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SEISMIC RESTRAINTMANUAL

GUIDELINES FORMECHANICAL SYSTEMS

SHEET METAL AND AIR CONDITIONING CONTRACTORS’NATIONAL ASSOCIATION, INC.

www.smacna.org

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SEISMIC RESTRAINTMANUAL

GUIDELINES FORMECHANICAL SYSTEMS

THIRD EDITION − MARCH, 2008


4201 Lafayette Center DriveChantilly, VA 20151−1209

www.smacna.org



SEISMIC RESTRAINT MANUALGUIDELINES FOR MECHANICAL SYSTEMS

COPYRIGHT � SMACNA 2008All Rights Reserved

by


4201 Lafayette Center DriveChantilly, VA 20151−1209

Printed in the U.S.A.

FIRST EDITION − DECEMBER 1991SECOND EDITION − FEBRUARY 1998

THIRD EDITION − MARCH 2008

Except as allowed in the Notice to Users and in certain licensing contracts, no part of this book may bereproduced, stored in a retrievable system, or transmitted, in any form or by any means, electronic,

mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher.



iiiSeismic Restraint Manual • Third Edition

FOREWORD

HISTORY OF THE GUIDELINES

During the San Fernando Earthquake of 1971, four of the eleven medical facilities in the area were so badly damaged

that they had to be evacuated. As a result, the State of California began to require that hospitals be built to remain

operational after an earthquake. Part of this mandate required stabilizing the mechanical and piping systems.

To provide technical guidance for economical bracing methods, the Sheet Metal Industry Fund of Los Angeles pub-

lished Guidelines for Seismic Restraint of Mechanical Systems in 1976. This document was pre−approved by the Cali-

fornia Office of Statewide Health Planning and Development (OSHPD). A later edition, in 1982, co−published by the

Plumbing and Piping Industry Council, Inc. (PPIC), expanded the bracing guidelines for piping. For several years,

these were the only available guidelines, and they were used nationwide even though they had been designed for Cali-

fornia’s unusually severe seismic conditions. The result was that, in many parts of the country, seismic restraints were

being over−designed at unnecessary expense.

To remedy this, SMACNA formed the Seismic Restraint Task Force to study the feasibility of developing national

standards. In April 1990, the task force recommended that SMACNA develop and publish this manual of seismic re-

straint guidelines. It was to include non−technical explanations of seismic forces, and the tables from the old guidelines

would be expanded to include electrical conduit and larger ducts. Then, for about a year, the manual was developed

by the task force and consulting engineers, with input from a broad spectrum of users in the sheet metal and plumbing

industries.

This third edition has been revised to conform to the requirements in the International Building Code 2006. The ap-

plication tables have been revised and a fourth table added to provide bracing provisions for four different levels of

anticipated force levels. Appendix A is provided to assist the design professional in the specification/selection of the

bracing levels required.

PURPOSE OF THE GUIDELINES

In the past, design for protection against earthquake damage was confined primarily to the structural systems of build-

ings. However, even in buildings that did not collapse, it was discovered that the destruction of nonstructural elements,

such as heating ducts and gas pipes, could cause great damage to the building and even loss of life. Damage to the

mechanical systems could mean that a building might be uninhabitable for weeks or months. As a result, seismic con-

cerns now include restraints for ductwork and piping in buildings.

Also in recent years, there has been growing concern about the possibility of earthquakes in parts of the country that

are not usually thought of as �earthquake zones." Areas of the South and Midwest, for example, are beginning to take

precautions because of the dangerous consequences to life and property in case an earthquake does occur. Since 1988,

all the major national building codes have required bracing for pipes and ducts. As engineers and builders in these areas

look for guidance in making buildings safer, they naturally turn to California, with its longer history of designing for

earthquakes. However, because California has such severe, frequent earthquakes, its standards may be too strict for

other parts of the country.

Until now, designers have had little choice but to use California’s strict guidelines or use none at all. The purpose of

this manual is to provide a flexible set of guidelines that accommodates all parts of the country. Within a single format,

very low−risk and very high−risk areas can be easily and equally accommodated. The guidelines will enable designers

and contractors to determine the regionally−appropriate restraints for sheet metal ducts, piping, and conduit, so that

they are more likely to maintain their integrity and remain attached to the building’s structure during an earthquake.

