A New Method for Calculating Bridge Influence Surface

Bridge influence surface (BIS), which reflects the relationship between the bridge response and the unit load moving on the bridge, has been commonly used in bridge weigh-in-motion, bridge damage detection, etc. Generally, the BIS can be obtained by interpolating bridge influence lines (BILs) at different lateral positions. In field tests, the BILs are usually extracted from the bridge response induced by a moving calibration vehicle with known axle loads. However, when taking the axle loads of the calibration vehicle into calculation, the impacts of the transverse distance between coaxial wheels and the unbalance of the coaxial wheel loads are ignored. Hence, errors may be brought to the calculated BIL and then propagated to the BIS. To remove these impacts, a new BIS calculation method, which takes the load of each wheel rather than each axle into calculation, is proposed in this research. Numerical simulation shows that the BIS can be successfully estimated by this method.