1、SEISMIC RESTRAINTMANUALGUIDELINES FORMECHANICAL SYSTEMSSHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.www.smacna.orgSEISMIC RESTRAINTMANUALGUIDELINES FORMECHANICAL SYSTEMSTHIRD EDITION MARCH, 2008SHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.4201 Lafaye
2、tte Center DriveChantilly, VA 201511209www.smacna.orgSEISMIC RESTRAINT MANUALGUIDELINES FOR MECHANICAL SYSTEMSCOPYRIGHT C0069 SMACNA 2008All Rights ReservedbySHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.4201 Lafayette Center DriveChantilly, VA 201511209Printed in the U.S.A.F
3、IRST EDITION DECEMBER 1991SECOND EDITION FEBRUARY 1998THIRD EDITION MARCH 2008Except 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, photoc
4、opying, recording, or otherwise, without the prior written permission of the publisher.iiiSeismic Restraint Manual Third EditionFOREWORDHISTORY OF THE GUIDELINESDuring the San Fernando Earthquake of 1971, four of the eleven medical facilities in the area were so badly damagedthat they had to be evac
5、uated. As a result, the State of California began to require that hospitals be built to remainoperational 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 Lo
6、s Angeles pub-lished Guidelines for Seismic Restraint of Mechanical Systems in 1976. This document was preapproved by the Cali-fornia Office of Statewide Health Planning and Development (OSHPD). A later edition, in 1982, copublished by thePlumbing and Piping Industry Council, Inc. (PPIC), expanded t
7、he 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-fornias unusually severe seismic conditions. The result was that, in many parts of the country, seismic restraints werebeing overdes
8、igned at unnecessary expense.To remedy this, SMACNA formed the Seismic Restraint Task Force to study the feasibility of developing nationalstandards. In April 1990, the task force recommended that SMACNA develop and publish this manual of seismic re-straint guidelines. It was to include nontechnical
9、 explanations of seismic forces, and the tables from the old guidelineswould be expanded to include electrical conduit and larger ducts. Then, for about a year, the manual was developedby the task force and consulting engineers, with input from a broad spectrum of users in the sheet metal and plumbi
10、ngindustries.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 ofanticipated force levels. Appendix A is provided to as
11、sist the design professional in the specification/selection of thebracing levels required.PURPOSE OF THE GUIDELINESIn 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 dis
12、covered 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 themechanical systems could mean that a building might be uninhabitable for weeks or months. As a result, seismic con-cerns now includ
13、e 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 thatare not usually thought of as quoteblleftearthquake zones.“ Areas of the South and Midwest, for example, are beginning to takeprecau
14、tions 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 areaslook for guidance in making buildings safer, they naturally turn to C
15、alifornia, with its longer history of designing forearthquakes. However, because California has such severe, frequent earthquakes, its standards may be too strict forother parts of the country.Until now, designers have had little choice but to use Californias strict guidelines or use none at all. Th
16、e purpose ofthis manual is to provide a flexible set of guidelines that accommodates all parts of the country. Within a single format,very lowrisk and very highrisk areas can be easily and equally accommodated. The guidelines will enable designersand contractors to determine the regionallyappropriat
17、e restraints for sheet metal ducts, piping, and conduit, so thatthey are more likely to maintain their integrity and remain attached to the buildings structure during an earthquake.ROLES OF CONSTRUCTION PROFESSIONALSIn order to accommodate a variety of conditions, these guidelines are somewhat more
18、complicated than the originalmanual. 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 Editionsu
19、ltation with local jurisdictions. A sheet metal or mechanical contractor cannot be expected to carry the burden ofthis 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.
