PROBABILISTIC APPROACHES TO THE DESIGN OF STEEL BRIDGES

This paper demonstrates how a relatively simple first-order probabilistic method can be used to assess the reliability of the 1977 AASHTO specification for the design of steel bridges and how a consistent load-and resistance-factor design specification can be developed for steel bridge structures. It is shown that the AASHTO load-factor design method, as characterized by the safety index, is consistently reliable but that the reliability of the allowable-stress design method varies considerably. The paper also outlines the steps needed to generate a probability-based bridge design code and lists the available statistical data for steel members and connectors. The conclusions are that existing theory and data will allow development of a probabilistic design specification for steel bridges and that the format of such a specification does not differ greatly from the AASHTO load-factor design method. /Author/