Effect of five versus two axle moving trucks on structural dynamic performance of frame bridges

Recent advances in analysis, and design approaches led to a considerable reduction of the structural elements' size and weight. Heavy multi-axle trucks are now standardized in North America, and elsewhere, the traffic speed and the average number of trucks passing bridges have dramatically increased. For the purpose of the design and/or assessment of bridge structures, it is imperative to evaluate the static deformations, frequency, vibration amplitudes, and dynamic deformation patterns of new and aged bridges due to the new five-axle versus the old two-axle design trucks. This study investigated the effects of using a recent standard multi-axle design truck on the dynamic performance of a frame bridge. It presents a comparison of the bridge dynamic performance under 2-axle and 5-axle moving trucks. A two-dimensional nonlinear finite element model is used to model the frame, and trucks are modelled as a multi-degree of freedom dynamic system integrated with the bridge model. It is found that the model is able to capture the local dynamic excitation and oscillations results from the high variation of the stiffness and mass of the bridge components.