Investigation of multi-lane factor models for bridge traffic load effects using multiple lane traffic data

Abstract

Multi-lane factor (MLF) is a crucial component of the traffic load model in design specifications for bridges. Due to the significant changes in highway freight transportation over the past two decades, it is urgent to propose precise MLFs for bridge assessment under onerous traffic loading. This study reviews the underpinning approaches of existing MLF models and uses numerical examples and site-specific weigh-in-motion data to investigate the performance of these approaches. First of all, three MLF underpinning approaches described in the literature, i.e., the multi-presence truck weights approach, the multi-presence truck load effects approach, and the coincident lane load effects approach, are illustrated and discussed. Then, numerical examples of multi-lane bridge traffic load effects without lane load disparity are used to compare the MLFs calibrated by the three approaches. Finally, realistic weigh-in-motion data that have a strong lane load disparity are employed to calibrate MLFs by these approaches, and the MLFs are compared with those in bridge design codes. Results show that the three approaches have large deviations on MLFs calculation based on the same traffic data and studied bridges. In general, the coincident lane load effects approach is flexible for MLF calibration of traffic data with and without lane load disparity. However, its calculation procedure is relatively complicated, especially when the number of traffic lanes is large. The multi-presence truck load effects approach gives comparable results of traffic data without lane load disparity but overestimates MLFs when there is lane disparity of traffic loads over multiple lanes. The multi-presence truck weights approach needs to be improved for traffic data with and without lane load disparity otherwise generates large deviations. The selection and improvement of the three approaches are further discussed. This work highlights the importance of MLF approaches to consider the lane disparity of traffic loads over multiple lanes in practical engineering.