AMERICAN NATIONAL STANDARD
ANSI/ASSE Z359.6-2009
Specifications and Design Requirements
for Active Fall Protection Systems
Part of the Fall Protection Code
A S
S E
AMERICAN S OCIETY OF
S AFETY E NGINEERS
The information and materials contained in this publication have been developed from sources believed to be
reliable. However, the American Society of Safety Engineers (ASSE) as secretariat of the ANSI accredited
Z359 Committee or individual committee members accept no legal responsibility for the correctness or completeness of this material or its application to speci fi c factual situations. By publication of this standard, ASSE
or the Z359 Committee does not ensure that adherence to these recommendations will protect the safety or
health of any persons, or preserve property
ANSI®
ANSI/ASSE Z359.6 – 2009
American National Standard
Speci fi cations and Design Requirements
for Active Fall Protection Systems
Secretariat
American Society of Safety Engineers
1 800 East Oakton Street
Des Plaines, Illinois 6001 8-21 87
Approved June 3, 2009
Effective Date November 16, 2009
American National Standards Institute, Inc.
American
National
Standard
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standards developer. Consensus is established when, in the judgment of the ANSI Board
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affected interests. Substantial agreement means much more than a simple majority, but
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standards. The American National Standards Institute does not develop standards and
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interpretation should be addressed to the secretariat or sponsor whose name appears on
the title page of this standard.
Caution Notice: This American National Standard may be revised or withdrawn at any
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Published August 2009 by:
American Society of Safety Engineers
1 800 East Oakton Street
Des Plaines, Illinois 60018-2187
(847) 699-2929 • www.asse.org
Copyright ©2009 by American Society of Safety Engineers
All Rights Reserved.
No part of this publication may be reproduced
in any form, in an electronic retrieval system or
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Printed in the United States of America
Foreword
(This Foreword is not a part of American National Standard Z359.6-2009.)
This standard, national in scope, was developed by an Accredited Standards Committee functioning under
the procedures of the American National Standards Institute, with the American Society of Safety Engineers
(ASSE) as secretariat. This standard establishes guidelines and minimum requirements for the development
of the various components that would comprise a comprehensive managed fall protection program.
It is intended that every employer whose operations fall within the scope and purpose of the standard will
adopt the guidelines and requirements detailed in this standard.
The need for this standard activity grew out of the continuing development of a series of fall protectionrelated standards. The focus is to provide guidance to designers of active fall protection systems. It should
be noted, as in all Z359-series standards, that this standard applies to all occupational and non-occupational
activities except those in SIC Division C (construction). It also is not intended to apply to sports activities such
as mountaineering.
Neither the standards committee, nor the secretariat, states that this standard is perfect or in its ultimate
form. It is recognized that new developments are to be expected, and that revisions of the standard will be
necessary as the state-of-the-art progresses and further experience is gained. It is felt, however, that uniform guidelines for the design of active fall protection systems are very much needed and that the standard
in its present form provides for the minimum criteria necessary.
The Z359 Committee acknowledges the critical role of design in in fl uencing the use of proper fall protection
equipment. Design de fi ciencies often increase the risk for employees who may be exposed to fall hazards:
examples are (1) lack of rail systems to prevent falls from machines, equipment and structures; (2) failure to
provide engineered anchorages where use of personal fall arrest systems are anticipated; (3) no provision
for safe access to elevated work areas; (4) installation of machines or equipment at heights, rather than fl oor/
ground level to preclude access to elevated areas; (5) failure to plan for the use of travel restriction or work
positioning devices.
The Z359 Committee solicits public input that may suggest the need for revisions to this standard. Such input
should be sent to the Secretariat, ASC Z359, American Society of Safety Engineers, 1 800 E. Oakton Street,
Des Plaines, IL 6001 8-21 87.
This standard was developed and approved for submittal to ANSI by the American National Standards
Committee on Standards for Fall Protection, Z359. Committee approval of the standard does not necessarily imply that all committee members voted for its approval. At the time it approved this standard, the Z359
Committee had the following members:
Randall Wing fi eld, Chairman
Basil Tominna, P.E., Vice Chairman
Timothy R. Fisher, CSP, CHMM, ARM, CPEA, Secretary
Jennie Dalesandro, Administrative Technical Support
Organization Represented
Name of Representative
American Society of Safety Engineers
Daniel Paine
Carl Griffi th, CSHM, CPSM, CHCM, CUSA, CPEA
Bradley S. McGill
Roderick A. Paul
Chuck Orebaugh
Joey R. Junio
Jim Rullo
Chris Delavera
J. Thomas Wolner, P.E.
Brad Rohlf
Craig Berkenmeier
Joe Burke
James W. Lane, CSP, P.E.
Mark C. Conover
Paul Doepel
Dr. J. Nigel Ellis, P.E., CSP, CPE
John T. Whitty, P.E.
Hugh Armstrong
David Lee
Randall Wing fi eld
Dave Lough
Timothy Healey
Jerome Kucharski, CFPS
Jack Lamberson
Bruce Guiliani
Frank Anzaldi
Ron Larkin
Russell Goldmann, II
Janice C. Bradley, CSP
David H. Pate, CUSA
Thomas Kramer, P.E., CSP
Rupert Noton, CEng, MIStructE
Paul Illick
Lynn Camp
Bashlin Industries, Inc.
Boeing Company
Buckingham Mfg. Co., Inc.
Capital Safety Group
Chevron
Chrysler LLC
Elk River, Inc.
Ellis Fall Safety Solutions
Flexible Lifeline Systems
Gravitec Systems, Inc.
Hartford Steam Boiler Inspection & Insurance Co.
Heritage Group Safety
Hy-Safe Technology
ISEA – International Safety Equipment Association
Indianapolis Power and Light
LJB Inc.
Latchways PLC
Lawrence Livermore National Security
Liberty Mutual Group
Lighthouse Safety LLC
MSA
Monsanto
Murdock Webbing Co. Inc.
National Association of Tower Erectors
Pamela R. Huck, Inc.
Peakworks
PenSafe
Reliance Industries, LLC
SPRAT – Society of Professional Rope
Access Technicians
Safety Connection
Safety Equipment Institute
Safety Through Engineering, Inc.
Scaffold Industry Association
SPANCO, Inc.
Sperian Protection
Sturges Manufacturing Co., Inc.
Tractel Inc.
Travelers
Tritech Fall Protection
United Auto Workers
U.S. Air Force Safety Center
U.S. Bureau of Reclamation
John Rabovsky, MS, CSP, ARM
Peter Furst
John Corriveau
Joseph Feldstein
Robert Apel
Robert Kling, P.E., CSP
Chad M. McDanel
Bob Golz
Greg Pilgrim
Gordon Lyman
Don Doty
Pamela Huck, CSP
Tim Accursi
Gabe Fusco
Keith Smith
W. Joe Shaw
Gary Choate
Loui McCurley
Jim Frank
Clint Honeycutt, Sr.
Chad Bourgeois
Steve Sanders
Mike C. Wright, P.E., CPE, CSP
Jeremy T. Deason, P.E.
Scott Billish
Daniel Zarletti
Arnie Galpin, P.E.
George Nolan
Preston Anderson
Chuck Ziegler
Richard Griffi th
Tyler Griffi th
Doug Knapp
Cliff Theve
Scott H. Richert, CSP, ARM, ALCM
John Seto
Craig Siciliani
Tom Kinman
John Rupp, Jr.
Thomas Pazell
Arvie E. Scott
Steven C. Beason
Victor Feuerstein, CIH
U.S. Department of Labor – OSHA
U.S. Department of the Navy
Western Area Power Administration
Subgroup Z359.6 had the following members:
Thomas Kramer, P.E., CSP (Chair)
Frank Anzaldi
John Corriveau
Dr. J. Nigel Ellis, P.E., CSP, CPE
Peter Furst
Joey Junio
Robert Kling, P.E., CSP
Paul Illick
Ken Mahnick
Chad M. McDanel
Daniel Paine
David H. Pate, CUSA
John Rabovsky, MS, CSP, ARM
W. Joe Shaw
Greg Small, P.Eng., M.Eng.
Basil Tominna, P.E.
Mike C. Wright, P.E., CPE, CSP
Sherman Williamson
John Newquist
Basil Tominna, P.E.
Douglas L. Craddock
Jeff Wild
Ralph Armstrong
Contents
SECTION .................................................................................................................. PAGE
1 . Scope, Purpose, Applications, Exceptions and Interpretations ........................ 8
1 .1 Scope .......................................................................................................... 8
1 .2 Purpose and Application ........................................................................... 8
1 .3 Exceptions .................................................................................................. 9
1 .4 Interpretations ............................................................................................ 1 0
2. De fi nitions ................................................................................................................ 1 0
3. Drawings and Speci fi cations ................................................................................. 1 0
3.1 General ........................................................................................................ 1 0
3.2 Sealing by a Professional Engineer ......................................................... 1 0
3.3 Required Information ................................................................................. 11
4. Materials, Equipment, and Other Design Requirements ................................... 1 3
4.1 Composition of Materials .......................................................................... 1 3
4.2 Ductility of Materials .................................................................................. 1 3
4.3 Environmental Considerations ................................................................. 1 3
4.4 Equipment ................................................................................................... 1 3
4.5 Other Design Requirements for Travel Restraint Systems ................... 1 7
4.6 Other Design Requirements for Fall Arrest Systems ............................. 1 7
5. Safety Criteria ......................................................................................................... 1 8
5.1 Speci fi ed Loads .......................................................................................... 1 8
5.2 Strength ....................................................................................................... 1 9
5.3 Swing Falls .................................................................................................. 21
5.4 Forces on the Worker’s Body ................................................................... 21
5.5 Clearance .................................................................................................... 22
5.6 Stability of Free-Standing Systems .......................................................... 22
6. Fall Protection System Loads and Forces ........................................................... 24
6.1 General ....................................................................................................... 24
6.2 Travel Restraint Systems .......................................................................... 24
6.3 Fall Arrest Systems ................................................................................... 25
7. Clearances for Fall Arrest Systems ...................................................................... 28
7.1 Clearance Reference ................................................................................ 28
7.2 Required Clearance .................................................................................. 28
8. Design Assumptions and Analytical Methods ..................................................... 32
8.1 Elasticity of Ropes ..................................................................................... 32
8.2 Horizontal Lifelines Sags .......................................................................... 32
8.3 Analytical Methods .................................................................................... 32
9. References .............................................................................................................. 34
1 0. Figures ................................................................................................................... 35
Appendices
A Commentary ........................................................................................................... 42
B Bibliography ............................................................................................................ 51
ANSI/ASSE Z359.6-2009 American National Standard
STANDARD REQUIREMENTS
1 . SCOPE, PURPOSE, APPLICATIONS, EXCEPTIONS AND INTERPRETATIONS
Specifications and Design Requirements
for Active Fall Protection Systems
EXPLANATORY INFORMATION
(Not part of American National Standard Z359. 1)
1 .1 Scope.
