Oil dampers installed on the first floor of an eight-story steel building were completely destroyed during the 2011 Great East Japan Earthquake. It is believed to be the first time in the world that real oil dampers in service failed due to earthquakes. Before this failure event, the actual performance of buildings that use oil dampers during catastrophic earthquakes has never been verified. Investigating the cause of the damage of the oil dampers is thus necessary and urgent. In this paper, a comprehensive identification was conducted to rebuild the numerical model of this damped structure equipped with/without damaged oil dampers using the measurement data of the installed monitoring system. Furthermore, the damage process of the oil dampers was postulated based on the identification and simulation results. The limit states of the oil dampers were studied. Based on the damages of the dampers and connection, the oil dampers experienced the displacement limit state when the allowable displacement limit was surpassed and the central cylinder pushed against the abutment. The insufficient stroke limit is the main cause of the collision between the damper and the abutment on the floor, which finally led to the failure of the oil dampers.
In this paper, the full rehabilitation process of a damaged passively controlled building is reported. A hybrid retrofit plan that uses tin-rubber bearings to replace the damaged oil dampers is proposed and tested within the size requirement and cost budget. Structural Identification and nonlinear dynamic analyses have been conducted to verify the effectiveness of the hybrid retrofit plan. After the rehabilitation was completed, the retrofitted building with tin-rubber isolators is proved by a recent earthquake to have a better seismic performance than the original building with oil dampers. Finally, the performance of the damping system will be discussed in this paper based on the performance-based design concepts. The performance level of the energy dissipation devices should be set accordingly based on the building performance level for the seismic rehabilitation design. The safety issues of the structural frame and retrofit procedure after the failure or degradation of the damping devices should be investigated in the future.
� In developing countries of seismic area, many people have to live in traditional masonry houses of adobes, bricks, stones and concrete blocks.Though collapse of the houses is one of the most tragic losses of human lives, shift of the houses to construction based on modern engineering is difficult by socioeconomic reason. The authors have been developing a rocking pillar base isolation system suitable for masonry houses.Seismic performance of the system was discussed by vibration test of reduced scale specimen in the previous paper. In this paper, shaking table tests and time integration method of the system are summarized. Based on the obtained test results, effectiveness of mass-eccentricity of superstructures on seismic performance of the system is discussed. Also, accuracy of the analytical method is demonstrated via numerical simulation of the shaking table test.
The authors have been designing a post-installed anchor that fixes itself into concrete material by expanding the anchor tip in an upward direction, and conducted tensile loading tests to confirm its fundamental dynamic characteristics. The test results on three types of test specimens, with anchor morphology as a parameter, indicate that the final failure modes were all anchor bar fractures, and a stable yield strength was confirmed. Additionally, the yield strength characteristics of the proposed anchor in cases where cracks are present on the concrete surface, wherein the anchors are fixed, were experimentally confirmed.
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