Fatigue Behavior of Steel Slit-Dampers With Various Shapes

Abstract eng:
Passive control structural systems with seismic dampers have achieved significant progress in recent decades. In this structural system, dampers dissipate most of the earthquake-induced energy to minimize damage to the parent structure. Steel slit-dampers, which are known to have stable and large energy dissipation capacity, are a type of such hysteretic dampers. This kind of dampers is fabricated by simply cutting slits on steel plates, leaving a number of strips in between. All slits are rounded at their ends to reduce stress concentration. High tension bolts are set at the end of the plates to connect the dampers to the parent structures. Each strip behaves as a fixed-ended beam and deforms in double curvature, while plastic hinges form at the end of the strips to dissipate energy under deformation. Slit-dampers are light-weight and can be easily set and replaced at various locations in the structures where necessary. By changing the shape of the damper, its stiffness and strength can be adjusted to different levels to meet the needs of structural design. Research has been done related to slit-dampers’ low cycle fatigue behavior and hysteretic characteristics. Cyclic loading tests were performed, which demonstrated the dampers’ stable hysteretic behavior and adequate energy dissipation capacity. Nevertheless, in most of the current research work, only slit-dampers with very limited geometries were studied, while “shape” is one of the most important variables in the design of the structures with slit-dampers, which would strongly affect the fatigue behavior/plastic deformation capacity of the dampers. In order to achieve desired structural performance, slit-dampers with suitable sizes for a structure should be chosen considering the structure response under various types of earthquakes. A practical design guideline for structures with slit-dampers is necessary. However, there is no such design guideline at this moment to facilitate the implementation of this device. For the purpose of establishing a design guideline for slit-dampers, it is necessary to clarify how geometric shapes affect the fatigue behaviour of slit-dampers. In this paper, experimental study of slit-dampers with various shapes was carried out. Basic information of the influence of geometries on the behavior of slitdampers is obtained from the tests. However, it is impossible to cover all the shape parameters in the experiments. Therefore, based on the previous experimental study, FEM analyses of slit-dampers with various shapes were also conducted. The equivalent strain amplitude at the fracture zone (toe of the strip where the ductile cracks start) is studied through the analytical results. For dampers with different shapes, the relationship between the equivalent strain amplitude and the number of loading cycles until the ultimate state of a slit-damper was found following the Manson-Coffin law. The influence of geometry on the fatigue behaviour & energy dissipation capacity of steel slit-dampers was evaluated based on the experimental and analytical results.

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