SEISMIC BRACING OF HVAC SYSTEMS FOR LDS TEMPLES
12 APRIL 2013
KDK ENGINEERING
KEVIN COUCH, DAVID DE KOCK, KIRSTEN HINDS AND JASON HIRSCHI
DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND TECHNOLOGY
BRIGHAM YOUNG UNIVERSITY
EXECUTIVE SUMMARY
Seismic bracing of ducts and pipes has become a standard requirement for most modern buildings, but it
is often not installed correctly or completely overlooked. The Church of Jesus Christ of Latter-day Saints (LDS) is,
therefore, concerned with ensuring that all necessary components in their structures are correctly secured to
ensure the safety of its members and continued use of the structure after a seismic event. The details, bracing
length constraints and specifications in this project address this problem in providing clear requirements to be
adhered to for bid submittals and construction. This will allow the LDS church to equally compare bid submittals
and inspect construction according to these requirements.
Recommendations for specifications were provided to clarify and state requirements regarding the
American Society of Civil Engineers (ASCE) 7-10 Chapter 13, submittals and force design, bracing and spacing
requirements. Various details for ductwork bracing were produced in reference with ASCE 7-10 and Sheet Metal
and Air Conditioning Contractors’ National Association (SMACNA) including rectangular transverse, round
transverse, longitudinal and equipment bracing. These generic details provide a template for contractors
submitting designs of the details required. Lastly, brace spacing requirements were specified according to ASCE 710 and recommendations from professional engineers. These provide maximum allowable spacing between braces
to ensure consistent and sufficient designs.
This report, which deals specifically with LDS temple structures, is expected to be used as a guideline for
design professionals when specifying the seismic requirements of all ductwork for LDS temple projects. Design
engineers specializing in seismic restraint, mechanical contractors, and seismic design standards and codes were
consulted in the formulation of the guidelines that comprise this report. When used in the creation of seismic
bracing specifications, this project will assist in ensuring that the seismic bracing of LDS temple ductwork and its
associated components is performed in a high-quality, predictable, and consistent manner.
TABLE OF CONTENTS
Executive summary ....................................................................................................................................................2
Introduction ...............................................................................................................................................................4
Design ........................................................................................................................................................................5
Specifications .........................................................................................................................................................5
Details ....................................................................................................................................................................7
Minimum Bracing Design .......................................................................................................................................8
Conclusion .................................................................................................................................................................9
APPENDIX A .............................................................................................................................................................10
APPENDIX B..............................................................................................................................................................11
INTRODUCTION
The Church of Jesus Christ of Latter-Day Saints (LDS) is continually announcing and constructing new
temples around the world. There are 140 temples currently in operation, 12 under construction, and 16
announced. As these new temples are built, they are used daily for worship, and therefore, built according to the
highest standards. The mechanical system seismic bracing is important to maintaining a functional building and
reducing damage after a seismic event. Our team provided the LDS church with a guideline for the creation of a
seismic restraint specification section as well as standard details drawn in Revit, to ensure that proper seismic
bracing is provided in newly constructed temples as well as retrofits.
Without standard specifications and details specific to the seismic bracing of LDS temples, it is difficult for
the LDS church to compare designs and costs provided by various contractors due to the varying methods of
design. The church has also encountered problems with ensuring that seismic bracing has met their expectations.
These specifications and details allow all parties to be informed of what is expected in a project's seismic bracing
design and installation, prior to bid and for the duration of a project. The LDS church will be able to clearly
communicate their requirements and expectations and receive equally satisfactory bids that can be compared
against specific standards for inspecting completed work.
The details consist of standard Revit drawings of square and round ductwork bracing for transverse and
longitudinal applications, as well as the bracing of hanging equipment. There are also details and an associated
table containing minimum bracing lengths for longitudinal and transverse bracing as well as the combination of
both. The specification document contains lists of specific items an engineer needs to include in the seismic
bracing specification section along with a table listing the Ap and Rp values of the various duct types and sizes.
Current standards practiced and maintained within the professional community as well as specific seismic
design codes were thoroughly consulted and referenced in the guideline and details created. Specifically, The
International Building Code (2012) and ASCE 7-10 Chapter 13 with reference to SMACNA Seismic Restraint Manual
(third edition), and the Practical Guide to Seismic Restraint (second edition) by the American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE) were used.
It is our intention and hope that this guideline and the standard seismic bracing details will be used to
assist design professionals in creating seismic restraint specification sections for LDS temple projects. These will
meet the specific needs and expectations of the LDS church by providing effective mechanical system seismic
bracing of all temples, past and future.
