Torsion Performance Analysis Of Base-isolated Eccentric Structures

During the long-term persistent fight with earthquake disaster,the isolation technology gradually becomes a new thinking,which decreases the seismic responses by changing the dynamic parameter of structure ,and shows obvious isolation effects and possesses significant social,technique improvement and economic advantages.At present,the structure is usually simplified as single particle system or multitude particle system when designing the base-isolated structure. The assumption of the calculation is that the structure performs horizontal displacement and no torsional displacement. Following the more extensive application of the base-isolation technology and the diversification of the construction style,the structure performs coupling torsional response besides horizontal movement under earthquake action because the quality center does not coincide with the stiffness center,so study about seismic behaviors of base-isolated eccentric structure is of importance whether theoretic or practical.Many factors have influence on seismic torsional effect. The study of the paper only catches hold of one factor—stiffness eccentricity of the isolation storey. In the paper,the parameters for estimate on torsional effect are storey torsional angle maximum , absolute storey angular acceleration maximum , storey torsion maximum, torsional-horsional displacement ratio and so forth.Depending on structure analysis program SAP2000 to establish models which are similar to a base-isolated residential building,the paper first makes a comparison upon the different torsional effect response between base-fixed building and base-isolated building,then discusses the alterable regularity of the structure in torsional effect because of stiffness eccentricity alteration of the isolation storey thourgh regulating horizontal stiffness of the isolation bearing. In the terms of analysis,some meaningful conclusion is put forward as an exploration for restraining the torsional effect of the base-isolated eccentric structure.