Area 3Assessment and Design Methodologies
Helmut Krawinkler (Stanford), Thrust Leader
The objective of research in this thrust area is to develop (a) a comprehensive reliability-based methodology for socio-economic and engineering performance assessment of structural, nonstructural, and content systems, and (b) performance-based design procedures that account explicitly for multiple performance objectives with respective acceptable risks or target reliabilities. The focus is on a systems approach, starting from the seismic hazard, considering the complete soil-foundation-structure system, and for buildings considering structural, nonstructural (e.g., architectural and mechanical), and contents systems. The assessment should incorporate the best available scientific predictions of the performance of the facilities under both mild and extreme shaking. The emphasis is on individual facilities (buildings, highway bridges), but networked facilities (university or industrial campus, transportation networks) will also receive attention.
Central to the research performed in this thrust area is the systematic consideration of the important uncertainties in every element of the problem, and of the propagation of uncertainties throughout the problem (from seismic hazard to response prediction to damage prediction to the evaluation of decision variables). PBEE must be formulated in a reliability-based framework, but the implementation must be simple enough to be usable by the profession. Emphasis in research is on reducing the uncertainties, establishing measures of uncertainties (epistemic and aleatory), and developing a methodology that accounts for these aspects in the design and evaluation process.
The research in this thrust builds on performance-based engineering frameworks developed recently through professional efforts (e.g., FEMA, ATC, SEAOC, and SAC) and refined by various researchers. However, these frameworks are viewed only as models that may, or may not, be recognizable in the final outcome of this effort. Indeed, in the past two years the efforts of this thrust have led to the formulation of a general framework applicable to methodologies that focus on either specific performance levels or on costs and society/owner constraints (e.g., fatality risk). The emphasis of the performance assessment research will be on the life safety level (related to partial and complete collapse limit states), on loss estimation (and lifecycle costs) and downtime. These are the issues that have been identified by PEERs industry partners as the critical ones for our global objective, which is to provide knowledge, procedures, and tools in support decision making. Meetings with our industry partners will continue to be an important vehicle for receiving industry feedback on the direction of the research.
International Workshop on Performance-Based Earthquake Engineering—3162002
Jack Moehle (UCB/F)
The goal of this project is to enhance at an international level the exchange of the latest research and professional practice information on performance-based earthquake engineering.
Methodology for Selection of Input Ground Motions for PBEE and Propagation of Uncertainty—3172002
C. Allin Cornell (Stanford/F), Fatemeh Jalayer (Stanford/GS), Jack Baker (Stanford/GS)
This project is designed to continue and bring to a level of completion the main issues of the Year 5 work statement: uncertainty propagation, IM sufficiency and efficiency investigations, and record selection/processing. The last two subjects are viewed, novelly, as being strongly inter-related.
Bridge Fragility and Post Earthquake Capacity—3182002
Bozidar Stojadinovic (UCB/F), Kevin Mackie (UCB/GS), Kyunghoo Lee (UCB/GS)
The goal of this project is to develop fragility functions for bridges to be used in PEER testbed projects. Fragility functions express the probability that a certain level of a decision variable related to bridge function is exceeded in a given seismic hazard environment. The objectives of the proposed project are:
- Define Decision Variable pertinent to bridge function state and repair time after an earthquake.
- Develop bridge fragility curves using bridge function Decision Variables for simple, yet common, bridge systems and sub-assemblies.
- Develop bridge post-earthquake aftershock (and traffic load, if time permits) fragility curves for collapse limit state.
Engineering Assessment Methodology—3192002
Helmut Krawinkler (Stanford/F), Ricardo Medina (Stan/GS), Luis Ibarra Olivas (Stan/GS), Farzin Zareian (Stan/GS), Christoph Adam (Stan/PD)
The objective is to develop quantitative information and simplified procedures that permit approximate performance assessment by means of commonly employed engineering analysis methods. Performance is expressed in terms of confidence levels and mean annual frequencies of exceedance of selected performance parameters (collapse, story drifts, inelastic deformations, and selected damage measures). The expected outcomes of the research are information and procedures that will assist the engineering profession in carrying out performance assessment with currently available tools and with tools that are under development by the research community.
