Thrust Area III – Lifelines Component & System Hazards
The Lifelines Components and Systems research program is directed toward increasing the reliability and safety of geographically distributed lifelines systems including transportation and utility lifelines. The performance of a lifeline system is governed by three considerations: (1) the regional distribution of earthquake ground motion and ground failure, (2) the performance of individual components to ground shaking and ground failure, and (3) the interaction among the multiple components of the lifeline system and the impact of damage on flow through the lifeline system. The research program is designed to address these aspects within the confines of a limited set of lifelines systems determined by the external funding agencies. At present, the lifelines systems are restricted to highway networks and to electric and gas transmission and distribution systems. PEER is currently communicating with other major lifelines organizations to formulate new collaborative research programs. This will enable us to expand our lifelines funding agencies and research projects related to performance of lifelines components and systems.
The goals for the Lifelines Components and Systems research program are: (1) to improve the ability to estimate distributions of strong ground motion considering the range of earthquake mechanisms, earthquake magnitudes, path, distance, site and basin effects expected especially in California; (2) to improve the ability to estimate the extent of ground failures that may affect distributed and/or buried lifelines systems; (3) to develop practical analytical methods, including fragilities, for assessment of the performance of lifelines components, including electric utility equipment and buildings (bridge substructures and superstructures are excluded, as they are covered under TAII and other programs); and (4) to develop models for assessing system risk, and to use those models to understand where the greatest uncertainties and research benefits may lie, and to query risk-decision processes to better understand how to influence performance decisions about lifelines.
Strategic Plan and Milestones
The strategic planning graphic for TA III (Fig. 2.16) defines a coordinated sequence of research projects to address some of the goals described above. The plan, however, is not shown fully populated in future years in the same way as done for the other thrust areas because of the different funding sources. Unlike TA I, II, and IV, which are funded by the NSF and core matching funds, TA III is funded primarily by the Lifelines Program sponsors. Continuation proposals to those sponsors are pending, and it would not be appropriate to provide proposed details until funding decisions are made.
The research plan for Years 9–10 includes two main, multi-investigator projects on ground motions. The first of these will continue work to improve our ability to predict earthquake ground motion for design application through better attenuation relations. A series of projects referred to as “NGA-E” (“Next-Generation Attenuation — Empirical”) culminates a major coordinated effort to develop improved attenuation relations for horizontal ground motions based primarily on empirical ground motion data (1A03, 1L01–1L10b). NGA-E will continue to deal with issues of fault-normal and fault-parallel ground motions as well as attenuation of vertical ground motion. The next major phase, NGA-H, will involve a hybrid of empirical and simulation data. Additionally, the plan is to add new attenuation relationships for subduction earthquakes (relevant to northern California and the Pacific Northwest), vertical motions, and other “intensity measures” beyond elastic response spectra (e.g., duration, inelastic spectra, etc.).
The results should significantly improve estimates for near-field and basin conditions through incorporation of emerging major advances in earthquake simulation. It will also add a “fling- step” model that accounts for relative timing of static offset motions with vibratory shaking. The fling-step model will be used in the practical analysis and design of facilities located close to active faults.
The second set of projects on ground motions will be the selection and scaling of ground motion records for nonlinear analysis. A specific project in this category is the Design Ground Motion Library (DGML). The project aims to develop convenient, standard, and transparent methods for the selection and scaling of earthquake ground motion histories for use in nonlinear dynamic structural analysis. The design application of nonlinear analysis for lifeline structures is expected to increase in the next several years, especially for cases involving near-fault locations, unusual structural geometries, or special details including energy-dissipation devices. Current selection procedures have proven unreliable, demonstrating the need for improved standard procedures. While this activity is being driven by the lifelines applications in TA III, the work will be coordinated closely with the other thrust areas where the same product is needed. Recent communications with other lifelines organizations in California revealed that besides Caltrans, other agencies may also co-fund this set of practical research projects.
