Torsion Effect Analysis Of Structures On The Slope Under The Inputs Of Two-Dimensional Seismic

Since the embedding end of structures on the slope not at the same height,it will cause the mass center and the stiffness center have a far distance,therefore torsion effect of structures on the slope will much significant.Excessive torsion effect will aggravate the damage of the structure under the action of earthquake.The existing researches on torsion design and control methods of general structures have been completed,but the torsional response of structures on the slope under large earthquake is still in the initial stage,the actual engineering design urgently needs theoretical research to provide the basis.Therefor this paper uses the SAP2000 and PERFORM 3D software to build three-dimensional model,the torsional response of structures on the slope under elastic and elastic-plastic conditions is studied respectively;compared the difference of torsional response between one-way and two-way earthquake input;investigated the effects of mass eccentricity,stiffness eccentricity and strength eccentricity on the torsion effect of the structures on the slope;the applicable limit of torsion displacement ratio of structures on the slope is proposed;the shear and torsional carrying capacity of the up grounding column under large earthquake and the effectiveness of various torsion design methods are investigated.Based on the above research,the main conclusions of this paper are as follows:(1)The torsional response of the structures on the slope under earthquake action is much greater than that of the ordinary structure,the torsional displacement ratio of upper embedding floor exceeds the limit of seismic code.From the point of view of structural damage control,the torsional displacement ratio of the falling layer structure should be controlled within 1.65.The torsional response in the elastic response phase is the same under both single and bidirectional seismic inputs.(2)The torsion effect of the structures on the slope increases with the increase of the static force eccentricity.The amplification factor of interlayer torsional angle under bidirectional seismic input is between 0.95 and 1.25,and the damage degree of structure will be increased obviously.Structures on the slope under large earthquake action does not appear a strong column weak beam damage mode since the damage of up ground columns is quite serious,which needs to more attention;(3)The effect of strength eccentricity on the torsional effect of typical structures on the slope is not significant,for the structures on the slope after the reduction of the static force eccentricity,when the strength eccentricity of the rigid center is the 1.3 times of the static force eccentricity,the torsional response is the least.(4)In the structures design,the torque amplification phenomenon of the vertical component enter the elastic-plastic state should be considered,when the torsional displacement ratio of structures on the slope in the limit of around 1.5,the shear bearing capacity to meet the requirements of vertical component,but the torsion bearing capacity can not be guaranteed.(5)In order to reduce the damage degree of the structure,the seismic grade of the upper grounding column should be increased by one grade,on the basis of the calculation results,the reinforcement of the upper grounding edge columns should be improved.Adjusting the cross section size of vertical components has little effect on reducing the torsional response of the structures on the slope.In the floors under the upper embedding end arrange shear walls can significantly suppressed torsional reaction of the structures on the slope,the different assign forms of the shear walls have no significant different on the torsional response,and the control effect of torsion is better than the other assign when shear walls is placed at the periphery of the dropping layer.