2012 IBC
®SEAOC STRUCTURAL/SEISMIC DESIGN MANUAL
Volume 1
ii 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1
Copyright
Copyright © 2013 Structural Engineers Association of California. All rights reserved. This publication or any part thereof must not be reproduced in any form without the written permission of the Structural Engineers Association of California.
Publisher
Structural Engineers Association of California (SEAOC) 1400 K Street, Ste. 212
Sacramento, California 95814
Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]; Web address: www.seaoc.org
The Structural Engineers Association of California (SEAOC) is a professional association of four regional member organizations (Southern California, Northern California, San Diego, and Central California). SEAOC represents the structural engineering community in California. This document is published in keeping with SEAOC’s stated mission:
To advance the structural engineering profession; to provide the public with structures of dependable performance through the application of state-of-the-art structural engineering principles; to assist the public in obtaining professional structural engineering services; to promote natural hazard mitigation; to provide continuing education and encourage research; to provide structural engineers with the most current information and tools to improve their practice; and to maintain the honor and dignity of the profession.
SEAOC Board oversight of this publication was provided by 2012 SEAOC Board President James Amundson, S.E. and Immediate Past President Doug Hohbach, S.E.
Editor
International Code Council
Disclaimer
While the information presented in this document is believed to be correct, neither SEAOC nor its member organizations, committees, writers, editors, or individuals who have contributed to this publication make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this publication. The material presented in this publication should not be used for any specific application without competent examination and verification of its accuracy, suitability, and applicability. Users of information from this publication assume all liability arising from such use.
First Printing: September 2013
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 iii
Suggestions for Improvement
Comments and suggestions for improvements are welcome and should be sent to the following: Structural Engineers Association of California (SEAOC)
Don Schinske, Executive Director 1400 K Street, Suite 212
Sacramento, California 95814
Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]
Errata Notification
SEAOC has made a substantial effort to ensure that the information in this document is accurate. In the event that corrections or clarifications are needed, these will be posted on the SEAOC Web site at
www.seaoc.org and on the ICC Web site at www.iccsafe.org. SEAOC, at its sole discretion, may issue written errata.
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 v
Table of Contents
Preface to the 2012 IBC SEAOC Structural/Seismic Design Manual . . . xiPreface to Volume 1 . . . xiii
Acknowledgements . . . xv
References . . . xvii
How to Use This Document. . . xix
Design Example 1 Design Spectral Response Acceleration Parameters . . . .§11.4 . . . .1
Design Example 2 Design Response Spectrum . . . §11.4.5 . . . .3
Design Example 3 Site-Specific Ground Motion Procedures . . . §11.4.7 . . . .6
Design Example 4 Importance Factor and Risk Category . . . .§11.5 Seismic Design Category . . . .§11.6 . . . .11
Design Example 5 Continuous Load Path and Interconnection . . . §12.1.3 Connection to Supports . . . §12.1.4 . . . .13
Design Example 6 Combination of Framing Systems in Different Directions . . . §12.2.2 . . . .15
Design Example 7 Combination of Framing Systems in The Same Direction: Vertical . . . .§12.2.3.1 . . . .17
Design Example 8 Combination of Framing Systems in The Same Direction: Horizontal . . . .§12.2.3.3 . . . .23
Design Example 9 Combination Framing Detailing Requirements . . . §12.2.4 . . . .25
vi 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 Design Example 10
Dual Systems . . . .§12.2.5.1 . . . .28 Design Example 11
Introduction to Horizontal Irregularities . . . .§12.3.2.1 . . . .31 Design Example 12
Horizontal Irregularity Type 1a and Type 1b . . . .§12.3.2.1 . . . .32 Design Example 13
Horizontal Irregularity Type 2 . . . .§12.3.2.1 . . . .36 Design Example 14
Horizontal Irregularity Type 3 . . . .§12.3.2.1 . . . .38 Design Example 15
Horizontal Irregularity Type 4 . . . .§12.3.2.1 . . . .40 Design Example 16
Horizontal Irregularity Type 5 . . . .§12.3.2.1 . . . .42 Design Example 17
Introduction to Vertical Irregularities . . . .§12.3.2.2 . . . .43 Design Example 18
Vertical Irregularity Type 1a and Type 1b . . . .§12.3.2.2 . . . .44 Design Example 19
Vertical Irregularity Type 2 . . . .§12.3.2.2 . . . .48 Design Example 20
Vertical Irregularity Type 3 . . . .§12.3.2.2 . . . .50 Design Example 21
Vertical Irregularity Type 4 . . . .§12.3.2.2 . . . .52 Design Example 22
Vertical Irregularity Type 5a/5b – Concrete Wall . . . .§12.3.2.2 . . . .54
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 vii Design Example 23
Vertical Irregularity Type 5a/5b – Steel Moment Frame . . . .§12.3.2.2 . . . .56 Design Example 24
Elements Supporting Discontinuous Walls or Frames . . . .§12.3.3.3 . . . .60 Design Example 25
Elements Supporting Discontinuous Walls or Frames – Light-Frame . . . .§12.3.3.3 . . . .64 Design Example 26
