Effects of Operational Traffic Variability on iSHM

Detectability of damage-sensitive signal features in Structural Health Monitoring (SHM) of bridges is confounded by operational and environmental factors, including variation in traffic conditions. Vehicles act as moving force exciters and also represent moving additional masses. Studies of vehicle-bridge interaction suggest that complex behaviour can result from simple bridge structures interacting with small numbers of vehicles. Indirect SHM (iSHM), a paradigm in which vehicles are used as sensor carriers, introduces additional challenges regarding spatial and temporal data sparsity. However, as the bridge span and traffic volume increase, dynamic coupling between the bridge and each individual vehicle reduces, suggesting a possible optimum condition for iSHM in which available data quantity is increased and the influence of individual vehicle behaviour is reduced. This paper presents a study of bridge damage detection using data from moving vehicle responses, generated by Finite Element simulation. Varying traffic conditions are represented by statistical characterisation of force inputs and additional masses to the bridge deck. The effect of spatial-temporal availability of monitoring data on detectability of damage is investigated by synthesising the responses of a range of different combinations of sensor-carrying vehicles. The efficacy of vehicle-borne and bridge-mounted sensors for damage detection is compared.