DESIGN
In preparation for the design portion of this report, each team member familiarized themselves with the
necessary seismic design codes and standards namely, ASCE 7-10, SMACNA, and ASHRAE. Once the code was
understood, the team met with John Masek and Enoch Eskelson from International Seismic Application Technology
(ISAT). John Masek is the senior structural engineer at ISAT and Enoch is the operations manager. ISAT was not
only a tremendous technical resource, but also accompanied the team on a tour of the print and distribution
facility of the LDS church which is currently undergoing a seismic restraint upgrade. The team also met with Dave
Halverson from Halverson Mechanical, a mechanical contractor with extensive experience with HVAC demands of
LDS temples. Both ISAT and Halverson mechanical helped us gain an understanding of current practices,
shortcomings in the industry, and specific applications for LDS temples. The team also learned to use MathCad and
Revit to create the details and maximum spacing specifications.
With an understanding of the code, current practices, and the design requirements for LDS temples, the
team became equipped to make recommendations for the formulation of a seismic restraint specification and the
creation of some typical seismic restraint designs that can be included in the construction drawings.
SPECIFICATIONS
Specifications are an important way to ensure that a project in a seismic area is constructed as planned. A
list of recommended specifications was produced in this project to be included in a specification document for the
design and construction of a temple for the LDS church. These recommendations have been compiled from various
sources including: ASCE 7-10, IBC, and recommendations from professionals practicing within the industry. These
recommendations should be used in order to clarify the code and to ensure all parties involved understand
expectations. The specifications are currently not complete and may contain internal notes for future reference as
the document is completed. The full list of specifications may be viewed in Appendix A.
The specifications are arranged in five categories for ease in organizing and better understanding their
context. They are arranged into five categories: General/ Definitions, Submittals, Design of Forces, Bracing, and
Connections. This may not be the organization chosen when generating the actual specification document. These
categories cover clarifications of definitions and rules from ASCE 7-10, required submittals, and requirements
regarding the design of forces, braces and connections. Specifications that were specifically noted as important are
discussed below.
The General/Definitions section assigns liability requiring that a contractor abide by ASCE 7 and IBC. The
specification clarifies inspection requirements to ensure compliance. These requirements include inspections presubmittal, prior to cover up and at completion. It is also recommended that inspections be required at regular
intervals. This section also contains a list of acceptable seismic restraint manufacturers to ensure that the seismic
braces are certified.
Several rules or guidelines in the code have room for interpretation to accommodate various situations.
These need to be stated in the specifications so that the interpretation of the code meets the expectations of the
LDS church in their seismic bracing. As stated in ASCE 7-10 13.6.7, all ductwork designs to carry toxic, highly toxic
or flammable gases or used for smoke control must be braced. A specific definition of toxic was suggested as a
specification to ensure that all ducts posing as a health hazard if released are braced. A similar variation in
interpretation is seen in the 12 inch (in.) rule in ASCE 7-10 13.6.7.1b that states if the, "ductwork is supported by
hangers and each hanger in the duct run is 12 in. or less in length from the duct support point to the supporting
structure," it is exempt from being braced. The 12 inches can be interpreted differently, and while it isn't explicitly
stated, it must be less than 12 in. for the full run of duct otherwise the duct isn't being braced properly. Therefore,
we further defined the 12 in. rule in the specification to clarify what specifically classifies under this rule and that it
must be on the full run of duct.
The required submittals are detailed to ensure equivalent submissions. It is specified that the design must
be project specific and stamped by an engineer in the state of construction. This guarantees that the engineer is
licensed in the state of construction and qualified to sign off on the requirements of that state. Project specific
plans discourage general submissions lacking any calculations for the specific project. It is also recommended that
they require them to state the exact location of braces on the plans and indicate the types. In designing the forces,
it is specified that the brace capacity must be calculated to include the dead load as well as the seismic load. This
may seem to be an apparent requirement but it must be stated so as to ensure that the duct is not being under
braced. The Ap and Rp values for calculation of the forces on the duct are included in the specifications and can be
seen in Table 1.
Table 1: Assigned Ap and Rp values
Duct Type
Ap
Rp
Air-side HVAC, fans, air handlers, air conditioning units, cabinet heaters, air
distribution boxes, and other mechanical components constructed of sheet
metal framing
2.5
6.0
Wet-side HVAC, boilers, furnaces, atmospheric tanks and bins, chillers, water
heaters, heat exchangers, evaporators, air separators, manufacturing or process
equipment, and other mechanical components constructed of highdeformability materials
1.0
2.5
Suspended vibration isolated equipment including in-line duct devices and
suspended internally isolated components
2.5
2.5
Ductwork, including in line components, constructed of high deformability
materials, with joints made by welding or brazing
2.5
9.0
Ductwork, including in-line components, constructed of high or limited
deformability materials with joints made by means other than welding or
brazing
2.5
6.0
Ductwork, including in-line components, constructed of low deformability
materials, such as cast iron, glass and non-ductile plastics
2.5
3.0
The bracing section of the specification discuses rules and exceptions for bracing the HVAC ducts. The
bracing exceptions can also be seen on plan sheet DT-04. This section states that if transverse bracing is used as
longitudinal bracing it must be designed for those loads (DT-01). Also, it requires a maximum of 45 degrees
measured from the horizontal for bracing and prohibits the use of cable and rigid braces on the same run. These
and other specifications provide specific guidelines on designing and constructing the seismic braces. They ensure
common submittals that are easily compared and that the code is being upheld during construction.
