Shaking table test of a damped-outrigger system incorporating friction dampers

The main purpose of this study is to investigate the seismic performance of a damped-outrigger system incorporating friction dampers through numerical analysis and shaking table tests. A 9-m-tall steel structure specimen was designed by scaling down a 20-story benchmark model. The specimen was equally divided into 10 floors; the outrigger beams together with the friction dampers could be installed in different floors. The normal force in the friction damper was adjustable so that its energy performance could be modified during the test. The seismic response of the specimen was evaluated by performing response spectral analysis (RSA) using the OpenSees numerical model. The equivalent damping ratio was included in the RSA to evaluate the energy dissipation resulting from the friction dampers. Based on the RSA results, the specimen configurations when outrigger was located at the sixth (6F), eighth (8F), and roof floors (RF) and when the normal force in the friction damper varied between 5, 10, and 20 kN were tested by imposing five different ground motions with the peak ground acceleration of 0.64g. Both the RSA and test results indicated that the maximum roof drift of the specimen was around 0.7, 0.4, and 0.3% rad., when the outrigger was located at the RF, 8F, and 6F, respectively. The greater normal force applied in the friction damper generally result in a greater amount of energy dissipation and a smaller roof drift response. Based on the experimental and numerical results, the optimal design of the damped-outrigger system incorporating friction dampers are demonstrated in this study.