Redundancy Factor r . . . §12.3.4 . . . .67 Design Example 27
Seismic Load Combinations: Strength Design . . . .§12.4.2.3 . . . .72 Design Example 28
Minimum Upward Force for Horizontal Cantilevers for SDC D through F . . . §12.4.4 . . . .75 Design Example 29
Interaction Effects . . . §12.7.4 . . . .78 Design Example 30
Seismic Base Shear . . . §12.8.1 . . . .80 Design Example 31
Approximate Fundamental Period . . . .§12.8.2.1 . . . .83 Design Example 32
Vertical Distribution of Seismic Forces . . . §12.8.3 . . . .87 Design Example 33
Horizontal Distribution of Forces . . . §12.8.4 . . . .91 Design Example 34
Amplification of Accidental Torsion . . . .§12.8.4.3 . . . .96 Design Example 35
Story Drift . . . §12.8.6 . . . .100
viii 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 Design Example 36
P-delta Effects . . . §12.8.7 . . . .103 Design Example 37
Scaling Design Values of Combined Response . . . §12.9.4 . . . .108 Design Example 38
Diaphragm Design Forces, Fpx: Lowrise . . . §12.10.1.1 . . . .112 Design Example 39
Diaphragm Design Forces, Fpx: Highrise . . . .§12.10.1.1 . . . .116 Design Example 40
Collector Elements – Flexible Diaphragm . . . §12.10.2 . . . .119 Design Example 41
Out-of-Plane Seismic Forces – One-Story Structural Wall . . . §12.11 and §13.3 . . . .123 Design Example 42
Out-of-Plane Seismic Forces – Two-Story Structural Wall . . . §12.11.1 and §12.11.2 . . . .127 Design Example 43
Wall Anchorage to Flexible Diaphragms . . . .§12.11.2.1 . . . .131 Design Example 44
Story Drift Limit . . . §12.12.1 . . . .134 Design Example 45
Structural Separation . . . §12.12.3 . . . .137 Design Example 46
Deformation Compatibility for Seismic Design Categories D through F . . . . §12.12.5 . . . .140 Design Example 47
Reduction of Foundation Overturning . . . §12.13.4 . . . .143 Design Example 48
Foundation Ties . . . §12.13.5.2, §12.13.6.2, and IBC §1810.3.13 . . . .147
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 ix Design Example 49
Simplified Alternative Structural Design Procedure . . . .§12.14 . . . .151 Design Example 50
Seismic Demands on Nonstructural Components on Rigid Supports . . . §13.3 and §13.4 . . . .154 Design Example 51
Seismic Demands on Vibration-Isolated Nonstructural Components . . . . §13.3 and §13.4 . . . .158 Design Example 52
Seismic Relative Displacements of Component Attachments . . . §13.3.2 . . . .161 Design Example 53
Exterior Nonstructural Wall Element . . . .§13.5 . . . .164 Design Example 54
Exterior Nonstructural Wall Element Connections . . . .§13.5 . . . .167 Design Example 55
Lateral Seismic Force on Nonbuilding Structure . . . .§15.4 . . . .174 Design Example 56
Flexible Nonbuilding Structure . . . §15.4 and §15.5 . . . .178 Design Example 57
Rigid Nonbuilding Structure . . . §15.4.2 . . . .181 Design Example 58
Retaining Wall with Seismic Lateral Earth Pressure . . . §15.6.1 . . . .183
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 xi
Preface to the 2012 IBC SEAOC Structural/Seismic
Design Manual
The IBC SEAOC Structural/Seismic Design Manual, throughout its many editions, has served the purpose of illustrating good seismic design and the correct application of building-code provisions. The Manual has bridged the gap between the discursive treatment of topics in the SEAOC Blue Book (Recommended
Lateral Force Requirements and Commentary) and real-world decisions that designers face in their practice. The examples illustrate code-compliant designs engineered to achieve good performance under severe seismic loading. In some cases simply complying with building-code requirements does not ensure good seismic response. This Manual takes the approach of exceeding the minimum code requirements in such cases, with discussion of the reasons for doing so.
Recent editions of the IBC SEAOC Structural/Seismic Design Manual have consisted of updates of previous editions, modified to address changes in the building code and referenced standards. Many of the adopted standards did not change between the 2006 edition of the International Building Code and the 2009 edition. The 2012 edition, which is the one used in this set of manuals, represents an extensive change of adopted standards, with many substantial changes in methodology.
Additionally, this edition has been substantially revised. New examples have been included to address new code provisions and new systems, as well as to address areas in which the codes and standards provide insufficient guidance. Important examples such as the design of base-plate anchorages for steel systems and the design of diaphragms have been added.
This expanded edition comprises five volumes: • Volume 1: Code Application Examples
• Volume 2: Examples for Light-Frame, Tilt-Up, and Masonry Buildings • Volume 3: Examples for Reinforced Concrete Buildings
• Volume 4: Examples for Steel-Framed Buildings
• Volume 5: Examples for Seismically Isolated Buildings and Buildings with Supplemental Damping Previous editions have been three volumes. This expanded edition contains more types of systems for concrete buildings and steel buildings. These are no longer contained in the same volume. Volumes 3 and 4 of the 2012 edition replace Volume 3 of the 2009 edition. Additionally, we have fulfilled the long-standing goal of including examples addressing seismic isolation and supplemental damping. These examples are presented in the new Volume 5.