1 .1 .1 This standard is intended for engineers with
expertise in designing fall protection systems. It
speci fi es requirements for the design and performance of complete active fall protection systems,
including travel restraint and vertical and horizontal
fall arrest systems.
E1.1.1
In most cases, the engineer should be a
professional engineer. However, there are some
exceptions where it is permissible per a local
building code for an engineer who is not registered
with a state or other governing body to perform
engineering. It is strongly recommended that if this
work is being performed by a consultant for a client,
that the work be performed under the supervision of
a professional engineer.
1 .2 Purpose and Application.
1 .2.1 This standard has been developed as a consensus document to provide uniform practice in the
design of active fall protection systems. The intention is to provide design criteria for routine use and
not to provide speci fi c criteria for infrequently encountered problems which occur.
1 .2.2 This standard involves the application of the
last option from the hierarchy of fall protection – active fall protection systems. Other options for employee protection should be considered prior to the
employer selecting the use of an active fall protection system.
E1.2.2 The ANSI/ASSE Z359. 2 standard contains
a hierarchy of fall protection (See Section 5. 1).
The first and preferred element of the hierarchy is
eliminating fall hazards.
OSHA Instruction STD 1-1. 13 states that “in
situations where the safeguarding [through the
use of physical barriers is] not applicable because
employees are exposed to falls from an elevated
surface other than a predictable and regular basis,
personal protective equipment as required by 29
CFR 1910. 132(a) or other effective fall protection
shall be provided. ”
Furthermore, predictable and regular was de fined
in this document as:
a. At least once every 2 weeks, or
b. For a total of 4 man-hours or more during any
sequential 4-week period (e. g. , 2 employees
once every 4 weeks for 2 hours = 4 man-hours
per 4-week period).
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
1 .3 Exceptions.
1 .3.1 This standard is not intended as a substitute
for testing and certi fi cation of individual components
of fall protection equipment in accordance with applicable ANSI/ASSE Z359 equipment standards.
1 .3.2 This standard does not cover the design of
passive fall protection systems such as guardrails
and nets, except where such passive systems are
also designed to serve as anchorage and/or anchorage connector subsystems for active fall protection systems covered by this standard.
1 .3.3 This standard does not cover the design of
positioning systems.
1 .3.4 This standard does not cover the determination of structural strength and behavior of components or anchorages of active fall protection systems. It does, however, establish the safety criteria
once the strengths and behaviors are known. Such
strengths and behaviors are determined by analytical testing or engineering methods and by AISC,
ACI, NDS or other design standards for the materials and structural systems being used. The IBC,
ASCE, state and local building codes shall be referenced by the designer of active fall protections
systems.
E1.3.4 AISC – American Institute of Steel
Construction.
ACI – American Concrete Institute
NDS – National Design Standard for Wood
Construction
IBC – International Building Code
ASCE – American Society of Civil Engineers
1 .3.5 This standard does not specify design or performance requirements for fall arrest equipment or
systems that have been manufactured and successfully tested in accordance with the requirements of another ANSI/ASSE Z359 standard.
E1.3.5. This standard is intended for the design of
complete active fall protection systems. Therefore, it
is recommended that this standard not be referenced
on specific fall protection products. It is anticipated
that this standard may be used to incorporate
equipment components into the design of active
fall protection systems prior to an acceptable
product standard being created for the equipment
component’s proper use.
Acceptance of material supplied from outside of
the United States. For equipment in which an ANSI
standard does not exist, engineers can consider
fall arrest equipment complying with EN, CSA, AU
and NZ standards as acceptable alternatives after a
review of the applicable foreign standard.
1 .3.6 This standard does not supersede the requirements of applicable occupational safety and
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
health regulations. Where the requirements in this
standard differ from legislated requirements, the
most conservative requirement shall be followed.
1 .3.7 In ANSI standards, “shall” is used to express a
requirement, i.e., a provision that the user is obliged
to satisfy in order to comply with the standard;
“should” is used to express a recommendation or
that which is advised but not required; and “may”
is used to express an option or that which is permissible within the limits of the standard. Notes accompanying sections do not include requirements
or alternative requirements; the purpose of the
e-column accompanying a section is to separate
from the text explanatory or informative material.
Notes to tables and fi gures are considered part of
the table or fi gure and may be written as requirements. Legends to equations and fi gures are considered requirements.
1 .4 Interpretations. Requests for interpretations of
this standard shall be in writing and addressed to
the Secretariat of this standard.
2. DEFINITIONS
Please refer to ANSI/ASSE Z359.0, Definitions and
Nomenclature Used for Fall Protection and Fall Arrest, for de fi nitions of terms used in this standard.
3. DRAWINGS AND SPECIFICATIONS
3.1 General.
3.1 .1 A fall protection system meeting the requirements of this standard shall have drawings and/or
speci fi cations prepared by or under the direction of
an engineer.
3.2 Sealing by a Professional Engineer.
3.2.1 If the system is designed by a professional
engineer, the professional engineer who designs
the system shall affi x his or her professional seal to
each drawing and speci fi cation issued. The professional engineer shall be registered in the state or
jurisdiction where the work is being performed.
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
3. 3 Req u i red I n form ati on .
Drawings, speci fi cations, and instructions
provided by the engineer shall include:
3. 3. 1
A statement de fi ning the type of system (fall
arrest, travel restraint, etc.) and indicating that the
design is in accordance with the requirements of
this standard;
3. 3. 1 . 1
A drawing showing the layout of the system,
including where it is located and the complete assembly of all components. In the case of a system
that can be relocated, the layout shall depict the
engineer’s expected typical installation and design
assumptions;
3. 3. 1 . 2
A speci fi cation of the number, location, and
quali fi cations (including minimum and maximum
weights and training) of workers using the system;
3. 3. 1 . 3
Speci fi cations for all components, including
sizes and minimum required breaking strengths.
The speci fi cations shall reference applicable standards and/or fully specify the makes and models of
the components. Where substitute materials are allowed or performance speci fi cations are provided,
the speci fi cations shall adequately describe the acceptable substitutions or products, respectively;
3. 3. 1 . 4
E3.3.1.4
This section applies to products and
materials that are not manufactured in accordance
with an ANSI/ASSE Z359 standard.
A description of any proof testing required
before the system may be put into use;
3. 3. 1 . 5
Alternatively, guidelines under which it
was intended for the system to be used can be
provided.
Information on the expected performance
of the system, including the maximum arrest load
(MAL), maximum loadings of all components, sags
and de fl ections, deployment of energy absorbers, and the maximum arrest force (MAF). Where
system performance may be affected by variable
environmental conditions such as temperature,
performance in worst-case conditions shall be described;
In horizontal lifelines (HLLs), the greatest
deflections occur at the highest temperature and the
greatest forces occur at the lowest temperature.
3. 3. 1 . 6
3. 3. 1 . 7
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E3.3.1.6
A speci fi cation of any environmental limitations on the use of the fall protection system, such
as chemical, temperature, radiation, or weather
factors that may temporarily or permanently render
the system unsafe to use;
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E3.3.1.7
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ANSI/ASSE Z359.6-2009 American National Standard
3.3.1 .8 A description of the greatest required clearances for all permitted worker locations, connecting
means, and full body harness combinations. Where
a required clearance varies with environmental conditions, the worst-case value shall be speci fi ed;
Specifications and Design Requirements
for Active Fall Protection Systems
E3.3.1.8
During a fall, harness effects or D-Ring
slide are commonly taken into account in clearance
calculations. The variable can vary by model.
3.3.1 .9 Instructions for assembly and installation. In
the case of generic systems or a system that can
be relocated, the instructions shall specify:
3.3.1 .9.1 The minimum required strength of the anchorages;
3.3.1 .9.2 The clearances required below the work-
ing platform or anchorages; and
3.3.1 .9.3 Any safety precautions that shall be followed during the erection and dismantling of the
system.
3.3.1 .1 0 Instructions for inspection, maintenance,
and retirement of the system and all of its components, including how often inspection and maintenance are to be performed and a description of
the quali fi cations required for persons performing
these tasks;
3.3.1 .1 1 Instructions for safe access to, egress
from, and use of the system;
3.3.1 .1 2 For fall arrest systems, a rescue plan or
directions to the owner of the system or the employer of the workers using the system to develop and
implement a rescue plan before the system is used.
The engineer shall indicate the appropriate uses of
the system or its anchorages during a rescue;
3.3.1 .1 3 A statement specifying:
3.3.1 .1 3.1 That the engineer who designed the
system or an engineer with similar experience and
quali fi cations shall be consulted before modifying
the design; and
3.3.1 .1 3.2 Whether the system is intended to be
generic or capable of being relocated, i.e., so that it
may be used at multiple locations.
3.3.1 .1 4 For permanent systems, “as-constructed”
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
drawings. The engineer shall state that the installation is in general accordance with the as-constructed drawings and speci fi cations; and
3.3.1 .1 5 Shall indicate how often the anchorages
shall be recerti fi ed by the engineer designing the
system or an engineer with similar experience and
quali fi cations.
E3.3.1.15.
If the original design was performed
by an engineer, an engineer or a qualified person
under the supervision of an engineer can perform
the recertification. If the original design was not
performed by an engineer, an engineer should be
involved in the recertification if this standard is to be
used for that process..
4. MATERIAL, EQUIPMENT, AND OTHER DESIGN REQUIREMENTS
4.1 Composition of Materials. Load-bearing com-
ponents of active fall protection systems shall be
composed of synthetic or metallic materials. Organic fi bers and materials may be used only for
non-load-bearing components.
4.2 Ductility of Materials. Metallic or synthetic
materials (with the exception of composite plastics
such as fi berglass) shall have at least 1 0% elongation prior to failure in the environments to which
they will be exposed.
4.3 Environmental Considerations. All compo-
nents of an active fall protection system shall be
speci fi ed to provide safe and durable service in
the environment(s) where the system may be used.
Environmental considerations include, but are not
limited to, corrosion, chemical attack, weather,
abrasion, and ultraviolet exposure. Additionally,
all portions of anchorages which are permanently
concealed from view shall be made from materials
that have the necessary durability for the environment.
E4.3 Designers should not assume that anchorages
that are permanently concealed will last forever.
At a minimum, the anchorages should be
inspected as outlined in Sections 4.6.4 and 4.6.5.
4.4 Equipment.
4.4.1 General. Fall arrest equipment components
used in systems designed in accordance with the
requirements of this standard shall meet the requirements of the applicable ANSI/ASSE Z359
standard. Where an ANSI/ASSE Z359 standard
does not exist for a particular component, suitable
speci fi cations for manufacturing or purchasing the
component shall be provided by the engineer.
