Experimental study on the progressive collapse performance of RC frames with infill walls Sidi Shan a,b , Shuang Li a,b,⇑ , Shiyu Xu c , Lili Xie b,d a Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education (Harbin Institute of Technology), Harbin 150090, China b School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China c Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong Special Administrative Region d Institute of Engineering Mechanics, China Earthquake Administration, Heilongjiang, Harbin 150080, China article info Article history: Received 28 January 2015 Revised 1 December 2015 Accepted 13 December 2015 Keywords: Reinforced concrete frame Progressive collapse performance Experiment Infill wall Failure mode abstract The interaction between the infill walls and the reinforced concrete (RC) frame members in the progres- sive collapse process was examined experimentally in this study. Two 1/3 scaled, four-bay, two-story RC frame specimens, one of which was featured without infill walls while the other with infill walls, were tested. The frame specimens were designed in such a way that the center column of the first story was missing, in order to simulate the failure of the structural component due to abnormal loads or design flaws. The frame specimens were quasi-statically pushed downward at the top of center column under displacement control to investigate the progressive collapse mechanism of the RC frames, with a focus on the effects of infill walls. Specifically, the physical quantities and phenomena of great interest in this study include the collapse resistance force and mechanism, strain variation and crack development in structural components, and local and global failure modes of the frames. The test results showed that the infill walls can provide alternative load paths for transferring the loads originally only supported by the beams, and thus, improve the collapse resistance capacity of the RC frame. The infill walls, how- ever, may reduce the ductility of the RC frame and may change the failure mode of the frame. It is con- cluded that the infill walls may affect (i.e., either improve or impair) the performance of RC frames against progressive collapse in different aspects. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction In present design practice, the structural members of buildings normally are proportioned according to the strength and displace- ment demands imposed on the structures when the structures are subjected to various load combinations (known as the limit states), considering the regular dead loads and live loads such as the grav- itational load, seismic load, and wind load, etc. However, when the exceptionally large-magnitude, unpredicted loads are applied to a certain portion of these kinds of code-conforming buildings, pro- gressive collapse may still occur. Progressive collapse is the phe- nomenon of disproportionate damage to structures, initiated by the loss of local members which can be induced by abnormal loads, design flaws or malevolent events. Famous progressive collapse events includes the collapse of Ronan Point building in 1968 due to gas explosion and the collapses of Murrah Federal Building and World Trade Center in 1995 and 2001, respectively, owing to the terrorist attack [1]. It is generally recognized that the main resisting mechanism with respect to progressive collapse of frame structures include flexural action [2], compressive arch action and catenary action [3,4]. Flexural action is the resistance forces pro- vided by flexural resistance of frame members. Compressive arch action refer to the compressive arch formed in beams due to the restraint of surrounding columns. Catenary action is the vertical resistance mobilized by axial tension force developed in beams at large displacements. Despite the fact that infill walls are com- monly considered as non-structural members, it is well known that the infill walls behave as struts (often used in numerical models for seismic analysis) in frame structures and may have non-negligible effects on a structure’s resistance capacity against various failure modes. Nonetheless, although many experimental and numerical studies on progressive collapse of RC frame structures [5–14] have been performed, very few of them have taken the interaction between the infill walls and the frame members into consideration. Tsai and Huang [15,16] numerically investigated the progres- sive collapse of RC frames, and examined the effects of infill walls http://dx.doi.org/10.1016/j.engstruct.2015.12.010 0141-0296/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education (Harbin Institute of Technology), Harbin 150090, China. E-mail address: shuangli@hit.edu.cn (S. Li). Engineering Structures 111 (2016) 80–92 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct