Abstract:
A modified friction damper is presented to enhance the performance of conventional friction damper and semi-active variable friction damper. An additional plate is provided between the two sliding plates of a conventional friction damper which results in an additional sliding interface with the same normal (clamping) force. Similar modification is also made to semi-active variable friction damper (SAVFD) to enhance its performance. The enhancement in the performance of the benchmark building is studied under across wind loads by installing the modified dampers. The governing equations of motion are solved by employing state space theory. Optimization of location and number of dampers is also carried out with the help of a controllability index which is obtained with the help of root-mean-square (RMS) value of the inter- storey drift. Further, a parametric study of passive friction dampers by varying slip force is carried out. From the numerical study, it is found that both double friction damper and semi-active variable double friction damper (SAVDFD) are quite effective in enhancing the performance of the benchmark building. At optimized locations, both the proposed dampers give significant enhancement in the performance of the benchmark building.
Keywords: Tall building; passive damper; semi-active control; double friction; wind load
1. Introduction
Various structural control methods like passive control, active control, semi-active control and hybrid control have been studied on different buildings for different dynamic loads. Significant progress has also been made in the area of structural control. Some of the control methods have been implemented for real structures. However, to streamline and focus the study of structural control on the same building with the same load, the concept of benchmark problems has come into picture. Therefore, based on realistic full scale buildings, two structural control benchmark problems have been proposed for earthquake and wind excitations [1]. The wind excited benchmark building is a 76-storey, 306 m concrete office tower proposed for the city of Melbourne, Australia. The building is tall and slender with a height to width ratio of 7.3; hence it is wind sensitive. Wind tunnel tests [2] for the 76-storey building model have been conducted at the University of Sydney and the results of across-wind data are provided for the analysis of the benchmark problem. Performance of various dampers like tuned liquid column dampers [3], liquid column vibration absorbers [4], hybrid viscous-tuned liquid column damper [5], variable stiffness


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