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E4.4.1 Care should be taken when considering how
to use a piece of equipment. Warnings, such as a
manufacturer specifically prohibiting the use of their
product in a certain manner, should be heeded. An
example of this prohibition is the 1) use of an SRL
in a flat manner rather than on its side, or 2) use
of an eyebolt in a manner that would allow it to be
subjected to an out-of-plane load.
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
4.4.2 Compatibility. Equipment and hardware for
all components of an active fall protection system
shall be speci fi ed to provide compatible connections. Combinations of equipment from different
manufacturers shall be permitted if the engineer is
satis fi ed that the connections are compatible and
that there is no dangerous interaction between
them, e.g., loading of carabiner or snaphook gates
to allow roll-out.
4.4.3 Energy Absorbers.
4.4.3.1 General. Energy absorbers, including per-
sonal energy absorbers (PEAs), self-retracting
lanyards (SRLs), and horizontal lifeline energy
absorbers (HLLEAs), shall sacri fi cially dissipate
the energy from a fall. They shall not release the
energy that they have absorbed back to the system or worker. Springs, bungees, and other elastic
devices shall not be considered energy absorbers
under this standard. Elastic mechanisms within
energy absorbers may be used to buffer, without
permanent elongation, thermal shrinkage or travel
restraint forces.
4.4.3.2 Selection of Personal Energy Absorbers. When selecting personal energy absorbers:
4.4.3.2.1 When the free fall distance allowed by the
system is 6 feet (1 .83 m) or less and worker weight
is 31 0 lbs (1 41 kg) or less, energy absorbers and
energy-absorbing lanyards, where used, shall meet
the requirements of ANSI/ASSE Z359.1 ; or
4.4.3.2.2 The engineer shall:
4.4.3.2.2.1 Use dynamic analysis, energy analysis,
or testing and interpolation analysis to ensure that
the impact forces on the worker’s body do not exceed 1 ,800 pounds (8 kN); or
4.4.3.2.2.2 Ensure that the maximum free fall distance allowed by the system does not exceed
in the following formula:
h Max =
where
w
X Max
E4.4.3.2.2.2 Specialized energy absorbers and
energy-absorbing lanyards may be used to control
the impact forces when devices meeting the
requirements of ANSI/ASSE Z359.1 do not provide
adequate protection.
Specialized energy-absorbing lanyards meeting
the requirements of ANSI/ASSE Z359.1 are
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FAvg – w
hMax
ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
= maximum free fall distance permitted by the
system, ft.
manufactured for larger free falls and workers
whose weight exceeds 310 lbs (141 kg). When
used, these devices shall keep the impact forces
below 1, 800 lbs (8 kN) for the maximum worker
mass and free fall allowed by the system.
h Max
FAvg =
average deployment force of the PEA or SRL,
lbs, in accordance with Section 6.3.3.2 or 6.3.4.2,
as applicable
= weight of worker, lbs, in accordance with Section 6.3.2
w
XMax
XMax is often identified as the deceleration distance
on an equipment label.
= maximum rated extension of the PEA, ft.
4.4.4 Self-Retracting Lanyards.
4.4.4.1 Travel Restraint Systems. SRLs shall
not be used in travel restraint systems unless the
length of the lifeline on the drum of the SRL will not
permit the worker to reach the hazard even when
fully deployed.
4.4.4.2 Fall Arrest Systems.
E.4.4.4.2 See Appendix A.
4.4.4.2.1 Flexible Anchorage Systems.
E4.4.4.2.1
When an SRL is used in a flexible
anchorage system such as an HLL, the engineer
should consider the dynamic interaction between
the locking mechanism and the natural frequency
of the flexible anchorage system. This should be
considered so that the SRL does not unlock during
the rebound of the system after fall arrest or, in a
system used by multiple workers simultaneously,
as a result of subsequent falls. A simple drop test
may consist of an SRL attached to center of 60
foot undampened cable between two substantial
anchorage points. Alternatively, the same test on
the cable using HLL energy absorber as specified
by the HLL manufacturer.
4.4.4.2.2 Systems Where Free Fall is Limited to
the Self-Retracting Lanyard’s Activation Distance. When the fall arrest system anchors the
SRL suffi ciently above the worker’s dorsal D-Ring
so that the free fall allowed by the system equals the
SRL’s activation distance, all SRL types meeting the
requirements of ANSI/ASSE Z359.1 may be used.
4.4.4.2.3 Systems Where Free Fall Exceeds the
Self-Retracting Lanyard’s Activation Distance.
Where the conditions of Section 4.4.4.2.2 cannot be
met, only SRLs with integral PEAs may be used.
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4.4.5 Lanyards.
4.4.5.1 Lanyards in Travel Restraint Systems.
PEAs may be used in lanyards in travel restraint
systems, provided that the engineer has determined whether the restraint force could cause the
PEA to deploy and, if so, that such deployment will
not permit the worker to reach the fall hazard.
4.4.5.2 Lanyards in Fall Arrest Systems. Except
as allowed by Section 4.4.3.2 or 5.4.2, lanyards in
fall arrest systems shall meet the requirements of
ANSI/ASSE Z359.1 .
4.4.6 Full Body Harnesses. Full body harnesses
shall meet the requirements of ANSI/ASSE Z359.1 .
Stretch out used in clearance calculations in Section 7.2.4 of this standard shall account for stretching of the type(s) of full body harnesses permitted
for use with the fall arrest system.
4.4.7 Fall Arresters. Fall arresters used on vertical
lifelines (VLLs) and ladder-climbing systems shall
meet the requirements of ANSI/ASSE Z359.1 .
4.4.8 Horizontal Lifeline Energy Absorbers.
4.4.8.1 Travel Restraint Systems. HLLEAs may
be used in travel restraint systems, provided that
the engineer has determined that the restraint forces will not cause the HLLEAs to deploy and ensures that the de fl ection of the cable in combination
with other deformations of the restraint system, will
not permit the worker(s) to reach the fall hazard.
The restraint system shall meet the requirements of
Section 4.4.8.2.
4.4.8.2 Fall Arrest Systems. HLLEAs shall be
used only to control or reduce the MAL, and only if
the engineer has ensured that the increased clearance requirements can be met.
E4.4.8.2 See Appendix A.
The maximum span in any HLL where HLLEAs are
used should not be greater than L Max in the following
equation:
2
10.76 Avg
-4
Max = 4.6 16
L
T
Mw
where
LMax = maximum span, ft.
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Specifications and Design Requirements
for Active Fall Protection Systems
TAvg = average deployment force of the HLLEA, lbs,
in accordance with Section 6.3.6.3
M = “lumping factor” for the maximum number of
workers that may attach themselves to one span
of the HLL at any one time, as specified in Section
E6.3.7.2
w = weight of one worker, lbs, in accordance with
Section 6.3.2
4.5 Other Design Requirements for Travel Restraint Systems. In addition to ensuring compli-
ance with the applicable safety criteria in Section
5, the engineer shall ensure that the worker cannot
reach and fall into any open hole or off the edge
of the working platform. Special attention shall be
paid to the use of fl exible anchorage systems, such
as HLLs, that may in fl uence how short the lanyard
or lifeline needs to be to meet this requirement.
4.6 Other Design Requirements for Fall Arrest
Systems.
4.6.1 General. In addition to the applicable safety
criteria outlined in Section 5, the requirements in
Sections 4.6.2 and 4.6.3 shall apply.
4.6.2 Rescue. To satisfy the requirements of Sec-
tion 3.3.1 .1 2, the design shall take into consideration
the potential uses of and loads on the fall arrest
system, in order to facilitate the prompt rescue of
workers who may fall while attached to the system.
4.6.3 Anchorage for Suspended Equipment Operations. The fall arrest anchorage requirements
for individuals working from suspended equipment
shall be as speci fi ed in ANSI/IWCA I-1 4.1 and
ASME A1 20.1
4.6.4 Inspection of Components Not Addressed
by a Manufacturer’s Requirements. For compo-
nents not addressed by a manufacturer’s inspection requirements, the components shall be visually
inspected, as a minimum, in a manner and frequency speci fi ed by the engineer designing the active
fall protection system. The frequency of inspection
shall not exceed one year.
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4.6.5 Recerti fi cation of Active Fall Protection
Systems. Active fall protection systems shall be
E4.6.5. If the original design was performed by an
engineer, an engineer or a qualified person under
the supervision of an engineer can perform the recertification. If the original design was not performed
by an engineer, an engineer should be involved in
the recertification if this standard is to be used for
that process.
thoroughly reviewed by an engineer at a frequency
to be determined by the original design or other
similarly quali fi ed engineer but not to exceed fi ve
years. This recerti fi cation process shall include a
review of the original documents prepared for the
system and their continued applicability. As a minimum, the following criteria shall also be considered
and the result of the certi fi cation shall result in a report or set of documents outlined in Section 3.3.1 .
• Changes in the hazards and tasks that are addressed by the active fall protection system.
• Changes in regulations, standards or other factors
affecting the active fall protection system.
• Feedback from a representative sample of the
competent persons and authorized persons of
the fall protection system.
5. SAFETY CRITERIA
5.1 Speci fi ed Loads. The load effects on each
component of an active fall protection system shall
be determined for the following loads:
E5.1 The symbols identified in Section 5.1 appear
in Section 5.2.3.
5.1 .1 D — Dead loads from the static weight of materials used in the system and, as applicable, from
the structure to which it is attached.
5.1 .2 A — Fall arrest or travel restraint loads applied
to the system determined in accordance with Section 6. The applied loadings from energy absorbers
shall be determined in accordance with Sections
6.3.3.1 , 6.3.4.1 , 6.3.5, and 6.3.6.2, as applicable.
E5.1.2
This can also be taken as the impact of
the dynamic loading applied to the building or
structure resulting from the activation of the active
fall protection system attached; as specified by the
engineer designing the system.
5.1 .3 L — Live loads due to the intended use and
occupancy of the building or structure to which the
active fall protection system is attached. Live loads
shall be as speci fi ed in the International Building
Code.
5.1 .4 Q — Wind, earthquake, or other loads that
may be applied to the structure or building to which
the active fall protection system is attached. These
loads shall be as speci fi ed in the International
Building Code.
5.1 .5
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T — In fl uences resulting from temperature
ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
changes, shrinkage or creep of component materials, or differential settlement. Temperature changes shall be as speci fi ed in the International Building
Code. Shrinkage or creep shall be in accordance
with the applicable design code for the materials
used in the construction of the active fall protection
system or the structure to which it is attached.
5.2 Strength.
5.2.1 General. All components and subsystems of
an active fall protection system, and the structure
to which it is attached, shall have suffi cient strength
and stability such that:
R ≥ F*
where
R = the factored resistance of the component or
subsystem
F* = the worst-case factored effect of the applied
loads on the component or subsystem
5.2.2 Determination of Factored Resistance.
5.2.1 .1 General. Factored resistance shall be determined as follows:
R = ØU
where
Ø = the capacity-reduction factor
U = the ultimate strength of the component or subsystem
5.2.2.2 Factored Resistance for Common Construction Materials. R, Ø, and U for common
construction materials used in the construction of
the active fall protection system or the structure to
which it is attached shall be determined in accordance with the requirements of the applicable design code(s) in Section 9.