An additional project on seismic hazard will develop a fault rupture model to improve our ability other lifelines crossing fault zones. The new design tools are being designed to account for the distribution of offset as a function of distance from the mapped fault, and to account for variations in mapping uncertainty, the distribution of slip along the fault strike, the likelihood of secondary faulting, and the size of the facility footprint. This work will be an extension of ongoing work that has established the fundamental methodology, and will provide an initial design tool for strike-slip earthquakes. This next phase will add a new model for reverse faults and improve on the Phase-1 model for strike-slip faults by better accounting for recognized zones of rupture complexity (e.g., fault bends, step-over zones).
In the area of soil liquefaction and SSFI, work will continue to improve our ability to predict earthquake ground deformation caused by liquefaction and to develop improved methods for evaluating the SSFI impacts of liquefaction deformations on bridge foundations and abutments. Earlier work in TA III included significant advances in predicting liquefaction demands and better SSFI modeling of loads imposed by liquefied ground. The liquefaction-demands research has yielded a comprehensive suite of triggering assessment techniques, demonstrated the potential for regional deformation mapping, and initiated work on improved prediction of lateral spread displacements. Related SSFI modeling research has provided unprecedented experimental data sets from both full-scale field experiments and a range of centrifuges and shake tables to serve as new constraints on numerical models. In the next phase, SSFI research will focus on synthesizing the array of experimental findings, filling remaining data gaps, calibrating numerical models, and developing practical design guidelines. Liquefaction demands research will focus on completion of improved displacement estimation tools.
For electric and gas utilities buildings and components, additional work is anticipated with substation buildings and equipment, as well as in preparing practical guidelines for utilities. A new element in this topic is technology transfer to disseminate the research finding to a wider engineering community. A series of open workshops will be conducted, followed by drafting and distributing practical guidelines. Additional private research funding from PG&E and Bonneville Power Administration (BPA) are being added to TA III for future seismic testing and analysis of electric components.
For TA III a new source of funding has been San Francisco Bay Area Rapid Transit (BART). Recently PEER signed a new contract with BART to the study seismic response of partially embedded structures. This will include centrifuge tests and analyses. The project will be concluded in Year 10, and the possibility of a follow-up funding will be explored.
Critical Mass and Level of Effort
Since its inception, the lifelines portion of the program has involved researchers from both within and outside the Core Universities. In the case of the NGA projects, we have involved five of the leading attenuation relation developers; 1- and 3-D ground motion simulation experts from PEER, SCEC, and others; practicing engineering seismologists; and an international team of researchers providing data on ground motions and site conditions. In addition, the work has been guided by a series of two-day workshops involving typically 50–80 researchers and practitioners. Work on liquefaction and its effects on foundations has involved PEER researchers (e.g., Seed, Elgamal, Ashford, Boulanger) working in collaboration with international partners to leverage ongoing activities. Studies of earthquake-risk decision making will involve lifelines organizations and may be conducted by one of the researchers who has been active in another thrust area. Finally, work will continue to be conducted as part of the Tri-Center activity.
Research Advances and Deliverables
PEER has made important advances in previous research in this topical area. We have assembled the premier strong ground motion database, consistently processed with detailed information on site, distance, and rupture mechanisms, and have made it widely available to the community online. The PEER strong motion database has been considerably expanded. The updated strong motion database is being linked to the PEER Internet website, where users can search and download the processed ground motion records as well as extensive information compiled on the source, path, and site condition. Progress in improving ground motion simulation techniques has enabled us to begin to fill gaps, especially for large magnitude and small distance. The USGS is currently reviewing the available NGA models for adopting into the next U.S. National Hazard Maps. The Maps include basic data for various seismic deign codes, including the IBC. Additional models will be submitted to the USGS in the early summer of 2006. This work will support ongoing studies in other thrust areas, as well as earthquake engineering research and practice worldwide.
In the areas of ground failure we have gathered and made available extensive data sets from laboratory and field research, which is providing a basis for new triggering models, some of which have been produced through PEER research, and result in significant reduction in uncertainty. We have gathered important data on the interaction between piles and liquefied flowing soils that will serve as a basis for continuing development in Years 9–10.
Research on utility components has produced standards for testing as well as fragility relations for critical equipment, overturning models, and models for equipment interaction, all of which are widely used by utility companies in the western U.S. Work on utility buildings has led to new concepts on building tagging, effects of aftershocks, and building evaluation that are currently being tested by practicing engineers.
