Structural Health Monitoring and Damage Evaluation of Full-Scale Bridges Using Triaxial Geophones: Controlled In-Situ Experiments and Finite Element Modeling

Abstract

The purpose of this study was to evaluate the effectiveness of various vibration-based damage detection methods using triaxial vibration records obtained using inexpensive geophones during in-situ, full-scale, damaged bridge tests. Geophones are passive directional sensors and much cheaper than accelerometers which are typically used for structural vibration measurements. However, magnitude and phase errors associated with a geophone’s output must be corrected for if they are implemented in bridge monitoring systems. This research discusses correction procedures for magnitude and phase errors associated with geophones. A simply supported beam was analyzed to verify that the correction procedures and modal parameter identification procedures used produced reliable results. A full-scale bridge test was also performed to further validate the correction and modal analysis procedures used. The results of the simple beam and full-scale bridge tests were validated using finite element modeling. Vibration-based damage detection relies on changes in the dynamic properties of a structure to detect damage. Only one other study was found that compares various vibration-based damage detection techniques using full-scale damaged bridge tests. Thus, a need remains for further comparison of vibration-based damage detection techniques using vibration data collected entirely on full-scale bridges. This study compares various vibration-based damage detection techniques using triaxial vibration records obtained during separate in-situ, full-scale, damaged bridge tests. Furthermore, the damage detection techniques are extended to three dimensions to evaluate three dimensional response of the bridge to damage. This is a unique aspect of the current research because no other three dimensional data sets obtained from in-situ, full-scale, damaged bridge tests have been reported in the literature. Finite element modeling is perhaps the most widely relied upon method of structural and mechanical analysis. In the field of vibration-based damage detection, finite element models are often used to plan field tests, to verify field test results, and to produce damaged data sets when the actual structure is unable to be damaged. As part of this research, finite element models were constructed to lend credibility to the field test results and to investigate damage scenarios other than those inflicted during the field tests