Seismic response of autoclaved aerated concrete masonry infill walls under in-plane and out-of-plane seismic demands

Infill walls of reinforced concrete (RC) frames exhibit significant vulnerability when subjected to in‐plane (IP) and out‐of‐plane (OOP) seismic demands. Despite the vast number of tests investigating the behavior of brick masonry infill walls in RC frames, past research is concerned with infill walls made up of autoclaved aerated concrete (AAC) blocks. In this study, six single‐bay, single‐story, half‐scaled RC frames were tested under the action of IP cyclic displacement excursions and/or OOP pressure. The objectives of the tests were to investigate the IP behavior of AAC infilled RC frames constructed with or without fiber mesh reinforced plaster to observe the influence of the OOP loads on the IP deformation capacity. It was found that AAC infill walls increased the strength and stiffness of the test frames compared to the bare frame specimen. The specimens without the plaster overlay experienced cracking at inter‐story drift ratio of about 0.35%. The ultimate drift ratio corresponding to a 20% lateral strength loss occurred at about 2% interstory drift ratio. The presence of plaster, on the other hand, delayed the visual cracking of the walls up until 1% interstory drift ratio. The OOP loads applied on the frame by using an airbag system was found to significantly reduce the IP deformation capacity of AAC framed infill walls. These results show that AAC infill walls may not sustain the IP and OOP seismic demands expected in RC frame buildings and innovative solutions are needed to limit the damage

Potential Use of Locked Brick Infill Walls to Decrease Soft-Story Formation in Frame Buildings

The objective of this study is to investigate the effects of a new type of infillcalled locked brick infill adopting horizontal sliding jointsin reducing the soft-story formation in reinforced concrete (RC) frames with code-conforming seismic detailing. Nonlinear static time-history analyses were performed on multistory planar frames with only the upper stories infilled in order to force the soft-story irregularity. The parameters of frame and infill elements that were used in numerical simulations were obtained from half-scale RC infilled frame tests that had been performed by the author covering single story-single bay frames infilled with standard and locked bricks. The numerical simulations showed that the use of locked bricks to form infill walls has the potential to decrease the soft-story/weak-story formation in comparison to standard bricks due to its shear sliding mechanism and decreased upper-story/first-story stiffness, even in buildings that have noninfilled first stories. (C) 2014 American Society of Civil Engineers