Seismic evaluation of highway bridges phase I: Screening for seismic retrofit
Abstract
A seismic screening system for highway bridges in Indiana is presented. The system is named SSIB (Seismic Screening of Indiana Bridges). SSIB is a rational and practical procedure for screening, assessing seismic vulnerability and prioritizing Indiana bridges for seismic retrofit. SSIB is an integrated interactive software package comprised of the following programs: SHAKE to account for soil conditions; DRAIN-2DX for nonlinear time history analysis of bridge structure; Microsoft Access, a database software for bridge database management; Quattro Pro; and Fortran computational routines. Seismic screening by SSIB is based on nonlinear time-history analysis of bridge structural models using simulated or actual earthquake records. SSIB computes the maximum dynamic structural responses that dictate the critical modes of failure and include longitudinal horizontal displacement of superstructure, maximum bending moment, maximum axial force and maximum shear force for both the superstructure and substructure. The critical elements for each response in both the superstructure and substructure are identified. Soil conditions and substructure behavior are taken into account in determining maximum responses. SSIB determines the level of seismic risk of a bridge structure based on fuzzy logic. The seismic risk prediction module called FUZZRISK that is incorporated into SSIB, uses the demand capacity ratio of each seismic demand that includes horizontal longitudinal displacement, axial force and bending moment, to determine the seismic risk rating of each individual seismic demand. Representing seismic risk rating of each seismic demand and the corresponding established degree of importance as fuzzy numbers, a fuzzy weighted average is computed which is reduced to a numerical scale also known as the priority or ranking index. Bridges are then designated into the category of high, moderate, or low seismic risk. In the event some bridges fall in the categories of moderate and high risk, then the priority index is used to rank the bridges for seismic retrofit. Application of fuzzy logic or generally the theory of fuzzy sets, is the best way to systematically handle information that is subjective like assessment of seismic risk prediction for highway bridges. The purpose of SSIB is to articulate a more complete and informative seismic vulnerability assessment of highway bridges and will facilitate better seismic retrofitting decisions.
Degree
Ph.D.
Advisors
Pan, Purdue University.
Subject Area
Civil engineering
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