Response and Analysis of Steel Trusses for Fatigue Truck Loading

Abstract

The strain responses of several members of two different types of truss bridges to known truck loads are measured and compared to the responses calculated using typical structural analysis as well as 2D and 3D finite-element analysis. The simple calculations result in calculated stress ranges that significantly exceed the measured stress ranges in most cases, for many reasons including (1) flexural moments are carried by the deck; (2) trusses act in a way that is partially composite; (3) simple angle end corrections of floor beams act partially restrained; and (4) steel bearings on older large trusses typically do not respond to live loads like rollers. Typical ratios of the measured stresses to calculated stresses are developed for different parts of the superstructure if there is still a significant discrepancy after making reasonable refinements in the assumptions and analysis.