Original Research Advances in Structural Engineering 1–12 Ó The Author(s) 2016 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1369433216665621 ase.sagepub.com Experimental model for predicting the semi-rigid connections’ behaviour with angles and stiffeners Mahyar Maali 1 , Mahmut Kılıc x 1 , Merve Sag ˘ ırog ˘lu 2 and Abdulkadir Cu ¨ neyt Aydın 1 Abstract This article presents the experimental results of nine specimens of steel bolted beam-to-column connections with top-and-seat angle and stiffener. All of the connections have the angles and beams reinforced with stiffeners in the extended parts. The results are ana- lysed on the basis of the global moment–rotation curves. The main parameters observed are the failure modes, the evolution of the resistance, the stiffness, the rotation capacity, the ductility of a joint and the energy dissipation. The aim was to provide necessary data to improve the Eurocode 3. While the stiffness decreased with the increased thickness of beam stiffeners of 5–10 mm, the maximum bending moment (M j.max ) increased with the increased length of top-and-seat angle. Keywords beam stiffeners, energy dissipation, Eurocode 3, experimental testing, resistance, semi-rigid connections Introduction The behaviour of beam–column joint plays an impor- tant role in the response of a steel moment resisting framed structure (Babu and Sreekumar, 2012). The use of bolted joints allows more energy dissipation and provides a good response under static loads. In the structural framework with semi-rigid joints, the char- acteristics of connections play a significant role in the resistance, the stiffness, the rotation capacity, the duc- tility of a joint and the energy dissipation mechanisms. As rigid connections are more expensive and difficult to assemble and because flexible connections do not have the necessary resistance and stiffness to resist the static loads, use of semi-rigid connections using bolted angles is justified (Babu and Sreekumar, 2012). In recent years, a number of research works were carried out to study the behaviour of semi-rigid connections. Cabrero and Bayo (2007) researched the semi-rigid behaviour of three-dimensional steel beam-to-column joints subjected to proportional loading. An experi- mental investigation of statically loaded extended end- plate connections in both major and minor column axes was undertaken. The aim of the research was to provide insight into the behaviour of these joints when a proportional load is applied to both axes (three-dimensional loading). Shi et al. (2007) investi- gated the experimental and theoretical analyses for the moment–rotation behaviour of stiffened extended end- plate connections. A new theoretical model for evalu- ating the moment–rotation (M–u)relationship for stif- fened and extended steel beam–column end-plate connections was derived. Based on a specific definition of the end-plate connection rotation, the end-plate connection was broken down into several components, including the panel zone, bolt, end-plate and column flange. Abidelah et al. (2012) researched the experi- mental and analytical behaviours of bolted end-plate connections with or without stiffeners. The results were analysed on the basis of global moment–rotation curves and the evolution of the tension forces in the bolts. The main parameters observed were the failure modes, the evolution of the resistance, the stiffness and the rotation capacity. When beam-to-column joints to the column minor axis were considered, the adopted design process generally assumed these joints to be 1 Department of Civil Engineering, Faculty of Engineering, Ataturk University, Erzurum, Turkey 2 Department of Civil Engineering, Faculty of Engineering, Erzurum Technical University, Erzurum, Turkey Corresponding author: Abdulkadir Cu ¨neyt Aydın, Department of Civil Engineering, Faculty of Engineering, Ataturk University, Erzurum 25240, Turkey. Email: acaydin@atauni.edu.tr