In general, the provisions for developing the design base shear, distributing the base-shear-forces vertically and horizontally, checking for irregularities, etc., are illustrated in Volume 1. The other volumes contain more extensive design examples that address the requirements of the material standards (for example, ACI 318 and AISC 341) that are adopted by the IBC. Building design examples do not illustrate many of the items addressed in Volume 1 in order to permit the inclusion of less-redundant content.
Each volume has been produced by a small group of authors under the direction of a manager. The
managers have assembled reviewers to ensure coordination with other SEAOC work and publications, most notably the Blue Book, as well as numerical accuracy.
This manual can serve as valuable tool for engineers seeking to design buildings for good seismic response. Rafael Sabelli
Project Manager
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 xiii
Preface to Volume 1
Volume 1 of the 2012 IBC SEAOC Structural/Seismic Design Manual addresses the application and interpretation of the seismic provisions of the 2012 International Building Code. More specifically, Chapter 16 of the 2012 IBC requires compliance with the provisions of ASCE/SEI 7-10 “Minimum Design Loads for Buildings and Other Structures," except for Chapter 14 of ASCE 7.
ASCE 7 generally prescribes the loading and methodology to be used in the analysis of a structure or an element. In order to determine strength to resist to the load demands from ASCE 7, the IBC adopts national material design standards (such as ACI, AISC, MSJC, and NDS) to be used for the design of an element of a particular material. The Volume 1 examples focus on the application of the provisions of ASCE 7, while the examples in Volumes 2, 3, and 4 focus more on the application of the material design standards. The
Manual is not intended to serve as a building code or to be an exhaustive catalogue of all valid approaches. Volume 1 presents 58 examples covering most of the key code provisions within ASCE 7 Chapters 11, 12, 13, and 15. Many of the examples are similar to those in previous editions but have been rewritten to more clearly present the material and have been updated to reflect changes to the code provisions and SEAOC recommendations. Additionally, new examples are included in this edition that specifically address provisions related to site-specific ground-motion procedures, combination framing detailing requirements, scaling design values in modal response spectrum analysis, and retaining walls subject to seismic earth pressures.
Whenever possible, the authors have incorporated lessons learned from actual projects into the examples. Readers are welcome to submit other conditions or provisions not addressed in this edition for consideration in future editions.
Ryan A. Kersting Volume Manager
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 xv
Acknowledgements
Volume 1 of the 2012 IBC SEAOC Seismic Design Manual was written and reviewed by a group of highly qualified structural engineers, chosen for their knowledge and experience with structural engineering practice and seismic design. The authors are:
Ryan A. Kersting, S.E., Associate Principal, Buehler & Buehler Structural Engineers — Volume Manager and Author/Reviewer of Various Examples
Ryan has over 15 years of experience in the analysis, design, and review of building structures spanning the spectrum of conventional systems and materials. He is also frequently involved in projects that incorporate innovative structural systems, nonlinear analysis, and performance-based designs. Ryan has been very active in SEAOC, including previously serving as Chair of the SEAOC Seismology Committee, co-authoring / reviewing Blue Book articles, and serving as Chair of the 2007 SEAOC Convention. www. bbse.com
April Buchberger, S.E., Senior Structural Engineer, Clark Pacific — Author/Reviewer of Various Examples
April has 10 years of experience designing precast concrete structural systems and architectural cladding for the commercial, residential, health care, and government sectors in California. She is active in the SEAOCC (Central California) member organization of SEAOC, where she is currently serving on the Board of Directors and as Website Committee Chair. www.ClarkPacific.com
Timothy S. Lucido, S.E., Associate, Rutherford + Chekene — Author/Reviewer of Various Examples Tim has 10 years of experience in the seismic design and evaluation of building structures with
specialization in hospital design and steel-framed systems. He is a contributing member of SEAOC and SEAONC, including co-authoring the SEAOC Blue Book article “Concentrically Braced Frames.” He has developed proprietary data and software analysis tools for BRB manufacturers, has given webinars on BIM 3D shop drawing review and coordination, and is a BIM leader for Rutherford + Chekene. www.ruthchek.com Kevin Morton, S.E., Associate Principal, Hohbach-Lewin Structural Engineers — Author/Reviewer of Various Examples
Kevin has 12 years of experience designing new structures and retrofitting existing ones, with particular expertise in seismic analysis, value engineering, and precast parking structure design. He is an active member of SEAOC, having served on the state Seismology Committee for the past three years. www. hohbach-lewin.com
Nicolas Rodrigues, PE, SE, Associate, DeSimone Consulting Engineeers — Author/Reviewer of Various Examples
Nic has more than 10 years of experience in performing both code-based and performance-based designs of new highrise concrete and steel buildings in seismic zones around the world including California, Turkey, the UAE, and the Philippines. He has chaired several SEAOC committees, served on a PEER committee for the performance-based design of tall buildings, and actively participates in ACI. Nic was the responsible structural engineer for such notable projects as the 60-story Millennium Tower in San Francisco and the twisting, 42-story Emirates Pearl Hotel in Abu Dhabi. www.de-simone.com.
xvi 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1
Ali Sumer, Ph.D., S.E., Senior Structural Engineer, State of California Office of Statewide Health Planning and Development (OSHPD) — Author/Reviewer of Various Examples
Prior to joining OSHPD, Ali worked in private industry for eight years. He has focused on projects that incorporate seismic retrofitting, innovative structural systems, nonlinear analysis techniques, performance-based designs, building collapse risk analysis, and equipment shake-table tests. www.oshpd.ca.gov
Close collaboration with the SEAOC Seismology Committee was maintained during the development of the document. The Seismology Committee has reviewed the document and provided many helpful comments and suggestions. Their assistance is gratefully acknowledged.
