Ke, Chen, Zhou, Yam, Hu, 2023
A new brace-type hybrid damper (BTHD) with steel slit plates that utilizes friction mechanism was introduced in this study. The damper was designed to achieve improved ductility and energy dissipation in comparison to traditional steel slit plates. Both experimental study and numerical analyses were carried out to verify its seismic performance. Six specimens of the proposed model were tested, demonstrating satisfactory responses such as high energy dissipating capacity and hysteretic curves under cyclic loading. This was further supported by its numerical results and finite element modeling analyses. It was denoted that the proposed damper exhibited multi-stage energy dissipation characteristics and also conveyed a significant relationship between its friction mechanism and the geometric parameters of the steel slit plates. Overall, the proposed damper demonstrated a promising seismic performance with satisfactory hysteretic behavior and energy dissipation.
System Concept
The proposed brace-type hybrid damper (BTHD) is made of a steel slit plate with friction dampers between its two rows of slits. The steel slit plate also consists of slotted holes in the panel zone that allows connection with the cover plate of the channel and creates an interface for friction. The study included two different types of dampers with different mechanisms: “frictional-metallic” (FM) type damper and “metallic-frictional” (MF) type damper. In the FM type damper, the friction energy dissipation is activated before the edge of slotted holes pushes the bolts, then resulting in yielding of the strips. As compared to MF type damper, it allows the applied force to yield the steel strips before the friction dampers dissipate energy as the cover plate slides begin to slide. Both mechanisms contribute to a ploughing effect that causes an increase in nominal friction coefficient and hysteretic hardening of the dampers. The properties of the BTHD can be altered by changing its different factors including the length of the slip range, the clamping force of the high-strength bolts on the cover plates, and the coefficient of friction on the interface, the geometrics of the steel slits and type of material for the other components of the system.
Experimental Study, Results, and Discussion
Five specimens of the proposed damper and a conventional steel slit plate damper were investigated on their energy dissipating behavior and compared for analyses. The test set-up includes the specimen in a horizontal position and a 2000 kN hydraulic jack connected to the channels. The test ensured only in-plane displacement loads by equipping a self-equilibrium frame that is secured to the strong floor. For monitoring purposes, strain gauges were also attached on the steel slit plate damper. The specimens underwent three stages of cyclic loading protocols at two cycles for each amplitude until failure is observed. According to the results of the experiments, it was observed that the ductility of the specimens was greatly influenced by the sequence of the energy dissipation mechanism. FM damper, which activates friction damper before yielding, has higher ductility in contrast to MF damper even though they have similar ultimate strength. Likewise, due to its stable energy dissipating mechanism, the FM damper also has a higher energy dissipating capacity compared to specimens with MF sequence mechanism. The test overall proved that the hybrid energy dissipation mechanism in the novel damper effectively enhanced the energy dissipation capacity and ductility compared to conventional steel slit plate dampers which is further validated by the numerical studies.
Reference
Ke, K., Chen, Y., Zhou, X., Yam, M. C. H., & Hu, S. (2023). Experimental and numerical study of a brace-type hybrid damper with steel slit plates enhanced by friction mechanism. Thin-Walled Structures, 182, 110249.