ABSTRACT
In the present paper, a novel technique is used to monitor and evaluate shear crack patterns in Partially Prestressed Concrete (PPC) beams. The proposed technique is based on experimental data obtained in two PPC beams tested in laboratory and instrumented by Distributed Optical Fiber Sensors (DOFS). The DOFS conform optical fiber grids bonded in the surfaces of the beams. The DOFS experimental data were obtained using an OBR (Optical Backscattered Reflectometer) system that provides continuous strain data with high spatial resolution and cracks can be characterized. The continuous (in space) monitoring of the strain along the DOFS, including the crossing of a crack provides additional information without requiring prior knowledge of the cracked zone.
Several experiences have demonstrated the feasibility of using OFDR theory and SWI technique in the structural monitoring of concrete structures (Villalba and Casas 2013, Rodriguez et al. 2015). In the specific case of detection, location and control of cracking in concrete structures, OBR system is an attractive monitoring tool. In the evaluation of shear crack pattern, the inclination of the cracking pattern is an additional unknown property. Two PPC beams named I1 and I2, were tested using DOFS grids as measuring alternative to check the proposed structural monitoring method. Correlation between shear crack pattern and detected peaks by OBR system at 262 kN in beam I1. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig69_1.jpg"/>
According to the preliminary results obtained in this paper, the use of DOFS is a feasible methodology to obtain important information in the study of shear structural behavior in concrete structures. Continuous strain data at different loading levels were obtained with high spatial resolution by OBR system. Using this data, detection and location of flexural and shear cracks were obtained without requiring prior knowledge of the cracked zone.
Finally, in the evaluation of the shear crack pattern, not only crack initiation and location are of importance, but also crack width, shear crack angles and shear sliding displacements along the cracks have to be measured to evaluate the shear performance of a structural element.
