DOI: 10.1002/cepa.814 FULL PAPER Seismic response of autoclaved aerated concrete masonry infill walls under in-plane and out-of-plane seismic demands Baris Binici 1 Erdem Canbay 1 ˙ Ismail Ozan Demirel 1 Alper Aldemir 2 U˘ gur Uzgan 3 Zafer Eryurtlu 3 Ahmet Yakut 1 1 Department of Civil Engineering, Middle East Technical University, Universiteler Mah, Ankara, Turkey 2 Department of Civil Engineering, Hacettepe University, Ankara, Turkey 3 AKG Gazbeton, ˙ Izmir, Turkey Correspondence Prof. Baris Binici, Department of Civil Engineering, Middle East Technical University, Universiteler Mah., K2-312, 06800 Ankara, Turkey. Email: binici@metu.edu.tr Funding information Turkish Autoclaved Aerated Concrete Association (TAACA) Abstract 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 investi- gating 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 influ- ence 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. KEYWORDS AAC infill walls, combined response, in-plane, out-of-plane 1 INTRODUCTION Infilled frame response has long been an attractive topic of inter- est among earthquake engineering community. Earthquake aftermath observations reveal that widespread damage on masonry infills have been observed on RC buildings where in some cases damage on infill is important in determination of structural performance of the building. Excessive infill damage without significant structural damage would affect the psychology of dwellers and their living in their apartments. Therefore, the control of infill damage is important for returning to usual life aftermath of earthquakes. Consequently, there is a constant effort to unveil the response of infill walls under the effect earthquake excitations. However, the studies on the AAC infilled frames are very limited in number. Compression struts and tension struts are formed along the diag- onals of infill walls placed inside RC elements, which shows a ten- dency to crack along diagonals under significant lateral displacement c  2018 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. demands [1,2]. This damage could cause loss of infill walls that might result in a softer and weaker story [3,4]. In other extremum point, the out-of-plane (OOP) acceleration demands may cause loss of stability due to loss of contact at the edges of infill walls stemming from exces- sive in-plane (IP) damage [5,6]. Therefore, the behavior of infill walls are not independent of IP and OOP demands. Numerical and experimental researches [7,8] have been conducted aiming at understanding infill wall and bounding frame interaction, which is influential for building response under seismic excitation. Although majority of the previous research are focused on investi- gation of IP and OOP response separately, infilled frames are usu- ally excited under combined bidirectional loading where failure of the walls are determined by the interaction of combined IP and OOP load- ing. Previous experimental research on combined loading of infilled frames are usually conducted by sequential loading of bidirectional lateral loads, which results in weak interaction between IP and OOP forces according to Flanagan and Bennett [9]. Thus, more realistic test ce papers. 2018;2:241–245. wileyonlinelibrary.com/journal/cepa 241