Kim, Choi, and Min 2010
This paper explains a combined system of rotational friction dampers, which are connected to high strength tendons to improve both seismic and progressive collapse-resisting capacity of existing structures. The writers discuss supplemental damping in conjunction with appropriate stiffness, which is an economical solution for the seismic rehabilitation of structures when compared to conventional methods, like concrete shear wall and rigid steel frame bracing. Friction dampers are considered one of the most efficient energy absorbing devices that can be installed in structures to resist earthquake loads. First, installation of friction dampers is explained, followed by the design and analytical model of a sample structure. Finally, the paper discusses collapse performance of retrofitted structures.
System Concept
In these friction dampers, two side plates and two circular friction pad discs are placed in between steel plates. The central plate is attached to the girder midspan in a framed structure by a hinge and the ends of the two side plates are connected to the members of an inverted V-brace. In order to avoid compression stresses and subsequent buckling, the bracing includes pretensioned bars. The bracing bars were pin-connected at both ends to the damper and to the column bases. The combination of two side plates and one central plate increases the frictional surface area, while also providing symmetry needed for obtaining plane action of the device. The bolts control the compression force, applied on the interfaces of the friction pad discs and steel plates. The girders displace horizontally when a lateral force is applied to the structure. In other words, when the structure undergoes lateral deformation, the friction dampers are activated and start dissipating energy. The forces transferred through the structure can be reduced considerably by means of dampers; since the dampers dissipate a major portion of the seismic energy.
Experimental Study, Results, and Discussion
Design procedures were determined by considering the required effective damping ratio and the frictional moment of the friction damping device. In order to validate the design process of the dampers, 3, 6 and 15-story reinforced concrete model structures were designed considering only gravity loads in OMRF and with seismic loads included in SMRF. OpenSees was used for the analyses.
Nonlinear dynamic time-history analysis results show that the structures retrofitted with rotational friction dampers generally satisfied the given performance objectives under seismic loads. It was observed that the displacement responses decreased significantly with the addition of the dampers that exhibited stable hysteretic behavior and dissipated a large amount of seismic energy.
Reference
Kim, J., Choi, H. and Min, K.W. (2011). “Use of Rotational Friction Dampers to Enhance Seismic and Progressive Collapse Resisting Capacity of Structures,” The Structural Design of Tall and Special Buildings 20, pp. 515-537.