A general solution to the identification of moving vehicle forces on a bridge

Bridge Weigh-In-Motion systems measure bridge strain caused by the passing of a truck
to estimate static axle weights. For this calculation, they commonly use a static
algorithm that takes the bridge influence line as reference. Such a technique relies on
adequate filtering to remove bridge dynamics and noise. However, filtering can lead to
the loss of a significant component of the underlying signal in bridges where the
vibration does not have time to complete sufficient number of cycles, and in cases of
closely spaced axles traveling at high vehicle speeds. In order to overcome these
limitations and also to provide additional information on the dynamics of the applied
forces, this paper presents an algorithm based on first order Tikhonov regularization and dynamic programming. First, strain measurements are simulated using an elaborate 3-D vehicle and orthotropic bridge interaction system. Then, strain is contaminated with noise and input into the moving force identification algorithm. The procedure to implement the algorithm and to derive the applied forces from the simulated strain record is described. Vehicle axle forces are shown to be accurately predicted for smooth and rough road profiles and a range of speeds.