ANSI MH16.1-2021
Revision of
ANSI MH16.1-2012(R2019)
Design, Testing, and Utilization
of Industrial Steel Storage Racks
An Industry Group of MHI
8720 Red Oak Blvd., Suite 201
Charlotte, NC 28217-3992
standards@mhi.org
© 2021 MHI
All rights reserved.
American National Standard
Approval of an American National Standard requires verification by the American National
Standards Institute (ANSI) that the requirements for due process, consensus, and other criteria
for approval have been met by the standards developer.
Consensus is established when, in the judgment of the ANSI Board of Standards Review,
substantial agreement has been reached by directly and materially affected interests.
Substantial agreement means much more than a simple majority, but not necessarily unanimity.
Consensus requires that all views and objections be considered, and that a concerted effort be
made toward their resolution.
The use of American National Standards is completely voluntary; their existence does not in any
respect preclude anyone, whether he has approved the standards or not, from manufacturing,
marketing, purchasing, or using products, processes or procedures not conforming to the
standards.
The American National Standards Institute does not develop standards and will in no
circumstances give an interpretation of any American National Standard. Moreover, no person
shall have the right or authority to issue an interpretation of an American National Standard in the
name of the American National Standards Institute. Requests for interpretations should be
addressed to the sponsor whose name appears on the title page of this standard.
CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time.
The procedures of the American National Standards Institute require that action be taken periodically
to reaffirm, revise or withdraw this standard. Purchasers of American National Standards may
receive current information on all standards by calling or writing the American National
Standards Institute.
Published by
Rack Manufacturers Institute
An Industry Group of MHI
8720 Red Oak Blvd., Suite 201, Charlotte, NC, 28217-3992
Telephone: (704) 676-1190 Fax: (704) 676-1199
standards@mhi.org
© 2021 by MHI
All rights reserved.
No part of this publication may be
reproduced in any form, in an electronic
retrieval system or otherwise, without
prior written permission of the publisher.
ANSI MH16.1-2021
Revision of
ANSI MH16.1-2012(R2019)
American National Standard
Design, Testing and Utilization of
Industrial Steel Storage Racks
Rack Manufacturers Institute
An Industry Group of MHI
Approved December 7, 2021
American National Standards Institute, Inc.
FOREWORD. This standard, which was developed under the American National Standards
Institute (ANSI) canvass method and approved by ANSI on December 7, 2021, represents
suggested design practices and operational requirements for industrial steel storage racks. It
was developed by MHI, along with the Rack Manufacturers Institute (“RMI”), one of its Industry
Groups, and is intended to provide useful information and guidance for owners, users,
designers, purchasers and/or specifiers of material handling equipment or systems. It is
advisory only and should only be regarded as a simple tool that its intended audience may or
may not choose to follow, adopt, modify, or reject. A standard may be part of but does not
constitute a comprehensive safety program that cannot guard against pitfalls in operating,
selecting, and purchasing industrial steel storage rack systems, and should not be relied upon
as such. Such a program should be developed by a registered design professional.
VOLUNTARY. The use of this document is completely voluntary. Its existence does not in any
respect preclude anyone, whether it has approved this standard or not, from following
procedures and assuming responsibilities not conforming to this standard.
DISCLAIMER OF LIABILITY. MHI, RMI and their members assume no responsibility and
disclaim all liability of any kind, however arising, as a result of acceptance or use or alleged use of
this standard. Anyone using this standard specifically understands and agrees that MHI, RMI,
their members, officers, agents, and employees shall not be liable under any legal theory of any
kind for any action or failure to act with respect to the design, erection, installation, manufacture,
and preparation for sale, sale, characteristics, features, or delivery of anything covered by this
standard or any other activity covered by this standard. Any use of this information must be
determined by the user to be in accordance with applicable federal, state, and local laws and
regulations.
DISCLAIMER OF WARRANTY. MHI, RMI and their members make no warranties of any kind,
express or implied, in connection with the information in this brochure and specifically disclaim
all implied warranties of merchantability and of fitness for particular purpose.
INDEMNIFICATION. By referring to or otherwise employing this standard, its user agrees to
defend, protect, indemnify, and hold MHI, RMI, their members, officers, agents, and employees
harmless from and against all claims, losses, expenses, damages, and liabilities, direct,
incidental, or consequential, arising from acceptance or use or alleged use of this standard,
including loss of profits and reasonable attorneys' fees which may arise out of the acceptance or
use or alleged use of this document. The intent of this provision is to absolve and protect MHI,
RMI, their members, officers, agents, and employees from loss relating in any way to this
document, including those resulting from the user's own negligence.
EXPRESSION OF PROVISIONS. This standard utilizes the expressions of provisions as defined in
ISO/IEC Directives, Part 2 – Principles and rules for the structure and drafting of ISO and IEC
documents, clause 7. The word “shall” expresses a requirement, or a mandatory provision to
comply with the standard. The word “should” expresses a recommendation or a good practice.
The word “may” expresses permission or something that is allowable. The word “can” expresses
a possibility or capability.
MHI. MHI is an Accredited Standards Developer. MHI provides RMI with administrative services
and, regarding this standard, arranges for its production and distribution. MHI and its officers,
directors, and employees have no other participation in the development and preparation of the
information contained in this standard.
RACK MANUFACTURERS INSTITUTE (“RMI”). RMI is an independent incorporated trade
association affiliated with MHI. The membership of RMI is made up of companies which
produce the preponderance of industrial steel storage racks and welded wire rack decking used
in the United States.
The RMI maintains the website www.mhi.org/rmi that has information about their products and
membership including ordering information for literature and a section on frequently asked
questions (FAQs).
At the date of approval of this standard, RMI consisted of the following member companies:

Advance Storage Products, Div. of J.C.M. Industries, Inc.

Atlanta Pallet Rack

Bulldog Rack Company

Cornerstone Specialty Wood Products, LLC

DACS, Inc.

Damotech, Inc.

Elite Storage Solutions, Inc.

Engineered Products

Equipement Boni, Inc.

Frazier Industrial

Hannibal Industries, Inc.

Heartland Steel Products

Husky Rack & Wire

Interlake Mecalux Inc.

ITC Manufacturing

J&L Wire Cloth, LLC

Jiangsu NOVA Intelligent Logistics Equipment Co., Ltd

Konstant

Mac Rak, Inc

Nanjing Kingmore Logistics Equipment Manufacturing Co., Ltd.

Nashville Wire Products, Inc.

Nedcon USA, LLC

Ohio Gratings, Inc.

Rack Builders, Inc.

RACKUSA / Tear Drop Rack

Ridg-U-Rak, Inc.

Speedrack Products Group, Ltd.

Steel King Industries, Inc.

Tri-Boro Rack & Storage Products

Twinlode Automation

Unarco Material Handling, Inc.

United Material Handling, Inc.
Questions or suggestions for improvement regarding of this standard are welcome. Suggestions
should be sent to: MH16.1 Committee, MHI, 8720 Red Oak Blvd., Suite 201, Charlotte, NC
28217; standards@mhi.org.
HISTORY OF THE STANDARD FOR INDUSTRIAL STEEL STORAGE RACKS
In the interest of improved uniformity of rack performance and enhanced public safety, the RMI
published in 1964 its first “Minimum Engineering Standards for Industrial Storage Racks”, and
now publishes this Specification. It was developed and promulgated by the RMI with the sole
intent of offering information to the parties engaged in the engineering, manufacturing,
marketing, purchasing, installation, inspection, permitting or use of such racks.
Since 1964, mechanized storage systems have grown very rapidly both in size and height with
new and modified types of racks having been developed. To reflect this rapid development and
to assure adequate safety and performance of modern rack structures, the RMI decided early in
1971 to replace its original standards by a more detailed and comprehensive specification.
Professors George Winter and Teoman Pekoz of Cornell University were retained to assist the
Rack Standard Development Project Committee in producing such a document. The members
of the Material Handling Institute, Inc. were the sponsors.
In 1972, the “Interim Specification for the Design, Testing and Utilization of Industrial Steel
Storage Racks” was adopted by the Rack Manufacturers Institute at their annual fall meeting.
The specification was then submitted to the American National Standards Institute for their
review and acceptance. In 1974, the Interim Specification with minor changes was accepted as
American National Standard ANSI MH16.1-1974.
RMI and MHI retained Professors Winter and Pekoz to continue testing rack components plus
perform full scale tests on typical storage rack structures. A number of the test results have
been analyzed, and it was considered necessary to rewrite the 1972 Interim Specification to
include the knowledge gained from the analysis of those tests. The 1972 Interim Specification
was rewritten by the Rack Standards Subcommittee with the assistance of Professors Winter
and Pekoz. Design parameters relating to drive-in and drive- through racks have been removed
from the Specification until drive-in and drive-through rack test results could be analyzed more
thoroughly; perhaps more testing would be required. Movable-shelf racks were added to the
Specification.
As a result of additional testing and analytical research, the RMI revised the 1972 Specification.
The ANSI MH16.1-1974 was withdrawn in deference to the 1979 Specification. More additions and
revisions prompted the RMI to publish the 1985 Specification.
Subsequent testing and research by Dr. Pekoz was the basis of the revisions resulting in the
1990 Specification.
From 1990 to 1997, due to continuing changes, specifically as they relate to seismic analysis
and other model building code issues, the Specification Advisory Committee, the Seismology
Committee and the RMI Engineering Committee working again with Dr. Pekoz and several
highly regarded members of the code community and various other members of similar groups
throughout the world, conducted extensive testing and parametric analysis. Findings resulted in
the 1997 Specification.
In addition to the benefit from the ongoing testing and analysis, the 1997 Specification was
expanded to include complete treatment of seismic design considerations so that the
Specification could be more easily incorporated by reference into various model building and
design codes.
In 1999, RMI created a voluntary certification program known as the R-Mark. The R-Mark is a
license earned by a manufacturer following a review by independent professional engineers of
tests and load capacity calculations performed by the manufacturer consistent with the
Specification.
Continued testing and parametric studies resulted in the 2002 Specification. In 2004 the 2002
RMI Specification and Commentary were adopted as American National Standard ANSI
MH16.1-2004.
ANSI MH16.1-2008 incorporated the results from FEMA 460. In addition, the symbol and
nomenclature tables were added. The seismic section was updated going from the old 𝐴𝑎 and
𝐴𝑣 values to the current 𝑆𝑆 and 𝑆1 values utilized by the USGS. A section on connection
rotational capacity was added. The column base plate section was updated. A section on shims
was added. A section on pick modules and rack supported platforms was added. The section on
automated and manual storage and retrieval systems was taken out of the appendix and
incorporated into the specification. A section for cyclic testing of beam-to- column connections
was added.
2021 Revision
ANSI MH16.1-2021 is a revision of ANSI MH16.1-2012(R2019). A summary of the major revisions
to this version include:

Reorganization of the document to align with guidance in ISO/IEC Directives, Part 2,
specifically moving requirements previously in Section 1 elsewhere in the document,
adding Normative References to Section 2 (previously Section 10, “References to the
Text”), and adding Terms and Definitions to Section 3 (previously “Nomenclature” in the
Foreword);

A requirement for post-installation inspection conducted by the owner has been added (see
4.3).

New stability design requirements similar to the requirements in ANSI/AISI S100 or
ANSI/AISC 360 replace the effective length method for stability design outlined in
previous editions (see 7.2);

Seismic provisions (7.4) were revised to align with ASCE/SEI 7-2016, including:
o
Revision of redundancy factors for multiple rows (see 7.4.3);
o
Revision of the 𝐹𝑎 and 𝐹𝑣 coefficients for the D-Default site class (see 7.4.4);

New design procedure for perforated columns that includes a new definition of net
section using reduced strips to represent the hole lines. Torsional properties are now to
be calculated using rounded corners and a distortional buckling check is required
for those sections subject to distortional buckling. The equation for 𝑄 effect on the
column strength has changed (see 8.2);

New section on pallet support design (see 9.5);

New section on frame tie and cross-aisle tie design (see 10.4).

New provisions for base plate and anchor design where the seismic overstrength
consideration is required (see 11.3).

Interpretation of the cyclic tests for connectors has been added (see 13.5);

The base fixity test (see 13.6) and frame bracing test (see 13.7) have been added;

