Identifying damage on a bridge using rotation-based Bridge Weigh-In-Motion

Abstract

Bridge Weigh-in-Motion (B-WIM) systems use the bridge response under a traversing vehicle to estimate its axle weights. The information obtained from B-WIM systems has been used for a wide range of applications such as pre-selection for weight enforcement, traffic management/planning and for bridge and pavement design. However, it is less often used for bridge condition assessment purposes which is the main focus of this study. This paper presents a bridge damage detection concept using information provided by B-WIM systems. However, conventional B-WIM systems use strain measurements which are not sensitive to local damage. In this paper the authors present a B-WIM formulation that uses rotation measurements obtained at the bridge supports. There is a linear relationship between support rotation and axle weight and, unlike strain, rotation is sensitive to damage anywhere in the bridge. Initially, the sensitivity of rotation to damage is investigated using a hypothetical simply supported bridge model. Having seen that rotation is damage-sensitive, the influence of bridge damage on weight predictions is analysed. It is shown that if damage occurs, a rotation-based B-WIM system will continuously overestimate the weight of traversing vehicles. Finally, the statistical repeatability of ambient traffic is studied using real traffic data obtained from a Weigh-in-Motion site in the U.S. under the Federal Highway Administration’s Long-Term Pavement Performance programme and a damage indicator is proposed as the change in the mean weights of ambient traffic data. To test the robustness of the proposed damage detection methodology numerical analysis are carried out on a simply supported bridge model and results are presented within the scope of this study.

A direct method to detect and localise damage using longitudinal data of ends-of-span rotations under live traffic loading

“…Alamdari et al [2] proposed a similar technique but used rotation influence lines obtained indirectly via strain measurements as opposed to directly measuring rotation. O'Brien et al [18] presented a damage detection approach based on the overestimation of vehicle weights by a rotation-based BWIM system following damage. The work in [28,34], proposes an approach which uses rotation measurements in combination with strain measurements and a baseline FE model of the bridge to detect damage.…”

“…Existing work can be broadly categorised as rotation-based bridge weigh-in-motion (BWIM), and rotation influence line approaches. Rotation-based BWIM approaches [18] seek to detect and potentially localise damage by tracking the change in the statistical distribution of the calculated vehicle weights. Rotation influence line-based approaches [2,10] typically utilise load testing with vehicles of known weights, which when repeated over a long period of time can highlight damage in the structure.…”

“…Both approaches are based on a two step process, specifically: (1) A bridge closure to carry out load testing using a vehicle of known axle weights and spacings to calculate the rotation influence line. (2) For the WIM approach [18], an axle detection system needs to be permanently installed on the bridge and a complex optimisation procedure used to calculate the vehicle weights. For the influence line approaches [2,10], the approach carried in (1) needs to be carried out in similar environmental conditions, although this is not highlighted in [2,10].…”

“…Both approaches have major limitations from a practical engineering perspective either due to road closures or the need to perform measurements with the same environmental conditions. The underlying principle [2,10,18] is that if damage occurs in the structure, the rotation response to a given load will increase. This work proposes a novel direct method for damage detection which performs analysis directly on measured rotation signal data.…”

A Novel Acceleration-Based Moving Force Identification Algorithm to Detect Global Bridge Damage

“…While A-MFI may not determine the weight of a particular vehicle accurately, the results are consistent. It is well known that the mean weight for vehicles of a given class, is highly repeatable at a given site (see, e.g., [47]). Hence, if the calculated mean GVW at a site increases, it suggests a loss of stiffness, i.e., damage, in the bridge.…”