Modelling of masonry infilled RC frames subjected to cyclic loads: State of the art review and modelling with OpenSees Nurbaiah Mohammad Noh a,⇑ , Laura Liberatore b , Fabrizio Mollaioli b , Solomon Tesfamariam a a School of Engineering, The University of British Columbia, Kelowna, BC, Canada b Department of Structural and Geotechnical Engineering, ‘‘Sapienza” University of Rome, Italy article info Article history: Received 6 February 2017 Revised 3 June 2017 Accepted 2 July 2017 Keywords: Masonry infill walls In-plane behavior Macro-model Equivalent strut abstract Reinforced concrete frames with unreinforced masonry infill walls represent a widely adopted building system. During seismic events, infill walls, usually considered as non-structural elements, may signifi- cantly affect the characteristics of the system in terms of in-plane stiffness, strength, and energy dissipa- tion capacity. The assessment of framed structures infilled with unreinforced masonry walls has been investigated since the 1950s. Developing reliable numerical models of infill walls has become an impor- tant issue since then. The analytical simplified model based on equivalent diagonal struts is often used to assess the infilled frames response. The nonlinear behavior of the equivalent diagonal strut is usually described by constitutive laws that account for the stiffness, the strength and the hardening or softening behavior of the infill. The present work focuses on the evaluation of various parameters needed to define the monotonic and hysteretic response of infill walls modelled by equivalent struts. In order to select a simple and reliable analytical model that suitable for representing the infill wall response, different strut formulations and hysteretic models have been analysed in detail and used to reproduce several experi- mental tests available in the literature. The numerical analyses are performed by means of the OpenSees computer program. Three uniaxial material models available in OpenSees are used to assess their capability in reproducing the experimental hysteretic response. Finally, from the comparison among different models and between numerical and experimental results, suggestions are made to properly model the in-plane non-linear response of infills. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Reinforced concrete (RC) frame buildings with unreinforced masonry (URM) infill walls, henceforth denoted as masonry infilled RC frame structures, are widely used in building constructions. Damage observation from past earthquakes (e.g. [1–3]) show that the seismic response of these buildings is strongly affected by the presence of masonry infill walls. The URM infills may increase lateral stiffness, strength, and energy dissipation capacity of the bare RC frame [4–6]. The presence of the infill walls on the bare frame might induce unexpected forces distribution and lead to local collapse when it is subjected to cyclic loading [7]. These effects depend on the infills geometrical distribution in plan and elevation, infill mechanical properties, infill aspect ratio, configura- tion of openings, and construction methods [6,8]. The seismic behavior of masonry infilled RC frame buildings has been investigated since the 1950s. Many experimental studies were conducted (e.g. [9–18]) to investigate the response of infill walls and their interaction with the surrounding RC frame. Concur- rently, analytical studies have been carried out by researchers (e.g. [4–6,19–25]) to model and evaluate the performance of these buildings under both monotonic and cyclic loads. Although there are numerous studies in the literature, the issue related to the assessment and the modelling of masonry infilled RC frames remain unresolved. Lack of a standardized guideline on how to configure an infill in a global seismic analysis of infilled frames is a main issue. Besides, the infill influence on the seismic behavior of framed structures is widely recognized but how it is incorpo- rated in the design process differs noticeably from one country to another [26]. Nevertheless, masonry infill walls are often neglected in the design process and analytical modelling, and are considered as non-structural elements. Reliable analytical methods are needed for the assessment of infilled framed structures [6]. This task is rather challenging due to the complex interaction between the frame and the infill, partic- ularly in the nonlinear range. Moreover, the selection of the most appropriate model is related to the analysis overall objectives: http://dx.doi.org/10.1016/j.engstruct.2017.07.002 0141-0296/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: nurbaiah.mohammadnoh@alumni.ubc.ca (N. Mohammad Noh). Engineering Structures 150 (2017) 599–621 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct