Damage Detection in Beam Bridges Using Quasi-static Displacement Influence Lines

Shaoyi Zhang,Yang Liu

doi:10.3390/app9091805

Abstract

Quasi-static strain influence lines (ILs) based on the Brillouin optical time domain analysis (BOTDA) technique have been proposed to effectively locate damage in beam bridges. Using measurement points with a high spatial resolution, the BOTDA technique supplies enough strain ILs to help detect damage in bridges. Unlike quasi-static strain ILs based on the BOTDA technique, quasi-static displacement ILs are relatively easy to implement in actual bridges; furthermore, only a few quasi-static displacement ILs are necessary for actual bridges. On this basis, an improved method is proposed to determine the existence of damage in beam bridges by using only a few quasi-static displacement ILs. First, the Hankel matrix of the damage feature, established based on the number of strain ILs, is reconstructed to generate the damage feature using only a few quasi-static displacement ILs. Second, the method used to obtain the metric for evaluating the damage feature is improved, thereby greatly increasing the efficiency of damage detection using quasi-static ILs. Finally, the effectiveness of the proposed method is demonstrated through both numerical analysis and experimentally measured data obtained during a quasi-static load test of a model bridge.

Highlights

In contrast to dynamic methods [1,2,3], static methods [4,5] exhibit obvious advantages in the detection of damage in civil structures: (1) static methods ensure a high accuracy of the measured static deformation of structures; (2) they effectively avoid the difficulties associated with identifying damage in structures; and (3) they do not need to consider various effects, such as the mass of the structure
The traditional method does not work for this damaged case. The reason for this inefficacy lies in the fact that the quasi-static displacement influence lines (ILs) are no longer smooth curves but volatile curves and the difference in the ILs is no longer sensitive to the damage suffered by the bridge, especially under conditions of small degrees of damage
14 the (a), performance compared with the proposed method and the traditional approach in consideration of the differences in the loading the reference state, it is difficult to differentiate the displacement ILs between the healthy conditions before and after damage

Summary

Introduction

In contrast to dynamic methods [1,2,3], static methods [4,5] exhibit obvious advantages in the detection of damage in civil structures: (1) static methods ensure a high accuracy of the measured static deformation of structures; (2) they effectively avoid the difficulties associated with identifying damage in structures; and (3) they do not need to consider various effects, such as the mass of the structure. Static methods have been increasingly employed to detect damage in structures using various static features, for example, the static displacement [6,7,8], static strain [9] and static flexibility of structures [10,11]. The static load test is commonly implemented to measure the static deformation of operational bridges to, for example, ascertain the displacement and strain along a cross-section of the superstructure. 13, a total of devices are displacement sensors are placed along the towing beams, that is, 5 sensors are attached to each are designed to simulate the damage of the transverse connection between the two T-shaped beams supporting the the moving moving vehicle, vehicle, aa total total of of 10 displacement sensors are placed along the towing beams, that is, sensors are attached to each displacement sensors areand placed along the beams towingsupporting beams, thatthe is, moving

Results

Discussion

Conclusion