In-plane cyclic behavior of brick walls strengthened with CFRP plates embedded in the horizontal mortar joint

Abstract

Unreinforced masonry (URM) buildings exhibit significant vulnerability under in-plane seismic loads due to poor tensile strength and integrity. An experiment was carried out to investigate the effectiveness of embedding carbon fiber reinforced polymer (CFRP) plates in the horizontal mortar joint on improving the in-plane seismic performance of URM wall that was prone to fail by diagonal shear failure mode. A total of five half-scale specimens, each measuring 2250 mm × 1500 mm × 240 mm, including two un-strengthened brick walls and three strengthened walls, were tested undergoing pre-compression stress combined with incremental lateral displacement. The CFRP plates were only embedded in the wall on one side in order to reduce the impact on building appearance and different reinforcement ratios were adopted. The failure mode, hysteretic behavior, shear strength, ductility, stiffness degradation and energy dissipation capacity of the specimens were discussed. The results showed that reinforcement can control the initiation and rapid growth of diagonal shear cracks. The strengthened masonry walls exhibited flexural rather than brittle shear failure with good ductility and energy dissipation. The ductility of the strengthened walls increased significantly with the increased reinforcement ratio and there was an optimal reinforcement ratio that maximized the ductility. The strengthened wall with medium reinforcement ratio showed the highest increase in ductility factor of 45.71% compared with the control specimen. The strengthened specimens displayed greater bearing capacity compared with the un-strengthened specimen. The largest increase in the shear strength of the strengthened walls was 10.16%, which indicates the effectiveness of the reinforcement method of used to embed CFRP in the horizontal joint to improve the in-plane seismic performance of URM walls. In addition, the abilities of several analytical models used to predict the shear capacity of the URM and strengthened walls were analyzed.