STRATEGIES FOR AXLE DETECTION IN BRIDGE WEIGH-IN-MOTION SYSTEMS

Abstract

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