5.2.2.3 Factored Resistance for Materials Not
Covered by an ANSI Limit States Design Code.
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ANSI/ASSE Z359.6-2009 American National Standard
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for Active Fall Protection Systems
Where an ANSI limit states design code does not
exist for a material used in the construction of a fall
arrest system:
5.2.2.3.1 The ultimate strength, U, of a component
shall be based on testing of the component or calculation of the strength of the component using the
known strength of the material; and
5.2.2.3.2 The capacity-reduction factor, Ø, shall be
as follows:
5.2.2.3.2.1 For brittle materials such as fi berglass,
0.3;
5.2.2.3.2.2 For synthetic ropes and webbing, 0.5;
5.2.2.3.2.3 For materials that exhibit at least 1 0%
elongation prior to failure at a yield stress that is between 60 and 80% of the ultimate stress, 0.6; and
5.2.2.3.2.4 For wire ropes meeting the requirements
of ASTM A1 023 (applied to the terminated strength
of the wire rope), 0.75 (applied to the terminated
strength of the wire rope).
5.2.3 Determination of Factored Load Effects.
The factored load for each component of an active
fall protection system shall be the worst-case force
effect, F*, using the following formula for all possible combinations of applied loading:
(F*
= α DD * + ? ( α A A * + α L L* + α QQ* + αTT*)
where
D*, A *, L*, Q *, and T* = the forces carried by
each component due to the applied loads
D, A , L , Q, and T described in Section 5.1
α = the load factor for the speci fi c type of loading,
as follows:
αD = 1 .25 or, when the dead load opposes the effect
of A, 0.85
E5.2.3 See Appendix A.
1 ) Unlike the limit states design methods described
in the International Building Code, the load factors
in this section are applied to the forces carried by
each component, rather than to the load resisted
by the system. This is necessary to ensure a
consistent safety factor throughout the system. For
example, in an HLL system, the tension in the HLL
increases in much lower proportion to the increase
in applied loading, and where HLL energy absorbers
are employed, there may be no increase in lifeline
tension due to factoring the applied load.
2) In systems where the majority of the load effect
is due to the fall arrest or travel-restraint force, A,
engineers may choose to simplify their determination
of F* by using α D = α A = α L = α Q = αT = 1. 5, which is
often only slightly conservative.
αA = 1 .5
αL = 1 .5 or, when the live load opposes the effect
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Specifications and Design Requirements
for Active Fall Protection Systems
of A, 0
αQ = 1 .5
αT = 1 .25 or, when thermal stresses change the
HLL pre-tension, 1 .5
? = the load combination factor, as follows:
?
? = 1 , where only A is applied
? = 0.7, if A acts in combination with either L or Q
? = 0.6, if A acts in combination with both L and Q
?
?
?
5.3 Swing Falls. In fall arrest systems, anchor-
ages shall be located directly above the worker(s)
to eliminate swing falls, wherever it is reasonably
practical to do so. Where it is not reasonably practical to prevent swing falls, the swing-drop distance
shall not exceed 4.0 ft (1 .22 m) (see Figure 1).
E5.3 See Appendix A.
5.4 Forces on the Worker’s Body.
5.4.1 Travel Restraint Systems. Where a worker
is using a full body harness in a travel restraint system, the force on the worker’s body shall not exceed 400 lbs (1 .78 kN).
E5.4.1. Users ofthis standard are encouraged, where
possible, to design anchorages for fall restraint as
if they were fall arrest anchorages. Additionally, it is
recommended that energy absorbing lanyards are
considered in the equipment specification. These
precautions would provide some level of protection
in the case of a system misuse.
5.4.2 Fall Arrest Systems.
5.4.2.1 Maximum Arrest Force. The MAF experienced by each worker using a fall arrest system
shall not exceed 1 ,800 lbs, (8.0 kN) except that
when PEAs or SRLs are omitted in accordance
with Section 5.4.2.3, the MAF shall not exceed
1 ,800 lbs (8.0 kN).
E5.4.2.1. See Appendix A.
5.4.2.2 Forces Applied to the Full Body Harness. In a fall arrest system, a worker shall wear
a full body harness and be attached to the system
at the dorsal D-Ring. The only permitted exception
shall be for ladder-climbing systems, which may
be used with a sternal attachment when the free
fall distance is limited to 1 8 inches (0.46 m) or less,
or for harnesses equipped with a front-mounted
attachment element for fall arrest, which shall be
used only as part of a personal fall arrest system
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
that limits the maximum free fall distance to two
feet (0.61 m) and limits the maximum arrest force to
900 pounds (4.0 kN).
5.4.2.3 Use of Personal Energy Absorbers or
Self-Retracting Lanyards. Fall arrest systems
shall use PEAs meeting the requirements of Section 4.4.3.2 or SRLs meeting the requirements of
Section 4.4.4.2.3 except:
E5.4.2.3 PEAs are often incorporated into lanyards
but may also be located elsewhere in the fall arrest
system, e.g., as part of an anchorage connector or
permanently attached to the full body harnesses.
5.4.2.3.1 In accordance with Section 4.4.4.2.2;
5.4.2.3.2 For ladder-climbing systems where the
free fall is limited to 1 8 inches (0.46 m) or less; or
5.4.2.3.3 When elimination of energy absorbers is
required to stop a fall within very limited available
clearances.
5.5 Clearance.
5.5.1 Travel Restraint Systems. In travel restraint systems, consideration of clearance is not
required.
5.5.2 Fall Arrest Systems. In fall arrest systems,
the required clearance, calculated in accordance
with Section 7.2, shall be less than or equal to the
available clearance for the system.
For the purposes of clearance calculations, the applied loadings from energy absorbers shall, as indicated in Sections 6.3.3.2, 6.3.4.2, and 6.3.6.3, be
applicable.
5.6 Stability of Free-Standing Systems.
5.6.1 General. Free-standing systems may only be
used on surfaces with a downward slope of less
than 5º toward any side or opening where a worker
could fall.
E5.6.1 A 5º slope is equivalent to approximately a
5.6.2 Manufactured Products. In lieu of a rigor-
E5.6.2 At a minimum, the engineer should request
ous analysis of overturning and sliding provided below, an engineer can review manufacturer data and
literature prior to the speci fi cation of a product.
1” vertical to 12” horizontal slope.
the following information from the manufacturer
of a product that will be used as a free-standing
system:
• The surfaces on which the product has been
tested.
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Specifications and Design Requirements
for Active Fall Protection Systems
• Potential performance variations for possible
surface contaminants.
• The uniform or concentrated loads the product will
apply to the structure during erection, use and
dismantling.
• The required edge distance or edge conditions,
such as a parapet, required by the product.
• Other cautions or instructions that are needed for
proper performance of the system.
5.6.3 Overturning of Counterbalanced Systems.
Where an active fall protection system is freestanding or counterbalanced and is not anchored
to a solid support, the system shall have a factor of
safety against overturning to resist the worst-case
combination of fall arrest loading and con fi guration
of the system as follows:
5.6.3.1 Not less than 4.0;
5.6.3.2 Not less than 2.0 where the design prevents
change to the counterbalance mass or movement
of the fulcrum point i.e. where the counterbalance
weights are bolted together and the fulcrum point is
bolted to the free-standing system;
5.6.3.3 Not less than 1 .5 where:
5.6.3.3.1 The design prevents change to the counterbalance mass or movement of the fulcrum point
i.e. where the counterbalance weights are bolted
together and the fulcrum point is bolted to the freestanding system; and
5.6.3.3.2 There is a minimum 4.0 factor of safety
when the energy required to bring the system to incipient tipping is compared to the total energy generated by the worst-case fall(s) that could occur.
5.6.4 Sliding of Ballasted Systems. Where an active fall protection system relies on friction between
a ballasted anchor and its supporting surface, instead of being anchored to a solid support, the ballasted anchor shall have a factor of safety against
sliding of not less than 3.0 to resist the worst-case
combination of fall arrest loading and con fi guration
of the system. The following requirements shall
also apply:
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
5.6.4.1 The coeffi cient of kinetic friction used in
calculating the resistance to sliding shall be determined by fi eld testing in the direction(s) of potential
loading at the site or similar conditions where the
ballasted anchor will be used and shall simulate the
worst-case weather conditions that may affect the
coeffi cient of friction; and
5.6.4.2 Unless any applicable stops or parapet walls
are analyzed or tested to prove that they are strong
enough to prevent the ballasted anchor from sliding
to an edge and falling, the ballasted anchor shall
be installed a minimum of 1 0.0 ft from any edge of
the surface it might fall from if it were to slide while
resisting the fall arrest loading.
6. FALL PROTECTION SYSTEM LOADS AND
FORCES
6.1 General. The force, A , applied to an active fall
protection system to stop or prevent falls shall be
determined in accordance with Sections 6.2 and
6.3.
6.2 Travel Restraint Systems.
6.2.1 Maximum Arrest Force and Maximum Arrest Load. The loads and forces in all components
of a travel restraint system due to the worst-case
impact from worker(s) being stopped short of the
fall hazard shall be determined in accordance with
Sections 6.2.2 and 6.2.3.
6.2.2 Level Surfaces. For surfaces that slope less
than 5%:
E6.2.2 Designers should be aware that fall arrest
can result if workers have an improperly adjusted
lifeline, lanyard, or SRL that is long enough to allow
a fall to occur.
6.2.2.1 Temporary restraint anchorages shall be
designed using static analysis with A = 400 lbs (1 .78
kN) per worker attached to the anchorage; and
6.2.2.2 Permanent restraint anchorages shall be
designed for fall arrest, determined in accordance
with Section 6.3.
6.2.3 Sloping Surfaces. Temporary or permanent
restraint anchorages intended to prevent workers
from falling off the bottom edge of a downward slop-
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Specifications and Design Requirements
for Active Fall Protection Systems
ing surface shall be designed for the force required
to stop the worst-case slides down the slope. Forces may be determined using one of the methods
outlined in Sections 8.3.2 to 8.3.6, but shall be not
less than what is required by Section 6.2.2.
6.3 Fall Arrest Systems.
6.3.1 Maximum Arrest Force and Maximum
Load. The loads and forces in all components of
a fall arrest system shall be determined, for the
worst-case fall, by one of the methods outlined in
Sections 8.3.2 to 8.3.6.
6.3.2 Design Weight of Workers. For an analysis
in accordance with Sections 5.2 and 6.3, the design
weight, w, shall be the mass of the heaviest worker permitted on the system, including all tools and
equipment, but not less than 31 0 pounds (1 41 kg).
E6.3.2 See Appendix A.
