Abstract
To perform effectively, a Bridge Weigh-in-Motion (B-WIM) system requires accurate information on the location and speed of all axles on the bridge. In recent years, axle detection is by sensors under the bridge – so called Free-of-Axle-Detector or Nothing-On-Road (NOR) B-WIM. As axles pass over an axle detecting strain sensor, there is a peak in strain which can be detected by the data acquisition system. This approach works well for some bridges but there are challenges for beam-and-slab bridges where the beams are deep, a common form of construction in Alabama. The slabs in such bridges are therefore generally used for axle detection but the peaks in the slab strains are quite sensitive to the transverse position of the wheels over the beam. This paper describes a study into axle detection which tests alternative strategies for a range of bridge types and spans.