Innovation in Piezoceramic Based Structural Health Monitoring
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Recent structural failures in both developing and developed countries highlight the importance of structural health monitoring, which has the ability to provide early warning based on real time monitoring of the structure of interest. The versatile functions and low cost of piezoceramic material has demonstrated its capability as transducers in structural health monitoring. This dissertation investigated modeling and innovative applications using piezoceramic based smart aggregate transducers for health monitoring of various structures. A theoretical and experimental modeling study of piezoceramic based smart aggregates were firstly conducted. Fundamental equations of a smart aggregate were established and numerical simulations were performed. The resonance and anti-resonance frequencies of a smart aggregate sample were computed, and were later verified by experimental tests. Many structural failures were initiated by cracks. A chapter of this dissertation is devoted to crack detection using piezoceramic based transducers. Two types of structures, a pipeline and a concrete column, were investigated. For the pipeline structure, an active sensing system with distributed actuators and sensors detects the crack and monitor the crack development. For the concrete column, the cyclic crack open-close condition was determined by embedded smart aggregates using wavelet packet-based structural damage index. Steel plate reinforced concrete structures are increasingly used in civil engineering. However, the bonding between the steel plate and the concrete is not well studied nor well known. This dissertation investigated detection of bond slip between the steel plate and concrete using smart aggregates. With appropriate deployment of smart aggregates in concrete structure and steel plate surface, shear stress induced bond slip phenomenon was monitored in real time. The severity of debonding was also characterized using the proposed method. Concrete structures are often used as underground containment for nuclear materials. Cracks and underground water are a lethal combination to migrate the radioactive pollution. This dissertation proposed an effective active sensing based method to detect concrete cracks and to further detect water presence in these concrete cracks, as experimentally demonstrated. Concrete is the most popular structural material and understanding its very early age (0-20 hours) hydration performance is of great importance. This dissertation proposes a novel approach to this topic using smart aggregate based active sensing approach. Two modes of smart aggregate, compressive mode and shear mode, were investigated and the results were compared. Both time domain and frequency domain analyses were conducted and the proposed approach can clearly identify the three distinct states, the liquid state, the transition state, and the hardened state, during the concrete hydration process. Soil freeze-thaw condition plays an important role in structural soil interaction in cold regions. The last chapter of this dissertation presents an innovative active sensing based method to monitor soil freeze-thaw condition using embedded smart aggregates. Since wave propagation is highly sensitive to the mechanical properties of soil during the freezing and thawing process, the received stress wave can be an effective indicator to determine the soil status. A wavelet packet-based soil frozen index was proposed and successfully applied to monitor the soil freezing or thawing status.