20、WHAT IS NOT IN THIS MANUALThis manual is not intended to cover the ordinary supports for ducts and pipes required for gravity loads. (Some havebeen included for reference only.) The only restraints shown in these tables and drawings are those needed to providethe extra support for seismic loads.This
21、 manual also does not cover the seismic restraints for fire sprinklers and equipment. Fire sprinklers have beencovered by the National Fire Protection Association (NFPA) since 1939.SHEET METAL AND AIR CONDITIONING CONTRACTORSNATIONAL ASSOCIATION, INC.v Seismic Restraint Manual Third EditionSEISMIC R
22、ESTRAINT TASK FORCERobert P. Vlick, ChairmanACCO Engineered SystemsTustin, CaliforniaTye HalversonSouthwest Air Conditioning, Inc.Las Vegas, NevadaKailasam SenthilCritchfield Mechanical, Inc.Menlo Park, CaliforniaRobert J. Wasilewski, Staff LiaisonSMACNAChantilly, VirginiaOTHER CONTRIBUTORSJohn A. M
23、artin however, most effects of earthquakes are not directlyon the fault line. This is because the movement causedby the slippage creates waves in the earth that travelaway from the fault plane. These waves changethroughout the duration of the earthquake, add to oneanother, and result in extremely co
24、mplicated wavemotions and vibrations. The direction of forces onstructures can be horizontal, vertical, or rotational. Interms of their effect on a given building, they are notonly unpredictable in direction, but also unpredictablein strength and duration. The structural load is propor-tional to the
25、 intensity of shaking and to the weight ofthe supported elements.1.4 HOW TO RESIST SEISMIC LOADSThe general principle behind the structural calcula-tions used to prepare these guidelines is enabling ductsand piping to resist seismic forces by the strength oftheir attachment to the buildings structur
26、e. For thepurposes of this manual, the building is assumed to bedesigned to perform safely in response to earthquakemotions. To remain intact and functioning, ducts andpipes need to move with the building during an earth-quake and not break away from their supports. There-fore, the restraints are si
27、zed to improve the chances ofkeeping the ducts and piping attached to the structure.1.5 KINDS OF BRACINGAll ducts and pipes are also assumed to be supportedvertically for their non-seismic (gravity) loads. Thebracing detailed in this manual focuses on the addi-tional members needed to resist horizon
28、tal forces. Be-cause the directionality of seismic forces is not pre-dictable, it is important to brace ducts and piping inseveral directions. Instead of bracing ducts and pipesagainst every possible angle of force, it is enough tobrace them longitudinally (in the direction of their run)and transver
29、sely (perpendicular to their run). Togeth-er, transverse bracing, longitudinal bracing, and thevertical supports resist lateral loads from any direc-tion.1.6 WHY DIFFERINGREQUIREMENTS?The choice of bracing and connectors is not alwaysstraightforward. There is a significant difference be-tween requir
30、ements for hospitals in California, for ex-ample, and those for houses in Ohio. To ensure ade-quate restraint without expensive over-design, adesign professional must take responsibility for speci-fying the parameters needed in the following chapter.1.2 Seismic Restraint Manual Third EditionTHIS PAG
31、E INTENTIONALLY LEFT BLANKINSTRUCTIONS FORUSING THE GUIDELINESCHAPTER 2INSTRUCTIONS FOR USING THE GUIDELINESCHAPTER 22.1Seismic Restraint Manual Third Edition2.1 THE SEISMIC HAZARD LEVEL(SHL)The SHL is to be determined by the design professional. Instructions are given in Appendix A.The SHL is deter
32、mined by using the building code tocalculate the lateral acceleration to be resisted. Thismanual provides tables for four levels of accelerationwhich are used to select the restraints. The level selected should be greater than or equal to the acceleration required by the building code.Because this m
33、anual covers several building codes andconditions, it is very important to use the correct SHL.The SHL will tell you which tables to use in lookingup references made in the drawings. Determining theappropriate codes and finding the SHL are the designprofessionals responsibility, not the mechanical c
34、ontractors.Appendix A provides guidelines for the design professional to establish the SHL.2.2 HOW TO READ THE SIZINGTABLESSee Chapter 4 to determine the appropriate details forthe application. Notice that instead of giving sizes forthe bracing members, the notes refer to tables, e.g.,“see Tables 5-
35、2, 6-2, 7-2, or 8-2.” This referencing system allows a variety of SHLs to be covered withoutcluttering up the drawing notes with a lot of sizing information.2.3 USING THE SIZING TABLESFind the appropriate details in Chapter 4. Refer to thetables indicated in the notes. The following tables arecontai
36、ned in the listed chapters:Chapter 5. Tables for Seismic Hazard Level ATable 51. Side Bracing for Rectangular Ducts,L=2 ft 8 in.Table 52. Side Bracing for Rectangular Ductswith Rod HangersTable 53. Center Bracing for RectangularDucts, L=7 ftTable 54. Center Bracing for RectangularDucts, L=10 ftTable
37、 55. Floor Supported DuctsTable 56. Bracing for Round DuctsTable 57. Bracing Pipes and ConduitTable 58. Bracing Pipes on TrapezeTable 59. Floor Supported PipesChapter 6. Tables for Seismic Hazard Level BTable 61. Side Bracing for Rectangular Ducts,L=2 ft 8 in.Table 62. Side Bracing for Rectangular D
38、uctswith Rod HangersTable 63. Center Bracing for RectangularDucts, L=7 ftTable 64. Center Bracing for RectangularDucts, L=10 ftTable 65. Floor Supported DuctsTable 66. Bracing for Round DuctsTable 67. Bracing Pipes and ConduitTable 68. Bracing Pipes on TrapezeTable 69. Floor Supported PipesChapter 7
39、. Tables for Seismic Hazard Level CTable 71. Side Bracing for Rectangular Ducts,L=2 ft 8 in.Table 72. Side Bracing for Rectangular Ductswith Rod HangersTable 73. Center Bracing for RectangularDucts, L=7 ftTable 74. Center Bracing for RectangularDucts, L=10 ftTable 75. Floor Supported DuctsTable 76.
