Modified Best-Selection Method for Bridge Live-Load Model Development

Abstract

Due to the expanding availability of high-fidelity weigh-in-motion (WIM) data in recent years, various local agencies have modified bridge design and rating procedures to best reflect state-specific traffic loads. However, accurate procedures for load model revision are often accompanied by high computational cost and implementation complexity. To address this concern, a reliability-based approach is proposed for vehicular live-load model development that involves selecting an actual vehicle configuration from the WIM database to serve as the basis for the load model. The approach first determined the required live-load factor for each potential vehicle configuration such that all considered structures would meet a minimum level of reliability. Next, the set of potential models was screened by imposing a limit on the level of design or rating conservatism allowed for any individual structure. Finally, an optimal load model was selected from the remaining set based on a penalty point approach that accounted for the deviation of results for any single structure as well as the overall deviation across all structures. Relative to an ideal reliability-based design optimization (RBDO) solution, the proposed method requires low computational cost, is straightforward to implement, results in a realistic vehicle configuration for the live-load model, and provides reasonable accuracy. The method was found to be slightly superior to the existing best-selection approach for large databases, but significantly better for small databases.