PBEE Procedures Report for Bridges and Benchmarking
Performance of RC Bridges - 2442005

Project goals and objectives

The goal of this project is to demonstrate how to use the PEER tools for probabilistic seismic performance assessment to highway overpass bridge structures. Such tools enable assessment of bridge performance in terms of the potential for bridge collapse in an earthquake, cost of repair of such a bridge after an earthquake, and the ability of the bridge to carry a given level of traffic load after an earthquake. The intended users of such tools are bridge engineers and highway system maintenance and emergency management professionals.

This project has two objectives. The first objective is to complete the benchmarking of the PEER PBEE procedure to the bridge test-bed developed in PEER project 2004209. This PBEE procedure was successfully applied up to the DM level. Repair cost data will be collected in order to extend the PBEE procedure to the DV level. The second objective is to complete the PBEE procedure report as it applies to bridges, and to provide support for other researchers working in the PEER bridge group on the test-bed bridge models to enable them to complete their portions of the PEER procedures report.

The intended users of the results of this study are: (1) PEER researchers working to enhance performance of bridges in geotechnical and structural engineering domains; and (2) Caltrans engineers who want to implement the PEER methodology in their design process.

Role of this project in supporting PEER's mission (vision)

This project is at the core of the Trust Area 2. An array of structural and geotechnical engineering projects aimed at enhancing the performance of bridges in earthquakes will use the test-bed baseline bridge models, developed and maintained in this project, to demonstrate the enhancements they develop.

This project will continue to serve as the liaison project to the MCEER and MAE center. The October 13 and 14, 2005 Tri-Center Bridge Workshop represents a formal result of the ongoing cooperation between the PEER, MAE and MCEER bridge researchers.

Furthermore, this project continues the ongoing cooperation with Caltrans. A PEER Lifelines project 9A01 has been initiated based on this cooperation.

Methodology employed

The fragility curves developed by the PIs in PEER projects 318, 539, 209 and 213 are used as input in the PEER integral to derive the result for the chosen testbed bridge.

Brief Description of previous year's achievements, with emphasis on accomplishments during last year (Year 8)

Results from work performed in Years 3 and 4 on project 312 "Seismic Demands for Performance-Based Design of Bridges", in Year 5 and 6 on project 318 "Bridge Fragility and Post-Earthquake Capacity", in Year 7 on project 538 "Performance Assessment of Highway Overpasses", and in Year 8 on project 209 "PEER Methodology Application to a Baseline Highway Overpass Bridge" is utilized in this project.

The principal results used from the Year 8 project is the prototype testbed bridge Type 11 (with long columns) and Type 1 (with short columns). The OpenSees models for these bridges have been developed in the modular fashion enabling other researchers to use them easily.

Reporting on project output will be conducted using a project reports, Trust Area meetings and a project web page. This web page will: 1. provide other PEER researchers with the updated status of this PEER projects; 2. enable exchange of data and software with other PEER researchers; and 3. provide the outreach to similar work conducted by the other two Earthquake Engineering Centers. In addition to this web page, conventional quarterly and annual repots will be prepared.

Other similar work being conducted within and outside PEER and how this project differs

A project on the development of a risk-based methodology for assessing seismic performance of highway systems (REDARS) is conducted by MCEER under the leadership of Dr. Stu Warner with TRB funding. The differences with respect to this project are: (1) the fragility curves developed in this project will be based on PEER probabilistic performance-based methodology and developed using sophisticated non-linear bridge computer models for the specific bridges considered, while the REDARS project uses simplified bridge models or empirical fragility curves; (2) REDARS project has a significantly wider aim, while this project is focused on rational evaluation of bridge post-earthquake operational state, repair time and cost, and aftershock collapse risk for specific baseline bridges.

The MAE center project on fragility assessment of bridges is lead by Prof. Reggie DesRoches. This project is similar, however the MAE project addresses the typical East Coast bridges. The MAE project has gone further in terms of assessing possible retrofit strategies and providing fragility curves for the retrofitted bridges. It has, also, a visual interface called MAE-VIZ developed by the MAE center. However, this project is ahead of the MAE project in terms of the complex soil-bridge modeling, consideration of soil-structure interaction and consideration of bridge repair cost and traffic capacity losses.

Describe any instances where you are aware that your results have been used in industry

Dr. Mark Ketchum of OPAC Inc. has been involved in the implementation of the damage and cost fragilities for this project. He has found PEER methodology quite interesting and on the way of adopting it in his own practice. Caltrans engineers are looking at this project to determine if they would consider adopting PEER methodology in their work.

Expected milestones & deliverables

The milestones for this project are:

1. Maintain the test-bed bridge OpenSees models developed in Year 8.
2. In cooperation with Bridge Trust Area researchers Professors Arduino and Kramer merge the bridge model with the soil model.
3. Conduct a probabilistic seismic demand analysis using the combined bridge-soil model for firm soil.
4. Conduct a probabilistic seismic demand analysis using the combined bridge-soil model for liquefiable soil.
5. In cooperation with Dr. Mark Ketchum develop a number of repair scenarios consistent with damage to the test-bed bridge at different levels of earthquake ground motion intensity.
6. In cooperation with Caltrans and independent estimators, conduct a survey to generate data on repair cost for the test-bed bridge repair scenarios.
7. In cooperation with PEER Buildings group develop an estimate of the remaining gravity load carrying capacity of the bridge based on the amount of residual displacement to generate data for an estimate of the remaining traffic load capacity of the test-bed bridge.
8. Use the IM-EDP models that include soil-structure effects, the EDP-DM models developed by Prof., Eberhardt, and the repair cost data to develop bridge repair cost fragility data.
9. Use the IM-EDP models that include soil-structure effects, the EDP-DM models developed by Prof., Eberhardt, and the repair cost data to develop bridge traffic capacity loss data.
10. Prepare fragility curves for traffic function loss models and DV-DM relations developed by other Trust Area 4 researchers.
11. Complete the report and the examples on the use of PEER PBEE methodology.

The deliverables of this project are:

1. Documentation on the combined soil-bridge model.
2. Bridge repair cost fragility curves.
3. Bridge traffic capacity loss curves.
4. Quarterly and annual repots.
5. Final project report.

The scope of the project is defined by its milestones listed below. The project time line is:

1. January 15, 2005: milestone 1, 2, and deliverable 1.
2. April 1, 2006 milestones 3, 4.
3. June 1, 2006 milestones 5, 6, 7.
4. September 1, 2006 milestone 8,9,10, and deliverable 2 and 3.
5. October 1, 2006 milestones 11 and deliverable 4.

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