ENERGY ABSORBING ELEMENTS IN REGULAR AND COMPOSITE STEEL FRAME STRUCTURES

Intensive investigations in the field of the control of structural beh aviour have been conducted at the Institute of Earthquake Engineering and Engineering Seismology in Skopje. Part of them, relating to energy absorption elements are presented in this paper. In order to provide a more sophisticated presentation of the characteristics and capabilit ies of these energy absorption elements, a short review of the current ly available and most frequently applied passive control systems is in cluded. To prove the efficiency of the energy absorption elements quas istatic tests on single-span models CR10 and CR20 of the characteristi c frame have been performed. The results proved that the CR20 models a re of considerably higher strength, even six times higher at ultimate state, ductility and energy dissipation capacity. A mathematical model has been formulated for the nonlinear behaviour of the main elements of the system, whereby a trilinear P-Delta diagram has been used, as d eveloped at the Institute. The analysis of the hypothetical prototype, a five-storey building, with energy absorption elements incorporated in six spans, subjected to the seismic excitations of two PGA levels, 0.12 g and 0.15 g, has shown very good results. Further investigations in this field resulted in the development of new energy absorbing ele ments (through friction), SEC, which when placed at the joints of the frame introduce hysteretic damping to the structure in the case of low level excitations, when the rest of the system is in the linear range .