DETAILS
Standardized details are included to ensure all parties involved have a proper understanding of what is
expected and to ensure proper installation. This is not an exhaustive list and is to serve as a guideline. Each detail
will need to be modified to the specific needs of each individual project. The details were compiled using various
sources as reference such as ASHRAE, SMACNA, and the structural engineer at the LDS church over temple
projects, Brent Maxfield. A Revit file for each drawing was included with the final report to ensure that any
necessary project specific adjustments can be made. Figure 1 displays a longitudinal brace detail and Figure 2
contains a transverse brace detail for a rectangular and round duct.
Figure 1: Longitudinal Brace
Figure 2: Transverse Bracing of Round and Rectangular Ducts
Once an adequate level of proficiency in Revit was attained, the team spent time deciding what types of
details might best represent the needs for a temple project. The team consulted with seismic bracing professionals
familiar to the LDS church such as ISAT and Halverson Mechanical, as well as the details found in the SMACNA and
ASHRAE seismic design manuals. Once details were selected as potential options, we consulted with Brent
Maxfield and narrowed down the list of details. Our team then had a specific list of details that best represented
what a design professional might need to include in the drawings of a temple project. These drawing were then
created in Revit, in transverse and longitudinal views.
MINIMUM BRACING DESIGN
When designing seismic braces of ductwork, there are many different factors that must be considered to
ensure proper performance in the event of an earthquake or other natural disaster. It is necessary for the
structural engineer to determine the proper spacing of seismic braces to ensure the strength is adequate. The
governing limit state which determines the brace spacing must be determined from the following:
•
•
•
•
•
Duct Brace Spacing Schedule
Capacity of the structure to resist brace load
Connection strength of the brace to the duct
Brace capacity
Capacity of duct to span between braces
The Duct Brace Spacing Schedule is a table which provides maximum transverse and longitudinal brace
spacing depending on the seismic acceleration input. This table provides maximum values that cannot be exceeded
even if the capacity of the other limit states allows it.
Once the maximum transverse and longitudinal brace spacing is calculated, the actual locations of the
braces on the ductwork must be determined. Often, ductwork bends and changes direction, leading to
complicated labyrinths of ductwork. When this occurs various rules must be followed to ensure proper seismic
bracing.
Due to the complexity of ductwork systems it is essential for these rules to be clear and include drawings. One of
the rules states, “If a straight run of ductwork has less than two support points, is connected to a braced straight
run of ductwork at each end, and its total length is less than two duct widths, brace across the run by adding its
length to the transverse and longitudinal brace design of the connected runs. If its length is greater than two duct
widths, a support point with a transverse brace is required.” This rule is not easily understood with one reading
and to ensure the interpretation is consistent, Figure 3 is provided. A complete list of rules and figures for the
determination of brace spacing can be found in Appendix B.
Figure 3: Drawing to Clarify Brace Spacing Rule
These rules were developed using ASCE 7-10, ASHRAE, and SMACNA. They were also reviewed by John Masek of
ISAT to ensure correctness.
CONCLUSION
The team met the sponsor’s needs by providing details for seismic bracing, a specification outline and
developing a system for determining brace spacing. This project has been performed in consultation with licensed
structural engineers, SMACNA and ASHRAE seismic design manuals and ASCE 7-10. These deliverables will assist
the LDS church in standardizing bids received so that a fair comparison can be made. They will also help to ensure
that design and installation of ductwork seismic bracing will be done properly according to the latest seismic
design standards.
The specifications and details provided are not meant to be a comprehensive list. It is suggested that
connection details would be added to the standard details. The specific seismic bracing requirements will need to
be developed according to the needs of each project. When used properly, these deliverables will effectively
communicate the expectations of the LDS church and ensure the proper seismic bracing of all current and future
temple projects.
APPENDIX A
STANDARD SPECIFICATIONS
RECOMMENDATIONS
______________________________________________
General/Definitions
Define Toxic (ex. Natural gas, flammable, poses health hazard if released).
Furnished engineering and materials should meet the requirement of seismic design of supports
and attachments of systems.
Materials shall be in conformance with national recognized standard ASCE 7-13.6.5.4.
