Development of Traffic Live-Load Models for Bridge Superstructure Rating with RBDO and Best Selection Approach

Abstract

Reliability-based design optimization (RBDO) is frequently used to determine optimal structural geometry and material characteristics that can best meet performance goals while considering uncertainties. In this study, the effectiveness of RBDO to develop a load rating model for a set of bridge structures was explored, as well as the use of an alternate best selection procedure that requires substantially less computational effort. The specific problem investigated was the development of a vehicular load model for use in bridge rating, where the objective of the optimization is to minimize the variation in reliability index across different girder types and bridge geometries. Moment and shear limit states were considered, where girder resistance and load random variables were included in the reliability analysis. It was found that the proposed best selection approach could be used to develop a rating model nearly as effective as an ideal RBDO solution but with significantly less computational effort. Both approaches significantly reduced the range and coefficient of variation of the reliability index among the bridge cases considered.