Production and art was provided by the International Code Council. Cover photo credits:
Main photo: Rien van Rijthoven Architecture Photography Inset photos: Buehler & Buehler Structural Engineers, Inc.
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 xvii
References
Standards
American Concrete Institute. ACI 318: Building Code Regulations for Reinforced Concrete, Farmington Hills, Michigan, 2011.
American Society of Civil Engineers. ASCE 7: Minimum Design Loads for Buildings and Other Structures. ASCE 2010.
International Code Council. International Building Code (IBC). Falls Church, Virginia, 2012.
Other References
SEAOC Seismology Committee. Recommended Lateral Force Requirements and Commentary (Blue Book), Structural Engineers Association of California (SEAOC), Seventh Edition, Sacramento, California, 1999.
SEAOC Seismology Committee. SEAOC Blue Book Seismic Design Recommendations, Structural Engineers Association of California (SEAOC), First Printing, Sacramento, California, 2009. www.seaoc.org/bluebook
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 1
Design Example 1
Design Spectral Response Acceleration
Parameters §11.4
OVERVIEW
For a given building site, the risk-targeted maximum considered earthquake spectral response accelerations
SS, at short periods, and S1, at a 1-second period, are given by the acceleration contour maps in Chapter 22
in Figures 22-1 through 22-6. This example illustrates the general procedure for determining the design spectral response acceleration parameters SDSand SD1 from the mapped values of SSand S1. The parameters
SDSand SD1 are used to calculate the design response spectrum in Section 11.4.5 and the design base shear
in Section 12.8.
The easiest and most accurate way to obtain the spectral values is to use the “U.S. Seismic Design Maps” application from the USGS website (http://geohazards.usgs.gov/designmaps/us/application.php). The USGS application allows for values of SSand S1 to be provided based on the address or the longitude and
latitude of the site being entered.
PROBLEM STATEMENT
A building site in California is located at 38.123° North (Latitude 38.123°) and 121.123° West (Longitude -121.123°). The soil profile is Site Class D.
DETERMINE THE FOLLOWING:
1. Mapped risk-targeted maximum considered earthquake (MCER) spectral response acceleration
parameters SSand S1.
2. Site coefficients Fa and Fv and MCER spectral response acceleration parameters SMSand SM1
adjusted for Site Class effects.
3. Design spectral response acceleration parameters SDS and SD1.
1. Mapped MCE
RSpectral Response Acceleration Parameters
S
sand S
1§11.4.1
For the given site at 38.123° North (Latitude 38.123°) and 121.123° West (Longitude -121.123°), the USGS “U.S. Seismic Design Maps” application provides the values of
SS= 0.634g S1 = 0.272g.
2 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1
2. Site Coefficients F
aand F
vand MCE
RSpectral Response Acceleration
Parameters S
MSand S
M1Adjusted for Site Class Effects
§11.4.3
For the given Site Class D and the values of SSand S1 determined above, the site coefficients are
Fa= 1.293 T11.4-1
Fv = 1.856. T11.4-2
The MCER spectral response acceleration parameters adjusted for Site Class effects are
SMS= Fa SS= 1.292(0.634g) = 0.819g Eq 11.4-1
SM1= Fv S1= 1.857(0.272g) = 0.505g Eq 11.4-2
3. Design Spectral Response Acceleration Parameters S
DSand S
D1§11.4.4
SDS= (2/3) SMS= (2/3)(0.819g) = 0.546g Eq 11.4-3
SD1= (2/3) SM1= (2/3)(0.505g) = 0.337g Eq 11.4-4
Commentary
The USGS application “U.S. Seismic Design Maps” requires the risk category to be specified, even though that category is not necessary for determining SDS and SD1.
§11.4 Design Example 1 n Design Spectral Response Acceleration Parameters
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 3
Design Example 2
Design Response Spectrum
§11.4.5
PROBLEM STATEMENT
A building site in California has the following design spectral response acceleration parameters determined in accordance with Section 11.4.4 and mapped long-period transition period evaluated from Figure 22-12:
SDS= 0.55g SD1= 0.34g
TL = 8 sec.
DETERMINE THE FOLLOWING:
1. Design response spectrum.
1. Design Response Spectrum
§11.4.5
Section 11.4.5 provides the equations for the 5 percent damped spectral response acceleration, Sa, relative to period, T, in the following ranges:
0 ≤ T < T0, T0 ≤ T ≤ TS, TS < T ≤ TL, and TL < T
where:
T0 = 0.2 SD1 / SDS, TS = SD1 / SDS, and
TL = long-period transition period from Figures 22-12 through 22-16. Given the values above for this example,
T0 = 0.2 SD1 / SDS = 0.2(0.34g / 0.55g) = 0.12 sec TS = SD1 / SDS = (0.34g / 0.55g) = 0.62 sec, and TL = 8 sec.
