Reliability assessment of steel-free deck system bridges

Steel-free concrete bridge deck system is a relatively new approach to bridge design and construction. The main modes of local failures for the system are punching failure of the deck due to concrete crushing, and yielding of the restrain straps. Cracking of concrete due to regular live loads or other natural phenomena does not have considerable influence on the failure modes of the system. The current assessment technique in bridge management systems is mainly assigning a rate to the system components based on detected cracks and steel bar corrosions, which is not applicable to steel-free deck systems. Here the condition assessment of such a bridge, namely the Crowchild bridge located in Calgary has been performed using a reliability approach. The finite element model of the bridge has been developed and verified using SAP2000 software. Dynamic tests conducted by other researchers show that the natural frequencies of the bridge changed with time. Such changes may be related to environmental effect (e.g. temperature) or changes in support conditions. In the finite element simulation, the properties of the elastic bearings have been changed to reflect various scenarios including jamming. Using Monte Carlo simulation technique, the reliability index β and probability of failure of the system have been determined for different times. The results show that the system is quite over-performing and there is a low probability of failure in the next 75 years for such system.