ROLES OF CONSTRUCTION PROFESSIONALS

In order to accommodate a variety of conditions, these guidelines are somewhat more complicated than the original

manual. It now takes more than a simple cookbook procedure to determine the proper restraints. One step in the re-

straint design process, determining the proper Seismic Hazard Level (SHL), requires professional judgment and con-



iv Seismic Restraint Manual • Third Edition

sultation with local jurisdictions. A sheet metal or mechanical contractor cannot be expected to carry the burden of

this judgment. Rather, the design professional must take responsibility for determining the SHL. Conditions not cov-

ered in this manual are the responsibility of the design professional.

WHAT IS NOT IN THIS MANUAL

This manual is not intended to cover the ordinary supports for ducts and pipes required for gravity loads. (Some have

been included for reference only.) The only restraints shown in these tables and drawings are those needed to provide

the extra support for seismic loads.

This manual also does not cover the seismic restraints for fire sprinklers and equipment. Fire sprinklers have been

covered by the National Fire Protection Association (NFPA) since 1939.




v Seismic Restraint Manual • Third Edition

SEISMIC RESTRAINT TASK FORCERobert P. Vlick, Chairman

ACCO Engineered Systems

Tustin, California

Tye Halverson

Southwest Air Conditioning, Inc.

Las Vegas, Nevada

Kailasam Senthil

Critchfield Mechanical, Inc.

Menlo Park, California

Robert J. Wasilewski, Staff Liaison

SMACNA

Chantilly, Virginia

OTHER CONTRIBUTORSJohn A. Martin & Associates

Structural Engineers

Eric D. Brown

950 South Grand Avenue

Los Angeles, California

The Sheet Metal Industry Fund of Los Angeles, CA

The Plumbing and Piping Industry Council, Inc.

Los Angeles, California



vi Seismic Restraint Manual • Third Edition

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viiSeismic Restraint Manual • Third Edition

NOTICE TO USERSOF THIS PUBLICATION

1. DISCLAIMER OF WARRANTIES

a) The Sheet Metal and Air Conditioning Contractors’ National Association (�SMACNA") provides its product for informationalpurposes.

b) The product contains �Data" which is believed by SMACNA to be accurate and correct but the data, including all information,ideas and expressions therein, is provided strictly �AS IS," with all faults. SMACNA makes no warranty either express or impliedregarding the Data and SMACNA EXPRESSLY DISCLAIMS ANY IMPLIED WARRANTIES OF MERCHANTABILITY ORFITNESS FOR PARTICULAR PURPOSE.

c) By using the data contained in the product user accepts the Data �AS IS" and assumes all risk of loss, harm or injury that may resultfrom its use. User acknowledges that the Data is complex, subject to faults and requires verification by competent professionals, andthat modification of parts of the Data by user may impact the results or other parts of the Data.

d) IN NO EVENT SHALL SMACNA BE LIABLE TO USER, OR ANY OTHER PERSON, FOR ANY INDIRECT, SPECIAL ORCONSEQUENTIAL DAMAGES ARISING, DIRECTLY OR INDIRECTLY, OUT OF OR RELATED TO USER’S USE OFSMACNA’S PRODUCT OR MODIFICATION OF DATA THEREIN. This limitation of liability applies even if SMACNA has beenadvised of the possibility of such damages. IN NO EVENT SHALL SMACNA’S LIABILITY EXCEED THE AMOUNT PAID BYUSER FOR ACCESS TO SMACNA’S PRODUCT OR $1,000.00, WHICHEVER IS GREATER, REGARDLESS OF LEGALTHEORY.

e) User by its use of SMACNA’s product acknowledges and accepts the foregoing limitation of liability and disclaimer of warrantyand agrees to indemnify and hold harmless SMACNA from and against all injuries, claims, loss or damage arising, directly or indi-rectly, out of user’s access to or use of SMACNA’s product or the Data contained therein.

2. ACCEPTANCE

This document or publication is prepared for voluntary acceptance and use within the limitations of application defined herein, andotherwise as those adopting it or applying it deem appropriate. It is not a safety standard. Its application for a specific project is contin-gent on a designer or other authority defining a specific use. SMACNA has no power or authority to police or enforce compliance withthe contents of this document or publication and it has no role in any representations by other parties that specific components are, infact, in compliance with it.