Design Example 2 n Design Response Spectrum §11.4.5
4 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 The spectral response acceleration, Sa, is calculated as follows:
1. For the interval 0 ≤ T < T0 (0 ≤ T < 0.12 s),
Sa = SDS(0.4 + 0.6T/T0) Eq 11.4-5
Sa = 0.55g(0.4+0.6T/0.12) = (0.22 + 2.75T)g.
2. For the interval T0 ≤ T ≤ TS (0.12 s ≤ T ≤ 0.62 s), Sa = SDS = 0.55g.
3. For the interval TS< T ≤ TL (0.62 s < T ≤ 8 s),
Sa = SD1/T Eq 11.4-6
Sa = (0.34/T)g.
4. For the interval TL < T (8 s < T),
Sa = SD1TL/T2 Eq 11.4-7
Sa = 0.34g(8)/T2 = (2.72/T2)g.
From this information, the elastic design response spectrum for this site can be drawn, as shown below, in accordance with Figure 11.4-1:
T (sec) Sa (g) 0.00 0.22 0.12 0.55 0.62 0.55 0.75 0.45 1.00 0.34 1.50 0.23 2.00 0.17 4.00 0.09 8.00 0.04 10.00 0.03 §11.4.5 Design Example 2 n Design Response Spectrum
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 1 5
Figure 2-1.
Design response spectrum per Section 11.4.5
Design Example 2 n Design Response Spectrum §11.4.5
2012 IBC
®SEAOC STRUCTURAL/SEISMIC DESIGN MANUAL
Volume 2
EXAMPLES FOR LIGHT-FRAME, TILT-UP,
AND MASONRY BUILDINGS
ii 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2
Copyright
Copyright © 2013 Structural Engineers Association of California. All rights reserved. This publication or any part thereof must not be reproduced in any form without the written permission of the Structural Engineers Association of California.
Publisher
Structural Engineers Association of California (SEAOC) 1400 K Street, Ste. 212
Sacramento, California 95814
Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]; Web address: www.seaoc.org
The Structural Engineers Association of California (SEAOC) is a professional association of four regional member organizations (Southern California, Northern California, San Diego, and Central California). SEAOC represents the structural engineering community in California. This document is published in keeping with SEAOC’s stated mission:
To advance the structural engineering profession; to provide the public with structures of dependable performance through the application of state-of-the-art structural engineering principles; to assist the public in obtaining professional structural engineering services; to promote natural hazard mitigation; to provide continuing education and encourage research; to provide structural engineers with the most current information and tools to improve their practice; and to maintain the honor and dignity of the profession.
SEAOC Board oversight of this publication was provided by 2012 SEAOC Board President James Amundson, S.E., and Immediate Past President Doug Hohbach, S.E.
Editor
International Code Council
Disclaimer
While the information presented in this document is believed to be correct, neither SEAOC nor its member organizations, committees, writers, editors, or individuals who have contributed to this publication make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, fi ndings, conclusions, or recommendations included in this publication. The material presented in this publication should not be used for any specifi c application without competent examination and verifi cation of its accuracy, suitability, and applicability. Users of information from this publication assume all liability arising from such use.
First Printing: September 2013
00_FM 2012 IBC SSDM V2.indd ii
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 iii
Suggestions for Improvement
Comments and suggestions for improvements are welcome and should be sent to the following: Structural Engineers Association of California (SEAOC)
Don Schinske, Executive Director 1400 K Street, Suite 212
Sacramento, California 95814
Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]
Errata Notifi cation
SEAOC has made a substantial effort to ensure that the information in this document is accurate. In the event that corrections or clarifi cations are needed, these will be posted on the SEAOC web site at
www.seaoc.org and on the ICC web site at www.iccsafe.org.
SEAOC, at its sole discretion, may issue written errata.
00_FM 2012 IBC SSDM V2.indd iii
00_FM 2012 IBC SSDM V2.indd iv
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 v
Table of Contents
Preface to the 2012 IBC SEAOC Structural/Seismic Design Manual . . . vii Preface to Volume 2 . . . ix Acknowledgements . . . xi References . . . xiii How to Use This Document. . . xxi Design Example 1
Four-story Wood Light-frame Structure . . . 1 Design Example 2
Flexible Diaphragm Design. . . 109 Design Example 3
Three Story Light-frame Multi-family Building Design Using Cold-formed Steel
Wall Framing and Wood Floor and Roof Framing . . . 133 Design Example 4
Masonry Shear Wall Building . . . 245 Design Example 5
Tilt-up Building . . . 273
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00_FM 2012 IBC SSDM V2.indd vi
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 vii
Preface to the 2012 IBC SEAOC Seismic/Structural
Design Manual
The IBC SEAOC Seismic/Structural Design Manual, throughout its many editions, has served the purpose of illustrating good seismic design and the correct application of building-code provisions. The manual has bridged the gap between the discursive treatment of topics in the SEAOC Blue Book (Recommended
Lateral Force Requirements and Commentary) and real-world decisions that designers face in their practice.