The portal test and the upright frame test in the 2012 revision were removed from the 2021
revision.
The new provisions in Sections 8 and 13 are the result of the work of Dr. Pekoz, his international
colleagues, and the Specification Advisory Committee.
Comparison to ANSI MH16.1-2012(R2019)
ANSI MH16.1-2021 represents a substantial reformatting and updating of the previous
standard, ANSI MH16.1-2012(R2019). The following represents the Table of Contents for
MH16.1-2012(R2019) and the location of the corresponding guidance in ANSI MH16.1-2021.
Section Title
General
Scope
Materials
Applicable Design Specifications
Integrity of Rack Installations
Owner Maintenance
Plaque
Conformance
Load Application and Rack Configuration Drawings
Multiple Configurations
Movable-Shelf Rack Stability
Column Base Plates and Anchors
Small Installations
Rack Damage
Racks Connected to the Building Structure
Out-of-plumb and Out-of-straight Limits
Loading
Load Combinations For The ASD Design Method
Load Factors and Combinations for the LRFD Design Method
Vertical Impact Loads
Horizontal Forces
Wind Loads
Earthquake Loads
General
Minimum Seismic Forces
Calculation of Seismic Response Coefficient
Connection Rotational Capacity
Seismic Displacement
Seismic Separation
Vertical Distribution of Seismic Forces
Horizontal Shear Distribution
Overturning
Concurrent Forces
Design Procedures
Design of Steel Elements and Members
Cold-Formed Steel Members
Properties of Sections
R2019
1
1.1
1.2
1.3
1.4
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.4.9
1.4.10
1.4.11
2
2.1
2.2
2.3
2.4
2.5
2.6
2.6.1
2.6.2
2.6.3
2.6.4
2.6.5
2.6.6
2.6.7
2.6.8
2.6.9
2.6.10
3
4
4.1
4.1.1
2021
1
1.2
5
6
4
4.1
4.5
N/A
4.6
4.7
4.8
4.2
4.9
4.4
4.10
4.11
7
7.1.2
7.1.3
7.5
7.6
7.3
7.4
7.4.1
7.4.2.2
7.4.6
9.4.2
7.4.10
7.4.10
7.4.12
7.4.13
7.8
N/A
6
8
8.2
8.2.1
Section Title
Flexural Members
Concentrically Loaded Compression Members
R2019
4.1.2
4.1.3
Hot-Rolled Steel Columns
Beam Design
Calculations
Cross Section
Deflections
Beam-to-Column Connections
General
Beam Locking Device
Movable-Shelf Racks
Pallet Supports
Welded-Wire Rack Decking
Upright Frame Design
Definition
General
Upright frames and multi-tiered portal frames
Connections
Effective Lengths
Flexural Buckling in the Direction Perpendicular to the Upright
Frames
Flexural Buckling in the Plane of the Upright Frame
Torsional Buckling
Diagonals and Horizontals
Stability of Trussed-Braced Upright Frames
Column Base Design
Column Base Plates
Bearing on Concrete
Base Plate Design
Maximum Considered Earthquake Base Rotation
Shims
Slab and Subgrade evaluation
Anchor Bolts
Anchor Bolt Design
Periodic Inspection of Anchor Bolt Installation
Special Rack Design Provisions
Overturning
Connections to Buildings
Interaction with Buildings
Pick Modules and Rack Supported Platforms
Posting of Design Loads
Design Requirements
Rack Supported Platform and Pick Module Walkways
Section Title
4.2
5
5.1
5.2
5.3
5.4
5.4.1
5.4.2
5.4.3
5.5
5.6
6
6.1
6.2
6.2.1
6.2.2
6.3
6.3.1
2021
N/A
8.2.2,
8.2.3
N/A
9
9.1
9.2
9.3
9.4
9.4.1
9.4.3
9.4.4
9.5
9.6
10
N/A
N/A
10.1
N/A
10.2
10.2.1
6.3.2
6.3.3
6.3.4
6.4
7
7.1
7.1.1
7.1.2
7.1.3
7.1.4
7.2
7.3
7.3.1
7.3.2
8
8.1
8.2
8.3
8.4
8.4.1
8.4.2
8.4.3
R2019
10.2.2
10.2.3
10.3
N/A
11
11.1
11.1.1
11.1.2
11.1.3
11.2
11.4
11.3
11.3.1
11.3.3
12
12.1
12.2
12.2
12.3
12.3.2
12.3.3
12.3.4-6
2021
Stairways
Product Fall Protection
Automated Storage and Retrieval Systems (Stacker Racks)
Tolerances
Vertical Impact Loads
Horizontal Loads
Wind and Snow Loads
Deflections (5.3)
Rack Compatibility with the Equipment
Test Methods
General
Testing Apparatus and Fixtures
Instrumentation
Reduction and Presentation of Test Data
Evaluation of Tests for Determining Structural Performance
Stub Column Tests for Cold-Formed and Hot-Rolled Columns
Test Specimen and Procedure
Evaluation of Test Results
Pallet Beam Tests
Simply Supported Pallet Beam Tests
Pallet Beam in Upright Frames Assembly Test
Pallet Beam-to-Column Connection Tests
The Cantilever Test
The Portal Test
Upright Frame Test
Horizontal Load in the Direction Perpendicular to the Plane
of the Upright Frame
Horizontal Load in the Direction Parallel to the Plane of Upright
Frame
Cyclic Testing of Beam-to-Column Connections
8.4.4
8.4.5
8.5
8.5.1
8.5.2
8.5.3
8.5.4
8.5.5
8.5.6
9
9.1
9.1.1
9.1.2
9.1.3
9.1.4
9.2
9.2.1
9.2.2
9.3
9.3.1
9.3.2
9.4
9.4.1
9.4.2
9.5
12.3.5
12.3.8
12.4
12.4.2
12.4.3
12.4.4
12.4.5
12.4.6
12.4.7
13
13.1
13.1.3
13.1.4
13.1.5
N/A
13.2
13.2.2
13.2.3
13.3
13.3.2
13.3.3
13.4
13.4
N/A
N/A
9.5.1
N/A
9.5.2
N/A
9.6
13.5
In Memoriam
Daniel W. Clapp
1950 – 2020
The Rack Manufacturers Institute dedicates this standard to the memory of Dan Clapp. Dan
spent his entire working career, almost 50 years, at Frazier Industrial Company. He started
working at Frazier as an intern during his college years while attending the Milwaukee School of
Engineering before graduating from Lehigh University with a degree in Civil Engineering.
Dan demonstrated an uncommon passion to better understand the performance and fitness of steel
storage structures. He combined this with an unwavering commitment to developing consensus
industry and national standards, including this standard, CSA A344, CSA S16 Annex N (Design
and construction of steel storage racks), and FEMA 460.
Dan was instrumental in the evolution of the RMI Specification and worked tirelessly on its
development. He was Chair of the RMI Engineering Committee for nearly 30 years and oversaw
the RMI Specification Advisory Committee and the Seismology Subcommittee. Dan led the
efforts to update design method advances and to incorporate specific seismic design criteria
into the specification in 2002, led adoption of the specification as an American National
Standard in 2004, and led revisions in 2008 and 2012. Dan chaired the RMI Engineering
Committee and the CSA S16 Annex N Work Group up to his untimely passing, two days before
his seventieth birthday, and planned to retire after celebrating his 50th anniversary with Frazier.
His meaningful contributions to the industry cannot be overstated.
Design, Testing and Utilization of Industrial Steel Storage Racks
Table of Contents
Foreword..................................................................................................................................... iv
Comparison to ANSI MH16.1-2012(R2019)...............................................................................viii
In Memoriam............................................................................................................................... xi
Figures....................................................................................................................................... xv
Tables........................................................................................................................................ xv
Symbols..................................................................................................................................... xvi
1 Purpose and scope............................................................................................................... 1
Purpose......................................................................................................................... 1
Scope............................................................................................................................ 1
2 Normative references............................................................................................................ 2
3 Terms and definitions............................................................................................................ 3
4 Rack integrity, use, and maintenance.................................................................................12
Owner responsibilities..................................................................................................12
Column base plates and anchors.................................................................................12
Post-installation inspection...........................................................................................12
Repair or replacement of damaged storage rack systems or components...................12
Load plaque................................................................................................................. 12
Load application and rack configuration drawings........................................................13
Multiple configurations.................................................................................................13
Movable-shelf racks.....................................................................................................13
Small installations........................................................................................................13
Racks connected to the building structure...................................................................13
Out-of-plumb and out-of-straight limits.........................................................................13
Out-of–plumb limit.................................................................................................13
Out-of-straight limit...............................................................................................14
Modifications to industrial steel storage rack systems..................................................14
5 Materials............................................................................................................................. 15
6 Design procedures.............................................................................................................. 16
7 Loading............................................................................................................................... 17
Loading design methods..............................................................................................17
General................................................................................................................. 17
Load combinations for ASD method.....................................................................17
Load factors and combinations for LRFD method.................................................18
Design for stability........................................................................................................18
General................................................................................................................. 18
Product load..........................................................................................................18
Second order effects.............................................................................................19
Notional loads.......................................................................................................19
Connector sway rotational stiffness and moment strength....................................20
Column base stiffness and moment strength........................................................20
Movable-shelf rack stability...................................................................................20
Wind loads................................................................................................................... 21
Earthquake loads......................................................................................................... 21
General................................................................................................................. 21
Seismic design criteria..........................................................................................21
Redundancy factor................................................................................................22
Site coefficients and adjusted maximum considered earthquake spectral
response acceleration parameters
............................................................................................................................................
23
Determination of the seismic response coefficient................................................25
Site class definitions.............................................................................................26
Mapped acceleration parameters 𝑺𝑺 and 𝑺𝟏........................................................26
Seismic design category.......................................................................................26
Seismic displacement...........................................................................................27
Seismic separation...............................................................................................28
Vertical distribution of seismic forces....................................................................28
Horizontal distribution of seismic load at a storage level......................................29
Vertical impact loads...................................................................................................29
Horizontal loads........................................................................................................... 29
Storage racks for automated storage and retrieval systems........................................29
Seismic overturning.....................................................................................................30
8 Design of steel elements and members..............................................................................31
General........................................................................................................................ 31
Perforated steel members...........................................................................................31
Section properties of cold-formed steel sections..................................................31
Concentrically-loaded perforated compression members.....................................32
Perforated members bending about the centroidal axis perpendicular to the axis of
symmetry
.............................................................................................................................................
32
9 Beam design....................................................................................................................... 34
Calculations.................................................................................................................34
Cross-section.............................................................................................................. 34
Deflections...................................................................................................................34
Beam-to-column connections......................................................................................34
General................................................................................................................34
Connection rotational demand..............................................................................34
Beam locking device............................................................................................34
Movable-shelf racks.............................................................................................35
Pallet supports............................................................................................................. 35
Welded-wire rack decking............................................................................................35
10 Upright frame design..........................................................................................................36
Upright frames............................................................................................................. 36
Column design............................................................................................................ 36
Flexural buckling in the direction perpendicular to the upright frames..................36
Applicable column length for flexural buckling in the plane of the upright frame...36
Column length for torsional buckling.....................................................................37
Frame bracing design..................................................................................................37
Frame tie design..........................................................................................................37
General................................................................................................................37
Back-to-back ties (row spacers)...........................................................................37
Frame-to-column ties............................................................................................38
Flue shear ties......................................................................................................38
Cross-aisle ties.....................................................................................................38
11 Column base design...........................................................................................................39
Column base plates.....................................................................................................39
Bearing on concrete.............................................................................................39
Base plate design.................................................................................................39
Column base plate connection rotational demand................................................40
Shims.......................................................................................................................... 41
Anchorage...................................................................................................................41
Anchor bolt design................................................................................................41
Overstrength design for anchor bolts....................................................................41
Periodic inspection of anchor bolt installation.......................................................42
Slabs and subgrade evaluation...................................................................................42
12 Special rack design provisions............................................................................................43
General................................................................................................................43
Stabilization from anchor bolts and external bracing............................................43
Height-to-depth ratios...........................................................................................43
Loading by powered material handling equipment...............................................43
Interaction with buildings.............................................................................................43
Pick modules and rack supported platforms................................................................43
General................................................................................................................43
Design requirements............................................................................................44
Posting of design loads........................................................................................44
Safety flooring......................................................................................................44
Stairs, ladders, and guards...................................................................................44
Kick-plates (toeboards).........................................................................................45
Conveyor floor openings.......................................................................................45
Product fall protection...........................................................................................45
Storage racks for automated storage and retrieval systems........................................45
General................................................................................................................45
Tolerances............................................................................................................ 45
Vertical impact loads............................................................................................45
Horizontal loads....................................................................................................45
Wind, snow, and roof live loads............................................................................45
Deflections............................................................................................................ 45
Rack compatibility with the equipment..................................................................45
13 Testing................................................................................................................................ 46
Test methods............................................................................................................... 46
Testing and evaluation of test results...................................................................46
Material properties................................................................................................46
Testing apparatus and fixtures.............................................................................46
Instrumentation.....................................................................................................46
Test report............................................................................................................ 46
Stub column tests for cold-formed steel and hot-rolled steel columns.........................47
Purpose................................................................................................................47
Test specimen and procedure..............................................................................47
Evaluation of test results......................................................................................47
Pallet beam tests.........................................................................................................47
Purpose................................................................................................................47
Simply supported pallet beam tests......................................................................48
Pallet beam in upright frames assembly test........................................................48
The cantilever test.......................................................................................................49
Purpose................................................................................................................49
Test setup............................................................................................................49
Test procedure.....................................................................................................50
Evaluation of test results......................................................................................50
Cyclic testing of beam-to-column connections.............................................................50
Purpose................................................................................................................50
Test specimen......................................................................................................51
Test setup............................................................................................................52
Test procedure.....................................................................................................53
Evaluation of test results......................................................................................53
Column base fixity testing............................................................................................56
Purpose................................................................................................................56
Definitions............................................................................................................56
Precision..............................................................................................................56
Test specimen fixture and set-up..........................................................................57
Test procedure.....................................................................................................58
Evaluation of test results......................................................................................59
Purpose................................................................................................................59
Symbols............................................................................................................... 59
Precision..............................................................................................................59
Test specimen, fixture, and set-up........................................................................60
Test procedure.....................................................................................................61
Evaluation of test results......................................................................................61
Cyclical testing of upright frame bracing connection....................................................61
Purpose................................................................................................................61
Symbols............................................................................................................... 61
Precision..............................................................................................................62
Test specimen, fixture, and setup.........................................................................62
Test procedure.....................................................................................................63
Evaluation of test results......................................................................................64
Figures
Figure 8.2-1 – Example of perforation strips in a column...........................................................31
Figure 13.3-1 – Simply-supported pallet beam test setup..........................................................48
Figure 13.4-1 – The cantilever test setup...................................................................................50
Figure 13.5-1 – Beam-to-column cyclic test setup......................................................................52
Figure 13.6-1 – Column base fixity test setup............................................................................57
Figure 13.7-1 – Test set-up for joints with braces in tension or compression.............................60
Figure 13.8-1 – Test setup for joints with braces in tension or compression..............................62
Tables
Table 7.4-1 – Values of Site Coefficient 𝑭𝒂 as a Function of Site Class and Mapped Spectral
Response Acceleration at Short Periods (𝑺𝒔)
...................................................................................................................................................
24
Table 7.4-2 – Values of Site Coefficient 𝑭𝒗 as a Function of Site Class and Mapped Spectral
Response Acceleration at Short Periods (𝑺𝟏)
...................................................................................................................................................
24
Table 7.4-3 – Site Classification.................................................................................................26
Table 7.4-4 – Seismic Design Category Based on Short Period Response Acceleration Parameter
................................................................................................................................................... 27
Table 7.4-5 – Seismic Design Category Based on 1-Second Response Acceleration Parameter
................................................................................................................................................... 27
Table 13.5-1 – Beam-to-column testing load steps and cycles...................................................53
Table 13.5-2 – Drift angle limit performance levels....................................................................54
Table 13.8-1 – 𝑪 value and number of cycles for cyclical testing of frame bracing connection...64
Symbols
The section or table number in the right-hand column refers to where the symbol is first used or
defined.
SYMBOL
𝐴𝑏𝑟𝑔
𝐴𝑑
𝐴𝑛𝑒𝑡𝑔
𝐵2
DEFINITION
Effective base plate bearing area
Cross-sectional area of a diagonal brace
Area calculated for global buckling
Factor used to magnify first order moments to account for second
orders
effects when determining the required moment for combined
bending and axial force interaction
Deflection amplification factor
Seismic response modification coefficient
Dead load
Displacement
Modulus of elasticity of steel
Earthquake (seismic) load
Lateral force at the first storage level
Site coefficient defined in Table 7.4-1
Seismic base shear induced at level 𝑖
Maximum allowable bearing stress
Site coefficient defined in Table 7.4.2
Lateral force for any level
Story shear
Impact loading on a storage level
System importance factor for buildings and non-building structures
Base rotational stiffness
Effective length factor for torsional buckling
Effective length factor for story buckling in the down-aisle direction
Live load or any transportable load not considered as product load
Vertical distance from beam centerline to beam centerline
Distance between perforation center points
Portion of the live load used to compute the seismic mass 𝑊𝑠
Roof live load
Distance between beam perforations in web
Distance between beam perforations in flange
Storage live load
Distance between column brace points
𝐶𝑑
𝐶𝑠
𝐷
𝐷
𝐸
𝐸
𝐹1
𝐹𝑎
𝐹𝑖
𝐹′𝑝
𝐹𝑣
𝐹𝑥
𝐻
𝐼
𝐼𝑒
𝐾𝑏
𝐾𝑡
𝐾𝑥
𝐿
𝐿
𝐿
𝐿𝑎𝑝𝑝
𝐿𝑟
𝐿𝑛𝑝,𝑓
𝐿𝑛𝑝,𝑤
𝐿𝑠
𝐿𝑠ℎ𝑜𝑟𝑡
and
𝐿𝑙𝑜𝑛𝑔
𝐿𝑥, 𝐿𝑦, 𝐿𝑡 Unbraced lengths for column design, for bending about x- and yaxes and for torsion
𝑀
Base moment in the down-aisle direction
𝑀𝑏
Base moment
𝑀𝑏𝑎𝑠𝑒_𝑑 Column to base connection design strength
𝑀𝑐𝑜𝑛𝑛_𝑑 Connector moment design strength
𝑀𝑐𝑟𝑑
Elastic distortional buckling moment
Maximum moment from the cyclic connector test performed in
𝑀𝑚𝑎𝑥
accordance with the cyclic connector test procedure
𝑀𝑛
Nominal flexural strength (resistance)
Nominal flexural strength (resistance) for yielding and global buckling
𝑀𝑛𝑒
calculated according to ANSI/AISI S100 modified for the
presence of perforations
SECTION
11.1.1
10.4
8.2.2
7.2.3
7.4.10
7.4.2.2
7.1.1
13.5.4
13.5.5
7.1.1
7.4.12
7.4.4
7.4.13
11.1.1
7.4.4
7.4.12
7.2.3
7.1.1
7.4.2.2
11.1.3
7.2.4
7.2.4
7.1.1
7.2.3
8.2.1
7.1.1
7.1.1
8.2.1
8.2.1
7.4.2.2
10.2.2
7.2.4
11.1.2.4
11.1.3
7.2.6
7.2.5
8.2.3
7.2.5
8.2.3
8.2.3
𝑀𝑛𝑙𝑑
𝑀𝑛𝑙𝑔
𝑀𝑝
𝑀𝑦
𝑁
𝑁𝑖
𝑃
𝑃
𝑃𝛥
𝑃𝛿
Distortional and global buckling strength limit
Local and global buckling strength limit
Bending strength of the base plate
Yield moment
Effective length of the base plate in the down-aisle direction
Notional load applied at level 𝑖
Axial load in the column
Maximum load from pallets stored on the racks
Moments caused by story sway (global imperfections)
Added moments caused by member imperfections such as
curvature from the member chord
𝑃𝑎𝑝𝑝𝑆
Portion of the product load present for the seismic uplift being
evaluated
𝑃𝑎𝑝𝑝𝑊
Portion of the product load present for the uplift being evaluated
𝑃𝑎𝑣𝑒𝑟𝑎𝑔 Average weight of the load on any one beam
𝑒
𝑃𝑐𝑟𝑑
Distortional buckling load
𝑃𝑐𝑟𝑒
Least axial elastic global flexural or torsional-flexural buckling load
𝑃𝑚𝑎𝑥
Maximum weight of the load on any one column
𝑃𝑛
Nominal axial strength
𝑃𝑛𝑒
Least global buckling axial flexural or torsional-flexural buckling load
𝑃𝑛𝑙𝑑
Nominal distortional buckling load
𝑃𝑛𝑙𝑔
Nominal axial strength
𝑃𝑅𝐹
Product load reduction factor
Axial yield load
𝑃𝑦
𝑄
Capacity reduction factor for compressive members
𝑄𝑚𝑎𝑥,
Values obtained by test for the largest and smallest thickness
𝑄𝑚𝑖𝑛
𝑅
Load from rain including ponding
𝑅
Seismic response modification factor
Factor to account for 𝑃𝛿 effects as defined in ANSI/AISI
𝑅𝑚
S100 and ANSI/AISC 360
Component response modification factor
𝑅𝑝
Ratio of expected yield stress to specified minimum yield stress
𝑅𝑦
𝑆
Snow load
Design spectral response acceleration parameter for 1-second period
𝑆𝐷1
(2⁄3)𝑆𝑀1
𝑆𝐷𝑆
Design spectral response acceleration parameter for short period
(2⁄3)𝑆𝑀
𝑆𝑀1
Maximum considered earthquake spectral response
accelerations for 1- second period
Maximum considered earthquake spectral response
𝑆𝑀𝑆
accelerations for a 0.2-second (short) period
Mapped spectral accelerations for a 0.2 second (short) period as
𝑆𝑠
determined by the USGS
Mapped spectral accelerations for a 1-second period as
𝑆1
determined in accordance with the USGS
Fundamental period of the shelving structure in each direction under
𝑇
consideration
𝑇𝑎𝑛𝑐ℎ
Required strength for anchorage, including overstrength
𝑇𝑏
Values defined in ANSI/AISC 360 or ANSIAISI S100
𝑈𝑛
Net uplift
𝑉
Seismic base shear
𝑉𝑥
Seismic base shear at any level
𝑊
Wind load
Seismic weight
𝑊𝑝
8.2.3
8.2.3
11.3.2
8.2.3
11.1.2.4
7.2.4
7.2.3
7.1.1
7.2.3
7.2.3
7.1.1
7.1.1
7.4.2.2
8.2.2
8.2.2
7.2.2
8.2.2
8.2.2
8.2.2
8.2.2
7.4.2.2
8.2.2
8.2.2
13.2.3
7.1.1
7.4.6
7.2.3
7.4.2.3
11.1.2.3
7.1.1
7.4.6
7.1.1
7.4.4
7.4.4
7.4.4
7.4.6
C7.4.4
11.3.2
7.2.4
11.3.2
7.4.2.2
7.4.13
7.1.2
7.4.2.3
𝑊𝑠
Loads on the structure that are used to compute the horizontal base
shear
𝑌𝑖
Gravity load applied at level 𝑖 from the LRFD or ASD load combination
Plastic section modulus of the base plate assuming an effective
𝑍𝑝
width of the plate halfway between the column and the anchor bolts
𝑒
Base plate axial load eccentricity
𝑓′𝑐
Minimum 28-day compression strength of the concrete floor
ℎ𝑖 or ℎ𝑥 Height from the base to level 𝑖 or 𝑥
ℎ𝑡𝑜𝑡𝑎𝑙
Height of the top storage level
ℎ𝑏,𝑡𝑜𝑝
Height from the floor slab to the top storage beam level
ℎ𝑡,𝑡𝑜𝑝
Height from the floor slab to the top back-to-back tie
Global and local buckling coefficient
𝑘𝑔
𝑡
Wall thickness of steel column
𝑡𝑑,𝑤 and Thicknesses of the strips containing web and flange perforations
𝑡𝑑,𝑓
𝑡𝑚𝑎𝑥 ,
Maximum and minimum column thickness
𝑡𝑚𝑖𝑛
𝑡𝑛𝑝
Plate thickness required to eliminate prying action
𝑣𝑠̅
Soil shear wave velocity
𝑤𝑖 or 𝑤𝑥 Portion of the total gravity load of a rack located or assigned to the
bottom storage level, level 𝑖 or 𝑥
𝛼
Second-order load amplification factor used in the column check
First iteration of the second-order amplification term calculated using a
𝛼𝑠
properly substantiated analysis
𝛽
Seismic product load coefficient
𝜌
Redundancy factor for earthquake loading
𝜙
Resistance factor for converting maximum moment into design
moment
𝜙
Angle between horizontal and diagonal braces
𝜃𝑏
Rotational capacity
𝜃𝐷
Rotational seismic demand of the beam-to-column connection
𝛿𝑥𝑒,𝑠
Elastic displacement of the steel storage rack resulting from the
seismic load
Inelastic displacement of the steel storage rack resulting from the
𝛿𝑥,𝑠
seismic load
Minimum separation distance between the rack structure and the
𝛿𝑀𝑇
building structure
𝛿𝑥,𝑏
Maximum seismic inelastic displacement of the building structure
Slenderness factor for least axial elastic global flexural or torsional𝜆𝑐
flexural buckling load
𝜆𝑑
Slenderness factor of distortional buckling
7.4.2.2
7.2.4
11.3.2
11.1.2.4
11.1.1
7.4.12
9.4.2
10.4.2
10.4.2
8.2.1
8.2.1
8.2.1
13.2.3
11.1.2.3
7.4.7
7.4.12
7.2.4
7.4.9
7.1.1
7.1.1
7.2.5
10.4
11.1.3
9.4.2
7.4.10
7.4.10
7.4.11
7.4.11
8.2.2
8.2.2
AMERICAN NATIONAL STANDARD
ANSI MH16.1-2021
1 Purpose and Scope
1.1 Purpose
The purpose of this standard is to specify minimum requirements for the structural design, testing,
and utilization of industrial steel storage racks.
1.2 Scope
This specification (hereinafter referred to as the standard) and companion commentary applies to
industrial steel storage racks, movable-shelf racks, rack-supported systems, and automated
storage and retrieval systems (sometimes referred to as “stacker racks”) constructed of coldformed and/or hot-rolled steel structural members. Such rack types also include push-back rack,
pallet-flow rack, case-flow rack, pick modules, and rack-supported platforms. This standard is also
intended to be applied to the design of the storage rack portion of any rack structure that provides
support to the exterior walls and roof, except as noted. It does not apply to other types of racks,
such as drive-in or drive-through racks, cantilever racks, portable racks, or to racks made of
material other than steel.
Specification for the Design, Testing, and Utilization of Industrial Steel Storage Racks
ANSI MH16.1-2021
2 Normative references
The following standards contain provisions which, through reference in this text, constitute
provisions of this American National Standard. At the time of publication, the editions indicated
were valid. All standards are subject to revision, and parties to agreements based on this
American National Standard are encouraged to investigate the possibility of applying the most
recent editions (including errata and supplements) of the standards indicated below.
ANSI/AISI S100-16(2020) with S2-20, North American Specification for the Design of ColdFormed Steel Structural Members, 2016 version (reaffirmed 2020) with Supplement 2, 2020
edition
AISI S902-17, Test Standard for Determining the Effective Area of Cold-Formed Steel
Compression Members
ANSI/AISC 360-16, Specification for Structural Steel Buildings
ANSI/AISC 341-16, Seismic Provisions for Structural Steel Buildings
ANSI MH26.2-2017, Design, Testing and Utilization of Welded-Wire Rack Decking
ANSI MH32.1-2018, Stairs, Ladders, and Open-Edge Guards for Use with Material Handling
Structures International Building Code, 2021 Edition, International Code Council (ICC)
ASCE/SEI 7-16, Minimum Design Loads for Buildings and Other Structures with Supplement 1
published December 13, 2018
ANSI/ASSE Z359.2-2017, Minimum Requirements for a Comprehensive Managed Fall Protection
Program
ACI 318-19, Building Code Requirements for Structural Concrete
ANSI/AWS D1.1/D1.1M-2020, Structural Welding Code – Steel
ANSI/AWS D1.3/D1.3M-2018, Structural Welding Code – Sheet
Steel
ASTM A370-20, Standard Test Methods and Definitions for Mechanical Testing of Steel Products
ASTM F3125 / F3125M - 19e2, Standard Specification for High Strength Structural Bolts and
Assemblies, Steel and Alloy Steel, Heat Treated, Inch Dimensions 120 ksi and 150 ksi Minimum
Tensile Strength, and Metric Dimensions 830 MPa and 1040 MPa Minimum Tensile Strength
ASTM E4-20, Standard Practices for Force Verification of Testing Machines
3 Terms and definitions
Unless otherwise expressly stated, the following words and terms shall, for the purposes of this
standard, have the meanings shown. Where terms are not specifically defined, such terms shall
have the commonly accepted meanings as the context implies or as stated within the referenced
documents.
NOTE - Terms designated with † are common with AISI and AISC terms that are coordinated
between the standards developers.
3.1
anchor
anchor bolt
a fastener typically used for securing an industrial steel storage rack to the floor
3.2
allowable strength design (ASD) †
method of proportioning structural components such that the allowable strength equals or
exceeds the required strength of the component under the action of the ASD load combinations
3.3
applicable building code†
code (enforced by the AHJ) under which the structure is designed
3.4
Authority Having Jurisdiction (AHJ)
an organization, office, or individual granted legal authority for enforcing the requirements of a
code or standard, or for approving equipment, materials, an installation, or a procedure
3.5
automated storage and retrieval system (ASRS)
a rack structure in which loading and unloading of the racks is accomplished by a stacker crane,
or similar vehicle, without the aid of an on-board operator
3.6
Automated storage and retrieval system (ASRS)
load carrying members designed to stabilize two rows of frames
3.7
beam
typically, a horizontal structural member that has the primary function of resisting bending moments
3.8
Beam locking device
a pin, bolt, or other mechanism that resists disengagement of the beam connector from the column
3.9
Braced frame†
an essentially vertical truss system that provides resistance to lateral forces and provides stability
for the structural system
3.10
Buckling
limit state of sudden change in the geometry of a structure or any of its elements under a critical
loading condition
3.11
Cantilever rack
a rack structure comprised primarily of vertical columns, extended bases, horizontal arms
projecting from the face of the columns, and down-aisle bracing between columns
NOTE – Storage level beams can be installed between arms depending on the product
being stored. Cantilever columns can be free-standing or overhead tied.
3.12
Cantilever test
a test designed and conducted to determine the connection moment-resisting capacity and the
rotational rigidity, 𝐹, of a beam-to-column connection
NOTE – The test set-up employs one column segment and one beam segment connected to one
another with a beam-to-column connector, with a load applied downwardly in the plane of the
frame at the cantilever end of the beam segment.
3.13
Case-flow rack
a specialized pallet rack structure in which either the horizontal storage level beams support caseflow lanes or case-flow storage level assemblies are supported by the upright frames
NOTE – The case-flow lanes or shelves are installed at a slight pitch permitting multiple-depth
case or box storage with loading from one service aisle and unloading or picking from another
service aisle.
3.14
Cladding
exterior covering of a structure
3.15
Cold-formed steel structural member†
shape manufactured by press-braking blanks sheared from sheets, cut lengths of coils or plates,
or by roll forming cold- or hot-rolled coils or sheets; both forming operations being performed at
ambient room temperature; i.e. without manifest addition of heat, such as would be required for
hot forming
3.16
Column
structural member that has the primary function of resisting axial force
3.17
Concurrent forces
two or more forces acting in conjunction with one another at a single location
3.18
Connection †
combination of structural elements and joints used to transmit forces between two or more members
3.19
Cross-aisle
Transverse direction
one of the two principal directions of the storage rack, corresponding to the direction
perpendicular to the principal handling equipment aisle
NOTE – See “down-aisle” definition for the other principal direction.
3.20
Cross-aisle ties
load-carrying members designed to stabilize two rows of frames separated by an aisle
3.21
Cyclic test
a test designed and conducted to determine a beam-to-column connection’s rotational capacity
and rotational stiffness under standardized cyclic loading conditions
NOTE 1 – The purpose of a cyclic test is to quantify the energy-dissipation properties of
the connection. NOTE 2 – See 13.5.
3.22
Design load †
applied load determined in accordance with either LRFD load combinations or ASD load
combinations, whichever is applicable
3.23
design strength †
resistance factor multiplied by the nominal strength (𝜃𝑅𝑛)
3.24
Diagonal bracing
inclined structural member carrying primarily axial force in a braced frame
3.25
Distortional buckling
a mode of buckling involving change in cross-sectional shape, excluding local buckling
3.26
double-stacking
the act of loading a storage level with loads stacked one on top of another in a pallet position
3.27
down-aisle
longitudinal direction
one of the two principal directions of the storage rack, corresponding to the direction of the principal
handling equipment aisle
NOTE – See “cross-aisle” definition for the other principal direction.
3.28
drive-in rack
a rack structure comprised primarily of vertical upright frames, horizontal support arms, and
horizontal load rails typically used for one-wide by multiple-depth storage
NOTE – This structure includes an “anchor section” with horizontal beams supporting the
load rails. Loading and unloading within a bay is done from the same aisle. A two-way
drive-in rack is a special case where back- to-back rows of drive-in racks are combined
into a single entity with a common rear post.
3.29
drive-through rack
a rack structure comprised primarily of vertical upright frames, horizontal support arms, and
horizontal load rails typically used for one-wide by multiple-depth storage
NOTE – This structure lacks the “anchor section” found in drive-in racks; therefore,
loading and unloading can be accomplished from both ends of a bay.
3.30
effective length
length of an otherwise identical column with the same strength when analyzed with pinned-end
conditions
3.31
effective length factor
ratio between the effective length and the unbraced length of the member
3.32
factored load†
product of a load factor and the nominal load
3.33
flexural buckling
buckling mode in which a compression member deflects laterally without twist or change in crosssectional shape
3.34
flexural-torsional buckling†
buckling mode in which a compression member bends and twists simultaneously without
change in cross- sectional shape
3.35
frame-to-column ties
load-carrying members designed to brace a single column to an upright frame and transfer lateral
forces from the single column to the frame line
3.36
flue shear ties
ties that are used to connect frames in tandem
3.37
guardrails
members installed on an elevated rack-supported platform or pick module walkway whose
purpose is to provide fall protection for the occupants of the structure
NOTE – Guardrails consist of a top rail, an intermediate rail(s), and posts.
3.38
gravity load
load such as that produced by product, dead and live loads, acting in the downward direction
3.39
Handrail
smooth, continuous railing that runs up a stairway assembly to provide added balance and safety
for the occupants as they walk up or down the stairway assembly
3.40
kick-plate
toeboard
a vertical plate (angle or barrier) that is installed at the edge of an elevated floor that is intended to
prevent loose items from sliding off the edge of the floor
3.41
load factor
factor that accounts for deviations of the nominal load from the actual load, for uncertainties in
the analysis that transforms the load into a load effect, and for the probability that more than one
extreme load will occur simultaneously
3.42
Load and Resistance Factor Design (LRFD)†
method of proportioning structural components such that the design strength equals or exceeds
the required strength of the component under the action of the LRFD load combinations
3.43
local buckling
limit state of buckling of a compression element within a cross-section
3.44
LRFD load combination†
load combination in the applicable building code intended for strength design
3.45
movable-shelf rack
a rack structure comprised primarily of vertical upright frames and horizontal storage level
beams and typically used for one-deep pallet or hand-stack storage, where the locations of
some of the storage levels are typically “fixed” with the location of the in-fill shelves being
flexible
3.46
nominal strength†
strength of a structure or component (without the resistance factor or safety factor applied) to
resist load effects, as determined in accordance with this standard
3.47
out-of-plumb ratio
maximum horizontal distance (inches or millimeters) from the centerline of the column at the floor to
a plumb line that extends downward from the centerline of the column at the top storage level
elevation divided by the vertical distance (feet or meters) from the floor to the top storage level
elevation
3.48
out-of-straight ratio
maximum horizontal distance (inches or millimeters) from the centerline at any point on the
column to a plumb line from any other point on the column divided by the vertical distance (feet
or meters) between the two points
3.49
overturning moment
an applied force multiplied by the height at which it is applied that causes a structure to turn over
3.50
pallet beam
the front and back storage level members that bear the weight of the load and transfer the load
to the upright frames
3.51
pallet-flow rack
a specialized pallet rack structure in which the horizontal storage level beams support palletflow lanes, where pallet-flow lanes are typically installed on a slight pitch permitting multipledepth pallet storage with loading from one service aisle and unloading from another service
aisle
3.52
pallet rack
storage rack
a rack structure comprised primarily of vertical upright frames and horizontal storage level
beams and typically used for one- and two-deep pallet storage
3.53
pallet support
a member that extends between the storage level beams at a given level underneath the stored
load that aids in the support of that load
3.54
pick module
a rack structure comprised primarily of vertical frames and horizontal beams, typically having
one or more elevated platform levels of selective, case-flow, or pallet-flow bays feeding into a
central pick aisle(s) [work platform(s)] supported by the rack structure
3.55
plan and back bracing
a bracing system including bracing parallel to the main aisle of the rack located at the back of
the rack row and horizontal bracing from the aisle column to the rear braced points
3.56
Plaque
signage depicting the permissible loading of the rack
3.57
portable rack
stacking frames
stacking rack
an assembly, typically with four corner columns, that permits stacking of one assembly on top of
another without applying any additional load to the product being stored on each assembly
3.58
product load
the weight of the item(s) placed on the rack
3.59
push-back rack
a specialized pallet rack structure in which the horizontal storage level beams support pushback lanes comprised of tracks and carts
NOTE – The push-back lanes are installed on a slight pitch permitting multiple-depth
pallet storage. Loading and unloading are done from the same service aisle by pushing
the pallets back. Push-back lanes can alternatively use pallet flow lanes in lieu of the
push-back lanes comprised of tracks and carts.
3.60
rack-supported platform
a decked working surface supported by the rack structure
3.61
rack-supported system
a rack structure with wall girts and roof purlins or equivalent components used to support wall
and roof cladding, designed to withstand wind, snow or rain, or roof live loads in addition to the
normal storage rack loads
3.62
registered design professional
an engineer registered or licensed to practice professional engineering as defined by the
statutory requirements of the professional registration laws of the jurisdiction in which the project
is to be constructed
3.63
resistance factor†
factor that accounts for unavoidable deviations of the nominal strength from the actual strength
and for the manner and consequences of failure
3.64
risk category
a categorization of buildings and other structures for determination of flood, snow, ice, and
earthquake loads based on the risk associated with unacceptable performance
3.65
safety factor†
factor that accounts factor that accounts for deviations of the actual strength from the nominal
strength, deviations of the actual load from the nominal load, uncertainties in the analysis that
transforms the load into a load effect, and for the manner and consequences of failure
NOTE – The nominal load divided by the safety factor results in the allowable load for an
Allowable Strength Design (ASD).
3.66
safety flooring
a surface that is provided in areas where order picking personnel might need to step off the
normal walking area or pick module walkway to dislodge loads that have not properly flowed to
their correct position
3.67
seismic design category
a classification assigned to a structure based on its risk category and the severity of the design
earthquake ground motion at the site
3.68
Sidesway
buckling mode where there is translation of the top of the column with respect to the bottom of
the column
NOTE – This mode is also referred to as story buckling and is a buckling mode for the
unbraced direction of a pallet rack row.
3.69
site class
a classification assigned to a location based on the types of soils present and their engineering
properties
3.70
site class
condition reached in the loading of a structural component, frame, or structure in which a slight
disturbance in the loads or geometry does not produce large displacements
3.71
stacker rack
storage racks associated with automated storage and retrieval systems
3.72
Stiffness
resistance to deformation of a member or structure, measured by the ratio of the applied force
(or moment) to the corresponding displacement (or rotation)
3.73
structural system
an assemblage of load-carrying components joined to provide interaction or interdependence
3.74
stub-column test
concentric compression testing of short column members to determine the column’s 𝑄 factor
3.75
torsional buckling
buckling mode in which a compression member twists about its shear center axis
3.76
torsional-flexural buckling
buckling mode in which compression members bend and twist simultaneously without change in
cross sectional shape
3.77
trussed-braced upright frame
upright frames having two columns similar to the chords of a truss and diagonal and horizontal
bracing attached to and located between the columns
NOTE – The diagonals and horizontals become the web members of the truss. (It is
referred to as a vertical truss.)
3.78
unbraced length
distance between braced points of a member, measured between the centers of gravity of the
bracing members
3.79
unit-load
the total weight expected to be placed in a single storage position in the rack consisting of the
product load and pallet weight
3.80
upright frame
frame
structural assembly that transfers the vertical and horizontal loads to the floor, usually made up
of two columns, bracing members between the columns, and base plates on the bottom of the
columns, where beams of the rack are attached to the columns of the frames and transfer the
loads to the columns
3.81
vertical impact load
additional downward force added to the beams produced during loading of the rack
3.82
welded-wire rack deck
a decking system used on pallet rack shelves, fabricated from welded-wire mesh and
reinforcements in the form of channels or support wires, intended to provide additional support
for stored material and acting as a safety net for unstable loads
3.83
yield point†
first stress in a material at which an increase in strain occurs without an increase in stress, as
defined by ASTM
3.84
yield strength†
stress at which a material exhibits a specified limiting deviation from the proportionality of stress
to strain, as defined by ASTM
4 Rack integrity, use, and maintenance
4.1 Owner responsibilities
Owners shall maintain the structural integrity of the installed storage rack system by assuring
proper operational, housekeeping, and maintenance procedures including, but not limited to, the
following:
a) Prohibit any overloading of any pallet positions and of the overall rack system.
b) Require all pallets to be maintained in good, safe, operating condition.
c) Ensure that pallets are properly placed onto pallet load support members in a properly
stacked and stable position.
d) Require that all goods stored on each pallet be properly stacked and stable.
e) Prohibit double-stacking of any pallet position, including the top-most position, unless
the rack system is specifically designed for such loading.
f)
Ensure that the racks are not modified or rearranged in a manner not within the
original design configurations described in 4.6, or as might invalidate the plaque
information as described in 4.5.
4.2 Column base plates and anchors
The bottom of all columns shall be furnished with column base plates, as specified in 11.1. All
rack columns shall be anchored to the floor with anchor bolts, as specified in 11.3, to resist all
applicable forces described in 7.1.
For hand-loaded storage rack systems whose top shelf is 8 ft (2.4 m) or less from the floor area,
the anchorage requirement shall be permitted to be waived, if approved by a registered design
professional.
4.3 Post-installation inspection
Owners of industrial steel storage racks shall inspect the rack system after installation to ensure
that the rack system was installed in accordance with the load application and rack configuration
drawings (see 4.6) and other requirements set forth in this standard.
4.4 Repair or replacement of damaged storage rack systems or components
Owners of industrial steel storage racks shall implement inspection, maintenance, and reporting
procedures to identify any visible damage or other conditions that could affect the load capacity
or structural performance of the industrial storage rack system. Upon identification of such
conditions, the owner shall immediately isolate the affected portions of the industrial storage
rack system and initiate a mitigative response, such as repair or replacement of the affected
portions of the rack system. Before allowing the storage rack system to be placed back into
service, a registered design professional shall certify that the storage rack system and/or the
repaired components have been restored to at least their original design capacity.
Rack damage inspection, assessment, and repair is beyond the scope of this standard. Refer to
the commentary for a broader discussion on this topic.
4.5 Load plaque
Industrial steel storage rack systems designed and installed in accordance with this standard
shall be identified with one or more load plaques, displayed on or near the rack system. Each
load plaque shall have an area of not less than 50 in2 (320 cm2). Load plaques shall include
the following information:
a)
the maximum permissible unit load and/or maximum uniformly distributed load per level;
b) the average unit load (𝑃𝐴𝑣𝑒𝑟𝑎𝑔𝑒 , see 7.4.2.2) if applicable;
c)
total actual loading expected in the interconnected bays (see 7.2.2); and
d) the maximum total load per bay.
Storage levels allowing multiple stacking of unit loads shall be identified.
Information on load plaques shall represent the permissible load capacity of the rack systems as
designed. If rack systems are modified in a way that invalidates the plaque information, the load
plaques shall be updated with new information (see 4.12).
4.6 Load application and rack configuration drawings
Load application and rack configuration (LARC) drawings shall be furnished with each rack
installation. The LARC drawings shall be retained by the owner for the entire life of the storage
rack system for future reference.
The owner shall ensure that the LARC drawings represent the rack systems as originally
designed. The owner shall also ensure that the rack system is not modified in a manner that
invalidates the LARC drawing information and have the LARC drawings updated when
modifications are made (see 4.12).
4.7 Multiple configurations
If a storage rack system is designed for more than one storage level configuration or profile, the
LARC drawings shall include either or both of the following:
a)
all the permissible configurations; or
b) limitations as to the maximum number of storage levels, the maximum distance
between storage levels and the maximum distance from the floor to the bottom storage
level.
4.8 Movable-shelf racks
The stability of movable-shelf racks shall not depend on the presence, absence, or location of
the movable shelves. Components that provide stability, such as permanently fastened top
shelves and longitudinal and transverse diagonal bracing, shall be clearly indicated on the
LARC drawings (see 4.6). For specific movable-shelf rack installations in which the overall rack
height is a controlling element, a conspicuous warning shall be included in the owner’s
utilization instruction manual stating any restrictions to shelf placement or shelf removal. Such
restrictions shall be permanently posted in locations clearly visible to forklift operators.
4.9 Small installations
The requirements in 4.5 and 4.6 shall be permitted to be waived for small installations that meet
all of the following criteria:
a)
the top storage level is less than 12 ft (3.7 m) in height from the floor;
b) the industrial storage rack system covers a floor area less than 3,000 ft2 (280 m2), not
including aisles; and
c)
multiple stacking on the top storage level is not permitted.
NOTE – See 7.4.1 for additional requirements on earthquake loads for storage racks
greater than 8 ft (2.4 m) in height.
4.10 Racks connected to the building structure
If storage racks are connected to the building structure, then the location and magnitude of the
maximum possible horizontal and vertical forces (see 7.1.2 and 7.1.3), that are imposed by the
storage rack to the building, shall be provided by the registered design professional to the
owner.
The design shall account for loads, if any, imposed by the building onto the storage rack system.
NOTE – See 12.2 for guidance regarding connections between storage racks and
portions of buildings other than floors.
4.11 Out-of-plumb and out-of-straight limits
4.11.1 Out-of–plumb limit
All loaded storage rack columns shall be within a top-to-bottom out-of-plumb ratio of 1/240 (0.05
in. per 1 ft or 0.5 in. per 10 ft [12 mm per 3 m] of height). Columns whose out-of-plumb ratio
exceed this limit shall be unloaded and plumbed within permissible limits. Any damaged parts
shall be repaired or replaced.
4.11.2 Out-of-straight limit
All loaded storage rack columns shall be within an out-of-straight ratio of 1/240 (0.05 in. per 1 ft
or 0.5 in. per 10 ft [12 mm per 3 m] of height). Columns whose out-of-straight ratio exceed this
limit shall be unloaded and plumbed within permissible limits. Any damaged parts shall be
repaired or replaced.
4.12 Modifications to industrial steel storage rack systems
Modifications to industrial steel storage rack systems that could affect the load capacity or other
performance requirements shall meet the following requirements:
a) the modifications shall be reviewed and approved by a registered design professional;
b) the registered design professional shall affirm that the modified rack system meets the
requirements of this standard;
c) the modifications and any changes to the load capacities shall be reflected on the load plaques
(see 4.5) and LARC drawings (see 4.6), if applicable (see 4.9);
d) the modified part(s) of the rack system shall be evaluated for out-of-plumb and out-of-straight
limits (see 4.11).
5 Materials
Storage racks shall be constructed of steel of structural quality as defined by the ASTM
standards listed in ANSI/AISI S100 and ANSI/AISC 360.
Fasteners shall conform to ASTM F3125, SAE J429 or other equivalent approved by the AHJ.
Steels not listed in ANSI/AISI S100 or ANSI/AISC 360 shall not be excluded provided both of the
following criteria are met:
a) they conform to the chemical and mechanical requirements of either reference ANSI/AISI S100
and ANSI/AISC 360, or other published specifications, which establish their properties and
structural suitability; and
b) they are subjected either by the producer or the purchaser to analyses, tests, and other controls
in the manner prescribed by either ANSI/AISI S100 and ANSI/AISC 360, as applicable.
6 Design procedures
All computations for safe loads, stresses, and deflections shall be made in accordance with
conventional methods of structural design, as specified in ANSI/AISI S100 for cold-formed steel
components and structural systems and ANSI/AISC 360 for hot-rolled steel components and
structural systems, except as modified or supplemented by this specification. In cases where
adequate methods of design calculations are not available, designs shall be based on test
results obtained in accordance with this standard or ANSI/AISI S100 Section K.
Slenderness limitations shall not be imposed on tension members that are not required to resist
compression forces under the various load combinations specified in 7.1.2 and 7.1.3.
7 Loading
7.1 Loading design methods
7.1.1.
General
Industrial steel storage rack structures shall be designed using the provisions for Allowable
Strength Design (ASD) or the provisions for Load and Resistance Factor Design (LRFD). The
members and connections shall be designed for the most critical load combination.
For both ASD (7.1.2) and LRFD (7.1.3), the following definitions shall apply:
𝐷
is the dead load;
𝐿
is the live load, or any transportable load not considered as
product load; (Examples: loading from rack supported platforms)
𝐿𝑎𝑝𝑝
is the portion of the live load used to compute the seismic mass 𝑊𝑠;
𝐿𝑟
is the roof live load as determined in accordance with ASCE/SEI 7;
𝑆
is the snow load as determined in accordance with ASCE/SEI 7;
𝑅
is the rain load as determined in accordance with ASCE/SEI 7;
𝑊
is the wind load as determined in accordance with ASCE/SEI 7;
𝐸
is the earthquake load;
𝐼
is the impact loading on a storage level;
𝑃
is the maximum load from product stored on the racks;
𝑃𝑎𝑝𝑝𝑆
is the portion of product load for seismic uplift that is present for the seismic
uplift being evaluated (see 0);
𝑃𝑎𝑝𝑝𝑊
for wind uplift, is the portion of product load that is used to compute the wind base
shear;
𝑆𝐷𝑆
is the design spectral response acceleration parameter for short period;
𝜌
is the redundancy factor for earthquake loading as specified in 7.4.3;
𝛽
is the seismic product load coefficient where 𝛽 = 0.7, except for uplift combinations
where
𝛽 = 1.0.
For uplift due to wind, only pallet loads that must be present to develop the lateral wind loads
shall be considered in 𝑃𝑎𝑝𝑝𝑊. For an unloaded rack that supports exterior cladding, 𝑃𝑎𝑝𝑝𝑊
shall be taken as zero
7.1.2 Load combinations for ASD method
When the ASD method is used, all load factors and combinations shall be in accordance with
ASCE/SEI 7, as modified in this section for industrial steel storage racks:
3.
𝐷 + 𝑃 + 𝐿
𝐷 + 𝑃 + (𝐿𝑟 𝑜𝑟 𝑆 𝑜𝑟 𝑅)
Critical limit state
dead load
gravity (product/live)
load
roof live/snow/rain load
4.
𝐷 + 0.75(𝑃 + 𝐿 + (𝐿𝑟 𝑜𝑟 𝑆 𝑜𝑟 𝑅))
gravity + roof live/
snow/rain load
1.
2.
𝐷 + 𝑃
5. (1 +
0.105𝑆𝐷𝑆
6.
7.
(𝐿𝑟
)𝛽𝑃 + 𝐿 +
)𝐷 + 0.75[(1.4 +
(𝐿𝑟
0.14𝑆𝐷𝑆
(1 + 0.14𝑆𝐷𝑆)𝐷 + (0.85 + 0.14𝑆𝐷𝑆)𝛽𝑃 + 0.7𝜌𝐸
𝐷 + 0.75(𝑃 + 𝐿 +
𝑜𝑟 𝑆 𝑜𝑟 𝑅) + 0.6𝑊)
gravity + other loads +
𝑜𝑟 𝑆 𝑜𝑟 𝑅) + 0.7𝜌𝐸] seismi
c
gravity + seismic
gravity + other
loads + wind
8. 0.6𝐷 + 0.6𝑃𝑎𝑝𝑝𝑊 + 0.6𝑊
9. 𝐷 + 0.85𝑃 + 0.6𝑊
10. (0.6 − 0.14𝑆𝐷𝑆)𝐷 + (0.6– 0.14𝑆𝐷𝑆)𝛽𝑃𝑎𝑝𝑝𝑆 + 𝐿𝑎𝑝𝑝 + 0.7𝜌𝐸
wind uplift
gravity + wind
seismic uplift
For load support beams and their connections only:
11. 𝐷 + 𝐿 + 0.5(𝑆 𝑜𝑟 𝑅) + 0.88𝑃 + 𝐼
shelf +impact
All safety factors shall be as stated in ANSI/AISI S100 or ANSI/AISC 360.
7.1.3 Load factors and combinations for LRFD method
When the LRFD method is used, all load factors and combinations shall be as stated in
ASCE/SEI 7, except as modified in this section for industrial steel storage racks:
1.
2.
3.
4.
5.
6.
7.
1.4𝐷 + 1.2𝑃
1.2𝐷 + 1.4𝑃 + 1.6𝐿 + 0.5(𝐿𝑟𝑜𝑟 𝑆 𝑜𝑟 𝑅)
1.2𝐷 + 0.85𝑃 + (0.5𝐿 𝑜𝑟 0.5𝑊) + 1.6(𝐿𝑟 𝑜𝑟 𝑆 𝑜𝑟 𝑅)
1.2𝐷 + 0.85𝑃 + 0.5𝐿 + 1.0𝑊 + 0.5(𝐿𝑟 𝑜𝑟 𝑆 𝑜𝑟 𝑅)
(1.2 + 0.2𝑆𝐷𝑆)𝐷 + (1.2 + 0.2𝑆𝐷𝑆)𝛽𝑃 + 0.5𝐿 + 𝜌𝐸 + 0.2𝑆
0.9𝐷 + 0.9𝑃𝑎𝑝𝑝𝑊 + 1.0𝑊
(0.9– 0.2𝑆𝐷𝑆)𝐷 + (0.9 − 0.2𝑆𝐷𝑆)𝛽𝑃𝑎𝑝𝑝𝑆 + 𝐿𝑎𝑝𝑝 + 𝜌𝐸
Critical limit state
dead load
gravity (product/live) load
roof live/snow/rain load
wind load
seismic load
wind uplift
seismic uplift
For load support beams and their connections only:
8. 1.2𝐷 + 1.6𝐿 + 0.5(𝑆 𝑜𝑟 𝑅) + 1.4𝑃 + 1.4𝐼
product/live/impact
NOTE – For load case #6 (wind uplift), only the pallet loads present to develop the
lateral wind loads are considered in 𝑃𝑎𝑝𝑝𝑊. 𝑃𝑎𝑝𝑝𝑊 is zero for an unloaded rack that
supports exterior cladding.
All resistance factors shall be as stated in ANSI/AISI S100 or ANSI/AISC 360.
7.2 Design for stability
7.2.1 General
Except as modified or supplemented in this standard, racks using cold-formed steel columns
shall be designed for stability, as specified by ANSI/AISI S100. Racks using structural steel
columns shall be designed for stability, as specified by ANSI/AISC 360. All load-dependent
effects shall be calculated at a level of loading corresponding to 𝛼 times the ASD load
combinations (where 𝛼 is defined in 7.2.3 or LRFD load combinations.
Semi-rigid rotational stiffness of all connections shall be included in the analysis. Stiffness
reduction multipliers found in ANSI/AISI S100 and ANSI/AISC 360 shall be applied for all
members and connections. Loads used for the stability analysis shall be the loads from the load
combination being considered. Use of average product load shall be as permitted in 7.2.2. All
member checks shall be made using either ANSI/AISI S100 or ANSI/AISC 360, except as
modified by this standard. The connector moments and the base moments shall not exceed
their design strength values calculated in 7.2.5 and 7.2.6, respectively.
7.2.2 Product load
The product load 𝑃𝑚𝑎𝑥 shall be the maximum weight permissible to be stored in that location.
The average product load 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 shall be permitted to be used for system stability if either of
the following conditions are met:
a)
For unbraced systems where stability is developed by moment frame action of the
columns, beams, and beam-to-column connectors and three or more bays are
connected.
b) For braced systems where the stability is developed by diagonal bracing and the use of
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 , in accordance with this standard, three or more sets of bracing are
interconnected to provide stability.
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 shall be taken as the total actual loading expected in the interconnected bays. When
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is used for system effects, the average load shall be specified as a part of the
contract documents by the rack owner and appear on both the load plaques and the LARC
drawings and calculations.
For the notional load analysis, the stated average load (𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 ) used shall not be less than
67% of the maximum load (𝑃𝑚𝑎𝑥 ).
The maximum product load 𝑃𝑚𝑎𝑥 shall be used for checking the compression on an individual
column and for computing the 𝑃𝛿 effect. See 7.2.3 for more information on the 𝑃𝛿 effect.
7.2.3 Second order effects
In addition to the primary forces and moments from the horizontal forces, analysis shall include
both 𝑃𝛥
and 𝑃𝛿:

𝑃𝛥 effects are moments caused by story sway (global imperfections);

