Out-of-Plane Strengthening of unreinforced masonry walls using textile reinforced mortar systems

Abstract

Masonry walls are popularly used in building envelopes because of their strength, durability, thermal resistance and aesthetical appearance. However, unreinforced masonry walls are vulnerable to out-of-plane loadings such as those resulting from earthquakes, gas explosions and blasts. In this study, the use of three different textile-reinforced mortar (TRM) strengthening systems to enhance the out-of-plane behavior of unreinforced masonry walls was investigated. These were polypropylene (PP) band-reinforced mortar, ferrocement and alkali resistant (AR)-glass textile reinforced mortar systems. Material tests were conducted on the compression strength of brick, mortar and strengthening matrix and tensile strength of PP band, wire mesh and AR-fibreglass textile mesh. In addition, tests were performed on walls specimens and strengthening systems to obtain the stress-strain relation in compression and tension respectively. Four-point-bending tests were then carried out to examine the flexural behavior of masonry walls strengthened with the TRM systems under consideration. The walls were tested with the continuous mortar joint parallel or perpendicular to the loading span. For each TRM strengthening systems, the walls were tested in two orthogonal loading directions and the reinforcement ratio varied. In total, 22 wall specimens were tested. Test results showed that ferrocement was highly effective in increasing the out-of-plane load carrying capacity but not the deformation capacity of the walls. AR-fibreglass reinforced mortar system provided comparable strength enhancement as ferrocement and also led to higher deformation capacity of the walls. The use of PP-band reinforced mortar system resulted in the largest deformation of the walls but lower load-carrying capacity. Analytical predictions based on the derived stress-strain relation of the masonry walls in compression and TRM systems in tension compares reasonably well with the test results. It was observed that the load-carrying capacity and energy absorption capacity based on the area under the load-deflection curve until peak load, increases with the reinforcement ratio or tensile capacity of the strengthening system, but were largely independent of the loading direction.