CEE Earthquake Resistant Design General Information

Transcription

1 University of California at Berkeley Civil and Environmental Engineering Instructor: Stephen A. Mahin Spring Semester 2003 CEE Earthquake Resistant Design General Information Course Objectives This course integrates information from various engineering and scientific disciplines in order to provide a rational basis for the design of earthquake-resistant structures. As such, the course touches upon pertinent information from engineering seismology, geotechnical engineering, economic, risk and reliability theory and architecture in addition to advanced topics related to the dynamics and the analysis and design of structures. The focus of the course is on buildings, bridges, industrial facilities and other types of structures that may in the event of a major earthquake be allowed to respond in the inelastic range. The course emphasizes understanding the fundamental factors that influence and control the response of such structures, establishing a performance-based framework with which to assess seismic response, and developing effective, but simplified, design procedures capable of reliably achieving specified performance goals. Course Outline 1. Introduction. -- Basis of earthquake engineering design philosophies: role of uncertainty and the management of risk, an 'ideal' approach and some practical simplifications, limit state approaches, approaches adopted in current and emerging building code provisions. Special design considerations when permitting inelastic structural response are highlighted; limitations of historic analysis-based design approaches and introduction to "capacity design" concepts. Establishing a basis for performance-based earthquake engineering. 2. Engineering Characterization of Earthquake Ground Motions. -- Sources of earthquake ground motions; measures of earthquake intensity and damage potential; effects of local soil conditions on ground shaking; engineering estimation of ground motion characteristics based on deterministic and probabilistic approaches. 3. Response of Simple Structural Systems to Different Types of Ground Motion. -- Assessment of the effect of structural system and ground motions on the response of simple one and multiple degree of freedom systems. Emphasis on identifying desirable characteristics of structures for various types of ground shaking, and on developing simplified procedures suitable for estimating seismic response during the preliminary design process.

2 4. Development of Design Earthquakes for Linear Structural Response. -- Identification of critical parameters -- influence of local soil conditions and structural damping; development of design spectrum. 5. Development of Design Earthquakes for Nonlinear Structural Response. - Identification of critical parameters -- influence of local soil conditions, viscous damping, duration of shaking, nonlinear mechanical characteristics of the structure, and geometric nonlinearities; development of design spectra from ground motion and structural characteristics; displacement estimates; alternative spectra formats; extension of design spectra to multi-degree of freedom systems. 6. Analytical Procedures for Preliminary/Conceptual Design and Proportioning of Structural Systems. -- Introduction to simple plastic theory; estimation of the maximum strength and deformation capacities of structural systems; simplifications for design of multistory structures; application of capacity design methods. Emphasis on ductile moment-resisting frames and braced frames. Methods discussed to control displacements and other response parameters of structural interest. 7. Code Related Issues. -- Basis and limitations of current code provisions for structural analysis and design. Future trends. Nonlinear static pushover procedures for evaluation of new and existing structures, development of target displacements. 8. Basic Performance-based Evaluation and Design Issues. -- Lessons from past earthquakes; quantification of performance objectives and levels for seismic resistant design; Selection of analysis procedures; numerical modeling of structural systems. Estimation of the confidence of a structure s ability to achieve its targeted performance objective. Current and emerging guidelines for the evaluation of existing and new structures. 9. Applications. -- Steel (and to a lessor extent reinforced concrete) details to insure member and connection ductility; basic design considerations for moment-resisting frames and concentrically braced frames. Issues related to seismic retrofit. Application of concepts to structures employing seismic isolation or utilizing supplemental energy dissipation devises. Prerequisites Students are expected to have a background in elastic structural analysis and structural dynamics. A basic understanding of inelastic structural analysis is required. Courses such as CEE 220 and CEE 225, or their substantial equivalent, satisfy this requirement. Students uncertain about the adequacy of their preparation should contact the instructor. 2

3 Required Course Materials Course notes will available on-line. Typically, course notes for the coming week will be posted on Monday. The course web site (Earthquake Resistant Design Interactive: also contains a number of applications that will prove useful in demonstrating some of the concepts introduced or developed in the class. Copies of handout materials, problem sets, review questions and some papers may also be downloaded from the site. The website also provides a number of important and interesting links to other related sites. Please note that this site is under construction and that items will be changed or added throughout the semester. Students are expected to regularly read papers and sections of reports. Copies of the papers will be distributed in class, made available for copying in the engineering library on campus, or available for download from the National Information Service for Earthquake Engineering ( or elsewhere. In addition, specific supplemental reading assignments will be made from the following sources: 1. Introduction to Structural Dynamics and Earthquake Engineering by Anil Chopra, Prentice Hall, NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA 356), FEMA/ASCE, Washington DC, Download from com/0_0_ Misc/0_1_FEMADocuments/fema356/ps-fema356.html. 3. The 2000 NEHRP Recommended Provisions For New Buildings And Other Structures (FEMA 368) FEMA, Washington DC, Download from 4. Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment- Frame Buildings(FEMA 351), FEMA, Washington DC, July Several computer programs will be utilized in the course to illustrate concepts and to complete homework assignments. These include applications on the course WWW site ( and PC-compatible programs for the dynamic analysis of single and multiple degree of freedom systems. The program BiSpec, used for computing the response of single degree of freedom subjected to one or two horizontal components of excitation, will be extensively used and should be downloaded from: Program manuals (on-line and hardcopies) can be obtained from the same site. A computer program, NONLIN, for computing the nonlinear dynamic response of multiple degree of freedom systems will be distributed later in the course. Three commercial computer programs for computing the static nonlinear response of structures under monotonically increasing lateral loads will be available for use (CAPP, SAP 2000n, ETABS). 3