𝑃𝛿 effects are added moments caused by member imperfections, such as curvature
from the member chord.
These effects shall be considered by using a computer analysis that includes these effects or by
multiplying the primary moments by 𝐵2:
1
𝐵2 =
≥1
(7.2-1)
𝛼𝑃𝛥
1−
𝑅𝑚𝐻𝐿
where:
𝐵2
is the factor used to magnify first order moments to account for second orders
effects when determining the required moment for combined bending and axial
force interaction;
𝛼
is the second-order load amplification factor used in the column check
(1.0
for LRFD or 1.4 + 0.2 for ASD);
𝐿
𝑃+𝐿
𝑃
is the column axial load based on 𝑃𝑚𝑎𝑥 or the column load based on
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 where permitted;
𝛥
is the primary story deflection or drift;
𝐻
is the story shear;
𝐿
is the vertical distance from the floor to the centerline of the first beam level, or
the vertical distance from beam centerline to beam centerline;
𝑅𝑚
360.
is the factor to account for 𝑃𝛿 effects as defined in ANSI/AISI S100 and ANSI/AISC
An 𝑅𝑚 value of 1.0 shall be permitted if 𝑃𝛿 moments are calculated and 𝐵2 is increased to
account for added 𝑃𝛿 moments.
If 𝐵2 ≥ 1.7, initial imperfections shall be included in the analysis for load combinations with
applied lateral loads. If 𝐵2 < 1.7, the analysis shall be permitted to include initial imperfections
only in the analysis for gravity-only load combinations
7.2.4 Notional loads
Notional loads shall be permitted to be used to represent the effects of initial system
imperfections rather than directly modelling these imperfections in accordance with AISI S100
and AISC 360, as applicable. These notional loads shall be applied at the points of intersection
of the beam and the column members. The notional load shall be applied to a model of the rack
system based on its nominal geometry. The properties of the punched column for the stability
analysis shall be the same as the properties used for the global buckling check (see 8.2).
Notional loads shall be applied as lateral loads at all levels simultaneously and shall be applied
in the direction that results in the greatest destabilizing effect. The notional loads shall be
applied in all load combinations. The magnitude of the notional loads shall be:
𝑁𝑖 = 0.004𝛼𝑌𝑖, if τ𝑏 is considered in the stiffness reduction;
(7.2-2)
𝑁𝑖 = 0.005𝛼𝑌𝑖, if τ𝑏 is not considered in the stiffness reduction.
(7.2-3)
where:
𝑁𝑖
is the notional load applied at storage level 𝑖;
𝛼
is defined in 7.2.3;
𝑌𝑖
is the gravity load applied at storage level 𝑖 from the LRFD or ASD load combination;
τ𝑏
are values defined in ANSI/AISC 360 or ANSI/AISI S100.
For rack structures that comply with the minimum bay requirements specified in 7.2.2, and
where there is a stated average storage level load that is less than the maximum load, the
stated average load shall be permitted to be used for 𝑌𝑖, since this value represents the story
load. For the notional load analysis, the stated average load used shall not be less than 67% of
the maximum load.
If an out-of-plumb or out-of-straight limit other than the limit in accordance with 4.11 is specified
on the LARC drawing, the notional load coefficient shall be permitted to be adjusted
proportionally. In no case shall the notional load used be less than 0.002.
When the method of analysis described herein is used, the effective length factor 𝐾𝑥 shall equal
1.0. 𝐿𝑥, 𝐿𝑦,
𝐿𝑡, 𝐾𝑦, and 𝐾𝑡 values shall be in accordance with Section 10.
7.2.5 Connector sway rotational stiffness and moment strength
The connector design moment strength to be used for the down-aisle frame analysis shall be taken
as:
𝑀𝑐𝑜𝑛𝑛_𝑑 = 𝜙𝑀𝑚𝑎𝑥
where
:
(7.2-4)
𝑀𝑐𝑜𝑛𝑛_𝑑 is the connector moment design strength;
𝜙
is the resistance factor for converting maximum moment into design moment (0.75);
𝑀𝑚𝑎𝑥 is the maximum moment from the cyclic connector test performed in accordance
with the cyclic connector test.
The connector rotational stiffness (𝐾𝑐𝑜𝑛𝑛) to be used for the down-aisle frame analysis shall be
taken as the slope of a line drawn from the origin of the connector 𝑀 vs. 𝜃 graph to the point on
the curve that corresponds to 0.8𝑀𝑐𝑜𝑛𝑛_𝑑.
Alternatively, a higher value of stiffness shall be permitted to be used based on rational analysis
provided that the final connector moment from the second order analysis does not exceed the
moment capacity corresponding to the point where stiffness is determined on the connector 𝑀
vs. 𝜃 curve.
7.2.6 Column base stiffness and moment strength
The column base design moment strength to be used for the down-aisle frame analysis shall be
taken as:
𝑀𝑏𝑎𝑠𝑒_𝑑 = 𝜙𝑀𝑚𝑎𝑥
(7.2-5)
where:
𝑀𝑏𝑎𝑠𝑒_𝑑 is the column to base connection design strength;
𝜙
is the resistance factor for converting maximum moment into design moment (0.75);
𝑀𝑚𝑎𝑥 is the maximum moment from the column base fixity test (see 13.6) to be used for
the down-aisle frame analysis and shall be taken as the slope of a line drawn
from the origin of the base connection 𝑀 vs. 𝜃 graph to the point on the curve
that corresponds to 0.8𝑀𝑏𝑎𝑠𝑒_𝑑.
Alternatively, a different value of stiffness shall be permitted to be used based on rational
analysis provided that the final base moment from the second order analysis does not exceed
the moment capacity of the base connection corresponding to the design stiffness.
7.2.7 Movable-shelf rack stability
The stability of movable-rack shelf racks shall not depend on the presence, absence, or location
of the movable shelves.
7.3 Wind loads
Wind loads shall be determined in accordance with ASCE/SEI 7.
Racks directly exposed to the wind shall be designed for the wind loads acting both on the rack
structure and the loaded pallets. For stability, consideration shall be given to loading conditions
which produce large wind loads combined with small stabilizing gravity forces.
Horizontal loads (see 7.6) caused by out-of-plumb installation shall be assumed to act
concurrently with any wind loads. Loads from seismic (see 7.4) or automated storage and
retrieving systems (ASRS) (see 7.7) shall not be required to act concurrently with wind loads.
7.4 Earthquake loads
7.4.1 General
Earthquake loads shall be determined in accordance with ASCE/SEI 7 as modified in this section.
Earthquake effects and associated lateral forces shall be incorporated into industrial storage
rack design when required by applicable building codes. For each such installation, the storage
rack shall be designed, manufactured, and installed in accordance with such provisions.
Industrial steel storage racks greater than 8 ft (2.4 m) in height to the top loaded storage level
and are subject to earthquake ground motions, shall be designed and constructed to resist
earthquake loads in compliance with this section.
7.4.2 Seismic design criteria
7.4.2.1 General
The storage rack shall be designed for the total minimum lateral seismic force in accordance
with one of the following methods:
a)
the methods specified in this section (7.4.2);
b) a Modal Response Spectrum Analysis (MRSA) conducted in accordance with ASCE/SEI 7;
c)
an approved seismic design evaluation performed using a displacement-based method.
7.4.2.2 Seismic base shear for racks installed at or below grade elevation
Storage racks installed at or below grade elevation shall be designed, fabricated, and installed
in accordance with the requirements of this section.
The seismic design forces shall not be less than that required by the following equation for the
determination of seismic base shear:
𝑉 = 𝐶𝑠 𝐼𝑒𝑊𝑠
(7.4-1)
Where:
𝑉
is the seismic response coefficient determined in 7.4.6;
𝐼𝑒
is the system importance factor, determined as follows:
𝑊𝑠
a)
𝐼𝑒 = 1.5 if the system contains material that would be
significantly hazardous if released;
b)
𝐼𝑒 = 1.5 if the system is open to the public, e.g., in a warehouse-style
retail store;
c)
𝐼𝑒 = 1.5 if the system is an essential facility;
d)
𝐼𝑒 = 1.0 for all other structures.
is the load on the structure that is used to compute the horizontal base
shear, computed as:
𝑊𝑠 = 𝐷 + (0.67𝑃𝑅𝐹𝑃) + 0.25𝐿𝑠
where:
𝐿𝑠
is the live load for areas used as storage;
𝑃𝑅𝐹
is the product load reduction factor, determined as follows:
a) Down-aisle direction: 𝑃𝑅𝐹 = 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 /𝑃𝑚𝑎𝑥𝑖𝑚𝑢𝑚
b) Cross-aisle direction: 𝑃𝑅𝐹 = 1
where:
(7.4-2)
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒
a)
is equal to:
𝑃𝑚𝑎𝑥𝑖𝑚𝑢𝑚 for warehouse retail stores open to the general
public; or
b) the maximum total weight of product expected on all the beam
levels in any row divided by the number of beam levels in
that row.
𝑃𝑚𝑎𝑥𝑖𝑚𝑢𝑚 is the maximum allowable weight of the product that is
placed on any one beam level in that row.
NOTE – The 0.67 coefficient associated with 𝑃𝑅𝐹 𝑃 is an indication of how much the
mass of the product would participate in the mode of vibration and should be applied any
time the equivalent force is computed. This coefficient is separate from the 67% value
calculated for seismic overturning (see 0), which pertains to loading combinations for the
evaluation of the floor and potential for pulling out the base anchors. When applicable,
both 0.67 values would apply
7.4.2.3 Above grade elevation
Storage racks installed at elevations above grade shall meet the force and displacement
requirements of the applicable building code for nonbuilding structures supported by other
structures, including the force and displacement effects caused by amplifications of upper-story
motions. The horizontal seismic design force (𝐹𝑃) shall be applied at the storage rack system’s
center of gravity and distributed relative to the storage rack system’s mass distribution in
accordance with ASCE/SEI 7, Section 13.3.1. The following terms shall be used to calculate 𝐹𝑃
for racks installed above grade elevation:
a)
𝐼𝑝 = 𝐼𝑒 , where 𝐼𝑝 is the system importance factor applied in the nonstructural component
force equations in ASCE/SEI 7, Section 13.3;
b) 𝑅𝑃 = 𝑅, where 𝑅𝑃 is the component response modification factor of the storage rack
when the storage rack is installed above grade elevation;
c)
𝑎𝑃 = 2.5, where 𝑎𝑃 is the component amplification factor of the storage rack when the
storage rack is installed above grade elevation;
d) 𝑊𝑝, the seismic weight; shall be calculated using the following equation:
𝑊𝑝 = 𝐷 + (0.67𝑃𝑅𝐹 𝑃) + 0.25𝐿𝑠
(7.4-3)
7.4.3 Redundancy factor
7.4.3.1 General
The redundancy factor in each horizontal direction shall be determined in accordance with
ASCE/SEI 7, Section 12.3.4, as modified in this section.
7.4.3.2 Seismic Design Categories A, B, and C
The redundancy factor shall be permitted to be 𝜌 = 1.0 for storage racks installed in facilities
that are assigned to Seismic Design Categories A, B, or C.
7.4.3.3 Seismic Design Categories D, E, and F
7.4.3.3.1 Moment frames
For storage racks with moment frames installed in locations that are assigned to Seismic Design
Categories D, E, or F, the redundancy factor shall vary depending on whether the moment
frames are interconnected in a manner where the frame connectors or cross-aisle ties are
designed to transfer the base shear from one frame to another through axial forces, shear
forces, and bending moments.
The redundancy factor for each line of resistance composed of moment frame structural
systems shall be permitted to be taken as follows:
a)
𝜌 = 1.3 when there is only one independent bay in the down-aisle direction or one
independent frame in the cross-aisle direction, and the conditions specified in
subparagraphs b) and c) are not present;
b) 𝜌 = 1.15 when there are two interconnected bays in the down-aisle direction or two
interconnected frames in the cross-aisle direction that are of equal strength and
stiffness; or
c)
𝜌 = 1.0 when there are three or more bays in the down-aisle direction or three
interconnected frames in the cross-aisle direction that are of equal strength and
stiffness.
7.4.3.3.2 Braced frames
For storage racks with braced frames installed in locations that are assigned to Seismic Design
Categories D, E, or F, the redundancy factor shall vary depending on whether the braced
frames are interconnected in a manner where the frame connectors or cross-aisle ties are
designed to transfer the base shear from one frame to another in both tension and compression.
The redundancy factor for each line of resistance composed of brace frame structural systems
shall be permitted to be assigned as follows:
a)
𝜌 = 1.3 when there is only one independent braced frame with only a single diagonal
brace or two connected braced frames with diagonal braces in the same direction, and
the conditions specified in subparagraphs b) and c) are not present;
b) 𝜌 = 1.15 when either of the following conditions are met:
1) there is only one braced frame per connected frame line that has X-braced
diagonals, and each diagonal and its connections is designed to equally resist
the design seismic forces in tension and compression in accordance with 10.3;
2) there are two braced frames of equal strength and stiffness with opposing
diagonals per connected frame line that are adequately tied back-to-back in
accordance with 10.4, and the braces and their connections in each braced
frame are designed to equally resist the design seismic forces acting in each
direction;
c)
𝜌 = 1.0 when either of the following conditions are met:
1) there are two braced frames of equal strength and stiffness per connected frame
line that have X-braced diagonal braces, and each diagonal and its connections
is designed to equally resist the design seismic forces in tension and
compression in accordance with 10.3;
2) there are three or more seismic force-resisting systems of equal strength and
stiffness that are tied back-to-back in accordance with 10.4, and the braces and
their connections in each braced frame are designed to equally resist the design
seismic forces in each direction.
7.4.4 Site coefficients and adjusted maximum considered earthquake spectral response acceleration
parameters
Site coefficients and adjusted maximum considered earthquake spectral response acceleration
parameters shall be determined in accordance with ASCE/SEI 7 Section 11.4.4 as modified in
this section.
The maximum considered earthquake spectral response acceleration for short periods, 𝑆𝑀𝑆 , and
at 1-second periods, 𝑆𝑀1, adjusted for site class effects, shall be determined from the following
equations:
𝑆𝑀𝑆 = 𝐹𝑎𝑆𝑠
(7.4-4)
𝑆𝑀1 = 𝐹𝑣𝑆1
(7.4-5)
where:
𝐹𝑎
is the site coefficient defined in Table 7.4-1;
𝐹𝑣
is the site coefficient defined in Table 7.4-2;
𝑆𝑠
is the mapped spectral accelerations for 0.2 second (short) period, as described in
7.4.8;
𝑆1
is the mapped spectral accelerations for a 1-second period, as described in 7.4.8.
Table 7.4-1 – Values of Site Coefficient 𝑭𝒂 as a Function of Site Class and Mapped
Spectral Response Acceleration at Short Periods (𝑺𝒔)
SITE
CLASS
A
B
C
D
D-default
E
F
MAPPED SPECTRAL RESPONSE ACCELERATION AT SHORT PERIODS
𝑺𝒔 ≤ 0.25
𝑺𝒔 = 0.50
𝑺𝒔 = 0.75
𝑺𝒔 = 1.00
𝑺𝒔= 1.25
𝑺𝒔 ≥ 1.5
0.8
0.8
0.8
0.8
0.8
0.8
0.9
0.9
0.9
0.9
0.9
0.9
1.3
1.3
1.2
1.2
1.2
1.2
1.6
1.4
1.2
1.1
1.0
1.0
1.6
1.4
1.2
1.2
1.2
1.2
2.4
1.7
1.3
NOTE 4
NOTE 4
NOTE 4
NOTE 3
NOTE 3
NOTE 3
NOTE 3
NOTE 3
NOTE 3
NOTE 1 – Refer to Table 7.4-3 for site class definitions.
NOTE 2 – Use straight-line interpolation for intermediate values of mapped spectral
response acceleration at short period, 𝑆𝑠.
NOTE 3 – a site response analysis shall be conducted as specified by ASCE/SEI 7,
Section 21.1, unless exempted in accordance with ASCE/SEI 7, Section 20.3.1.
NOTE 4 – A ground motion hazard analysis (GMHA) including site effects shall be
conducted as specified by ASCE/SEI 7, Section 21.2, except when the site coefficient 𝐹𝑎 is
taken as equal to that of Site Class C.
Table 7.4-2 – Values of Site Coefficient 𝑭𝒗 as a Function of Site Class and Mapped
Spectral Response Acceleration at Short Periods (𝑺𝟏)
SITE
CLASS
A
B
C
D
Ddef
aul
t
E
F
MAPPED SPECTRAL RESPONSE ACCELERATION AT SHORT PERIODS
𝑺𝟏 < 0.1
𝑺𝟏 = 0.2
𝑺𝟏 = 0.3
𝑺𝟏 = 0.4
𝑺𝟏 = 0.5
𝑺𝟏 ≥ 0.6
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
1.5
1.5
1.5
1.5
1.5
1.4
2.4
NOTE 4
NOTE 4
NOTE 4
NOTE 4
NOTE 4
2.4
3.3 (NOTE 5)
3.0
2.85
2.7
2.55
4.2
NOTE
3
NOTE 4
NOTE 3
NOTE 4
NOTE 3
NOTE 4
NOTE 3
NOTE 4
NOTE 3
NOTE 4
NOTE 3
NOTE 1 – Refer to Table 7.4-3 for site class definitions.
NOTE 2 – Use straight-line interpolation for intermediate values of mapped spectral
response acceleration at 1-second period, 𝑆1.
NOTE 3 – A site response analysis shall be conducted as specified by ASCE/SEI 7,
Section 21.1, unless exempted in accordance with ASCE/SEI 7, Section 20.3.1.
NOTE 4 – A GMHA including site effects shall be conducted as specified by
ASCE/SEI 7, Section 21.2. NOTE 5 – For 𝑆1 values greater than 0.1 and less than
0.2, interpolate between 2.4 and 2.2.
7.5 Design spectral response acceleration parameters
Five-percent damped design spectral response accelerations at short periods, 𝑆𝐷𝑆, and at a 1second period, 𝑆𝐷1, shall be determined from the following equations in accordance with
ASCE/SEI 7, Section 11.4.5:
where:
𝑆𝑀𝑆
𝑆𝐷𝑆 = (2/3)𝑆𝑀𝑆
(7.4-6)
𝑆𝐷1 = (2/3)𝑆𝑀1
(7.4-7)
is the maximum considered earthquake spectral response accelerations for
short period as determined in 7.4.4;
𝑆𝑀1
is the maximum considered earthquake spectral response accelerations for
1-second period as determined in 7.4.4.
7.4.6 Determination of the seismic response coefficient
The seismic response coefficient in each horizontal direction shall be determined in accordance
with ASCE/SEI 7, Section 12.8.1.1, as modified in this section:
The seismic response coefficient, 𝐶𝑠, shall be determined in accordance with the following
equation:
𝑆
𝐶𝑠 = 𝐷𝑆
𝑅
where:
(7.4-8)
𝐶𝑠
is the seismic response coefficient;
𝑆𝐷𝑆
is the design earthquake spectral response acceleration at a short period as
described in 7.4.4;
𝑅
is the response modification factor: 𝑅 = 4.0 in the braced direction and 𝑅 =
6.0 in the moment frame direction.
When the fundamental period of the rack structure is computed, the value of 𝐶𝑠 determined in
accordance with the equation above need not exceed the following:
𝐶𝑠 shall not be less than:
𝐶𝑠 𝑆𝐷1
=
𝑇𝑅
𝐶𝑠 = 0.044𝑆𝐷𝑆 ≥ 0.01
(7.4-9)
(7.4-10)
In addition, for structures located where 𝑆1 ≥ 0.6𝑔, 𝐶𝑠 shall not be less than:
𝐶𝑠 0.5𝑆1
=
𝑅
where:
𝑆𝐷1
is the design earthquake spectral response acceleration at a 1-second period, as
described in 7.4.4;
𝑇
is the fundamental period of the rack structure in each direction under
consideration established using the structural properties and deformation
characteristics of the resisting elements in a properly substantiated analysis. For
the moment frame direction, the period shall be determined using a connection
stiffness, 𝐹, not less than the value from 13.5;
𝑆1
is the mapped spectral acceleration for a 1-second period, as described in 7.4.8.
𝑆𝑀𝑆 = 𝐹𝑎𝑆𝑠
(7.4-12)
𝑆𝑀1 = 𝐹𝑣𝑆1
7.4.7Site class definitions
(7.4-13)
The site class shall be defined in accordance with the site classifications defined in ASCE/SEI
7, Section 20.3, as specified in this section.
Based on the site soil properties, the site shall be classified as Site Class A, B, C, D, E, or F in
accordance with Table 7.4-3. Where the soil properties are not known in sufficient detail to
determine the site class, Site Class D-default shall be used unless the Authority Having
Jurisdiction (AHJ) or geotechnical data determine that Site Class E or F soils are present at the
site.
Table 7.4-3 – Site Classification
SITE
CLASS
A
B
C
SOIL PROFILE NAME
Hard rock
Rock
D
Very dense soil and soft
rock
Stiff soil
E
Soft clay soil
F
Soils
requiring
site
response analysis in
accordance
with
ASCE/SEI 7, Section
21.1
AVERAGE PROPERTIES IN TOP 100 ft
Standard penetration
Soil shear wave
Soil undrained shear
resistance, 𝑵̅
velocity, 𝒗̅𝒔 , (ft/s)
strength, 𝒔̅𝒖 , (psf)
(blows/ft)
𝑣𝑠̅ > 5,000
N/A
N/A
2,500 < 𝑣𝑠̅ ≤
N/A
N/A
5,000
1,200 < 𝑣𝑠̅ ≤
𝑁̅ > 50
𝑠𝑢̅ ≥ 2,000
2,500
600 < 𝑣𝑠̅ ≤ 1,200
15 ≤ 𝑁̅ ≤ 50
1,000 ≤ 𝑁̅ ≤ 2,000
𝑣𝑠̅ < 600
𝑁̅ < 15
𝑠𝑢̅ < 1,000
Any profile with more than 10 feet of soil having the following characteristics:
1.
Plasticity index 𝑃𝐼 > 20,
2.
Moisture content 𝑤 ≥ 40%,
3.
Undrained shear strength 𝑠𝑢̅ < 500 psf
Any profile containing soils having one or more of the following
characteristics:
1.
Soils vulnerable to potential failure or collapse under seismic
loading such as liquefiable soils, quick and highly sensitive clays,
collapsible weakly cemented soils.
2.
Peats and/or highly organic clays (𝐻 > 10 feet of peat
and/or highly organic clay where 𝐻 = thickness of soil)
3.
Very high plasticity clays (𝐻 > 25 feet with plasticity index 𝑃𝐼 >
75) in a soil profile that would otherwise be classified as Site
Class D or E.
4.
Very thick, soft/medium clays (𝐻 > 120 feet) with 𝑠𝑢̅ < 1,000 psf.
NOTE 1 – For SI: 1 ft = 0.304 m; 1 ft/s = 0.304 m/s; 1 psf = 0.048 kPa.
NOTE 2 – N/A = Not applicable.
NOTE 3 – Table source: ASCE/SEI 7, Table 20.3-1.
7.4.8 Mapped acceleration parameters 𝑺𝑺 and 𝑺𝟏
The mapped acceleration parameters shall be determined in accordance with ASCE/SEI 7,
Section 11.4.2. The parameters 𝑆𝑠 and 𝑆1 shall be as specified in ASCE/SEI 7, Chapter 22.
NOTE 1 – A software program providing mapped values in accordance with ASCE/SEI
7, Chapter 22, is accessible at https://asce7hazardtool.online/ or https://seismicmaps.org
to determine the values based on the street address or latitude and longitude of the site.
NOTE 2 – For jurisdictions that require that structural design meet the 2021 International
Building Code (IBC), seismic design ground motion values for a specific site location and
site soil conditions determined in accordance with Chapter 16 of the 2021 IBC are
provided at https://asce7hazardtool.online/ or https://seismicmaps.org. To be an
acceptable source of design values associated with the 2021 IBC, seismic design value
websites are required to utilize the electronic values of mapped acceleration parameters
provided
by
the
U.S.
Geological
Survey
(USGS)
website
https://doi.org/10.5066/F7NK3C76. The user is cautioned to verify that the website being
used utilizes this USGS website to obtain its 2021 IBC seismic design ground motion
values.
7.4.9 Seismic design category
The seismic design category shall be determined in accordance with ASCE/SEI 7, Section 11.6,
as indicated in this section.
Structures shall be assigned a seismic design category based upon the controlling 𝑆𝐷𝑆 or 𝑆𝐷1
value as calculated in 7.4.4. See Table 7.4-4 and Table 7.4-5, respectively.
Table 7.4-4 – Seismic Design Category Based on Short Period Response Acceleration
Parameter
Value of 𝑺𝑫𝐒
𝑆𝐷S < 0.167
0.167 ≤ 𝑆𝐷S < 0.33
0.33 ≤ 𝑆𝐷S < 0.50
0.50 ≤ 𝑆𝐷S
Risk Category
I or II or III
IV
A
A
B
C
C
D
D
D
Table 7.4-5 – Seismic Design Category Based on 1-Second Response Acceleration
Parameter
Value of 𝑺𝑫𝟏
𝑆𝐷1 < 0.067
0.067 ≤ 𝑆𝐷1 < 0.133
0.133 ≤ 𝑆𝐷1 < 0.20
0.20 ≤ 𝑆𝐷1
Risk Category
I or II or III
IV
A
A
B
C
C
D
D
D
Structures classified as Risk Category I, II or III that are located where the mapped spectral
response acceleration parameter at 1-second period, 𝑆1 ≥ 0.75 shall be assigned to Seismic
Design Category E.
Structures classified as Risk Category IV that are located where the mapped spectral response
acceleration parameter at 1-second period, 𝑆1 ≥ 0.75 shall be assigned to Seismic Design
Category F.
All other structures shall be assigned to a seismic design category based on their Risk Category
and the design spectral response acceleration coefficients, 𝑆𝐷𝑆 and 𝑆𝐷1 determined in
accordance with 7.4.4.
7.4.10 Seismic displacement
The seismic displacement shall be determined in accordance with ASCE/SEI 7, Section
12.12.3, as modified in this section.
The elastic displacement of the storage rack resulting from the seismic load, 𝛿𝑥𝑒,𝑠., shall be
determined using the same structural system stiffness as used to determine the period for the
base shear calculation (see C7.4.4) and using the base shear from 7.4.2, including the 𝐼𝑝 factor.
The elastic displacement 𝛿𝑥𝑒,𝑠 shall be calculated by elastic analysis using LRFD-level seismic
forces determined using the strength load combinations provided in 7.1.3 (or 1.43 times ASDlevel forces determined using load combinations provided in 7.1.2).
The inelastic seismic displacement 𝛿𝑥,𝑠 shall be determined using the following equation:
𝛿𝑥,𝑠 = (𝐶𝑑𝛿𝑥𝑒,𝑠)/𝐼𝑒
(7.4-14)
Where:
𝛿𝑥,𝑠 is the maximum seismic inelastic displacement of the steel storage rack;
𝐶𝑑 is the deflection amplification factor (3.5 in the braced direction or 5.5 in the unbraced
direction);
𝛿𝑥𝑒,𝑠 is the storage rack displacement determined by an elastic analysis;
𝐼𝑒 is the importance factor (see 7.4.2.2).
7.4.11 Seismic separation
The minimum seismic separation shall be determined in accordance with ASCE/SEI 7, Section
12.12.3, as modified in this section.
Seismic separation shall be checked for storage racks assigned to Seismic Design Categories D, E,
or F.
If an analysis is performed, the minimum separation distance between the rack structure and
the building structure, which includes any attached permanent components or elements, shall
be equal to 𝛿𝑀𝑇 , determined as follows:
where:
𝛿𝑀𝑇 = ([𝛿𝑥,𝑠 ]2 + [𝛿𝑥,𝑏 ]2)0.5
(7.4-15)
𝛿𝑀𝑇 is the minimum separation distance between the rack structure and the building
structure;
𝛿𝑥,𝑠
is the maximum inelastic seismic displacement of the steel storage rack
determined in accordance with 7.4.10;
𝛿𝑥,𝑏
is the maximum seismic inelastic displacement of the building structure.
In lieu of an analysis, rack structures shall be separated from the building structure and any
attached permanent components or elements by a distance not less than:

braced direction = 0.02ℎ𝑡𝑜𝑡𝑎𝑙

unbraced direction = 0.05ℎ𝑡𝑜𝑡𝑎𝑙
where:
ℎ𝑡𝑜𝑡𝑎𝑙
is the height of the top level of the storage rack.
7.4.12 Vertical distribution of seismic forces
The lateral seismic load at each vertical storage level shall be determined in accordance with
ASCE/SEI 7, Section 12.8.3, as modified in this section.
The lateral force, 𝐹𝑥 at any level shall be determined from the following equations:
If the centerline of the first storage level is 12 in. (30 cm) or less above finished floor, for the first
storage level:
𝐹1 = 𝐶𝑠𝐼𝑒𝑤1
and for the remaining levels above 12 in. (30 cm):
𝐹𝑥 = (𝑉 − 𝐹1)𝑤𝑥ℎ𝑥
Σni=2 𝑤𝑖ℎ𝑖
(7.4-16)
If the centerline of the first storage level is greater than 12 in. (30 cm) above the floor, for all levels:
𝐹𝑥 = 𝑉𝑤𝑥ℎ𝑥
Σni=1 𝑤𝑖ℎ𝑖
Where:
𝐹1
is the lateral force at the first storage level;
𝐹𝑥
is the lateral force at level 𝑥;
𝑉
is the total design lateral force or shear at the base of the rack;
𝑤𝑖 or 𝑤𝑥 is the portion of the total gravity load on the racks (including live load, dead
load, and product load multiplied by the product load reduction factor (see
7.4.2) located or assigned to designated storage level 𝑖 or 𝑥.
ℎ𝑖 or ℎ𝑥
is the height from the base to storage level 𝑖 or 𝑥.
7.4.13 Horizontal distribution of seismic load at a storage level
The lateral seismic load at each vertical storage level that is to be horizontally distributed
shall be determined in accordance with ASCE/SEI 7, Section 12.8.4, as indicated below.
The seismic design shear at any storage level, 𝑉𝑥 , shall be determined in accordance with the
following equation:
n
𝑉𝑥 = ∑ F𝑖
𝑖=𝑥
where:
𝐹𝑖
is the portion of the seismic base shear, 𝑉, induced at storage
level 𝑖.
(7.4-19)
The seismic design shear, 𝑉𝑥 , shall be distributed to the various vertical elements of the
seismic force resisting system in the level under consideration based on the relative lateral
stiffness of the vertical resisting elements.
7.5 Vertical impact loads
Load-supporting beams and connector components used to attach them to the columns shall be
designed for an additional vertical impact load equal to 25% of one unit load. This impact load
shall be placed in the most unfavorable position when determining maximum load on each
component. For beams whose design capacity is determined by testing (see 13.3), then the
testing shall incorporate the additional impact load. This impact load need not be applied when
checking beam deflections (see 9.3) or designing upright frames, columns, and other vertical
components. For ASRSs (see 7.7 and 12.4), the ASRS manufacturer shall be responsible for
supplying information on maximum vertical static and dynamic loads for the design of stacker
racks to the registered design professional of the storage rack.
7.6 Horizontal loads
The horizontal forces that a rack shall resist varies with the application. The horizontal forces
shall be applied separately, not simultaneously, in the cross-aisle and down-aisle directions.
The rack shall be designed for the most critical of:
a)
notional loads only;
b) earthquake loads + notional loads;
c)
wind loads + notional loads (when applicable);
Additionally, the minimum force for the design of the frame braces and their connections shall
equal1.5%(𝐷 + 𝑃 + 𝐿) based on the maximum loading.
7.7 Storage racks for automated storage and retrieval systems
Storage racks for ASRSs, also known as “stacker racks,” shall incorporate the magnitude,
location, and direction of all loads (static and dynamic) transmitted from the ASRS to the rack
structure. Stacker racks shall also meet the requirements of 7.4.
Forces attributable to stacker racks shall be permitted to not be applied concurrently with the
loads described in 7.3 and 7.4.
7.8 Seismic overturning
Using the indicated product load (𝑃𝑎𝑝𝑝𝑆), storage racks shall be designed to resist cross-aisle
overturning due to seismic forces located at the appropriate shelf levels for both of the following
design conditions:
a)
weight of rack plus every storage level loaded to 67% of its rated load capacity;
b) weight of the rack plus the highest storage level only loaded to 100% of its rated capacity.
NOTE – The 67% value in a) is separate from the 0.67 coefficient associated with 𝑃𝑅𝐹 𝑃
(see 7.4.2.2). For the cross-aisle overturning case in a), 67% of the load weight is present in
the racks. The 0.67 coefficient in 7.4.2.2 is still applied to this weight to compute 𝑊.
8 Design of steel elements and members
8.1 General
The effect of perforations on the load-carrying capacity of compression members shall be in
accordance with ANSI/AISI S100 or ANSI/AISC 360, as applicable, and the modifications in this
section.
8.2 Perforated steel members
8.2.1 Section properties of cold-formed steel sections
Section properties of cold-formed steel sections shall be computed in accordance with
ANSI/AISI S100 with the following exceptions:
a. section properties shall be based on round corners; and
b. section properties shall be based on idealized cross sections with reduced thicknesses
in the strips along the length of the member containing perforations, as shown in Figure
8.2-1.
Figure 8.2-1 – Example of perforation strips in a column
For global (overall) and local buckling calculations, the thickness of the strips containing web and
flange perforation shall be determined using the following equations:
whe
re:
y
𝑡𝑔,𝑤 and 𝑡𝑔,𝑓
are the thicknesses of the strips containing web and flange perforations;
𝑘𝑔
is the global and local buckling coefficient (0.6);
𝑡
is the wall thickness of the steel column;
𝐿𝑛𝑝,𝑤 and 𝐿𝑛𝑝,𝑓
is the distance between perforations as shown in Figure 8.2-1;
𝐿
is the distance between perforation center points as shown in Figure
8.2-1.
For elastic distortional buckling calculations, the thickness of the strips containing web and
flange perforation shall be determined using the following equations:
wh er e:
y
(8.2-2)
𝑡𝑑,𝑤 and 𝑡𝑑,𝑓 are the thicknesses of the strips containing web and flange perforations;
𝑘𝑑
is the distortional buckling thickness coefficient (0.8).
8.2.2 Concentrically-loaded perforated compression members
For cold-formed steel open sections, the nominal axial strength (resistance) (𝑃𝑛) shall be the lesser
of the nominal flexural and local buckling strength (resistance) 𝑃𝑛𝑙𝑔 and the notional distortional
buckling strength
𝑃𝑛𝑙𝑑 , as determined using the following equations:
si
donde
si
(8.2-3)
(8.2-4)
(8.2-5)
To calculate distortional and global buckling for open cold-formed steel sections:
(8.2-6)
(8.2-7)
where:
si
𝜆𝑐
is the slenderness factor for the lesser of the axial elastic global flexural or
torsional-flexural buckling load;
𝜆𝑑
is the slenderness factor of distortional buckling;
𝑃𝑐𝑟𝑒
is the lesser of the axial elastic global flexural or torsional-flexural buckling
strength calculated according to ANSI/AISI S100 or ANSI/AISC 360 with 𝐾 and 𝐿
values defined in
10.2 and 10.3;
𝑃𝑛𝑒
is the lesser of the global buckling axial flexural or torsional-flexural buckling
strength;
𝑃𝑦
is the axial yield load, 𝑃𝑦 = 𝐹𝑦𝐴𝑛𝑒𝑡𝑔;
𝑃𝑐𝑟𝑑
is the elastic critical distortional buckling strength calculated in accordance with
ANSI/AISI S100, with the thickness changes required in 8.2.1, and the thickness
of the strips containing web and flange perforations calculated in accordance with
Equation (8.2-2);
𝑃𝑛𝑙𝑑
is the nominal distortional buckling strength;
𝐹𝑦
is the yield stress;
𝐴𝑛𝑒𝑡𝑔 is the area calculated for global buckling;
𝑄
is the local buckling factor calculated in accordance with 13.2.3.
For hot rolled steel compression members and closed section cold-formed steel compression
members, global flexural buckling, and local buckling, nominal axial strength (resistance) 𝑃𝑛𝑙𝑔.
shall be determined in accordance with Equations (8.2-3), (8.2-4), and (8.2-5).
8.2.3 Perforated members bending about the centroidal axis perpendicular to the axis of symmetry
For open section cold-formed steel members, nominal flexural strength (resistance) (𝑀𝑛) shall
be the lesser of 𝑀𝑛𝑙𝑔 for local and distortional buckling and 𝑀𝑛𝑙𝑑 for distortional buckling as
calculated using the following equations:
(8.2-8)
(8.2-9)
(8.2-10)
where:
𝑀𝑛𝑒
is the nominal flexural strength (resistance) for yielding and global buckling
calculated according to ANSI/AISI S100 modified for the presence of
perforations;
𝑀𝑦
is the yield moment: 𝑀𝑦 = 𝐹𝑦𝑆𝑓𝑦;
𝑆𝑓𝑦
is the elastic section modulus calculated for the section with reduced thickness
about the bending axis for first yielding;
𝜆𝑑
is the slenderness factor of distortional buckling;
𝑀𝑐𝑟𝑑 is the elastic distortional buckling moment calculated in accordance with
ANSI/AISI S100, with the thickness changes required in 8.2.1, and the thickness
of the strips containing web and flange perforations calculated in accordance with
Equation (8.2-2);
𝑄
is the local buckling factor calculated in accordance with 13.2.3.
For hot rolled steel compression members and closed section cold-formed steel members, 𝑀𝑛
shall equal
𝑀𝑛𝑙𝑔 as defined in this section.
9 Beam design
9.1 Calculations
The bending moments, reactions, shear forces, and deflections shall be determined by
considering the beams as simply supported or by rational analysis for beams having partial endfixity. Where the shape of the beam cross-section and end-connection details permit, permissible
loads for pallet-carrying beams shall be determined by conventional methods of calculation
according to ANSI/AISI S100 or ANSI/AISC 360.
9.2 Cross-section
Where the configuration of the cross-section precludes calculation of allowable loads and
deflections, the determination shall be made by tests in accordance with Section 13.
9.3 Deflections
At the unfactored load (excluding impact), the maximum deflection at any point of a beam shall
not exceed 1/180 of the span measured with respect to the ends of the beam. The deflection of
the beam shall be measured when loaded and when unloaded, and the difference between
these two measurements shall be taken as the net deflection that shall be limited to L/180.
9.4 Beam-to-column connections
9.4.1 General
The connections shall have the strength, rotational stiffness, and rotational capacity to be able
to resist the calculated resultant forces, moments, and where required, displacement demands.
The strength, stiffness, and rotational capacity shall be established by test, or where possible,
by calculation.
9.4.2 Connection rotational demand
The rotational capacity, 𝜃𝑚𝑎𝑥 , shall be established by test as the maximum rotation sustained
by the beam- to-column connection over at least two cycles. 𝜃𝑚𝑎𝑥 for the beam-to-column
connection shall be demonstrated by testing as outlined in 13.5 to be greater than the rotational
demand, 𝜃𝐷, using the following equation:
where:
𝜃𝐷
is the rotational demand;
𝛼𝑠
is the first iteration of the second-order amplification term calculated using a
properly substantiated analysis;
𝛿𝑥,𝑠
is the maximum inelastic seismic displacement at the height of the top loaded
storage level as determined in 7.4.10;
ℎ𝑡𝑜𝑡𝑎𝑙 is the height to the top loaded storage level;
𝜃𝑚𝑎𝑥 is the rotation or rotational capacity sustained at maximum moment during
cyclic testing of the beam-to-column connection over at least two cycles.
For seismic design categories A, B, and C, the rotational capacity check need not be made if
the seismic response coefficient is calculated using Equation (7.4-9).
9.4.3 Beam locking device
For storage rack beams and fixed shelves in movable-shelf racks, beams subject to machine
loading shall have connection locking devices (or bolts) capable of resisting an upward force of
1,000 lbf (4,450 N) per connection without failure or disengagement.
9.4.4 Movable-shelf racks
The movable storage levels shall be connected to prevent forward displacement when lifting out
the front beam of the storage level.
9.5 Pallet supports
When pallet support members extending between the storage level beams are furnished, they
shall be designed for the worst loading condition considering the dimensions of the storage
rack, the dimensions and configuration of the bottom of the pallet and the anticipated pallet
placement (see Figure C9.5-1). The storage rack system design shall consider the expected
configuration, condition, and construction of the pallets to be used.
Pallet supports shall be prevented from lateral displacement along the storage level structure in
accordance
with the manufacturer’s instructions.
9.6 Welded-wire rack decking
When welded-wire rack decking is utilized, it shall comply with ANSI MH26.2.
10 Upright frame design
10.1 Upright frames
Upright frames shall be designed for the critical combinations of vertical and horizontal loads for
their most unfavorable conditions as specified in Section 7. All moments and forces induced in
the columns by the beams shall be considered.
Stability, wind resistance (if applicable), and seismic resistance shall be analyzed in each of the
two principal directions of the rack structure separately, but do not need to be analyzed in both
directions simultaneously.
10.2 Column design
10.2.1 Flexural buckling in the direction perpendicular to the upright frames
10.2.1.1 Racks not braced against sidesway
Racks that are not braced to prevent sidesway shall be designed for strength and stability in
accordance with the requirements set forth in 7.2, where 𝐿𝑥 is the distance from the centerline
of one beam to the centerline of the next beam or the distance from the floor to the centerline of
the first beam, and the effective length factor 𝐾𝑥 shall be taken as 1.0.
10.2.1.2 Racks braced against sidesway
Racks braced against sidesway shall have either a rigid and fixed top storage level or diagonal
bracing in the horizontal plane of the top fixed storage level. Increased column capacity shall be
achieved by placing an additional rigid and fixed storage level (or storage levels) or bracing in
the horizontal plane. The unsupported length shall be defined as the distance from the floor to
the fixed top storage level or bracing; or, in the case of an additional rigid fixed storage level (or
storage levels) or fixed storage level with diagonal bracing in its horizontal plane, the
unsupported length is the distance between fixed shelves or braced shelves.
10.2.2 Applicable column length for flexural buckling in the plane of the upright frame
The applicable column length to determine flexural buckling in the plan of the upright frame shall
be established in accordance with criteria defined in ANSI/AISI S100 or ANSI/AISC 360, as
modified in accordance with this section.
𝐿𝑦 shall be taken as the distance along the neutral axis of the column between the intersection
of the neutral axis of the column with the neutral axis of either two adjacent diagonals, two
adjacent horizontals, or a diagonal and a horizontal.
𝐿𝑠ℎ𝑜𝑟𝑡 and 𝐿𝑙𝑜𝑛𝑔 shall be taken as the distances between the intersection of the neutral axis of
the column with the neutral axis of either two adjacent diagonals or a diagonal and a horizontal.
𝐿𝑠ℎ𝑜𝑟𝑡 shall be taken as the shortest distance between the intersection of the neutral axis of
one of the two diagonal braces with the neutral axis of the horizontal brace, or between the
intersections of one diagonal brace with the neutral axis of the horizontal brace with the neutral
axis of the column.
𝐿𝑙𝑜𝑛𝑔 shall be taken as the length of the horizontal brace measured between the neutral axes of
the columns.
NOTE – See Figure C10.2-4(a) in the commentary for visual illustrations of these variables.
For upright frames having diagonal braces or a combination of diagonal and horizontal braces
that intersect the columns, the effective length factor (𝐾) for the portion of the column between
braced points shall be taken as 1.0, provided that the maximum value of the ratio of 𝐿𝑠ℎ𝑜𝑟𝑡 to
𝐿𝑙𝑜𝑛𝑔 does not exceed 0.15.
In an upright frame with diagonals and horizontals, 𝐿𝑠ℎ𝑜𝑟𝑡 and 𝐿𝑙𝑜𝑛𝑔 shall refer to the minimum
and maximum distances between two adjacent segments between two adjacent horizontals. In
an upright frame with only diagonals 𝐿𝑠ℎ𝑜𝑟𝑡 and 𝐿𝑙𝑜𝑛𝑔, shall refer to two adjacent segments. All
distances shall be measured along the neutral axis of the column.
For upright frames having diagonal braces that intersect the horizontal braces, the effective
length factor (𝐾) for the portion of the column between braced points shall be taken as 1.0,
provided that the ratio of
𝐿𝑠ℎ𝑜𝑟𝑡 to 𝐿𝑙𝑜𝑛𝑔 does not exceed 0.12.
All measurements shall be along the neutral axis of the horizontal brace.
For the upright frames having bracing patterns not included above, the effective length factor (𝐾)
of the column shall be determined by rational analysis or by upright frame testing.
10.2.3 Column length for torsional buckling
The column length, 𝐿𝑡, for torsional buckling shall be taken as the length of the member
unbraced against twisting. The effective length shall be taken as 0.8𝐾𝑡𝐿𝑡, where 𝐾𝑡 is the
effective length factor for torsional buckling, provided that the connection details between the
columns and the braces prevent twisting of the column at the brace points. If the connections do
not prevent twist, then the torsional buckling column length can be larger and shall be determined
by rational analysis or testing.
𝐿𝑡 shall be taken as the length of the member unsupported against twisting.
10.3 Frame bracing design
The connections between the column and the brace shall be designed for the maximum
calculated force in the brace or 1.5% of the total load in the column in accordance with 7.6. 𝐿
shall be taken as the length of the brace between connection points, 𝐾𝑥 and 𝐾𝑦 shall be taken
as 1.0, and 𝐾𝑡 shall be taken as 0.8. If the brace is not torsionally restrained at the column, 𝐾𝑡
shall be determined by rational analysis or testing.
10.4 Frame tie design
10.4.1 General
Frame ties and their connections shall be designed to resist the forces outlined herein acting in
tension or compression. The required force for all cases shall be multiplied by the appropriate
load factors used in the cross-aisle seismic analysis. Special requirements for ties and their
connections in sloped-leg and offset- leg frames shall be considered in the structural analysis.
Frame ties shall be installed as shown on the LARC drawings or as specified in the
manufacturer’s
installation instructions.
10.4.2 Back-to-back ties (row spacers)
Where back-to-back ties are used to form a double or multiple-tied frame system, the top backto-back tie shall be placed at an elevation greater than or equal to 80% of the distance from the
floor to the top shelf. The back-to-back tie and its connections shall be designed for the greater
of:
a) the calculated horizontal seismic force of the greater of the two frames being tied
together, assuming the frames are not tied together, when the storage rack is subject to
seismic forces;
NOTE – Seismic design is not required when the storage rack is located in Seismic Design
Category A.
b) the calculated wind load when the storage rack is subject to wind loads; or
c) the non-seismic case for the topmost back-to-back tie only, calculated using the following
equation:
350 lbf × (ℎ𝑏,𝑡𝑜𝑝/ℎ𝑡,𝑡𝑜𝑝)
(10.4-1)
where:
ℎ𝑏,𝑡𝑜𝑝 is the height from the floor slab to the top storage beam level;
ℎ𝑡,𝑡𝑜𝑝 is the height from the floor slab to the top back-to-back tie.
Alternatively, for cases a) and b) above, where lower (or intermediate) level back-to-back ties
are used, the force in the top back-to-back tie shall be permitted to be reduced by the calculated
force resisted by the lower back-to-back ties.
The 350 lbf (1,560 N) applied force shall be considered live load and factored appropriately
depending on whether the ASD or LRFD method is used.
10.4.3 Frame-to-column ties
The frame-to-column ties shall be placed at elevations needed to adequately brace the column to the
frame. The frame to column ties and their connections shall be designed for the greater of:
a)
the calculated seismic force when the storage rack is subject to seismic forces;
b) the calculated wind load when the storage rack is subject to wind loads;
c)
the bracing case, which shall be taken as 1.5% if the total factored load on the column; or
d) the non-seismic case, which shall be taken as 350 lbf (1,560 N).
The 350 lbf (1,560 N) applied force shall be considered live load and factored appropriately,
depending on whether the ASD or LRFD method is used.
10.4.4 Flue shear ties
Flue shear ties and their connections shall be designed to resist the axial loads, shears, and
moments that are being transferred between adjacent frames. The flue shear ties shall be
modeled in the seismic and wind cross-aisle overturning structural analyses. The analysis shall
account for axial, shear, and bearing stiffness of the ties themselves and of the tie connections.
The analysis shall provide an evaluation of localized forces, shears, and moments in the flue
shear ties, columns, and struts, along with the concentrated connection forces between flue
shear ties and columns. The seismic analysis shall account for the largest load of the tandem
frames, assuming the total seismic load of both frames is applied to only one of the frames. For
storage rack subject to wind loads, the wind analysis shall consider shielding and suction
effects.
10.4.5 Cross-aisle ties
Cross-aisle ties and their connections shall be designed for the most critical of:
a)
the seismic case, 𝐹𝑐𝑎,𝑡𝑜𝑝, which is the full seismic base shear in tension and
compression for the worst-case loaded rack, 𝑉𝑐𝑎 (see 7.4.2.2), of one frame in the
cross-aisle direction resisted by the cross-aisle tie, assuming the frames are not tied;
b) the fully calculated wind base shear, in tension and compression, when the storage rack
is subject to wind loads; or
c)
the non-seismic case, which is 350 lbf (1,560 N).
The 350 lbf (1,560 N) applied force shall be considered live load and factored appropriately,
depending on whether the ASD or LRFD method is used.
11 Column base design
11.1 Column base plates
11.1.1 Bearing on concrete
Industrial steel storage racks shall be designed to transfer column forces and moments into the
floor. These forces and moments shall be consistent in magnitude and direction with the rack
analysis.
Unless otherwise specified, the maximum allowable bearing stress on concrete at the bottom of the
effective base plate bearing area shall be determined as follows:
For ASD: 𝑃𝑝⁄Ω𝑐 = (1.7𝑓′ ′c 𝐴𝑏𝑟𝑔)/2.31
(11.1-1)
For LRFD: 𝜙𝑐 𝑃𝑝 = 0.65(1.7𝑓′𝑐𝐴𝑏𝑟𝑔)
(11.1-2)
where:
𝑃𝑝
is the nominal bearing strength;
𝑓′𝑐
is the minimum 28-day compression strength of the concrete floor which, unless otherwise
brought to the attention of the rack manufacturer, shall be assumed to be 3,000 psi
(20 MPa);
𝐴𝑏𝑟𝑔
is the effective base plate bearing area.
11.1.2 Base plate design
11.1.2.1 General
The base plate shall be sized so that the calculated allowable bearing stress (𝐹′𝑝) is not
exceeded. The minimum thickness of the base plate shall be determined by rational analysis or
by an approved test using a test load 1.5 times the ASD design load or the factored LRFD load.
Upon request, information shall be given to the owner or the owner’s agent on the location, size,
and pressures under the column base plates for each type of upright frame in the installation.
When rational analysis is used to determine base plate thickness, and other applicable
standards do not apply, the base plate shall be permitted to be designed for the loading
conditions described in 11.1.2.2 and 11.1.2.3.
11.1.2.2 Downward vertical force
The effective area of the base plate shall be defined as the minimum area needed to satisfy the
concrete bearing requirements or the minimum bearing area required by the concrete slab
designer, and this area ranges from the area bounded by the perimeter of the rack column to
the full area of the base plate. The resulting area shall be defined as the effective base plate
area. The base plate thickness shall be calculated assuming that the bearing pressure is
uniformly distributed over the effective base plate area and the plate shall be analyzed as a rigid
member.
11.1.2.3 Uplift or tension force
The minimum base plate thickness due to a net uplift or tension force shall be determined in
accordance with rational methods and the requirements of ANSI/AISI S100 or ANSI/AISC 360
for flexural members. For yield line analysis, determination of the design bending moment in the
plate shall be calculated as the uplift force times an effective bending arm, accounting for the
anticipated behavior of the base plate. If the plate thickness (𝑡) is adequate to resist the demand
in single curvature (𝑡 > 𝑡𝑛𝑝), prying action shall not be required.
The required minimum base plate thickness (𝑡𝑚𝑖𝑛) shall be calculated as:
The 𝑡 value required to eliminate prying action (𝑡𝑛𝑝) shall be calculated as:
where:
𝑇𝑢
is the uplift computed by structural analysis for Ω0 = 1 per side, where Ω0 is the
overstrength factor defined in 11.3.2. Where there are anchors on both sides of the
column,
𝑇𝑢 equals one-half of the total column uplift;
𝑚
is the distance from the centerline of the anchor to the nearest rack column edge
(bending length);
𝜙
is the bending resistance factor, equal to 0.90;
𝑅𝑦
is the ratio of expected yield stress to specified minimum yield stress, with the
following values:

1.5 for 𝐹𝑦 = 36 ksi minimum;

1.1 for 𝐹𝑦 = 50 ksi minimum; or

1.0 when the actual yield strength of the base plate is used;
𝑝
is the plate width parallel to the nearest rack column edge;
𝐹𝑦
is the minimum specified or actual yield strength of the base plate material.
NOTE – Refer to the commentary for a visual representation of base plate dimensions.
11.2.4 Axial load plus bending (down-aisle seismic or wind)
When downward axial loads and bending moments due to lateral loads exist, the base plate
thickness and anchor forces shall be determined as follows:
𝑒 = 𝑀/𝑃
where:
𝑒
is the base plate axial load eccentricity;
𝑀
is the base moment in the down-aisle direction;
𝑃
is the axial load in the column at the base plate.
(11.1-5)
When 𝑒 ≤ 𝑁/6, where 𝑁 is the effective length of the base plate in the down-aisle direction, it
shall be assumed that no uplift of the base plate will occur. Since no tension force is present in
the anchors and the anchors shall be designed for the maximum calculated shear force. The
base plate thickness shall be determined in accordance with 11.1.2.2.
When 𝑒 > 𝑁/6, it shall be assumed that a tension force can occur in the anchor(s). The tension
force shall be calculated directly once the compressive stress block underneath the plate has
been established. In order to calculate the anchor tension, the designer shall assume either the
peak magnitude of the stress distribution or the length of the stress block. Once the concrete
stress block distribution and magnitude has been established, the anchor tension shall be
calculated directly through the equations of equilibrium. The base plate thickness shall be
determined in accordance with 11.1.2.3.
11.1.3 Column base plate connection rotational demand
When base bending moments are assumed in the design, the base plate shall have a rotational
demand,
𝜃𝑏, of not less than:
(11.1-6)
where:
𝜃𝑏
is the rotational demand;
𝐶𝑑
is the deflection amplification factor (see 7.4.10);
𝛼𝑠
is the gravity load amplification term using 𝑊𝑝𝑖 (see 9.4.2);
𝑀𝑏
is the base moment from analysis determined including 𝐼𝑒 for LRFD. The moment
used for
𝑀𝑏 shall be 1.43 times the computed base moment if the base moment was
computed using the ASD design method determined including 𝐼𝑒 ;
𝐾𝑏
is the base rotational stiffness used in the structural analysis that determined 𝑀𝑏.
If the rotational capacity of the base is exceeded, the structural components shall be modified until
the base rotational demand equation (11.1-6) is satisfied.
11.2 Shims
Shims shall be permitted to be used under the base plate to maintain the plumbness and/or
levelness of the storage rack. The shims shall be made of a material that meets or exceeds the
design bearing strength (LRFD) or allowable bearing strength (ASD) of the floor. The shim size
and location under the base plate shall be equal to or greater than the required base plate size
and location. When shims are present, the anchor length shall be increased, if necessary, to
achieve the design embedment into the concrete floor slab.
The total thickness of a shim stack under a base plate shall not exceed six times the diameter of
the largest anchor bolt used in that base.
Shims stacks shall be secure or fastened together in a fashion that is capable of transferring all
the shear forces at the base. The integrity of the shim stack shall be permitted to be maintained
by a variety of methods including, but not limited to, two or more anchors in the base plate,
friction from overturning compressive forces, nesting, interlocking, welding, adding additional
anchors, or any combination of these methods.
Bending in the anchor associated with shims or grout under the base plate shall be considered
in the design of anchor bolts.
11.3 Anchorage
11.3.1 Anchor bolt design
The anchor bolt design shall comply with ACI 318 Chapter 17. The redundancy factor in the
load combinations found in 7.1.2 and 7.1.3 shall be 1.0.
11.3.2 Overstrength design for anchor bolts
Anchor bolts in racks assigned to Seismic Design Category C or higher shall be designed in
accordance with this section. The required strength of the anchorage, including overstrength
(𝑇𝑎𝑛𝑐ℎ ), shall be calculated as:
𝑇𝑎𝑛𝑐ℎ = 𝑈𝑛𝛺0
(11.3-1)
where:
𝑈𝑛
is the net uplift resulting from LRFD load combination #7 in 7.1.3 or 1.5
times the net uplift resulting from ASD load combination #10 in 7.1.2;
𝛺0
is the overstrength factor.
Tension forces in the anchors shall be calculated either using 𝛺0 = 2 or the maximum tension
expected to be delivered to the anchors by the base plate at the plastic bending moment, 𝑀𝑝.
Alternatively, testing shall be permitted to demonstrate that the reaction forces developed by the
plate do not exceed the anchor group capacity. Shear design forces in the anchors shall be
determined using 𝛺0 = 2.
𝑇𝑎𝑛𝑐ℎ shall be permitted to not be greater than 𝑇𝑚𝑎𝑥 , which is calculated as follows:
a. If 𝑡 > 𝑡𝑛𝑝 (no prying):
b. If 𝑡 < 𝑡𝑛𝑝 (with
prying):
𝑇𝑚𝑎𝑥 =
𝑀𝑝
×𝑁
T𝑚𝑎𝑥 =
𝑚
𝑀𝑝
(11.3-2)
× [1 + (1 − 𝑃𝑒 ) ] × 𝑁
(𝑎⁄𝑚)
𝑚 × 𝑃𝑒2
2
(11.3-3)
The bending strength of the base plate (𝑀𝑝) shall be calculated using the following equation:
𝑀𝑝 = 1.1𝑅𝑦𝐹𝑦𝑍𝑝
where:
(11.3-4)
𝑁
is the number of sides (𝑁 = 1 for anchors on one side of column; 𝑁 = 2 for
anchors on two sides of column);
𝑚
is the distance from the centerline of the anchor(s) to the nearest edge of the rack
column;
𝑎
is the distance from the centerline of the anchor to the edge of the plate (prying
length);
𝑅𝑦
is defined in 11.1.2.3;
𝐹𝑦
is the minimum specified or actual yield strength of the base plate;
𝑍𝑝
is the plastic section modulus of the base plate, calculated using the following
equation:
𝑍𝑝 = 𝑝 × 𝑡2⁄4
𝑃𝑒
is a measure of the prying effect, calculated using the following
equation:
𝑡
=
𝑃𝑒
𝑡𝑛𝑝
(11.3-5)
(11.3-6)
If 𝑃𝑒 < 0.75, then a thicker plate shall be used.
11.3.3 Periodic inspection of anchor bolt installation
Periodic special inspection of rack anchorage shall be conducted on storage racks that are at
least 8 ft (2.4 m) to the top load-supporting storage level and assigned to seismic design
category D, E, or F.
NOTE – See 2021 IBC Section 1705.13.7 for periodic inspection requirements.
When periodic inspection of the anchor bolt installation is required, the owner, or the owner’s
designated representative, shall retain a qualified inspector to conduct the inspection. The
inspection shall be limited to the anchors in the main force-resisting system.
11.4 Slabs and subgrade evaluation
Industrial storage rack systems shall be installed on surfaces consisting of a concrete slab and
subgrade designed to support the rack loads.
NOTE – Typically, the owner is responsible for ensuring the concrete slab and subfloor
conditions, while the rack supplier is responsible for the column loading and base plate
detail information needed to evaluate the slab and subgrade.
12 Special rack design provisions
12.1 Overturnin
12.1.1 General
The registered design professional shall evaluate the storage rack design for uplift forces that
can result in overturning caused by the most unfavorable combination of vertical and horizontal
loads.
12.1.2 Stabilization from anchor bolts and external bracing
Stabilizing forces from anchor bolts shall not be used in overturning calculations unless the
storage rack is anchored to resist calculated uplift forces and the concrete floor slab is designed
and installed to resist the resultant overturning forces. When all columns are anchored to resist
tension forces, the ratio of the restoring moment to overturning moment shall be permitted to be
less than 1.5.
12.1.3 Height-to-depth ratios
The height-to-depth ratio of a storage rack with straight-column style frames shall not exceed 6
to 1, unless the rack is anchored to resist calculated uplift forces or braced externally to resist
overturning. The height of the industrial steel storage rack shall be measured from the floor to
the top loaded storage level and the depth from face to face of the upright frame’s columns at
the floor level.
The height-to-depth ratio of a storage rack with a sloped-column or offset-column frames shall
be based on the upright frame depth measured at the floor. The analysis and design of this
racking, including the anchorage and slab loading, shall include the effects due to the center of
gravity of the applied loading being different from the center of gravity of the support columns at
the floor.
12.1.4 Loading by powered material handling equipment
Storage rack loaded and unloaded by powered material handling equipment that exceeds the 6
to 1 ratio defined above, shall also be designed to resist a 350-lbf. (1,560-N) side force applied
to any single frame at the top loaded storage level. If the LRFD design method is used, the load
factor applied to this force shall be 1.6. This force shall be applied to an empty frame and
divided into as many frames as are interconnected in the direction of the force. Anchor bolts and
base plates shall be designed to resist the resulting uplift forces from this applied force. The
350-lbf (1,560-N) side force need not be applied concurrently with horizontal forces (see 7.6)
and frame columns need not be designed for the additional axial load from this force.
12.2 Interaction with buildings
When storage rack is connected to building areas other than the floor, they shall be designed
and installed to prevent reactions or displacements of the building from damaging the rack. In
addition, connections of racks to buildings shall be designed so the reactions or displacements
of the racks do not damage the building (see 4.10). The design for the industrial storage rack
and building structures shall account for their interaction given their inherently different dynamic
behaviors. The registered design professional responsible for the building shall review and
approve any storage rack connections to areas of the building other than the floor.
The design of rack connections to buildings shall also account for the responses of the building
structure and the storage rack to seismic ground motion. When storage rack is located above
grade elevation, it shall be designed to resist seismic forces and the displacement effects
caused by amplifications of upper-story motions. In these instances, the response of the
building and of the storage rack shall be considered as a combined structure.
12.3 Pick modules and rack supported platforms
12.3.1 General
Pick modules and rack-supported platforms, which are within an industrial or warehouse environment
where access is limited to authorized or trained personnel and are not open to the general public,
shall be designed and configured in accordance with this section.
12.3.2 Design requirements
Rack supported platforms and pick module walkways shall be designed for the maximum
concentrated loads and the maximum uniformly distributed loads that are imposed on the racksupported platform floor. The design of the rack-supported platform or pick module shall
incorporate all anticipated loads for its intended use.
The design load for the foot traffic on pick module walkways shall be specified by the user but
not less than 60 psf (2.9 kN/m2) live load superimposed over the entire area of the foot traffic
walkway. Where applicable, the pick module floor shall also be designed for conveyor leg
loading, pallet staging, shelving, mobile- handling equipment, or any other items that create
additional load on the pick module walkway. The pick module walkway shall also be designed
for other items, such as lights or sprinkler pipes hung from the pick module walkway floor or
floor supports.
If the project specifications dictate that a pick module walkway live load greater than or equal to
100 psf (4.8 kN/m2) is required, and there are two or more elevated floor levels, the live load
shall be permitted to be reduced by 20% for the design of the column framing system, which
includes the support columns, the frame bracing, the frame bracing connections, and the base
plates. This reduction shall not be applied to the beams that support the floor or their
connections.
The maximum live load deflection for beams that support rack supported platforms shall not be
greater than
𝐿/240, where 𝐿 is the length of the beam. The total load deflection shall not be more than
𝐿/180. The clear width of a pick module walkway shall be at least 30 in. (76 cm).
12.3.3 Posting of design loads
The design loads for the floor areas of the rack-supported platforms and pick module walkways
and open areas shall be shown on the LARC drawings. These design loads shall also be
displayed in one or more conspicuous locations within the structure, such as at the top and/or
bottom of the access stairway or ladder.
12.3.4 Safety flooring
Safety flooring shall be designed for a 300 lbf (1,330 N) concentrated load (to support
personnel) and a distributed live load of 60 psf (2.9 kN/m2) acting separately. Safety flooring
shall be used in conjunction with fall protection devices and procedures designed for personnel
protection.
12.3.5 Stairs, ladders, and guards
Fixed stairs or ladders shall be provided for access to elevated rack supported platforms or pick
modules. Stairways, ladders, and vertical and horizontal guarding for these structures shall
meet the design requirements set forth in ANSI MH32.1.
Guardrails shall be provided to protect any other openings through which an order picker could
fall. Where guardrails are omitted for pallet drops, safety gates, removable guardrail sections or
removable chains shall be used for fall protection. These devices shall meet the same strength
and configuration requirements as the permanently installed guardrail. Guardrails shall not be
required to be in place where they would interfere with product being loaded into or removed
from the pick module system. In addition, they shall not be required at locations where other
structural members fulfill the fall through protection requirements. These other structural
members, such as rack frame horizontal members, shall meet the strength and configuration
requirements of the guardrail.
Temporary openings within the guards for designated drop zones on elevated surfaces shall be
equipped with fall protection measures, which can include:
a) a guard that provides continuous protection, such as a double-hung safety gate;
b) a guard that does not provide continuous protection, such as a lift-out, sliding, swing or
pivoting gate, provided the platform includes the support framing for approved fallprotection equipment. The support framing is not required if the potential fall distance is
less than 60 in. (150 cm).
When drop zones are present, the facility shall provide a fall protection program meeting the
requirements of ANSI/ASSE359.2.
12.3.6 Kick-plates (toeboards)
Kick-plates shall extend at least 3.5 in. (90 mm) above the floor surface. Kick-plates shall be
installed at the sides of pallet drop locations and at any additional areas where kick-plates are
needed for protection due to the configuration of the pick module. Kick-plates shall not be
required at picking locations, trash holes, or where rack frame bracing or other structural
components such as shelf decking or safety flooring are next to the edge of the floor.
12.3.7 Conveyor floor openings
All sides of conveyor openings in the floor shall be guarded, except where use of such guardrail
would interfere with the conveyor or product.
Floor openings under the conveyor path that are used for the discharge of trash shall not be
required to have guardrails or kick-plates if they would interfere with the efficient discharge of
trash.
12.3.8 Product fall protection
The design shall consider any locations where operations would require horizontal or vertical
safety barriers to prevent product from falling.
12.4 Storage racks for automated storage and retrieval systems
12.4.1 General
Storage racks for ASRSs shall also be designed for the additional requirements outlined in this
section.
12.4.2 Tolerances
Storage racks for ASRSs shall be designed to tolerances that conform to the requirements of the
automated storage and retrieval device equipment.
12.4.3 Vertical impact loads
Storage racks for ASRSs shall be designed to withstand the maximum vertical static and
dynamic loads imposed by the automated storage and retrieval device equipment.
12.4.4 Horizontal loads
Storage racks for ASRSs shall be designed to withstand horizontal loads as specified in 7.6.
12.4.5 Wind, snow, and roof live loads
Wind (including uplift), snow, and roof live loads for both erection and use shall be included in
the design of the rack, when applicable. In determining the total force on a rack structure, forces
in all members of the structure shall account for the shielding effects, the shape effect, and
other applicable force effects.
The forces specified in 7.4 and 7.6 shall not act concurrently with wind loads.
12.4.6 Deflections
Deflections shall not exceed the limits required for ASRS operation.
12.4.7 Rack compatibility with the equipment
Horizontal and vertical deflections shall be calculated and reviewed with the ASRS equipment
supplier for compatibility.
Rack design shall be compatible with the ASRS equipment. The basic considerations shall
include the height of the first storage level, clearance from the top storage level to the crossaisle tie, shuttle window height, and sprinkler system.
13 Testing
13.1 Test methods
13.1.1 Testing and evaluation of test results
Structural strength or performance characteristics of members and connections that cannot be
evaluated by calculation by this standard, except for this section, shall be determined by testing
in accordance with this section.
The testing and evaluation of results shall be conducted in accordance with procedures
described in ANSI/AISI S100, Sections A and K, except as modified in this section.
13.1.2 Material properties
Material properties shall be determined in accordance with the applicable ASTM A370 test
procedures. Material properties shall be evaluated with tensile coupons taken at the completion
of testing from flat portions of the specimen at regions of low bending moment and shear force.
Alternately, test reports from the mill that produced the steel shall be permitted to be accepted,
as long as the tests were conducted in accordance with applicable ASTM A370 test procedures.
If the effect of cold working is being accounted for by test, the test specimens shall be formed by
the same procedure as is used or contemplated in the finished product.
13.1.3 Testing apparatus and fixtures
Tests shall be carried out in a testing machine or by means of hydraulic jacks in a test frame or by
application of properly measured weights. The testing machine or load-measuring apparatus
shall meet the requirements prescribed in ASTM E4.
The weights of load distribution beams and other fixtures, where relevant, shall be measured
and included in evaluating the test data.
13.1.4 Instrumentation
Dial gages or other deflection measuring devices shall be required to obtain alignment and to
measure load-deflection behavior. The deflections shall be measured and reported to an
accuracy of ±0.03 in. (±0.76 mm).
Strain gages shall be used if behavior characteristics other than ultimate loads and loaddeflection relations are desired.
For members subject to twisting, the angle of twist shall be measured by proper means.
13.1.5 Test report
A test report shall be created for each test conducted and include the following information, at a
minimum:
a. Description of the tested specimens, including a drawing detailing all pertinent
dimensions.
b. Physical steel properties of the tested steel specimen.
c. Detailed drawings of the test setup, showing location and direction of load
application, location of displacement instrumentation and their point of reference,
and details of any deviations from the test requirements. Additionally, photographs
shall supplement the detailed drawings of the test setup.
d. Individual and average load-versus-deformation/rotation values and curves, as
plotted directly, or as reprinted from data acquisition systems.
e. Individual and average maximum test load values observed, description of the
nature, type and location of failure exhibited by each specimen tested, and a
description of the general behavior of the test fixture during load application.
Additionally, photographs to supplement the description of the failure mode(s).
f.
Description of the test method and loading procedure used, rate of loading, etc
g. Further information required in each type of test.
13.2 Stub column tests for cold-formed steel and hot-rolled steel columns
13.2.1 Purpose
A stub column test shall be performed when the determination of the effective section area and
the investigation of the effects of perforations on the local ultimate capacity of a column is
necessary.
13.2.2 Test specimen and procedure
The local buckling factor 𝑄 values of perforated compression members for use in Section 8 shall
be determined by stub column tests as described in AISI S902. The ends of the stub column
shall be milled flat (preferably to a tolerance of ±0.002 in. [0.051 mm]). When the required
flatness can be achieved, welding of the stub-column ends to the endplates shall not be
required. However, when this flatness cannot be achieved, steel endplates shall be continuously
welded to both ends of the specimen so that there is no gap between the ends of the stubcolumn and the end plates. For the purposes of determining 𝑄, the ultimate strength of the stub
column shall be determined.
The axial load shall be applied by flat plates bearing (not welded or otherwise connected)
against the milled ends.
13.2.3 Evaluation of test results
𝑄 shall be calculated using the following equation:
where
:
𝐹𝑦
𝐴𝑛𝑒𝑡𝑔
Ultimate compressive strength of stub column by test
is the actual yield stress actual yield stress of the material as determined from a
coupon test using a coupon from the same coil or cut from the flat of sample
made from the same coil;
is the area calculated for global buckling in accordance with 8.2 considering
perforations.
𝑄 shall not be greater than 1.
Where a series of sections with identical cross-sectional dimensions and identical hole
dimensions and locations are produced in a variety of thicknesses, the stub column shall be
permitted to be conducted only for the largest and the smallest thicknesses (𝑡𝑚𝑎𝑥 and 𝑡𝑚𝑖𝑛). 𝑄
values for intermediate thicknesses shall be determined by interpolation according to the
following equation:
where:
𝑄
𝑄𝑚𝑎𝑥, 𝑄𝑚𝑖𝑛
respectively.
is the value for the intermediate thickness, 𝑡;
are values obtained by test for the largest and smallest thicknesses,
This interpolation shall be permitted only if the yield stresses of the two specimens do not differ
by more than 25% and if the yield points of the intermediate thicknesses fall between or below
those of the test specimens.
13.3 Pallet beam tests
13.3.1 Purpose
Pallet beam tests shall be performed to determine flexural behavior patterns and parameters,
such as the yield moment, ultimate moment, and effective flexural rigidity (EI). The tests shall be
permitted to be performed with beams being simply supported or supported as part of an upright
frame.
13.3.2 Simply supported pallet beam tests
For beams that are not subject to significant torsional stresses or distortions, the simply
supported pallet beam test shall be conducted only if the flexural behavior parameters such as
the yield moment, ultimate moment, and the EI shall be determined. For EI, tests shall be
conducted on two identical specimens unless a third test is required as specified in 13.3.2.3. If
lateral restraints are required, the beams shall be tested in pairs as they would be used in
completed assemblies.
13.3.2.1 Test setup
A typical test setup is shown in Figure 13.3-1. The test set-up shall consist of a beam test
specimen simply supported at each end (not connected to columns). The test load shall be
applied to a load distribution beam which imposes a load at two points on the beam and
imposes a load at two points on the beam specimen. Each load point on the beam test
specimen shall be set at a distance of 𝑆/𝐶 from the support; where 𝑆 is the span and 𝐶 is a
numerical value between 2.5 and 3. Plates shall be permitted to be used to prevent local failure
at supports or at load points.
Figure 13.3-1 – Simply-supported pallet beam test setup
13.3.2.2 Test procedure
After alignment, a small initial load of about 5% of the expected ultimate test load shall be
applied to the test assembly to ensure firm contact between the specimen and all loading and
support components. At this load, initial readings shall be taken from all gages. Loads shall then
be applied in increments no larger than about one-fifth of the expected design load. Readings
shall be taken for all load increments.
All specific events noticeable by visual inspection, such as local buckling, crippling, failure of
connections, etc., shall be recorded at the loads at which they occur.
13.3.2.3 Evaluation of test results
The parameters investigated shall be determined by test results by conventional methods.
The flexural rigidity shall be calculated based on the results of two tests of identical specimens,
provided that the deviation from the average value does not exceed 10%. If the deviation from
the average exceeds 10%, then a third identical specimen shall be tested. The average of the
two lower values obtained from the tests shall be the result from the series of tests.
13.3.3 Pallet beam in upright frames assembly test
13.3.3.1 Purpose
This test shall be performed to determine the design loads when rational analysis is not a viable
option.
13.3.3.2 Test setup
The test assembly shall consist of two upright frames not bolted to the floor and two levels of
pallet beams with front-to-back ties when specified.
The upright frame height shall not be limited. However, the bottom level beams shall be tested
and shall be located so there is a minimum of 24 in. (610 mm) clearance between the test
beams and the floor or between the test beams and the top-level beams.
The end connections shall be those used in the finished product.
The location of the test loads perpendicular to the beams shall simulate actual loading.
13.3.3.3 Test procedure
The test procedures specified in 13.3.2.2 of this report shall be used.
13.3.3.4 Evaluation of test results
The design load shall be the smallest of the following:
a)
Strength determined according to the applicable provisions of ANSI/AISI S100 Section K
and its subsections.
b) Two-thirds of the load at which harmful or objectionable distortions are observed in the
connections or elsewhere. These distortions include rotations of such magnitude as to
render the beam unserviceable.
The load (not including impact) at which maximum vertical deflections attain 1/180 of the
span, measured with respect to the ends of the beams.
13.3.3.5 Number of tests required
c)
The number of tests for determining design loads shall be as specified in ANSI/AISI S100 Section
K.
13.3.3.6 Deflection test
Once the design load has been determined as specified in 13.3.3.2 through 13.3.3.3, an
additional test shall be conducted using a new set of specimens. An initial load equal to the
design load shall be applied, reduced to zero and the deflection read; this deflection reading
shall be the zero-reference reading. A load equal to 1.5 times the design load shall then be
applied, and the deflection read. The load shall then be held constant for one-quarter of an hour
and the deflection read again. This deflection reading shall not exceed the previous reading by
more than 5%. The load shall then be reduced to zero and the residual or permanent deflection
read. The net residual deflection of the beam shall not exceed 15% of the final deflection
measured at 1.5 times the design load. If these limitations are not met, the design load shall be
reduced accordingly, or the source of residual deflections determined and remedied, and the
test repeated with new specimens.
13.4 The cantilever test Purpose
This test shall be conducted to determine the connection moment capacity.
13.4.1Test setup
The test setup shall consist of a pallet beam at least 26 in. (660 mm) in length connected to the
center of a column at least 30 in. (760 mm) in length, as illustrated in Figure 13.4-1. Both ends
of the column shall be rigidly connected to rigid supports. The load shall be applied to the pallet
beam at 24 in. (610 mm) from the face of the column. At this load application point, a dial gage
shall be mounted to measure deflections.
Figure 13.4-1 – The cantilever test setup
13.4.3 Test procedure
The test procedure specified in 13.3.2.2 shall be used.
13.4.4 Evaluation of test results
The design moment shall be determined in a manner similar to that specified in 13.3.3.4 a) and b).
If the relationship between the moment and the angular change at a joint is not linear, the following
equation shall be used for determining a constant value of 𝐹 to be used in a linear analysis:
where
(𝑅. 𝐹. ) is a reduction factor to provide safety considering scatter of test results;
𝑃0.85 is 0.85 times the ultimate load;
𝛿0.85 is the deflection of the free end of the cantilever at load 𝑃0.85;
𝐿𝑐, 𝐿𝑏, 𝐼𝑐 , 𝐼𝑏 are the same lengths and moments of inertias of the columns and the
beam, respectively.
For the design of the beams, the reduction factor (𝑅. 𝐹. ) = 2/3 shall be used, since a lower 𝐹
means a higher design moment for the beam. For the bending moment of the column, (𝑅. 𝐹. ) = 1.0
shall be used, since a higher 𝐹 leads to a more conservative value of the bending moment.
NOTE – This section is used for beam design. Refer to 13.5 for design of connections for
semi-rigid framing.
𝐹 shall be calculated on the basis of the average results of two tests of identical specimens,
provided that the deviation from the average results of two tests does not exceed 10%. If the
deviation from the average exceeds 10%, then a third specimen shall be tested. The average of
the two higher values shall be used as the result in the column design.
13.5 Cyclic testing of beam-to-column connections
13.5.1 Purpose
This test shall be conducted to provide requirements for qualifying cyclic tests of beam-tocolumn moment connections in steel storage rack subjected to seismic loads.
13.5.2 Test specimen
The testing program shall include tests of at least two test specimens of each combination of
beam and column and connector size. The size of the beams and columns used in the test
specimen shall be representative of typical, full-size storage rack beams and columns, and shall
represent the inelastic action in the column, as described in 13.5.3 a). The beam-to-column
connectors, and the connection details used in the test specimen, shall represent the typical fullsized connection details as closely as possible. The connection elements used in the test
specimen shall be representative of typical full-size storage rack connectors and connection
details.
Welds on the test specimen shall satisfy and be performed in accordance with ANSI/AWS
D1.1/D1.1M or ANSI/AWS D1.3/D1.3M, as applicable. The bolted portions of the test specimens
shall replicate the bolted portions of the finished product connection as closely as practicable.
Each member of the connection element that contributes to the inelastic rotation at yielding shall
be tested to determine its yield stress and yield strength. Tension testing shall be conducted on
samples of steel taken from the material adjacent to each test specimen. Tension test results
from certified mill test reports shall be reported, but are not permitted to be used in place of
specimen testing for the purposes of this section. Tension test results shall be based upon
testing that is conducted in accordance with the appropriate ASTM testing protocols for the
materials being used.
13.5.2.1 Inelastic rotation in the test specimen
Inelastic rotation shall be developed in the test specimen by inelastic action in the same
members and connection elements as anticipated in the prototype, i.e., in the beam, in the
column, in the panel zone, or within the connection elements. The fraction of the total inelastic
rotation in the test specimen that is developed in each member or connection element shall be
at least 75% of the anticipated fraction of the total inelastic rotation in the prototype developed in
the corresponding member or connection element.
The following additional requirements shall be satisfied for each member of the connection
element of the test specimen that contributes to inelastic rotation at yielding:
a)
The yield stress shall be determined by material tests on the actual materials used for
the test specimen, as specified below. Because of the amount of cold-working to which
the connector is subjected in manufacture and testing, the yield stress for connectors
shall be determined from connectors taken from identical neighboring components in the
manufacturing sequence. The use of yield stress values that are reported on certified
mill test reports are not permitted.
b) The yield stress of the beam shall not be more than 15% percent below 𝑅𝑦𝐹𝑦 for the
grade of steel being used for the corresponding elements of the test specimen.
Columns, connectors, and connector elements with a tested yield stress shall not be
more than 15% above or below 𝑅𝑦𝐹𝑦 for the grade of steel to be used for the
corresponding elements of the test specimen. 𝑅𝑦𝐹𝑦 shall be determined in accordance
with ANSI/AISC 341 Section 6.2, where 𝐹𝑦 is the minimum specified yield strength, and
𝑅𝑦 is the ratio of the expected yield strength to the minimum expected yield strength 𝐹𝑦.
13.5.2.2 Tension testing in the test specimen
Tension testing shall be conducted in accordance with the appropriate ASTM testing protocols
for the particular materials being used, with the following exceptions:
a)
The yield stress, 𝐹𝑦, that is reported from the test shall be based upon the yield strength
definition in ASTM A370, using the offset method at 0.002 strain; and
b) The loading rate for the tension test shall replicate, as closely as practicable, the loading
rate to be used in the test specimen.
Tension testing shall be conducted and reported for the following portions of the test specimen:
a)
flange(s) and web(s) of beams and columns at standard locations; and
b) any element of the connector that contributes to inelastic rotation by yielding.
13.5.2.3 Bolted portion of test specimens
The beam-to-column connectors, and the connection details used in the test specimen, shall
represent the typical full-sized connection details as closely as possible. The connection
elements used in the test specimen shall be representative of typical full-size storage rack
connectors and connection details.
The bolted portions of the test specimen shall replicate the bolted portions of the finished
product connection as closely as practicable.
a)
The bolt grade used in the test specimen shall be the same as that used for the finished
product.
b) The type and orientation of bolt holes used in the test specimen shall be the same as
those to be used for the corresponding bolt holes in the finished product.
c)
When inelastic rotation is to be developed either by yielding, or by slip within a bolted
portion of the connection, the method used to make the bolt holes in the test specimen
shall be the same as that used in the corresponding bolt holes in the finished product.
d) Bolts in the test specimen shall have the same installation and faying.
13.5.3 Test setup
The test setup shall include the following features:
a)
a test specimen consisting of a column element and two cantilever beam elements
attached to both sides of the column with beam-to-column connections integrally
attached at one end of the beams (Figure 13.5-1);
b) the test specimen shall incorporate points of inflection that coincide or mimic the
anticipated points of inflection under earthquake loading;
c)
lateral bracing for the test specimen is permissible as needed to provide lateral bracing
for testing. Additional lateral bracing shall also be used if lateral bracing is incorporated
into the finished product.
The test setup shall include two independent actuators located at points P L and PR to measure
the two different forces developed at the two beam ends, where equal displacement forces are
applied.
Figure 13.5-1 – Beam-to-column cyclic test setup
13.5.4 Test procedure
Inelastic rotation shall be developed in the test specimen by inelastic action in the same
members and connection elements as anticipated in the finished product, i.e., in the beam, in
the column, in the panel zone, or within the connection elements. Sufficient instrumentation
shall be provided on the test specimen to permit measurement or calculation of the quantities
required to produce meaningful, reproducible results for this procedure.
Prior to the application of any cyclic loading, a constant downward load, 𝑃𝑐 , of one kip shall be
applied to each beam segment adjacent to each connector on both sides of the beam-tocolumn connection, simulating the design downward-acting gravity pallet loads that serve to
fully engage the beams and their connectors into the columns receiving them.
The test specimen shall be subjected to cyclic loads according to the requirements prescribed
for beam-to- column moment connections in moment frames. Loading shall proceed with the
application of equal displacements, 𝐷, at each end of each beam, and the measurement of the
forces, 𝑃𝐿 and 𝑃𝑅 , corresponding to each such displacement.
The magnitudes of loading steps shall be determined by the peak drift angle imposed on the
test specimen. The peak drift angle, 𝜃, shall be taken as the maximum positive and negative
vertical net displacement (from connector rotation only), 𝛥, divided by the distance ℓ (see Figure
13.5-1). The net displacement test data shall be the sum of beam deflection, connector rotation
and column deflection. To obtain the net connector rotation, the beam deflection caused by the
beam bending and the column rotation shall be subtracted from the total deflection of the arms
to obtain the net deflection caused by only the connector rotation.
Qualifying cyclic tests of storage rack beam-to-column connections shall be conducted by
controlling the peak drift angle, 𝜃, imposed on the test specimen as summarized in Table 13.51. The test specimen shall satisfy the strength and drift angle requirements for the connection,
as applicable, and sustain the required drift angle for at least one complete loading cycle.
Table 13.5-1 – Beam-to-column testing load steps and cycles
Loa
No. of
d
cycles
step
1
3
2
3
3
3
4
3
5
2
6
2
𝑛
2
Drift angle
𝜃 = 0.025 radians
𝜃 = 0.050 radians
𝜃 = 0.075 radians
𝜃 = 0.100 radians
𝜃 = 0.150 radians
𝜃 = 0.200 radians
increase at increments
of
𝜃 = 0.050 radians
Alternate testing requirements are permitted when approved by the registered design
professional and the AHJ. In such cases, loading sequences other than those specified shall be
permitted to be used provided they are demonstrated to be of equivalent or greater severity.
13.5.5 Evaluation of test results
The results of the tests shall be used to determine the median value of drift angle capacity for
the performance states described below. The drift angle limit, 𝜃, for various performance levels
shall be defined as indicated in Table 13.5-2.
Table 13.5-2 – Drift angle limit performance levels
Performance level
Strength
degradation
Ultimate
Symbol
𝜃𝑆𝐷
𝜃𝑈
Drift angle capacity
Taken as the value of 𝜃 at which either failure of the
connection occurs, or the strength of either connection
degrades to less than the nominal capacity, whichever is less.
Taken as the value of 𝜃 at which connection damage is so
severe that continued ability to remain stable under gravity
loading is uncertain.
The test specimen shall satisfy the strength and rotational demand requirements of this test
program for the connection, as applicable. The test specimen shall sustain the required
rotational demand for at least one complete loading cycle.
The test specified in this section shall be used to determine the moment strength and rotational
capacity of the beam-to-column connection as follows.
1.
Determine the average of the lowest combined moment for each direction of each cycle:
𝑀𝑎𝑣𝑔 = 𝑀𝑙𝑒𝑓𝑡 + 𝑀𝑟𝑖𝑔ℎ𝑡
(13.5-1)
Each cycle in the test is for a specific 𝜃 value which is 𝜃𝑡𝑜𝑡𝑎𝑙.
2.
Since this is for two connectors, the moment per connector is:
𝑀𝑐𝑜𝑛𝑛 = 𝑀𝑎𝑣𝑔/2
3.
Compute 𝜃𝑐𝑜𝑛𝑛for each cycle using the following equation.
(13.5-2)
4.
Find 𝑀𝑚𝑎𝑥 and 𝜃𝑚𝑎𝑥 from the test data. 𝑀𝑚𝑎𝑥 is the maximum moment at which the
connector can still sustain two cycles. 𝜃𝑚𝑎𝑥 is the corresponding rotation where 𝑀𝑚𝑎𝑥
occurs. The 𝑀𝑚𝑎𝑥 value is described in 7.2.5.
5. Find 𝜃𝑐𝑜𝑛𝑛 at 𝑀 = 0.8𝜙𝑀𝑚𝑎𝑥 in accordance with 7.2.5.
6.
For design by second order analysis (notional load):
𝐾𝑐𝑜𝑛𝑛 = 0.8𝜙𝑀𝑚𝑎𝑥⁄𝜃𝑐𝑜𝑛𝑛.
7.
(13.5-4)
The final connection moments from the second order analysis shall not exceed
0.8ϕ𝑀𝑚𝑎𝑥 . where:
𝑀𝑙𝑒𝑓𝑡 is the moment on left cantilever arm assembly at a specific cycle in the cyclic load
test
(𝑃𝐿𝐿𝑏);
𝑀𝑟𝑖𝑔ℎ𝑡 is the moment on right cantilever arm assembly at a specific cycle in the cyclic load
test
(𝑃𝑅 𝐿𝑏);
𝜃𝑡𝑜𝑡𝑎𝑙 is the total rotation at the end of the cantilever arm assembly at a specific cycle in
the cyclic load test. Since the cyclic test is displacement based the displacement
for each stage of
the test is dictated by the testing procedure and given in the test data. 𝜃𝑡𝑜𝑡𝑎𝑙 at
each stage is the displacement at the point of application of 𝑃𝐿 or 𝑃𝑅 divided by
the distance from the column to the point of load application 𝐿𝑏;
𝑀𝑎𝑣𝑔
is the average of combined lowest moment 𝑀𝑙𝑒𝑓𝑡and 𝑀𝑟𝑖𝑔ℎ𝑡 for a cycle in the
cyclic load test;
𝑀𝑐𝑜𝑛𝑛 is the moment per connector which is the average of lowest combined moment
divided by two;
𝜃𝑐𝑜𝑛𝑛 is the net rotation of the beam-to-column connector. This is the total rotation
minus the rotations of the beam and the column as shown in step 3;
𝐾𝑐𝑜𝑛𝑛 is the connector spring constant;
𝐿𝑐
is the length of column in cyclic test (typically 30 in. [76 cm]);
𝐿𝑏
is the distance from the column to the point of force application in cyclic test
shown in Figure 13.5-1 (typically 24 in. [61 cm]);
𝐼𝑐
is the moment of inertia of the column used for global buckling analysis;
𝐼𝑏
is the moment of inertia of the beam of the cantilever arm assembly;
𝐸
is the modulus of elasticity.
A written test report meeting the requirements of the AHJ shall be prepared for each test
specimen. The report shall include items outlined in 13.1.5 and thoroughly document all key
features and results of the test, including:
a)
A drawing or clear description of the test specimen and test setup, including key
dimensions, boundary conditions at loading and reaction points, and location of any
lateral braces.
b) A drawing of the connector and connection details, showing member sizes, grades of
steel, the sizes of all connector and connection elements, welding details including any
filler metals, the sizes and locations of any slots or bolt holes, the size and grade of
bolts, and all other pertinent details, of the connection.
c)
A listing of essential variable for the test specimen, including sources of inelastic
rotation, material strength, size of members, connection details, welds, and bolts.
d) A listing or plot showing the applied load and displacement history of the test specimen.
e)
A plot of the applied load versus the displacement of the test specimen. The
displacement reported in this plot shall be measured at or near the point of load
application. The locations on the test specimen, where the loads and displacements
were measured, shall be clearly identified.
f)
A plot of beam moment versus drift angle for beam-to-column moment connections. For
beam-to- column connections, the beam moment and the drift angle shall be computed
with respect to the centerline of the column.
g) The drift angle and the total inelastic rotation developed by the test specimen. The
components of the test specimen contributing to the total inelastic rotation due to
yielding or slip shall be identified. The portion of the total inelastic rotation contributed by
each component of the test specimen shall be reported. The method used to compute
inelastic rotations shall be clearly shown.
h) A chronological listing of significant test observations, including observations of yielding,
slip, instability, tearing, and fracture of any portion of the test specimen, as applicable.
i)
The controlling failure mode for the test specimen. if the test is terminated prior to failure,
the reason for terminating the test shall be clearly indicated.
j)
The results of the material tests specified under material testing requirements, above.
k) The Welding Procedure Specifications (WPS) and welding inspection reports. These
items shall be prepared either by the manufacturer or the testing laboratory.
13.6 Column base fixity testing
13.6.1 Purpose
This procedure shall be conducted to determine the base fixity parameters of rack columns for
given axial loads, including:
a)
ultimate and design moments of column bases for a specified column axial load; and
b) design moment-rotation fixity for column bases for a specified column axial load.
The following setup and procedure represent one method to conduct the base fixity test;
however, other test setup methods that produce equivalent results shall be permitted to be
used.
13.6.2 Definitions
Refer to Figure 13.6-1 for test setup.
c1, c2, c3 are measuring devices;
𝑑23
is the distance between measuring devices;
F1, F2 are the forces applied by the jacks;
g
is a concrete block;
h
is a column segment;
J1, J2 are hydraulic jacks;
L
is the distance between the load application joint and the concrete block;
𝑎
is the distance between the support and the load application joint;
θ𝑏
is the rotation of the base plate;
𝛽
𝛿
is the angle between axial force and initial alignment; 𝛽 = arctan ( 1⁄𝑎);
𝛿1
is the displacement of the top of the column segment measured by 𝑐1.
13.6.3 Precision
Loads shall be recorded to a precision of 1% of the anticipated ultimate load during application of
test loads. Deflections shall be recorded to a precision of 0.01 in. (0.25 mm).
Figure 13.6-1 – Column base fixity test setup
Test specimen fixture and set-up
The column base fixity testing test specimen and set-up shall meet the following requirements:
a)
The test setup is illustrated in Figure 13.6-1. The column used shall be at least four
times as long as the largest dimension of the column cross-section and shall have a
base plate bearing on the concrete representing the floor.
b) The properties of the column segment, the concrete block shall be the same as those of the
finished product.
c)
The base plate of the column and the details of how it is connected to the concrete cube
shall be the same as in the finished product.
d) The hinges shall be allowed to move only in the direction they move in the finished product.
e)
Axial loads shall be applied by means of hydraulic cylinders capable of correcting the
applied axial load 𝐹1 so that the axial load on the base plate is the target base plate axial
load at any given lateral deflection.
f)
The column and its base plate shall be oriented depending on whether the down aisle or
cross aisle behavior is being investigated.
g) The concrete block (g) shall be at least 12 in. (30.5 cm) thick and shall extend at
least 6.5 in. (16.5 cm) beyond the edges of the base plate on all sides. The concrete
strength shall be at least 4,000 psi (27,600 kPa). The concrete strength shall be verified
prior to tests.
h) The end rotation of the column, 𝜃𝑏, with respect to the concrete block shall be
determined from the deflection measuring devices c2 and c3, as shown in Figure 13.6-1.
The displacement measuring devices shall be able to measure the relative displacement
between the concrete block and the column end.
i)
The bar touching devices c2 and c3 shall be attached to the column as close as possible
to the concrete block as shown in Figure 13.6-1.
The end of the column at the location of the load application shall permit in-plane
displacements and restrain out-of-plane displacements.
13.6.5 Test procedure
j)
The levels of the axial loads F1 shall be chosen to provide a range of values up to the required
design load for the column. The lowest axial load level shall be approximately 10% of the
effective area design load. 10% of the effective area design load with a resistance factor of 0.5
shall be calculated using the following equation:
0.5𝐹𝑦𝐴𝑛𝑒𝑡𝑔𝑄
(13.6-1)
The highest axial load in the series shall be the required design load. Tests shall be carried out
for at least two other intermediate axial load levels. The number of tests carried out at each axial
load level shall be determined in accordance with 13.2.
At the start of each test, the load in Jack No. 1 shall be set at a minimum value which keeps all
the components in contact and the displacement measuring devices zeroed. The load in Jack
No. 1 shall then be increased to its required value and held constant at that value. If the top of
the column moves, the displacements shall be noted, and the load in Jack No. 2 shall be
applied in the same direction as the movement. The load in Jack No. 2 shall then be increased
and further displacement observations shall be made until this load reaches its required value.
Depending on the desired information, the following two loadings shall be used:
a)
The load perpendicular to the base plate 𝐹1 cos 𝛽 shall be held constant while the bending
moment shall be increased in sufficiently small steps (usually one tenth of the expected
maximum moment at the base plate).
b) Both the load perpendicular to the base plate and the bending moment at the base plate
shall be increased monotonically in sufficiently small steps. The ratio of the loads shall
be decided depending on the end use contemplated.
Tests shall be carried out at axial load levels relevant for the design use. At each axial load
level, the number of tests shall be decided upon according to ANSI/AISI S100 Section K2.
No test result shall be eliminated unless a rationale for its exclusion can be given.
The ultimate bending moment for the column base, 𝑀𝑢, shall be the maximum moment that can be
reached.
Evaluation of test results
The moment applied to the base, 𝑀𝑏, and rotation, 𝜃𝑏, shall be calculated as follows:
𝑀𝑏 = (𝐹2 + 𝐹1 sin 𝛽)𝐿 + (𝐹1 cos 𝛽)𝑑1
(𝑑3 − 𝑑2)
⁄𝑑
𝜃𝑏 =
2
3
a)
(13.6-2)
(13.6-3)
Corrections of yield and thickness of the column and base plate need not be considered
if the difference between the test sample and the nominal value is 15% or below.
b) Evaluation of the test results and the determination of the available strength and/or
design strength (resistance) shall be made in accordance with the procedures described
in ANSI/AISI S100 Section K2.
c)
The column base design moment shall be taken as 0.6𝑀𝑢.
d) The column base stiffness 𝑘 shall be taken as the base design moment divided by the
column base rotation, 𝜃, at column base design moment.
Static testing of frame bracing
connections Purpose
This test determines the axial stiffness and axial strength of upright frame column to brace joints.
Symbols
The symbols described below are illustrated in Figure 13.7-1.
𝐹
is the force in the axial load actuator;
𝛿𝑏
is the mean of the two displacement transducer readings on each side of the
brace in the direction shown in Figure 13.7-1;
𝛿𝑤𝑏
is the mean of the two displacement transducer readings at mid span on the
bottom of the beam in the direction shown in Figure 13.7-1.
Precision
Loads shall be recorded to a precision of 1% of the anticipated ultimate load during application
of test loads. Deflections shall be measured and recorded to a precision of 0.01 in. (0.25 mm).
Figure 13.7-1 – Test set-up for joints with braces in tension or
compression
Test specimen, fixture, and set-up
Test specimens shall be representative of the finished
product. The test fixtures and setups shall be as shown in
Figure 13.7-1.
The column and the brace shall be connected as in the finished product. The dimensions shown
in Figure 13.7-1 are examples and are adjustable based on the overall geometry of the columns
and braces.
Lateral restraint shall be provided as shown in Figure 13.7-1 when the brace is in compression.
Lateral restraint shall prevent displacement in the plane and perpendicular to the plane of the
setup. To the extent possible, the lateral restraint shall not restrain the axial direction of the
brace. The location of the lateral restraint shall be such that local deformations at the joint shall
not be affected.
Loads shall be applied by means of hydraulic actuators as shown in Figure 13.7-1.
Two end fixtures with a pin located at the center of gravity of the column shall be mounted at
each end of the column. The distance between the pins is variable depending on the geometry
of the cross section; however, it shall not be less than 24 in. (61 cm).
One end of the column shall be connected to the base with a hinge and the other shall be
connected to the base with a sliding hinge as shown in Figure 13.7-1.
In all cases, if the column is a lipped section, the section with the lips shall be on top.
In the tension case, if desired, the spherical pin joint on top shall be permitted to not be used if
special care is taken to prevent any damage.
Lateral restraint shall be permitted to be used in the case where the brace is in tension.
Displacement devices 𝑏, 𝑓, ℎ, 𝑟, 𝑤𝑏, 𝑚𝑠 shown on Figure 13.7-1 shall be placed on both sides
of the column or the brace.
Deflection measuring devices 𝑓, ℎ, 𝑚𝑠, 𝑟 and 𝑤𝑠 shall be permitted to be optional if further
checks are desired.
Test procedure
Testing shall be conducted using the following procedure:
a)
The sensors shall be set to zero.
b) The load shall be gradually increased until the joint reaches the final failure load.
c)
Values of the applied force and the displacements shall be recorded.
d) Type of failure shall be recorded.
Evaluation of test results
Evaluation of the test results and the determination of the available strength and/or design
strength (resistance) shall be conducted in accordance with the procedures described in
ANSI/AISI S100, Section K2.
The stiffness of the joint shall be expressed in terms of the local extension of the joint
(displacement), 𝛿𝑠
for right angle joints and 𝛿𝑑𝑖𝑎𝑔 for diagonal joints divided by the axial force in
the brace. Values of 𝛿𝑏 and 𝛿𝑤𝑏 for each load level 𝐹 and shall be recorded.
The stiffness of the joint for each load level shall be calculated as:
(𝛿𝑏 − 𝛿𝑤𝑏)⁄
𝐹
Cyclical testing of upright frame bracing
(13.7-1)
connection Purpose
This test provides an alternate procedure to the simplified analysis method for determining the
seismic strength, stiffness, and hysteretic cyclic properties of the bracing connection in an
upright frame based on cyclic testing.
Symbols
The symbols described below are illustrated in Figure 13.8-1.
𝐹
is the force in the axial load actuator;
𝛿𝑏
is the mean of the two displacement transducer readings on each side of the
brace in the direction shown in Figure 13.8-1;
𝛿𝑤𝑏
is the mean of the two displacement transducer readings at mid span on the
bottom of the beam in the direction shown in Figure 13.8-1.
Figure 13.8-1 – Test setup for joints with braces in tension or
compression
NOTE –The compression force 𝐹 is the only force shown in the figure.
Precision
Loads shall be recorded to a precision of 1% of the anticipated ultimate load during application
of test loads. Deflections shall be measured and recorded to a precision of 0.01 in. (0.25 mm).
Test specimen, fixture, and setup
Test specimens shall be representative of the finished
product. The test fixtures and setups shall be as shown in
Figure 13.8-1.
The column and the brace shall be connected as in the finished product. The dimensions shown
in Figure 13.8-1 shall be permitted to be adjustable for the overall geometry of the columns and
braces.
Lateral restraint shall be provided as shown in Figure 13.8-1. Lateral restraint shall prevent
displacement in the plane and perpendicular to the plane of the setup. To the extent possible
the lateral restraint shall not restrain the axial direction of the brace. The location of the lateral
restraint shall be such that local deformations at the joint shall not be affected.
Loads shall be applied by means of a hydraulic actuator as shown in Figure 13.8-1.
Two end fixtures with a pin located at the center of gravity of the column shall be mounted at
each end of the column. The distance between pins is variable depending on the geometry of
the cross section; however, it shall not be less than 24 in. (610 mm).
One end of the column shall be connected to the base with a hinge and the other shall be
connected to the base with a sliding hinge, as shown in Figure 13.8-1.
In all cases, if the column is lipped, the section with the lips shall be on top.
The brace shall have a lateral restraint in both directions (in plane and out of plane) to prevent
damage to the hydraulic jack and load measuring device.
Displacement devices 𝑏, 𝑓, ℎ, 𝑟, 𝑤𝑏, 𝑚𝑠 shown on Figure 13.8-1 shall be placed on both sides
of the column or the brace.
Deflection measuring devices 𝑓, ℎ, 𝑚𝑠, 𝑟 and 𝑤𝑠 shall be permitted to be optional if further
checks are desired.
Test procedure
Before the cyclic tests, two static tests with the brace in tension and two tests with the brace in
compression to failure shall be carried out.
In the cyclic tests, the load shall be applied in cycles, each ranging from:
+𝐶 × 𝐴 to −𝐶 × 𝐴
where
:
𝐶
is the factor as shown in Table 13.8-1;
𝐴
is the deflection in the non-cyclic tests:
𝐴 = 0.06 (𝛿𝑎𝑐 + 𝛿𝑎𝑡)
where
:
𝛿𝑎𝑐
𝛿𝑎𝑡
(13.8-1)
(13.8-2)
is the absolute value of the displacement at maximum compression force
reached during the static test;
is the absolute test value of the displacement at maximum tension force
reached during the static test.
At each loading cycle, the deflections shall be continuously recorded in such a way that they
can be used to calculate the area within the force deflection curve.
The cyclic deflection shall be gradually increased until the joint reaches failure. The type of failure
shall be recorded.
Table 13.8-1 – 𝑪 value and number of cycles for cyclical testing of frame bracing
connection
𝑪
0.25
0.50
0.75
1.00
1.30
1.60
2.00
2.50
3.00
3.50
4.50
6.00
8.00
10.0
0
Number
of
cycles
1
1
1
1
3
3
3
2
2
2
2
2
2
2
Evaluation of test results
The brace connection axial stiffness to be used for the cross-aisle frame analysis shall be taken
as the slope of a line drawn from the origin of the 𝐹 vs. 𝛥 graph to a point on the curve that does
not exceed a force value of:
𝐹𝑐𝑜𝑛𝑛 = 0.8𝜙𝐹𝑚𝑎𝑥
(13.8-3)
where
:
𝐹𝑐𝑜𝑛𝑛 is the brace connection force design strength capacity determined by cyclic testing;
𝜙
is the resistance factor for converting maximum force into design force (0.75);
𝐹𝑚𝑎𝑥 is the maximum force from the cyclic brace connection test performed in
accordance with the cyclic brace connection test procedure.
Alternatively, a higher value of stiffness (secant slope) is permitted if the final brace connection
force from the analysis does not exceed the corresponding point on the 𝐹 vs. 𝛥 curve.
When testing is used to establish the strength and stiffness of brace connections in accordance
with this section, the strength of the connections 𝐹𝑐𝑜𝑛𝑛 shall be greater than the required strength
for the connections.
Commentary to ANSI MH16.12021
Revision
of
Commentary
to
ANSI
MH16.1-2012(R2019)
Commentary for the Design, Testing, and Utilization of Industrial Steel
Storage Racks
An Industry Group of MHI 8720
Red Oak Blvd., Suite 201
Charlotte, NC 28217-3992
standards@mhi.org
© 2021 MHI
All rights reserved.
PREFACE TO THE COMMENTARY
Any structural design specification is the product of extensive research and development work
combined with accumulated engineering experience. Industrial steel storage racks differ in
many respects from more familiar types of structures, such as buildings and bridges. It follows
that the generally recognized principals and methods of design and testing of steel structures
must be, modified and supplemented for those features peculiar to rack structures. This can be
done adequately only by extensive analytical and experimental research on rack structures,
combined with engineering experience in this field.
It is important to bear in mind that the ANSI MH16.1-2021 Specification and the Commentary
should not be used without first obtaining competent engineering advice with respect to
suitability for any given application.
This commentary, like those in ANSI/AISI S100-16, North American Specification for the Design
of Cold- Formed Steel Structural Members and ANSI/AISC 360-16, Specification for Structural
Steel Buildings, attempt to serve two purposes:
a)
it gives explanations of, and reasons for, the various provisions of the Specification; and
b) where advisable, it suggests specific procedures regarding engineering design,
calculation, or testing, which satisfy the particular requirements of the specification.
It should be emphasized that, while the provisions of ANSI MH16.1-2021 are meant to be
explicit, recommendations and suggestions made in the commentary are not. In many cases,
they represent one way of interpreting ANSI MH16.1-2021 provisions, but do not preclude other
ways of doing so.
Published by
Rack Manufacturers Institute
An Industry Group of MHI
8720 Red Oak Blvd., Suite 201, Charlotte, NC, 28217-3992
Telephone: (704) 676-1190 Fax: (704) 676-1199
standards@mhi.org
© 2021 by MHI
All rights reserved.
No part of this publication may be reproduced in any form,
in an electronic retrieval system or otherwise, without prior
written permission of the publisher.
Table of Contents
C1 Purpose and scope ............................................................................... C-1
Purpose ..................................................................................................................................... C-1
Scope ........................................................................................................................................ C-1
C2 Normative references ......................................................... C-2
C3 Terms and definitions .................................................................... C-3
C4 Rack integrity, use, and maintenance .................................................... C-4
C4.1 Owner responsibilities ..................................................................... C-4
C4.2 Column base plates and anchors ...................................................................... C-4
C4.3 Post-installation inspection.......................................................................... C-4
C4.4 Repair or replacement of damaged storage rack systems or components ................. C-5
C4.5 Load plaque............................................................................................................. C-5
C4.6 Load application and rack configuration drawings .................................................... C-6
C4.7 Multiple configurations ................................................................................... C-7
C4.8 Movable shelf racks .............................................................................. C-7
C4.9 Small installations ............................................................................... C-7
C4.10 Racks connected to the building structure ........................................................... C-7
C4.11 Out-of-plumb and out-of-straight limits .............................................................. C-8
C4.11.1 Out-of-plumb limit ................................................................................ C-8
C4.11.2 Out-of-straight limit ......................................................................... C-8
C4.12 Modification of industrial steel storage rack systems .............................................. C-8
C5 Materials ....................................................................................................................... C-9
C6 Design procedures ......................................................................................... C-10
C7 Loading ......................................................................................................... C-11
C7.1 Loading design methods ....................................................................... C-11
C7.1.1 General .............................................................. C-11
C7.1.2 Load combinations for ASD method ............................... C-11
C7.1.3 Load factors and combinations for LRFD method ....................... C-12
C7.2. Design for stability .......................................................................... C-13
C7.2.1 General ........................................................................................ C-13
C7.2.2 Product load ........................................................................... C-13
C7.2.3 Second order effects ....................................................... C-13
C7.2.4 Notional loads ..................................................................... C-14
C7.2.5 Connector sway rotational stiffness and moment strength ............. C-14
C7.2.6 Column base stiffness and moment strength .......................... C-14
C7.2.7 Movable-shelf rack stability ............................................ C-15
C7.3 Wind loads .............................................................................. C-15
C7.4 Earthquake forces ......................................................................... C-15
C7.4.1 General .............................................................................. C-15
C7.4.2 Seismic design criteria ........................................................... C-16
C7.4.3 Redundancy factor .................................................................... C-17
C7.4.4 Site coefficients and adjusted maximum considered earthquake spectral
response acceleration parameters.................................................... C-17
C7.4.5 Design spectral response acceleration parameters .................... C-18
C7.4.6 Determination of the seismic response coefficient ....................... C-18
C7.4.7 Site class definitions .............................................. C-19
C7.4.8 Mapped acceleration parameters SS and S1 ......................... C-19
C7.4.9 Seismic design category ...................................... C-19
C7.4.10 Seismic displacement .............................................................. C-20
C7.4.11 Seismic separation ............................................................ C-20
C7.4.12 Vertical distribution of seismic forces ..................................... C-20
C7.4.13 Horizontal distribution of seismic load at a storage level ............. C-20
C7.4.14 Vertical impact loads ........................................ C-20
C7.4.15 Horizontal loads ................................................................... C-21
C7.7 Storage racks for automated storage and retrieval systems ........................ C-21
C7.8 Seismic overturning ................................................................................ C-21
C8 Design of steel elements and members .............................................. C-22
C8.1 General .................................................................................... C-22
C8.2 Perforated steel members ................................................................. C-22
C8.2.1 Section properties of cold-formed steel sections ........................... C-22
C8.2.2 Concentrically-loaded perforated compression members .............. C-22
C8.2.3 Perforated members bending about the centroidal axis perpendicular to
the axis of symmetry ........................................................................... C-25
C9 Beam design ...................................................................................... C-27
C9.1 Calculations .................................................................................. C-27
C9.2 Cross section.................................................................................. C-27
C9.3 Deflections .......................................................................... C-28
C9.4 Beam-to-column connections .............................................. C-28
C9.4.1 General ........................................................................... C-28
C9.4.2 Connection rotational demand ......................................... C-28
C9.4.3 Beam locking device .............................................................. C-30
C9.4.4 Movable-shelf racks ...................................................... C-30
C9.5 Pallet supports.................................................................. C-30
C9.6 Welded wire rack decking ......................................................... C-31
C10 Upright frame design ......
........................................................................... C-32
C10.1 Upright frames ................................................................................. C-32
C10.2 Column design .......................................................................... C-32
C10.2.1 Flexural buckling in the direction perpendicular to the upright frame
C10.2.2 Applicable column length for flexural buckling in the plane of the
upright frame ............ C-33
C10.2.3 Column length for torsional buckling .................................. C-35
C10.3 Frame bracing design .................................................................. C-36
C10.4 Frame tie design ................................................................... C-36
C10.4.1 General .................................................................... C-36
C10.4.2 Back-to-back ties (row spacers) ......................................... C-36
C10.4.3 Frame-to-column ties ............................................................ C-37
C10.4.4 Flue shear ties ............................................................................... C-37
C14.4.5 Cross-aisle ties ................................................. C-37
C11 Column base design ........................................................................................ C-38
C11.1 Column base plates ............................................................. C-38
C11.1.1 Bearing on concrete .............................................................. C-38
C11.1.2 Base plate design ......................................................................... C-38
C11.1.3 Column base plate connection rotational demand ....................... C-39
C11.2 Shims .......................................................................... C-40
C11.3 Anchorage ....................................................... C-40
C11.3.1 Anchor bolt design................................................... C-40
C11.3.2 Overstrength design for anchor bolts ........................................... C-41
C11.3.3 Periodic inspection of anchor bolt installation ............................ C-41
C11.4 Slabs and subgrade evaluation ......................................... C-42
C12 Special rack design provisions.............................................................................. C-43
C12.1 Overturning ................................................................... C-43
C12.2 Interaction with buildings ..................................................... C-43
C12.3 Pick modules and rack supported platforms ............................................. C-43
C12.3.1 General ................................................................................ C-43
C12.3.2 Design requirements ........................................................... C-44
C12.3.3 Posting of design loads .......................................................... C-44
C12.3.4 Safety flooring ................................................................ C-44
C12.3.5 Stairs, ladders, and guards ......................................... C-45
C12.3.6 Kick plates (toeboards) ................................................. C-45
C12.3.7 Conveyor floor openings ..................................................... C-45
C12.3.8 Product fall protection ...................................................... C-45
C12.4 Storage racks for automated storage and retrieval systems .................. C-45
C13 Testing .................................................................................................. C-46
C13.1 Test methods............................................................................................. C-46
C13.2 Stub column tests for cold-formed and hot-rolled columns ................. C-46
C13.2.1 Purpose ............................................................................ C-46
C13.2.2 Test specimen and procedure ................................................ C-46
C13.2.3 Evaluation of test results ....................................................... C-46
C13.3 Pallet beam tests ................................................................. C-46
C13.3.1 Purpose ....................................................................................... C-46
C13.3.2 Simply-supported pallet beam tests ........................................................ C-46
C13.3.3 Pallet beam in upright frames assembly tests ........................................ C-47
C13.4 The cantilever test ...................................................... C-48
C13.5 Cyclic testing of beam-to-column connections ......................................... C-48
C13.5.1 Purpose ................................................................ C-48
C13.5.2 Test specimen ................................................................. C-49
C13.5.3 Test setup ......................................................................... C-49
C13.5.4 Test procedure ........................................................................ C-49
C13.5.5 Evaluation of test results .................................................. C-49
C13.6 Column base fixity testing ................................................................. C-49
C13.6.1 Purpose .................................................................................... C-49
C13.6.2 Definitions ................................................................................... C-49
C13.6.3 Precision ...................................................................................... C-50
C13.6.4 Test specimen fixture and setup ........................................................... C-50
C13.6.5 Test procedure ............................................................................... C-51
C13.6.6 Evaluation of test results .................................................................. C-51
C13.7 Static testing of frame bracing connections ......................................... C-51
C13.8 Cyclical testing of upright frame bracing connection................................... C-55
Figures
Figure C4.5-1 – Example of a load capacity and compliance plaque for palletized loads
Figure C4.5-2 – Example of a load capacity and compliance plaque for distributed loads
Figure C4.11-1 – Examples of out-of-straight limits
Figure C7.4-1 – Seismic design categories
Figure C8.2-1 – An open section that could be subject to distortional buckling
Figure C8.2-2 – Examples of sections that could be subject to distortional buckling
Figure C8.2-3 – Finite element models for correlation with finite strip models (FSM) and physical
tests
Figure C8.2-4 – Tested specimens demonstrating distortional buckling
Figure C8.2-5 – CUFSM analysis result (axial load vs. length of the section) shown in
Figure C8.2-3 and Figure C8.2-4
Figure C8.2-6 – Reduced thickness strips
Figure C8.2-7 – FEM model demonstrating distortional buckling under bending
Figure C9.5-1 – Examples of pallet storage positions
Figure C10.2-1 – Plan and back bracing
Figure C10.2-2 – Racks braced against sidesway
Figure C10.2-3 – Braced and unbraced frames
Figure C10.2-4 – Frames with diagonal braces that intersect the columns
Figure C10.2-5 – Upright frames with diagonal braces that intersect the horizontal braces
Figure C10.2-6 – Joint details
Figure C11.1-1 – Visual representation of dimensions for 𝒎, 𝒑, and 𝒂
Figure C13.6-1 – Photo of column base fixity test setup
Figure C13.6-2 – Photo of column base fixity test setup
Figure C13.7-1 – Front and cross section views of a short upright frame
Figure C13.7-2 – Diagonal brace test setup
Figure C13.7-3 – Diagonal brace test setup
Figure C13.7-4 – Horizontal brace test setup
Figure C13.7-5 – Horizontal brace test setup
Figure C13.7-6 – Spherical joint pin for rotation capacity around the three axes shown
Commentary for the Design, Testing and Utilization of Industrial Steel Storage Racks
C1
Purpose and scope
Purpose
The specification is intended to be referenced by registered design professionals who have a
basic understanding of the unique characteristics and behavior of industrial steel storage racks.
The commentary is a companion to the specification and includes informative insight and
technical information. The reader is encouraged to refer to this commentary for such
information.
Scope
The scope limits the applicability of ANSI MH16.1-2021 to pallet racks, movable shelf racks,
rack supported structures and stacker racks made of hot-rolled or cold-formed steel. Although
only these types of rack are explicitly mentioned, ANSI MH16.1-2021 is also intended to be
applied to any freestanding rack having a three-dimensional structural system comprised of
braced frames in one direction and moment frames in the other—in other words, any rack
system that is constructed with beams and frames. Such rack types include, but are not limited
to, push back rack, pallet flow rack, case flow rack, and pick modules. ANSI MH16.1-2021 is
also intended to be applied to the design of the storage rack portion of rack supported
structures.
The rack systems that are excluded from ANSI MH16.1-2021 (such as cantilever and drive-in)
are excluded for the following reasons:

Guidance for cantilever rack can be found in ANSI MH16.3, Specification for the Design,
Testing, and Utilization of Industrial Steel Cantilever Storage Racks;

Several provisions included in ANSI MH16.1-2021, such as the beam design and upright
frame and effective length provisions in Sections 9 and 10, respectively do not apply to
these rack types; and

ANSI MH16.1-2021 does not include the necessary design provisions for these rack
types. For example, effective length factors and deflection limits for cantilever uprights
would need to be included. Some of the design testing requirements in ANSI MH16.12021, such as the design of steel elements and members in Section 8, would be
applicable to any hot-rolled or cold-formed steel column of other rack types.
This standard does not specify specific design or capacity ratings for ancillary items used in
conjunction with racking systems. Unless noted otherwise, such items include, but are not
limited to:

conveyor systems;

push-back lanes;

pallet-flow lanes;

carton-flow lanes;

metal shelf and floor decking; or

engineered-wood shelf and floor decking.
C2
Normative references
The following standards and documents do not constitute provisions of this American National
Standard but can contain provisions that could be useful or relevant to the design, testing, and
utilization of industrial steel storage racks.
AISI D100-17, Cold-Formed Steel Design Manual
AISC 325, Steel Construction Manual, 15th Edition, 2017
ANSI MH16.3-2016, Specification for the Design, Testing, and Utilization of Industrial Steel
Cantilevered Storage Racks
ATC-19, Structural Response Modification Factors, Applied Technology
Council, 1995 ATC-24, Guidelines for Cyclic Seismic Testing of Components of
Steel Structures, 1992
California Office of Statewide Health Planning and Development, Seismic Design Maps:
https://seismicmaps.org/
FEMA-350, Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings, June
2000
FEMA 460, Seismic Considerations for Steel Storage Racks in Areas Accessible to the Public,
September 2005
FEMA P-1050-1/2015 Edition, NEHRP Recommended Seismic Provisions for New Buildings and
Other Structures, Federal Emergency Management Agency
FEMA P-750/2009 Edition, NEHRP Recommended Seismic Provisions, Building Seismic Safety
Council SAE J429-2014, Mechanical and Material Requirements for Externally Threaded
Fasteners
SEAOC Blue Book, Seismic Design Recommendations, 2019
Rack Manufacturers Institute, Guidelines for the Assessment and Repair of Replacement of
Damaged Rack
Rack Manufacturers Institute, Considerations for the Planning and Use of Industrial Steel Storage
Racks
C3
Terms and definitions
No commentary provided.
C4
Rack integrity, use, and maintenance
Owner responsibilities
This section stresses the importance of planning in the initial design process, controlling the use
of the rack to that initially intended, and scheduling regular inspection to maintain the integrity of
rack structures. The RMI document, Considerations for the Planning and Use of Industrial Steel
Storage Racks provides more information on this subject. This document can be obtained at
https://www.mhi.org/rmi. Additionally, FEMA 460 provides additional guidance on proper
operation and maintenance of racks installed in areas accessible to the public.
Column base plates and anchors
Base plates receive the concentrated forces and moments at the bottom of the columns and
distribute those forces across the concrete floor. Guidance for designing and dimensioning of
column base plates on concrete floors is provided in Section 11. Adequate connection of the
column to the base plate is required to properly transfer the forces.
This section also specifies that all rack columns shall be anchored to the floor. Anchors serve
several distinct functions:

Anchors fix the relative positions of, and distances between, neighboring columns.

