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ASCE 7-98

American Society of Civil Engineers

Minimum Design Loadsfor Buildings andOther Structures

Revision of ANSI/ASCE 7-95

This document uses both Système International (SI) units and customary units.

Structural Engineering Institute

Published by the American Society of Civil Engineers1801 Alexander Bell Drive

Reston, Virginia 20191-4400



ABSTRACTASCE standard, Minimum Design Loads for Bui/dings andOther Structures (ASCE 7-98 a revision of ANSI/ASCE 7-95),gives requirements for dead, live, soil, flood, wind, snow, rain,ice, and earthquake loads, and their combinations, that aresuitable for inclusion in building codes and other documents.The major revision of this standard involves the section onwind loads. This section has been greatly expanded to in-clude the latest information in the field of wind load engi-neering. Requirements have been added for flood loads andice loads. An appendix on serviceability requirements hasalso been added. The structural load requirements providedby this standard are intended for use by architects, structuralengineers, and those engaged in preparing and administeringlocal building codes.

Library of Congress Cataloging-in-Publication Data

Minimum design loads for buildings and other structures /American Society of Civil Engineers

p. cm."ASCE 7-98""Revision of ANSI/ASCE 7-95.""Approved October 1999.""Published January 2000."Includes bibliographical references and index.ISBN 0-7844-0445-3

1. Structural engineering—United States. 2. Standards,Engineering—United States. I. American Society ofCivil Engineers.

TH851.M56 1996624.1'72—dc21 94-3854

CIP

Photocopies. Authorization to photocopy material for internalor personal use under circumstances not falling within the fairuse provisions of the Copyright Act is granted by ASCE tolibraries and other users registered with the Copyright Clear-ance Center (CCC) Transactional Reporting Service, pro-vided that the base fee of $8.00 per chapter plus $.50 perpage is paid directly to CCC, 222 Rosewood Drive, Danvers,MA 01923. The identification for ASCE Books is 0-7844-0445-3/00 $8.00 + $.50 per page. Requests for special permissionor bulk copying should be addressed to Permissions & Copy-right Dept., ASCE.

Copyright © 2000 by the American Society of Civil Engineers,All Rights Reserved.Library of Congress Catalog Card No: 94-3854ISBN 0-7844-0445-3Manufactured in the United States of America.

Third printing.



STANDARDS

In April 1980, the Board of Direction approvedASCE Rules for Standards Committees to govern thewriting and maintenance of standards developed bythe Society. All such standards are developed by aconsensus standards process managed by the Man-agement Group F (MGF), Codes and Standards. Theconsensus process includes balloting by the balancedstandards committee made up of Society membersand nonmembers, balloting by the membership ofASCE as a whole, and balloting by the public. Allstandards are updated or reaffirmed by the same pro-cess at intervals not exceeding 5 years.

The following Standards have been issued.

ANSI/ASCE 1-82 N-725 Guideline for Design andAnalysis of Nuclear Safety Related EarthStructures

ANSI/ASCE 2-91 Measurement of Oxygen Transferin Clean Water

ANSI/ASCE 3-91 Standard for the Structural Designof Composite Slabs and ANSI/ASCE 9-91 Stan-dard Practice for the Construction and Inspectionof Composite Slabs

ANSE 4-86 Seismic Analysis of Safety-Related Nu-clear Structures

Building Code Requirements for Masonry Structures(ACI530-99/ASCE5-99/TMS402-99) and Specifi-cations for Masonry Structures (ACI530.1-99/ASCE6-99/TMS602-99)

ANSI/ASCE 7-98 Minimum Design Loads for Build-ings and Other Structures

ANSI/ASCE 8-90 Standard Specification for the De-sign of Cold-Formed Stainless Steel StructuralMembers

ANSI/ASCE 9-91 listed with ASCE 3-91ANSI/ASCE 10-97 Design of Latticed Steel Trans-

mission StructuresANSI/ASCE 11-90 Guideline for Structural Condition

Assessment of Existing BuildingsANSI/ASCE 12-91 Guideline for the Design of Ur-

ban Subsurface DrainageASCE 13-93 Standard Guidelines for Installation of

Urban Subsurface DrainageASCE 14-93 Standard Guidelines for Operation and

Maintenance of Urban Subsurface DrainageANSI/ASCE 15-93 Standard Practice for Direct De-

sign of Buried Precast Concrete Pipe Using Stan-dard Installations (SIDD)

ASCE 16-95 Standard for Load and Resistance Fac-tor Design (LRFD) of Engineered WoodConstruction

ASCE 17-96 Air-Supported StructuresASCE 18-96 Standard Guidelines for In-Process

Oxygen Transfer TestingASCE 19-96 Structural Applications of Steel Cables

for BuildingsASCE 20-96 Standard Guidelines for the Design and

Installation of Pile FoundationsASCE 21-96 Automated People Mover Standards—

Part 1ASCE 21-98 Automated People Mover Standards—

Part 2ASCE 22-97 Independent Project Peer ReviewASCE 23-97 Specification for Structural Steel Beams

with Web OpeningsASCE 24-98 Flood Resistant Design and

ConstructionASCE 25-97 Earthquake-Actuated Automatic Gas

Shut-Off Devices

This document-has been carefully reviewed, edited, and proofread. However, to notify readers of any errata inthe text, ASCE has set up the following web site: www.seinstitute.org/pdf/errata.pdf

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www.seinstitute.org/pdf/errata.pdf


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FOREWORD

The material presented in this publication has on the part of the American Society of Civil Engi-been prepared in accordance with recognized engineers, or of any other person named herein, that thisneering principles. This Standard and Commentary information is suitable for any general or particularshould not be used without first securing competent use or promises freedom from infringement of anyadvice with respect to their suitability for any given patent or patents. Anyone making use of this infor-application. The publication of the material contained mation assumes all liability from such use.herein is not intended as a representation or warranty

v



ACKNOWLEDGEMENTS

The American Society of Civil Engineers(ASCE) acknowledges the work of the Minimum De-sign Loads on Buildings and Other Structures Stan-dards Committee of the Codes and Standards Activi-ties Division of the Structural Engineering Institute.This group comprises individuals from many back-grounds including: consulting engineering, research,construction industry, education, government, designand private practice.