The seismic restraint of nonstructural components shall meet the requirements of ASCE 7. If the
component in question is exempted by Section 13.1.4 of ASCE 7, a submittal noting that seismic
restrain of the particular component is not required.
The following seismic restraint manufacturers are accepted:
o Vibro-Acoustics
o International Seismic Application Technology(ISAT)
o Amber/Boothe
o Mason Industries Inc. (M.I.)
o Kinetics Noise Control Inc (K.N.C.)
o Vibration Mounting & Controls, Inc.
Clarify special inspection requirements included in bid specs.
Specify inspections are required in regular intervals (recommended: time of construction/5 or
every other week).
Inspections must be performed at least pre-submittal, prior to cover up and at completion.
Comply with applicable requirements as in ASCE 7 Table 13.2-1.
Default Ip=1.25 unless otherwise specified or required.
Submittals
Must submit calculations by a structural engineer specific to the project to be reviewed by
consulting structural engineer.
Drawings and calculations that take into account relative displacements are required.
Don’t require certification of components with Ip=1.5 if it does not contain hazardous
substances, as per ASCE 7-13.2.2.
Drawings shall specify anchor bolt type, embedment, concrete compressive strength, minimum
spacing between anchors and minimum distances of anchors from concrete edges. All anchor
ICC certifications shall be submitted.
Project-specific design prepared by a registered design professional in state where the project is
being constructed and manufacturer’s certification of component seismic qualifications that
meet the requirements are required.
Each contractor responsible for the installation of Designated Seismic Systems must submit a
“Statement of Responsibility” as required by section 1706.1 of the IBC 2006, prior to beginning
work on the system or component.
Submittal document must include a “Basis for Designing” or “Design Criteria” which includes a
statement from the registered design professional that the design complies with the
requirements of the ASCE 7-05, chapter 13 and IBC 2009 Chapter 1912/ACI 318(concrete
anchors).
Submittals must include seismic bracing layout drawings indicating the location of all seismic
restraints. The submittal package must include seismic restraint details providing specific
information relating to the materials, type, size, and locations of anchorages; materials used for
bracing; attachment requirements of bracing to structure and component, and locations of
transverse and longitudinal sway bracing and rod stiffeners.
Catalog cut sheets and installation instructions shall be included for each type of seismic
restraint used on equipment or components being restrained.
Submittal drawings and calculations must be stamped by a registered professional engineer in
the state where the project is being constructed who is responsible for the seismic restraint
design. All seismic restraint submittals not complying with this certification will be rejected.
Design of Forces
The component Ip values must be specified by item by the engineer.
The system shall be designed such that it will not transmit isolated vibration to the structure
(isolators).
Thermal Expansion, Isolation and Thrust Forces shall be considered in design.
The various utilities will coordinate so as to ensure displacement won’t cause failure to other
components.
Design must include seismic loads in conjunction with dead loads as required by the IBC/ASCE 7.
Design must consider flexibility as well as strength, as per ASCE 7-13.2.4.
The force Fp shall be applied independently in at least two orthogonal horizontal directions,
except where non-seismic loads on nonstructural components exceed Fp, such loads shall govern
the strength design.
Duct Type
Air-side HVAC, fans, air handlers, air condiConing units, cabinet
heaters, air distribuCon boxes, and other mechanical components
constructed of sheet metal framing
Ap
Rp
2.5
6.0
Wet-side HVAC, boilers, furnaces, atmospheric tanks and bins, chillers,
water heaters, heat exchangers, evaporators, air separators,
manufacturing or process equipment, and other mechanical
components constructed of high-deformability materials
1.0
2.5
Suspended vibraCon isolated equipment including in-line duct devices
and suspended internally isolated components
2.5
2.5
Ductwork, including in line components, constructed of high
deformability materials, with joints made by welding or brazing
2.5
9.0
Ductwork, including in-line components, constructed of high or limited
deformability materials with joints made by means other than welding
or brazing
2.5
6.0
Ductwork, including in-line components, constructed of low
deformability materials, such as cast iron, glass and non-ducCle
plasCcs
2.5
3.0
Bracings
The 12 inch rule must be explicitly defined or not allowed. Recommended wording for explicitly
defining 12 inch rule:
o Seismic restraints are not required on HVAC ducts suspended from hangers that are 12
inches or less in length from the top of the duct to the supporting structure and the
hangers are detailed to avoid significant bending of the hangers and their connections.
Duct must be positively attached to hangers within 2” from the top of the duct. Hanger
rods shall not be constructed in a manner that would subject the rod to bending
moments (swivel, eye bolt, or vibration isolation hanger connection to structure are
required to prevent bending moments when utilizing this exclusion). Displacement of
the component shall not cause damaging impact with other utilities or the structure.
