Evaluation of dynamic responses of bridges considering traffic flow and surface roughness

Abstract

The variations in the vehicle types, speeds, and passing order in the traffic flow and roughness conditions cause the dynamic effects of live loads on the bridges. In this study, a numerical calculation scheme is proposed to evaluate the bridge dynamic response under random traffic flow, considering the surface roughness condition. Traffic vehicles with a random passing order are constructed as the time history of the transient force functions assigned at each discretised deck node of the numerical model. The random effects of the vehicle types, speeds, and surface roughness are represented by the amplitude levels of the transient force functions. The validity of the calculation scheme is verified by applying it to an existing steel box-girder bridge using dynamic monitoring data, traffic data, and a finite element model. The behaviour of the calculated root mean square (RMS) of the accelerations agrees with that of the measurement data, particularly in the traffic situation with a high truck ratio. Moreover, a parametric study is conducted to investigate the effects of the traffic flow characteristics and surface roughness conditions on the bridge dynamic responses. The results demonstrate that the RMS of acceleration depends on the truck ratio and traffic flow speed; however, the maximum acceleration may be influenced by the vehicle speed and passing order, as well as the surface roughness condition. It is concluded that the calculation scheme is applicable for evaluating the dynamic responses of existing bridges with the given dynamic monitoring data, traffic flow, and surface roughness conditions.