This revision of the standard began in 1995 andincorporates information as described in thecommentary.

This Standard was prepared through the consen-sus standards process by balloting in compliance withprocedures of ASCE's Codes and Standards ActivitiesCommittee. Those individuals who serve on the Stan-dards Committee are:

Kharaiti L. AbrolShirin D. AderDemirtas C. BayarJohn E. BreenDavid G. BrinkerRay A. BucklinJames R. CagleyJack E. CermakKevin C.K. CheungEdward CohenJames S. CohenJay H. CrandellStanley W. CrawleyMajed DabdoubAmitabha DattaCharles A. De AngelisJames M. DelahayBradford K. DouglasJohn F. DuntemannDonald DusenberryBruce R. Ellingwood, Vice-ChairEdward R. EstesDavid A. FanellaTheodore V. GalambosSatyendra K. GhoshLorenzo GonzalezDennis W. Graber -Lawrence G. GriffisDavid S. GromalaRobert D. HansonJames R. Harris, ChairJoseph P. HartmanSteven R. HemlerNicholas IsyumovChristopher P. JonesJohn H. Kapmann, Jr.A. Harry KarabinisD.J. Laurie KennedyJon P. KilandRandy KissellUno Kula

Edward M. LaatschJohn V. LoscheiderIan MackinlayHarry W. MartinRusk MasihGeorge M. MatsumuraRobert R. McCluerRichard McConnellKishor C. MehtaRick MendlenJoseph J. Messersmith, Jr.Joe N. NunneryMichael O'RourkeClifford OliverFrederick J. PalmerAlan B. PeabodyDavid B. PerazaDale C. PerryClarkson W. PinkhamRobert D. PrinceRobert T. RatayMassandra K. RavindraLawrence D. ReaveleyAbraham J. RokachWilliam D. RomeJames A. RossbergJulie A. RuthHerbert S. SaffirPhillip J SamblanetSuresh C. SatsangiAndrew ScanlonWilliam L. ShoemakerEmil SimiuThomas D. SkaggsThomas L. SmithJames G. SoulesTheodore StathopoulosFrank W. Stockwell, Jr.Donald R. StrandEdgar L. Sutton, Jr.Harry B. Thomas

Wayne N. TobiassonBrian E. TrimbleDavid P. TyreeThomas R. TysonJoseph W. VellozziRichard A. VognildFrancis J. Walter, Jr.Marius B. WechslerYi Kwei WenPeter J.G. WillseLyle L. WilsonJoseph A. Wintz, III

Task Committee on GeneralStructural Requirement!!James S. CohenJohn F. DuntemannDonald Dusenberry, ChairJohn L. GrossMark B. HoganAnatol LonginowRobert T. RatayJames G. Soules

Task Committee on StrengthBruce R. Ellingwood, ChairTheodore V. GalambosDavid S. GromalaJames R. HarrisD.J. Laurie KennedyClarkson PinkhamAndrew ScanlonJames G. SoulesMassandra K. RavindraYi Kwei Wen

Task Committee on Live LoadsJames R. CagleyRaymond A. CookRoss B. CorotisCharles A. De Angelis

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William L. ShoemakerJohn G. TawreseyHarry B. ThomasThomas R. TysonYi Kwei Wen, Chair

Task Committee on Flood LoadsChristopher P. Jones, Chair

Task Committee on Wind LoadsHoward S. BurtonJames M. DelahayBradford K. DouglasLawrence G. Griffis, ChairGilliam S. HarrisPeter A. IrwinAhsan KareemJames R. McDonaldJoseph J. Messersmith, Jr.Dale C. PerryJon A. PeterkaTimothy A. ReinholdDon R. ScottThomas L. SmithEric StaffordTheodore StathopoulosPeter J. VickeryRichard A. Vognild

Task Committee on Snow andRain LoadsShirin AderCharles De AngelisBrad DouglasDave HattisNicholas IsyumovJ. Randolph KissellIan MackinlayHarry W. MartinJoe N. NunneryMichael O'Rourke, ChairSuresh C. SatsangiW. Lee ShoemakerEd SuttonWayne N. TobiassonPeter Willse

Task Committee onEarthquake LoadsShirin D. AderJulie BircherSatyendra K. GhoshRonald O. HamburgerRobert D. HansonMark B. HoganJon P. KilandHarry W. Martin

Lawrence D. Reaveley, ChairJohn G. TawreseyDiana R. Todd

Task Committee onAtmospheric IcingDavid G. BrinkerPeter G. CatchpoleClayton L. ClemJohn EricsenKaren FinstadDonald G. HealdKathy Jones, ChairSettiana G. KishnasamySteve LaCasseNeal LottDonald G. MarshallNate MulherinAlan B. PeabodyJoe PohlmanChuck RyersonTapani SeppaLonggang ShanRonald M. ThorkildsonH. B. White

Vlll



CONTENTS

PageSTANDARDS iiiFOREWORD vACKNOWLEDGMENTS vii

Standard1.0 General 1

1.1 Scope .- 11.2 Definitions 11.3 Basic Requirements 1

1.3.1 Strength 11.3.2 Serviceability 21.3.3 Self-Straining Forces 21.3.4 Analysis 21.3.5 Counteracting Structural Actions 2