Flexible connections are required between unbraced systems and equipment to
accommodate differential displacements. Where HVAC systems Ip>1.25, this exclusion
shall not apply (per ASCE 13.6.7).
If transverse braces are used to brace longitudinally, they shall be designed for both the
longitudinal and transverse forces.
Rods must be stiffened such that the Euler buckling strength will not results in buckling.
Specifications may include a minimum length required to be braced for the project.
All isolation materials, flexible connectors and seismic restraints shall be properly certified and
shall be from the same vendor.
Inline items greater than 75 lbs. shall be braced separately.
Cable restraints must always be straight and may not bend around obstructions.
Braces shall be a maximum of 45° from the horizontal or 60° if braced twice as often.
The bracing loads on the structure shall be coordinated with the structural engineer.
When using vibration isolator’s cable bracing shall be used.
Multi-tiered racks shall be stiffened.
Attachment of brace to duct must provide a positive load path to structure. Seismic bracing
details shall clearly indicate positive load path.
Cable and rigid braces shall not be combined on one run.
Seismic restraints shall not inhibit isolation systems.
Duct:
Where duct Ip=1.25, brace all rectangular duct greater than and equal to 6 ft2, all round
duct greater than 33” dia.
o Where duct Ip>1.25, brace all duct > 5lb/ft.
Equipment items installed in-line and rigidly mounted at the inlet and outlet to the duct system
(e.g. fans, heat exchangers and humidifiers) with an operating weight less than 75 pounds need
not be braced if the duct run it is attached to is braced. Equipment with an operating weight
greater than 75 lbs. must be braced and supported independent of the duct.
Brace spacing for low deformability duct shall not exceed one half of the brace spacing of high
deformability duct.
o
Bracing brackets shall be designed to yield in a ductile manner prior to achieving a load
level which would result in non-ductile concrete cone pullout failure. This ductility shall
be demonstrated by psuedostatic cyclic testing. An OSPHD approval of bracket design values
shall be considered as adequate demonstration of bracket ductility. Alternately, if cyclic testing
is not available, maximum brace spacings in the table presented on the brace spacing details
sheet shall be reduced by 50%.
Connections
If shot pin anchors are allowed, walls shall be designed for those forces and verified with wall
structural engineer.
If the area of influence for multiple anchors overlap, group affects shall be taken into account.
Anchor type shall satisfy the requirements for the parent material.
Anchor must be positively fastened without consideration of frictional resistance produced by
effects of gravity.
Design documents must contain sufficient information relating to the attachments to verify
compliance with ASCE 7-13.4.
Anchors and supports must be designed for the same forces and displacements, as per ASCE 713.6.5.
All post installed anchors utilized in the seismic design must be qualified for use in cracked
concrete and approved for use with seismic loads.
All beam clamps utilized for vertical supports must also incorporate retention straps.
All seismic brace arm anchorages to include concrete anchors, beam clamps, truss connections,
etc. must be approved for use with seismic loads.
Gravity supports must be designed by a licensed engineer in the project state for systems
subject to seismic requirements as listed above. Gravity supports include primary support and
anchorage of all distributed systems, riser supports, and supports for floor mounted utilities.
Design to include seismic loads in conjunction with dead loads as required by the IBC/ASCE 7.
APPENDEX B
SEISMIC BRACING OF HVAC
SYSTEMS OF LDS TEMPLES
KDK ENGINEERING
KEVIN COUCH, DAVID DE KOCK, KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERNIG AND TECHNOLOGY
BRIGHAM YOUNG UNIVERSITY
KEVIN COUCH
KDK
ENGINEERING
DAVID DE KOCK
KIRSTEN HINDS
The following steps and figures shall be used to determine the distance of brace spacing. Brace spacing shall not
exceed the lesser of the following:
1. Duct brace spacing schedule for duct
2. Pipe brace spacing schedule for pipe
3. Pipe Brace Spacing provided by the NSE
2. Capacity of the structure to resist brace load
3. Connection strength of the brace to the duct or pipe
4. Brace Capacity
5. Capacity of duct or pipe to span between braces
The Structural Engineer of Record(SER) and Mechanical Engineer of Record(MER) must provide the capacity of connected
parts of the structure to the Non-Structural Engineer (NSE).
Seismic supports are referred to as either lateral or transverse bracing, other supports are referred to as gravity supports.
1. The spacing of seismic bracing of ductwork or pipes shall be determined by seismic analysis based on the requirements of ASCE 7-10.
This design shall be performed by a licensed structural engineer in responsible charge for nonstructural seismic bracing design(NSE).
2. The NSE shall coordinate this design with the building design Structural Engineer of Record (SER) and the Mechanical Engineer of
Record (MER). Maximum brace spacing shall not exceed values which would exceed allowable limits on the building or facility structure,
as provided by the SER.
