In Plane Sliding Shear Behaviour of Unreinforced Concrete Masonry Retrofitted with Surface-Bonded Fibreglass Laminates

Abstract

<p>Lateral loads on buildings, either caused by wind or seismic events, are resisted primarily by the in-plane strength and stiffness of the walls oriented parallel to the direction of the applied load. The concern associated with relying on unreinforced masonry (URM) shear walls to transfer the load to the foundation is that the typical modes of failure are characterized by brittle behaviour, with rapid decreases in capacity and very limited deformations once the ultimate load is reached.</p> <p>Traditional strengthening techniques have several undesirable properties, including being labour intensive and adding weight to the structure. Past research has shown that fibre reinforced polymer (FRP) reinforcement is an effective method of increasing both the strength and ductility of URM. One of the most desirable properties of FRP is that it has a high strength to weight ratio.</p> <p>An experimental investigation was conducted to study the influence of surfacebonded fibreglass laminates on the sliding shear resistance of URM. The investigation was conducted in three phases:</p> <p>1 Phase One: Analyzing the performance of five different test specimen shapes retrofitted with GFRP to determine the most adequate configuration for further shear slip tests. The data was also of direct use as an evaluation of strength and behaviour of FRP reinforced masonry subjected to shear-slip failure. Thirty-seven shear slip specimens were tested to failure. The average increase in shear strength ranged from 3 .1 to 7. 7 times that of the unretrofitted counterparts.</p> <p>2 Phase Two: Assessing the feasibility of obtaining two sets to data from each test specimen.</p> <p>3 Phase Three: Assessing the shear-slip strength and behaviour of URM reinforced with fibreglass mesh, of different weights, adhered at two different orientations to the bed joint slip planes (0°190°, ±45°) using a modified mortar parging. Twenty-one shear slip specimens were tested to failure. Typically, for any given mesh weight, orienting the fibres at ±45° resulted in failure characterized by higher strength and less ductility compared to tests with fibres oriented at 0°190° to the bed joints. At ±45° orientation, the fibres ruptured at failure. When the mesh was oriented at 0°190°, the fibres pulled out of the cement parging, which limited the strength, but enabled specimens to undergo large deformations while maintaining fairly constant residual capacity.</p>