Area 2Hazard Assessment and Geo-Performance
Ahmed Elgamal (UCSD), Thrust Leader
The hazard assessment and geo-performance research program is directed toward evaluation of the relationship between ground motion hazards, ground response/failure, and system performance. This thrust area includes elements of ground motion characterization, evaluation of free-field ground response, and evaluation of soil-foundation-structure interaction. The hazard assessment research will consider uncertainties and spatial/temporal variabilities in soil conditions, and their influence on performance. The hazard assessment research will provide direct input into the development of reliability-based global design methodologies, and into improved procedures for demand evaluation and loss estimation. Results of the hazard assessment research, particularly that dealing with evaluation of free-field response and soil-foundation-structure interaction is being implemented into the OpenSees analytical platform.
Studies of ground motions, site response, ground failure, and soil-foundation-structure interaction undertaken by others have not been oriented toward multi-level performance prediction, and have generally not included uncertainties and spatial/temporal variabilities. The explicit consideration of these factors is a distinguishing feature of PEERs Hazard Assessment thrust area.
3D Simulation of Seismic Ground Deformation in OpenSees—2202002
Ahmed Elgamal (UCSD/F), Zhaohui Yang (UCSD/PD), Jinchi Lu (UCSD/GS)
This project complements other ongoing efforts related to the open computational simulation platform OpenSees (led by Professor Greg Fenves). Specifically, the project is focused on: i) adding new geotechnical simulation capabilities, ii) calibration of these capabilities using available data sets, iii) advancing the spatial simulation capabilities, iv) integrating the Soil and Structural simulation components, v) exploring the seismic response of combined large-scale soil-structure systems, and vi) advancing the PEER Humboldt Bay Bridge Testbed efforts. Recent work has been addressing:
- Further development of the three-dimensional (3D) analysis capabilities for nonlinear soil-structure systems,
- Related Parallel-processing challenges (in collaboration with Prof. Kincho Law, Prof. Greg Fenves and the San Diego Supercomputing Center), and
- Computational developments related to spatial definition of ground motion (in collaboration with Prof. Jacobo Bielak and Prof. Joel Conte).
3D Soil Simulation Models in OpenSees—2212002
Boris Jeremíc (UCD/F), Zhaohui Yang (UCD/PD), Kevin Murakoshi (UCD/US), Qing Liu (UCD/GS), Feng Xiong (UCD/PD)
The goal of this project is to develop computational tools for seismic analysis of soil-foundation-structure interaction (SFSI). In particular, three dimensional elastic-plastic material models, integration algorithms and coupled formulations are in development and are being used to assess the effects SFSI has on Humboldt Bay Bridge. To this end, a number of elastic-plastic material models have been developed and implemented into OpenSees. Moreover, a fully coupled solid fluid formulation has been developed and implemented into OpenSees as well and is currently being validated.
Performance of Improved Ground—2222002
Nicholas Sitar (UCB/F), Elizabeth Hausler (UCB/PD), Gang Wang (UCB/GS)
This project was started in year 5 as a result of issues that arose during the seismic retrofit on the Berkeley Campus and it is aimed at developing a better understanding of the axial response of pier foundations under seismic loading. The traditional methods used for the evaluation of axial capacity of deep foundations under dynamic loading lead to extremely conservative and costly foundations. The conservativeness of the foundation design translates into increased demands on the structure itself and, hence, very costly structural systems. Test with direct evaluation of the dynamic axial response on the Berkeley Campus and at other sites in the S.F. Bay area showed a significant increase in the predicted axial stiffness and axial capacity of deep foundation elements over traditional design methods. As a result at Berkeley, the net savings to the Berkeley Campus were over $500K on one project alone. The objective of this research is twofold:
- to develop an numerical model for axial response of drilled piers; and
- to use the existing field test data and the results of numerical analyses to develop axial capacity and axial deformation relationships for different site conditions for use in PBEE.
Empirical Characterization of Basin Effects on Site Response—2252002
Jonathan Stewart (UCLA/F), Yoojong Choi (UCLA/GS), Robert Graves (I)
This Year 6 project is an extension of the Year 5 project having the same title. As described in the original project proposal, the general intent of this work is to develop a statistically robust engineering model for characterizing basin effects on ground motion intensity measures (IMs). The approach taken is to evaluate residuals between data and predictions, and correlate these residuals to basin geometric parameters. The predictions used to evaluate the residuals will, to the extent possible, remove the effects of site, path, and shallow ground response in an average sense, so that the deviations from data can be attributed to basin response.
Performance of Shallow Foundations—2262002
Bruce Kutter (UCD/F), Sivapalan Gajan (UCD/GS), Justin Phalen (UCD/GS), Peggy Walgenbach (UCD/O)
The nonlinearity of the soil and the interaction between the soil and foundation is shown to cause the building's stiffness and period to change to varying degrees. On the one hand, the nonlinearity of the soil may act as an energy dissipation mechanism, potentially reducing demands exerted on the structural components of the building. This associated nonlinearity, however, may result in permanent deformations (rotation or settlement) that cause damage to the building. The goal of this research is to further the understanding of soil-foundation-structure interaction with regards to seismic response.