6.3.3 Deployment Force of Personal Energy Absorbers and Energy-Absorbing Lanyards.
6.3.3.1 FMax (for strength calculations). PEAs and
energy-absorbing lanyards meeting the requirements of ANSI/ASSE Z359.1 shall be assumed to
deploy at a force of FMax = 900 pounds (4.0 kN), or,
in environments where they may become wet and
frozen, at a force of FMax = 1 ,800 lbs (8.0 kN). Where
a specialized PEA is required by the design, as permitted by Section 4.4.3.2, the device shall be assumed to deploy at the maximum force speci fi ed by
its manufacturer, but not less than 900 lbs (4.0 kN).
6.3.3.2 FAvg (for clearance calculations). PEAs
and energy-absorbing lanyards shall be assumed
to deploy at the minimum average force speci fi ed
by their manufacturers. In the absence of information from the manufacturer, PEAs meeting the requirements of ANSI/ASSE Z359.1 may be assumed
to deploy at FAvg = 0.8 x FMax.
6.3.4 Impact Force of Self-Retracting Lanyards.
6.3.4.1 General. SRLs may be used only in accor-
dance with Section 4.4.4.2.2. The maximum impact
force shall be determined using one of the methods
in Sections 6.3.4.2 to 6.3.4.4.
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
6.3.4.2 Dynamic Analysis and Energy Analysis.
When a fall arrest system is analyzed in accordance with Section 8.3.2 or 8.3.3, the MAF shall
be calculated using the assumption that the device
does not stretch and does not dissipate any energy
after it has locked off.
6.3.4.3 Static Analysis. When a fall arrest system
is analyzed in accordance with Section 8.3.4, the
MAF shall be the maximum impact force speci fi ed
by the manufacturer for the free fall permitted by
the system.
6.3.4.4 Testing and Interpolation Analysis. The
MAF shall be the measured force(s) when a fall arrest system is tested in accordance with Section
8.3.5.
6.3.5 Deployment Force of Horizontal Lifeline
Energy Absorbers.
6.3.5.1 General. When HLLEAs are used, the de-
ployment forces to be used in strength and clearance calculations shall be as speci fi ed in Sections
6.3.5.2 and 6.3.5.3.
6.3.5.2 TMax (for strength calculations). HLLEAs
shall be assumed to deploy at the maximum force
speci fi ed by their manufacturer.
6.3.5.3 TAvg (for clearance calculations). HLLEAs
shall be assumed to deploy at the minimum average
force speci fi ed by their manufacturer, or, when the
total energy consumed by an HLLEA at full deployment is speci fi ed by the manufacturer, as follows:
U
TAvg = X Max
HEAMax
where
TAvg = average deployment force, lbs
UMax = total energy absorbed by the HLLEA at full
deployment, lbs•ft.
XHEAMax = maximum available deployment of the
HLLEA, ft.
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Specifications and Design Requirements
for Active Fall Protection Systems
6.3.6 Multiple-Worker Falls.
6.3.6.1 General. For systems that may allow more
than one worker to be attached to an anchorage,
anchorage connector, or anchorage subsystem,
the effect of possible simultaneous or sequential
impacts shall be accounted for in determining the
MAF, MAL, and clearances.
In HLLs, unless the design of the system or control of the work procedures reliably precludes the
gathering of workers at a single point, all workers
allowed within a single span shall be assumed to
fall at the same point on the system.
In multiple-span HLLs, the simultaneous falling of
workers on different spans is considered highly
improbable. It shall not be necessary to consider
the possibility of simultaneous falls unless there is
some unusual circumstance, such as a multiplespan HLL above a single-span work surface that,
in the event of a collapse, would result in impacts
on more than one span within a very short time.
6.3.6.2 Equivalent Lumped Mass. In the absence
of more rigorous analytical methods, the effect of
multiple-worker falls may be modeled by:
E6.3.6.2 See Appendix A.
Another factor to consider for the lumping factor is
whether the fall is due to the surface upon which
the work occurs. A collapsible surface involves a
situation where the integrity of the surface upon
which the employees are working leads to a
potential fall hazard. Examples: employees working
on a suspended platform for exterior building
maintenance; maintenance on a roof with significant
deterioration in which there is a hazard with the
employees falling through the roof surface.
6.3.6.2.1 Lumping the masses of the falling workers
into a single mass that is the product of the mass of
the design worker, m, de fi ned in Section 6.3.2, and
the number of falling workers.
6.3.6.2.2 Lumping PEAs or SRLs, where used, in
parallel into a single device using F Max or FAvg as
applicable and de fi ned in Section 6.3.3 or 6.3.4.
For two workers attached, it shall be assumed that
they impact at the same time. For each subsequent
worker attached, the weight of the design worker
shall be added to the two workers impact.
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E6.3.6.2.2 For example where the MAF for the PEA
is 900 lbs. (4 kN) and the maximum worker weight
is 220 lbs. (100 kg) and four workers are attached, it
should be assumed that two workers are suspended
and two workers fall and impact the system. The
resulting force would be 900+900+220+220 =
2, 240 lbs. (10 kN). If used as a factor, the effective
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Specifications and Design Requirements
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lumping factor would be 2,240/900 = 2.49.
E6.3.6.3. In some cases,
6.3.6.3 Sequential Falls on Horizontal Lifeline
Systems. On HLLs only, the load effect, A , for mul-
energy absorbers, either
connected to the lanyard or horizontal lifeline, may
bottom out due to the additional energy applied by
the increased free fall.
6.3.7 Horizontal Systems. The engineer shall de-
E6.3.7 Engineers should take into consideration for
tiple-worker falls may be determined by loading the
HLL, pre-sagged by the deployment of any applicable HLLEA due to the earlier falls, with the dead
weight of all prior fallen workers, in accordance with
Section 6.3.2, plus the fall arrest impact from the
last worker. The free fall of and clearance required
for the last worker will be greater than for the prior
workers because the HLL has been pulled downward by the prior falls and permanent HLL sag due
to deployment of an HLLEA.
termine worker locations where falls would result
in the least difference between required and available clearances and cause the maximum forces in
the system components. Engineers shall, at a minimum, determine the performance of the system
when a fall occurs on the shortest span and the
longest span in the system. Engineers shall also
determine the variation in system performance due
to temperature or other environmental variations, if
applicable.
HLLs:
a) The maximum transverse forces on system anchorages occur when workers fall while immediately adjacent to end or intermediate anchorages; and
b) The greatest HLL tension and total-fall distance for each span of the system will occur
when a fall occurs midway between supports.
7. CLEARANCES FOR FALL ARREST SYSTEMS
7.1 Clearance Reference. Clearances shall be ref-
erenced to the working platform (CP), except when
it may be necessary for portable or temporary systems to reference clearances to the anchorage (CA)
(see Figure 2).
7.2 Required Clearance.
7.2.1 General. Clearance requirements shall ac-
count for the worst-case total of free fall distance,
deceleration distance, stretch out, applicable swingdrop distance, and the safety margin speci fi ed in
Sections 7.2.2 to 7.2.6 (see Figures 1 , 2, and 3).
In multiple-worker systems that are analyzed in accordance with Section 6.3.6.2, the required clearance shall be adjusted in accordance with Section
7.2.6.
7.2.2 Free Fall Distance.
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7.2.2.1 General. Free fall is the unimpeded fall dis-
tance of the worker. Free fall ends when all slack
has been taken out of the fall arrest system so that
further displacement of the worker will be resisted
by forces developed in the system. Free fall will include any applicable lanyard or HLL or VLL slack,
or activation distance (see Figures 2, 4, and 5).
7.2.2.2 Lanyard or Lifeline Slack. The lanyard
or lifeline slack shall be taken as the height of the
worker’s D-Ring above the opposite end of the
lanyard or lifeline, plus the length of the lanyard or
lifeline. Where the worker’s D-Ring is below the opposite end of the lifeline or lanyard, the difference in
height shall be negative (see Figures 4 and 5).
7.2.2.3 Activation Distance. The activation or
lock-off distance of a fall arrester or SRL shall be
included in the free fall distance (see Figure 5).
7.2.2.4 Horizontal Lifeline Slack. In HLL systems,
the change in sag between the initial sag and the
cusp sag shall be included in the free fall distance
(see Figure 6).
7.2.3 Deceleration Distance.
7.2.3.1 General. Deceleration distance is the distance over which a fall arrest system reacts to bring
a falling worker to a complete stop. Deceleration
distance shall include any applicable stretch of lifelines and lanyards, the maximum anchorage system de fl ection, and deployment of PEAs and SRLs
(see Figure 2).
7.2.3.2 Stretch of Lanyards. Signi fi cant dynamic
stretch of SRLs and conventional lanyards shall be
included in the deceleration distance. Where the
stretch is known to be less than 2 inches, it may be
ignored (see Figure 2).
7.2.3.3 Maximum Anchorage System De fl ection
(MASD). The dynamic displacement of the anchor-
age, dynamic stretch of a vertical lifeline, or dynamic sag of an HLL shall be included in the deceleration distance (see Figures 2 and 6).
7.2.3.4 Deployment of Personal Energy Absorbers and Self-Retracting Lanyards. In fall arrest
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Specifications and Design Requirements
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systems that use PEAs or SRLs, the deceleration
distance shall include the deployment distance of
these devices (see Figure 2), as follows:
7.2.3.4.1 PEAs may be assumed to fully deploy;
7.2.3.4.2 Deployment of PEAs or SRLs may be accurately determined using dynamic analysis, energy analysis, or testing and interpolation analysis
in accordance with Section 8.3.2, 8.3.3, or 8.3.5,
respectively; or
7.2.3.4.3 if static analysis is used (as allowed by
Section 8.3.4), deployment of PEAs or SRLs may
be estimated using the following formula:
X PEA =
wh
FAvg - w
Where
XPEA = deployment of the PEA or SRL, ft.
w = weight of falling worker, lbs, in accordance with
Section 6.3.2
h = the free fall, ft.
FAvg = average deployment force of the PEA or SRL,
lbs, in accordance with Section 6.3.3.2 or 6.3.4.2,
as applicable. The engineer shall review the manufacturer’s literature to determine the maximum deployment of the PEA that he or she has speci fi ed
for the fall arrest system or shall otherwise assume
3.5 ft (1 .07 m) worst-case deployment.
7.2.4 Stretch Out. The required clearance shall include allowance for stretch out, including harness
stretch, and reaction of the worker’s body to the
deceleration forces, including applicable lengthening of the worker’s body if falling from a kneeling or
lying position (see Figure 3). The type of full body
harness being worn by the workers is a major component of stretch out. Harness stretch data shall be
obtained from the harness manufacturer or shall
be determined by testing harness performance at
the MAF allowed by the fall arrest system. If the
engineer is unable to obtain harness stretch infor-
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E7.2.4 See Appendix A.
ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
mation or does not otherwise specify and control
the type(s) of full body harnesses being used, a
minimum of 2.5 ft (0.76 m) shall be assumed for the
harness contribution to stretch out.