The examples illustrate code-compliant designs engineered to achieve good performance under severe seismic loading. In some cases simply complying with building-code requirements does not ensure good seismic response. This manual takes the approach of exceeding the minimum code requirements in such cases, with discussion of the reasons for doing so.
Recent editions of the IBC SEAOC Seismic/Structural Design Manual have consisted of updates of previous editions, modifi ed to address changes in the building code and referenced standards. Many of the adopted standards did not change between the 2006 edition of the International Building Code and the 2009 edition. The 2012 edition, which is the one used in this set of manuals, represents an extensive change of adopted standards, with many substantial changes in methodology.
Additionally, this edition has been substantially revised. New examples have been included to address new code provisions and new systems, as well as to address areas in which the codes and standards provide insuffi cient guidance. Important examples such as the design of base-plate anchorages for steel systems and the design of diaphragms have been added.
This expanded edition comprises fi ve volumes: • Volume 1: Code Application Examples
• Volume 2: Examples for Light-Frame, Tilt-Up, and Masonry Buildings • Volume 3: Examples for Reinforced Concrete Buildings
• Volume 4: Examples for Steel-Framed Buildings
• Volume 5: Examples for Seismically Isolated Buildings and Buildings with Supplemental Damping Previous editions have been three volumes. This expanded edition contains more types of systems for concrete buildings and steel buildings. These are no longer contained in the same volume. Volumes 3 and 4 of the 2012 edition replace Volume 3 of the 2009 edition. Additionally, we have fulfi lled the long-standing goal of including examples addressing seismic isolation and supplemental damping. These examples are presented in the new Volume 5.
In general, the provisions for developing the design base shear, distributing the base-shear-forces vertically and horizontally, checking for irregularities, etc., are illustrated in Volume 1. The other volumes contain more extensive design examples that address the requirements of the material standards (for example, ACI 318 and AISC 341) that are adopted by the IBC. Building design examples do not illustrate many of the items addressed in Volume 1 in order to permit the inclusion of less-redundant content.
Each volume has been produced by a small group of authors under the direction of a manager. The
managers have assembled reviewers to ensure coordination with other SEAOC work and publications, most notably the Blue Book, as well as numerical accuracy.
This manual can serve as valuable tool for engineers seeking to design buildings for good seismic response. Rafael Sabelli
Project Manager
00_FM 2012 IBC SSDM V2.indd vii
00_FM 2012 IBC SSDM V2.indd viii
2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 ix
Preface to Volume 2
Volume 2 of the 2012 IBC SEAOC Structural/Seismic Design Manual addresses the design of light-frame, concrete tilt-up, and masonry shear wall building systems for seismic loading. These include the illustration of the design requirements for the shear walls and diaphragms, as were illustrated in previous editions, and also important interfaces with the rest of the structure.
The design examples in this volume represent a range of structural systems and seismic systems. The design of each of these systems is governed by standards developed by the American Concrete Institute (ACI) and the American Wood Council (AWC). The methods illustrated herein represent approaches consistent with the ductility expectations for each system and with the desired seismic response. In most cases there are several details or mechanisms that can be utilized to achieve the ductility and resistance required, and the author of each example has selected an appropriate option. In many cases alternatives are discussed. This manual is not intended to serve as a building code, or to be an exhaustive catalogue of all valid approaches and details.
This manual is presented as a set of examples in which the engineer has considered the building-code requirements in conjunction with the optimal seismic response of the system. The examples follow the guidelines of the SEAOC Blue Book and other SEAOC recommendations. The examples are intended to aid conscientious designers in crafting designs that are likely to achieve good seismic performance consistent with expectations inherent in the requirements for the systems.
Four examples have been included in past editions of this manual and are updated in this edition: four-story wood light-frame structure, light-gage framed building on podium structure, masonry shear wall building, and tilt-up building with windows. One example—wood diaphragm—is new and is included in this edition of the manual.
Douglas Thompson Volume 2 Manager
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2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 xi
Acknowledgements
Volume 2 of the 2012 IBC SEAOC Seismic/Structural Design Manual was written by a group of highly qualifi ed structural engineers, chosen for their knowledge and experience with structural engineering practice and seismic design. The authors are:
Douglas S. Thompson, S.E., S.E.C.B. – Volume Manager and Example 1
Doug Thompson has over 35 years of experience in designing of wood structures. He is author several publications in timber design including the WoodWorks publications: Four-story Wood-frame Structure over Podium Slab and Five-story Wood-frame Structure over Podium Slab. Doug has instructed license review classes in timber design for the PE and SE exams for 20 years. He is the 2013-2014 president of the Structural Engineers Association of Southern California and holds licenses in six states. www.stbse.com
John Lawson, S.E. – Examples 2 and 5
Assistant Professor John Lawson has provided structural engineering consulting services for over 30 years, including overseeing more than 100 million square feet of low-sloped roof and tilt-up concrete engineering. He now teaches in the Architectural Engineering department at California Polytechnic State University in San Luis Obispo. John is the recipient of the 2006 Tilt-up Concrete Association’s David L. Kelly Distinguished Engineer Award. www.arce.calpoly.edu
Michael Cochran, S.E., S.E.C.B – Example 3
Michael Cochran is an Associate Principal with Weidlinger Associates, Inc. in Marina del Rey, California, with over 25 years of design experience. He has an extensive background in the design of multi-story light-framed commercial and multifamily residential wood and cold-formed steel-stud buildings. He is a registered structural engineer in California, an active member of the AISC Connection Prequalifi cation Review Panel, a past president of the Structural Engineers Association of Southern California (SEAOSC), and incoming 2013-2014 president for the Structural Engineers Association of California.