3. Each straight run of ductowrk or pipe should be installed with a minimum of two transverse braces perpendicular to the ductwork
and one longitudinal brace installed parallel to the ductwork, as shown in the Figure 1.
T
T
T
L
L
<= Max Longitudinal Brace Spacing
T
T - Transverse Brace
Location
L - Longitudinal Brace
Location
X- Gravity Support
Figure 1
4. Transverse seismic braces should be installed at the final gravity support point of each run of duct or pipe that has two or more gravity
supports. If the distance between the seismic braces exceeds the maximum calculated transverse brace spacing in the following relevant
table, then additional transverse seismic braces shall be located to limit the seismic brace spacing to the maximum calculated transverse
spacing.
5. A longitudinal brace must be located on each straight run of duct greater than 8' in length and each run of pipe with length
greater than the calculated longitudinal seismic brace spacing. Additional seismic braces shall be located on the run to
limit the seismic brace spacing to the maximum longitudinal brace spacing.
T
Support Point
Duct Width
Length=1/2 Calculated Transverse Brace Spacing - 2*Duct Width
6. A transverse brace located within two duct widths of a 90 degree turn can provide some longitudinal bracing for the
straight run of duct around the turn. The length of ductwork longitudinally braced by this transverse brace is equal to one
half the maximum transverse brace spacing minus the distance from the transverse brace to the turn, as shown in Figure 2.
For pipes this may apply if the transverse brace is within the offset length from the offset length table. The length
of pipe that may supported longitudinally is one half the maximum transverse brace spacing minus the distance from the
transverse brace to the turn.
2 times Duct Width or Maximum offset length(for pipes)
Figure 2
KDK
KDK ENGINEERING
LDS CHURCH
BRACE SPACING
DT-01
WINTER 2013
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
NOTES
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
7. If a straight run of ductwork or pipe has less than two gravity support points, is connected to a braced straight run
of ductwork or pipe at each end, and its total length is less than two duct widths for duct or the maximum offset
length in the table below for pipe, brace across the run by adding its length to the transverse and longitudinal
brace design of the connected runs. If its length is greater than two duct widths for duct or the maximum offset
length for pipe in the table below, a support point with a transverse brace is required, as shown in Figure 3 and 4.
<= 2x Duct Width
T
TL
L
<= Max. Transverse Braces Spacing - Offset
<= Max Longitudinal Brace Spacing
Figure 3: Offset With No Transverse Brace Required
>= 2x Duct Width
T
T L
L
<= Max. Transverse Braces Spacing - Offset
<= Max Longitudinal Brace Spacing
Figure 4: Offset With Transverse Brace Required
Gravity Support
00°
45.
<= Max Transverse Brace Spacing - Offset Length
8. Vertical drops to equipment require a transverse brace at the final gravity support location before the ductwork or pipe drops. The
total length of the ductwork from the support point to the equipment connection or flexible connector shall be less than half
the maximum spacing of the transverse brace, and the length of ductwork or pipe from the support point to the drop should be less
than two duct widths for pipe or the applicable maximum offset length from the pipe brace spacing schedule, as shown in the figure 5.
Transverse Brace
Offest Length<= 2x Duct Width or Maximum offset Length(for pipes)
Figure 5
9. Bracing brackets shall be designed to yield in a ductile manner prior to achieving a load level which would result in
nonductile concrete cone pullout failure. This ductility shall be demonstrated by psuedostatic cyclic testing. An OSPHD
approval of bracket design values shall be considered as adequate demonstation of bracket ductility. Alternately, if
cyclic testing is not available, maximum brace spacings in the Duct Brace Spacing Schedule and the Pipe Brace Spacing
Schedule shall be reduced by 50%.
10. Do not mix solid bracing with cable bracing in the same direction on any duct or pipe run.
11. Duct and Pipe seismic bracing design shall consider mechanical vibration and thermal loading using vibration and thermal
requirements provided in mechanical specifications.
12. Cable bracing shall be in a straight line to the structure, it shall not touch other ductowrk, piping, or other building
components.