3. AMENDMENTS

The Association may, from time to time, issue formal interpretations or interim amendments, which can be of significance betweensuccessive editions.

4. PROPRIETARY PRODUCTS

SMACNA encourages technological development in the interest of improving the industry for the public benefit. SMACNA does not,however, endorse individual manufacturers or products.

5. FORMAL INTERPRETATION

a) A formal interpretation of the literal text herein or the intent of the technical committee or task force associated with the documentor publication is obtainable only on the basis of written petition, addressed to the Technical Resources Department and sent to theAssociation’s national office in Chantilly, Virginia. In the event that the petitioner has a substantive disagreement with the interpreta-tion, an appeal may be filed with the Technical Resources Committee, which has technical oversight responsibility. The request mustpertain to a specifically identified portion of the document that does not involve published text which provides the requested informa-tion. In considering such requests, the Association will not review or judge products or components as being in compliance with thedocument or publication. Oral and written interpretations otherwise obtained from anyone affiliated with the Association are unoffi-cial. This procedure does not prevent any committee or task force chairman, member of the committee or task force, or staff liaisonfrom expressing an opinion on a provision within the document, provided that such person clearly states that the opinion is personaland does not represent an official act of the Association in any way, and it should not be relied on as such. The Board of Directors ofSMACNA shall have final authority for interpretation of this standard with such rules or procedures as they may adopt for processingsame.

b) SMACNA disclaims any liability for any personal injury, property damage, or other damage of any nature whatsoever, whetherspecial, indirect, consequential or compensatory, direct or indirectly resulting from the publication, use of, or reliance upon this docu-ment. SMACNA makes no guaranty or warranty as to the accuracy or completeness of any information published herein.

6. APPLICATION

a) Any standards contained in this publication were developed using reliable engineering principles and research plus consultationwith, and information obtained from, manufacturers, users, testing laboratories, and others having specialized experience. They are



viii Seismic Restraint Manual • Third Edition

subject to revision as further experience and investigation may show is necessary or desirable. Construction and products which com-ply with these Standards will not necessarily be acceptable if, when examined and tested, they are found to have other features whichimpair the result contemplated by these requirements. The Sheet Metal and Air Conditioning Contractors’ National Association andother contributors assume no responsibility and accept no liability for the application of the principles or techniques contained in thispublication. Authorities considering adoption of any standards contained herein should review all federal, state, local, and contractregulations applicable to specific installations.

b) In issuing and making this document available, SMACNA is not undertaking to render professional or other services for or onbehalf of any person or entity. SMACNA is not undertaking to perform any duty owed to any person or entity to someone else. Anyperson or organization using this document should rely on his, her or its own judgement or, as appropriate, seek the advice of a compe-tent professional in determining the exercise of reasonable care in any given circumstance.

7. REPRINT PERMISSION

Non−exclusive, royalty−free permission is granted to government and private sector specifying authorities to reproduce only anyconstruction details found herein in their specifications and contract drawings prepared for receipt of bids on new construction andrenovation work within the United States and its territories, provided that the material copied is unaltered in substance and that thereproducer assumes all liability for the specific application, including errors in reproduction.

8. THE SMACNA LOGO

The SMACNA logo is registered as a membership identification mark. The Association prescribes acceptable use of the logo andexpressly forbids the use of it to represent anything other than possession of membership. Possession of membership and use of thelogo in no way constitutes or reflects SMACNA approval of any product, method, or component. Furthermore, compliance of anysuch item with standards published or recognized by SMACNA is not indicated by presence of the logo.



TABLE OF CONTENTS



TABLE OF CONTENTS

ixSeismic Restraint Manual • Third Edition

FOREWORD iii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SEISMIC RESTRAINT TASK FORCE v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

NOTICE TO USERS OF THIS PUBLICATION vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TABLE OF CONTENTS ix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 1 INTRODUCTION Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.1 OVERVIEW 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 WHAT ARE SEISMIC LOADS? 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 WHAT HAPPENS DURING AN EARTHQUAKE? 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 HOW TO RESIST SEISMIC LOADS 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 KINDS OF BRACING 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 WHY DIFFERING REQUIREMENTS? 1.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 2 INSTRUCTIONS FOR USING THE GUIDELINES

