ABSTRACT
This paper summarizes results obtained from the field testing of an open deck plate-girder riveted metallic bridge removed from service in the UK and load-tested under controlled conditions. A purpose-built loading frame was constructed around the bridge for the application of the loading, which was applied in a form that represents typical passenger train axle loading; this included single and pairs of 10-ton axle loads. Testing was carried out under different axle load positions on the bridge with and without the timber deck to quantify load distribution effects on the bridge components. The response was measured via approximately 40 displacement transducers and 30 strain gauges. It was concluded that the presence of timber beams is significant both in terms of the maximum strains reached under a typical train axle load, as well as in terms of the load experienced by adjacent elements when the axle is directly over a specific cross-girder. Moreover, the effect of irregularities in the solid timber beams, e.g. in the form of unintended camber, can play a significant role in the recorded response. Minor geometric asymmetries, e.g. the location of transverse offset stiffeners on the two main girders, can introduce noticeable effects on the U-frame action, whose quantification is an important factor in bridge assessment guidelines. These observations will be utilized in updating adjustment factors for simplified fatigue assessments based on stress ranges estimated from idealized train passages over the bridge.
