Cyclic behavior of cfrp confined nylon fiber-reinforced rc frameunder static load

Abstract

RC Buildings often experience localized damage caused due to seismic events, which, if kept untreated, might lead to catastrophic phenomena like a progressive collapse of floors. Different retrofit techniques are employed in RC buildings to prevent collapse and initiate a ductile response in frame members, among which Carbon Fiber Reinforced Polymer (CFRP) treatment has been found effective in damage control. On the other hand, masonry infill walls within frame systems are proven to improve the in-plane stiffness of the system by reducing lateral displacement. Recently, locally available nylon fibers are being used as short discreet fiber in order to enhance the performance of concrete. Hence, evaluating the response of CFRP treated damaged frames having nylon fiber within their concrete matrix will give insight to the overall behavior or structure. In this study four initially damaged frames were treated with CFRP laminates and then subjected to in-plane static cyclic loading. Masonry infills were incorporated in two frames and their responses were compared with the bare frames. Compressive strength and drying shrinkage of cement mortars with different nylon fiber contents were determined. In addition to that, masonry prisms with and without nylon fiber in the mortars and plasters were tested under compression. Moreover, at the optimum dose of nylon fiber, concrete cylinder compressive strength with various number of CFRP laminates were evaluated. It was found that the 0.1% dosage of nylon fiber provided maximum compressive strength in mortar. The masonry prism tests revealed that inclusion of optimum dose of nylon fiber within mortar only, and within both mortar and plaster increased the compressive strength capacities to 9.26% and 22.40% respectively. Introducing optimum dose of nylon fiber within concrete matrix increases the compressive strength by 20.16%, and when they were wrapped with single and triple layers of CFRP laminates this increase was 144% and 375% respectively. From the in-plane static test on retrofitted frames, it was found that inclusion of nylon fiber in concrete matrix resulted in almost 30% increase in load carrying capacity, and 22.2% increase in energy dissipation. After inclusion of infill wall, load carrying capacity increased almost 70%; displacements and energy dissipation reduced to 95.1% and 74.5% respectively. Finally, inclusion of nylon fiber within the mortar mixes between masonry layers of infilled frame increased the maximum load carrying capacity to 3.8%; and decreased the energy dissipation capacity to 17.85%.