: The American Society of Civil Engineers
: 24.28 MB
Preface The purpose of this guide is to provide examples related to the use of the Standard ASCE/SEI 7-10, Minimum Design Loads for Buildings and Other Structures (often referred to as ASCE 7). The guide is also pertinent to users of the 2012 International Building Code (ICC, 2011 ) because the IBC refers directly to ASCE 7. Sections of ASCE 7 Pertinent to the Guide Seismic Loads: Guide to the Seismic Load Provisions of ASCE 7-10 (the Guide ) has examples pertinent to the following chapters of ASCE 7: Chapter 1: General Chapter 2: Combinations of Loads Chapter 11: Seismic Design Criteria Chapter 12: Seismic Design Requirements for Building Structures Chapter 16: Seismic Response History Procedures Chapter 20: Site Classifi cation Procedure for Seismic Design Chapter 22: Seismic Ground Motion and Long Period Maps Seismic material excluded from the Guide are Chapter 13 (Nonstructural Components), Chapter 14 (Material-Specifi c Design and Detailing Requirements), Chapter 15 (Nonbuilding structures), Chapter 17 (Seismic Design Requirements for Seismically Isolated Structures), Chapter 18 (Seismic Design Requirements for Structures with Damping Systems), Chapter 19 (Soil-Structure Interaction for Seismic Design), and Chapter 21 (Site-Specifi c Procedures for Seismic Design). The vast majority of the examples in the Guide relate to Chapters 1, 2, 11, 12, and 16 of ASCE 7, with buildings as the principal subject. The materials on nonstructural components and on nonbuilding structures will be expanded in a later edition of the Guide , or in a separate volume. The materials presented for Chapter 16 relate to the selection and scaling of ground motions for response history analysis and the use of linear response history analysis. Chapter 14 of ASCE 7 is not included because the Guide focuses principally on seismic load analysis and not seismic design. The reader is referred to the Reference section of the Guide for resources containing design examples. The materials included in Chapters 17 through 19 are considered “advanced topics” and may be included in a future volume of examples. The principal purpose of the Guide is to illustrate the provisions of ASCE 7 and not to provide background on the theoretical basis of the provisions. Hence, theoretical discussion is kept to a minimum. However, explanations are provided in a few instances. The reference section contains several sources for understanding the theoretical basis of the ASCE 7 seismic loading provisions. Specifi cally, the reader is referred to the expanded commentary to the ASCE Seismic Provisions. Note that this commentary was fi rst available in the third printing of ASCE 7. Additional useful documents provided by FEMA (at no charge) are as follows: FEMA P-749, “Earthquake Resistant Design Concepts” (FEMA, 2010 ); FEMA P-750, “NEHRP Recommended Seismic Provisions for New Buildings and Other Structures” (FEMA, 2009a ); and FEMA P-751, “NEHRP Recommended Provisions: Design Examples” (FEMA, 2012 ). FEMA P-751 contains numerous detailed design examples that incorporate many of the requirements of ASCE 7-05 and ASCE 7-10. These examples are much more detailed than those provided in this Guide and concentrate on the structural design aspects of earthquake engineering, rather than just the loads and analysis side, which is the focus of the Guide . The National Institute of Building Standards (NIST) provides another excellent set of seismic analysis and design references. These “technical briefs” cover various subjects, including diaphragm behavior, design of moment frames, design of braced frames, and nonlinear structural analysis. The briefs can be downloaded at no charge from www.nehrp-consultants .org. How to Use the Guide The Guide is organized into a series of individual examples. With minor exceptions, each example “stands alone” and does not depend on information provided in other examples. This means that, in some cases, information is provided in the beginning of the example that requires some substantial calculations, but these calculations are not shown. For instance, in the example on drift and P-delta effects (Example 19), the details for computing the lateral forces used in the analysis are not provided, and insuffi cient information is provided for the reader to back-calculate these forces. However, reference is made to other examples in the Guide where similar calculations (e.g., fi nding lateral forces) are presented. The reader should always be able to follow and reproduce all new numbers (not part of the given information) that are generated in the example. Table and Figure Numbering The examples presented in the Guide often refer to sections, equations, tables, and fi gures in ASCE 7. All such items are referred to directly, without specifi c reference to ASCE 7. For instance, a specifi c example might contain the statement, “The response modifi cation factor R for the system is provided by Table 12.2-1.” References to sections, equations, tables, and fi gures that are unique to the Guide are always preceded by the letter G and use bold text. For example, the text may state that the distribution of forces along the height of the structure are listed in Table G12-3 and illustrated in Fig. G12-5 . In this citation, the number 12 is the example number, and the number after the dash is the sequence number of the item (that is, third table or fi fth fi gure). Notation and Defi nitions The mathematical notation in the Guide follows directly the notation provided in Chapter 11 of ASCE 7. However, as the Guide does not use all of the symbols in ASCE 7, a separate list of symbols actually used in the Guide is provided in a separate section titled “Symbols Unique to the Guide. ” This list also provides defi nitions for new symbols that have been introduced in the Guide . Computational Units All examples in the Guide are developed in the U.S. customary (English) system, as follows (with the standard abbreviation in parentheses): Length units: inches (in.) or feet (ft) Force units: pounds (lb) or kips (k) Time units: seconds (s). All other units (e.g., mass) are formed as combinations of the aforementioned units. A unit conversion table is provided. Appendices and Frequently Asked Questions In addition to the 22 individual examples, the Guide contains three appendices. The fi rst appendix provides interpolation tables that simplify the process of calculating some of the values (e.g., site coeffi cients F a and F v ) required by ASCE 7. The second and third appendices explain the use of web-based utilities for determining ground motion parameters and for selection of ground motion records for response history analysis. The Guide also contains a special section titled “Frequently Asked Questions,” where several common questions are listed, together with the author ’ s answers. In some cases, this requires an interpretation of ASCE 7, especially when the standard is ambiguous. User Comments Users are requested to notify the author of any ambiguities or errors that are found in this Guide . Suggestions for improvement or additions are welcomed and will be included in future versions of the Guide . Disclaimer The interpretations of ASCE 7 requirements and any and all other opinions presented in this guide are those of the author and do not necessarily represent the views of the ASCE 7 Standard Committee or the American Society of Civil Engineers.