Health Assessment of a Plate Girder Railway Bridge under Increased Axle Loads

Abstract

Most bridges are aging and do not have complete design information. Hence, field testing for the evaluation of the structural performance and health of bridges is becoming essential, but even sophisticated modern structural analysis techniques cannot replace field testing, especially in the case of determining the live-load performance of bridges. Furthermore, field data can be used to calibrate and fine-tune an analytical model to match the behavior observed in the field. In this paper, details of full-scale field testing and performance-evaluation studies carried out on a typical steel plate girder railway bridge under increased axle loads are presented. One of the primary objectives of the study is to evaluate the longitudinal force caused by the increased axle loads of freight wagons. The bridge superstructure is extensively instrumented to measure the responses under various static and dynamic tests carried out using the test train formation with increased axle loading. The strategies adopted for evaluating structural response parameters are discussed. In addition, dispersion of the longitudinal force from the rail to the superstructure is evaluated using an innovative fixture together with the appropriate instrumentation scheme. It is found that around 50% of the longitudinal force generated at the rail level is transferred to the bridge substructure of the instrumented span. Using the load spectra adopted in the current study, the remaining fatigue life of the bridge is also evaluated using different damage models and is estimated to be around 150 years. The methodologies developed and implemented for the health assessment of plate girder bridges would pave the way for undertaking timely maintenance.