Multi-Parameter Correlation Approach for Structural Health Monitoring of Operational Highway Bridges
thesisposted on 28.06.2013, 00:00 authored by Ali Zarafshan
Highway bridges across the US are getting older and increasing traffic demands engenders the safety of these structures. Therefore, requirements for methodologies to insure the safety of the public transportation which are using these infrastructures seem inevitable. Fiber optic based structural health monitoring systems are valuable tool in bridge safety management inventory. They can provide structural feedback in real-time about the performance of highway structures under railway and traffic loads. I have employed these systems for health monitoring of bridges in both super and sub structural systems. Scour is the major cause for many bridge failures and damage to piers and abutments and is not easily noticeable because it is buried under the channel flow. I have developed, tested, and field implemented a new and simple type of scour sensor. The scour depth detection concept is based on measuring the fundamental frequency of vibration of a rod embedded in the riverbed. Then, a computational approach is developed based on the Winkler spring reaction soil model for automated calibration of the scour sensor during installation in the riverbed. The scope of the research included development of the theoretical basis for the sensor, establishment of the computational methodology for detection of the riverbed foundation properties, proof-of-concept laboratory tests, small-scale field verification tests, and installation and remote monitoring system on scour critical bridge in Illinois. In addition, current research proposes a novel method for reference-free real time deflection measurement of bridges by employing the output of a smart sensor network installed on the bridge. This method estimates the actual deflection profile of the superstructure with a high order polynomial. To construct the polynomial profile curve, real-time rotation and curvature of the bridge, collected by tiltmeters and strain gauges were used. Several live load tests were performed on two highway bridges in the states of California and Illinois. The former bridge had a concrete girder box superstructure, while the latter had a continuous steel girder with concrete slab. Detailed finite element model (FEM) of these bridges were also developed. Results from the proposed method were compared with the recorded data and output of FEMs.