Structural performance of RC shear walls with post-construction openings strengthened with FRP composite laminates

Over the past few decades, retrofitting of existing buildings, rather than new construction, became more popular due to economic reasons and the benefit of shorter service interruptions of constructed facilities. Change of use of an existing building may require the removal of portions of the structural members such as introducing door and window openings in an existing shear walls. In these scenarios, a remedial external retrofit is needed to restore the structural integrity and to regain building's seismic ductility. This paper presents the results of an experimental study that aimed at evaluating the structural performance of reinforced concrete (RC) shear walls, with different opening geometries strengthened with fiber-reinforced-polymer (FRP) carbon/epoxy composites laminates. Experimental results indicated that the proposed FRP lamination system for RC shear walls with post-construction openings was successful in enhancing both the strength and ductility of retrofitted walls. The average strength gain and ductility enhancement of the retrofitted walls, as compared to the unstrengthened walls ranged from 20% to 28%. An analytical procedures for analyzing retrofitted reinforced concrete with different opening geometries is also presented. For design purposes, a proposed efficiency factor that accounts for the efficiency of different lamination protocols is discussed. Conclusions and recommendations for future research are presented.