Applicability of Point Load Approximation to Traffic Load Estimation

Abstract

There is a growing demand to efficiently and accurately determine the axle weights of vehicles passing over bridges for the purpose of evaluating bridge health and for use in traffic control. The existing method for estimating axle weight, called BWIM (Bridge Weight-In-Motion), generally uses calibrated influence lines and strain signals in the calculation of the estimated axle weight. However, conventional methods require the acquisition of new influence lines and the use of strain gauges, which are costly to install. This study introduces the Point Load Approximation (PLA) to the BWIM method and investigates a new method of axle weight estimation using analytical influence lines and load effects other than strain. To verify the applicability of PLA, simulations in MATLAB and experiments on an undamaged model bridge were conducted. In the simulations, displacement and acceleration were used as measured data. The simulation results confirmed that the PLA theory can be used to estimate the axle weight using displacement and acceleration as load effects. The acceleration and displacement data were then obtained in a model bridge experiment. The experiments confirmed that BWIM with PLA provides better accuracy of axle weight estimation than existing methods. However, acceleration data resulted in less accuracy due to higher uncertainties in measurement than that of displacement.