2.1 THE SEISMIC HAZARD LEVEL (SHL) 2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 HOW TO READ THE SIZING TABLES 2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 USING THE SIZING TABLES 2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 EXAMPLE: DUCT BRACING 2.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 3 GENERAL REQUIREMENTS

3.1 GENERAL REQUIREMENTS 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 MATERIAL SPECIFICATIONS 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 GENERAL REQUIREMENTS FOR BRACING OF DUCTS 3.2 . . . . . . . . . . . . . . . . . . . . . 3.4 GENERAL REQUIREMENTS FOR BRACING OF PIPES 3.3 . . . . . . . . . . . . . . . . . . . . . . 3.5 ITEMS TO BE PROVIDED BY THE DESIGN PROFESSIONALS 3.4 . . . . . . . . . . . . . . . 3.6 NOTES ON ATTACHMENT TO THE BUILDING STRUCTURE 3.4 . . . . . . . . . . . . . . . . . .

CHAPTER 4 DETAIL DRAWINGS OF BRACING

4.1 INSTRUCTIONS FOR BRACING INDIVIDUALLY SUPPORTED PIPE 4.1 . . . . . . . . . . .

CHAPTER 5 TABLES FOR SEISMIC HAZARD LEVEL A

5.1 USE OF TABLES 5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 6 TABLES FOR SEISMIC HAZARD LEVEL B

6.1 USE OF TABLES 6.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 7 TABLES FOR SEISMIC HAZARD LEVEL C

7.1 USE OF TABLES 7.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 8 TABLES FOR SEISMIC HAZARD LEVEL D

8.1 USE OF TABLES 8.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



x Seismic Restraint Manual • Third Edition

CHAPTER 9 DETAILS OF CONNECTIONS TO STRUCTURAL MEMBERS Page. . . . . . . . . . . . . . . . .

