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.

This paper focuses on implementing existing bridge weigh-in-motion technology on railways. Using only simple instrumentation with four concrete embedded sensors, a complete WIM system with axle detection, weighing, track detection and attempted identification of locomotives was implemented on a bridge with multiple railway tracks. The results and the effectiveness of this type of sensor setup is discussed.

This paper describes Twim, a toolbox written in the MATLAB computer language. Twim is designed for monitoring bridge behaviour during train passages as well as for performing Bridge Weigh-In-Motion of railway traffic, both in real-time and offline. The algorithms calculate the static bogie loads and bogie distances, as well as the speed and acceleration of the train. Twim also includes visualization functions, automatic identification of known locomotives and an auto-calibration that uses locomotives with known bogie loads. The algorithms used place specific requirements on both the bridge type and the instrumentation of the bridge. These requirements are explained in the paper. The instrumentation of several bridges is described, and some of the interesting results gained through this instrumentation are presented.