TODO LO QUE DEBE SABER PARA REALIZAR UN CURSO Y SALGAN BUENOS ESTIMADORES DE RIESGO...
An Introduction to EarthquakeResistant Design Stephen Mahin
Nishkian Professor of Structural Engineering University of California at Berkeley 777 Davis Hall 642-4021;
[email protected] CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
©UC Regents
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The Earthquake Challenge Earthquakes provide one of the most challenging problems facing the structural engineering profession Important social and economic problem Field is rapidly changing Changing demands by society New tools for design and analysis New technologies Basic concepts and tools relevant to design to resist other forms of natural and human-induced hazards
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Today
Course Organization Sources of Earthquake Damage Trends in Earthquake Engineering
Evolution of building codes Genesis of performance-based approaches to earthquake engineering
Scope of Course
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
©UC Regents
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Course Organization Contact Information
Instructor:
Stephen Mahin
777 Davis Hall, 642-4021,
[email protected] Office Hours: Tentatively TuTh 1-2 or by appointment
Teaching Assistant: Janise Rodgers
504 Davis Hall
[email protected] Office Hours: TBD
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Course Organization Lectures
TuTh 11-12:30 534 Davis Hall
Review and Discussion Session ?
Weekly session with Graduate Student Instructor or Professor. Clarify important points in class or carry out examples. Help with homework assignments. Time slot to make up missed classes.
Time to be determined
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Course Organization Prerequisites
Advanced course in structural analysis (CEE 220/121) Course in structural dynamics through modal analysis
and use of linear response spectrum techniques for multiple degree of freedom systems (CEE 225/125). Some design background. Some familiarity with plastic analysis.
Questions on student background:
Capacity design concepts (CE 244) and simple plastic analysis (CEE 248)? Computer tools? SAP? ETABS? OpenSees? CEE 221? CEE 227 - Earthquake Engineering U.C. Berkeley
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On-Line Course Notes Annotated interactive course outline available at: http://peer.berkeley.edu/course_mod ules/eqrd/
Still under construction
Includes class notes, handouts, homework problems, most solutions, review questions, as well as:
Various analytical tools Links Other useful information
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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FEMA References FEMA publications available for free by downloading from the web or calling 1-800-480-2520
The 2000 NEHRP Recommended Provisions For New Buildings And
Other Structures (FEMA 368) FEMA, Washington DC, 2000, http://www.bssconline.org/NEHRP2000/comments/provisions/ Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings(FEMA 351), Specifications and Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications (FEMA 353), Seismic Design Criteria for New Steel Moment-Frame Buildings (FEMA 350), FEMA, Washington DC, July 2000. http://www.fema.gov/library/ prepandprev.shtm#earthquakes NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA 356), FEMA/ASCE, Washington DC, 1997. http://www.degenkolb.com/0_0_ Misc/0_1_FEMADocuments/ fema356/ps-fema356.html.
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Useful References
Various Technical Papers
On Reserve in Engineering Library From course website or other provided URLs.
Frequent reference to:
“Structural Dynamics and Earthquake
Engineering,” A. Chopra, Prentice Hall, 2000.
Reference Texts:
“Earthquake Engineering Handbook,”
Scawthorn, CRC Press, 2002.
W-F. Chen; C.
