Multi-channel random decrement smart sensing system for concrete bridge girders damage location identification

Abstract

Health monitoring of infrastructures is one of the essential modern services for civil engineering structures. A design of a Structural Health Monitoring (SHM) system that allows a continuous assessment of the structure’s integrity is required to increase safety, and to optimize operational and maintenance costs. Nowadays, non-destructive techniques are common to predict the damage as it monitors the structure during its service lifetime. The advances of using Fiber Bragg Grating (FBG) array sensors for continuous monitoring has been proven to be far superior and more accurate than strain gauges and accelerometers due to the great reduction in noise signals. The Random Decrement (RD) technique is one of the output measurement diagnostic techniques used for identifying the dynamic properties of bridge girders. The technique to be applied on multi-channels for enhancing the efficiency of data aggregation and integrity identification using fiber optic multi-channel sensor networks system known as Multi-Channel Random Decrement (MCRD) for concrete bridge monitoring. The significance of RD and MCRD approaches in SHM is that it determines the bridge’s dynamic properties without the prior knowledge of the magnitude of excitation forces; so the identification system of the bridge is based on random bridge actual traffic loading response through the installed FBG sensing system to record the dynamic response due to the applied traffic loading.The concept has been used before for steel and metal structure. However, the concrete material is a nonlinear elasto-plastic damaged material with unique qualities of cracking, tension softening, shear degradation and tension stiffening effects. The emphasis for the steel beam monitoring is focused on the change in the natural frequency; however, the emphasis for the concrete beam monitoring is focused on the change in the Random Decrement Damping (RDD) between the intact and damaged case. The change in RDD is more evident for concrete beams due the rapid change in stiffness due to cracking and the propagation of cracking due to loading. The focus in this work is to assess the applicability of using MCRD with FBG arrays for monitoring reinforced concrete (RC) girders based on experimental testing. For validating the feasibility of the proposed approach, a laboratory investigation has been performed on a main and secondary girder to identify the suitability of using FBG sensors on RC girders to detect the damage and locate it. The results of the investigation showed that MCRD using FBG sensors has the potential to detect the damage location that could be implemented effectively in bridge monitoring strategies.