The Study Of Active Damage Monitoring For Concrete Structures Based On Piezoelectric Smart Aggregate

The speed of infrastructure construction has been accelerating with the steady development of China’s national economy since 21th century, due to which more and more large-scale and complex engineering projects were established. However, many engineering structural problems caused by a variety of natural conditions pose potential threats to life and property security of the people and the society. The emergency of smart structure in civil engineering could help to provide effective solutions for the issues mentioned above. Smart Aggregate (SA), designed based on the actuation effect of piezoelectric materials, possesses the characteristics of sensing and driving. Besides, S A has the advantages of rapid response, low cost, easy processability, simple structure, low energy consumption, good linearity, and high reliability, etc. This paper proposes a SA-based damage active monitoring for reinforced concrete structures. The main aspects are concluded below.(1) First of all, carry out the study of local damage of concrete monitor based on local vibration caused by SA excitation. The array SA based on stone is arranged in the concrete, and one SA is taken as an incentive, the rest as a receiver. On SA of the incentive, it sweeps to produce localized vibrations in the concrete, and the stress of SA acquisition is collected on the receiver. The relationship between the changes in the spectrum of SA and the concrete damage is analysised, and index based on the area of the spectrum SA is established, and it establishes the relationship between concrete damage index and extent of the damage. The test results show that the index increases gradually with the deepening of damage, showing the increasing of energy emission and thus verifying the feasibility of this monitoring approach.(2) Secondly, carry out the study of damage detection on simulation concrete which based on SA sweep excitation. Arrange SA array of metal packaging in low elastic modulus simulation concrete materials, exert sweep excitation on one of the SA, let it produce fluctuation in simulation concrete, use the rest of SA to monitor the stress field. Set up the concrete damage index which based on receive SA stress spectrum area, establish the relationship between the concrete damage index and the level of concrete damage. Use this monitor method to monitor simulation concrete arch dam’s damage process during shaking table experiment. The research shows, this monitor method can effectively capture the micro cracks in simulation concrete.(3) Thirdly, Carry out the study of damage detection on concrete which based on SA instantaneous excitation. Use initiative monitor method of concrete Structures damage, exert Gaussian pulse modulation excitation on SA, the center frequency of the excitation chose 30 kHz and 70 kHz, monitor the stress wave’s spread process in concrete and the impact of the hollow in concrete on stress wave’s spread process. The results showed that:during the spread in concrete the stress wave is linear attenuating, the hollow in concrete may cause amplification effect during stress wave’s partial spread.