Load Rating of a Fully Instrumented Bridge: Comparison of LRFR Approaches

Abstract

This paper presents a comparison of three methods used to load rate the Powder Mill Bridge based on the load and resistance factor rating (LRFR) approach. This is a typical three-span continuous bridge with steel girders in composite action with the RC bridge deck. The three methods are as follows: (1) employing the conventional design office load rating technique using a simplified line girder analysis, (2) using strain measurements from a diagnostic load test to adjust the design office rating to account for in-situ bridge behavior, and (3) using a finite-element (FE) model of the bridge, which accounts for three-dimensional (3D) structural system behavior. Advantages and disadvantages of each method are related to speed, ease of use, reviewability, cost, accuracy, and type of use intended. Similarities and differences in utilizing these three methods are discussed. The advanced load rating methods are shown to produce higher ratings in comparison with the conventional approach.