Steel structures in seismic zones are designed for stiffness, strength and ductility. Stiffness is required for limitation of damage of non-structural elements and reduction of the second order effects. Strength is required for a safe transmission of the acting forces and moments. Ductility under cyclic loading leads to the dissipation of the input seismic energy and results in a reduction of the seismic forces. In such structures, energy absorption is accomplished through plastic deformation in certain areas called plastic hinges. Repairing damage after earthquake is very costly, time consuming and sometimes impossible. Given the slow pace of structural repair and retrofit to cope with future earthquakes, the idea of using a control systems in a structure has been proposed. Passive control systems are among the most common and cheapest form of damage control systems. In these systems, input earthquake energy dissipation, is concentrated in special devices with good and stable hysteresis behavior. Different types of energy dampers, developed and used in structures. In this study, a new visco-plastic damper is developed. This damper have been uses viscoelastic material properties and yielding of metallic materials for energy dissipation. The proposed damper is high speed in installation and repairing process after experiencing a strong earthquake. By using this damper in beam to column moment connection, plastic deformations can be prevented in the main structural elements such as beams and columns. the proposed connection systems, the stiffness, strength and energy dissipation capacity remains at an acceptable level with respect to conventional moment connections. To ensure proper behavior of damper under cyclic loading an example of the damper is built and tested. To determine the behavior of the rubber layer, in two of the experiments, the damper has been built with no steel element dissipator. Also, two specimens armed with steel yielding elements made of low carbon steel and stainless steel (A304L) under cyclic deformation has been tested. In each case, the damper response as force - deformation curves are derived and presented. Then, to determine the behavior of proposed connection, this connection system is simulated with ABAQUS and a parametric study is done. In each finite elements sample, moment-drift and energy dissipation curves in the proposed system are presented. It is shown that by using the proposed connection system, can be maintain the stiffness, strength and ductility are maintained at the desirable levels and the structure is prevented from seismic damage. In addition, good hysteresis behavior and high speed in repairing provides a high potential for its use in design of steel structures.
Keywords: passive energy dissipation, visco-plastic damper, steel moment connection, energy dissipation