Dynamic analysis of the effects of vehicle movement over bridges observed with CCTV images

This work describes a combination of image analysis techniques used to identify vehicles travelling on a bridge with a vectorised modal dynamic analysis that can handle efficiently a large number of wheel loads on the deck at each analysis step-time. In the absence of weight-in-motion data, a randomisation of the traffic flow is proposed to define the weight of the vehicles as a function of their identified size. The methodology is applied to real CCTV recording on a conventional road bridge with a large width-to-span ratio in which the deck is modelled with shell elements. The latter is found to be important to capture the significant contribution of local slab modes to the vibrations along the sidewalks. The dynamic analysis of a large number of traffic records indicate that code-based load cases with long truck convoys lead to unrealistically large contributions of high-order modes and to vibrations that are categorised as uncomfortable, whilst the more realistic traffic flows obtained from image analysis satisfy the comfort criteria based on root-mean-square accelerations.