Seismic assessment of the in-plane/out-of-plane interaction of masonry infills in a two-storey RC building subjected to bi-directional shaking table tests

This paper presents a series of shaking table tests conducted on a 60%-scaled two-storey infilled reinforced concrete building. The main parameters include the presence of openings in the masonry infills and the effect of bi-directional dynamic shaking to the latter. The building was subjected to four different levels of shaking intensity, ranging up to the Maximum Considered Earthquake (MCE), equivalent to 150% of the design earthquake. The study focuses on and evaluates the damage caused by combined in- and out-of-plane shaking. Under the design level earthquake, the second-storey infill walls with openings were severely damaged, with near-collapse of a masonry pier. For the fully infilled direction without openings instead, diagonal cracking as well as out-of-plane inclination of the infill wall in the second storey were observed. Due to the interaction between the two loading directions and the direct adverse effect of the in-plane damage on the out-of-plane resistance of the infills, the out-of-plane collapse of 3/4 of the second storey masonry infill occurred during the MCE. The reported damage observations on the masonry-infills with or without openings provide further insights on the vulnerability of non-seismically designed reinforced concrete buildings. Additionally, the seismic performance of the structure is assessed using further structural response quantities recorded during testing, including floor accelerations, inter-storey drifts, base shear forces and reductions in natural frequency. Future testing will focus on investigating the effectiveness of retrofitting measures in improving the connection between the infill and frame, reducing in-plane damage, and preventing out-of-plane failure of the infills.