40、Bracing for Round DuctsTable 77. Bracing Pipes and ConduitTable 78. Bracing Pipes on TrapezeTable 79. Floor Supported Pipes2.2 Seismic Restraint Manual Third EditionChapter 8. Tables for Seismic Hazard Level DTable 81. Side Bracing for Rectangular Ducts,L=2 ft 8 in.Table 82. Side Bracing for Rectang
41、ular Ductswith Rod HangersTable 83. Center Bracing for RectangularDucts, L=7 ftTable 84. Center Bracing for RectangularDucts, L=10 ftTable 85. Floor Supported DuctsTable 86. Bracing for Round DuctsTable 87. Bracing Pipes and ConduitTable 88. Bracing Pipes on TrapezeTable 89. Floor Supported PipesPer
42、form the following steps to use the sizing tables:Step 1. Get the SHL from the construction documents,design professional, or building official.Step 2. Check the structural system to know from whatthe pipes or ducts are being hung.Step 3. Find the detail in Chapter 4 that corresponds tothe duct or p
43、iping attachment condition needed. Thenotes on the detail will indicate the table where member sizes and connections can be found.Step 4. Determine which chapter contains the table foryour SHL. For SHL A, use Chapter 5. For SHL B, useChapter 6. For SHL C, use Chapter 7. For SHL D, useChapter 8. Each
44、 chapter contains a complete set ofTables x1 through x9, where “x” is the appropriatechapter number.Step 5. In the chapter corresponding to the requiredSHL, find the table referred to in detail from Chapter4.Step 6. In the first column, find the duct or pipe size.If the exact size is not listed in t
45、he table, the next largersize must be used. Ducts are assumed to be SMACNAstandard construction, and pipes are assumed to beSchedule 40 water pipes. If the installation uses insulation or heavy construction, verify the weight of theduct or pipe and use the weight column in the tables toselect the pr
46、oper braces. Duct bracing must be selectedso that the size and weight are not less than indicatedin the tables. Bracing for pipes and electrical conduitmay be selected by their weight alone. Use the bracingindicated for a pipe weight equal to or greater than theweight of the pipe or conduit used.Ste
47、p 7. Once the appropriate row in the table is found,move to the right to read the sizes of the hangers,braces, and bolts.Step 8. In the same row, under the column labeled“Connection Type to Structural Member,” find theconnection type designated by a capital letter (Athrough I).Step 9. Find the conne
48、ction type in the first column inTable 9-1 in Chapter 9. Move to the right in the samerow to find sizes for expansion anchors, bolts, spreadersizes, and angle connectors for connecting to the supporting structure.Step 10. Find a detail in Chapter 9 that corresponds tothe connection type and to the t
49、ype of supporting structural system. Install transverse and longitudinal seismic braces at the intervals specified in the general requirements for ducts in Chapter 3 or the tables for pipesin Chapters 5, 6, 7, or 8.2.4 EXAMPLE: DUCT BRACINGDetermine the bracing for a 48 in. (1219 mm) squareduct supported so that the top of the duct is 5 ft (1524mm) below a structural concrete slab.Step 1. The construction documents specify SHL A.Step 2. Chapter 4 contains rectangular ducts shown inFigures 4-2 through 4-7.
