Introduction of New Steel Slit Dampers with Elliptical Slit in Bracing Connection and Comparison with Steel Slit Dampers with Constant Slit Width by Experimental and Numerical Study

Controlling systems are modern systems of designing structures that have become widely used in the building industry today. One of these control systems is the use of a damper. These systems can be generally categorized into active, inactive, semi-active, and hybrid systems. Among the mentioned systems, the inactive dampers do not require the use of an external power source. Contrary to conventional methods of designing earthquake resistant structures in which major earthquake energy is absorbed by the yielding of specific points of the structure (typically, the ends of the beams and columns in the moment frame systems), in inactive control systems, the major part of this energy is absorbed by certain devices which are called seismic dampers. One of these types of dampers, which can be replaced after damage from large earthquakes, is the Steel Slit Damper (SSD). Steel slit damper is a kind of inactive energy depreciator with behavior dependent on displacement. Steel Slit dampers are mainly made of metal or special alloys that are easily yielded and have an acceptable performance to dissipate energy under severe seismic loads. In these dampers, the blades between the slits dissipate seismic energy by absorbing non-elastic deformations and prevent it from being transferred to the main structural members.

In this study, an investigation on the experimental behavior of steel slit dampers was performed. One specimen was considered as a reference without any slit, 4 specimens had slit with constant width and cross section but different height and 3 specimens had elliptical slit with constant cross-section and different height. Cyclic loading was applied to all the specimens in the form of displacement control and the results of experiments such as load capacity, absorbed energy, stiffness, ductility and damping were presented and compared. In addition, a numerical study was performed by finite element software (ABAQUS) and the results showed a good correlation in comparison to experimental results. The experimental study showed that elliptical split dampers had better performance in terms of bearing capacity, ductility and energy absorption, with a mean increase of 73.76%, 15.91% and 129.49%, compared to slit steel dampers with constant width, respectively. A noticeable point about the steel dampers with an elliptical slit was that in addition to increasing the bearing capacity, the displacement capacity, as well as ductility, increased, while in the dampers that have been investigated, the simultaneous increase in load capacity and ductility has not been found. Also in dampers with an elliptical slit the more length of slits participated in energy dissipation, strength and stress tolerance compared to the dampers with constant width. According to the experimental and numerical results obtained from this study, it can be concluded that the use of elliptical slit dampers with respect to the performance in terms of bearing capacity, energy absorption, ductility, and displacement capacity, has a significant effect on seismic performance improvement in comparison to dampers with constant slit width. In these dampers (with elliptical slit), the ratio of height to slit width (h/b) equal to 4.85, has shown the best performance compared to other h/b ratios