ABSTRACT
When traffic flow pass through the bridge, the peak of vehicle loads often occur at the same damaged locations of bridge surface. At these local locations, the maximum dynamic load of each traffic vehicle influence to bridge dynamic response. This paper presents a numerical method to evaluate the dynamic impact factor of existing bridges considering effect of all vehicles in traffic flow and local roughness condition. At first, data acquisition and traffic monitoring are conducted to extract the traffic patterns influencing on bridge dynamic responses. At the same time, International Roughness Index (IRI) values at every 1-meter length are measured by a laser profiler to assess the local roughness irregularity of the target bridge. From monitoring traffic data, traffic flow with random vehicle passing order is constructed as the time-history of transient time force functions. The fluctuated level of traffic load function assigned at each discretized deck node of bridge FE model represents for the local roughness damage position along bridge length. The numerical result was verified by applying it to a target existing bridge using the measured dynamic monitoring data, traffic data, roughness surface, and the finite element model on bridge. Dynamic effect of traffic and local damage on existing bridges is derived as the ratio between RMS acceleration of bridge deck under local surface damage and good surface condition. From this ratio, the dynamic impact factor of traffic and current local damages is calculated which could be applied for bridge load rating and evaluation.