7.2.5 Swing-Fall Distance. The required clearance shall include an allowance for any applicable
swing-fall distance (see Figure 1).
7.2.6 Safety Margin.
7.2.6.1 Rigid Anchorage Systems. The safety
margin, E, for rigid anchorage systems (see Figure
2) shall be not less than 2.0 ft (0.61 m).
7.2.6.2 Flexible Anchorage Systems. The safety
margin, E, for fl exible anchorage systems (see Figure 2) shall be not less than the value given by the
following formula:
E7.2.6.2 See Appendix A.
E = 0.6 + CMASD x MASD (ft)
where
CMASD depends on the method used to determine the
maximum anchorage system de fl ection (MASD),
as follows:
CMASD = 0.30 for static analysis in accordance with
Section 8.3.4
CMASD = 0.1 0 for dynamic analysis or energy analy-
sis in accordance with Section 8.3.2 or 8.3.3
CMASD = 0.05 for testing and interpolation analysis in
accordance with Section 8.3.5
7.2.7 Clearance for Equivalent Lumped-Mass
Simulation of Multiple-Worker Falls. Where a
fl exible
anchorage system providing protection for
multiple workers has been analyzed using an equivalent lumped mass as de fi ned in Section 6.3.7.2,
the required clearance calculated for the equivalent
lumped mass shall be increased to account for the
increased total of free fall and deceleration distance seen by the last worker to fall. In the absence
of other proven methods, the following formula may
be used to calculate the required clearance:
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E7.2.7 See Appendix A.
C, CLM, and C1 are the
applicable CP or CA values, depending on whether
the clearance is specified below the platform or
below the anchorage.
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Specifications and Design Requirements
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C = 1 .6C LM – 0.6C1
where
C
= clearance for the last worker to fall
CLM =
required clearance for the equivalent lumpedmass fall
C1
= required clearance for a single-worker fall
8. DESIGN ASSUMPTIONS AND ANALYTICAL
METHODS
8.1 Elasticity of Ropes.
8.1 .1 Wire Ropes. Wire ropes may be assumed to
behave in a linear elastic manner, using the elastic
modulus recommended by the manufacturer and in
accordance with the grade and construction of the
wire rope.
8.1 .2 Synthetic Ropes. Synthetic ropes may be
assumed to behave in a linear elastic manner. In
the absence of more accurate analytical methods,
the engineer shall use an elastic modulus that gives
the correct stretch (+/- 5%) at the greatest MAF or
MAL to which the rope will be subjected. The stretch
properties of the rope shall be determined by testing or shall be detailed in information supplied by
the manufacturer.
8.2 Horizontal Lifelines Sags. HLL sags due to
pretension may be determined using catenary or
parabolic equations.
E8.2 For all sags greater than or equal to the cusp
sag (SC), the HLL may be idealized as straight-line
chords, ignoring the slight sags that occur because
of its self-weight (see Figure 6).
8.3 Analytical Methods.
8.3.1 General. The analytical methods described
in Sections 8.3.2 to 8.3.6 may be used to determine
the performance of active fall protection systems.
8.3.2 Dynamic Analysis. Dynamic analysis may
be used on all active fall protection systems.
8.3.3 Energy Analysis. Energy analysis may be
used on all active fall protection systems.
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8.3.4 Static Analysis.
8.3.4.1 General. Static analysis may be used only
on active fall protection systems where the requirements of Section 8.3.4.2 or 8.3.4.3 are met, i.e., so
that the MAF or restraint force applied to the system is known.
8.3.4.2 Travel Restraint Systems. In travel restraint systems, static analysis may be used only
if the requirements of Section 6.2.2 are met, i.e.,
so that the force speci fi ed in that section is applicable.
8.3.4.3 Fall Arrest Systems. In fall arrest systems,
static analysis may be used only when all of the following conditions can be met:
E8.3.4.3 See Appendix A.
8.3.4.3.1 PEAs or SRLs are used to control the
MAF;
8.3.4.3.2 The free fall distance for any worker attached to the system is less than h Max, as calculated
in Section 4.4.3.2; and
E8.3.4.3.2 In systems used by multiple workers
simultaneously, the free fall of the last worker to
fall in a sequential fall is used for comparison to
the allowable hMax. In the absence of more rigorous
methods, the free fall of the last worker may be
taken as the free fall of the first worker plus the
maximum anchorage system displacement to
arrest a lumped-mass fall of all workers prior to the
last worker.
8.3.4.3.3 In HLL systems that incorporate HLLEAs,
E8.3.4.3.3 The following condition should be
considered in HLL systems that incorporate
HLLEAs. The total available deployment of all
HLLEAs used in the system should be greater than
XHEAMin as defined below:
the engineer shall verify that the HLLEA does not
completely deploy. If the HLLEA does completely
deploy, other methods are required to accurately
determine the peak forces in the HLL, which will be
greater than the deployment force of the HLLEA.
X HEAMin = 1.5
1
1-
MFAvg
2TAvg
2 -1
L
where
XHEAMin = the minimum required total deployment of
all HLLEAs used in the system, ft.
M = the “lumping factor” for the maximum number of
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
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workers that may attach to one span of the HLL at
any one time, in accordance with Section E6.3.7.2
FAvg = the average deployment force of the PEA or
SRL, lbs, in accordance with Section 6.3.4.2
TAvg = the average deployment force of the HLLEA,
lbs, in accordance with Section 6.3.6.3
L = the maximum span of the HLL, ft.
8.3.5 Testing and Interpolation Analysis. Forces
and clearance requirements for active fall protection
systems may be based on tests of a prototype of
the actual system or interpolation of test results for
similar systems that bracket the system being designed. Where interpolation of test data is required,
an adequate range of con fi gurations shall be tested, but not fewer than four tests for each parameter
that is being varied, to permit interpolation to an accuracy of +/-5%. Rigid test weight(s) or articulating
mannequins shall have a mass as speci fi ed in Section 6.3.2. For multiple-worker systems, a lumped
mass in accordance with Section 6.3.7.2 may be
used. The test(s) shall use the actual equipment
speci fi ed for use in the active fall protection system.
Full body harnesses may be omitted, provided that
clearances are increased to account for stretch out
of both the worker and the harness. PEAs may be
substituted for SRLs in the tests, provided that testing has proved that the average deployment force
of the chosen lanyard is within +/-5% of the average
deployment force of the SRL.
8.3.6 Other Acceptable Methods. Other analytical methods, based on proven scienti fi c principles,
shall be acceptable if they can be shown to accurately predict the performance of active fall protection systems.
9. REFERENCES
This standard refers to the following publications,
and where such reference is made, it shall be to
the edition listed below, including all amendments
published thereto.
9.1 American Concrete Institute (ACI)
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Specifications and Design Requirements
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9.1 .1 ACI 31 8-05, Building Code Requirements for
Structural Concrete and Commentary
9.2 American Institute of Steel Construction
(AISC)
9.2.1 ANSI/AISC 360-05, Specification for Structural Steel Buildings
9.3 American National Standards Institute (ANSI)
9.3.1 ANSI/SIA A92.29 Vehicle-Mounted Elevating
and Rotating Aerial Devices
9.3.2 ANSI/IWCA I 1 4.1 -2001 , Window Cleaning
Safety
9.4 American Society for Testing and Materials
(ASTM)
9.4.1 A1 023/A1 023M-02, Standard Specification
for Stranded Carbon Steel Wire Ropes for General
Purposes
9.5 Other Publications
9.5.1 PLUS 11 56 Fall arrest systems — Practical
Essentials, by Andrew C. Sulowski
9.5.2 ANSI/ASSE Z359 series of Standards
9.5.3 International Building Code
9.5.4 Arteau, J. (2003). “Protection contre les
chutes de hauteur: absorbeur d’énergie, distance
de freinage, grande hauteur de chute et grande
masse (Protection against falls from height: energy absorber, deceleration distance, large free fall
distance and large mass)”. Actes du 25e congrès
de l’AQHSST, Trois-Rivières, 7–9 May, 2003, pp.
