Monitoring traffic loads and dynamic effects using an instrumented railway bridge

This paper presents a cost-effective method for the assessment of actual traffic loads on an instrumented bridge. The instrumentation of a newly constructed integral-type railway bridge in Stockholm (Sweden) is described. A complete “Bridge Weigh-in-Motion” (B-WIM) system, with axle detection and accurate axle-load evaluation, was implemented using only four concrete embedded strain transducers. A temporary accelerometer was attached to the edge beam of the bridge to evaluate the eigenfrequencies, predict possible wheel/rail defects, and check whether the acceleration limit value for ballast instability (as given in railway bridge design codes) is exceeded. The main objective of the monitoring project has been to increase the knowledge of actual traffic loads and their effect on railway bridges, through both measurements and numerical simulations. Some very early but representative results are presented, and the efficiency of the algorithms and usefulness of the monitoring program highlighted.