1.4 General Structural Integrity „... 21.5 Classification of Buildings and Other Structures 21.6 Additions and Alterations to Existing Structures 21.7 Load Tests 3

2.0 Combinations of Loads 52.1 General 52.2 Symbols and Notation 52.3 Combining Factored Loads Using Strength Design 5

2.3.1 Applicability 52.3.2 Basic Combinations 52.3.3 Load Combinations Including Flood Load 5

2.4 Combining Nominal Loads Using Allowable Stress Design 52.4.1 Basic Combinations 52.4.2 Load Combinations Including Flood Load 62.4.3 Load Reduction 6

2.5 Load Combinations for Extraordinary Events 6

3.0 Dead Loads 73.1 Definition 73.2 Weights of Materials and Constructions 73.3 Weight of Fixed Service Equipment 7

4.0 Live Loads 84.1 Definition 84.2 Uniformly Distributed Loads 8

4.2.1 Required Live Loads 84.2.2 Provision for Partitions 8

4.3 Concentrated Loads 84.4 Loads on Handrails, Guardrail Systems, Grab Bar Systems, Vehicle Barrier Systems,

and Fixed Ladders 84.4.1 Definitions 84.4.2 Loads 8

4.5 Loads Not Specified 94.6 Partial Loading 94.7 Impact Loads 9

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4.7.1 Elevators 94.7.2 Machinery 9

4.8 Reduction in Live Loads 94.8.1 General 94.8.2 Heavy Live Loads 104.8.3 Passenger Car Garages 104.8.4 Special Occupancies 104.8.5 Special Structural Elements 10

4.9 Minimum Roof Live Loads 104.9.1 Flat, Pitched, and Curved Roofs '. 104.9.2 Special-Purpose Roofs 10

4.10 Crane Loads 104.10.1 Maximum Wheel Load 114.10.2 Vertical Impact Force 114.10.3 Lateral Force 114.10.4 Longitudinal Force 11

4.11 References 11

5.0 Soil and Hydrostatic Pressure and Flood Loss 155.1 Pressure on Basement Walls 155.2 Uplift on Floors and Foundations 155.3 Flood Loads 15

5.3.1 Definitions 155.3.2 Design Requirements 16

5.3.2.1 Design Loads 165.3.2.2 Breakaway Walls 16

5.3.3 Loads during Flooding 165.3.3.1 Load Basis 165.3.3.2 Hydrostatic Loads 165.3.3.3 Hydrodynamic Loads 165.3.3.4 Wave Loads 16

5.3.3.4.1 Breaking Wave Loads on Vertical Pilings and Columns 175.3.3.4.2 Breaking Wave Loads on Vertical Walls 175.3.3.4.3 Breaking Wave Loads on Non-Vertical Walls 185.3.3.4.4 Breaking Wave Loads from Obliquely Incident Waves 18

5.3.3.5 Impact Loads 185.3.4 Special Flood Hazard Areas—A Zones 18

5.3.4.1 Elevation 18' 5.3.4.2 Anchorage 18

5.3.4.3 Non-Residential Flood-Resistant Construction 195.3.4.4 Enclosures below Design Flood Elevation 195.3.4.5 Scour 19

5.3.5 Coastal High Hazard Areas—V Zones 195.3.5.1 Elevation 195.3.5.2 Space below Design Flood Elevation 195.3.5.3 Erosion and Scour 19

6.0 Wind Loads 236.1 General 23

6.1.1 Scope 236.1.2 Allowed Procedures 236.1.3 Wind Pressures Acting on Opposite Faces of Each Building Surface 23

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6.1.4 Minimum Design Wind Loading 236.1.4.1 Main Wind Force Resisting System 236.1.4.2 Components and Cladding 23

6.2 Definitions 236.3 Symbols and Notations 256.4 Method 1—Simplified Procedure 26

6.4.1 Scope 266.4.2 Design Procedure 266.4.3 Air Permeable Cladding 26

6.5 Method 2—Analytical Procedure ~ 276.5.1 Scope 276.5.2 Limitations 27

6.5.2.1 Shielding 276.5.2.2 Air Permeable Cladding 27

6.5.3 Design Procedure 276.5.4 Basic Wind Speed 27

6.5.4.1 Special Wind Regions 276.5.4.2 Estimation of Basic Wind Speeds from Regional Climatic Data 276.5.4.3 Limitation 286.5.4.4 Wind Directionality Factor 28

6.5.5 Importance Factor 286.5.6 Exposure Categories 28

6.5.6.1 General 286.5.6.2 Exposure Category for Main Wind-Force Resisting Systems 28

6.5.6.2.1 Buildings and Other Structures 286.5.6.2.2 Low-Rise Buildings 28

6.5.6.3 Exposure Category for Components and Cladding 286.5.6.3.1 Buildings with Mean Roof Height h Less Than or Equal

to 60 ft (18 m) 286.5.6.3.2 Buildings with Mean Roof Height /?, Greater Than 60 ft

(18 m) and Other Structures 286.5.6.4 Velocity Pressure Exposure Coefficient 29

6.5.7 Topographic Effects 296.5.7.1 Wind Speed-Up over Hills, Ridges, and Escarpments 296.5.7.2 Topographic Factor 29

6.5.8 Gust Effect Factor 296.5.8.1 Rigid Structures 296.5.8.2 Flexible or Dynamically Sensitive Structures 296.5.8.3 Rational Analysis 306.5.8.4 Limitations 30

