ABSTRACT

To assist in understanding the behavior of the shear wall specimens and the performance of the rehabilitation strategy, this study employs an image analysis method capable of capturing crack distributions, displacement and strain fields in structural experiments. The technique uses a freely available software called ImPro Stereo to analyze stereo images taken of the deformed specimen over the course of the test (Yang et al., 2014). By applying a unique pattern to the surface of the wall, the software is capable of tracking unique points as the test specimen deforms under load and uses

1 INTRODUCTION

Reinforced Concrete (RC) shear walls are a common structural system used to resist lateral loads including wind and earthquake loads. Unfortunately, there is a large stock of existing shear wall buildings designed according to older, obsolete design standards. These standards have littleto-no consideration for earthquake induced lateral load. The typical design deficiencies of the time included insufficient shear reinforcement, no concrete confinement at the two ends of the shear wall and lap splices of the longitudinal reinforcement in the plastic hinge region along the base of the wall. Consequently, the shear walls in these older structures are susceptible to damage during an earthquake. To repair a deficient structure and restore or improve its seismic performance, there are a number of available retrofitting solutions. However, many of these techniques can be time consuming and intrusive, requiring the structure to remain un-operational for an extended period of time. Alternatively, a minimally disruptive retrofitting strategy consisting of externally bonded Carbon-Fiber Reinforced Polymer (CFRP) sheets provides a simple and cost effective solution to

this information to track important structural parameters used to quantify the behavior of the element, such as displacement and strain. The feasibility of using the image analysis technique to track debonding or separation between the CFRP sheets and the underlying concrete is also evaluated. ImPro Stereo has been used in past experiments over a small region of a test specimen (Yang et al., 2012; Yang et al., 2015). The use of ImPro Stereo in structural experiments is shown to be an effective alternative to conventional measurement techniques, such as electrical strain gauges, which would require hundreds of sensors to monitor the behavior of such a large area. In addition, the surface preparation time, cost of the sensors and the large data acquisition systems required is prohibitive. This experiment expands on past research and evaluates the effectiveness of using ImPro Stereo over the entire surface of a large structural element.