THE STEEL COLUMN DAMPER: A NEW HYSTERETIC DEVICE PROVIDING ADDITIONAL STIFFNESS AND DAMPING

Over the years, with the scope of minimizing structural damage, several dampers were developed [1-2] and new replaceable hybrid composite steel devices [3] have been recently proposed. The aim of this paper is to propose and investigate a new replaceable hysteretic damper having a basic form of the art of building, minimally architecturally invasive, consisting of two or more dissipative steel columns directly connected to two consecutive floors linked to each other with X-shaped low/mild steel plates. The proposed Dissipative Column (DC) models are shown in Fig. 1 for two different end cases (models A, B). The elements can be considered as a sort of framed bi-pendulum, connected in parallel to the primary structure, able to react to the story drift D with a lateral force QD adding stiffness, strength and damping. The design concept of the DC element aims to obtain a lever mechanism by which a small inter-storey drift provides an amplified vertical drift in the Xplate ends reacting with shear forces, (Fig. 1 c)). X-shaped steel plates made of mild or Low Yielding Strength (LYS) steel [4] are also used as shear links between coupled elements. The top ends of two models are linked to upper floor through slotted bolted connections to allow vertical displacements. By yielding a large volume of steel, the shear devices dissipate substantial input energy under earthquake or strong wind also increasing damping in the entire system.The great advantages of DC elements, if compared with classical dissipative brace, are the reduced architectural invasiveness so that they are able to be integrated in any building, the ease of installation everywhere, their replacement after earthquakes and the stable behavior in cyclic reversal deformation. Axial forces should be designed in ordered to be transferred locally to a proper structural element.