249–260
9.5.5 Sulowski, A. C. Evaluation of Fall Arresting
Systems (Ontario Hydro Research Report 78-98H). Toronto, 1 978
1 0. FIGURES
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Specifications and Design Requirements
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SFD
SDD
ANSI/ASSE Z359.6-2009 American National Standard
Legend:
SDD = Swing-drop distance (drop in height of D-Ring from the onset of the swing to the
point where the worker may impact any structure)
SFD = Swing-fall distance (drop in height of D-Ring from the onset of the swing to the
lowest point it reaches during the swing)
Note: SDD and SFD are calculated assuming a circular (pendular) motion of the worker’s
D-Ring on a fi xed taut length of lifeline. They do not include a drop in height due to free or
deceleration distance
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Figure 1: Swing Falls
ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
for Active Fall Protection Systems
(HI)
(HDA )
D-Ring (Typical)
(FF)
(HA )
MASD
TFD
(XL)
DD
(HI)
(E)
(HF)
(XW)
(XPEA )
(CA )
(CP)
MASD
Top of Highest Obstruction
Legend:
C A = Required clearance below the anchorage
HI
CP
MASD =
DD
= FF - HDA + DD + HF + E
= Required clearance below the platform
= FF + DD + XW + E
= Deceleration Distance
HA
= MASD + XL + XPEA
= Safety margin
= Free Fall
= FFA + FFL + FFC (SEE FIGURE 1, 2
= Height of anchorage above the
H DA
=
HF
=
E
FF
AND
3)
working platform
Height of D-Ring above the anchorage
(H DA is negative if the D-Ring is initially below
the anchorage)
Final height of D-Ring (above the
worker’s toes) at fall arrest
=
TDF
=
XL
XPEA
=
=
XW
=
Initial Height of D-Ring (above the worker’s
surface) at start of fall
Maximum anchorage system displacement
(dynamic de fl ection of horizontal lifelines,
fl exible anchorages)
Total fall distance (of the worker’s
dorsal D-Ring)
Stretch of the lanyard
Deployment of the personal energy
absorber or clutching self-retracting lanyard
Stretch out (due to D-Ring fl ip and slide,
harness stretch, and straightening of
worker’s body)
Figure 2: Clearance (Excluding Swing Fall Distance)
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HI
D-Ring (typical)
XW
HF
HI
D-Ring (typical)
Legend:
H F = Final height of D-Ring (above the worker’s toes) at fall arrest
H I = Initial height of D-Ring of (above the workers surface) at start of fall
XW = Stretch out (due to D-Ring flip and slide, Harness stretch, and
straightening of the worker’s body)
Legend:
H F = Final height of D-Ring (above the worker’s toes)
at fall arrest
H I = Initial height of D-Ring of (above the worker’s
surface) at start of fall
XW = Stretch out (due to D-Ring fl ip and slide, harness
stretch, and straightening of the worker’s body)
Figure 3: Stretch Out
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Specifications and Design Requirements
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(H DA)
D-Ring (Typical)
D-Ring (Typical)
(H DA)
Anchorage
Anchorage
Connector
Free Fall Distance (FF)
Work Platform
Length of Lanyard (LY)
Anchorage
Connector
Length of Lanyard (LY)
Free Fall Distance (FF)
Anchorage
Work Platform
WORKER’S D-RING IS
ABOVE ANCHORAGE
WORKER’S D-RING IS
BELOW ANCHORAGE
LLegend:
d
FF = Free Fall
FFA = Free Fall due to the activation distance of the fall arrester
(to lock onto the vertical lifeline)
FFL = Free Fall resulting from Lanyard slack
= H DA + L Y
H DA = Vertical distance from the D-Ring to where the lanyard connects to the anchorage connector
(H DA is negative if the D-Ring is initially below the fall arrestor)
L Y = Length of Lanyard
Figure 4: Free Fall Resulting from Lanyard Lifeline Slack
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ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
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Anchorage (A)
Anchorage (A)
D-Ring
Anchorage
Connector
Anchorage
Connector
(FFA )
Length of Lanyard (L Y)
(HDA )
Working
Surface
Free Fall Distance (FF)
(FFA )
Length of Lanyard (LY)
Free Fall Distance (FF)
(HDA )
D-Ring
Working Surface
WORKER’S D-RING IS
BELOW ANCHORAGE
WORKER’S D-RING IS
ABOVE ANCHORAGE
Lifeline
Tensioner (LT)
Lifeline
Tensioner (LT)
Legend:
FF = Free Fall
FFA = Free Fall due to the activation distance of the fall arrester
(to lock onto the vertical lifeline)
FFL = Free Fall resulting from lanyard slack
= H DA + L Y
H DA = Vertical distance from the D-Ring to where the lanyard connects to the anchorage connector
LY
(H DA is negative if the D-Ring is initially below the fall arrestor)
= Length of lanyard
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Figure 5: Free Fall on Vertical Lifelines Resulting
from Lanyard Slack and Movement of the Fall Arrest
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Intermediate
Anchorage
End Anchorage
End Anchorage
(FFC)
S Max
(FC)
MASD
MAF
Legend:
F CLegend:= Force required to pull slack out of adjacent spans and hold the initial length of cable into approximate
Fc
= Force
required to pull
slack out
of adjacentthis
spansforce
and hold
length
cable into approximate
straight-line
cords
(because
is the
low,initial
there
is ofnegligible
worker deceleration
straight-line cords (becuase this force is low, there is negligible worker deceleration prior to achieving cusp
FFsag)
C = Free fall distance due to slack in the horizontal lifeline cable
MAF
=
Maximum
Force
distance Arrest
due to slack
in the horizontal lifeline cable
FF C = Free-fall
MAL
Maximum
MAF == Maximum
ArrestArrest
Force Load (a force vector co-linear with the cable)
prior to achieving cusp sag)
MAL == Maximum
S - SArrest Load ( a force vector co-linear with the cable)
Max
C
S Max - S C
S CSC ===Cusp
Cusp
of the horizontal
to all out
slack
beingspans
pulled
adjacent spans and to the initial length of
sag ofsag
the horizontal
lifeline (due tolifeline
all slack(due
being pulled
of adjacent
and toout
theof
initial
rd
length of cable
being pulled into approximate straight-line cords)
being
pulled
cords) to self-weight being balanced by the pretension force)
S I =cable
initial
sag
of into
theapproximate
horizontalstraight-line
lifeline (due
sag of the horizontal
lifeline
(due to self-weight
balanced
by the
pre-tension
S I ==initial
S Max
Maximum
sag of the
horizontal
lifelinebeing
at fall
arrest
(due
to the force)
applied MAF)
41
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Specifications and Design Requirements
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Figure 6: Horizontal Lifeline Sags and Forces
(SC)
(SI)
MAL
ANSI/ASSE Z359.6-2009 American National Standard
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MAL
ANSI/ASSE Z359.6-2009 American National Standard
Specifications and Design Requirements
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APPENDIX A (INFORMATIVE)
COMMENTARY
A.1 Selection of Personal Energy Absorbers
(see Section 4.4.3.2). Section 4.4.3.2 limits the as-
sumption of a 900 lbs (4.0 kN) peak impact force
for ANSI/ASSE Z359.1 energy absorbers to situations where the free fall is 4.6 ft (1 .40 m) or less and
worker mass is 31 0 lbs (1 41 kg) or less. The purpose
of this limitation is to prevent the energy absorber
from bottoming out. When either of the above restrictions cannot be met, the formula provided in
Section 4.4.3.2 allows one to calculate the maximum allowable free fall needed to ensure that the
personal energy absorber (PEA) does not bottom
out. It is based on all of the energy from the fall being consumed by the PEA. The 4.6 ft (1 .40 m) limit
is less than is currently allowed by some regulations
and was determined as follows:
EA.1
1) This Appendix is not a mandatory part of this
standard.
2) This commentary provides additional information
on selected sections in this standard. Fall protection
engineering is a relatively new specialization, and
for this reason the standard has adopted a fairly
conservative approach to fall protection.
3) The authors of this standard expect that some
sections will be refined as time and further research
allow. Users of this standard who believe that it can
be improved are invited to submit proposed changes,
supported by research and sound reasoning, to the
Z359.6 Subcommittee.
A.1 .1 ANSI/ASSE Z359.1 establishes a test for
PEAs that involves dropping a 220 lbs (1 00 kg)
mass 6.0 ft. (1 .83 m). The PEA is permitted to deploy up to 3.5 ft (1 .07 m), with a peak force of up to
900 lbs (4.0 kN).
A.1 .2 Most PEAs sold in U.S. are manufactured for
both the U.S. and Canadian markets (and therefore
limit their maximum deployment to 3.5 ft (1 .07 m)
to meet the ANSI/ASSE Z359.1 (and CSA) requirement).
A.1 .3 Most PEAs deploy at an average force of 600
to 800 lbs (2.67 to 3.56 kN).
A.1 .4 Given the commentary in Section A.7, the
ANSI Z359 Full Committee has concluded that a
282 lbs (1 28 kg) mass should be used to simulate
the effect from a 31 0 lbs (1 41 kg) worker. This is a
departure from the previously accepted assumption
that a 220 lbs (1 00 kg) test mass would properly represent a 31 0 lbs (1 41 kg) worker.
A.1 .5 The formula in Section 4.4.3.2 yields a maxi-
mum allowable free fall of 4.6 ft (1 .40 m), based on
FAvg = 720 lbs (3.2 kN), XMax = 3.5 ft (1 .07 m), and m
= 31 0 lbs (1 41 kg).
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A.2 Self-Retracting Lanyards Used in Fall Arrest
Systems (see Section 4.4.4.2). Section 4.4.4.2
restricts the use of self-retracting lanyards (SRLs)
that meet the requirements of ANSI/ASSE Z359.1 .
These SRLs are restricted to fall arrest systems
where the SRL is anchored above the worker (such
that the free fall is the lock-off distance of the SRL).
The reasoning behind this requirement is as follows:
A.2.1 The testing method in ANSI/ASSE Z359.1
subjects SRLs to a free fall of only 2.0 ft (0.61 m)
plus the lock-off of the SRL. The maximum arrest
force (MAF) is not measured (which would determine the MAF seen by the worker). Most of these
devices include a label stating that the impact force
to the worker’s body is kept below 900 lbs (4.0 kN),
but only if the device is anchored above the worker
prior to the drop, so that the free fall is limited to the
lock-off distance of the SRL.
A.3 Horizontal Lifeline Energy Absorbers Used
in Fall Arrest Systems (see Section 4.4.8.2). Sec-
tion 4.4.8.2 provides the following formula for limiting the maximum span of horizontal lifelines (HLLs)
when horizontal lifeline energy absorbers (HLLEAs)
are used:
Lmax = 4.6
16
T
Mw
9.75 avg
2
-4
where
Lmax = maximum span, ft.
TAvg = average deployment force of the HLLEA, lbs,
in accordance with Section 6.3.6.3
M = the “lumping factor” for the maximum number
of workers that may be attached to one span of the
HLL at any one time, in accordance with Section
E6.3.7.2
w = weight of one worker, lbs, in accordance with
Section 6.3.2
Some members of the CSA Z259 Technical Com-
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mittee have tested HLLEAs on long spans where,
due to the properties of the energy absorber, the
system has become unstable beyond certain span
lengths and sagged well past a simple balance of
forces between the PEA and HLLEA.
The above formula was derived using the following
progression of theoretical arguments:
A.3.1 A body being accelerated by gravity will continue to accelerate downward until acted on by an
upward force that is greater than the weight of the
falling body.
A.3.2 Because there is always elasticity in actual
fall arrest anchorage systems, the force applied to
arrest the falling body is related to the de fl ection of
the system.
A.3.3 In the case of HLLs, and particularly HLLs
with HLLEAs, signi fi cant sag is required before the
system reacts with a force greater than or equal to
the weight of the falling body (the sag beyond which
the falling body begins to slow).
A.3.4 The worst case is a mid-span fall.
A.3.5 The cable will defl ect into a V shape of two
straight lines.
A.3.6 The average cable tension is equal to the average deployment force of the HLLEA (usually less
than the nominal [peak] deployment force).
A.3.7 The average vertical arresting force applied
to arrest the falling body is equal to the sum of the
vertical components of the average cable tension.
A.3.8 The sag at which the system begins to slow
the falling mass is the sag where the average vertical arresting force applied by the cable equals
the weight of the falling mass. HLLs meeting the
requirements of this formula will begin to slow the
falling worker(s) within the fi rst 4.0 ft (1 .22 m) of sag.
The 4.0 ft (1 .22 m) value was selected to ensure
that the PEA does not bottom out in a fall with a 6.0
ft (1 .83 m) lanyard connected to an HLL at waist
height. With a few exceptions, HLLEAs on the market are already limited by their manufacturers to
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spans shorter than those permitted by this formula.
Readers should note that the fi nal sag of the HLL at
fall arrest is typically two to four times the sag where
the system begins to slow the falling body.
A.4 Determination of Factored Load Effects (see
Section 5.2.3). Because fall arrest systems are
subjected to dynamic rather than static forces, and
because of the use of PEAs and HLLEAs to limit
the forces in fall arrest systems, it was necessary
to apply the load factors to the load effects rather
than to the loads themselves. This is contrary to the
limit states design methodology in the International
Building Code 2003, where the load factor is applied to the weight of the falling mass. (If this approach were used in a system that includes a PEA,
the maximum impact force could be identical to that
calculated for the unfactored weight, resulting in no
factor of safety for the strength of the system.)
