Design of instrumented bearings for direct measure of bridge live loads

A long span steel through truss was scheduled for expansion bearing replacement as part of an overall rehabilitation project. At the time, a Structural Health Monitoring (SHM) system was being designed to investigate how overloaded trucks were affecting the performance of the bridge. Due to the opportunity presented by the bearing replacement project, the concept of instrumenting the new bearings with load cells was accepted by the bridge owner and a formal design was commissioned. A prototype bearing was constructed and evaluated through rigorous testing in a laboratory setting to ensure that the addition of sensors in the load path of the bearings would not compromise the integrity or safety of the bridge. Upon completion of the acceptance testing of the prototype bearing, the full construction of the bearing assemblies and their subsequent installation was started. The paper discusses the various challenges associated with the design, construction, maintenance, and processing/interpretation of the measurements for such a system.