Design and fabrication of a new fiber-cement-piezoelectric composite sensor for measurement of inner stress in concrete structures

Abstract

Rare suitable sensors are reported till now for the accurate measurement of inner forces at the concrete structures. In this study, a novel sensor is designed and fabricated for the evaluation of inner stress in the concrete structures under dynamical loads. By embedding this sensor in the critical points of the modern concrete structures (e.g. high-rise buildings, large-span bridges, dams, etc.), the heath monitoring of such structures may be easily done. The proposed sensor is a 5cm×5cm×5cm cube made of a novel cement-resin-fiber composite matrix. A number of circular piezoelectric sheets with the same polarization alignment are embedded at the center of the cube with the certain distance from each other. The composite material used in the construction of the proposed sensor is in fact a new matrix composed of Portland cement, resin, water, fine silica and polymeric fibers which guarantees the strength, safety and sensitivity of the sensor at high level of stresses. The performance and reliability of the presented sensor has been proved through experimental tests. By considering different range of input force frequency (ω), it was found that the simple exponential law ΔV=0.8exp(−0.037ω)ΔF exists between the amplitude of output sensor (ΔV) and amplitude of input force (ΔF). Compared to optical sensors and other available types of sensors which usually require special fabrication technology, the proposed sensor is low-price and easy to build and install. High sensitivity and precision in the range of 0.5–50Hz, good compatibility with concrete, high durability, and the generating of strong output signals are other advantages of the proposed sensor.