Comparison of load rating techniques for the Red Deer River Bridge

A reliability-based structural evaluation for the Red Deer River Bridge was conducted based on collected strain gauge data and compared to theoretical results using the conventional methods outlined in CAN/CSA-S6-06. Live load capacities for flexure were calculated in accordance with both the load and resistance factor and mean load code-based methods, suggesting that the bridge is adequate for the proposed increased live load level. The structural evaluation based upon the results of the field measurements, though, indicated reliability indices for flexure that exceeded those calculated based on code methods for all but the one instrumented location; furthermore, anomalously high strain readings at this one apparently deficient location cast doubt on the measured result. The transverse distribution of live loads varied considerably along the instrumented span and indicated that the bridge diaphragms are not fully effective. Measured dynamic effects were lower than those prescribed by CAN/CSA-S6-06.