9.1 INTRODUCTION 9.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 10 MISCELLANEOUS CONNECTIONS

10.1 INTRODUCTION 10.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDIX A DETERMINING THE SEISMIC HAZARD LEVEL



xiSeismic Restraint Manual • Third Edition

TABLES Page 3−1 Standard Sheet Metal Gages 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3−2 Minimum Allowable Cable Strength 3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3−3 Minimum Allowable Design Values for Expansion Anchors 3.2 . . . . . . . . . . . . . . . . . . . . . . 5−1 Side Bracing for Rectangular Ducts, SHL A, L=2 ft 8 in. (Max.) 5.2 . . . . . . . . . . . . . . . . . . 5−1M Side Bracing for Rectangular Ducts, SHL A, L=.81 m (Max.) 5.3 . . . . . . . . . . . . . . . . . . . . 5−2 Side Bracing for Rectangular Ducts with Rod Hangers, SHL A 5.4 . . . . . . . . . . . . . . . . . . 5−2M Side Bracing for Rectangular Ducts with Rod Hangers, SHL A 5.5 . . . . . . . . . . . . . . . . . . 5−3 Center Bracing for Rectangular Ducts, SHL A, L=7 ft 5.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−3M Center Bracing for Rectangular Ducts, SHL A, L=2.1 m 5.7 . . . . . . . . . . . . . . . . . . . . . . . . 5−4 Center Bracing for Rectangular Ducts, SHL A, L=10 ft 5.8 . . . . . . . . . . . . . . . . . . . . . . . . . 5−4M Center Bracing for Rectangular Ducts, SHL A, L=3.0 m 5.9 . . . . . . . . . . . . . . . . . . . . . . . . 5−5 Floor Supported Ducts, SHL A 5.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−5M Floor Supported Ducts, SHL A 5.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−6 Bracing for Round Ducts, SHL A 5.12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−6M Bracing for Round Ducts, SHL A 5.13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−7 Schedule for Bracing Pipes and Conduit, SHL A 5.14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−7M Schedule for Bracing Pipes and Conduit, SHL A 5.15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−8 Schedule for Bracing Pipes on Trapeze, SHL A 5.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−8M Schedule for Bracing Pipes on Trapeze, SHL A 5.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−9 Floor Supported Pipes, SHL A 5.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5−9M Floor Supported Pipes, SHL A 5.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−1 Side Bracing for Rectangular Ducts, SHL B, L=2 ft 8 in. (Max.) 6.2 . . . . . . . . . . . . . . . . . . 6−1M Side Bracing for Rectangular Ducts, SHL B, L=.81 m (Max.) 6.3 . . . . . . . . . . . . . . . . . . . . 6−2 Side Bracing for Rectangular Ducts with Rod Hangers, SHL B 6.4 . . . . . . . . . . . . . . . . . . 6−2M Side Bracing for Rectangular Ducts with Rod Hangers, SHL B 6.5. . . . . . . . . . . . . . . . . . 6−3 Center Bracing for Rectangular Ducts, SHL B, L=7 ft 6.6. . . . . . . . . . . . . . . . . . . . . . . . . . . 6−3M Center Bracing for Rectangular Ducts, SHL B, L=2.1 m 6.7. . . . . . . . . . . . . . . . . . . . . . . . 6−4 Center Bracing for Rectangular Ducts, SHL B, L=10 ft 6.8. . . . . . . . . . . . . . . . . . . . . . . . . 6−4M Center Bracing for Rectangular Ducts, SHL B, L=3.0 m 6.9. . . . . . . . . . . . . . . . . . . . . . . . 6−5 Floor Supported Ducts, SHL B 6.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−5M Floor Supported Ducts, SHL B 6.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−6 Bracing for Round Ducts, SHL B 6.12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−6M Bracing for Round Ducts, SHL B 6.13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−7 Schedule for Bracing Pipes and Conduit, SHL B 6.14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−7M Schedule for Bracing Pipes and Conduit, SHL B 6.15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−8 Schedule for Bracing Pipes on Trapeze, SHL B 6.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−8M Schedule for Bracing Pipes on Trapeze, SHL B 6.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−9 Floor Supported Pipes, SHL B 6.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6−9M Floor Supported Pipes, SHL B 6.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7−1 Side Bracing for Rectangular Ducts, SHL C, L=2 ft 8 in. (Max.) 7.2 . . . . . . . . . . . . . . . . . . 7−1M Side Bracing for Rectangular Ducts, SHL C, L=.81 m (Max.) 7.3 . . . . . . . . . . . . . . . . . . . . 7−2 Side Bracing for Rectangular Ducts with Rod Hangers, SHL C 7.4 . . . . . . . . . . . . . . . . . . 7−2M Side Bracing for Rectangular Ducts with Rod Hangers, SHL C 7.5 . . . . . . . . . . . . . . . . . . 7−3 Center Bracing for Rectangular Ducts, SHL C, L=7 ft 7.6 . . . . . . . . . . . . . . . . . . . . . . . . . . 7−3M Center Bracing for Rectangular Ducts, SHL C, L=2.1 m 7.7 . . . . . . . . . . . . . . . . . . . . . . . . 7−4 Center Bracing for Rectangular Ducts, SHL C, L=10 ft 7.8 . . . . . . . . . . . . . . . . . . . . . . . . . 7−4M Center Bracing for Rectangular Ducts, SHL C, L=3.0 m 7.9 . . . . . . . . . . . . . . . . . . . . . . . . 7−5 Floor Supported Ducts, SHL C 7.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7−5M Floor Supported Ducts, SHL C 7.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7−6 Bracing for Round Ducts, SHL C 7.12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