Seismic Hazard Simulation of Bay Area Highway Network Analysis—3222002
James Moore (USC/F), Yue Yue Fan (USC/GS), Sungbin Cho (USC/GS), Qisheng Pan (USC/GS), Soojung Kim (USC/GS), Dongwhan An (USC/GS), Deepali Chausalkar (USC/GS)
The goals of the PEER Seismic Hazard Simulation of Bay Area Highway Network Transportation Analysis are to develop appropriate analytical and computational methods for evaluating the impact of a transportation system on an urban area and to illustrate the utility of these methods through an application to a region. In general, risk analysis of highway transportation systems is performed with the objective to provide:
- appropriate information in the retrofit and disaster mitigation decision process (in the pre-event and post-event period, it is necessary to determine which bridges are to be retrofitted/repaired/replaced, in what order and to what design level); and
- models and tools for estimating the socio-economic impact of transportation systems that have been damaged by an earthquake, and the benefits (losses foregone) of current and proposed retrofit and reconstruction programs affecting transportation structures.
- Linking models of network performance, transportation demand, bridge performance, and seismic hazard are the key to this effort.
Life Sciences Testbed Simulation—3242002
Khalid Mosalam (UCB/F), Tae-Hyung Lee (UCB/GS)
Develop a state-of-the-art computational model and perform nonlinear dynamic analysis of the UC-Berkeley Life Sciences building using the OpenSees simulation platform to demonstrate PEER performance-based earthquake engineering assessment and design methodologies. The project has dual objectives:
- Testbed for simulation in OpenSees using actual buildings, and
- Developing floor displacement and acceleration time histories to be utilized in testing building contents.
I-880 Testbed Simulation—3252002
Sashi Kunnath (UCD/F), Boris Jeremíc (UCD/F), Anna von Felten (UCD/GS), Keith Bauer (UCD/GS), Jinxiu Liao (UCD/GS), Feng Xiong (UCD/GS)
The primary objective of the project is to apply evolving PEER performance-based earthquake engineering methodology to evaluate the seismic response of a section of the I-880 viaduct. A major component of the methodology involves the estimation of engineering demand parameters (EDP) for a given hazard level which is quantified by means of an intensity measure (IM). An accurate representation of EDPs for the I-880 testbed requires the development of adequate and reliable simulation models of the target system. The development of an appropriate computer model incorporating all critical elements of the system including soil-foundation interaction is one of the goals of this project. Another goal of the project is to investigate sensitivity of material and modeling parameters in estimating EDP|IM. A related objective of the project is to provide input to the development and validation of OpenSees.
Coordinate PEER Methodology Testbed Research—3262002
Keith Porter (Caltech/F)
General coordination. Coordinate PEER methodology testbed research. Includes meetings, reports, online locus, methodological coordination, shepherding crosscutting topics, research planning, and promotion of BIP participation.
Meetings. Assist RC to arrange quarterly combined testbed meetings. Assist testbed managers to arrange mid-quarter testbed-specific meetings. Assist various researchers to arrange ad-hoc meetings of crosscutting-topic groups. Participate in RC and SAC meetings.
Reports. Assist testbed managers (Krawinkler, Comerio, Elgamal, & Kunnath) to coordinate whole-testbed project reports, which specify general methodology and illustrate with end-to-end analyses of individual testbeds.
Van Nuys Testbed Simulation—3272002
Laura Lowes (UW/F), Chaitanya Paspuleti (UW/GS), Nilanjan Mitra (UW/GS)
The primary objective of the proposed research effort is the development of state-of-the-art numerical modeling techniques for use in simulating the earthquake performance of older reinforced concrete buildings. The OpenSees analysis platform will be used as a basis for model development and the Nuys Testbed Building will be used as an example structure. The Year 6 research effort will building on a previously developed model of the Van Nuys building to:
- improve simulation of inelastic structural response,
- enable prediction of structural and non-structural damage and economic loss, and
- predict the impact of the FEMA 356 retrofit scheme on damage and loss.
