Quasi-static cyclic in-plane testing of masonry walls strengthened with a single-sided fabric-reinforced cementitious matrix overlay and flexible anchorage

Abstract

An experimental program was undertaken to assess the effectiveness of a new retrofit concept to improve the in-plane behavior of unreinforced clay brick walls by means of full-scale static-cyclic in-plane tests. The proposed seismic retrofit system combines two standalone retrofit measures for in-plane and out-of-plane strengthening of masonry walls. The inplane reinforcement consists of a single-sided carbon Fabric-Reinforced Cementitious Matrix (FRCM) overlay, and anchors embedded with a flexible adhesive in the masonry. The out-of-plane reinforcement, which consisted of deep mounted Carbon Fibre Reinforced Polymer (CFRP) strips embedded with a flexible adhesive in the masonry, was included in the study to investigate the possible degrading effects of the deep groove on the in-plane behavior. A total of nine full-scale reinforced masonry walls with three different geometries were tested under three different axial loads. None of the specimens showed shear failure at both the reinforced and the as-built side. Cracking predominantly occurred at the interface between the bottommost bed-joint and the foundation beam. The out-of-plane reinforcement did not affect the in-plane strength, as no vertical shear cracks occurred. Moreover, it was found that the anchors increased both the rocking and sliding resistance of the walls. An analytical model was proposed covering the rocking and sliding resistance of the reinforced walls, providing a good approximation of the experimentally obtained in-plane strengths. Additional pull-out experiments showed that the testing scenario where the tensile forces in the anchor were transferred to CFRP strip, provided a good approximation of the analytically determined anchorage strength.

Masonry Elements Strengthened with TRM: A Review of Experimental, Design and Numerical Methods

“…In some of the available tests (Table 2), the shear-type scheme was reproduced (Figure 3a), avoiding rotations at the panel top [31,[47][48][49][50] and recreating, in such a way, the typical boundary condition of piers in a building with strong spandrels [51]. In contrast, a cantilever scheme (Figure 3b), which allows free rotation at the top [42,43,[52][53][54][55][56][57], is representative of buildings with weak spandrels. The shear-compression tests available in the literature on TRM-strengthened panels typical concern samples having widths generally ranging from 800 to 3000 mm, with slender ratios from 0.68 to 1.6; the axial stress level is usually in the range 2.5%-10% of the masonry compressive stress or, in some cases, higher (e.g., 20%-30% [47,53,54]).…”