Seismic Vulnerability of the Highway System

Task B1-1: Review of REDARS Seismic Risk Analysis Software

Subject Area:  Loss Estimation Methodologies
Research Year 2

Principal Investigator(s) and Institution(s)

Ronald T. Eguchi, ImageCat, Inc.


Under Task 106-E-7.3.1 of FHWA/MCEER Project DTHF61-92-C-00106, the methodology and beta version software for conducting a seismic risk assessment (SRA) of highway systems (currently called REDARS) was developed. Certain extensions are being considered to make the software more adaptable to decision making. Ultimately, the software will be used to improve the seismic design and construction of new facilities, the seismic retrofit of existing facilities, and the development of effective post-earthquake response and recovery strategies.

Prior to starting work on these extensions, however, it is desired to have the existing methodology and software independently reviewed, calibrated, and tested. The purpose of this task is therefore to perform an in-depth review of the current REDARS methodology and software. Specifically, the following objectives will be pursued in Year 2: a) test the usability of the program by implementing an example for a new study area, e.g., Los Angeles, b) identify key program modules and parameters by performing sensitivity studies, c) validate the methodology by comparing the results of REDARS to actual earthquake data, e.g., 1994 Northridge earthquake, and d) determine the usability of the results by working with an end-user panel or group.


During Year 2, the following subtasks will be performed:

  • SRA Review. The project team will complete its review of the SRA methodology. Particular attention will be given to those parameters and models that can be modified or replaced. Since one of the tasks this year deals with the sensitivity of results to changes in parameter values, it will be important to determine the extent to which these models can modified. 

  • Implementation of REDARS Code. During this phase of the project, we will install REDARS on our system for subsequent testing and evaluation. We understand that the Beta version of the program will be available for testing prior to July of 2000. We will implement several simple examples, as well as install the Memphis Case study. As part of this subtask, we will also test the completeness and understandability of the Users Manual.

  • Develop Input Data for Los Angeles Case Study. To implement REDARS for Los Angeles, we will compile data and information on local seismic hazards in the Los Angeles area (including soil data), bridge information (including bridge types, configurations, number of spans, etc.), highway network data, and traffic flow information. In Year 1, the project team collected damage and post-earthquake traffic information on the 1994 Northridge earthquake. These data will be used in the sensitivity and validation studies.

  • Conduct Sensitivity Studies. In Year 2, we will begin conducting sensitivity studies in order to identify key parameters and modules. The purpose of these sensitivity studies is to 1) identify the effect that parameter uncertainties have on the final loss estimation results, and 2) to identify possible simplifications in the methodology to facilitate more rapid calculations of loss or impact. In particular, we will focus on those simplifications that will help to improve the modeling of post-earthquake traffic patterns and levels. These sensitivity studies, which will focus on Los Angeles, will be combined with similar studies for Memphis (see task statement for B1-2).

  • Conduct Validation Studies using Data from the 1994 Northridge and 1987 Whittier Narrows Earthquakes. We will begin the validation process by developing the input required to run REDARS for two southern California earthquakes: 1994 Northridge and 1987 Whittier Narrows. The Northridge earthquake will test REDARS' ability to identify changes in post-earthquake traffic patterns after a major earthquake. The Whittier Narrows event will be important in ensuring the programs reliability for a smaller and less damaging event. This validation process will begin in Year 2 and will continue in Year 3.

  • Conduct Workshop focused on End-User Needs. At the beginning of Year 2, we will conduct an end-users workshop that will 1) introduce the SRA methodology and the REDARS software program, 2) examine addition performance measures, 3) identify ways in which loss estimation methods can be used for the design and construction of new facilities, the retrofit of existing facilities, and the development of more effective post-earthquake response and recovery strategies, and 4) identify a mechanism to involve end-users throughout this research project. The results from this workshop will help to define the requirements for a Decision-Guidance tool (see task statement for B1-2).


  • Technical report documenting the review of the SRA methodology.
  • Technical report documenting the results of the sensitivity studies.
  • Interim report on the validation studies.
  • Proceedings of the End-User workshop

Technical Challenges

Testing Beta version of the REDARS software program. Testing preliminary versions of any software program can often be problematic. To overcome this challenge and to ensure that this task stays on schedule will require extensive interaction between the software program developer, SSEC and the reviewer, ImageCat, Inc.


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