The overall factor of safety for the strength of the
system is equal to the ratio of the load factor, α , divided by the capacity-reduction factor, Ø. The load
factor applied to the load effect, α A, was chosen
to be 1 .5 for consistency with load factors used in
other American design codes. It was not developed
based on a statistical review of the variability of
loadings. The authors of this standard believe that
the capacity-reduction factors used in ANSI/AISC360-05 and ACI-31 8 generally maintain an overall
factor of safety greater than or equal to 2.0 between
the applied loading and the ultimate strength of the
supporting system, which agrees with the fall protection regulations in most jurisdictions where the
factor of safety has been speci fi ed, e.g., the United
States (OSHA).
Section 5.2.3 speci fi es capacity-reduction factors
for materials not covered by ANSI. These factors
were selected with a view to maintaining a consistent factor of safety of at least 2.0, in accordance
with the factors of safety that have been used for
other materials. Applicable references are as follows:
A.4.1 Section 3.2.2 of ANSI/SIA A92.2 for vehicle-
mounted aerial devices speci fi es a structural factor of safety of at least 5.0 for fi berglass. This standard therefore uses a capacity-reduction factor of
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0.3, which, in combination with the load factor of
1 .5, matches the factor of safety of 5.0 in ANSI/SIA
A92.2.
A.4.2 Draft standand ANSI/ASSE Z359.17-20XX
requires a factor of safety of 3.0 for synthetic rope.
A capacity-reduction factor of 0.5 was therefore selected, in order to be consistent with ANSI/ASSE
Z359.1 7-20XX.
A.4.3 A capacity-reduction factor of 0.6 was select-
ed for other ductile materials not covered by U.S.
design codes to provide an overall factor of safety
of 2.5.
A.4.4 Although ACI-31 8 suggests a capacity-reduc-
tion factor of 0.8 against the ultimate strength of prestressing strands, a value of 0.75 was selected for
all wire rope cables to maintain a minimum factor of
safety of 2.0.
A.5 Swing Falls (see Section 5.3). The “swing velocity” of a worker is created by the potential energy
gained by the worker’s drop in elevation during the
swing. The swing velocity is therefore identical to
the velocity attained in a vertical fall for the same
drop in elevation.
EA.5 U.S. legislative bodies (OSHA) require fall
protection above threshold heights that are typically between 4.0 and 1 0.0 ft.
The important difference with swing falls is that the
impact will always be perpendicular to the main axis
of the body, whereas in vertical falls the orientation
of the body on impact may be random but can be
affected by the twisting and tumbling of the falling
worker as he or she attempts to land in the strongest possible orientation (feet fi rst).
The Committee therefore believed that a conservative limit on the maximum permissible elevation drop
during a swing fall was warranted, but also needed
to allow a reasonable amount of lateral movement
from an overhead anchorage. A maximum swing
drop distance of 4.0 ft was chosen.
A.6 Maximum Arrest Force (see Section 5.4.2.2).
Sulowski (1 978) and other sources have recommended that the maximum impact to a worker wearing a properly fi tted full body harness should not
exceed 9 g. The current maximum force accepted
virtually everywhere in North America is 1 ,800 lbs
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(8 kN), which ensures that no more than 9 g is felt
by the worker so long as his or her body mass is at
least 200 lbs (91 kg). There is certainly a signi fi cant
proportion of the working population that weighs
less than this.
For most SRLs, and all energy absorbers meeting
ANSI/ASSE Z359.1 requirements, the maximum
impact force that a worker should experience with a
dry energy absorber at room temperature is 900 lbs
(4.0 kN), thus keeping impacts below 9 g for body
masses down to 1 00 lbs (45 kg).
For large workers or long free falls where suffi cient
clearance exists, two or more energy absorbers
meeting the requirements of ANSI/ASSE Z359.1
could be used in series. This should be done only
under the direction of a engineer. See Arteau (2003)
and CSA PLUS 11 56.
A.7 Design Mass of Workers (see Section 6.3.2).
This standard radically departs from other testing
and design standards in that the mass employed to
represent a 31 0 lbs (1 41 kg) worker is 220 lbs (1 00
kg).
ANSI/ASSE Z359.1 -2007 and standards in the CSA
Z259 series published before 2003 provide for the
dropping of 220 lbs rigid test masses to simulate the
effect from a 31 0 lbs (1 41 kg) worker (the heaviest
worker that these standards are designed to protect). The 220 lbs (1 00 kg) test mass is based on
a commonly accepted principle that a human body
will stretch and absorb energy, so that the impact
forces from a person should be less than those from
a rigid test mass of the same weight. The rule adopted by testing standards and some OSHA regulations speci fi es a relationship of 1 .4 between the
impact forces generated by a test mass and those
generated by a person of the same weight. This factor, established several decades ago, was based on
dynamic testing using non-energy-absorbing lanyards.
It has been assumed that the force relationship also
translates into a mass relationship of 1 .4 (e.g., a 220
lbs (1 00 kg) weight will have the same effect on a fall
arrest system as a 31 0 lbs (1 41 kg) worker).
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One member of the CSA Technical Committee
stated that he had done some very limited testing
comparing the deployment of energy absorbers using rigid test torsos and human subjects and found
virtually no difference between the two. A preliminary examination of the historical basis of the 1 .4
factor revealed a tremendous variation in the test
data, and showed that 1 .4 was more a consensus
value picked by regulators than a number clearly
proved by testing. (Testing of rope lanyards at the
time the 1 .4 factor was chosen showed a variation
of 1 .1 to 1 .8.)
The Technical Committee concluded that whereas
one would expect a human body to absorb some
fall energy because of its internal elasticity, energy
absorber deployments might not re fl ect this, for two
reasons:
a) The drop tests that led to the 1 .4 factor probably produced greater impact forces on the human
body (perhaps up to 1 ,800 lbs (8.0 kN) or more), in
which case the in fl uence of the elasticity of the human body would be stronger. With the lesser forces
of a energy absorber (nominally 900 lbs, and likely
closer to 630 to 81 0 lbs), it is probable that the force
takes up all of the initial slack in the human body, all
of which lowers the body’s center of mass, generating some fall energy (which may be of the same
magnitude as the energy the body absorbed as it
fl exed). It is only at higher forces that tendons and
joints bottom out, leading to increased compression
or crushing of cartilage, stretching of tendons, and
stretching of muscles beyond their range of easy
movement. Thus where the forces are greater, the
body may absorb or dissipate fall energy at a greater rate than is produced by the additional lowering
of the center of gravity (leading to development of
the 1 .4 factor).
b) When a person wears a full body harness with
a sliding D-Ring, the harness stretches and the
D-Ring slides, lowering the body by perhaps 6 to
24 inches (0.1 5 to 0.61 m), depending on the elasticity of the harness. This fl ex of the harness and
sliding of the D-Ring occurs at relatively low forces
and therefore does not absorb as much energy as
is gained by the additional lowering of the person’s
center of mass.
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After further discussion, it was agreed that this standard should not rely on the 1 .4 factor for forces or for
equivalency of test (or design calculation) masses,
particularly since energy absorbers are now common place and the basis of the 1 .4 factor was testing with non-energy-absorbing lanyards.
In the face of test data, and with plausible explanations why a person in a harness should cause the
same deployment of a energy absorber as a rigid
test mass, the consensus vote of the Full Committee was to reduce the 1 .4 factor to 1 .1 .
A.8 Equivalent Lumped Mass (see Section
6.3.7.2). For multiple-worker falls, a common ap-
proach is to lump the masses of workers together
into a single mass that may then be analyzed using
techniques for a single-worker fall.
Research on multiple-worker falls has shown that
it was virtually impossible to have a simultaneous
peak impact involving multiple workers even when
the goal of the test is to create a simultaneous impact.
The information in Section 6.3.7.2.2 is consistent
with the BS 8347-2005.
A.9 Deployment of Personal Energy Absorbers and Self-Retracting Lanyards (see Section
7.2.3.4). If the designer of a fall arrest system has
met the requirements of Section 4.4.3.2, the PEA
will not fully deploy, and for this reason the designer
may conservatively assume full deployment in calculating clearance requirements.
If the designer is using energy analysis, dynamic
analysis, or testing and interpolation analysis, the
amount of deployment of the energy absorber can
be accurately calculated.
Static analysis, however, will not enable the designer to determine the amount of fall energy absorbed by other components of the fall arrest system (meaning that the designer cannot accurately
calculate the deployment of the energy absorber).
The equation in Section 7.2.3.4 is another version
of the equation in Section 4.4.3.2.2.2, algebraically
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manipulated to solve for PEA deployment rather
than free fall height.
A.10 Stretch Out (see Section 7.2.4). The stretch
out of the worker and harness was kept as a separate factor so that designers account for:
A.1 0.1 Situations where a worker using an SRL anchored overhead might fall from a kneeling or lying
position. These situations require more clearance
below the working platform than situations where
the worker falls from a standing position; and
A.1 0.2 The stretch of a full body harness, which
can vary tremendously (typically from 6 to 30 inches) depending on the harness design and the elasticity of the webbing.
A.11 Safety Margin for Flexible Anchorage Systems (see Section 7.2.6.2). The safety margins for
fl exible
anchorage systems are adjusted to account
for the anticipated worst-case inaccuracies expected for the various analytical methods. The CMASD
factors in this standard re fl ect the consensus of the
Working Group and do not have a rational or scienti fi c basis. They were chosen as a starting point for
this edition of the standard, because of their use by
some Committee members. They may be subject
to re fi nement in future editions if research into this
topic is undertaken by interested parties and submitted to the Committee.
A.1 2 Clearance for Equivalent Lumped-Mass
Simulation of Multiple-Worker Falls (see Section
7.2.7). In a sequential fall on a fl exible anchorage
system, the last worker falling will have the greatest
free fall because the anchorage system (such as an
HLL) will have been moved by the preceding falls.
A.1 3 Condition Required for Static Analysis
of Fall Arrest Systems (see Section 8.3.4.3.3).
The equation in Section 8.3.4.3.3 was developed
to ensure that an HLLEA will not deploy more than
two-thirds of its maximum available deployment in
a worst-case fall. This requirement permits users
of static analysis to safely assume that the maximum tension in the HLL will be TMax (See Section
6.3.6.2).
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Should the HLLEA bottom out, static analysis no
longer applies. In that case, the designer would use
energy, dynamic, or testing and interpolation analytical methods to accurately determine the peak
forces in the HLL, which will be greater than the deployment force of the HLLEA.
APPENDIX B (INFORMATIVE)
BIBLIOGRAPHY
B.1 Riches, D. (2002) “Analysis and evaluation of
different types of test surrogate employed in the dynamic performance testing of fall arrest equipment”.
Health & Safety Executive HSE (United Kingdom),
Research Report CRR 411 /2002.
E B.1 This Appendix is not a mandatory part of this
standard.
B.2 Corden, C.H.H. “Wire rope grip terminations”.
Health and Safety Executive, May 1 996
B.3 Sulowski, A.C., and Amphoux, M. (eds). “Fundamentals of Fall Protection”. International Society
for Fall Protection, Toronto, June 1 991 .
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