The use of multistorey composite structures (steel columns, steel beams, and reinforced concrete slabs) became a necessity. The multi storey composite structures are used for different types of buildings such as office buildings, bank buildings, industrial buildings, public buildings, high-rise parking buildings, etc. These kind of buildings can be seen around the world, in the highly developed countries depicting their financial and technical power. The safety and function expressed through control of the mass, stiffness, strength, and ductility at the structural design of the multi storey composite structures, and mostly of the connections of the elements exposed under cyclic-horizontal loading (such as earthquake, wind loading) in combination with other loading is of highest priority for this kind of structures. The behavior of the beam-column connections in the multi storey frame structures (MSFS) is viewed as a whole and it’s in direct correlation and dependence with the behavior of their main constructive fundamental elements (steel deisgning courses in kerala beams, columns and the elements for their connection) . In other words, the way the beams, the columns and their elements of connection behave, that way the MSFS behaves. The behavior of the beam-column connection in the MSFS again is dependent on the constructive solution. However, dominant in this paper is the research of new or modified constructive solutions of the connections, and all with the purpose of improving their loading capacity in conditions of real external loading. Some constructive solutions can be controlled by the dissipation of energy, meaning,they can be controlled by the stress and deformation distribution in the sections of the elements of the MSFS i.e. the constructive solution of the connection directly influences the appearance of the plastic hinges in some of the sections of the elements, when their loading capacity is exhausted. In the numerical modeling of the beam-column connection the demands of the new codes ,, are incorporated, which is the well-known concept of the seismic resistant structure that proposes development of plastic hinges in the beams, and columns.
Consequently, the size of the static influence that dictates the order of the plastic hinge appearance should be taken under consideration i.e., column bending strength should be larger then beam bending strength. With the alternative of the collapse mechanism (the order of the element’s plastification) and generally the mechanism of energy dissipation, two different approaches exist: The first approach is based on the contribution of the panel–zone in the energy dissipation with the purpose of its reduction and also accepting a part of the plastic deformations, without excluding the contribution of the columns and the beams. The second approach does not include the panel zone in the energy dissipation. As a result, the end parts of the beam must accept the plastic deformations. Thus the beam–column connection can be specified in detail. During design of connections it is important to control the weight, stiffness, strength and the ductility of the material of the elements. This is due the fact that their behavior depends on the mentioned parameters of the elements in the connections . The deformation (rotation) capability is inversely proportional to the capacity of carrying of the beam i.e. the semi rigid connections have bigger plastic deformations and possibility for bigger rotation during the use of their total capacity to carry, but they have smaller capacity to carry comparing to the ones with rigid connection.