Smart Aggregates: a Distributed Intelligent Multi-purpose Sensor Network (DIMSN) for Civil Structures

Early-age strength monitoring, impact detection, and structural health monitoring are important issues for concrete structures, especially concrete infrastructures such as bridges. A distributed intelligent multi-purpose sensor network (DIMSN) using innovative piezoelectric-based smart aggregates is proposed in this paper to address these important issues. The smart aggregate is fabricated by embedding a water-proofed piezoelectric patch into a small concrete block. The smart aggregates are then placed at the desired locations in concrete structures before casting to form a distributed intelligent multipurpose sensor network. In this paper, a two-story concrete frame is used as the object to test the multi-functionality of smart aggregates and the DIMSN. The early-age strength monitoring is performed by monitoring the harmonic response amplitude of smart aggregates. Experimental results show that the predicted concrete strength matches the experimental results obtained in the compressive test. Impact tests are by performed by impacting the concrete frame at different locations. Experimental results show that the impact response is captured by the distributed smart aggregates and the energy of the impact response is related to the distance between the smart aggregate and the impact location. After the concrete strength is fully developed, structural health monitoring is conducted on the concrete frame through a destructive push-over test. Experimental results show that the proposed damage index matrix reveals the time history of health status of different locations. The proposed smart aggregate-based health monitoring approach is more sensitive than the traditional approaches that use microscopes and LVDTs. The proposed distributed intelligent multi-purpose sensor network has the potential to be implemented to the comprehensive performance evaluation of concrete civil structures.