KDK
KDK ENGINEERING
LDS CHURCH
BRACE SPACING
DT-02
WINTER 2013
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
NOTES
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
KDK
KDK ENGINEERING
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
0' - 1"
0' - 2"
0' - 3"
0' - 4"
0' - 6"
0' - 8"
0' - 10"
1' - 0"
1' - 2"
3' - 0"
2' - 0"
2' - 0"
4' - 0"
8' - 0"
10' - 0"
10' - 0"
10' - 0"
10' - 0"
1' - 0"
1' - 0"
1' - 0"
2' - 0"
4' - 0"
8' - 0"
10' - 0"
10' - 0"
10' - 0"
0' - 0"
0' - 0"
0' - 0"
1' - 0"
2' - 0"
4' - 0"
5' - 0"
6' - 0"
10' - 0"
2.0g,
Seismic
Input
0' - 0"
0' - 0"
0' - 0"
1' - 0"
2' - 0"
4' - 0"
5' - 0"
6' - 0"
10' - 0"
Maximum Seismic
Acceleration Sds
Input (g)
0.2
0.4
0.8
1.6
Duct Brace Spacing
Maximum
Transverse Brace
Spacing, Lt (ft.)*
40' - 0"
30' - 0"
30' - 0"
30' - 0"
Maximum
Longitudinal Brace
Spacing, Ll (ft.)
LDS CHURCH
80' - 0"
60' - 0"
60' - 0"
40' - 0"
NOTES
Max Pipe
Diameter (in)
Maximum Offset Lengths for Pipe
0.25g,
0.5g,
1.0g,
Seismic
Seismic
Seismic
Input
Input
Input
Pipe Brace Spacing
40' - 0"
40' - 0"
20' - 0"
Max Longitudinal
Distance (ft)
80' - 0"
40' - 0"
20' - 0"
SPACING TABLES
DT-03
WINTER 2013
0' - 5"
0' - 8"
1' - 4"
Max Transverse
Distance (ft)
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
Max Pipe
Diameter
(in)
General Notes
Importance Factors
Code
LDS
Requirement Requirement
Description
Sprinkler systems (including all mechanical and electrical components
required for the fire protection sprinkler system to operate following an
earthquake) and other life-safety components required by ASCE 7-10
13.1.3.
All Other Systems
Ip = 1.5
Ip = 1.5
Ip = 1.0
Ip = 1.25
Notes
Use Ip = 1.25 only to calculate loads. for all other code
requirements assume Ip = 1.0
Mechanical and Electrical components listed in this Schedule shall be braced and shall conform to ASCE 7-10 Chapter 13
Seismic Design Category
Notes
Clarification
Seismic Design Categories A and B
No seismic bracing is required
Seismic Design Category C
Fire protection sprinkler systems: This includes all mechanical and electrical components required for the fire protection
sprinkler system to operate following an earthquake, such as: piping, fire pumps, fire pump control panels, water tanks, fire
dampers, smoke dampers, smoke exhaust systems, generators, transfer switches, switches, emergency lighting systems,
and other life-safety systems or systems supporting life-safety systems.
Pipes and Components with Ip = 1.5
Special Bracing Excpetions for Piping (does not apply to fire protection sprinkler piping)
Piping with Rp = 4.5 (per Table 13.6-1 of
ASCE 7-10) or greater, and with Ip = 1.5 or
less, and with nominal diameter of 2 inches
(50 mm) or less, and spaced to avoid impact
with other ducts, piping, or architectural
components, need not be braced.
Seismic Design Category D, E, and F
Fire protection sprinkler systems as noted in Seismic Design Category C
All components without flexible connections between the component and associated ductwork, piping, and conduit.
All components with flexible connections between the component and associated
All components with flexible connections between the component and associated
ductwork, piping, and conduit that weigh more than 20 lbf (89 N), and have a
center of gravity greater than 4 feet (1.22 m) above the adjacent floor.
All distributed systems without flexible connections between the component and
associated ductwork, piping, and conduit.
Distributed systems with flexible connections between the component and
associated ductwork, piping, and conduit that weight more than 5 lbf (73 N/m).
The following bracing exceptions are allowed; however, flexible
connections must be provided between un-braced
Type
Exception
Speciacl Exceptions for Ductwork
Ductwork weighing less than 17 lbf/ft (248 N/m) (including the acoustical duct
liner) or having a cross sectional area less than 6 ft2 (0.557 m2), spaced to avoid
impact with other ducts, piping, or architectural components need not be
braced. If not spaced to avoid impact with other ducts, piping, or architectural
components, then an engineer must certify that impacts with such will not
cause damage to such components. Otherwise ducts must be braced.
Special Exceptions for Piping
Ductwork supported by hangers when the distance from the top of the duct
to the structure support point is 12 inches or less, AND a swivel is used on rod
hangers, need not be braced.
Ductwork supported by a trapeze assembly when the total weight of the
ductwork supported by the trapeze is less than 10 lbf/ft (146 N/m), the trapeze
need not be braced.
*Does not apply to fire protection sprinkler piping
Piping with Rp = 4.5 (per Table 13.6-1 of ASCE 7-10) or greater, and with Ip =
1.5, and with nominal diameter of 1 inch (25 mm) or less, and spaced to avoid
impact with other ducts, piping, or architectural components, need not be
braced.
