Novel Semiactive Friction Controller for Linear Structures against Earthquakes

Semiactive friction dampers (SAFD) have been shown to be more effective than passive friction dampers in reducing structural response due to earthquakes. The effectiveness of SAFD, however, depends on the control strategy used. Because of the nonlinear nature of friction dampers, the establishment of an effective control strategy is a challenging effort. The motion of friction dampers, either passive or semiactive, involves sticking and slipping phases. The idea for increasing the performance of SAFD is to maintain its motion in the slipping phase as much as possible, as energy is dissipated during the slipping phase rather than the sticking phase. In this paper, the authors propose control strategies which are capable of: 1) maintaining the motion of SAFD in the slipping phase as much as possible; and 2) eliminating the undesirable acceleration spikes by introducing an appropriate boundary layer in the control strategy. Two structures, a 6-story base-isolated structure and a 3-story fixed base building model, were used to demonstrate the performance of the proposed control strategies using different far-field and near-field earthquakes. Further, the performances of various combinations of passive and semiactive energy dissipation devices have been evaluated and compared. Based on numerical simulation results, it is demonstrated that the proposed semiactive friction control strategies are very effective.