Study On Torsional Design And Seismic Vulnerability Of Base-isolated Structures

In recent years,people's requirements for living and living environment have continuously increased.In order to meet the design requirements,there are more and more irregular planar buildings.Seismic damage investigation and theoretical research show that,due to the misalignment of the center of mass and rigidity of the planar irregular structure,the obvious torsional response under the action of earthquakes is one of the direct factors leading to severe damage to eccentric structures.Therefore,it is of great practical significance to study the problem of torsional coupling control of eccentric structures.Aiming at the characteristics of eccentric structures that are prone to torsional failure and poor seismic performance under the action of horizontal earthquakes,this paper combines the basic isolation technology and the torsional displacement ratio with inter-story displacement and floor displacement as indicators to evaluate the torsional effect of the structure.The eccentricity of the isolation layer is the control variable,and the torsional displacement ratio is used as the structural torsional response index.When the eccentricity of the upper structure exists,the eccentricity of the working conditions can be obtained by adjusting the position of the rigid center of the isolation layer.The torsion design of the eccentric structure is proposed,and a torsion design method suitable for the eccentric structure is proposed.The torsional design method proposed in this paper is used to complete the isolation design of eccentric structure.The inter-layer displacement angle and inter-layer torsion angle are used as performance indicators.The seismic vulnerability analysis method is used to analyze the seismic vulnerability of three eccentric base-isolated structures.,And draw the seismic vulnerability curve to evaluate base-isolated structure.The main research contents are as follows:(1)Torsional design method of eccentric base-isolated structureAiming at the eccentric base-isolated structure,the elastoplastic time-history analysis method is used,and the torsional displacement ratio is used as the torsional response index.When the eccentricity of the upper structure exists,the eccentricity of the rigid center of the isolation layer is adjusted,and the torsional resistance of the design method eccentric base-isolated structure is proposed.The results show that: when the superstructure is severely eccentric in one direction,the rigidity of the isolation layer and the rigidity of the superstructure should be placed on both sides of the center of mass,and the eccentricity of the isolating layer should be close to the eccentricity of the superstructure;In the case of severe eccentricity in both directions,the rigidity of the isolation layer and the rigidity of the superstructure should be arranged on both sides of the center of mass.the eccentricity of the isolation layer should be increased as much as possible to make the isolation Layer rigid center,away from the center of mass of the superstructure.(2)Isolation design of eccentric structureFor two-way slightly eccentric structures,the torsional effect of the upper structure is significantly reduced in accordance with the design principles of seismic isolation given in the "Resistance Regulations".At the same time,the torsional displacement ratio of the isolation layer is less than 1.2.Plane symmetrical structure.For one-way severe eccentric structure and two-way severe eccentric structure,according to the torsional design method proposed in this paper,the torsional effect of the superstructure is significantly reduced,and the horizontal seismic action of the superstructure can be reduced by one degree for structural design.(3)Analysis of seismic vulnerability of eccentric base-isolated structuresThe torsion design method proposed in this paper is used to isolate the eccentric structure.The seismic vulnerability analysis method is used to analyze the seismic vulnerability of the eccentric base-isolated structure.The inter-layer torsion angle are used as performance indicators.Seismic vulnerability curve.The research results show that: for eccentric base-isolated structures,the probability of damage to the isolated layer is greater than that of the upper structure,and the isolated layer is more likely to break;for slightly eccentric or symmetrical structures with a torsional displacement ratio less than 1.2,the inter-layer displacement angle is used as an indicator The vulnerability curve is higher than the vulnerability curve with the inter-layer torsional angle as the index,the torsional displacement ratio is greater than 1.2 for severely eccentric structures,and the vulnerability curve with the inter-layer torsional angle as the index is significantly higher than the inter-layer torsional angle as The vulnerability curve of the index has a greater probability of overtaking with the inter-layer torsion angle as the index,and it is safer to select the inter-layer torsion angle as the performance index to study the seismic performance of the eccentric base-isolated structure.