Piping with Rp = 4.5 (per Table 13.6-1 of ASCE 7-10) or greater, with Ip < 1.5,
and with nominal diameter of 3 inches or less, and spaced to avoid impact with
other ducts, piping, or architectural components, need not be braced.
Piping supported by hangers when the distance from the top of the pipe to
the structure support point is 12 inches or less, AND a swivel is used on rod
hangers, need not be braced.
Piping supported by trapezes when the distance from trapeze to the structure
support point is 12 inches or less, AND a swivel is used on rod hangers, need
not be braced.
Piping supported by a trapeze assembly when the total weight of all piping is
less than 10 lbf/ft (146 N/m), and no pipe supported by the trapeze exceed 3
inches (75 mm) for Ip < 1.5 or 1 inch (25 mm) for Ip = 1.5, the trapeze need not
be braced.
KDK
KDK ENGINEERING
LDS CHURCH
GENERAL NOTES
DT-04
WINTER 2013
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
NOTES
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
KDK
INCLUDE
CONNECTION
DETAIL
SEE CONNECTION
DETAILS
INCLUDE CONNECTION DETAIL
SEE CONNECTION DETAILS
KDK ENGINEERING
VERTICAL
HANGER OR
STIFFENED
RODS.
SEE STIFFENED
ROD DETAIL.
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
VERTICAL
HANGER OR
STIFFENED
RODS.
SEE STIFFENED
ROD DETAIL.
X
MA
X
MA
45º
45º
TRAPEZE
LDS CHURCH
INCLUDE
CONNECTION
DETAIL
SEE CONNECTION
DETAILS
VERTICAL
HANGER OR
STIFFENED
RODS.
SEE STIFFENED
ROD DETAIL.
NOTES
VERTICAL
HANGER OR
STIFFENED
RODS.
SEE STIFFENED
ROD DETAIL.
INCLUDE
CONNECTION
DETAIL
SEE CONNECTION
DETAILS
VERTICAL
HANGER OR
STIFFENED
RODS.
SEE STIFFENED
ROD DETAIL.
45º
TRANSVERSE RECTANGULAR DUCT BRACING
WINTER 2013
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
X
MA
CONCRETE OR
MASONRY WALL
RECTANGULAR DUCTS
DT-05
KDK
KDK ENGINEERING
INCLUDE CONNECTION DETAIL
SEE CONNECTION DETAILS
INCLUDE CONNECTION DETAIL.
SEE CONNECTION DETAILS
45°
45º
MA
X
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
MA
X
VERTICAL HANGER
OR STIFFENED RODS.
SEE STIFFENED ROD DETAIL
VERTICAL HANGER
OR STIFFENED RODS.
SEE STIFFENED ROD DETAIL.
LDS CHURCH
INCLUDE CONNECTION DETAILS.
SEE CONNECTION DETAILS
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
VERTICAL HANGER OR
ROD STIFFNERS.
SEE DETAIL STIFFENED ROD DETAIL.
CONCRETE OR MASONRY WALL
ROUND DUCTS
TRANSVERSE ROUND DUCT BRACING
DT-06
WINTER 2013
NOTES
INCLUDE CONNECTION DETAIL.
SEE CONNECTION DETAILS
KDK
INCLUDE CONNECTION DETAIL.
SEE CONNECTION DETAILS
KDK ENGINEERING
45º
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
X
MA
RECTANGULAR DUCT
ROUND DUCT
INCLUDE CONNECTION DETAIL.
SEE CONNECTION DETAILS
LDS CHURCH
45º
ROUND DUCT
NOTES
X
MA
RECTANGULAR DUCT
X
MA
ROUND DUCT
WINTER 2013
45º
RECTANGULAR DUCT
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
INCLUDE CONNECTION DETAIL.
SEE CONNECTION DETAILS
LONGITUDINAL BRACING
LONGITUDINAL DUCT BRACING
DT-07
KDK
6" MAX
KDK ENGINEERING
STIFFENER CLIP SPACED PER MANUFACTURER (2 MIN)
STEEL ANGLE OR
STRUT CHANNEL
Equipment
CABLE OR RIGID BRACE
45º
ATTACHMENT CLAMP
X
MA
6" MAX
KEVIN COUCH, DAVID DE KOCK AND KIRSTEN HINDS
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
IRA A. FULTON COLLEGE OF ENGINEERING AND
TECNOLOGY
BRIGHAM YOUNG UNIVERSITY
Four-Cable
ROD STIFFENER
LDS CHURCH
Solid Brace
WINTER 2013
Equipment
SEISMIC BRACING
OF HVAC SYSTEMS
DESIGN FOR LDS
TEMPLES
Eight Cable
NOTES
Equipment
EQUIPMENT BRACING
DT-08