Abstract
This paper summarises observations and results obtained from diagnostic testing and a complementary finite element model of a 140-year old short-span open-deck metallic girder bridge. A purpose-built frame was constructed around the bridge in order to apply the load in a form that represents passenger train axle loading. Testing was carried out under different axle load positions on the bridge with and without the timber deck superstructure to quantify load distribution effects on the supporting bridge members. Minor asymmetries, due to the location of offset stiffeners on main girder webs, and imperfections in the timber deck, in the form of unintended camber in the solid beams, played a significant role in the recorded bridge response, manifested through U-frame action deformation profiles and cross-girder bending stresses. Prompted by these test observations and using appropriate finite element models, a novel numerical sensitivity study was undertaken to quantify, for the first time, the effect of these factors on fatigue damage for a typical train passage. It is demonstrated that the synergistic application of load testing and numerical modelling can add value to our understanding of bridge response and inform issues related to static and fatigue assessments leading to more reliable service life predictions.