Analysis On Seismic Response Of Eccentric Structures With Combined Base Isolation

One of the most representative last century of the innovative seismic technology isdamping control technology, it provides new tools and research directions in theearthquake engineering. From which, the base isolation technology is used more widelyin the reconstruction after Wenchuan earthquake in China, the common isolationsystems are: device damper, rubber bearings and friction sliding bearings. However, inour seismic codes, the combination of base isolation and friction sliding bearings are notmentioned, the domestic and international study of the seismic response of baseisolated structure is relatively rare, either. While the previous earthquake damages haveshowed that the seismic response is an important reason for building structural damage,so this paper mainly discuss the seismic response of combined base isolation structure,whose isolation layer is made by a combination of friction sliding bearings and leadrubber bearings.The combined base isolation is used in this paper for a multi-layer eccentricframework structure and a eccentric frame-shear wall structure separately, establishthree-dimensional model of the space structure by SAP2000, choose nonlinearmulti-layer shell element to simulate the shear walls, use the FNA method and theHiber-Huges-Taytor method in direct integration method, analysis the dynamictime-history response of structure, and get the results of structure isolation and torsionalproperties affects caused by the layout program of isolation bearings, the coefficient offriction of the sliding bearings, and the numbers of bearings. For the structures in thispaper, get the results shows that:①No matter eccentric framework structure or eccentric frame-shear wall structure,the impacts of story drift of upper structure and inter-story torision angle affect bylayout program of isolation bearings are relatively small, much less than the results oftraditional non-isolation system. And the horizontal displacement of the isolation layerand torision angle lay more on the layout program of isolation bearings. If there exists astiffness eccentricity, the layer torsional angle will be larger, and the friction slidingbearings should not be arranged in the periphery of isolation layer.②To eccentric framework structure，when the layout program of leader rubberbearings remain the same，the larger of friction sliding bearings coefficient，the smallerof the horizontal displacement of the isolation layer, and the story drift of the upper stories is more larger, while the torision angle of isolation first decreases and thenincreases, and the torsion angle reaches the minimum at the point of friction coefficientequivalent to0.08.③To eccentric frame-shear wall isolated structure, the main torsional deformationof the structure is in the isolation layer, which is the first layer; from the second layer,the maximum inter-story torision angle become small. Easy to see, the torsionalproperties of isolation is so well.Besides, through energy analysis of the impacts of the isolation layer parameters tostructural damping effect of combined base isolation, it has showed that: friction slidingbearings have strong energy dissipation capacity，when combination of isolated, frictionsliding bearings can consume more seismic energy than leader rubber bearings, but notto say the more the better.