6.5.9 Enclosure Classifications 306.5.9.1 General 306.5.9.2 Openings 306.5.9.3 Wind Borne Debris 306.5.9.4 Multiple Classifications 30

6.5.10 Velocity Pressure 306.5.11 Pressure and Force Coefficients 30

6.5.11.1 Internal Pressure Coefficients 306.5.11.1.1 Reduction Factor for Large Volume Buildings, R, 30

6.5.11.2 External Pressure Coefficients 316.5.11.2.1 Main Wind Force Resisting Systems 316.5.11.2.2 Components and Cladding 31

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6.5.11.3 Force Coefficients 316.5.11.4 Roof Overhangs 31

6.5.11.4.1 Main Wind-Force Resisting System 316.5.11.4.2 Components and Cladding 31

6.5.12 Design Wind Loads on Enclosed and Partially Enclosed Buildings 316.5.12.1 General 31

6.5.12.1.1 Sign Convention 316.5.12.1.2 Critical Load Condition 316.5.12.1.3 Tributary Areas Greater Than 700 ft2 (65 m2) 31

6.5.12.2 Main Wind Force Resisting Systems 316.5.12.2.1 Rigid Buildings of All Heights 316.5.12.2.2 Low-Rise Buildings 326.5.12.2.3 Flexible Buildings 32

6.5.12.3 Full and Partial Loading 326.5.12.4 Components and Cladding 32

6.5.12.4.1 Low-Rise Buildings and Buildings with ft < 60 ft(18.3 m) 32

6.5.12.4.2 Buildings with h > 60 ft (18.3 m) 326.5.12.4.3 Alternative Design Wind Pressures for Components and

Cladding in Buildings with 60 ft (18.3 m) < ft < 90 ft(27.4m) 32

6.5.13 Design Wind Loads on Open Buildings and Other Structures 336.6 Method 3—Wind Tunnel Procedure 33

6.6.1 Scope 336.6.2 Test Conditions 336.6.3 Dynamic Response 336.6.4 Limitations 33

6.6.4.1 Limitations on Wind Speeds 33

7.0 Snow Loads 697.1 Symbols and Notation 697.2 Ground Snow Loads, ps 697.3 Flat-Roof Snow Loads, pf 69

7.3.1 Exposure Factor, Ce 697.3.2 Thermal Factor, C, 697.3.3 Importance Factor, / 697.3.4 Minimum Values of pffor Low-Slope Roofs 69

7.4 Sloped-Roof Snow Loads, ps 697.4.1 Warm-Roof Slope Factor, Cs 707.4.2 Cold Roof Slope Factor, Cs 707.4.3 Roof Slope Factor for Curved Roofs 707.4.4 Roof Slope Factor for Multiple Folded Plate, Sawtooth, and Barrel Vault Roofs.... 707.4.5 Ice Dams and Icicles along Eaves 70

7.5 Partial Loading 707.5.1 Continuous Beam Systems 707.5.2 Other Structural Systems 71

7.6 Unbalanced Roof Snow Loads 717.6.1 Unbalanced Snow Loads for Hip and Gable Roofs 717.6.2 Unbalanced Snow Loads for Curved Roofs 717.6.3 Unbalanced Snow Loads for Multiple Folded Plate, Sawtooth, and Barrel

Vault Roofs 717.6.4 Unbalanced Snow Loads for Dome Roofs 71

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7.7 Drifts on Lower Roofs (Aerodynamic Shade) 717.7.1 Lower Roof of a Structure 717.7.2 Adjacent Structures and Terrain Features 72

7.8 Roof Projections 727.9 Sliding Snow 727.10 Rain-on-Snow Surcharge Load 727.11 Ponding Instability 727.12 Existing Roofs 72

8.0 Rain Loads ." 848.1 Symbols and Notation 848.2 Roof Drainage 848.3 Design Rain Loads 848.4 Ponding Instability 848.5 Controlled Drainage 84

9.0 Earthquake Loads 859.1 General Provisions : 85

9.1.1 Purpose 859.1.2 Scope and Application ; 85

9.1.2.1 Scope 859.1.2.2 Additions to Existing Structures 85

9.1.2.2.1 (no heading) 859.1.2.2.2 (no heading) 85

9.1.2.3 Change of Use 859.1.2.4 Application of Provisions 86

9.1.2.4.1 New Buildings 869.1.2.5 Alternate Materials and Methods of Construction 86

9.1.3 Seismic Use Groups 869.1.3.1 (no heading) 86

9.1.3.1.1 (no heading) 869.1.3.1.2 (no heading) 86

9.1.3.2 (no heading) 869.1.3.3 (no heading) 869.1.3.4 Multiple Use 86

9.1.4 Occupancy Importance Factor 869.2.1 Definitions 869.2.2 Symbols 92

9.3 This Section Left Intentionally Blank 989.4.1 Procedures for Determining Maximum Considered Earthquake and

Design Earthquake Ground Motion Accelerations and Response Spectra 989.4.1.1 Maximum Considered Earthquake Ground Motions 989.4.1.2 General Procedure for Determining Maximum Considered Earthquake

and Design Spectral Response Accelerations 989.4.1.2.1 Site Class Definitions 999.4.1.2.2 Steps for Classifying a Site 999.4.1.2.3 Definitions of Site Class Parameters 1189.4.1.2.4 Site Coefficients and Adjusted Maximum Considered

Earthquake Spectral Response Acceleration Parameters 1199.4.1.2.5 Design Spectral Response Acceleration Parameters 1199.4.1.2.6 General Procedure Response Spectrum 120