Deliverables for the next phase of research have been described in Section 2.5.2, and include new attenuation models, liquefaction triggering models, models for SSFI for foundations in liquefied soils, and improved models for electric utility components and systems.
The future plans for TA III follow directly from the strategic plan and milestones described in Section 2.5.2. Details of the funded projects will be determined by the level of funding and the decisions of the Joint Management Committee (JMC) working in collaboration with the PEER Research Committee. The PEER Lifelines Program research will continue beyond Year 10. For example, on July 2005, a new five-year contract was signed between PEER and the California Department of Transportation (Caltrans) for $2,250,000 funding. The new contract includes various topics ranging from ground motions to nonlinear site response to permanent ground deformations. In the near future, this contract will be likely amended to expand the level of funding and scope to include projects on nonlinear analyses of bridge structures. PEER is also signing a new contract with the California Energy Commission (CEC) to carry out a comprehensive technology transfer initiative for a wider engineering community, and a series of workshops and practical guidelines will be developed. PEER is also working on contractual details to get more funding from PG&E and Bonneville Power Administration (BPA) to study the fragility of components of electrical networks. This will provide an opportunity for PEER to collect more data and carry out tests for the fragility of nonstructural components. As of this time, the scopes of the next phase of long-term projects related to the performance of electric networks are still pending, as contractual negotiations are under way with the funding agency. It is anticipated that some of the future TA III studies will tie into the bridge, transportation, and Hayward fault scenario application study of TA II.
PEER Director Moehle and PEER Associate Director Bozorgnia are members of both the JMC and the PEER Research Committee. This ensures more coherent collaboration between TA III and the other thrust areas.
- Bozorgnia, Y., Hachem, M., and Campbell, K.W. 2006. Attenuation of inelastic and damage spectra. Proc. Eighth National Conference on Earthquake Engineering, San Francisco, CA, April 18–21.
- Campbell, K. W., and Bozorgnia, Y. 2006. Campbell-Bozorgnia next generation attenuation (NGA) relations for PGA, PEG, and spectral acceleration: A progress report. Proc. Eighth National Conference on Earthquake Engineering, San Francisco, CA, April 18–21.
- Chiou, B., Roblee, C., Abrahamson, N., and Power, M. 2004. The research program of next generation of ground-motion attenuation models. Geotechnical Special Publication No. 126, Geotechnical Engineering for Transportation Projects, Proc. Geo-Trans 2004, Los Angeles, CA, Geo-Institute of ASCE, V. 1, p. 768–77.
- Chiou, B., Power, M., Abrahamson, N., and Roblee, C. 2006. An overview of the project of next generation of ground motion attenuation models for shallow crustal earthquakes in active tectonic regions. Submitted for publication to Fifth National Seismic Conference on Bridges and Highways, September 18–20, San Francisco, California.
- Kwok, O. A., Stewart, J. P., Hashash, Y. M. A., Matasovic, M., Pyke, R., Wang, Z., and Yang, Z. 2006. Practical implementation of analysis routines for nonlinear seismic ground response analysis. Proc. 8th U.S. National Conference on Earthquake Engineering, April 18–22, San Francisco, CA, Paper 546. 8th U.S. National Conference on Earthquake Engineering, April 18– 22, San Francisco, CA,
- Power, M., Chiou, B., Abrahamson, N., and Roblee, C. 2006. The ‘next generation of ground motion attenuation models’ (NGA) project: An overview. Proc. Eighth National Conference on Earthquake Engineering, San Francisco, CA, April 18–21.
- Stewart, J. P., Goulet, C., Bazzurro, P., and Claassen, R. 2006. Implementation of 1D ground response analysis in probabilistic assessments of ground shaking potential, in GeoCongress 2006 —Geotechnical Engineering in the Information Technology Age, D.J. DeGroot, J.T. DeJong, J.D. Frost, and L.G. Baise (eds.), Atlanta, GA, Feb. 26–March 1, 6 pages (electronic file).
For additional details, see the PEER Annual Report - Volume 2 (PDF file - 7.6 MB).