PERFORMANCE DETERIORATION OF SLOTTED-BOLTED CONNECTION DUE TO BOLT IMPACT AND REMEDY BY RESTRAINERS
The behaviour of slotted-bolted connections when the maximum slip travel exceed the available slot length is presented. The drastic degradation behaviour of slotted-bolted connections under bolt impact is demonstrated. Remedy by means of the concept of restrainers is proposed, which is also advantageous in suppressing the build-up of resonance motion by virtue of the change in system stiffness at different stages. Nonlinear dynamic analyses were performed on a prototype 6-storey steel building equipped with friction dampers with and without restrainers. Three historical earthquake records from California, i.e. the 1989 Loma Prieta, the 1966 Parkfield, and the 1940 El Centro records, were considered in the analyses. In the worst loading case, dampers with restrainers are superior to that without restrainers, resulting in reduction of the peak inter-storey drift by 16% and the peak slip travel by 15%. The shorter slip travel obviously provides extra safety to the system. Increasing the maximum restraining force is generally beneficial in reducing the peak inter-storey drift. However for steel bracings, the restraining force limit should be kept sufficiently below the buckling capacity to avoid buckling of the bracings. Furthermore, a higher restraining force would induce higher storey base shear. Hence, the adequacy of the foundation has to be properly addressed as well in retrofitting of buildings.
A state-of-the-art review on passive friction dampers and their applications
Abstract This paper presents a state-of-the-art review on friction type passive energy dissipation devices. Friction dampers are highly preferred as an energy dissipation device, particularly for the seismic fortification of the engineering structures due to their simplicity, reliability, and maximum energy dissipation as a result of the generation of rectangular hysteretic loops. Additionally, their performance is not significantly influenced by the loading amplitude, frequency, and the number of cycles. Hence, with a better understanding of friction mechanism and behavior, numerous novel passive dry friction dampers have been invented and applied in the field of civil engineering since 1980. However, decades of studies over these dampers are highly scattered throughout the academic community. Hence, the availability of many valuable pieces of research is out of reach for further studies. Therefore, a holistic chronological detail of advancement (development and application) in the field of passive friction dampers has been presented systematically in this study. The major purpose of this paper is to present an integrated and holistic overview of passive friction damper for the ease of further studies and generate future research directions for researchers who will be working in this field.
Performance Evaluation of Friction Damped Braced Steel Frames under Simulated Earthquake Loads
This paper presents the results obtained from tests of a new friction damping system, which has been proposed in order to improve the response of steel Moment Resisting Frames (MRF) and Braced Moment Resisting Frames (BMRF) during severe earthquakes. The system consists of a mechanism containing brake lining pads introduced at the intersection of frame cross-braces. Seismic tests of a three storey Friction Damped Braced Frame (FDBF) model were performed on an earthquake simulator table. The experimental results are compared with the findings of an inelastic time-history dynamic analysis. The results clearly indicate the superior performance of the FDBF compared to conventional building systems.