9.4.1.3 Site-Specific Procedure for Determining Ground Motion Accelerations... 121

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9.4.1.3.1 Probabilisti c Maximu m Considere d Earthquak e 1219.4.1.3.2 Deterministi c Limi t on Maximu m Considere d Earthquak e

Groun d Motio n 1219.4.1.3.3 Deterministi c Maximu m Considere d Earthquak e

Groun d Motio n 1219.4.1.3.4 Site-Specifi c Design Groun d Motio n 121

9.4.2 Seismic Design Categor y 1219.4.2.1 Determinatio n of Seismic Design Categor y 1219.4.2.2 Site Limitatio n for Seismic Design Categorie s E and F 122

9.4.3 Qualit y Assurance 1229.5 Structura l Design Criteria , Analysis & Procedure s 122

9.5.1 Thi s Section Has Been Intentionall y Left Blank 1229.5.2 Structura l Design Requirement s 122

9.5.2.1 Design Basis 1229.5.2.2 Basic Seismic-Force-Resistin g Systems 123

9.5.2.2.1 Dua l System 1239.5.2.2.2 Combination s of Framin g Systems 123

9.5.2.2.2. 1 R and Ω o Factor s ....... ' 1239.5.2.2.2.2 Combinatio n Framin g Detailin g

Requirement s 1239.5.2.2.3 Seismic Design Categorie s A, B and C 1239.5.2.2.4 Seismic Design Categorie s D and E 123

9.5.2.2.4. 1 Increase d Buildin g Heigh t Limi t 1239.5.2.2.4.2 Interactio n Effects 1239.5.2.2.4.3 Deformationa l Compatibilit y 1279.5.2.2.4.4 Special Momen t Frame s 128

9.5.2.2.5 Seismic Design Categor y F 1289.5.2.3 Structur e Configuratio n 128

9.5.2.3.1 Diaphrag m Flexibilit y 1289.5.2.3.2 Plan Irregularit y 1289.5.2.3.3 Vertical Irregularit y 128

9.5.2.4 Redundanc y 1289.5.2.4.1 Seismic Design Categorie s A, B, and C 1289.5.2.4.2 Seismic Design Categor y D 1289.5.2.4.3 Seismic Design Categorie s E and F 129

9.5.2.5 Analysis Procedure s 1309.5.2.5.1 Seismic Design Categor y A 1309.5.2.5.2 Seismic Design Categorie s B and C 1309.5.2.5.3 Seismic Design Categorie s D, E, and F 1319.5.2.5.4 Diaphragm s 131

9.5.2.6 Design , Detailin g Requirements , and Structura l Componen tLoad Effects 1319.5.2.6.1 Seismic Design Categor y A 132

9.5.2.6.1. 1 Componen t Load Effects 1329.5.2.6.1.2 Load Pat h Connection s 1329.5.2.6.1.3 Anchorag e of Concret e or Masonr y Walls 132

9.5.2.6.2 Seismic Design Categor y B 1329.5.2.6.2.1 Componen t Load Effects 1329.5.2.6.2.2 Opening s 1329.5.2.6.2.3 Directio n of Seismic Load 1329.5.2.6.2.4 Discontinuitie s in Vertical System 1329.5.2.6.2.5 Nonredundan t Systems 132

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9.5.2.6.2.6 Collector Elements 1339.5.2.6.2.7 Diaphragms 1339.5.2.6.2.8 Bearing Walls 1339.5.2.6.2.9 Inverted Pendulum-Type Structures 1339.5.2.6.2.10 Anchorage of Nonstructural Systems 1339.5.2.6.2.11 Columns Supporting Discontinuous Walls

or Frames 1339.5.2.6.3 Seismic Design Category C 133

9.5.2.6.3.1 Direction of Seismic Load 1339.5.2.6.3.2 Collector Elements , 1339.5.2.6.3.3 Anchorage of Concrete or Masonry Walls 133

9.5.2.6.4 Seismic Design Category D 1349.5.2.6.4.1 Direction of Seismic Load 1349.5.2.6.4.2 Collector Elements 1349.5.2.6.4.3 Plan or Vertical Irregularities 1349.5.2.6.4.4 Vertical Seismic Forces 134

9.5.2.6.5 Seismic Design Categories E and F 1349.5.2.6.5.1 Plan or Vertical Irregularities 134

9.5.2.7 Combination of Load Effects 1349.5.2.8 Deflection and Drift Limits 135

9.5.3 Equivalent Lateral Force Procedure 1359.5.3.1 General 1359.5.3.2 Seismic Base Shear 136

9.5.3.2.1 Calculation of Seismic Response Coefficient 1369.5.3.3 Period Determination 1369.5.3.4 Vertical Distribution of Seismic Forces 1379.5.3.5 Horizontal Shear Distribution and Torsion 137

9.5.3.5.1 Direct Shear 1379.5.3.5.2 Torsion 138

9.5.3.6 Overturning 1389.5.3.7 Drift Determination and F-Delta Effects 138

9.5.3.7.1 Story Drift Determination 1389.5.3.7.2 P-Delta Effects 139

9.5.3.8 Simplified Analysis Procedure for Seismic Design of Buildings 1399.5.3.8.1 Seismic Base Shear 1399.5.3.8.2 Vertical Distribution 140

9.5.4 Modal Analysis Procedure 1409.5.4.1 General 1409.5.4.2 Modeling 1409.5.4.3 Modes 1409.5.4.4 Periods 1409.5.4.5 Modal Base Shear 1409.5.4.6 Modal Forces, Deflections, and Drifts 1419.5.4.7 Modal Story Shears and Moments 1419.5.4.8 Design Values 1419.5.4.9 Horizontal Shear Distribution 1429.5.4.10 Foundation Overturning 1429.5.4.11 P-Delta Effects 142

