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Structural Health Monitoring (SHM) of Concrete using Smart Piezo Modules (SPM)

Aging concrete infrastructure associated with material degradation and structural damage leads to structural integrity issues, which are extensively discussed across the world. However, the absence of an effective, in-situ, inexpensive method for structural health monitoring (SHM) of concrete structures has been identified as a concern by civil engineering communities. Most commonly used SHM techniques such as, visual inspection and laboratory tests of core samples, do not give a complete picture about the heterogeneous and anisotropic material, concrete. Instead, the results are highly localized and confined only to a specific area of the structure. Also, it is difficult to implement these methods on large scaled structures with complex geometries. Existing non-destructive testing (NDT) methods such as, impact echo, impulse response, radiography, acoustic emission, thermal field, etc., are also inconvenient and expensive. Thus, ultrasonic wave-based sensor/actuator systems are a promising alternative for real-time SHM of concrete structures.

Ultrasonic wave-based testing utilizes high frequency sound waves in the damage detection and material property assessment process. Piezoelectric transducers made of PZT (lead zirconate titanate) are widely used in ultrasonic sensing applications, due to high sensitivity, applicability to active sensing, low cost, quick response, availability in different shapes and small size. PZT is the most commonly used sensor material for SHM and NDT applications at present. Such material can develop an electric potential across its boundaries, when subjected to a mechanical stress. This phenomenon is known as the direct piezoelectric effect. In contrast, converse piezoelectric effect is the ability of piezoelectric material to produce mechanical stress waves in the presence of an electric field. These two properties make PZT transducers, ideal candidates for sensor-actuator applications. However, most of the research related topics uses embedded PZT sensors for condition assessment of concrete structures and requires the embedment of sensors in to the structure. Nevertheless, this limits the practical applicability of such methods to existing structures. Thus, this study aims to develop a sound, effective, inexpensive technique for in-situ continuous SHM of concrete using smart piezo modules (SPM), which is readily applicable to both new and existing structures. Specifically, this investigation provides a basis for the development of a non-destructive technique for damage identification, determination of impact-response, material property and durability assessment of concrete members.

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