Performance of Shallow Foundations—2272002
Geoffrey Martin (USC/F), Tara Hutchinson (UCI/F), Chad Harden (UCI/GS), Barbara Chang (UCI/GS)
The goals of PEER researchers (at UCD, USC, and UCI) studying the nonlinear behavior of shallow building foundations are to develop and test procedures to account for this nonlinearity in performance-based design. So far, it is established that soil yielding beneath foundations can be a very effective energy dissipation mechanism. However, foundation yielding may lead to excessive permanent deformations. The primary goal of the research at UCD (Kutter) is to produce archived test data at prototype stress levels. Collaborating researchers at UCI (Hutchinson) and USC (Martin) are using the experimental data provided by UCD and by other sources primarily for performing numerical analysis using OpenSees.
Soil-Foundation-Structure Interaction of Deep Foundations in Liquefied Ground—2312002
Ross Boulanger (UCD/F), Scott Brandenberg (UCD/GS), Dongdong Chang (UCD/GS)
The objectives of this project are to develop and validate nonlinear p-y, t-z, and q-z material models for OpenSees-based simulations of the seismic response of deep foundations in liquefied and laterally spreading ground.
Proposal to Investigate the Seismic Response of Short-Period Buildings—2332002
Christopher Rojahn (ATC/I), Jonathan Stewart (UCLA/F)
In October 2002, PEER awarded the Applied Technology Council (ATC) a contract to investigate the seismic response of short period buildings (ATC-55-1). The ATC-55-1 project is being conducted in support of a larger ATC project (ATC-55), “Evaluation and Improvement of Inelastic Analysis Procedures”, which is funded by the Federal Emergency Management Agency. The objectives of the larger ATC-55 project, which is being conducted in several phases over a two-to-three year period, are: (1) the development of practical recommendations for improved prediction of inelastic structural response of buildings to earthquakes (i.e., guidance for improved application of inelastic analysis procedures) and (2) the identification of important issues for future research.
Performance of Lifelines Subjected to Lateral Spreading—2342002
Scott Ashford (UCSD/F), Chia-Ming Uang (UCSD/F), Teerawut Juirnarongrit (UCSD/PD), Ben Siegel (UCSD/GS), Lisa Everingham (UCSD/US)
The overall project goal is to utilize the full-scale data assess current methods for estimating the effect of lateral spreading on pile foundations and pipelines, and develop new procedures if necessary. Specifically for Year 6, our objectives are to:
- Back calculate P-y curves for all specimens for both tests.
- Model Experiment 1 using OPENSEES.
Effects of Geotechnical Uncertainties on EDPs—2352002
Steve Kramer (UW/F), Pedro Arduino (UW/F), Sarah Paulsen (UW/GS)
The goal of the proposed project is to systematically investigate the effects of uncertainty in geotechnical parameters on uncertainty in engineering demand parameters (EDPs). The work will be accomplished in a hierarchical manner, beginning with relatively simple geotechnical models and site conditions and progressing to more complicated models and conditions. The EDPs will be simple, and selected to be consistent with those being used in PEER structural engineering investigations. The results will provide insights into the level of uncertainty inherent in ground motion predictions with the tools most commonly used in contemporary geotechnical engineering practice, and with more advanced tools developed by PEER.
Calibration of Basin Simulations—Lifelines 1A03
Steven Day (SDSU/F), Douglas Dreger (UCB/F), Shawn Larsen (LLNL/I), Kim Olsen (UCSB/O), Arben Pitarka (URS/I), Robert Graves (URS/I), Jacobo Bielak (CMU/F), Antonio Fernandez (CMU/GS)
The project will foster the integration of 3D ground motion simulation methods and results into engineering applications. We will validate 3D simulation methods and apply them to complex geological structures, with emphasis on urban sedimentary basins. This is a collaboration between the Pacific Earthquake Engineering (PEER) Center and the Southern California Earthquake Center (SCEC).
Physically Based Source Input for Strong Ground Motion Simulation—Lifelines 1C08
Greg Beroza (Stanford/F), Mariagiovanna Guatteri (Stan./PD), Seok Goo Song (Stanford/GS)
The goal of this project is to develop a library of rupture models for scenario earthquakes that are consistent with both the scaling and spatial variability of slip determined for past earthquakes and with simple notions of earthquake faulting physics.
Comparison of Ground Motion Characteristics Between Taiwan and California—Lifelines 1E07
Walter Silva (PE&A/I)
There are two objectives to this project:
- Process data from the 33 Chi-chi aftershocks and other relevant crustal earthquakes in Taiwan.
- Compare Taiwan response spectral shapes as well as source (stress drop), path (Q(f)), and site (kappa) properties with those of tectonically active regions (e.g. California).The goal is to produce a processed data set consisting of time histories and response spectra for inclusion in the PEER strong motion database and to assess the appropriateness of including Taiwan crustal earthquakes with California data for regression analyses.
