NEW PROCEDURE FOR FATIGUE DESIGN OF HIGHWAY BRIDGE GIRDERS

The wide variety of heavy truck traffic and bridge girder weld conditions combined with reported low measured stress levels under random traffic suggests there must currently be inconsistent safety margins against bridge fatigue. This paper discusses a probabilistic load model that forecasts histograms of highway bridge loading and that can be used to predict fatigue life and to properly size girder sections. A reliability of risk approach to choosing safety factors on material and load is also described. The simplified design procedure based on the truck loading model permits cross sections to be designed or checked against fatigue by a simple formula that also includes as parameters truck volume, span length, weld category, and location.