Online Monitoring of Flexural Damage Index of a Cable-Stayed Bridge

Byeong Hwa Kim

doi:10.1155/2019/7607214

Abstract

This work introduces a recent application of the online nondestructive damage assessment system into a cable-stayed bridge. A set of ambient modal parameters are automatically extracted every 20 minutes using real-time signal data collected from a total of 26 accelerometers attached on the deck plate of the bridge. Then, a set of modal flexibilities are reconstructed by the combination of the extracted modal parameters with the approximated modal mass of the girder. Next, the curvature of the modal flexibility is approximated by a central difference formula. Finally, the set of flexural damage index equations is constructed by comparing the modal curvature of the damaged state to that of the undamaged state. Solving the overdetermined flexural damage index equations, the desired damage index is finally quantified. The resulting index clearly indicates the location and severity of the potential structural damage on the girder. Based on the overall performance of the implemented health monitoring system, the bridge operator’s damage index control criteria are set to ±20% of the undamaged state.

Highlights

Long span bridges are a key component of the nation’s ground transportation infrastructure network. e bridge’s service life may be shortened due to various hostile environmental conditions
Many reviews [1,2,3,4,5,6,7] on vibration-based nondestructive damage evaluation (NDE) methods show that the mode shape curvature (MSC) method by Pandey et al [8] and the damage index (DI) method by Stubbs and Kim [9] accurately detect the location and severity of the damage
An online vibration-based NDE system has been successfully implemented on the deck plate of a cable-stayed bridge

Summary

Introduction

Long span bridges are a key component of the nation’s ground transportation infrastructure network. e bridge’s service life may be shortened due to various hostile environmental conditions. Many reviews [1,2,3,4,5,6,7] on vibration-based NDE methods show that the mode shape curvature (MSC) method by Pandey et al [8] and the damage index (DI) method by Stubbs and Kim [9] accurately detect the location and severity of the damage. To resolve first and second drawbacks of the MSC method, the flexural damage index equation (FDIE) method [10,11,12,13,14] and the nodal curvature method [15, 16] are proposed. Many full-scale deployments [30,31,32,33] of the vibration-based NDE methods have been reported, only the DI method shows applicability to real-time SHM systems [31, 32]. is study introduces, for the first time, the fullscale field application of the FDIE method to an online SHM system

Vibration-Based NDE System

Ambient Modal Analysis

Damage Index from FDIE Method

Findings

Summary and Conclusions