The 12th International Symposium on Fiber Reinforced Polymers for Reinforced Concrete Structures (FRPRCS-12) & The 5th Asia-Pacific Conference on Fiber Reinforced Polymers in Structures (APFIS-2015) Joint Conference, 14-16 December 2015, Nanjing, China SEISMIC RETROFITTING OF A THREE-STOREY MASONRY- INFILLED RC FRAME WITH TEXTILE-REINFORCED MORTAR (TRM) Lampros N. Koutas 1 , Thanasis C. Triantafillou 2 and Stathis N. Bousias 3 1 Faculty of Engineering, The University of Nottingham University Park, NG7 2RD, Nottingham, United Kingdom Email: Lampros.Koutas@nottingham.ac.uk 2 Department of Civil Engineering, University of Patras Patras, GR-26500, Greece Email: ttriant@upatras.gr 3 Department of Civil Engineering, University of Patras Patras, GR-26500, Greece Email: sbousias@upatras.gr Keywords: Analytical modelling, Infilled frames, Large-scale testing, Masonry infills, Reinforced concrete, Seismic retrofitting, Textile-reinforced mortar (TRM) ABSTRACT The effectiveness of using textile-reinforced mortar (TRM) as a means of improving the mechanical behaviour of reinforced concrete (RC) or masonry elements has been experimentally verified in the recent past. In this study TRM was employed for the first time in the case of substandard masonry-infilled RC frames representing structural detailing of the 60s-era in Southern Europe. For this purpose cyclic tests on two nearly full-scale three-storey RC frames were conducted. The structure was subjected to a linear pattern of cyclically alternating forces through servohydraulic actuators. The performance of the retrofitted specimen was compared to the performance of the unretrofitted companion specimen. The test results demonstrate that the proposed strengthening technique considerably enhances the lateral strength, the lateral stiffness and the deformation capacity of the frame. An analytical model to simulate the response of TRM retrofitted masonry-infilled RC frames is also provided. 1 INTRODUCTION Past experience has shown that masonry infills in substandard reinforced concrete (RC) buildings play a key role in their behaviour under seismic excitations. This role can either be beneficial for the overall response of the structure, or can have catastrophic consequences. An overstrength is usually provided by the infills, given that they do not cause adverse effects on the frame members or on the structure as a whole. Nevertheless, masonry infills cannot be considered as reliable structural elements because they suffer damage even since early stages of strong earthquakes, shedding rapidly their strength and stiffness and becoming vulnerable to collapse. In this context, retrofitting masonry infills aims to convert them from non-structural to structural elements by applying external layers of reinforcement and by connecting them to the surrounding RC frame members. Various retrofitting techniques have been proposed in the literature as alternative solutions to conventional ones that make use of steel-mesh reinforced shotcrete layers. The most recent techniques include the application of fiber-reinforced polymers (FRP) (e.g. [1, 2]) and sprayable ductile fiber- reinforced cementitious composites (e.g. [3]). The retrofitting technique proposed in this study is based on the application of textile-reinforced mortar (TRM), which is a composite material comprising high-strength open-mesh fiber textiles as reinforcement in combination with inorganic matrices (i.e. cement-based mortars). The concept of the technique relies on the application of TRM layers on the