Evaluation and Assessment of PBEE Methodology—3292002
Jon Heintz (Degenkolb/I), Robert Pekelnicky (I), Rose Katz (I)
This project is a continuation of Year 5 work. The objective is to provide an engineering practitioner’s assessment of the PEER PBEE methodology through a detailed comparison with current state-of-practice techniques. Year 5 focused on providing an independent evaluation of the expected performance of the building. Year 6 will focus on designing seismic rehabilitation for the Van Nuys testbed building, and comparing results with designs developed using the PEER PBEE methodology.
Practitioner Critique of PEER Bridge Analysis Methodology—3322002
William Nascimento (LAN/I), Mohan Char (LAN/I)
Review Assessment and Design Methodologies of Performance Based Earthquake Engineering developed by PEER with emphasis on practical design applicability.
Practitioner Critique of PEER Bridge Analysis Methodology— 3332002
Roy Imbsen (I)
Critique the newly developed PEER methodology for seismic design of bridges using a portion of the I-880 Caltrans Viaduct located in Oakland, California, i.e., I-880 Testbed.
Jack Moehle (UCB/F)
The goal is to enhance PEER research in geographically distributed networks by strategic planning and collaboration with other earthquake centers.
Advanced Seismic Assessment Guidelines—Lifelines 507
Allin Cornell (Stanford/F), Charles Menun (Stanford, F), Paolo Bazzurro (AIR/I), Maziar Matahari (Stanford/GS), Gee Liek Yeo (Stanford/GS), Joe Maffei (R&C/I)
The primary objective of this two-phase project is the development of a new level of guidelines for the assessment of existing buildings. The scope is limited to typical PG&E 1-3 story buildings often of older and mixed construction. The limit states considered are those of direct electrical-system-reliability interest, e.g., collapse and (red or yellow) tagging, the latter because of their operability implications. An advanced state-of-practice engineering is employed, e.g., the structural engineer will provide a nonlinear (NL) static pushover analysis (SPO). In keeping with sponsor-stated needs and recent SAC and PEER developments, the guidelines will incorporate both aleatory and epistemic uncertainty measures, and the guidelines’ output products will include limit-state “fragility curves”, i.e., curves of the probability of limit state given ground motion intensity (IM) level, that reflect these various uncertainties. The first-year objective has been a “beta-version” of these guidelines, using results of only the first year’s research and default methods and parameter values where necessary. Nonetheless this first-year version is “operational”, i.e., up to or beyond current practice in all respects, such that it is being tested by two top-level structural engineering firms in the second year.
Test Applications of Advanced Seismic Assessment Guidelines—Lifelines 508
Joe Maffei (R&C/I), Dayna Mohr (R&C/I)
Advanced seismic assessment guidelines were developed by Stanford University (C. Allin Cornell, Paolo Bazzurro, Charles Menun, Maziar Motahari) as part of the PEER Lifelines Program, Building Vulnerability Studies (Project Task Number 507). Predicting the post-earthquake functionality of utility structures is a crucial step in evaluating the likelihood of the electric distribution network being able to provide gas and electricity to its customers. The final product of the guidelines is a set of fragility curves for structural limit states directly related to post-earthquake building occupancy status, namely green, yellow, or red tagging.
Influence of Design Ground Motion Level on Highway Bridge Costs—Lifelines 6D01
Mark Ketchum (OPAC/I), Vivian Chang (OPAC/I), James Scheld (OPAC/I), Kwong Cheng (OPAC/I), Francis Drouillard (OPAC/I), Tom Shantz (Caltrans/I), Fadel Alemeddine (Caltrans/I)
The project proposes to quantify, in percentage terms, the cost impact of raising or lowering levels of design ground motion for new highway bridges. The nature of the cost curve may be influenced by many variables, including site-specific issues as well as bridge-type-specific issues. Its basic features, the nature of design constraints that define the cusps, and the relative economy of various bridge types at differing levels of design ground motions are immediately achievable objectives of this project. The project focuses on bridge types used for ramps, interchanges, and grade separations, which account for the majority of bridge construction costs in California.