Anchors provide resistance against horizontal displacements of the bottom of the
columns. A tendency for such horizontal displacement can result from external lateral
forces (earthquake, wind, impact, etc.) or from the horizontal reactions (shear forces)
resulting from the rigid or semi- rigid frame action of the rack. If such shear forces
caused horizontal displacements of the bottoms of the columns, this would reduce the
carrying capacity as compared to computed values.

For particularly tall and narrow racks, anchors can significantly increase the stability
against overturning (see C12.1).
Base plates commonly have several pre-drilled holes in them to accept anchors, though it is not
always necessary to install an anchor in each anchor hole. Refer to the LARC drawings for
anchorage requirements.
ANSI MH16.1-2021 allows an exception to the requirement to anchor small, hand-loaded
storage rack systems that meet the conditions given in this section, and as approved by the
registered design professional. Small storage racks are often used in environments where the
user intends to be able to periodically move the storage racks to different locations in their
facility. The height-to-depth ratio of small storage racks typically make small storage rack
systems stable with respect to overturning. When storage racks are unanchored, the
specification prohibits double-stacking on the top storage level and limits loading to handloading applications to avoid overturning, or the possibility of material handling equipment
impacting or damaging the storage rack columns.
Post-installation inspection
Users of rack systems should ensure that a post-installation inspection of the rack is performed
by competent personnel. The inspector should be provided with updated LARC drawings and
product load details. The inspection should identify and address the following:
a)
discrepancies between the rack layout and LARC drawings;
b) structural damage;
c)
torque on fasteners; and
d) missing, modified, or out-of-position components.
Repair or replacement of damaged storage rack systems or components
Collisions of forklifts or other moving equipment with front columns of storage rack systems are
the most common source of structural distress of storage racks.
This section is concerned with the protection of the bottom portions of columns exposed to such
potential collisions. The height from the ground surface at which such collisions can occur
depends on the configuration of the vehicle. Damage to the storage rack columns is typically
confined to below the first level of beams. When the lowest beam is located a nominal
distance, for example, 24 to 48 in. (61 to 122 cm) from the floor, the rear counterweight of some
trucks can impact the beam, imposing a substantial horizontal load on the beam or frame
bracing. In such cases, impact protection designed to withstand such contact should be
considered.
While it is not practical to design racks to resist the maximum possible impact of storage
equipment, this section addresses two possible methods to safeguard storage racks against the
consequences of minor collisions:
a)
The first method involves the installation of guards, barriers, or other protective devices
designed to prevent trucks from contacting the exposed columns. Fenders or bumpers
can and have been used for this purpose. Also, deflectors which, while not designed to
withstand the full impact of the truck, are shaped to deflect it away from collision with
the columns. No specific requirements for force resistance are provided. The potential
forces will depend on the vehicle characteristics, such as mass, velocity, or bumpers.
These protective devices can be designed to lose their integrity or effectiveness after
impacts, thus requiring replacement. Therefore, such devices should be made to be
easily replaceable or repairable in case of collision damage.
b) The second method involves the installation of guards, bumpers, deflectors, or
reinforcements on the bottom portion of the front column or bracing in the frame, where
contact is most likely to occur. Common methods include welding an angle deflector to
the front of the aisle side column, doubling the section strength by welding two columns
together, using heavier horizontal and diagonal bracing to provide alternate load paths,
or using larger base plates and anchors with the aisle side column.
These methods are intended to aid in avoiding collapse of the frame due to minor impacts (not
major collisions) and limiting the damage caused. Regardless of the presence or absence of
safeguards, regular inspections are also required to identify damage, remove damaged rack
from service, and make necessary repairs. RMI has developed a document entitled, “Guideline
for the Assessment and Repair or Replacement of Damaged Rack” that provides more
information on this topic. This document can be obtained at https://www.mhi.org/rmi.
Load plaque
In industrial and commercial warehouses, allowable floor loads are generally posted in readily
visible locations, and such postings are often required by law. ANSI MH16.1-2021 provides for
similar posting of maximum permissible unit load for each given rack installation. A sample
plaque is illustrated in Figure C4.5-1 and Figure C4.5-2. For racks designed to receive loads on
standard sized pallets, a unit load means the combined weight of product and pallet unless the
installation provides for more than one unit load being stacked on top of each other. Load
beams can be separately identified. The figures are not intended to limit the plaque details, but
rather are presented as possible examples. Any plaque that provides the required information is
acceptable.
Figure C4.5-1 – Example of a load capacity and compliance plaque for palletized loads
Figure C4.5-2 – Example of a load capacity and compliance plaque for distributed loads
The unit load is usually shown as a single pallet or container and its contents that are added or
removed from the storage rack with a fork truck or other mechanical means.
The plaques should not be transferred to any reconfigured or relocated rack without first
verifying the applicability of the information on the plaque to the new configuration or location.
In addition to load plaques, manufacturers are recommended to include a permanent
identification mark on their beam and frame components so that the components can be traced
back to the manufacturer. The identification marks can consist of embossed or engraved
identification or applied to a label affixed to the component for components that cannot be
readily embossed or engraved.
Load application and rack configuration drawings
Complete engineering data should be available on the design and capacity of the racks as
originally ordered, delivered, and installed, so this information could be used for future
reference, safety inspections, repairs, or proposed modifications.
This section requires LARC drawings be furnished by the rack dealer or manufacturer’s
representative involved in procuring and erecting the rack installation. The LARC drawings are
required to include the load magnitude and applications.
LARC drawings should be maintained by the owner and the dealer because either party could
change over the lifetime of the installation. The maintenance of LARC drawings by both parties
will increase the probability that the drawings will be available for future reference.
Multiple configurations
Most storage rack systems are produced to be adjustable and potentially reassembled in
configurations different from the one originally ordered and installed. Consequently, it is possible
to install or modify a rack into an unsafe alternate configuration. For example, while using the
original components (beams and upright frames), the rack could be rearranged to increase the
vertical distance between the lower beams, which would increase the unbraced length of the
columns. Its increased slenderness ratio would reduce the carrying capacity of the columns, as
compared to the original configuration. Alternately, storage rack systems can be modified by
installation of additional components; e.g., greater number of shelf beams at smaller vertical
spacing with the original upright frames. This would reduce the slenderness ratios of the
individual column segments and increase their load capacities. However, the additional loads,
which can now be placed on the greater number of shelves, could increase the load on the
column by an amount greater than the increased capacity resulting from the reduction of the
unbraced length. These are just two examples of changed configurations which could make an
originally adequate rack unsafe.
The owner or user of the rack installations typically lacks the engineering expertise to establish
the safe load capacity of the modified rack configuration.
It is for these reasons that this section provides that the owner is provided with multiple
configuration guidance for storage rack systems where multiple configurations can be
assembled. If changes other than those detailed in the guidelines need to be made, the original
manufacturer or a registered design professional should be contacted.
Movable shelf racks
Movable shelf racks differ from standard storage racking in that most shelves in movable shelf
racks are designed to be removed. In standard storage racks, shelves (beams) are readily
adjustable, but cannot be removed without unloading the rack and re-assembling the
components. In contrast, movable shelf racks are fitted with one or more permanent shelves
and/or braces that provide the needed stability to the structure. This section specifies the
provisions for identifying those stabilizing components, and for posting warnings and
restrictions for removal.
The movable shelves are constructed with a set of front and rear longitudinal beams connected
rigidly to each other by transverse members. The movable shelves are connected to prevent
forward displacement when lifting out the front beam of the shelf.
The upward load is specified to prevent accidental disengagement of the beam connection. The
upward force should be applied to an unloaded beam. Since this load is compared to the
connection locking device failure, there is no load factoring required.
Small installations
This section offers an exemption for small rack installations from LARC drawing (C4.6) and
multiple configuration (C4.7) requirements. However, in all other respects, the design, testing
and utilization provisions of ANSI MH16.1-2021 apply to all storage racks, including the small
installations as defined in this section.
Even though storage rack from 8 ft to 12 ft (2.4 to 3.6 m) in height generally require seismic
design, they are still considered to be small installations if they otherwise meet the criteria in this
section.
Racks connected to the building structure
It is common practice to connect certain storage racks, such as single-row racks adjacent to a
wall, to the building structure for added stability. It is important, particularly in seismic
applications, to consider the forces that can be applied to each of the structures, as well as
considering the structural interactions due to those forces. This section requires that the
registered design professional advise the building owner of the possible forces imposed by the
rack so that the building architect or engineer can be notified.
The force transfer between any two structures is dependent on their relative movement and
stiffness. Absent detailed knowledge of the other structure, it is generally not possible to
compute the rack force being transferred. In such cases, the registered design professional can
provide forces assuming that the adjacent structure is infinitely stiff. The registered design
professional should also consider situations where the adjacent structure transfers load to the
rack.
Out-of-plumb and out-of-straight limits
The purpose of out-of-plumb and out-of-straight limits is to minimize the axial load eccentricity.
An out-of- plumb or out-of-straight condition will cause axial load eccentricity that will reduce the
load carrying capacity of a rack column. The reduction can be significant. A storage rack that
is out-of-plumb from top to bottom, or a rack column that is not straight, is likely to become
further out-of-plumb or out-of-straight when it is loaded. The limits on out-of-plumb and out-ofstraight that are given in C4.11.1 and C4.11.2 are for loaded racks. They are provided so the
user knows when their racks might need to be re-plumbed and possibly repaired. If an empty
rack exceeds these limits, it should be corrected prior to loading. Some installations, such as a
storage rack that is loaded and unloaded by an automated guided vehicle (AGV) or
autonomous mobile robot (AMR), could require tighter limits.
Out-of-plumb limit
The limit given for top to bottom out-of-plumb is for a loaded rack and is not intended to be an
installation tolerance. The installer should obtain the installation tolerances from the rack
supplier prior to the start of an installation. These tolerances should be such that the loading of
the racks will not cause the racks to exceed the out-of-plumb limit. This limit is intended to
prevent the use of racks that have a down aisle or a cross aisle lean.
Out-of-straight limit
The out-of-straight limit is given to prevent excessive “bows,” “kinks,” or “dogleg” conditions that
can exist in a rack column. A column could be plumb from top to bottom but have an
unacceptable bow at mid- height (see Figure C4.11-1 (a)), or a 20 ft (6 m) high column
could be out 1 in. (25 mm) from top to bottom. Such a column would be acceptable using a
simple top-to-bottom out-of-plumb measurement, but the entire out-of-plumb could be between
the floor and the 5 ft (1.5 m) level (see Figure C4.11-1 (b)). This condition could be caused by
forklift impact and could negatively affect the storage rack’s load capacity. The column could
have a sine wave shape and be out-of-straight as shown in Figure C4.11-1 (c). The column
could also be locally bent and exceed this limit, see Figure C4.11-1 (d). ANSI MH16.1-2021
deems these situations to be unacceptable if they exceed the 1/240 out-of-straight limit.
Figure C4.11-1 – Examples of out-of-straight
limits Modification of industrial steel storage rack systems
No commentary provided.
C5
Materials
ANSI MH16.1-2021 supplements or modifies ANSI/AISI S100 and ANSI/AISC 360.
The fastener requirement was added in this edition of the specification given SAE hardware is
typically used in rack applications and is an acceptable alternative to hardware that complies
with ASTM standards.
C6
Design procedures
This section specifies that engineering design calculations are to be made in accordance with
accepted principals and conventional methods of structural design. This means among other
things, that the basic concepts of structural analysis must be observed. This section also refers
to ANSI/AISI S100 and ANSI/AISC 360 as modified in various specifics in the specification.
This edition of ANSI MH16.1-2021 allows the use of either Allowable Strength Design (ASD) or
Load Resistance Factor Design (LRFD) for rack design.
The following is an example of what is meant by “conventional methods of structural methods of
structural design.” Depending on types of connections, cross sections and relative capacities of
beams and columns, pallet racks can function and be analyzed either as elastic rigid frames or
as frames with semi- rigid connections. Regardless of what methods are used, the basic laws of
equilibrium and compatibility need to be satisfied in all parts of the structure. For example, in the
design of shelf beams, advantage can be taken of negative end moments up to values that can
be developed by the specific connections, as determined by test (Section 9.4). However, if this
is done, the column needs to be designed for the end moments which they must develop in
order to create the end restraint used in the beam design. For instance, the upper end of a
corner column has to support the full end moment of the abutting uppermost shelf beam, and
the column must be designed for its axial load plus indicated moment. Unless this is done, the
basic law of equilibrium has been violated. The same holds true at all other beam and column
joints, except that the unbalanced end moment of two adjacent beams, is jointly resisted by both
columns framing in to that joint and possibly also by the unloaded beam if its connection can
resist an appropriate moment. This is because the negative beam moments can be
calculated on the basis of conventional rigid frame analysis, or on the basis of semi-rigid
analysis (i.e., using test values of connection capacities). By the simple law of equilibrium, no
negative moment can act on the end of a beam unless the abutting members can develop this
moment and are designed for it.
There could be situations in rack structures for which adequate design methods do not exist.
This is the case where configurations of sections are used which cannot be calculated by
established methods, where connections of a non-standard character are employed, etc. In
these cases, design calculations of member and connection capacity are replaced by
appropriate tests. Several tests, specific to storage racks construction, are specified in Section
13. Tests not specified are to be conducted according to the general test procedure
requirements of ANSI/AISI S100.
Tests are not to be used in lieu of design calculations, except in those situations which cannot
be calculated by available methods. ANSI/AISI S100 Section K is specific about this. It should
be noted that confirmatory tests have a different nature and are covered in ANSI/AISI S100.
Where tests are not specified in the specification or ANSI/AISI S100 for cold-formed members,
the procedures in the IBC Section 1714 and Section 1715 are to be used.
No slenderness limitations are imposed on tension members. However, the slenderness ratio of
compression members preferably should not exceed 200. The ANSI/AISI S100 limitations
themselves are not mandatory but are instead suggested as good practice.
C7
Loading
Loading design
methods General
The purpose of this section is to clarify the design methods used in ANSI/AISI S100 and
ANSI/AISC 360 as they apply to storage racks and to show how ASCE/SEI 7 load combinations
should be applied to storage racks. Storage racks differ from building structures in that their
dead loads are a very small percentage of the total load when compared to buildings. Also,
storage racks have product loads in addition to dead load and possibly live load. Product load
has been defined for racks as the products or pallet loads stored in the rack. This load is given
the symbol, 𝑃, in the load combinations. Live loads could still be present in racks. Examples of
live loads include loading on a work platform or moving equipment loads discussed in 12.5.
The product load, 𝑃, is considered to be between a dead load and a live load. Therefore, for
gravity load combinations, the LRFD product load factor is 1.4, which is the average of the
ASCE/SEI 7 LFRD dead load factor of 1.2 and live load factor of 1.6. Similarly, for snow/rain or
roof live load and wind load LFRD load combinations, the factor applied to product loads is the
average of the ASCE/SEI 7 LFRD dead load factor of 1.2 and the live load factor of 0.5. For
seismic loads, a 𝛽 factor of 0.7 is applied to the product load for non-uplift conditions. The 0.7
value was determined as the average between dead and live load LRFD factors. However, for
seismic loads, the 0.7 𝛽 factor is needed to result in loading conditions that were slightly
conservative. For seismic uplift conditions, a 𝛽 factor of 1.0 is specified because the product
load needs to be present in order to obtain the seismic force associated with lift conditions. The
additional product load terms 𝑃𝑎𝑝𝑝𝑊 and 𝑃𝑎𝑝𝑝𝑆 are also defined for both wind and seismic
uplift conditions based upon the percentage of pallet load present that would result in the
maximum uplift forces, determined by engineering best judgment. For storage racks exposed to
wind forces, this could require an assumption of a full-size unit load that is a fraction of the
weight of a maximum unit load. Note that the design wind and the dead load portion of the
product load resisting overturning are directly proportional to the height of the loads stored in the
rack. Additionally, for outdoor racks or rack structures with cladding, 𝑃𝑎𝑝𝑝𝑊 is zero for the wind
uplift case because the racks could be required to resist the full wind force when they are
empty.
The load combinations have been written to align with the load combinations from ASCE/SEI 7
as they apply to storage racks with the addition of the product load (𝑃) added to each
combination. Roof live load (𝐿𝑟) for rack-supported structures was first included in ANSI
MH16.1-2002. In ANSI MH16.1-2012, the 𝛽 factor was introduced to provide more consistent
treatment of vertical seismic forces from product load.
LRFD design has become common for cold-formed and structural steel installations. Both
ANSI/AISI S100 and ANSI/AISC 360 have incorporated LRFD and ASD. Either method is
equally acceptable, and the methods should give similar results, though they will likely not be
the same. Additionally, the critical load combination or load placement for one member or
connection will likely not be the same for another member or connection. ANSI MH16.1-2021
requires designs to be conducted in accordance with either LRFD or ASD. There could be
advantages to designing using the LRFD method due to the product load factor that has been
incorporated in the LRFD load combinations.
In addition to the vertical load, ANSI MH16.1-2021 includes provisions for vertical impact and
horizontal loads that a normal rack installation will experience during its use. It is important to
include all loads that could reasonably act together, and refrain from combining loads that are
unlikely to act together.
EXAMPLE – It is unlikely that a forklift would place a load on a rack during an
earthquake, so it is not necessary to combine shelf impact and earthquake loading.
Load combinations for ASD method
The ASD design method uses mostly unfactored applied loads and then compares them with
nominal strengths divided by factors of safety. The 0.88 value applied to the shelf plus impact in
ASD load combination #11 is considered the critical load case because impact is a shortduration load and for the two-pallet case where the impact effects are not large, the beam
design will result in the traditional factor of safety of 1.65 to 1. ASD load combination #11
provides a more realistic treatment of impact loading for shelves. See further explanation in
C7.1.3. Other load factors that appear in the ASD method are due to
changes in the ASCE/SEI 7 combinations. All loads resulting from these combinations need to
be checked against nominal strengths from either ANSI/AISC 360 or ANSI/AISI S100 divided by
the appropriate Ω (safety factors) given therein.
The 𝑃𝑎𝑝𝑝𝑊 load represents the product loading that must be present for the wind load to be
possible during wind uplift conditions. The 𝑃𝑎𝑝𝑝𝑆 load represents the product loading that must
be present for the seismic load to be possible during seismic uplift conditions. For seismic
evaluations, it is recommended that this be the percent of the product load assumed to be
present that was used to compute the base shear for the seismic analysis. For outdoor racks or
rack structures with cladding, 𝑃𝑎𝑝𝑝𝑊 is zero for the wind uplift case because the racks could be
required to resist the full wind force when they are empty.
ASD load combination #11 exists to give a more realistic treatment of impact loading for
shelves. See further explanation in C7.1.3.
Load factors and combinations for LRFD method
As stated above, product loads are the loads that are placed on storage racks. Product load has
been differentiated from live load so it can be factored differently. It is necessary to differentiate
between these two types of loading because their treatment under seismic conditions is also
different. The load combinations have been written to align with the load combinations from
ASCE/SEI 7 as they apply to storage racks with the addition of the product load added to each
combination. The maximum product load is generally well known for a typical installation and
more predictable because the weight and density of the product to be stored is known. The
potential for overload can also be reduced due to the lifting limitations of the forklift. For this
reason, a smaller load factor than that used for a live load is justified. However, the probability of
a high product load being present during an earthquake is greater than the probability of a high
live load being present, so for some of the loading combinations, the product load factor is
higher.
The purpose of these modifications is to make the load combinations more realistic for the rack
structures. These loads are to be compared with the nominal strength for the member or
connection, multiplied by the appropriate resistance factor from ANSI/AISC 360 or ANSI/AISI
S100. The load factors and combinations have been updated to reflect similar changes made in
ASCE/SEI 7.
Product load has been added to the uplift case because, for racks, the product loads need to be
present for the prescribed seismic forces to act. It is possible to get an irregular loading that will
produce seismic uplift on an unloaded column for an interconnected section of rack. The
unloaded frames, in this case, would be tied to frames with pallet loading that would resist uplift.
The seismic forces would then be less for the under-loaded areas. The product load not used to
compute 𝑊 is still present and resisting uplift.
The modification of the LRFD approach is a reduced load factor of 1.4 for product loads. As
mentioned above, this is justified due to better predictability of product loads than live loads.
This applies to product loading only and does not apply to other live loading from roof,
mezzanines, etc. The load factors for all the combinations were derived by averaging the 𝐿
factor and the 𝐷 factor. This results in a safety factor of
1.65 for the gravity load case for the entire range of column lengths with respect to product
loading. The resistance factor (𝜙) for compression members is 0.85 for cold-formed structural
steel and 0.9 for hot- rolled structural steel.
LRFD load combination #8 provides a more realistic treatment of impact loading for shelves.
This combination will usually govern the design of the shelf. For a two-pallet wide shelf, which
is most common, the impact effect is about 1/8 of the beam load, so the margin of safety for this
combination (with the 𝐷 equal to 1 percent of the product load) would be:
For 𝜙 = 0.95
(1.2 × 0.01 × 𝑃) + (1.4 × 𝑃) + (1.4 × [0.125 × 𝑃]) = 1.587𝑃
This corresponds to the traditional 1.67 factor of safety:
1.587⁄ = 1.587⁄
0.95 = 1.67
𝜙
A resistance factor (𝜙𝑏) of 0.9 would result in a higher factor of safety. This load combination
would govern over combination #2 because combination #2 includes no impact loading. For
ASD, combination #2 could govern on a shelf with many loads applied, for example a shelf with
50 hand-stacked boxes. Combination #8 will always govern for LRFD.
Design for
stability General
Previous editions of ANSI MH16.1 allowed racks to be designed using the effective length
method and allowed the use of 𝐾 = 1.7 to provide the racks with some degree of restraint
against story buckling. Using 𝐾𝑥 = 1.7 assumes a story stiffness rather than analyzing the
actual story stiffness. Both ANSI/AISC 360 and ANSI/AISI S100 now require second order
analysis for typical storage rack stiffness with few exceptions.
This edition of ANSI MH16.1 requires use of the methods in ANSI/AISC 360 and ANSI/AISI
S100 with some modifications and clarifications to make these methods applicable to storage
racks.
The stability of a down-aisle frame-beam type pallet rack is maintained by the stiffness of
perforated columns, the stiffness of the beams, the stiffness of the semi-rigid column to base
connections, and the stiffness of the semi-rigid beam to column connections. The semi-rigid
nature of the connections and the base needs to be included in the model. The local-global
properties of the perforated columns from Section 8.2 are to be used. All further stiffness
reductions requirements in ANSI/AISC 360 and ANSI/AISI S100 are to be used.
Product load
This section provides guidance as to when 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 could be used rather than 𝑃𝑚𝑎𝑥 . 𝑃𝑚𝑎𝑥 is
to be used for each individual column design.
Use of 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is permitted for system stability effects only. System stability effects include the
calculation of the notional loads and the 𝑃 value in the 𝑃𝛥 magnification term (𝐵2 term) in 7.2.3.
The 𝑃 value for 𝑃𝛿 needs to be 𝑃𝑚𝑎𝑥 because 𝑃𝛿 is not a system stability effect.
Where 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is used, the average load needs to be indicated on the contract documents,
the load plaques, rack calculations and the LARC drawings. ANSI MH16.1-2021 limits
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 to no less than 67% of 𝑃𝑚𝑎𝑥 .
For braced systems where 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is permitted, the bracing can be designed based on
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 . An example of a braced system that would allow the bracing to be designed for
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is an ASRS system stabilized by down-aisle X bracing with four or more brace
towers. An example of a braced system where ANSI MH16.1-2021 does not allow the bracing to
be designed for 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is the frame bracing in a back- to-back row of pallet rack.
Second order effects
Many computer programs will compute all the second order effects required as part of the
analysis. Other programs might not. ANSI/AISC 360 provides guidance on how to determine if a
program adequately considers both the 𝑃𝛥 and the 𝑃𝛿 effects. It also allows design to be done
by computing the primary moments and drifts and magnifying these moments to include the
second order effects. The 𝐵2 magnification term given will conservatively magnify the primary
moments. This term is conservative because the 𝑅𝑚 value used in the equation to account for
the 𝑃𝛿 moments can overestimate the effect of
𝑃𝛿 moments. In most cases, the moments obtained from a program that properly computes second
order
effects will give results that are less conservative. In lieu of using 𝑅𝑚, the added moment from
the 𝑃𝛿
effect can be found by direct calculation added to the 𝑃𝛥 moments to get the total required moment
or the
𝐵2 magnification term calculated using 𝑅𝑚 = 1.0 can be increased to include the effects of the 𝑃𝛿
column moment from the member deformation.
When a computer analysis is used that computes all second order effects and 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is
used in the model for 𝑃𝛥, the 𝑃𝛥 effects will be correct but the 𝑃𝛿 effects, which utilize 𝑃𝑚𝑎𝑥 ,
will be incorrect and unconservative. If 𝑃𝑚𝑎𝑥 is used in the model for 𝑃𝛥 and there is a lesser
𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 , then both the 𝑃𝛥 and 𝑃𝛿
effects will be conservative.
Registered design professionals are advised to impose a limit to the value of 𝐵2. The point at
which additional small displacements can lead to large moment magnifications and potential
instability is generally between a 𝐵2 value of 2.5 and 5.0. The upper end of this range should
only be used if the registered design professional is computing the connection and base
stiffness determined using the slope from the origin to 80% of the maximum connector rotation
in the down-aisle direction. A lesser rotation can be used when evaluating the cross-aisle
seismic condition. See 7.2.5 and 7.2.6 in the specification. If rational analysis methods are used
to compute higher stiffness values for the connector and base stiffness, maximum 𝐵2 values at
the lower end of this range should be used. Refer to ANSI/AISC 360 and ANSI/AISI S100 for
more discussion on stability analysis.
Notional loads
The notional load coefficient of 0.004 is the out-of-plumb limit of the rack rounded to three
decimal places (1/240 = 0.00416̅ ). Using this ratio is equivalent to designing the rack with an
L/240 loaded lean. The notional loads are required to account for global imperfections of the
structure. These notional loads need to be added to other horizontal loads such as wind or
seismic. Since the notional loads are a system effect, the average load can be used to calculate
the notional load.
The notional loads are to be applied in the directions of least stability. For example, for the
down-aisle seismic analysis the notional loads are added to the horizontal loads. For the crossaisle seismic where buckling is in the down-aisle direction, the notional loads are still applied
down aisle since buckling is down-aisle.
A major difference between the notional load method and the effective length method is that
with the notional load method, stability is accounted for by the addition of the 𝑃𝛥 and 𝑃𝛿
moments, so the increase in the 𝐾𝑥 term that was required when the effective length method
was used is no longer necessary.
𝐾𝑥 = 1.0 can be used to determine the design axial strength of the column.
Connector sway rotational stiffness and moment strength
The down-aisle story stiffness and strength are highly dependent on the rotational stiffness
and strength of the beam end connection for unbraced framing. The cyclic tests of the
connectors usually show that the 𝑀 vs. 𝜃 curve for the connector is non-linear. This procedure is
a conservative simplification that permits the use of a linear spring constant for moment-rotation
data that is quite nonlinear. This linear spring constant and design moment can be used for the
stability analysis.
The specification also recognizes that at lower moment levels a correspondingly higher spring
stiffness can be used. The final moments from the stability analysis should be checked to
ensure that the design strength of the connectors is not exceeded.
Column base stiffness and moment strength
The down-aisle story stiffness and strength are also dependent on the rotational stiffness and
strength of the column base connection for unbraced framing. The RMI has tested three
commonly used base details and information on their behavior is available 1. The tests of the
bases show that the 𝑀 vs. 𝜃 curve for the column base connection is non-linear. This procedure
is a conservative simplification that permits the use of a linear spring constant for momentrotation data that is quite nonlinear. This linear spring constant and design moment can be used
for the stability analysis. The specification also recognizes that at lower moment levels, a
correspondingly higher spring stiffness can be used. In the absence of specific test data for the
base plate being analyzed, rational analysis can be used to determine approximate stiffness
and moment capacity values for the base plate connection.
For narrow base plates that are often used in lower seismic risk area, when the base axial load
eccentricity exceeds half of the column width, the base can suddenly lose the ability to take
more moment. If the base moment becomes high enough for this to occur, a wider baseplate
and additional anchorage would be needed, or the analysis will have to be changed to ensure
stability with the lower base moment. If the design moment for the base calculated in this
section is not exceeded, the base would be adequate. ANSI MH16.1-2021 allows for the use of
a correspondingly higher spring stiffness at lower moment levels.
Movable-shelf rack stability
Movable-shelf racks differ from conventional storage racks in that a majority of shelves are
designed to be removed. In conventional storage racks, shelves (beams) are readily adjustable,
but cannot be removed without unloading the rack and re-assembling the components. For this
reason, movable-shelf racks are fitted with one or more permanent shelves and/or braces that
provide the needed stability to the structure. This section specifies the provisions for identifying
those stabilizing components, and for posting warnings and restrictions for removal.
Wind loads
There are instances, such as outdoor installations or rack-supported structures, where storage
racks are the main wind-resisting structural system.
When walls do not protect the rack system, wind will exert force primarily on the surface area of
the pallet loads in the stored locations. Consideration should be given to unit loads of less
than maximum weight but the same size as the posted unit load. Consideration should also be
given to partially loaded rack where, for instance, a load is placed only in the top position. The
effects of wind acting on the rack components when empty or during construction should also
be considered.
When a rack system supports a wall, consideration should be given in the design, especially for
overturning, of racks that could be subjected to wind loading, whether pallets loads are placed
in the racks or the racks are empty.
Earthquake
forces General
This section provides modifications to the guidance set forth in ASCE/SEI 7 to account for the
unique structural characteristics of industrial steel storage racks.
1 Roure, F., Peköz, T., Somalo, M.R., Bonada, J., Pastor, M.M., Segura, A., Casafont, M.,
Industrial Cold-Formed Steel Rack Column Base Fixity and Strength, Proceedings,
International Conference on Cold-Formed Steel Structures, 2016.
It is important that industrial steel storage rack systems be engineered, manufactured, installed,
and utilized in a manner that they perform adequately under all anticipated loading conditions.
Many geographic regions have building codes that require building and non-building structures,
including storage rack systems, be designed to accommodate earthquake loads. The analytical
approach to the seismic behavior of rack structures developed within ANSI MH16.1-2021 is
intended to reflect the current thinking documented in FEMA P-1050, ASCE/SEI 7, and the
International Building Code.
If the rack structure is connected to another structure in a manner which significantly
modifies the free field ground motions, then this structural interaction needs to be made part of
the analysis and resulting design of both the rack system and the supporting structure. While
most storage racks are typically supported at grade, there are cases where they are supported
in buildings on floors above grade. For these cases, the seismic design forces are increased
because the earthquake forces are amplified by the response of the building structure to the
earthquake motions, and separate procedures provided in ASCE/SEI 7 Chapter 13 have been
specified to determine the design earthquake forces.
A principal advantage of mass-produced steel storage rack systems is their modular design,
which allows considerable flexibility of configuration and installation. This advantage also
presents a serious challenge to competent seismic performance. The initial installation of a rack
system should be in accordance with an engineered design. Subsequent modifications should
be made only with guidance by a registered design professional to avoid compromising the
seismic integrity of the system. Further, storage rack systems are often subject to rough use
and damage. Periodic inspection and maintenance of the rack system is necessary to ensure its
structural integrity in the event of an earthquake.
Seismic design criteria
The base of a rack system supported by a floor slab at or below grade experiences ground
accelerations directly, and the design should proceed accordingly. For a rack system supported
by another structure (e.g., an upper story of a multi-story building structure), the structural
analysis needs to consider the interaction between the structures, and the amplification of
earthquake forces with relative height within a supporting structure.
The system importance factors with magnitudes greater than one are intended to result in a
higher performance level for certain rack installations under seismic conditions such as:

systems installed at essential facilities that would be expected to remain in operation
following a seismic event;