4 Course Organization The course will have two 1-1/2 hour lectures per week. It meets in 534 Davis Hall. Depending on interests of students, a weekly discussion session will be organized, which will be devoted to discussion of conceptual and analytical approaches presented in the class and for help in solving homework assignments. There will be no final exam, but a term project will be required. The term project may be done individually, or in groups of two. Grades will be based on performance on homework assignments, several midterm quizzes, and a final term project, according to the following approximate weights: 25%, 40% and 35%. Reference Material A wide variety of reference material is available. For example, several good (but expensive) textbooks exist. These may provide useful information on a number of topics not covered by the book used in this course. These books include: 1. Earthquake Engineering Handbook, W-F. Chen, C. Scawthorn, CRC Press, The Seismic Design Handbook, F. Naeim, Ed., Van Nostrand/Reinhold, New York, NY, Geotechnical Earthquake Engineering, Steven Kramer, Prentice Hall, Earthquake Engineering, Hu, Y-X, Liu, S-C and Dong, W, E&FN Spon, London, Design of Earthquake Resistant Buildings, Wakabayashi, M., McGraw-Hill, New York, NY, Earthquake Resistant Design, Dorwick, D., Wiley, New York, NY, Fundamentals of Earthquake Engineering, Newmark,N.andRosenblueth,E., Prentice Hall, New York, NY, Design of Ductile Steel Structures, Bruneau,M.,Uang,C-M,andWhittaker,A., McGraw-Hill, Steel Structures: Controlling Behavior Through Design, Robert Englekirk, Wiley,

5 10. Earthquake Spectra and Design, Newmark,N.andHall,W., EERI,Oakland, CA Some other useful, code-related documents include: 1. Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings, FEMA 350, Federal Emergency Management Agency, Washington DC, July Recommended Post-Earthquake Evaluation and Repair Criteria for Welded Steel Moment-Frame Buildings (FEMA 352), FEMA, Washington DC, July Specifications and Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications (FEMA 353), FEMA, Washington DC, July prepandprev.shtm#earthquakes 4. SEAOC, Recommended Lateral Force Requirements and Commentary (the Blue Book ), Sacramento, CA, 1999 (see 5. California Building Code, Title 24, California Administrative Code, 2001 edition (see 6. HAZUS, a natural hazard loss estimation methodology, FEMA in partnership with the National Institute of Building Sciences, Washington DC. Note that hardcopies of FEMA documents may be generally obtained for free by calling Some important sources of information include: 1. The Pacific Earthquake Engineering Research (PEER) Center at the Richmond Field Station. It can be reached at 2. The National Information Service for Earthquake Engineering (NISEE) has its offices at the Richmond Field Station. It has the worlds largest library related to earthquake engineering. The WWW site for NISEE has a variety of user features, including an on-line search feature, library of earthquake damage photos, downloadable computer programs, and so on. The homepage for NISE is Many other useful URLs are available on the course homepage. 5

6 University of California at Berkeley Civil and Environmental Engineering Instructor: Stephen A. Mahin Spring Semester 2003 CEE Earthquake Resistant Design Basic Guidelines for Designing Damage Tolerant Structures 1. Avoid unnecessary mass. Achieve a uniform distribution of mass. 2. Preserve symmetry. Avoid significant torsional motions. 3. Us as simple a structural system as possible. Make sure there is a complete load path. 4. Use a redundant structural system. Use a backup structural system where ever possible. 5. Structure should be compact and regular in both plan and elevation. Avoid structures with elongated or irregular plans; having substantial setbacks in elevation; or that are unusually slender. 6. Use a uniform and continuous distribution of stiffness and strength. Avoid nonstructural components that could unintentionally effect this distribution. Avoid sudden changes in member sizes or details. 7. Permit inelastic action (damage) only in inherently non-critical ductile elements (i.e., in beams rather than columns). 8. Detail the members to avoid premature, brittle failure modes. Utilize capacity design principles to avoid undesired shear, axial or joint failures and to foster ductile flexural failure modes. 9. Avoid hammering (pounding) of adjacent structures. 10. Tie all structural components together. Anchor nonstructural components to structure to avoid falling hazards. 11. Avoid systems with low amounts of viscous damping. Absence of nonstructural components tied to structure may be indication of low damping in steel structures. 6