The effect of different methods of determining the stiffness of stories on seismic performance of steel structures controlled by viscous dampers

Passive control systems have always been used in civil structures due to the lack of external energy source, low cost, easy installation and simple design. The fluid viscous damper is one of the most advanced passive control devices that dissipates the energy input to the structure by converting mechanical energy into heat. In conventional viscous damping design methods, the required damping required to be provided by viscous dampers in the structure depends on the stiffness of the structure. In this paper, in order to distribute the viscous damping at the height of the building, the distribution method is used in proportion to the inter-story drift proportional distribution determined on the basis of the first mode deformations and five different methods for determining the stiffness of the stories are used to calculate the total damping. Finally, of the five methods, the one in which the responses of the controlled building to the viscous damper are more in line with the design goal would be the preferred method. Also, in order to evaluate the design cost to choose the appropriate method, a comparison has been made based on the total damping required (as a cost criterion) to achieve the desired design goal. The studied structures are 3, 9 and 20 story benchmark buildings of SAC project. In order to analyze the time history of buildings, four benchmark near field records with the effect of Fling Step and four benchmark field far records have been used. The results show the different effects of different methods of calculating the stiffness of floors in accordance with the design goal and therefore it is necessary to choose the appropriate stiffness method from different methods to determine the desired design goal.