In-plane/out-of-plane seismic performance of masonry infilled RC frame structure made of nano-SiO2 reinforced mortar: Experimental study

Due to the seismic vulnerability of conventional masonry infill wall Reinforced Concrete (RC) frame buildings, which caused the infill wall structure to break and collapse, resulting in serious casualties and property damage. It was necessary to fully understand the action mechanism and seismic strengthening of the infill wall structure. Considering that few researches had paid attention to the effect of mortar performance on the seismic behaviors of infill wall structure, this study was the first to use a nano-SiO2 (NS) reinforced mortar to construct masonry infill wall RC frame structure. The pure out-of-plane (OOP) and in-plane and out-of-plane (IPOOP) loading tests were conducted to validate the structure's seismic performance. The experimental results of comparison with ordinary mortar specimen were shown. Due to the mitigation of the cracking of wall in pure OOP test, the initial stiffness, load-bearing capacity and ultimate displacement of new mortar specimen were increased by 65.88%, 23.57% and 11.12%, respectively. However, both infill wall specimens exhibited the similar cracking characteristics and load-displacement response, those indicated that the improvement in mortar performance was not sufficient to change the failure mode. In the in-plane (IP) tests, the infill walls constructed with new mortar provided a better diagonal bracing mechanism, resulting in a 13.32% and 12.67% increase in the IP load-bearing and energy dissipation capacity. The less side shear cracking of infill wall caused stiffness degrades more slowly. In the IPOOP tests, at approximately the same previous IP damage level, the slower propagation of crack resulted in a slower reduction in the load-bearing capacity and an increase in the deformability during subsequent OOP loading. Therefore, the application of the new mortar improved the shear and bond strength of the members, which mitigated IP damage and improved the stability of the wall, while slowed down the OOP cracking of the wall and reduced the risk of collapse.