Jeff Ellis, S.E. – Example 3
Manager of Codes, Standards, and Special Projects for Simpson Strong-Tie Company Inc., he has more than 22 years of experience in the construction industry. Mr. Ellis manages the company code and standards involvement as well as code reports. Additionally, he is involved in product development and offers technical guidance to customers for connectors, fastening systems, and lateral systems. He was a practicing design engineer for commercial, residential, and forensic projects for more than nine years prior to joining Simpson Strong-Tie at the end of 2000. He has served on the Board of Directors for SEAOSC, as chair of the 2011 and 2012 SEAOSC Buildings At Risk Summit, as chair of the AISI COFS Lateral Design Subcommittee, as president of the CFSEI and authored the Cold-Formed Steel Engineers Institute’s (CFSEI) Design Guide: Cold-Formed Steel Framed Wood Panel or Steel Sheet Sheathed Shear Wall
Assemblies.
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xii 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 Chukwuma G. Ekwueme, PhD, SE, LEED AP – Example 4
Dr. Ekwueme is an Associate Principal with Weidlinger Associates, Inc. in Marina del Rey, California. He has an extensive background in the design and analysis of a wide variety of structures, including concrete and masonry construction, steel and aluminum structures, and light-framed wood buildings. He is a
registered Structural Engineer in California and Nevada and is an active member of the main committee, the seismic subcommittee, and the axial fl exural loads and shear subcommittee of the Masonry Standards Joint Committee (MSJC).
Additionally, a number of SEAOC members and other structural engineers helped check the examples in this volume. During its development, drafts of the examples were sent to these individuals. Their help was sought in review of code interpretations as well as detailed checking of the numerical computations. The reviewers include:
James Lai, S.E. Alan Robinson, S.E. Tim Stafford, S.E. Doug Thompson, S.E. Tom VanDorpe, S.E.
Close collaboration with the SEAOC Seismology Committee was maintained during the development of this document. The Seismology Committee has reviewed the document and provided many helpful comments and suggestions. Their assistance is gratefully acknowledged.
Production and art was provided by the International Code Council.
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Cook, J., 2010, “Simplifi ed Analysis of Wood Shear Walls with Multiple Openings” Proceedings: Annual SEAOC Convention. Structural Engineers Association of California, Sacramento, California.
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CUREe, 1999, Proceedings of the Workshop on Seismic Testing, Analysis, and Design of Wood
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Dolan, J. D., 1996, Experimental Results from Cyclic Racking Tests of Wood Shear Walls with
Openings. Timber Engineering Report No. TE-1996-001. Virginia Polytechnic Institute and State
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Openings and Base Restraint Confi gurations. Timber Engineering Report No. TE-1997-001,
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Sacramento, California.
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Forest Products Laboratory, 2010, Wood Handbook Publication FPL—GTR—113. Madison, Wisconsin.
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Single-Family Dwellings. Applied Technology Council, Redwood City, California.
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2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 xvii Gupta, R., H. Redler, and M. Clauson, 2007. “Cyclic Tests of Engineered Shear Walls with Different
Bottom-plate and Anchor-bolt sizes (Phase II).” Department of Weed Science and Engineering,
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SCCACI/SEAOSC, 1982, Report of the Task Committee on Slender Walls, Southern California Chapter American Concrete Institute and Structural Engineers Association of Southern California, Los Angeles, California. September.
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Design Example 1
Four-story Wood Light-frame Structure
OVERVIEW
This design example illustrates the seismic design of selected elements for a four-story wood-frame hotel structure. The gravity-load framing system consists of wood-frame bearing walls. The lateral-load-resisting system consists of wood-framed bearing shear walls (common box-type system). A typical building elevation and fl oor plan of the structure are shown in Figures 1-1 and 1-2 respectively. A typical section showing the heights of the structure is shown in Figure 1-3. The wood roof is framed with pre-manufactured wood trusses. The fl oor is framed with prefabricated wood I-joists. The fl oors have a 1½-inch lightweight concrete topping. The roofi ng is composition shingles.
When designing this type of “mid-rise” wood-frame structure, there are several unique design elements to consider. The following steps provide a detailed analysis of some of the important seismic requirements of the shear walls per the 2012 IBC. This design example represents a very simple wood-framed wood structure; most wood-framed structures have several unique features requiring engineering design and detailing not shown in this design example.
This design example is not a complete building design. Many aspects have not been included, specifi cally the gravity-load framing system, and only certain steps of the seismic design related to portions of a selected shear wall have been illustrated. In addition, the lateral requirements for wind design related to the selected shear wall have not been illustrated (only seismic). The steps that have been illustrated may be more detailed than what is necessary for an actual building design but are presented in this manner to help the design engineer understand the process. For a more detailed listing of the items not addressed see Section 10.
