Overlooked Secondary Effects in Open-Deck Truss Bridges

Deformation-induced fatigue cracking has been a common source of fatiguedamage in steel bridges. These damage cases are often the result of secondaryrestraint forces generated by an unintended or overlooked interaction betweendifferent members in the bridge.A number of these interaction mechanisms areexamined in this paper using finite element analysis of a case-study bridge. Fieldmeasurements performed on the bridge were used to validate the analysis. Theresults of the analysis indicate that the effects of secondary forces, which developin different members of the floor system of riveted truss bridges, are generallynot negligible. In particular, the connections between different orthogonal membersof the floor system, such as stringer-to-floor-beam and floor-beam-to-chordconnections, might be critical with respect to fatigue due to these effects