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.
Highlights
While the bridge stock around the world is ageing, freight transport is growing and the demand on transport infrastructure is increasing
The results showed that the rotation measurement technique described above can sense the effect of damage on the bridge model for a damage level as low as 7% change in stiffness applied over a length of 2.5% of the bridge span
Closed triangles are for months where the bridge is damaged, but the inferred tandem weight combination falls inside the 95% curve, i.e., damaged but damage not detected
Summary
While the bridge stock around the world is ageing, freight transport is growing and the demand on transport infrastructure is increasing. Data gathered from WIM systems have been used for other purposes such as updating notional traffic load models for bridge design [11], developing a site-specific bridge load model [12], calculating a dynamic amplification factor for bridge design and/or assessment [13], planning and management of road infrastructure [14], and assessment of fatigue load calculations [15,16,17] In recent studies, it has been investigated for SHM purposes. It is of note that, in all of these studies, the use of B-WIM technology for SHM purposes is limited to integral bridges This is because the B-WIM systems investigated in these studies use strain sensors to measure bridge deformations, which are only sensitive to local damage at the sensor location in a statically determinate structure. Capability of the proposed method to detect local damage on a bridge structure is demonstrated through numerical analysis on a 3-D FE bridge model
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