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OUTLINE
1. Building Geometry and Loads
2. Calculation of the Design Base Shear
3. Location of Shear Walls and Diaphragms
4. Mechanics of Multi-story Segmented Shear Walls and Load Combinations
5. Mechanics of Multi-story Shear Walls with Force Transfer around Openings
6. The Envelope Process
7. Design and Detailing of Shear Wall at Line C
8. Diaphragm Defl ections to Determine if the Diaphragm is Flexible
9. Special Inspection and Structural Observation
10. Items Not Addressed in This Example
1.
Building Geometry and Loads
ASCE 7
1.1 GIVEN INFORMATION
The roof is 15/32-inch-thick DOC PS 1- or DOC PS 2-rated sheathing, with a 32/16 span rating and Exposure I glue.
The fl oor is 23/32-inch-thick DOC PS 1- or DOC PS 2-rated Sturd-I-Floor 24 inches o.c. rating, with a 48/24 span rating (40/20 span rating with topping is also acceptable) and Exposure I glue.
DOC PS 1 and DOC PS 2 are the U.S. Department of Commerce (DOC) Prescriptive and Performance-based standards for plywood and oriented strand board (OSB), respectively.
Wall framing is a “modifi ed balloon framing” where the joists hang from the walls in joist hangers. (See Figure 1-7 detail of this and an explanation of other common framing conditions.)
Framing lumber for studs and posts NDS T 4A
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Design Example 1 ◾ Four-story Wood Light-frame Structure
Douglas Fir Larch-No. 1 Grade:
Fb = 1,000 psi Fc = 1,500 psi Ft = 675 psi E = 1,700,000 psi Emin = 620,000 psi Cm = 1.0 Ct = 1.0
Common wire nails are used for shear walls, diaphragms, and straps. When specifying nails on a project, specifi cation of the penny weight, type, diameter, and length (example 10d common = 0.148 inch × 3 inches) are recommended.
Figure 1–1. Building elevation
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4 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 Design Example 1 ◾ Four-story Wood Light-frame Structure
Figure 1–2. Typical foundation plan
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Design Example 1 ◾ Four-story Wood Light-frame Structure
Figure 1–3. Typical fl oor framing plan
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6 2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 2 Design Example 1 ◾ Four-story Wood Light-frame Structure
Figure 1–4. Typical roof framing plan
Notes for Figure 1-2 through 1-4:
1. Non-structural “pop-outs” on the exterior walls at lines 1, 4 need special detailing showing the wood structural panel sheathing running continuous at lines 1, 4 and the pop-outs framed after the sheathing is installed.
2. All walls stack from the foundation to the fourth fl oor.
3. Designates sheathed wall per shear-wall schedule (see Table 1-32).
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2012 IBC
®SEAOC STRUCTURAL/SEISMIC DESIGN MANUAL
Volume 3
EXAMPLES FOR CONCRETE BUILDINGS
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Copyright
Copyright © 2013 Structural Engineers Association of California. All rights reserved. This publication or any part thereof must not be reproduced in any form without the written permission of the Structural Engineers Association of California.
Publisher
Structural Engineers Association of California (SEAOC) 1400 K Street, Ste. 212
Sacramento, California 95814
Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]; Web address: www.seaoc.org
The Structural Engineers Association of California (SEAOC) is a professional association of four regional member organizations (Central California, Northern California, San Diego, and Southern California). SEAOC represents the structural engineering community in California. This document is published in keeping with SEAOC’s stated mission:
To advance the structural engineering profession; to provide the public with structures of dependable performance through the application of state-of-the-art structural engineering principles; to assist the public in obtaining professional structural engineering services; to promote natural hazard mitigation; to provide continuing education and encourage research; to provide structural engineers with the most current information and tools to improve their practice; and to maintain the honor and dignity of the profession.
SEAOC Board oversight of this publication was provided by 2012 SEAOC Board President James Amundson, S.E. and Immediate Past President Doug Hohbach, S.E.
Editor
International Code Council
Disclaimer
While the information presented in this document is believed to be correct, neither SEAOC nor its member organizations, committees, writers, editors, or individuals who have contributed to this publication make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, fi ndings, conclusions, or recommendations included in this publication. The material presented in this publication should not be used for any specifi c application without competent examination and verifi cation of its accuracy, suitability, and applicability. Users of information from this publication assume all liability arising from such use.
First Printing: August 2013
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2012 IBC SEAOC Structural/Seismic Design Manual, Vol. 3 iii
Suggestions for Improvement
Comments and suggestions for improvements are welcome and should be sent to the following: Structural Engineers Association of California (SEAOC)
Don Schinske, Executive Director 1400 K Street, Suite 212
Sacramento, California 95814
Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]
Errata Notifi cation
SEAOC has made a substantial effort to ensure that the information in this document is accurate. In the event that corrections or clarifi cations are needed, these will be posted on the SEAOC web site at
www.seaoc.org and on the ICC web site at www.iccsafe.org.
SEAOC, at its sole discretion, may issue written errata.
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