“Seismic Design Handbook,” F. Naiem, 2nd ed., Kluwer Press, 2001. “Earthquake Geotechnical Engineering,” S.Kramer, Prentice Hall, 1995. CEE 227 - Earthquake Engineering U.C. Berkeley
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Important Sources of Information National Information Service for Earthquake Engineering http://nisee.berkeley.edu
Library, located at Pacific
Earthquake Engineering Research Center, Richmond Computer applicationsProvides non-proprietary computer software and ground motions library
Earthquake Engineering Research Institute, Oakland, CA http://www.eeri.org
CEE 227 - Earthquake Engineering U.C. Berkeley
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Nonlinear Analysis of Structural Systems Download: http://www.ce.berkeley.edu/~hachem/bispec/index.html
Bispec
Single-DOF systems
subjected to one or two components of one or more earthquake records Response spectra Animation Online and downloadable help manuals
Other programs (NONLIN, CAPP, ETABS, SAP) will be made available later
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Course Organization Assignments
Reading Homework Assignments
Sequence of problems related
to design and evaluation of a single building Quantitative as well as discussion type questions
Grading Homework, 25% Quizzes, 40% Project, 35%
Midterm Quizzes
Equivalent of two 80 minute
midterm exams ( 4-40 minute or 5-35 minute quizzes)
Term Project
Design or research type project of your choice
One of many possible projects
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Course Organization
Questions? nisee
CEE 227 - Earthquake Engineering U.C. Berkeley
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Review Sources of Damage Damage caused by:
Ground shaking
Fault rupturing Liquefaction and soil movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures (pounding)
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing Liquefaction and soil movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures (pounding)
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing
Liquefaction and soil
movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures (pounding)
nisee
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing Liquefaction and soil
movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures (pounding)
nisee
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing Liquefaction and soil movement Slope instability and
landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures (pounding)
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing Liquefaction and soil movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures (pounding)
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
©UC Regents
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing Liquefaction and soil movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Review Sources of Damage Damage caused by:
Ground shaking Fault rupturing Liquefaction and soil movement Slope instability and landslides Tsunami and seiche Fire Flooding Interaction with adjacent structures
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
©UC Regents
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Trends in Earthquake Engineering
Rapid evolution of model building codes and ad hoc guidelines for design of special structures and evaluation and rehabilitation of existing structures Fundamental approaches being developed for performance-based engineering design and evaluation
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Rapid evolution of building codes Focus is on prevention of major catastrophes associated with structural collapse Changes in code provisions usually tied to observed damage in major earthquakes Damage to buildings on soft soil soil factors Damage to tops of tall structures concentrated forces applied at top of structures Damage in R/C columns ductile details
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Basic Design Guidelines from Past Earthquakes 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.
1.
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 unintentionally effect this distribution. Avoid sudden changes in member sizes or details.
5.
CEE 227 - Earthquake Engineering U.C. Berkeley
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Basic Guidelines (Continued) 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.
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Building codes are useful design tools Define “standard of care” ... important legal and professional concept. But ... focus is on minimum standards needed for the protection of life safety “ provide minimum standards to safeguard life or limb, health, property and public welfare by regulating
g Buildin Code
and controlling the design, construction, quality of materials, use and occupancy, location and maintenance of buildings.”
A detailed, prescriptive “deemed-to-comply” format used. Contains a mix of empiricism, simplified theory and expert judgment. Current codes provide little guidance on how various stipulations relate to performance.
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Codes improving, but not perfect ...
Uneven performance of model code-compliant buildings noted in recent earthquakes. Some perform very well, while others are inadequate.
Nearly 70% of new steel buildings
shaken by the Northridge earthquake suffered brittle fractures in their welded beam to column connections. More than 10% of new steel welded moment frame buildings in Kobe collapsed. Several new reinforced concrete structures collapsed or were severely damaged during the Northridge and Loma Prieta earthquakes. Important buildings designed by well respected engineers, under stringent quality control conditions are frequently damaged.
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Problems becoming more complex
Expected ground motions more severe and complex than previously assumed.
Concern for near-source, soft soil,
long duration motions ... the big one.
Public’s tolerance for damage has diminished due to apparent increase in the frequency of damaging earthquakes
Recent earthquakes Near Los Angeles and San Francisco Turkey, Taiwan and Japan Highly publicized probabilistic predictions
No longer considered a rare “act of god.” Insurance companies and building owners concerned with maximum probable economic losses Minimizing disruption of services important CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Situation is in flux!
Addition of new technologies for seismic
resistance (isolation, supplemental damping, buckling restrained bracing, composite members, etc.) Quantitative, not qualitative, answers wanted Addition of new analysis and design tools (nonlinear static and dynamic analysis, probabalistic hazard maps, etc.) Economic and social impacts more important Developments do not all have same objectives Life safety. How safe? Stated performance goals may differ What is meant by performance state (e.g., continued occupancy) Targeted confidence levels vary
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Some considerations Traditional Analysis problem
Need tool box
analysis of demands on structure analysis of capacity of
Given structure and loading, check that Demands < Capacity
Design problem
structure
Identify attributes of a structure that for given earthquake environment will economically and reliably satisfy stated performance expectations.
Need to manage risk and uncertainty
Rational load and resistance factors Utilize system characteristics
inherently insensitive to uncertainties in seismic hazard Focus more on displacement and stability than force
CEE 227 - Earthquake Engineering U.C. Berkeley
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Towards Performance-based Engineering No need to wait for next earthquake to improve seismic design and evaluation methods
Probabilistic framework Probabalistic seismic hazard assessment Integrate research on system and element behavior Computational tools for predicting seismic demands on systems and elements Computational tools to predict capacity of systems and elements to resist expected demands Relate engineering parameters to parameters owners and decision makers can understand (cost, disruption, etc.)