xii Seismic Restraint Manual • Third Edition

7-6M Bracing for Round Ducts, SHL C 7.13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Schedule for Bracing Pipes and Conduit, SHL C 7.14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7M Schedule for Bracing Pipes and Conduit, SHL C 7.15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8 Schedule for Bracing Pipes on Trapeze, SHL C 7.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8M Schedule for Bracing Pipes on Trapeze, SHL C 7.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9 Floor Supported Pipes, SHL C 7.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9M Floor Supported Pipes, SHL C 7.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 Side Bracing for Rectangular Ducts, SHL D, L=2 ft 8 in. (Max.) 8.2 . . . . . . . . . . . . . . . . . . 8-1M Side Bracing for Rectangular Ducts, SHL D, L=.81 m (Max.) 8.3 . . . . . . . . . . . . . . . . . . . . 8-2 Side Bracing for Rectangular Ducts with Rod Hangers, SHL D 8.4 . . . . . . . . . . . . . . . . . . 8-2M Side Bracing for Rectangular Ducts with Rod Hangers, SHL D 8.5 . . . . . . . . . . . . . . . . . . 8-3 Center Bracing for Rectangular Ducts, SHL D, L=7 ft 8.6 . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3M Center Bracing for Rectangular Ducts, SHL D, L=2.1 m 8.7 . . . . . . . . . . . . . . . . . . . . . . . . 8-4 Center Bracing for Rectangular Ducts, SHL D, L=10 ft 8.8 . . . . . . . . . . . . . . . . . . . . . . . . . 8-4M Center Bracing for Rectangular Ducts, SHL D, L=3.0 m 8.9 . . . . . . . . . . . . . . . . . . . . . . . . 8-5 Floor Supported Ducts, SHL D 8.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5M Floor Supported Ducts, SHL D 8.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6 Bracing for Round Ducts, SHL D 8.12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6M Bracing for Round Ducts, SHL D 8.13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7 Schedule for Bracing Pipes and Conduit, SHL D 8.14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7M Schedule for Bracing Pipes and Conduit, SHL D 8.15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8 Schedule for Bracing Pipes on Trapeze, SHL D 8.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8M Schedule for Bracing Pipes on Trapeze, SHL D 8.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9 Floor Supported Pipes, SHL D 8.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9M Floor Supported Pipes, SHL D 8.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 Schedule for Typical Connections to Structural Supporting Members1 9.2 . . . . . . . . . . . . 9-1M Schedule for Typical Connections to Structural Supporting Members1 9.3 . . . . . . . . . . . .



xiiiSeismic Restraint Manual • Third Edition

FIGURES Page

4-1 Typical Locations of Bracing 4.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Side Bracing for Rectangular Ducts 4.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 Side Bracing for Rectangular Ducts 4.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 Cable Side Bracing for Rectangular Ducts 4.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5 Side Bracing for Rectangular Ducts 4.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6 Center Bracing for Rectangular Ducts 4.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7 Cable Center Bracing for Rectangular Ducts 4.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8 Floor Supported Duct 4.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9 Single Hanger Bracing for Round Ducts 33-36 Inches (838-900 mm) 4.12. . . . . . . . . . . . 4-10 Single Hanger Cable Bracing for Round Ducts 33-36 Inches (838-900 mm) 4.13. . . . . . 4-11 Double Hanger Bracing for Round Ducts Up to 84 Inches (2100 mm) 4.14. . . . . . . . . . . . 4-12 Double Hanger Bracing for Round Ducts Up to 84 Inches (2100 mm) 4.15. . . . . . . . . . . . 4-13 Transverse Bracing for Pipes 4.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14 Strut Bracing for Pipes 4.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15 Alternate Attachment to Hanger for Pipe Bracing 4.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16 Longitudinal Bracing for Pipes 4.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17 Alternate Bracing for Pipes 4.20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18 Cable Bracing for Pipes 4.21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19 Longitudinal Cable Bracing for Pipes 4.22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20 Strut Bracing for Pipe Trapeze 4.23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21 Cable Bracing for Pipe Trapeze 4.24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22 Floor Supported Pipes 4.25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 Connections to Concrete 9.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1B Connections to Concrete 9.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2 Adjustable Connections to Concrete 9.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3 Alternate Hinged Connections to Concrete 9.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4 Alternate Connections to Concrete 9.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5 Alternate Connections to Concrete 9.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6 Connections to Concrete Fill on Steel Deck 9.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7 Connections to Concrete 9.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8 Connections to Steel 9.12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-9 Connections to Open Web Steel Joists 9.13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10 Alternate Connection to Open Web Steel Joists 9.14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-11 Connections to Steel 9.15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12 Connections to Steel 9.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-13 Ducts Hung Below Steel Beams 9.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-14 Acceptable Details-Wire Connections to Structure 9.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-15 Hanger Connection to Wood 9.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16 Connections to Wood I-Joist 9.20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-17 Connections to Wood 9.21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 Cable Connection to Duct Frame 10.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2 Alternate Cable Connection to Duct Frame 10.3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3 Longitudinal Cable Connection to Duct Hanger 10.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4 Alternate Longitudinal Cable Bracing Connection to Duct Hanger 10.5 . . . . . . . . . . . . . . . 10-5 Cable End Connection 10.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6 Pipe Strut Connections 10.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7 Connections for Framing Channel 10.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8 Hanger Rod Connections 10.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9 Hubless Cast Iron Pipe 10.10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10 Riser Bracing for Hubless Pipes 10.11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



xiv Seismic Restraint Manual • Third Edition

10-11 Framing Channel 10.12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12 Connections for Pipes on Trapeze 10.13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13 Alternate Stiffener Connection 10.14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-14 Safety Supports for Ceiliing-Mounted Distribution Device 10.15. . . . . . . . . . . . . . . . . . . . . . 10-15 Seismic Joints In Pipes 10.16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-16 Transverse Brace at Steam Pipes 10.17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-17 Welded Tabs 10.18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-18 Stiffeners And Saddles at Pipe Clamps 10.19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-19 Seismic Bracing of Pipes on Isolators 10.20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