9.5.5 Soil Structure Interaction 1429.5.5.1 General 1429.5.5.2 Equivalent Lateral Force Procedure 142

9.5.5.2.1 Base Shear 142

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9.5.5.2.1.1 Effective Building Period 1429.5.5.2.1.2 Effective Damping 143

9.5.5.2.2 Vertical Distribution of Seismic Forces 1459.5.5.2.3 Other Effects 145

9.5.5.3 Modal Analysis Procedure 1459.5.5.3.1 Modal Base Shears 1459.5.5.3.2 Other Modal Effects 1459.5.5.3.3 Design Values 146

9.6 Architectural, Mechanical, and Electrical Components and Systems 1469.6.1 General : 146

9.6.1.1 Reference Standards 1479.6.1.1.1 Consensus Standards 1479.6.1.1.2 Accepted Standards 147

9.6.1.2 Component Force Transfer 1489.6.1.3 Seismic Forces 1489.6.1.4 Seismic Relative Displacements 1489.6.1.5 Component Importance Factor 1499.6.1.6 Component Anchorage r 149

9.6.1.6.1 (no heading) 1499.6.1.6.2 (no heading) 1499.6.1.6.3 (no heading) 1499.6.1.6.4 (no heading) 1499.6.1.6.5 (no heading) 1499.6.1.6.6 (no heading) 149

9.6.1.7 Construction Documents 1499.6.2 Architectural Component Design 149

9.6.2.1 General 1499.6.2.2 Architectural Component Forces and Displacements 1499.6.2.3 Architectural Component Deformation 1509.6.2.4 Exterior Nonstructural Wall Elements and Connections 1509.6.2.5 Out-of-Plane Bending 1529.6.2.6 Suspended Ceilings 152

9.6.2.6.1 Seismic Forces 1529.6.2.6.2 Industry Standard Construction 152

9.6.2.6.2.1 Seismic Design Category C 1529.6.2.6.2.2 Seismic Design Categories, D, E, and F 152

9.6.2.6.3 Integral Ceiling/Sprinkler Construction 1539.6.2.7 Access Floors 153

9.6.2.7.1 General 1539.6.2.7.2 Special Access Floors 153

9.6.2.8 Partitions 1539.6.2.9 Steel Storage Racks 153

9.6.3 Mechanical and Electrical Component Design 1539.6.3.1 General 1539.6.3.2 Mechanical and Electrical Component Forces and Displacements 1539.6.3.3 Mechanical and Electrical Component Period 1549.6.3.4 Mechanical and Electrical Component Attachments 1559.6.3.5 Component Supports 1559.6.3.6 Component Certification 1559.6.3.7 Utility and Service Lines at Structure Interfaces 1559.6.3.8 Site-Specific Considerations 1559.6.3.9 Storage Tanks Mounted in Structures 155

xvi



9.6.3.10 HVAC Ductwork 1559.6.3.11 Piping Systems 156

9.6.3.11.1 Pressure Piping Systems 1569.6.3.11.2 Fire Protection Sprinkler Systems 1569.6.3.11.3 Other Piping Systems 1569.6.3.11.4 Supports and Attachments for Other Piping 156

9.6.3.12 Boilers and Pressure Vessels 1579.6.3.12.1 ASME Boilers and Pressure Vessels 1579.6.3.12.2 Other Boilers and Pressure Vessels 1579.6.3.12.3 Supports and Attachments for Other Boilers and

Pressure Vessels 1579.6.3.13 Mechanical Equipment, Attachments and Supports 157

9.6.3.13.1 Mechanical Equipment 1589.6.3.13.2 Attachments and Supports for Mechanical Equipment 158

9.6.3.14 Electrical Equipment, Attachments and Supports 1589.6.3.14.1 Electrical Equipment 1589.6.3.14.2 Attachments and Supports for Electrical Equipment 159

9.6.3.15 Alternate Seismic Qualification Methods ,.-...- 1599.6.3.16 Elevator Design Requirements 159

9.6.3.16.1 Reference Document 1599.6.3.16.2 Elevators and Hoistway Structural System 1599.6.3.16.3 Elevator Machinery and Controller Supports

and Attachments 1609.6.3.16.4 Seismic Controls 1609.6.3.16.5 Retainer Plates 160

9.7 Foundation Design Requirements 1609.7.1 General 1609.7.2 Seismic Design Category A 1609.7.3 Seismic Design Category B 160

9.7.3.1 Structural Components 1609.7.3.2 Soil Capacities 160

9.7.4 Seismic Design Category C 1609.7.4.1 Investigation 1609.7.4.2 Pole-Type Structures 1619.7.4.3 Foundation Ties 1619.7.4.4 Special Pile Requirements 161

9.7.5 Foundation Requirements for Seismic Design Categories D, E, and F 1619.7.5.1 Investigation 1619.7.5.2 Foundation Ties 1619.7.5.3 Liquefaction Potential and Soil Strength Loss 1619.7.5.4 Special Pile Requirements 161

9.8 Steel 1619.8.1 Reference Documents 161

9.9 Structural Concrete 1629.9.1 Reference Documents 162

9.10 Reserved for Composite Structures 1629.11 Masonry 162

9.11.1 Reference Documents 1629.12 Wood 162

9.12.1 Reference Documents 1629.13 Provisions for Seismically Isolated Structures 163

9.13.1 General 163

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9.13.2 Criteria Selection 1639.13.2.1 Basis for Design 1639.13.2.2 Stability of the Isolation System 1639.13.2.3 Seismic Use Group 1639.13.2.4 Configuration Requirements 1639.13.2.5 Selection of Lateral Response Procedure 163