Design Ground Motion Library—Lifelines 1F01
Maurice Power (Geomatrix/I), Robert Youngs (I), Faiz Makdisi (I), Donald Wells (I), Ronald Hamburger (I), Ronald Mayes (I), Roupen Donikian (I), Yusof Ghanaat (I), Walter Silva (I), Allin Cornell (Stanford/F), Paul Somerville (I), Stephen Mahin (UCB/F), Ignatius Po Lam (I)
The objective of this project is to develop a “Design Ground Motion Library” (DGML), which is a library of recorded acceleration time histories suitable for use by engineering practitioners for time history dynamic analysis of various facility types in the western United States, including buildings, bridges, utility structures, dams, base-isolated structures, and other common infrastructure facilities. The overall goal is to have a current and authoritative library of strong motion records endorsed by leading scientists and users within the professional seismological and engineering communities.
Parameterization of Non-Stationary Acceleration Time Histories —Lifelines 1G00
Paolo Bazzurro (AIR/I), Nicolas Luco (AIR/I), Norm Abrahamson (PG&E/I), Brian Chiou (Caltrans/I), Allin Cornell (Stanford/F), Joe Maffei (R&C/I), Maury Power (Geomatrix/I)
The project is structured into two phases:
Phase I: Investigate whether "non-stationary" characteristics of seismograms, in addition to more conventional ground motion intensity measures (e.g., spectral values), can improve the accuracy in the prediction of structural seismic performance.
Phase II: Three tasks:
- to provide the quantitative technical basis to establish the threshold limits beyond which earthquake record scaling introduces bias in the nonlinear response of structures (issue of particular interest to the PEER Lifelines Program's Design Ground Motion Library study).
- to provide the tools necessary for the synthetic time history validation criteria currently being developed by the PEER Lifelines Program (NGA Working Group #3). These criteria will consider the issue of nonlinear structural response.
- to provide a technical basis for some of the assumptions used in the PEER Lifelines Project 507 entitled "The Advanced Seismic Assessment Guidelines," which provided recommendations for "tagging" of buildings damaged by a mainshock and susceptible to an aftershock. These assumptions are also relevant to the follow-up applications PEER Lifelines Projects 508 and 509.
Next Generation Attenuation (NGA) Models, WUS Shallow Crustal Earthquake—Lifelines 1L01
Maurice Power (Geomatrix/I), Robert Youngs (I), I.M. Idriss (UCD/F), Kenneth Cambell (ABS/I), Yousef Bozorgnia (I)
The overall goal of project 1L Series is to develop Next-Generation Ground Motion Attenuation (NGA) Models for shallow crustal earthquakes in the western United States. Project Task No. 1L01 covers two components of the NGA project:
- project coordination – project coordinator Maurice Power; and
- participation of three of the teams developing NGA models – Robert Youngs and Brian Chiou (Task 1L01 provides support for Robert Youngs; Brian Chiou is directly supported
NGA Data Sets—Lifelines 1L02
Walter Silva (PE&A/I)
Configure the PEER Strong Motion Data Set for use in developing empirical attenuation relations.
Coordination of SMA Site Data from Taiwan: Phase I —Lifelines 2A02d
Robert Nigbor (USC/F), Ali Asghari (USC/GS), Jennifer Swift (USC/F), John Diehl (I), Rob Steller (I), Rong-Ruey Lee (I), Ming-Hung Chen (NCREE/O)
The objective of this project is to form a collaboration between PEER and NCREE regarding site characterization work at strong motion stations in Taiwan. Specific goals for this Phase 1 project are the execution of collaborative work at three strong-motion stations, the publication of these collaborative data, and the dissemination by NCREE of all of their site characterization data.
Application of SASW to US SMA Sites—Lifelines 2C01
Kenneth Stokoe II (UT/F), Brent Rosenblad (UT/PD), Hyung Park (UT/PD), Yin Cheng Lin (UT/GS), Jagrut Jathal (UT/GS)
The goal of this project is to evaluate shear wave velocity (Vs) profiles at approximately 15 sites in the Los Angeles, CA area using noninvasive, surface-wave seismic technology. The results of the Vs profiles will fulfill three purposes. First, at many sites, new information will be generated for PEER Lifelines Task 2G01 where profiles to depths in excess of 30 m would be beneficial. Second, some sites will be drilled and logged in the future under PEER Lifelines Task 2A01. The Vs profiles will be used in “blind” comparisons with subsequent profiles measured with the suspension logger. Third, some sites have “old” Vs profiles; that is, Vs measurements performed by other seismic test methods. The new Vs profiles will permit evaluation of the validity of the older data.
Supplement and Validation of Silva Theoretical Amplification Factors—Lifelines 2G01
Jonathan Stewart (UCLA/F), Annie Kwok (UCLA/GS)
The goals of this project are two-fold. First, we have extended the scope of the original 2G01 project to include the preparation of a final written project report documenting considerations associated with the selection of calibration sites and comparison of ground response predictions to other ground motion prediction techniques. Included in this report is discussion of a technique for the interpretation of ground response results suggested by Norman Abrahamson that involves the estimation of response spectra as the product of the input target spectrum and the median RRS (ratio of response spectra from ground response analysis). Second, we are validating Walt Silva’s surface-geology based amplification factors against strong motion data.