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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From research to practice No longer need to wait
until the next earthquake Testing has had a big impact on structural engineering knowledge and practice
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CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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From research to practice No longer need to wait
until the next earthquake Testing has had a big impact on structural engineering knowledge and practice Greatly improved details
QuickTime™ and a YUV420 codec decompressor are needed to see this picture.
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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From research to practice No longer need to wait
until the next earthquake Testing has had a big impact on structural engineering knowledge and practice Greatly improved details Validated computer models
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Structural Engineering Practice
More and better education Regularly use computer simulation models in design Rigorous inspection of construction Codes include advanced analysis methods Introduction of new technologies and devices Seismic isolation, supplemental energy dissipation devices Performance-based engineering frameworks
QuickTime™ and a YUV420 codec decompressor are needed to see this picture.
QuickTime™ and a YUV420 codec decompressor are needed to see this picture.
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Severity of Damage
Joe’s
Joe’s
Joe’s Beer! Food!
Operational
0%
Beer! Food!
Immediate Occupancy
Beer! Food!
Life Safety
Damage
Collapse Prevention 99%
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Damage related to demand parameters Joe’s
Joe’s
Beer! Food!
Lateral REsistance
Beer! Food!
Joe’s Beer! Food!
Structural Displacement ∆
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Relate Probabilities of Exceedence to Damage States Occasional
Very Rare
Joe’s
Joe’s Beer! Food!
Beer! Food!
10
1
Joe’s
0.1
Beer! Food!
0.01
0.001
0.1
0.01
0.0001
Pea k Ground Acceleration - g
Rare
Frequent (25 years)
Annual Probability of Exceedance
CEE 227 - Earthquake Engineering U.C. Berkeley
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Quantification of Earthquake Hazard
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
Structural Engineering Tools Improve Greater demands for quantitative design and evaluation methods that realistically and explicitly account for performance Improving analysis tools Analysis Engine
Improving characterization of performance
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Improved proportioning strategies
Capacity Design Improved earthquake characterization Probability
Hazard Model
Sd Improving control of uncertainties
Demand Capacity
Damage Models
Probability
Reliability Model
Fails
δ
Improved assessment of losses
Loss Models
$
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Performance-Based Design Approaches Capacity Design
Damage Models Analysis Engine
Loss Models
Probability
Demand Capacity
Reliability Model
$
Fails?
δ
Probability
Hazard Model
Sd
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Much activity to improve codes Improved national codes
National Earthquake Hazard Reduction Program (NEHRP) Tentative Provisions for Seismic Design of Buildings (Building Seismic Safety Council)
International Building Code (merging of three main model codes used in the US and incorporating NEHRP provisions.
New approaches
Improved performance and reliability Performance -based design (EERC/FEMA) Vision 2000 (SEAOC) SAC Steel Project (FEMA 350 FEMA 353) Next generation codes (NSF, FEMA) Existing Buildings Guidelines for the Rehabilitation
of Existing Buildings (FEMA 356)
CEE 227 - Earthquake Engineering U.C. Berkeley
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Earthquake-Resistant Design
What’s covered Course outline
CEE 227 - Earthquake Engineering U.C. Berkeley
Spring 2003
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Rational framework needed Need balanced perspective to integrate information from:
structural analysis structural behavior seismology geotechnical engineering economics and public policy risk and reliability analysis
Focus on objectives, not procedures or prescriptions Rely on first principles CEE 227 - Earthquake Engineering U.C. Berkeley
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Some basic issues treated in course Identify key response parameters How to get a structure that behaves as expected? How do different ground motion characteristics effect structures? How do different structural materials & systems behave? How do you change system to improve performance? Effect of designer decisions about proportions on response. How to characterize reliability of a system? What simplified tools should be used in design? What analysis tools can be used to assess performance? CEE 227 - Earthquake Engineering U.C. Berkeley
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Course Overview
Introduction Engineering Characterization of Ground Motions Sensitivity of Seismic Response of Simple Systems to Ground Motion and Structural Characteristics Development of Design Earthquakes (Linear & Nonlinear) Analytical Tools for Preliminary/Conceptual Design Design Issues and Approaches Code-related Issues - Interpretation and future trends Performance-based Design Capacity Design / Damage Tolerant Design
Applications Moment Resisting and Braced Frames (mainly steel) New construction and retrofit Special topics CEE 227 - Earthquake Engineering U.C. Berkeley
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Scope of Course
Questions? nisee
CEE 227 - Earthquake Engineering U.C. Berkeley
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