ASEISMIC ROOF ISOLATION SYSTEM BUILT WITH STEEL OVAL DAMPERS

摘要

Presented here are the details of and results from experimental and analytical studies conducted to assess the feasibility and effectiveness of a proposed roof isolation system whose purpose is to reduce the seismic response of buildings. The proposed roof isolation system entails the detachment of a building's roof through the insertion of a low-friction mechanism and the attachment of oval-shaped steel dampers placed between the detached roof and the structure below. The objective is to form a simple resonant oscillator with the building's roof and these oval dampers, where the roof provides the oscillator's mass and the oval dampers its spring and damping elements. An additional objective is to induce a large number of inelastic deformation cycles into the oval dampers and make them, as a result, dissipate a large portion of the energy transmitted to a building during an earthquake. Through their stable hysteretic behavior, steel oval dampers have been found to work effectively as energy dissipating devices. In the experimental study, a small five-story steel frame is tested on an earthquake simulator alternatively with and without the proposed roof isolation system. Then, a comparison is made between the peak floor accelerations and story drifts induced in the frame in each case. In the analytical study, a typical thirteen-story building is similarly tested through numerical simulations. In both studies, the tests are conducted under the effect of different earthquake ground motions. In both studies, too, it is found that the proposed roof isolation system is effective in reducing the seismic response of the tested structures. It is concluded that the investigated system has the potential to become an inexpensive and effective way to protect some buildings against earthquake effects and reduce, as a result, the amount of structural and nonstructural damage they may experience during a strong earthquake.