9.13.2.5.1 General 1639.13.2.5.2 Equivalent-Lateral-Force Procedure 1639.13.2.5.3 Dynamic Analysis 163

9.13.2.5.3.1 Response-Spectrum Analysis 1639.13.2.5.3.2 Time-History Analysis 1639.13.2.5.3.3 Site-Specific Design Spectra 164

9.13.3 Equivalent-Lateral Force Procedure 1649.13.3.1 General 1649.13.3.2 Deformation Characteristics of the Isolation System 1649.13.3.3 Minimum Lateral Displacements 164

9.13.3.3.1 Design Displacement 1649.13.3.3.2 Effective Period at Design Displacement 1649.13.3.3.3 Maximum Lateral Displacement 1659.13.3.3.4 Effective Period at Maximum Displacement 1659.13.3.3.5 Total Lateral Displacement 165

9.13.3.4 Minimum Lateral Forces 1669.13.3.4.1 Isolation System and Structural Elements at or below

the Isolation System 1669.13.3.4.2 Structural Elements above the Isolation System 1669.13.3.4.3 Limits on Vs 166

9.13.3.5 Vertical Distribution of Force 1669.13.3.6 Drift Limits 167

9.13.4 Dynamic Lateral Response Procedure 1679.13.4.1 General 1679.13.4.2 Isolation System and Structural Elements below the

Isolation System 1679.13.4.3 Structural Elements above the Isolation System 1679.13.4.4 Ground Motion 167

9.13.4.4.1 Design Spectra 1679.13.4.4.2 Time Histories 168

9.13.4.5 Mathematical Model 1689.13.4.5.1 General 1689.13.4.5.2 Isolation System 168

: 9.13.4.5.3 Isolated Building 1689.13.4.5.3.1 Displacement 1689.13.4.5.3.2 Forces and Displacements in Key Elements 168

9.13.4.6 Description of Analysis Procedures 1689.13.4.6.1 General 1689.13.4.6.2 Input Earthquake 1689.13.4.6.3 Response-Spectrum Analysis 1699.13.4.6.4 Time-History Analysis 169

9.13.4.7 Design Lateral Force 1699.13.4.7.1 Isolation System and Structural Elements at or below

the Isolation System 1699.13.4.7.2 Structural Elements above the Isolation System 1699.13.4.7.3 Scaling of Results 169

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9.13.4.7.4 Drift Limits 1699.13.5 Lateral Load on Elements of Structures and Nonstructural Components

Supported by Buildings 1699.13.5.1 General 1699.13.5.2 Forces and Displacements 170

9.13.5.2.1 Components at or above the Isolation Interface 1709.13.5.2.2 Components Crossing the Isolation Interface 1709.13.5.2.3 Components below the Isolation Interface 170

9.13.6 Detailed System Requirements 1709.13.6.1 General : 1709.13.6.2 Isolation System 170

9.13.6.2.1 Environmental Conditions 1709.13.6.2.2 Wind Forces 1709.13.6.2.3 Fire Resistance 1709.13.6.2.4 Lateral-Restoring Force 1709.13.6.2.5 Displacement Restraint 1709.13.6.2.6 Vertical-Load Stability 1719.13.6.2.7 Overturning :.'... 1719.13.6.2.8 Inspection and Replacement 1719.13.6.2.9 Quality Control 171

9.13.6.3 Structural System 1719.13.6.3.1 Horizontal Distribution of Force 1719.13.6.3.2 Building Separations 1719.13.6.3.3 Nonbuilding Structures 171

9.13.7 Foundations 1719.13.8 Design and Construction Review 171

9.13.8.1 General 1719.13.8.2 Isolation System 171

9.13.9 Required Tests of the Isolation System 1729.13.9.1 General 1729.13.9.2 Prototype Tests 172

9.13.9.2.1 General 1729.13.9.2.2 Record 1729.13.9.2.3 Sequence and Cycles 1729.13.9.2.4 Units Dependent on Loading Rates 1729.13.9.2.5 Units Dependent on Bilateral Load 1729.13.9.2.6 Maximum and Minimum Vertical Load 1739.13.9.2.7 Sacrificial-Wind-Restraint Systems 1739.13.9.2.8 Testing Similar Units 173

9.13.9.3 Determination of Force-Deflection Characteristics 1739.13.9.4 System Adequacy 1739.13.9.5 Design Properties of the Isolation System 173

9.13.9.5.1 Maximum and Minimum Effective Stiffness 1739.13.9.5.2 Effective Damping 174

9.14 Nonbuilding Structures 1749.14.1 General 174

9.14.1.1 (no heading) 1749.14.1.2 (no heading) 1749.14.1.3 (no heading) 1759.14.1.4 (no heading) 1759.14.1.5 (no heading) 1759.14.1.6 (no heading) 175

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9.14.1.7 (no heading) 1759.14.1.8 Reference Standard 175

9.14.2 Nonbuilding Structures Similar to Buildings 1759.14.2.1.2 (no heading) 175

9.14.2.2 Rigid Nonbuilding Structures 1759.14.2.3 Deflection Limits and Structure Separation 1769.14.2.1 Design Basis 176

9.14.3 Nonbuilding Structures Similar to Buildings 1769.14.3.1 (no heading) 1769.14.3.2 Pipe Racks '. 178

9.14.3.2.1 Design Basis 1789.14.3.3 Steel Storage Racks 178

9.14.3.3.1 General Requirements 1789.14.3.3.2 Operating Weight 1799.14.3.3.3 Vertical Distribution of Seismic Forces 1799.14.3.3.4 Seismic Displacements 179

