Seismic Vulnerability of the Highway System

Task B1-1: Review of ROAD-1 Seismic Risk Analysis Software
Subject Area: Loss Estimation Methodologies

Principal Investigator(s) and Institution(s)
Ronald T. Eguchi, Center for Advanced Planning and Research, EQE International 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 ROAD-1) was developed. As a follow-on to that work, this project will extend the SRA methodology and software, and incorporate formal loss estimation methodologies, so that it can be used for predicting not only impacts to traffic flows around a region, but also the direct and indirect costs resulting from earthquake-related damage to the highway system.

Prior to starting work on the loss estimation 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 ROAD-1 methodology and software. Specifically, the following objectives will be pursued in Year 1 of this two-year task: (1) review the basic methodology behind the seismic hazard, bridge fragility, traffic flow, and loss modeling; (2) review the methodology used to generate the sequence of earthquake events used in the probabilistic analysis of loss and effects; (3) review the software integration plan for merging the different program modules; (4) develop a work plan for performing a demonstration study in Los Angeles; and (5) prepare an outline for an "end-users" workshop.

Currently, ROAD-1 analyzes the probability of experiencing various levels of reduced traffic capacity based on a sequence of earthquake events for a region. Hazard levels are based on ground shaking and liquefaction effects; at this point, only highway structures are addressed. The methodology has been applied in a demonstration to the Memphis, Tennessee region. Current efforts are focused on producing a user-friendly software package that automates these calculations for the Memphis region.

While each of the individual models has undergone some level of scrutiny, the overall methodology has yet to be evaluated and tested. An independent review will be conducted before the software code is released to the general engineering community. Some of the factors that should be considered in this review include: (1) are the loss or damage measures comprehensive enough for most earthquake transportation planning studies? (2) are the models transferable to other regions of the country? (3) how do the results from this methodology compare with actual earthquake losses or experience? (4) is the software reasonably easy to use and are the instructions for creating and inputting data clear? and (5) are the results easy to interpret?

The approach to this task will be to: (1) review each of the existing models in ROAD-1, comparing the details of the current models to other existing models or methodologies; (2) examine the results from the Memphis study, with the focus here on examining the types of output produced by the current methodology; (3) assess where the methodology should be extended or expanded in order to produce the desired outputs (it should be noted that an assessment of user needs will be critical here); (4) recommend areas of improvement or modification; and (5) begin preparing for a demonstration study in Los Angeles.
Actual validation of the methodology and software will take place in Year 2 with Los Angeles being the demonstration city. Several case studies will also be performed: (a) repeat of the 1987 Whittier Narrows earthquake; (b) repeat of the 1994 Northridge earthquake; and (c) a future catastrophic earthquake (M7 or higher) in the Los Angeles basin.

Throughout this process, the developer of ROAD-1 will provide assistance, under related project Task B1-2.

Anticipated Start Date and Duration
January 1, 1999 - 24 months