Health monitoring of existing structures

The primary objective of this dissertation research is to explore the issues that have not been previously studied but are important to the implementation of vibration-based structural health monitoring (SHM), by performing large scale seismic shaking table experiments, long term monitoring of real-life structures and computer analyses.; The first part of this dissertation is devoted to examining the soil-structure interaction (SSI) effects on the identified modal parameters using ambient and seismic records measured on a four-story reinforced concrete building which has been instrumented with 43 accelerometers. These sensors are installed not only on the superstructure but also in the soil to examine SSI effects. It was observed that the modal parameters obtained during the earthquakes differ from those obtained under ambient vibrations due to the SSI.; In the second part, vibration based monitoring of a new concrete bridge and identification of its stiffness change was performed over a five-year period. Automated system for wireless data transfer, collection and analysis for SHM purposes is developed. It was clearly seen from the trend in identified modal values and structural parameters that the bridge was aging. The information obtained in this study is valuable for studying aging of similar bridges.; In the third part, a large-scale shaking table test of a three-bent concrete bridge model to different damage levels by a sequence of earthquake motions with increasing intensities was performed. This seismic shaking table test represents the first effort to verify EKF experimentally using a large-scale realistic bridge model subjected realistic seismic damage. Identification of stiffness value is highly useful for estimation of post-event capacity of structures.; In the last part, the use of the structural parameter values identified based on vibration measurement in the estimation of the remaining capacity of a bridge structure after a damaging event is presented. In the scope of this research, it was shown that remaining structural capacity estimation based on the design values and updated in Bayesian sense is higher than the one estimated using identified parameters based on vibration measurement. This is the first effort to develop an approach to estimate remaining structural capacity using SHM results.