Measuring strain fields in FRP strengthened RC shear walls using a distributed fiber optic sensor

Abstract

This paper presents results on the applications of a truly distributed fiber-optic sensor (DFOS) in the cyclic testing of a reinforced concrete (RC) shear wall. To improve the performance of the wall, the RC shear wall is strengthened using externally bonded fiber-reinforced polymer (FRP) sheets. The DFOS is used as a replacement for conventional strain gauges to measure the strain distribution in the FRP sheet. Conventional electrical strain measurement techniques require a priori knowledge of measurement location and do not provide spatial information over a large area of a structural component, such as a wall. In recent years, the development of fiber-optic sensing technologies offers clear advantages compared to the conventional strain measurement approach. In particular, the DFOS has the unique capability of capturing strain at any location along the length of a fiber, without pre-determining the measurement locations before the test. The DFOS provides high precision strain measurement by optical frequency domain reflectometry. This allows full two-dimensional spatial strain measurement over the entire area of the shear wall. The DFOS can capture detailed response and failure mechanisms of the concrete and FRP as well as their contributions to the resistance of the shear wall. Experimental results are used to develop a better understanding of the behavior of RC shear walls retrofitted with FRP sheets, and assist in improving design guidelines for the application of FRP in RC structures.