BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică „Gheorghe Asachi” din Iaşi Tomul LVI (LX), Fasc. 4, 2010 Secţia CONSTRUCŢII. ĂRHITECTURĂ THEORETICAL AND EXPERIMENTAL STUDIES REGARDING STEEL–CONCRETE COMPOSITE JOINTS BY DANIEL DAN, VALERIU STOIAN and TAMAS NAGY GYÖRGY Abstract. Theoretical approaches supplemented with an experimental testing program were developed at the „Politehnica” University of Timişoara for a specific steel– concrete composite joint, used into a multi-storey skeletal structure. Starting with the joint type used, two series of joints were tested. Two loading hypotheses of the joint were considered: symmetrical and asymmetrical. For the structures placed in seismic areas the energy dissipation during earthquake is important. The dissipation of energy consists in appearance of plastic hinges located in to the beams. For this study the pursued aim was to obtain the collapse mechanism in the joint panel rather than outside the joint, in order to compare the bending resistant moment of steel joint with the bending resistant moment of composite joint. Using the previsions of EC4 [1], in the theoretical phase the joints were analysed together with their connections – the beams and the columns in order to establish the dimensions of the joint components, thus satisfying the desired collapse mechanism. Also a numerical study was performed in the elastic and post elastic range. Finally the experimental work was performed using special testing equipment and the international recommended testing procedures. This paper presents some aspects regarding the behaviour of steel and steel joints tested. Key words: composite joints; numerical analysis; experimental tests. 1. Introduction Due to the technological process, a composite structure is initially a steel structure. After placing the reinforcement and the concrete casting the structure becomes a composite one. The type of studied joint was used in a multi-storey building in Timişoara, with 12 storeys. The entire structure was built as a steel–concrete composite construction. The structural type is a space skeleton bar structure using plane frames placed on two orthogonal directions,