A Non-Intrusive Bridge Weigh-in-Motion System for a Single Span Steel Girder Bridge Using Only Strain Measurements

This study proposes and demonstrates a non-intrusive Bridge Weigh-In-Motion (BWIM) methodology in a field study. This methodology is for a single span steel girder bridge that uses only strain measurements of the steel girders beneath the bridge deck to determine the weight and accompanying characteristics of trucks traveling over the bridge. A brief literature review of BWIM technology is presented, followed by a description of the proposed BWIM methodology. The proposed methodology determines gross vehicle weight, speed, axle spacing, and axle weight in an automated fashion using only strain measurements. A description is presented of the field study conducted to validate the proposed BWIM methodology. The field study used both a test truck and trucks from the traffic stream to calibrate and compare the accuracy of the proposed BWIM methodology with static measurements of weight and axle spacing collected at a weigh station located one-half mile past the bridge. The performance of the BWIM methodology is presented from a statistical perspective whereby the 95% confidence intervals are determined for the various errors in truck characteristic measurements. The field study was made possible through the collaborative efforts of the Connecticut Department of Transportation, the Connecticut State Police, and the Federal Highway Administration.