systems that store hazardous materials; and

warehouse-style retail stores where the rack system is accessible to the public.
In warehouse-style retail store, unlike a sparsely-populated typical warehouse and distribution
center, large numbers of the public can be expected to be within the rack system during
business hours. The consequences of a rack failure in this environment dictate a higher level of
performance for such systems. The 𝐼𝑒 factor of 1.5 for warehouse-style retail stores is
equivalent to having the racks being designed for maximum considered earthquake event
performance, which is consistent with the stated performance goals of FEMA 460.
The owner should inform the registered design professional whether any hazardous material
will be stored in the storage rack, whether the storage rack will be open to the general public,
and whether the racks will be installed in an essential facility.
The 𝐼𝑒 factor can be 1.0 if an acceptable displacement-based analysis is used because the
displacement demand used in the displacement-based analysis should be determined, as
recommended in FEMA 460, based on demands on the Maximum Considered Earthquake
(MCE) level rather than the Design Earthquake level. For the down-aisle direction, the
procedure provided in 9.4.2 is an acceptable displacement-based analysis to determine the
needed rotational capacity of the beam-to-column connections, while the procedure in 11.3 is an
acceptable displacement-based procedure to determine the needed rotational capacity of the
column base plate connections. Since rotational demands determine these connections based
on Design Earthquake level forces and displacements, they need to be multiplied by 𝐼𝑒 to obtain
MCE level demands. There are currently no acceptable displacement-based analysis similar
procedures provided in ANSI MH16.1-2021 in the cross-aisle direction. A displacement- based
evaluation can include the movement of the pallets on the shelf beams. The movement of the
pallet should not be more than what would cause the pallet to fall off the shelf beams for the
cross-aisle analysis or the sum of the product load clearances for the down-aisle analysis.
To properly account for the fact that the product loads placed on shelves are often less than the
capacity for which the shelves are designed, the product load reduction factor (𝑃𝑅𝐹 ) is introduced.
Thus, in the longitudinal (or down-aisle) direction, where there are numerous repetitious pallet
positions, 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 is defined as the maximum total weight of product expected on the shelves
in any row divided by the number of shelves in that row. 𝑃𝑚𝑎𝑥𝑖𝑚𝑢𝑚 is defined as the
maximum weight of product that will be placed on any one shelf in that row, this being usually
the design capacity for the pallet positions. With 𝑃𝑎𝑣𝑒𝑟𝑎𝑔𝑒 and 𝑃𝑚𝑎𝑥𝑖𝑚𝑢𝑚 , 𝑃𝑅𝐹 becomes the
quotient of the two. This reduction is not applicable in the cross-aisle direction.
The 0.67 coefficient applies to the loading considerations under seismic events. It does not
apply to vertical load under any load combination nor to the fraction of vertical load used for
restoring moment in the evaluation of seismic stability. Research has shown that there is some
friction inducing, energy dissipating, relative movement between the rack and the stored product
during seismic motions. The 0.67 coefficient represents the fraction of the dynamically active
load on a fully-loaded system that is likely to be felt by a structure in a normal application, and
that needs to be taken into account in the determination of lateral loads under seismic events. If
the dynamic portion of the load for a particular installation is likely to be greater than 67%, then
a higher magnitude should be used in the determination of lateral forces.
Alternatively, the seismic design evaluation can be performed using a displacement-based
method, such as the method described in FEMA 460, 6.5.1.
The equation for design seismic force for racks supported above grade by other structures
provided in 7.4.2.3 is based on the requirements of ASCE/SEI 7 Section 15.3.1 where the seismic
design forces are required to be determined for such cases in accordance with ASCE/SEI 7
Chapter 13.
Redundancy factor
A redundancy factor, 𝜌, is included in the design of rack. It only comes into effect for Seismic
Design Categories D, E and F.
Plan and Back Bracing is shown in Figure C10.2-1 and a Braced Tower is shown in Figure C10.2-3
(a).
The factors shown in this standard are based on a standard storage rack configuration, with
many semi- rigid beam-to-column connections down-aisle and frames braced with diagonals or
horizontals and diagonals cross-aisle. Other configurations are permitted, but the redundancy
factor needs to be adapted to suit each configuration.
In ANSI MH16.1-2012, two frames tied back-to-back were considered to be redundant (i.e.
achieve a redundancy factor [𝜌] of 1.0) under certain conditions. This consideration was not
incorporated into ANSI MH16.1-2021 because such frames do not fully satisfy the redundancy
definitions of ASCE/SEI 7. Instead, three frames tied together are needed to achieve a
redundancy factor (𝜌) of 1.0 in accordance with ASCE/SEI 7. However, two frames provide
more redundancy than a single frame (𝜌 = 1.3) and have some partial redundancy. Therefore,
a redundancy factor of 𝜌 = 1.15 has been added to ANSI MH16.1-2021 for this case.
In addition, a 𝜌 = 1.15 has been added for uprights that include X-bracing, where each diagonal
is designed to equally resist the design seismic forces in tension and compression.
Additionally, in ANSI MH16.1-2012, two adjoining bays in the down-aisle direction were
considered to be redundant. It was later determined at least three adjoining bays were needed
to be considered sufficiently redundant to achieve a redundancy factor of 1.0 in accordance with
ASCE/SEI 7. However, two bays provide more redundancy than a single bay (𝜌 = 1.3) and have
some partial redundancy and therefore, a redundancy factor of 𝜌 = 1.15 has been added for this
case. For two uprights with X-bracing that are tied back-to-back, a redundancy factor of 𝜌 = 1.0
can be used.
Site coefficients and adjusted maximum considered earthquake spectral response
acceleration parameters
Mapped spectral acceleration parameters 𝑆𝑆 and 𝑆1 apply to sites that have 𝑣𝑠̅ =2,500 ft/s
(soils between Site Class B and C). For all other soils, the values for 𝑆𝑆 and 𝑆1 need to be
adjusted. This is done by means of site coefficients 𝐹𝑎 and 𝐹𝑣 listed in Tables 7.4-1 and 7.4-2,
respectively. Special attention needs to be given to Site Class D.
Notes to Table 7.4.-1 for Site Coefficient 𝐹𝑎:
There is a choice of Site Class D and D-default in Table 7.4-1. Section 7.4.7 includes additional
information on Site Class D-default. ASCE/SEI 7, Section 11.4.4 requires that value of the site
coefficient
𝐹𝑎 shall not be less than 1.2 for Soil Class D-default to ensure that this value is not less than 𝐹𝑎
for Site Class C. ANSI MH16.1, Table 7.4.-1 expands ASCE/SEI 7, Table 11.4-1 to include
Soil Class D-default for clarity.
Notes to Table 7.4-2 for Site Coefficient 𝐹𝑣:
ASCE/SEI 7, Section 21.2, Site Class D requires that for 𝑆1 ≥ 0.2, a Ground Motion Hazard
Analysis (GMHA) is needed, unless Site Class D-Default values are used. The value of 2.4 for
𝑆1 < 0.1 is taken directly from ASCE/SEI 7, Table 11.4.2. The value of 2.2 for 𝑆1 = 0.2 in Table
7.4.2 is also taken directly from ASCE/SEI 7, Table 11.4.2. Table 7.4-2 Note 5 allows for
interpolation between 2.4 and 2.2 for
𝑆1 > 0.1 and 𝑆1 ≤ 0.2. For Site Class D-default, the other values for 𝑆1 ≥ 0.2 have been amplified so
that a site-specific GHMA is not required. The GHMA needs to include site effects. There is also a
possibility to use values without the ground motion hazard analysis. For that case, the values listed
in Table 11.4-2 shall be amplified (the response spectrum shall be modified). ANSI MH16.1, Table
7.4-2 amplifies these values directly, allowing for a choice between Site Class D with GMHA or Site
Class D without GMHA. For Site Class D with GMHA, Table 7.4-2 includes a note with a reference
to ASCE/SEI 7, Section 21.2 which gives details on GMHA. For Site Class D without GMHA, Table
7.4-2 includes the applicable values of Site Coefficient 𝐹𝑣.
Design spectral response acceleration parameters
ANSI MH16.1-2021 utilizes spectral design (based on ASCE/SEI 7) performed for earthquake
demand that are two-thirds of the 𝑀𝐶𝐸𝑅 response spectra. Two parameters, 𝑆𝐷𝑆 and 𝑆𝐷1, are
used to define the acceleration response spectrum for this design level.
Determination of the seismic response coefficient
The seismic response coefficient is a site-specific value. The magnitude of this coefficient is a
function of the seismic characteristics of the rack structural system through the values of 𝑅 and
the fundamental period of the structural system, 𝑇. It is also a function of the site-specific ground
motions and the characteristics of the soil underlying the building where the storage rack is
installed. The 𝑅-factor is an empirical response reduction factor intended to account for damping
and the ductility inherent in the structural system at displacements great enough to surpass
initial yield and approach the ultimate load displacement of the structural system. The 𝑅-factor is
not only a function of energy dissipation and ductility, but reflects also the overstrength of the
seismic system used. A specific procedure that can be used to justify larger 𝑅-factor values is
provided in FEMA P695, Quantification of Building Seismic Performance Factors.
The procedures to determine the design ground motion values for a given site is provided in 7.4.5
through
7.4.8 and is further explained in the commentary below.
Period computations need to employ rational methods. The empirical equations for buildings are
not applicable to storage racks and cannot be used. There is no restriction on the period thus
computed (see ASCE/SEI 7, Section 15.4.4). In the down-aisle direction, storage racks typically
have much higher drifts than buildings, resulting in much longer periods than a building.
There are several ways for estimating the fundamental period of vibration for a pallet rack in the
down aisle direction. One method that is used is the Rayleigh Equation:
where:
𝑊𝑖
is 𝐷 + 𝑃 (used to determine the seismic lateral forces) + 0.25𝐿𝑆 at each level 𝑖
(See 7.4.2.2: 𝐷 + 0.67𝑃𝑅𝐹 𝑃 + 0.25𝐿𝑆);
𝐹𝑖
is the seismic lateral force at level 𝑖. The force at each level needs to be
computed from the force distribution equation required by the seismic design
code. These formulas are given in 7.4.13;
𝑔
is acceleration due to gravity (386.4 in/sec2) (9.81 m/s2);
𝑇
is the fundamental period of vibration;
𝛥𝑖
is total lateral displacement at level 𝑖 relative to the base, as computed using 𝐹𝑖.
To use the Rayleigh Equation, it is necessary to be able to compute the story lateral
displacements. These values can be found by a rigorous frame analysis or by approximation.
More accurate computations of the lateral displacements will result in a more accurate 𝑇 value.
If the drifts are underestimated, the resulting 𝑇 value will be conservative.
The period in the cross-aisle direction can also be calculated or approximated but is usually much
shorter.
An alternate acceptable method of computing the period is provided in FEMA 460 using the
rotational stiffness 𝐾𝑐𝑜𝑛𝑛 from 7.2.5.
Site class definitions
Table 7.4-3 outlines soil classifications based on soil profiles. This table comes from ASCE/SEI 7.
It is standard practice to use the same Site Class as determined for the building for the design
of storage rack that are located within or adjacent to the building.
When soil classifications are not known, Site Class D-default can be used, as specified in
ASCE/SEI 7, Section 11.4.3, as long as geotechnical data determine that Soil Class E or F are
not present at the site. Such a determination can be subject to approval by the authority having
jurisdiction.
Mapped acceleration parameters 𝑺𝑺 and 𝑺𝟏
The site-specific risk targeted MCE ground motions for a given site are specified as spectral
response acceleration 𝑆𝑆 and 𝑆1 are available from websites such as the ASCE 7 Hazard Tool
(https://asce7hazardtool.online/) which will be available as a free download by the end of 2021.
In the interim, https://seismicmaps.org/ is a viable source for obtaining the values. These
websites provide values for 𝑆𝑆 and 𝑆1, and the Design Earthquake values for 𝑆𝐷𝑆 and 𝑆𝐷1 for a
given site soil profile type. If the soil profile type is unknown, the websites provide values for the
default soil type. For Site Profile Type D and E in higher seismic areas, the site 𝐹𝑎 and 𝐹𝑣
factors are greater in ASCE/SEI 7 than in prior editions. See the commentary of ASCE/SEI 7
Chapter 11 for the reasons for these increases.
Seismic design category
The Seismic Design Categories are a function of the seismic hazard at a site, the Risk Category
of the building constructed at the site and the site-specific soil data. Figure C7.4-1 is a map
representing Seismic Design Categories in the United States for assumed Class D soil
conditions.
Magnitudes of the spectral response acceleration 𝑆𝑆 and 𝑆1 are to be taken from the
accompanying contour maps or USGS Open-File Report 01-437 “Earthquake Spectral
Response Acceleration Maps” Version 3.10 as specified by the building code authority.
Figure C7.4-1 – Seismic design categories
Seismic displacement
The stiffness of all members and connections used to compute 𝛿𝑥𝑒,𝑠 should be the same as
used for the design of the structure.
When computing the seismic displacement 𝛿𝑥𝑒,𝑠, all loads used should be determined using the
LRFD strength load combinations of Section 7.1.3. The total earthquake force (𝐸) should be
used rather than 0.7𝐸 that is used for strength calculations in ASD. If the ASD-level earthquake
forces which have utilized the load combinations of Section 7.1.2 are used, the displacement
should be multiplied by 1.43 to obtain
𝛿𝑥𝑒,𝑠.
Seismic separation
For racks assigned to Seismic Design Category D and above, the seismic separation is checked
in accordance with 7.4.12. This section allows a separation to be checked by analysis of the
specific structure or by default distances given in the table for the braced and unbraced
directions. Storage rack seismic displacement is less in the braced direction, so the required
separation is less. If an analysis is used to compute the seismic displacement, this analysis
should be performed using the LRFD combinations of 7.1.3 with the seismic force 𝐸 (not 0.7𝐸)
applied to the rack.
These separations are intended to include the effects of both the rack and the building
structure. Amplification of the computed rack drift is felt to be adequate to accommodate the
building drift.
Vertical distribution of seismic forces
The calculation of the vertical distribution of the lateral forces 𝐹, which are being resisted by the
base shear, 𝑉, results in a linearly increasing or triangular distribution for values based on the
recommendations of FEMA 460.
It is appropriate to account fairly for the contribution of the shelf-loading pattern on the
development of the lateral forces, their distribution, and the resulting behavior of the rack
structure. Thus, it is felt that when the bottom most pallet beam is within 12 in. (30 cm) of the
floor, such a shelf loading contributes little to the lateral deflections and resulting lateral force
distribution along the height of the structure. However, when such a bottom shelf is located at
an elevation greater than 12 in. (30 cm) above the floor, the contributions will begin to be
significant and should be considered in the same manner as the remaining loading on all the
upper shelves.
Horizontal distribution of seismic load at a storage level
The magnitude of the lateral shear force at any level is determined simply by the equations of
equilibrium applied to the particular section of the structure. The story shear in any story is the
sum of the lateral forces acting at all levels above that story.
Vertical impact loads
Beam damage typically occurs when pallets are placed on or removed from shelves.
Considering the magnitude of the forces possible, no beam can be designed and guaranteed to
not be damaged by a pallet being dropped onto the rack or when a beam being hit from the
underside when a pallet is lifted too forcefully. An allowance for impact can therefore be no
substitute for proper forklift operation. Forklift operation is beyond the scope of responsibility for
the registered design professional. Facility owners need to ensure that forklift drivers are
properly trained and responsible, and that untrained personnel are prohibited from operating
forklifts.
Some degree of impact to the shelf will occur during operation. When a pallet is loaded onto the
storage rack, the impact force will be transmitted by the pallet being loaded. The pallet position
should be chosen to ensure that the minimum safety margin exists for loading pallets at any
location, this section requires the impact force to be on one shelf distributed along the width of
the pallet which causes the greatest stresses.
When determining allowable loads by test, the impact load needs to be included in checking
compliance with this section. The impact load should be applied by loading one pallet at 125%
of the test weight and all other pallets at 100% of the test weight. This will give an additional
25% of the test pallet load on each shelf. The heavy pallet might have to be placed in different
locations to check bending moment, shear force, and end connections. When testing or
designing for deflection in accordance with C9.3, the inclusion of impact is not required.
This impact provision is included to add extra safety to the design of the shelves and their
connections due to vertical impact of loads being placed by the forklift or other device. When
25% of one pallet load is added for impact on a two-load wide shelf, the margin of safety is
about 1.67 as shown in C7.1.3. This is equal to the traditional margin of safety. If there is one
load per shelf, the margin of safety would be higher. For a shelf loaded with several small
boxes, the margin of safety could be less and could approach 1.4/𝜙 or 1.56 minimum.
Horizontal loads
ANSI MH16.1-2021 requires stability design to account for rack lean (global imperfection) when
loaded. Section 7.6 requires the notional loads to be combined with the earthquake loads (a) or
wind loads (b). Structures also need to be checked for notional loads alone. The 1.5%(𝐷 + 𝑃 +
𝐿) minimum load for the design of braces and their connections required in ANSI
MH16.1-2012 is still required in ANSI MH16.1-2021.
Storage racks for automated storage and retrieval systems
Storage racks associated with automated storage and retrieval systems (traditionally referred
to as “stacker racks”) are structures commonly classified as a special industrial occupancy
category.
Seismic overturning
The overturning checks are intended for only anchor uplift and floor reactions. ANSI MH16.12021 requires two separate overturning checks. One is for the case of all storage positions
loaded to 67% of the full rated capacity and the other for 100% in the top load position only.
Due to added conservatisms in the anchorage design and to simplify the analysis, this
edition of ANSI MH16.1 allows the overturning forces to be applied to the storage rack at the
beam levels rather than at the load center of gravity as required by previous editions of ANSI
MH16.1.
C8
Design of steel elements and members
General
This section accounts for the effects on the perforations in industrial steel storage rack columns.
Perforated steel members
Section properties of cold-formed steel sections
In previous editions, the torsional properties were permitted to be calculated based on the sharp
corner section properties because it was difficult to calculate these properties for rounded
corners. This produces results that are unconservative for these properties. Many tools now
exist to obtain these properties for rounded corners. The rounded (or segmented) corners
should be used to obtain these properties.
This section gives an approach to idealize the sections with perforations for analysis by
assuming reduced thicknesses in the strips along the length of the member containing
perforations. The idealized sections with perforations were studied extensively in references 8.1
through 8.5 at the end of this section. Different strip thicknesses are to be used depending on
whether the strips are in the web or flanges of the section and on the type of behavior being
investigated.
Perforated steel members can consist of columns of either cold-formed or structural steels.
Concentrically-loaded perforated compression members
Axially loaded cold-formed steel open sections such as those shown in Figure C8.2-1 and
Figure C8.2-2 could be subject to distortional buckling, as well as flexural, torsional-flexural,
local buckling. These types of buckling could also occur interactively. The objective of this
section is to predict failure loads for these types of modes. The presence of perforations
significantly influences the performance. Since hot rolled structural sections and closed cold-
formed steel sections are not subject to distortional buckling, the distortional checks in 8.1.2 and
8.1.3 are not needed.
The basis of these provisions for axially loaded cold-formed steel open sections can be found in
References 1, 2, 3, 4, and 5. The approach was developed on the basis of physical tests, Finite
Element Solutions (as shown in Figure C8.2-3) and Finite Strip analyses. It was concluded that
the most suitable design approach would be to use finite strip analysis combined with the
expressions given in this section. Distortional buckling deformations are illustrated in Figure
C8.2-4.
Finite strip analysis and the calculation of section properties can be carried out using the
CUFSM
program,
which
can
be
obtained
at:
http://www.ce.jhu.edu/bschafer/cufsm/#standalone_version_for_PCs.
𝑃𝑐𝑟𝑑 is found by modelling the distortional cross section with axial load using CUFSM (or
similar programs). The distortional cross section is defined in 8.2.1 using Equation 8.2-2.
One of the sections studied
FSM Model
Figure C8.2-1 – An open section that could be subject to distortional
buckling
Figure C8.2-2 – Examples of sections that could be subject to distortional buckling
Figure C8.2-3 – Finite element models for correlation with finite strip models (FSM) and
physical tests
Figure C8.2-4 – Tested specimens demonstrating distortional buckling
Figure C8.2-5 – CUFSM analysis result (axial load vs. length of the section) shown in Figure
C8.2-3 and Figure C8.2-4
Web perforations (Dimensions in inches, strips of reduced thickness are shaded)
Flange perforations (Dimensions in inches, strips of reduced thickness are
shaded) Figure C8.2-6 – Reduced thickness strips
Perforated members bending about the centroidal axis perpendicular to the axis of
symmetry
The effects of perforations are accounted for by reduced thickness strips as was done in
Section 8.2.2. Limited Finite Element studies reported in Reference 6 on the beam shown in
Figure C8.2-7 indicate satisfactory results for the approach of this section.
𝑀𝑐𝑟𝑑 is found by modelling the distortional cross section with bending load using CUFSM (or
similar programs). The distortional cross section is defined in 8.2.1 using Equation 8.2-2.
Figure C8.2-7 – FEM model demonstrating distortional buckling under bending
References for design of steel elements and members
The following references provided context for the guidance in this section.
1.
Casafont, M., Pastor, M.M., Roure F., Peköz, T. “An Experimental Investigation of
Distortional
Buckling of Steel Storage Rack Columns.” Thin-Walled Structures 2011, 49(11): 933-946.
2.
Peköz, T., Kiymaz, G., Casafont, M, Pastor, M.M., and Bonada, J., “Design of Perforated
Industrial Storage Rack Columns for Distortional Buckling,” Proceedings of the Cold
Formed Steel Structures Conference, 2012, St. Louis, MO.
3.
Ribera, M.C., Fernández, F.R., and Coarasa, M.R.S., “Distortional buckling strength of
American type cold formed rack columns,” Report 42007/1A, Escola Tècnica Superior
d’Enginyeria Industrial de Barcelona, May 21, 2013.
4.
Casafont, M., Pastor, M. M., Roure, F., Bonada, J. and Peköz, T., “An Investigation on
The Design of Steel Storage Rack Columns Via The Direct Strength Method,” J. Struct.
Eng. 139, Issue 5, Special Issue: Cold-Formed Steel Structures, 669-679, May 2013.
5.
Casafont, M., Roure, F., Pastor, M.M., Bonado, J., “Elastic Buckling Loads of Rack
Columns with Web Perforations and Flange Holes,” Escola Tècnica Superior
d’Enginyeria Industrial de Barcelona, May 2014.
6.
Liu, S-W, Peköz, T., Gao, W-L, Ziemian, R.D., Crews, J., ”Frame Analysis and Design
of Industrial Rack Structures with Perforated Cold-formed Steel Columns,” Thin Walled
Steel Structures Journal 2021 (to be published).
C9
Beam design
Calculations
No commentary provided.
Cross section
For pallet rack and stacker rack beams, this section states that the load effects shall be
determined by conventional methods of calculation, if the shape of the cross section permits. In
general, the usual simple formulas for stresses and deflections of beams apply only if the cross
sections are symmetrical about the loading direction, i.e., if the section has a vertical axis of
symmetry. Beams of any other cross- sectional shape can twist under load. Such twist can
reduce the carrying capacity of the beams, and/or result in deflections larger than that
determined by conventional computations. Examples of such sections are channels, particularly
those with wide flanges, and wide flanged C-shapes when placed with web vertical. Since
calculations that include the twist are fairly complex and not always reliable, Section 9.2
requires test determination.
It is worth noting that closed box shapes, even if they have no vertical axis of symmetry, are
subjected to less twist than open shapes. Thus, in many cases for closed unsymmetrical box
beams, determination of section properties by conventional calculations could prove adequate.
The following equation can be used to account for the end fixity effect in determining the
maximum midspan moment 𝑀𝑀𝑎𝑥 of a pallet beam considering semi-rigid end connections:
where:
𝑀𝑀𝑎𝑥 is the maximum midspan moment;
𝐸
is the modulus of elasticity;
F
is the joint spring constant determined either by the Cantilever Test described in
C13.4 or by the Pallet Beam in Upright Frames Assembly Test described in
C13.3.3;
𝐼𝑏
is the beam moment of inertia about the bending axis;
𝐿
is the span of the beam;
𝑊
is the total load on each beam (including vertical impact loads);
𝑟𝑚
is the maximum moment reduction coefficient;
𝑀𝑒
is the beam end moment:
In the above derivation, the load is assumed to be uniformly distributed. For a value of 𝐹 equal to
zero,
𝑀𝑀𝑎𝑥 = 𝑊𝐿⁄8 is obtained. ANSI MH16.1-2021 requires applying a vertical impact factor of
25% to one unit load. For a pair of pallet beams supporting two pallets, this would mean that the
load on one-half of the beam would be 25% more than the load on the other half. The maximum
moment would not occur at midspan in that case. However, it can be shown that the magnitude
of the computed maximum moment would be within 1% of the moment computed on the basis
of distributing the total load uniformly.
For semi-rigid joints, the following expression for maximum deflection 𝑑𝑚𝑎𝑥 can be derived as:
Δ𝑚𝑎𝑥 = Δ𝑠𝑠 𝑟𝑑
where
:
Δ𝑠𝑠
(C9.2-4)
is the simply supported beam centerline deflection for a beam with a uniformly
distributed load, calculated as follows:
5𝑊𝐿3
∆𝑠𝑠=
384𝐸𝐼
𝑏
(C9.2-5)
𝑟𝑑
is the maximum deflection reduction coefficient, calculated as
follows:
(C9.2-6)
Deflections
The 1/180 of the clear span is an industry consensus figure based on visual appearance and
operational clearance considerations. Smaller limits could be required for beams that support
pallet flow or pushback lanes or carton flow shelves.
Beam-to-column
connections General
Beam end connections are designed to resist the forces and moments obtained from the
structural analysis.
The effects of eccentricity of the connection and the effect of rotation of an attachment to the
edge of an unstiffened flange needs to be evaluated. The influence of these connections on the
overall behavior is significant. Particular attention should be directed to the column-to-bracing
connections.
Connection rotational demand
This section resulted from the report presented in FEMA 460. 𝐶𝑑 is the deflection amplification
factor for a moment resisting frame and is obtained from ASCE/SEI 7, Table 15.4-1. From
FEMA 460, 𝐶𝑑 = 5.5 is the value for the unbraced frames and 𝐶𝑑 = 3.5 is the value for braced
frames.
The connection rotational capacity has to exceed the maximum rotational demand. The
maximum rotational demand can be computed directly using known earthquake records scaled
in accordance with ASCE/SEI 7, Section 16.2, as is done for buildings. This reduces the
uncertainties in establishing 𝛼𝑠 and
𝐶𝑑. Where available, as with buildings, such computations can be used in lieu of the
requirements in this section. At present, such analyses are not currently practical for everyday
design.
As a simplification, the demand equation in this section is upper bound based on the
assumption that the column and beam deformations are very small relative to the deflections
due to connector rotation. The basic connector rotational demand can be taken as the
maximum earth displacement divided by the height of the rack (the top level is assumed
stationary).
While perhaps convenient, this formulation can obscure the origin of the displacement demand.
It arises from expected maximum displacement of the ground and is not a function of the
structure itself. While not obvious, this formula is derived from ASCE/SEI 7 equation 17.5-3
(which was used in developing the FEMA 460 Appendix A equations). At the Maximum
Considered Earthquake level, the displacement demand would be:
(C9.4-1)
where
:
𝑇
is the effective period of the rack determined using the effective stiffness of the
rack at displacement, 𝛥, that has been appropriately modified to account for 𝑃 −
𝛥 effects;
𝐵
is the dampening coefficient determined as a function of the effective damping
and the effective peak ground acceleration. Values of 𝐵 are provided on Page 61
of FEMA 460.
This alternate formulation can be used in place of the complex FEMA 460 calculations.
The connection rotational demand should include the effect of gravity load amplification. The
column axial load used in the calculation of the gravity load amplification does not include the
effective horizontal seismic weight factor, 0.67 on the 𝑃. This is because the entire product load
contributes to the gravity load amplification portion of the drift.
Since the seismic response of storage racks is a dynamic phenomenon, use of the full
amplification 1/(1 − 𝛼𝑠) is conservative for the seismic base and beam-to-column connection
rotational demand analyses. The (1 + 𝛼𝑠) term is used to account for only the first iteration of
the second order effects. The intent is to obtain a reasonable estimate of these effects, not
restrict the registered design professional to any one method of obtaining them. Better
estimates of the amplified effects of gravity load (shake table results or other time dependent
computer modeling methods) are allowable.
In the equation for the connection rotational demand, the 1 + 𝛼𝑠 term estimates the effects of
gravity load amplification. Based on FEMA 460, the 𝛼𝑠 term is calculated as follows:
level
s;
where:
𝑁𝐿
is the number of loaded
𝑊pi
is the weight on the rack that amplifies the drift. The 0.67 coefficient for the
product load should not be used because the entire product weight amplifies
the drift:
𝑊𝑝𝑖 = (𝑃𝑅𝐹 𝑃) + 𝐷 + 0.25𝐿𝑆
(C9.4-3)
𝑘𝑐
13.5;
is the rotational stiffness of each beam-to-upright connection from testing outlined in
𝑘𝑏
is the rotational stiffness of each base plate connection (which can be assumed
to be equal to 𝑘𝑐 for installations where there is at least one anchor bolt on
opposite sides of the column in the down-aisle direction);
𝑁𝑐
is the number of beam-to-upright connections;
N𝑏
is the number of base plate connections;
𝑘be
is the beam end rotational stiffness, assumed to be given by:
(C9.4-4)
𝑘ce
is the bottom column end rotational stiffness, assumed to be given by:
(C9.4-5)
For computing 𝛩𝑑, the displacements are multiplied by a factor of 1.5 to get them to the MCE
level, which is specified in FEMA 460.
For both the ASD and the LRFD method, the seismic drift, 𝛥𝑠, is computed using the entire
weight on the beams (𝑊𝑝𝑖) when using a second order computer analysis.
Beam locking device
The upward force is specified to prevent accidental disengagement of the beam connection.
The upward force should be applied to an unloaded beam. Since this force is compared to the
connection locking device failure, there is no load factoring required.
Failure of the locking device is defined as the distortion of the locking device that prevents
reapplication of upward force, removal, reinstallation, or reduces the carrying capacity.
Movable-shelf racks
The movable storage levels are generally constructed of a set of front and rear longitudinal
beams connected rigidly to each other by transverse members.
The upward load is specified to prevent accidental disengagement of the beam connection. The
upward force should be applied to an unloaded beam. Since this load is compared to the
connection locking device failure, there is no load factoring required.
The phrase “connected rigidly to each other” indicates that the beams are connected so that
skewing of transverse members would be prevented in normal use.
Pallet supports
Pallet supports can be installed between load beams. They can be constructed of metal, wood,
or other suitable material.
There are many types of pallets and containers that can be stored on a pallet rack storage level.
In general, a properly placed stored unit that is on a structurally sound pallet will adequately
support the product on the pallet spanning between the beams. In that case, additional supports
are unnecessary. In the absence of information to the contrary, it is customary for the registered
design professional to assume that the warehouse operator will be using pallets that are
adequate to support the load spanning between the load beams throughout the entire
warehouse.
Based on the operation of the facility, there could be the potential for the pallet to be
misplaced on the load beams in such a way that the edge of the pallet does not rest on the
beam. In this case, if crossbars are requested by the facility operator, the bottom of these
pallets or containers can cause some or all of the load to be applied to the crossbar. Refer to
Figure C9.5-1. The crossbar should be designed to have adequate stiffness and strength to
support the anticipated load and transfer that load to the load beams. Crossbars also need to be
designed to support the load for the case of a broken pallet stringer. Since the crossbar is an
accessory and the design requirements can be many and varied, the detailed design of
crossbars for the many particular situations is beyond the scope of this specification. It is
recommended that crossbars have the bending strength and stiffness to support that portion of
the load that is between the load beams.
The specification requires that the ends of the crossbars are attached to the beam to prevent
lateral movement along the load beams.
Properly placed stored unit
Misplaced stored unit
Misplaced stored unit
Figure C9.5-1 – Examples of pallet storage
positions Welded wire rack decking
Wire decking is a decking system used on pallet rack shelves to provide additional support for
stored materials. and to retain unstable loads. Wire decking is fabricated from welded-wire
mesh, and usually has reinforcements in the form of channels or support wires. Wire decks are
typically supported by the rack beams at the front and rear and the strength and stiffness of the
wire deck system provides support for the load between the beams. Decking designs vary
greatly depending on the application. Wire thickness, grid pattern and number of channels all
have an effect on performance. Wire decking is unique to other types of shelving not only in
appearance but also in performance. Because wire decks are made of steel, their integrity,
capacity, and performance remain constant. The advantages of wire mesh decks include safety,
their ability to allow light, air, debris, and water (which is important in some jurisdictions due to
fire codes) to pass through the decks.
C10
Upright frame design
Upright frames
This section requires upright frames and multi-tiered portal frames be designed based on
combinations of critical combinations of the most unfavorable vertical and horizontal load
conditions, taking into consideration all moments and forces induced in the columns.
Column design
Flexural buckling in the direction perpendicular to the upright
frames Racks not braced against sidesway
Previous editions of ANSI MH16.1 used the effective length method for the design of racks to
prevent sidesway instability. ANSI/AISI S100 and ANSI/AISC 360 no longer allow this design
method for structures with slender columns, such as storage racks. Therefore, ANSI MH16.12021 has stability design requirements in 7.2 that resemble the provisions in ANSI/AISI S100
and ANSI/AISC 360, but include changes, such as the treatment of product loading to make
them applicable to storage racks. When the stability requirements of 7.2 are followed, the value
𝐾𝑥 = 1.7 previously required for sidesway buckling is no longer required and 𝐾𝑥 = 1.0 can be
used.
Racks braced against sidesway
In order to be treated as braced against sidesway, a rack structure requires diagonal bracing in
the vertical plane for the portion under consideration. This restrains the columns in the braced
plane. In order to restrain the columns in other planes, the rack structure requires shelves that
are rigid or have diagonal bracing in their horizontal plane. Some of the parts used above are
illustrated in Figure C10.2-1. The function of this rigid or braced shelf is to ensure restraint for
the other row of columns against sidesway with respect to the braced row of columns. All
bracing needs to be connected tightly and designed for its intended use.
Horizontal movement, or translation, of the front column relative to the rear column of rack with
bracing in the rear vertical plane can, in some cases, be prevented by the presence of pallets on
the load beams. To prevent translation of the front column, the frictional forces between the
pallets and the load beams need to be capable of resisting horizontal force perpendicular to the
plane of the upright. The magnitude of this force at a bracing point should be at least 1.5% of
the column load immediately below the beam acting as the horizontal brace. The potential
presence of sufficient forces to prevent translation can be determined by rational analysis
considering factors such as, but not limited to, lighter than normal loads and the absence of any
or all loads.
The coefficient of friction between a wood or metal pallet and its supporting beams in typical
warehouse conditions has been the subject of several tests and can conservatively be
estimated as 0.10. Special consideration is necessary in cold storage freezers where
operational procedures can produce ice on the contact surfaces. Representative tests are
recommended in this and other conditions, such as greasy or oily environments, where they
would likewise be warranted.
In order to cut down the unsupported lengths of the columns, the diagonal bracing should divide
the brace plane as shown in Figure C10.2-2 (a) and (b). At the same time rigid or braced fixed
shelves are to be provided at levels AA in order to have unsupported lengths of h as shown in
the figures. If such shelves are not provided at levels AA, then the column will be designed in
accordance with 10.2.1.1.
The bottom and top portions of columns in Figure C10.2-2 (c) are to be designed as columns in
an unbraced rack, whereas those in the mid-portion as columns in a braced rack.
Figure C10.2-1 – Plan and back bracing
(a) (b)
(c) Figure C10.2-2 –
Racks braced against sidesway
Applicable column length for flexural buckling in the plane of the upright frame
In an upright frame, 𝐿𝑠ℎ𝑜𝑟𝑡 and 𝐿𝑙𝑜𝑛𝑔 refer to the minimum and maximum distances between
two adjacent segments. All distances are measured along the neutral axis of the column.
In rack structures, the columns are usually either singly symmetrical shapes with the axis of
symmetry in the plane of the upright frames or doubly symmetric shapes. Because of this,
buckling in the planes of the uprights is usually flexural. Upright frames have a wide variety of
bracing patterns. The most effective bracing pattern is one where the centerlines of braces and
the columns intersect at one point as shown in Figure C10.2-2(a). This is because the braces
restrain the columns by virtue of their axial stiffness. On the other hand, the bracing action in
the system shown in Figure C10.2-2(b) depends on the flexural rigidities of the braces and
the connections between the columns and the braces. Thus, this type of bracing is not as
effective.
The effective length factor for the frame of Figure C10.2-3 (a) can usually be taken as 1.0. This
assumes that the braces are adequate and the connection between the braces and columns are
sufficiently rigid in the axial direction of the braces. The effective length factor for the frame of
Figure C10.2-3 (b) is usually greater than 1.0 and can be calculated by rational analysis.
(a)
(b)
Figure C10.2-3 – Braced and unbraced frames
In rack structures the centerlines of the horizontal and the diagonal braces and the centerline of
the column frequently do not meet at one point. Thus, the bracing arrangement falls between
the extremes illustrated in Figure C10.2-4 (a) and (b). The following three scenarios treat
various bracing configuration possibilities.
Upright frames with diagonal braces or a combination of diagonal and horizontal braces that
intersect the columns are illustrated in Figure C10.2-4 (a) and (b). These figures also define the
terms 𝐿𝑙𝑜𝑛𝑔 and 𝐿𝑠ℎ𝑜𝑟𝑡.As the ratio 𝐿𝑠ℎ𝑜𝑟𝑡⁄𝐿𝑙𝑜𝑛𝑔 increases, the frame approaches the case
shown in Figure C10.2-4 (b) and hence, the effective length factor can be greater than one.
The stability of the frame depends on not only the relative axial and flexural stiffness of the
members, but also the details of the connections between the members. The axial stiffness at
the connection in the direction of the braces depends on the details of the connection.
Upright frames with diagonal braces that intersect horizontal braces are illustrated in Figure
C10.2-5 (a) and (b). As the ratio 𝐿𝑠ℎ𝑜𝑟𝑡⁄𝐿𝑙𝑜𝑛𝑔 increases, the basic behavior of the frame
approaches that of Figure C10.2-5 (b) and hence the effective length factor can be greater than
one.
For uprights having a bracing pattern such as the configuration shown in Figure C10.2-3 (b), no
typical effective length factors are recommended. Rational analysis can be used for such cases
to determine the effective length factor. Alternately, the load carrying capacity can be
determined by test.
(a)
(b)
Figure C10.2-4 – Frames with diagonal braces that intersect the columns
(a)
(b)
Figure C10.2-5 – Upright frames with diagonal braces that intersect the horizontal
braces Column length for torsional buckling
Though torsional buckling is not likely to happen in rack structures, torsional-flexural buckling is
usually the governing critical buckling mode for open C-shape sections. The torsional buckling
effective length factor is a parameter in the analysis of torsional-flexural behavior. The value of
𝐾𝑡 given in this section assumes an effective connection between the columns and the braces
as shown in Figure C10.2-6.
Figure C10.2-6 – Joint details
Frame bracing design
𝐾𝑥𝐿, 𝐾𝑦𝐿 and 𝐾𝑡𝐿 are the effective lengths of the brace between connection points. When
braces are welded to the columns to prevent twisting, the 𝐾𝑡 value for the brace can be taken
as 0.8. The connections between the column and the brace need to be designed for the force in
the brace.
Frame tie
design General
Frame ties are horizontal structural members that link a rack frame with another aligned frame
or single post, one behind the other within a frame line. The design of these individual members
considers both seismic and non-seismic load requirements. The calculated seismic force is
factored by the applicable redundancy factor, as specified in 7.4.3. The seismic load
combination for the allowable strength design (ASD) already contains a 0.7 factor, so no further
reduction of the earthquake force is allowed.
The design requirements specified in this section are applicable to straight-leg frames where the
product load is equally distributed to the frame’s front and rear posts. For slope-leg or offset-leg
frames, the registered design professional needs to consider that the center of mass is closer to
the recessed post and not symmetrically located between the front and rear columns. For such
frames, the design needs to include an analysis that considers all possible load patterns in order
to evaluate the most unfavorable loading condition for the frame ties.
Back-to-back ties (row spacers)
Back-to-back ties, commonly referred to as row spacers, provide structural stability in the rack
frame’s cross-aisle direction when connecting two or more aligned frames. These components
also provide structural redundancy to the brace members of a rack frame. The tie member and
its connection are sized so that they can perform their intended function and resist the most
critical of the calculated design forces.
While seismic base shear is distributed in a triangular pattern, if one assumes that back-to-back
frames are equally loaded, there is minimal force transfer through the tie member. Using the
seismic forces calculated in C7.4 to design the uppermost tie, when there are intermediate ties,
is conservative. When back-to-back ties are installed below the upper-most tie, the analysis can
presume that the forces applied to the upper-most tie would be decreased, and the back-toback tie members could be proportioned accordingly.
At least two back-to-back ties should be provided between a pair of rack frames and vertically
spaced as shown on the LARC drawings. Back-to-back ties, however, should be
positioned at elevations that provide a direct load path between the frame posts—generally
spaced 10 to 12 ft (3.0 to 3.6 m) apart at bracing nodes. Installation of back-to-back ties directly
above a load beam should be avoided when they could potentially restrict the storage level’s
adjustability during future, approved rack reconfigurations.
The design requirements of this section do not apply to ties that are not used to transmit forces
between frames. In these cases, the frames comprising the individual rows of rack are designed
so they are not dependent on an external structure for cross-aisle stability.
The use of back-to-back ties to form double rack rows or multi-pallet deep storage systems is
recommended to ensure that frames remain separated by a specific distance. Ties can assist
with the rack’s installation and maintain the geometry of the rack structure during its use. When
fire protection requirements dictate that minimum longitudinal flue space clearances be
provided, it is critical that proper back-to-back tie lengths be specified with care.
Frame-to-column ties
Frame-to-column ties are horizontal brace members between a frame and a single column in a
frame line. Their primary function is to brace the column against minor-axis buckling and are
designed with adequate strength and stiffness to control the post’s movement. These ties are
designed to resist a minimum horizontal load of 1.5% of the factored product load, as specified
in 7.6. At times, these components can also transfer pass-through forces in a frame-columnframe cross-aisle rack configuration to stabilize linked frames. Frame-to-column ties are also
designed to resist a 350 lbf (1,560 N) horizontal force, similar to that specified in 10.4.2 for
the purpose of checking overturning for racks loaded by powered equipment. The size of the tie
member and its connection is such that it can perform its intended function and resist the most
critical of the calculated design forces.
Flue shear ties
Flue shear ties are substantial structural members used between back-to-back frames to resist
lateral loads and provide cross-aisle stability, typically for slender racks installed in moderate to
high seismic areas. They provide lateral resistance to the rack structure by resisting in-plane
loads along the height of the frames. By integrating shear ties between frames, the aspect ratio
of the rack frame is significantly reduced. Reaction forces on the floor slab can be subsequently
smaller in magnitude, resulting in anchor and base plate designs that are workable for typical
warehouse operations. A rigorous analysis of flue shear ties and their connections is warranted
to ensure that the strength and stiffness requirements are satisfied.
Cross-aisle ties
Cross-aisle ties are horizontal members that span across an aisle, connecting the tops of two
opposing frames. Rack frames loaded by powered loading equipment with large aspect
ratios, particularly those with height-to-depth ratios greater than 8 to 1, require close
examination of their cross-aisle stability. The usual and preferred practice to improve stability is
to provide overhead cross-aisle ties between opposing frame(s). When a lateral force is
transmitted to an adjacent structure by the tie beam, the structure is designed to resist its
calculated portion of the force. Given that single rows of rack are more prone to overturning or
collapse if damaged, the installation of cross-aisle ties is recommended to lessen the probability
of a rack failure due to an accidental impact.
If a cross-aisle tie is connecting two uprights, then each upright will deflect the same amount at
the top. If the uprights have differing cross-aisle stiffness, then the lateral loads at the tops of the
frames need to be in proportion to the stiffness of the frames so they have the same lateral
displacement.
C11
Column base design
Column base plates
Bearing on concrete
Formulas for determining the maximum permissible bearing stress or load on the concrete floor
are given in the specification. These resultant values can be used to design the column base
plates, unless the concrete floor designer requires a larger bearing area.
The owner can initiate dialog between the storage rack registered design professionals and the
building designers to ensure that the strength of the floor, including, but not limited to, the
strength of the concrete, the thickness of the floor slab, the method of reinforcement, and the
quality of the subgrade is adequate for the storage rack loading. For bearing surfaces other than
concrete, special design is required and is beyond the scope of this standard.
ANSI MH16.1-2021 is for the design of storage racks only. Floor slab design is a separate
issue not within the scope of the specification.
Base plate design
General
This document contains three methods for calculating the required thickness of the column base
plates.
a)
downward vertical load;
b) uplift or tension force; and
c)
axial load plus bending.
Downward vertical force
The column base connections are designed to resist the forces and moments obtained from the
structural analysis. Actual field experience and limited testing has shown that base plates
thinner than those normally provided under hot rolled structural shapes designed in accordance
with ANSI/AISC 360 can meet these requirements.
Welds from the base plate to the column should transfer all loads.
Uplift or tension force
There are three ranges to consider while checking plate thickness for uplift. Refer to Figure C11.11.
Range 1: No prying action—the plate capacity is adequate and anchor forces are equal to the
applied force:
(C11.1-1)
𝜙𝑀𝑝 > 𝑇𝑢 × 𝑚
Range 2: Prying action—the plate capacity is adequate; anchor forces can increase above
applied forces due to prying:
𝑇𝑢 × 𝑚 > 𝜙𝑀𝑝 > 𝑇𝑢 ×
𝑚
2
(C11.1-2)
Range 3: Insufficient plate strength – select a thicker plate or change plate geometry:
𝜙𝑀𝑝 < 𝑇𝑢 ×
𝑚
2
(C11.1-3)
For uplift, an inflection point at half the distance from the nearest edge of the column to the
anchor location reflects reverse curvature bending of the base plate. For seismic design, it could
be preferable to demonstrate that the baseplate has adequate thickness to resist the design
uplift force in single curvature bending or a transition between single and double curvature. The
design forces used to determine the minimum thickness of the base plate are based on the load
combinations without overstrength.
Figure C11.1-1 – Visual representation of dimensions for 𝒎, 𝒑, and 𝒂
The effective bending arm in single curvature is from the anchor bolt centerline to the edge of
the rack column. The yield stress of the baseplate, 𝐹𝑦 × 1.1𝑅𝑦, is used to determine minimum
plate thickness to prevent prying action. The multiplier of 1.1𝑅𝑦 is from AISC 341 for maximum
deliverable force in seismic connections. These values deviate from the AISC Steel
Construction Manual prying action equations because column bases behave differently for
prying action than bolted flange connections for two reasons:
a)
bearing on concrete that is more compressible than steel; and
b) slip prior to follow-up expansion of torque-controlled anchors that does not occur in
bolted steel connections.
Axial load plus bending (down-aisle seismic or wind)
No commentary provided.
Column base plate connection rotational demand
The rotational stiffness of the base is modeled in the down-aisle frame analysis as a rotational
spring with stiffness 𝐾𝑏. The base moments, 𝑀𝑏, are determined from the structural analysis of
the down-aisle model. The rotational demand of the base (𝜃𝑏 ) is:
𝜃𝑏 = 𝑀𝑏⁄𝐾𝑏
(C11.1-4)
The equation given for base demand amplifies this moment by multiplying it by 𝐶𝑑 to increase Θ
to the design earthquake level. If the analysis model does not account for the amplified
gravity load drift, the 1 + 𝛼𝑠 factor is required as shown. Conversely, if the analysis considers
the amplified gravity load drift, the 1 + 𝛼𝑠 factor is not required because the effect would already
be accounted for. See C9.4.2 for discussion of the 1 + 𝛼𝑠 term.
When the ASD design method of analysis is used, the seismic forces that are applied to the
structure are only 67% of the forces that are applied using the LRFD design method. To
compensate for this difference, the base moment, 𝑀𝑏, should be multiplied by 1.5 for
computing 𝜃𝑏 when the ASD design method is used.
The rotational stiffness and the rotational capacity can be determined by tests.
Shims
Shims are commonly used to allow columns and uprights to be installed plumb and/or level and
to transfer the column loads to the supporting concrete floor slab. Some operational conditions
could result in the accidental displacement and/or dislodgement of an improperly secured shim
stack. The transfer of the column loads relies on the shim stack remaining in place. The integrity
of the shim stack can be maintained by a variety of methods including, but not limited to, friction,
nesting, interlocking, and/or welding.
A review of storage racks with shims installed in high seismic areas has demonstrated that the
overturning force in compression develops adequate friction to transfer shear forces through the
shim stack. However, such designs should be evaluated to ensure adequate friction can be
achieved when conditions warrant.
For empty rack subjected to wind forces, bending of the anchors should be investigated if
shim heights are expected to exceed a height greater than or equal to the anchor diameter.
Anchorage
Anchor bolt design
The proper anchor embedment is critical to the design capacity of the anchor. The effective
anchor embedment depth is defined as the final distance from the floor surface to the tip of the
anchor after it has been installed and tightened in accordance with the manufacturer’s
recommendations. The nominal embedment depth is the distance from the floor surface to the
tip of the anchor prior to tightening the anchor nut. Anchor capacities shown in manufacturer’s
tables often show a capacity corresponding to the nominal depth of the anchor, but the
installed depth needs only be equal to the effective embedment depth as established by the
anchor manufacturer. The final embedment depth can be affected by the thickness of the base
plate and the thickness of shims often required to plumb the rack uprights. The combined
thickness of the base plate and maximum expected shim pack should be considered when
determining the required anchor length.
The eccentricity reduction factor specified in ACI 318 for computing anchor strength on a group
of anchors in a baseplate is intended for those cases where one (or more) anchor(s) in the
anchor group is closer to the column centerline than other anchor(s). For those cases where
each anchor in the anchor group is the same distance from the centerline of the column, which
is usually the case for rack applications, the eccentricity for the anchor group can be taken as
zero. For asymmetric anchor arrangements, refer to ACI 318.
For a rack frame consisting of two columns and a horizontal brace close to the floor that is
subjected to cross-aisle seismic force, a combined tension and shear check on the anchors is
not needed for the anchors on the uplift side when it can be shown that the column, base plate,
and anchorage on the compression side is capable of resisting the total base shear of the
frame. When this assumption is made, the registered design professional should remember
that there will be additional moment in the column on the compression side due to the entire
frame base shear being transferred through that column.
Anchor bolt capacities are affected by their proximity to the edge of the concrete slab per the
anchor bolt manufacturer’s literature. The edge of a slab can include a free edge, slab edge
against soil, or slab edge against asphalt. In these cases, the edge of the slab might spall when
installing an anchor. Control, contraction, or construction joints are not considered an edge of a
slab, given there is concrete on both sides and the slab is prevented from spalling.
Overstrength design for anchor bolts
An overstrength factor, 𝛺0, is included in seismic load combinations for anchor uplift to ensure
that the base connection to the concrete has adequate capacity and ductility. Post-installed
anchors are to be designed for load combinations using an overstrength factor of 2.0, unless it
can be shown that a plastic hinge could develop in the plate which would limit the maximum
force that can develop in the anchors. The capacity-limited seismic load effect accounts for
strain hardening and material overstrength by applying 1.1𝑅𝑦 to the specified yield stress,
consistent with AISC 341 provisions for steel buildings. Refer to C11.1.2.3 for an explanation of
prying action. If it can be shown that the plate has adequate bending capacity in single
curvature, then double curvature bending is unlikely to develop and the maximum deliverable
force can be based on single curvature bending. It is acceptable to consider a case of partial
reverse curvature, where 0.67 < 𝑃𝑒 < 1, and a combination of plate yielding and bolt prying
occurs.
The anchor force will be less if the plate can be sized and the anchors properly spaced to
minimize or eliminate prying action.
Periodic inspection of anchor bolt installation
Periodic inspection of the anchor bolt installation can be required. An independent qualified
inspector should be sought to carry out this inspection. When such an inspection is needed,
only those anchors that are part of the main force resisting system need to be inspected. This is
because accessories on or around the rack system that are not part of the storage rack’s
structural design are not covered under this standard.
The following example is provided to offer possible guidance language for a periodic
inspection. This assumes the industrial steel storage rack is installed on a concrete floor
that is adequate to support the structure and is suitable for the anchor type being used.
This guidance is not mandatory.
Periodic inspection may be waived for anchors that have calculated factored uplift using
the LRFD method less than or equal to 1,000 lbf (4,500 N) or 50% of the uplift capacity
(when the uplift capacity is calculated using LRFD method). For the ASD method,
calculated uplift is less than 667 lbf. (3,000 N) or 33% of the uplift capacity (when the
uplift capacity is calculated using ASD method). Periodic inspection is typically waived in
Seismic Design Categories A, B or C.
The inspector shall deliver the required inspection report to the rack owner and other
interested parties, in an acceptable format.
The anchor bolt inspector shall be present prior to the installation of the anchors that
require periodic inspection. The inspector shall verify that the installer of the anchors is
installing the correct type and brand of anchor bolt that has been specified on the Load
and Rack Configuration (LARC) drawings or the rack installation drawings. The
inspector shall also ensure that the installer has a copy of the manufacturer’s installation
procedure for the anchor that is being installed.
The inspector shall visually inspect the anchor, drill, and bits to be used for the
installation to make sure they are correct and compatible with the anchor being
installed. The inspector shall ensure that the anchors provided are long enough to attain
the embedment specified on the LARC drawings, accounting for the base plate
thickness and the highest required shim stack.
The inspector shall observe and approve the installation of the first several anchors at
the base of the column or other member that is to be anchored. The installation shall be
done in accordance with the manufacturer’s installation instructions and the LARC
drawings. The anchors shall be tightened to the anchor bolt manufacturer’s
specifications. After the installation and approval of initial anchor bolt group, the anchor
bolt inspector shall allow the installer to continue with the installation of anchor bolts.
If there is more than one anchor bolt configuration, but the anchor size and type of
anchor are the same, the actual inspection of the installation of the anchor bolt need not
be repeated, but the other configurations (patterns) should be reviewed for compliance
with the LARC drawings. If the anchor sizes change, the bits for each size should be
reviewed for compatibility with the anchor. If there is more than one type of anchor used,
the installation of each type shall be observed and approved following all of the steps
above for each anchor type.
Subsequent inspections may be done at any time but shall be done when:

There is a request to change the type of anchor used during a project.

Changes in site conditions that can affect anchoring, such as rebar interference
or proximity to floor joints or edges, are observed. When modifications to the
installation of the anchor bolts are necessary, a qualified engineer shall review
the modification and ensure that the change will result in adequate anchorage of
the structural member.
Intermediate inspections should be done on projects with over 1,000 anchors.
Intermediate inspections are only needed to ensure that the installer is continuing to
properly install the anchor bolts, and that no new problems have been experienced
since the initial inspection.
Final anchor bolt inspection is required on all projects that require inspection. The
inspector should ensure that all anchors have been installed in their correct locations in
accordance with the LARC drawings and that the anchors have the correct embedment.
The special inspection is over once all of the anchor bolts have been installed and the
building official has accepted and approved the final inspection report.
Slabs and subgrade evaluation
Analysis of the slab and subgrade are outside the scope of this standard. FEMA 460 Appendix
D includes a variety of rational procedures from accepted engineering practice for the structural
evaluation of concrete slabs-on-grade with equipment loads.
C12
Special rack design provisions
Overturning
An important aspect of rack design is to provide stability against overturning of the rack
structure when the rack is subjected to horizontal forces. Horizontal forces on the rack structure
can be due to wind (see C7.3), earthquake (see C7.4), or the force described in this section.
The rack design should not consider the stabilizing forces provided by ordinary anchorage to
maintain rack alignment. However, if forces on anchors are analyzed and the anchors properly
designed and installed for these forces, then the anchorage can be considered in the stability
analysis.
A limit on the height-to-depth ratio of the rack is imposed. This ratio is defined as the height from
the supporting floor to the topmost loaded beam divided by the width (or the combined width of
interconnected frames) of a straight-leg style frame. While it is recommended that all frames be
anchored (see C11.3), if the 6 to 1 limiting ratio is exceeded, the rack must be analyzed for
overturning, even in the absence of seismic and wind forces. A 350 lbf (1,160 N) lateral force,
which could result from moving equipment servicing the rack, is applied at the topmost shelf
level for the purpose of designing the anchorage. This short duration load need not be
considered in the design of the column.
A further limit on the height-to-depth ratio is given as 8 to 1. Stabilizing a single row of rack that
exceeds this ratio with floor anchors alone is not recommended. Under certain circumstances,
this can be feasible, but such cases should be thoroughly analyzed and certified by a registered
design professional. When designing machine-loaded storage racks exceeding a height-todepth ratio of 8 to 1, registered design professionals should consider using cross-aisle ties (see
10.4.5) or connecting the storage rack upright to the building structure (see 12.2) to provide
additional load transfer members or structural redundancy.
The provisions of this section apply to frames of constant width over their height. Other
configurations such as offset or sloped legs require a more detailed analysis.
Sloped-leg frames and offset-leg frames are generally avoided in single rows of rack.
Interaction with buildings
The connection of racks to buildings, other than the floor, is not recommended. If a storage rack
system is connected to a portion of a building other than the floor, the storage rack system
could impose unacceptable forces upon the building, or the building could impose
unacceptable forces upon the storage rack. The design of connections between a storage rack
system and a building, other than a floor, is outside the scope of this standard. Consultation
between the registered design professional and the building structural engineer is
recommended to ensure all relevant forces are accounted for in both the building and the
storage rack system.
This section recognizes that building structures and rack structures are likely to have different
structural characteristics. During an earthquake, this could have a magnifying effect for
structures that are interconnected, but which have different periods of vibration. Thus, the
connections must be designed to ensure that neither structure causes damage to the other
during a seismic event.
The relative stiffness of racks and buildings varies significantly. Therefore, any attachment
between the rack and the building needs to include provisions for vertical and lateral building
movements. Such attachments need to be proportioned so that the attachment would fail prior
to causing damage to the building structure. Care should be taken that roof loads are not
transferred to the racks.
The 350 lbf (1,160 N) force originates from the applied horizontal force requirement that is
resisted to stabilize a single row of rack for the non-seismic case as defined in C7.6.
Pick modules and rack supported platforms
General
Pick modules are found in warehouse and distribution centers and allow rapid throughput of
product. They are customized multi-level racks that support one or more product storage bays
having a forklift aisle on one side and a pick aisle floor on the opposite side. Pallets or products
are generally inserted into a product storage bay from forklifts on the forklift aisle side and
removed by workers from the pick aisle side. The pallets can either be stationary in the product
storage bay or can flow toward the pick aisle floor.
Most pick modules are frame-beam style racks with integrated pick module walkways or
platform levels that are used by authorized or trained order picking personnel for the loading
and unloading of products. These structures are intended to be in an industrial distribution
environment and are not open to the general public. Pick modules are free-standing structures
within a warehouse. The pick module walkways have flooring, guardrails, stairways, and often
have conveyor systems that deliver and/or remove products. These structures should be
designed using the provisions of the specification. This section is intended to provide special
provisions for these structures that are needed in addition to the requirements of the rest of the
specification.
Rack-supported platforms have elevated levels like pick modules, but the platforms can be
more open and involve activities other than order picking.
Design requirements
The minimum pick module walkway design live load of 60 psf (2.9 kN/m 2) is specified to support
order picking personnel. The user should advise the registered design professional whether
there are to be such activities or equipment on the pick module floor that would require a higher
design load. Also, the conveyor live and product loads, dead loads and any other equipment or
fixtures that are on the platform floor should be considered (such as lighting, sprinkler piping,
etc.).
When the project specifications require a design live load of greater than or equal to 100 psf
(4.8 kN/m2) and there are two or more elevated floor levels, ANSI MH16.1-2021 allows the
registered design professional to reduce the live load by 20% for the design of the support
framing. The support framing includes the columns, the frame bracing, the frame bracing
connections and the base plates. It does not include the platform support beams and their
connections. It would be excessively conservative to require the columns (and support structure
members) to be sized for all of the floor levels having all of the live loads present at the same
time. This reduction only applies to the floor live load for the walkway areas. It does not apply to
other loads such as dead loads or product loads.
A more stringent limit on live load beam deflection is required for floor-supporting beams
because the L/180 limit used for rack beams can result in excessive deflection and cause the
floor to bounce. For this reason, a rack manufacturer’s beam capacity tables should not be used
to select floor beams for platforms without proper consideration of deflection. The deflection
from the total load cannot exceed L/180. The registered design professional can limit the total
deflection to L/240 or check the deflection separately for both cases.
A 30 in. (76 cm) minimum clear pick aisle width is recommended to allow the order pickers the
clearance to safely navigate the walkway and perform the picking operations.
Posting of design loads
The design loads for a rack-supported platform or pick module walkway should be on the LARC
drawings. The design loads should also be posted on the structure and serve as a reminder to
the users of the load limit for the pick module walkway or rack-supported platform.
Safety flooring
Safety flooring is a flooring surface provided in areas where order picking personnel might
need to step off the normal walking area or pick module walkway to dislodge loads that might
not have properly flowed to their correct discharging positions.
Pick modules often contain product flow lanes. Because unit loads can sometimes hang up or
not flow freely, safety flooring is recommended or required. Safety flooring is designed by the
flooring manufacturer with the following specifications:
a)
300 lb. (136 kg) concentrated load (to support the picker);
b) 60 psf (2.9 kN/m2) uniformly distributed load acting separately; and
c)
Any other requirements necessary to protect both the picker and pick module.
Owners should develop safe working procedures to ensure that order pickers avoid open or
unguarded edges of safety flooring unless they are utilizing fall protection devices. Owners
should consider establishing a distance of 4 ft (1.2 m), or the length of a typical pallet, as a
distance between order pickers and open or unguarded edges of safety flooring, or another
distance that conforms to the application. These procedures will vary depending on the
configuration of the structure and the working environment. ANSI MH16.1-2021 is not intended
to establish the exact procedures, as they can vary, but rather to stress the importance of
having safety procedures that are strictly followed. Under no circumstances should a picker
climb or walk into the rack when safety flooring has not been provided for that purpose.
Stairs, ladders, and guards
Pick modules and rack-supported platforms are unique storage structures where authorized,
trained personnel can access their elevated floor levels by using fixed stairs or ladders. The
unenclosed stairways, ladders and the vertical and horizontal guarding provided for these
structures are to be designed in accordance with the requirements outlined in ANSI MH32.12018, Stairs, Ladders, and Open- Edge Guards for Use with Material Handling Structures. This
standard serves as a reference document of design practices and operational requirements for
owners, users, designers, purchasers and specifiers of pick modules and rack-supported
platforms. The requirements in ANSI MH32.1-2018 differ from building code requirements,
however; the requirements provide adequate protection due to the structures’ low occupancy,
inaccessibility to the general public, and their intended usage restricted only to for material
handling and storage activities.
Kick plates (toeboards)
Kick-plates are vertical plates that extend upward at the edge of a floor surface to prevent loose
items from falling off the edge of a floor.
Pick modules are typically installed in industrial warehouses. In these environments, there exists
the risk that stored product or other objects can fall from an elevated floor level onto personnel
below along the floor perimeter or at floor openings. To help address the potential hazard of
loose items from sliding off the edge of a floor, OSHA requires that a toe-board be provided that
extends from the floor surface to a height of at least 3½ in. (8.9 cm) above the floor surface (see
29 CFR 1910.29 (k) (1) (ii)) for installations under the jurisdiction of U.S. regulations. The toe
board or kick plate is typically a non-perforated, vertical steel plate, angle or other barrier
installed at the edge of the elevated surface.
Conveyor floor openings
Pick modules typically accommodate full-case or split-case picking operations. They are
serviced by powered conveyors at the main aisles of each floor level which transport totes or
cartons to the ground- level for order fulfillment. Openings in the floor system are often
positioned to permit the passage of incline conveyors between floor levels.
In many cases, floor openings are designed to assist with the disposal of empty cardboard
boxes and other packaging material using trash take-away conveyors that are suspended
directly beneath the floor openings. These applications typically have one or more down-aisle
conveyors that are secured directly above the floor openings at a bed height of approximately
30 in. (76 cm) which, in turn, provide physical fall protection for employees working alongside
the floor openings.
Product fall protection
There can be systems in place to protect areas within or around the structure from products that
could accidentally fall. Often, these locations are areas where people could be situated, or areas
where falling product could cause other types of property damage or present a safety hazard.
These areas should be identified by the owner and brought to the attention of the registered
design professional. Proper barriers, if required, should be supplied and installed. These
requirements will vary depending on the products, the operation, and the configuration of the
structure.
Storage racks for automated storage and retrieval systems
Stacker racks are commonly classified as a special industrial occupancy category.
C13
Testing
Test methods
Many factors affecting the design of rack are difficult to account for analytically. This section
provides a series of optional tests that can be used to evaluate the effects of components on the
overall behavior.
Except as either modified or supplemented in the specification, requirements set forth in
ANSI/AISI S100 and ANSI/AISC 360 apply to the testing of components.
A critical aspect of any testing program is repeatability. Test specimens representative of the
actual product should be collected, and test methods should be followed precisely with the goal
of producing repeatable test results. It is important to note that different manufacturing methods
can produce materials that will exhibit different properties and produce different results.
It is also important that tensile coupons be taken from each specimen to determine the actual
yield stress. Generally, the actual yield stress of the steel is higher than the specified minimum
yield stress. It is important to know the actual yield stress in order to analyze the test results. It
is also essential to have a complete report spelling out the test procedures, the results, and the
analysis of the results.
Stub column tests for cold-formed and hot-rolled
columns Purpose
No commentary provided.
Test specimen and procedure
It is acceptable to interpolate the 𝑄-values linearly for a series of shapes with identical crosssection and perforation dimensions, but with a variety of thicknesses. For this purpose, 𝑄𝑚𝑎𝑥 and
𝑄𝑚𝑖𝑛 should be determined from stub column tests on specimens made with the maximum and
minimum thicknesses of coil from which the stub column was made. This correction is necessary in
order to avoid unsafe design in case the virgin yield stress (before forming) of the specimens was
significantly higher than the specified minimum.
It is possible for the test results to yield a 𝑄-value greater than 1.0. This could occur if the
neglected strengthening effects of cold-work outweigh the weakening effects of the perforations.
However, guidance in ANSI/AISI S100 states that when a 𝑄-value greater than 1.0 is obtained
in testing, 𝑄 = 1.0 is to be used in subsequent calculations.
Evaluation of test results
The equation for 𝑄 in ANSI MH16.1-2021 differs from the equation from previous editions.
Previous editions of ANSI MH16.1 used 𝐹𝑦 multiplied by 𝐴𝑛𝑒𝑡𝑚𝑖𝑛 in the denominator. In ANSI
MH16.1-2021, the denominator was changed to 𝐹𝑦 multiplied by 𝐴𝑛𝑒𝑡𝑔. This change is made
because Section 8 now uses this definition.
Pallet beam
tests Purpose
In this section, depending on the information required, two different types of tests are
specified (i.e., simply-supported pallet beam tests and pallet beam in upright frame assembly).
The loading in these tests is applied by means of a test machine or jacks. This loading can
restrain the torsional distortions and hence, can lead to unconservative results for members
subject to such distortions.
The beam test methods illustrated do not account for impact. However, in practice, test results
will have to be adjusted to consider the added impact effect.
Simply-supported pallet beam tests
This test can also be used in the design of beams, in general, when the end restraint is deemed
not to lead to significant increase in the load carrying capacity.
In the determination of yield moments, the number of tests needed is determined in accordance
with ANSI/AISI S100.
Test setup
The value of 𝐶 is set between 2.5 and 3 to avoid shear failure and to ensure a sufficiently long
portion with constant moment.
For most pallet beams, the end connection detail is such that the beam can be placed directly
on the supporting surface and have simply supported end conditions. In this case, the clamps,
diaphragms, or stiffeners at the supports most likely will not be needed.
Test procedure
It is good practice to plot load versus mid-span deflection readings at each load increment
during testing. Noticeable deviation from straightness of such a plot will indicate incipient
inelastic behavior or local buckling or crippling. When such is the case, load increments are
reduced to no more than one-half the initial increments. It is also good practice, though not
required, to measure permanent set for loads within the interval of ±25% of the expected design
load by reducing, within this interval, the ratio of the applied load to the initial load after the
increment. Appropriate gage readings shall be taken at this reduced load to determine
permanent set.
When deflection increments for given load increments increase rapidly, this indicates the
approach of ultimate failure load. If sudden failure is possible by the nature of the specimen, and
if such sudden failure could damage the gages, they should be removed. Alternatively, if a
gradual failure is expected, such as by simply yielding, it is desirable to measure the last center
line deflections right up to and past the maximum or ultimate load, to obtain some part of the
descending portion of the load deflection curve.
Evaluation of test results
No commentary provided.
Pallet beam in upright frames assembly
tests Purpose
No commentary provided.
Test setup
This test specifies that the upright frame is not to be anchored to the floor even if the actual
racks are anchored to the floor. The test is intended to represent the behavior of the rack
between the inflection points. Therefore, any restraint at the column bases other than due to the
pressure should be avoided.
It is important to minimize friction between beams and pallets because new, dry pallets on new,
dry beams, when used in the test, could provide considerably more bracing than pallets and
beams worn smooth in use and possibly covered with a film of oil or other form of lubrication.
If loads are applied by pallets or other devices resting on beams, it is important that friction
between pallet and beams be reduced to the minimum possible amount by greasing or other
means. (This is suggested because new, dry pallets on new, dry beams when used in the test
could provide considerably more bracing than pallets and beams worn smooth in use and
possibly covered with a film of oil.)
The minimum instrumentation for such tests consists of devices for measuring the deflections of
both beams at mid-span relative to the ends of the beams. One way of doing this is to attach a
scale graduated to 0.01 in. (0.25 mm) at mid-span of each beam and to stretch a tight string
(usually a string with a rubber band at one end) or wire attached to each end of the beam.
Another way is to use dial gages at mid-span and at each end of the beams. Transits are
permitted to read scales located at mid- span and at the end of the beams.
Additional instrumentation, such as strain gages or additional dial gages at the ends of the
beam, is required only if special problems are to be considered. For highly unsymmetrical
beams, e.g., deep channels or C-sections, measuring rotation under load is advised. This is
most easily done by rigidly attaching a protractor of sufficient size to the beam at or close to
mid-span. A vertical string weighted at the end and acting as a plumb is then read against the
protractor at every load increment.
Test procedure
No commentary provided.
Evaluation of test results
General guidelines given in C13.1 are to be used in addition to the following three particular
requirements or criteria for determining allowable load. The first of these is the determination of
the factor of safety or the resistance factor specified in ANSI/AISI S100, Section K.
The second criterion by which to determine allowable loads from the test results prescribes a
safety factor of 1.5 against excessive load distortion.
Number of tests required
No commentary provided.
Deflection test
The third and last criterion limits deflection of beams under design load to 1/180 of the span. To
satisfy this requirement, the load that results in this amount of deflection should be read from
the load deflection curve plotted from the test results. If this load is smaller than those obtained
from the first two requirements, it governs.
The cantilever test
The Cantilever Test provides a simple means of determining the connection moment capacity
and rigidity. However, it has the disadvantage that the ratio of shear force (i.e., the vertical
reaction) to moment at the joint is not well represented. For typical rack connections, this ratio is
likely higher than it is in the cantilever test.
In general, a higher ratio would probably lead to a more rigid connection. However, bending
moment and shear force would interact and lower the ultimate load of the connection. This
effect should be studied by reducing the length of the cantilever to the distance between the end
of the beam and the expected location of the inflection point.
Cyclic testing of beam-to-column
connections Purpose
The purpose of this test is to establish the moment-rotation characteristics (dynamic spring
relationship) of a rack beam-to-column connection and to determine its strength, stiffness, and
rotational capacity.
RMI, working with and through other codes and standards organizations such as Building
Seismic Safety Council (BSSC), International Code Council (ICC), American Society of Civil
Engineers (ASCE), National Fire Protection Agency (NFPA), and others, have advocated to
address industrial steel storage racks as building-like non-building structures. Industrial steel
storage racks designed, permitted, and installed in accordance with ANSI MH16.1 have
performed well in actual seismic events, which lends credibility to RMI’s efforts.
ANSI MH16.1 references provisions and guidance outlined in the National Earthquake Hazards
Reduction Program (NEHRP).
The testing procedures in this section are analogous to those in the AISC 341. However,
because of the much higher drifts typical of storage racks, the rotational demands and
associated capacities in high seismic areas can be several times larger than those required in
the AISC 341. This test method specifically evaluates structural beam-to-column connections for
storage racks in a testing laboratory. This test method mimics the test procedures developed
for connection properties of hot-rolled structural connections in FEMA 350, ANSI/AISC 341,
ATC 19, ATC 24, and the SEAOC Blue Book. This test method can be used for either coldformed or hot-formed storage rack components.
Test specimen
The test specimen replicates, as closely as is practicable, the pertinent design, detailing,
construction features, and material properties of the prototype. The test specimen should
replicate sources of inelastic rotation, material strength, size of members, connection details,
welds, and bolts present in the finished product.
Extrapolation beyond the limits of any component of the test specimen is subject to qualified
peer review and approval by the AHJ.
Test setup
No commentary provided.
Test procedure
This section presents a testing and evaluation protocol intended to evaluate the characteristics
of typical rack beam-to-column connections. These tests are to be executed on behalf of each
storage rack manufacturer in order to determine and evaluate the moment/rotation stiffnesses
and their limiting values for their various beam-to-column connectors. This testing protocol is
based on FEMA 350 Table 3-14 scaled up by a factor appropriate for rack beam-to-column
connectors. These characteristics, when evaluated in a dependable and reproducible manner
by an independent testing laboratory, will then become the basis for the removal or modification
of the present the cap on the rack structural period. A more reasonable period value will be
used to calculate a more reasonable prediction of rack structural behavior, including drift, which
is more representative of the response of real systems in the field under seismic conditions.
Typical rack behavior will be tested with beam-to-column rotations of up to 0.1 radians, with up
to five cycles, and will be representative of rack structures having displacements resulting in
drift of ℎ/50. Following the last cycle of the cyclic tests, the moment/rotation behavior will be
recorded to failure where the rotation will be on the order of 0.3 radians.
Rack beam-to-column connectors normally exhibit a large degree of ductility in response to
demand placed on such connections. For example, assuming a drift index of 0.02 (ℎ/50), which
is about the most ever seen on a shake table, the demand rotation would be 0.04 radians. This
is because shake tables have not had the displacement capacity to test actual earthquake
motions in the 2 to 4 second period range. However, rack connections can achieve failure
rotations of 0.2 to 0.3 radians, some ten times the drift index. Comparing this to a building
structure, the Uniform Building Code requires that joints accommodate a drift of 0.0025 at 0.03
radians for a ductile frame, and around 0.015 for an “ordinary” moment frame, which is six times
the building drift. Rack connections generally exhibit more ductility than any representative
building connection. This capacity is needed since demand on rack connections is many times
the demand on building structural connections, so it is possible for a rack connection with a
capacity of 0.10 radians to be inadequate.
Evaluation of test results
The beam-to-column connection cyclic test is used to determine the moment strength and
inelastic rotational capacity of the rack beam-column connection. The design moment is to be
determined using the test method outlined in 13.6. Other methods that lead to comparable
results are acceptable.
The results of the beam-to-column connection cyclic test determine the median value of drift
angle capacity for the performance states of strength degradation and ultimate drift angle
capacity. The test results also determine the beam-to-column moment-rotation characteristics
and dynamic spring relationship for each of the connection member combinations tested.
Column base fixity testing
Purpose
No commentary provided.
Definitions
No commentary provided.
Precision
No commentary provided.
Test specimen fixture and setup
A column base fixity specimen and setup is illustrated in Figure C13.6-1 and Figure C13.62.
Figure C13.6-1 – Photo of column base fixity test setup
Figure C13.6-2 – Photo of column base fixity test setup
Test procedure
ANSI/AISI S100 Section K2 has provisions for strength – the tests here also consider rotation
and thus stiffness. Another peculiarity of ANSI/AISI S100 is that it is related to LRFD only.
Evaluation of test results
No commentary provided.
Static testing of frame bracing connections
An upright frame analyzed assuming brace to column joints as rigid is found to be much stiffer
than the actual frame. The cause of the difference is the flexibility of the braces in the axial
direction of the braces resulting from the local distortions. The moment rotation flexibility at the
joints do not influence the behavior to a significant extent. The flexibility of the joints influencing
the overall behavior is to a much larger extent from the extensions due to the distortion of the
column section in the direction of the braces2,3. The determination of the axial flexibility of the
joints is the aim of the tests prescribed.
This provision applies to tests to determine the rotational stiffness and strength of upright frame
column to brace joints. The information obtained from these tests is intended to be used in
calculating the in plane lateral stiffness of upright frames. An example of a short upright frame
is shown in Figure C13.7-1. The stiffness and strength of the joints determined by the tests
prescribed can be used in the determination of the overall strength and stiffness of upright
frames. As shown in Figure C13.7-1, the braces can be joined to the columns at right angles or
diagonally. Joints at 45-degree angles are illustrated in the figure. The tests procedures cover
both of these possibilities.
2 Roure, F., Peköz, T., Somalo, M.R., Bonada, J., Pastor, M.M., Segura, A., “Cross-aisle
stiffness analysis of industrial welded cold-formed steel rack upright frames”, Thin-Walled
Structures, August 2019, Pages 332-344.
3 Roure, F., Peköz, T., Somalo, M.R., Bonada, J., Pastor, M.M., Segura, A., Casafont, M.,
“Design of industrial cold- formed steel rack upright frames for loads in cross-aisle direction”,
International Conference on Cold-Formed Steel Structures, 2016.
Figure C13.7-1 – Front and cross section views of a short upright
frame
In evaluating the test results, care should be taken to separate the effect of local distortions
from those due to the overall deflections of the test specimens.
Figure C13.7-2 and Figure C13.7-3 show the minimum number of displacement sensors to be
provided. Details of test fixtures are given in the photographs in Figures C13.7.2 through
C13.7.6
Figure C13.7-2 – Diagonal brace test setup
Figure C13.7-3 – Diagonal brace test setup
Figure C13.7-4 – Horizontal brace test setup
Figure C13.7-5 – Horizontal brace test setup
Figure C13.7-6 – Spherical joint pin for rotation capacity around the three axes shown
As shown in Figure 13.7-1 (left) in the specification, for conditions where the brace is in tension,
the hydraulic jack and load measuring device has a spherical pin joint on the top and bottom.
This assures avoiding any damage to the hydraulic jack and load measuring device.
As shown in Figure 13.7-1 (right) in the specification, for conditions where the brace is in
compression, the hydraulic jack and load measuring device top is fixed to frame (without a
spherical pin) and only the bottom has a spherical pin joint. The brace has a lateral restraint in
both directions (in plane and out of plane). This assures avoiding any damage to the hydraulic
jack and load measuring device
Cyclical testing of upright frame bracing connection
This section provides a procedure for determining the cyclic test capacity of specific brace
connection designs for use in seismic applications. The cyclic test capacity is generally
significantly less than the capacity obtained from static tension and compression tests.
The cyclic testing also provides determination of connection stiffness that can be used in the
braced direction.
The measured nonlinear stiffness and hysteretic properties from these tests can also be used to
evaluate the non-linear dynamic seismic performance of racks using advanced analysis tools. A
long-term objective of the RMI is to develop procedures for establishing verifiable procedures for
establishing the seismic capacity of racks based on the cyclic properties of specific connection
designs in the cross-aisle direction similar to that done in the down-aisle direction. These
advanced analyses can also be used to verify or revise the 𝑅 factor values used in code-based
design analysis of storage rack. The 𝑅 factor values are currently established by engineering
judgement and historical precedent.