Load testing of bridges for load rating

Abstract

The AASHTO load rating method, which is the standard for determining the live load carrying capacity of bridges in the United States, is based primarily on the as-built material and section properties of a bridge. This supplemented with the ASSHTO load distribution factors, generally underestimates the “actual” load rating for bridges. Numerous field studies have shown that field test data provides an accurate representation of the actual bridge, and accurately predict the load rating of bridges. Field testing generally returns higher load ratings than what is predicted by the AASHTO method because it accounts for the actual load distribution, end fixity and stiffness of the structure. With advances in data acquisition and sensor technology, the use of diagnostic testing to evaluate bridge load ratings has become increasingly popular. This paper examines how current technologies are used, principally magnetic and reusable strain gauges and wireless data acquisition, to rapidly load test and improve the load rating of single span steel girder bridges.