A new design strategy for optimal distribution of dampers in smart building structures

A new strategy for structural control systems using viscous dampers is proposed. When we use some energy absorption devices, such as viscous dampers, in a building structure, the devices are uniformly distributed over the building so that the input energy should not concentrate in a specific story. However, this design strategy is not always the optimum one. A unique strategy that does not utilize the uniform distribution of dampers is presented here. Many advantages exist in the system that does not have uniformly distributed dampers. First, in the stories which do not require dampers, more freedom for using the floor space is possible. In addition, this fact results in lowering the cost as well by allocating the dampers to limited stories. By simplifying the flow of energy absorption, the structural reliability is significantly improved. The simplified energy flow in the structure will enhance the feasibility of the structural health monitoring system. In this paper, it is also shown that by softening appropriately the stiffness of the story to which dampers are installed, it is possible to raise the energy absorption efficiency without causing concentration of the drift. We define the modal concentration ratio using complex modal vectors to obtain optimal story stiffness and the capacity of viscous dampers for achieving the desired damping ratio. The performances of the systems were carefully evaluated by conducting nonlinear dynamic response analyses subject to several large earthquakes. The analysis models for the structures were the lumped mass models considering shear deformation. The dampers attached to the structure were modeled as Maxwell models to incorporate the stiffness of the supporting members.