9.14.3.4 Electrical Power Generating Facilities 1799.14.3.4.1 General :.... 1799.14.3.4.2 Design Basis 179

9.14.3.5 Structural Towers for Tanks and Vessels 1799.14.3.5.1 General 179

9.14.3.6 Piers and Wharves 1799.14.3.6.1 General 1799.14.3.6.2 Design Basis 179

9.14.4 Nonbuilding Structures Not Similar to Buildings 1809.14.4.1 General 1809.14.4.2 Earth Retaining Structures 180

9.14.4.2.1 General 1809.14.4.3 Tanks and Vessels 180

9.14.4.3.1 General 1809.14.4.3.2 Design Basis 1809.14.4.3.3 Additional Requirements 180

9.14.4.4 Electrical Transmission, Substation, and Distribution Structures 1809.14.4.4.1 General 1809.14.4.4.2 Design Basis 180

9.14.4.5 Telecommunication Towers 1809.14.4.5.1 General 1809.14.4.5.2 Design Basis 180

9.14.4.6 Stacks and Chimneys 180: 9.14.4.6.1 General 180

9.14.4.6.2 Design Basis 1809.14.4.7 Amusement Structures 181

9.14.4.7.1 General 1819.14.4.7.2 Design Basis 181

9.14.4.8 Special Hydraulic Structures 1819.14.4.8.1 General 1819.14.4.8.2 Design Basis 181

9.14.4.9 Buried Structures 1819.14.4.9.1 General 1819.14.4.9.2 Design Basis 181

9.14.4.10 Inverted Pendulums 181

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10.0 Ice Loads—Atmospheric Icing 18210.1 Definitions 18210.2 General 18210.3 Design for Ice Loads 182

10.3.1 Weight of Ice 18210.3.2 Wind on Ice Covered Structures 18210.3.3 Partial Loading 182

Appendix AA.9.0 Supplemental Provisions '. 184A.9.1 Purpose 184A.9.3 Quality Assurance 184A.9.7 Supplementary Foundation Requirements 188A.9.8 Supplementary Provisions for Steel 190A.9.9 Supplementary Provisions for Concrete 192A.9.11 Supplementary Provisions for Masonry 205A.9.12 Supplementary Provisions for Wood 206

Appendix BB .0 Serviceability Considerations 208B.I Deflection, Vibration and Drift 208B.2 Design for Long-Term Deflections 208B.3 Camber 208B.4 Expansion and Contraction 208B.5 Durability 208

Commentary 209

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Minimum Design Loads for Buildings andOther Structures1.0 GENERAL

1.1 SCOPE

This standard provides minimum load require-ments for the design of buildings and other structuresthat are subject to building code requirements. Loadsand appropriate load combinations, which have beendeveloped to be used together, are set forth forstrength design and allowable stress design. For de-sign strengths and allowable stress limits, designspecifications for conventional structural materialsused in buildings and modifications contained in thisstandard shall be followed.

1.2 DEFINITIONS

The following definitions apply to the provisionsof the entire standard.

Allowable stress design: A method of propor-tioning structural members such that elastically com-puted stresses produced in the members by nominalloads do not exceed specified allowable stresses (alsocalled working stress design).

Authority having jurisdiction: The organiza-tion, political subdivision, office or individualcharged with the responsibility of administering andenforcing the provisions of this standard.

Buildings: Structures, usually enclosed by wallsand a roof, constructed to provide support or shelterfor an intended occupancy.

Design strength: The product of the nominalstrength and a resistance factor.

Essential facilities: Buildings and other struc-tures that are intended to remain operational in theevent of extreme environmental loading from wind,snow or earthquakes.

Factored load: The product of the nominal loadand a load factor.

Limit state: A condition beyond which a struc-ture or member becomes unfit for service and isjudged either to be no longer useful for its intendedfunction (serviceability limit state) or to be unsafe(strength limit state).

Load effects: Forces and deformations producedin structural members by the applied loads.

Load factor: A factor that accounts for devia-tions of the actual load from the nominal load, for

uncertainties in the analysis that transforms the loadinto a load effect, and for the probability that morethan one extreme load will occur simultaneously.

Loads: Forces or other actions that result fromthe weight of all building materials, occupants andtheir possessions, environmental effects, differentialmovement, and restrained dimensional changes. Per-manent loads are those loads in which variations overtime are rare or of small magnitude. All other loadsare variable loads. (See also nominal loads.)

Nominal loads: The magnitudes of the loadsspecified in Sections 3 through 9 (dead, live, soil,wind, snow, rain, flood and earthquake) of thisstandard.

Nominal strength: The capacity of a structure ormember to resist the effects of loads, as determinedby computations using specified material strengthsand dimensions and formulas derived from acceptedprinciples of structural mechanics or by field tests orlaboratory tests of scaled models, allowing for mod-eling effects and differences between laboratory andfield conditions.

Occupancy: The purpose for which a buildingor other structure, or part thereof, is used or intendedto be used.

Other structures: Structures, other than build-ings, for which loads are specified in this standard.

P-delta effect: The second order effect on shearsand moments of frame members induced by axialloads on a laterally displaced building frame.

Resistance factor: A factor that accounts for de-viations of the actual strength from the nominalstrength and the manner and consequences of failure(also called strength reduction factor).

Strength design: A method of proportioningstructural members such that the computed forcesproduced in the members by the factored loads donot exceed the member design strength (also calledload and resistance factor design).

Temporary facilities: Buildings or other struc-tures that are to be in service for a limited time andhave a limited exposure period for environmentalloadings.

1.3 BASIC REQUIREMENTS

1.3.1 StrengthBuildings and other structures, and all parts

thereof, shall be designed and constructed to support

1