INTRODUCTION

CHAPTER 1



INTRODUCTIONCHAPTER 1

1.1Seismic Restraint Manual • Third Edition

1.1 OVERVIEW

This manual begins with a nontechnical explanation of

seismic loads to help designers and builders appreciate

the need for seismic restraints. Chapter 2 explains the

steps in using the drawings and tables and includes two

worked examples. Chapter 3 outlines the general re-

quirements for restraints. Chapter 4 includes the detail

drawings that illustrate required bracing. Notes on

these details refer to tables in Chapters 5 through 8 for

specific bracing sizes. Chapters 9 and 10 give sizes and

details for connecting the bracing to the structure. Ap-

pendix A instructs designers in the selection of the

Seismic Hazard Level (SHL), Appendix B is a sample

specification, and Appendix C is a list of references.

The manual concludes with a glossary found in Ap-

pendix D and an index.

1.2 WHAT ARE SEISMIC LOADS?

Seismic loads are the horizontal and vertical forces ex-

erted on a structure during an earthquake. Every struc-

ture is designed for vertical, or gravity, loads. In the

case of ducts or pipes, gravity loads include the weight

of the ducts or pipes and their contents, and the direc-

tion of the loading is downward. By contrast, earth-

quake forces can be in any direction. However, the or-

dinary supports designed for gravity loads generally

take care of the vertical loads during an earthquake.

Therefore, the primary emphasis in seismic design is

on lateral, or horizontal forces.

1.3 WHAT HAPPENS DURING ANEARTHQUAKE?

A fault is a fracture in the earth’s crust, and an earth-

quake results from slippage along the fault plane. Any

structure straddling the fault line will probably suffer

damage, no matter how well it has been designed;

however, most effects of earthquakes are not directly

on the fault line. This is because the movement caused

by the slippage creates waves in the earth that travel

away from the fault plane. These waves change

throughout the duration of the earthquake, add to one

another, and result in extremely complicated wave

motions and vibrations. The direction of forces on

structures can be horizontal, vertical, or rotational. In

terms of their effect on a given building, they are not

only unpredictable in direction, but also unpredictable

in strength and duration. The structural load is propor-

tional to the intensity of shaking and to the weight of

the supported elements.

1.4 HOW TO RESIST SEISMIC LOADS

The general principle behind the structural calcula-

tions used to prepare these guidelines is enabling ducts

and piping to resist seismic forces by the strength of

their attachment to the building’s structure. For the

purposes of this manual, the building is assumed to be

designed to perform safely in response to earthquake

motions. To remain intact and functioning, ducts and

pipes need to move with the building during an earth-

quake and not break away from their supports. There-

fore, the restraints are sized to improve the chances of

keeping the ducts and piping attached to the structure.

1.5 KINDS OF BRACING

All ducts and pipes are also assumed to be supported

vertically for their non-seismic (gravity) loads. The

bracing detailed in this manual focuses on the addi-

tional members needed to resist horizontal forces. Be-

cause the directionality of seismic forces is not pre-

dictable, it is important to brace ducts and piping in

several directions. Instead of bracing ducts and pipes

against every possible angle of force, it is enough to

brace them longitudinally (in the direction of their run)

and transversely (perpendicular to their run). Togeth-

er, transverse bracing, longitudinal bracing, and the

vertical supports resist lateral loads from any direc-

tion.

1.6 WHY DIFFERINGREQUIREMENTS?

The choice of bracing and connectors is not always

straightforward. There is a significant difference be-

tween requirements for hospitals in California, for ex-

ample, and those for houses in Ohio. To ensure ade-

quate restraint without expensive over-design, a

design professional must take responsibility for speci-

fying the parameters needed in the following chapter.



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