| With the vigorous development of economic,society,science and technology,people pay more and more attention to the beauty of architecture.The integration of art and the allocation of space create a large number of eccentric structures.The structure with severe eccentricity will produce lateral torsional coupling effect under earthquake.At present,the research on the coupling and torsion coupling is becoming more and more perfect.For the eccentric structure,there are more parametric analysis of the lateral torsional coupling.But the main evaluating indicators are eccentricity and torsion to frequency ratio,and the effect of aspect ratio on the lateral torsional coupling effect has not been proposed.Although the ratio of length to width is related to the ratio of torsion to frequency,the relationship is not clear.In this regard,two two-way eccentrically balanced frame structures with different length to width ratio,but eccentricity and torsion frequency ratio were selected.By means of dynamic time history analysis,The effects of aspect ratio on torsion effect,torsion coupling effect,spatial effect and bending moment of column bottom were studied.After considering the interaction of soil and structure,the change of torsional effect,horizontal torsion coupling effect,spatial effect and bending moment of the bottom of the columns were further studied.The main work and results are as follows:(1)Based on the intensive study of the motion equation of a simplified two degree of freedom model,the eccentricity 'B' and the torsion frequency ratio '?' of the single layer simplified eccentric structure were analyzed.It was found that although the length width ratio of the structure is related to the torsion to frequency ratio,the relationship is not clear.Therefor,the interlayer rotation angle,the joint twist displacement ratio and the spatial effect coefficient were defined to measure the torsional effect,the horizontal torsion coupling effect and the spatial effect of the high rise eccentricity structure.(2)Two eccentric and bidirectional eccentric frame structures of ten layers with the same eccentricity and the same writhing rate and the ratio of the length to width ratio were selected.The finite element model was set up by ANSYS and the seismic time history analysis was carried out.Then the changing rule of interlaminar rotation angle,node torsion displacement ratio,spatial effect coefficient and the bending moment of the bottom of the columns were obtained.The rules are as follow:(1)with the rise of the floor,the torsional effect of the structure increases first and then decreases,and the maximum value is reached at the 1/5 of the total structure height;the coupling effect of the flat torsion is weakened and the spatial effect is slightly increased;(2)As the structure enters the plastic stage,and with the plastic development,the torsion stiffness degradation of the structure,the torsional effect of the structure increases more and more,the horizontal torsion coupling effect will weaken,the spatial effect changes relatively small.(3)With the increase of aspect ratio,the torsion effect and torsion coupling effect of the structure are enhanced,but the spatial effect is weakened.(4)In the same floor,the greater the torsion displacement ratio is,the stronger the lateral torsion coupling effect is.(5)With the rise of floor,the moment of column bottom gradually decreases,and the speed decreases faster and faster.The larger the radius of gyration is,the greater the torsion effect is.(3)The change rule of interlayer rotation angle,node twist to displacement ratio space effect coefficient and the bending moment of the bottom of the columns under the action of small earthquake was analyzed and compared.It was found that the torsional effect of the structure,the horizontal torsion coupling effect,the spatial effect and the bending moment are all weakened to some extent considering the influence of the foundation soil.So the effect of the foundation soil will be beneficial to the structural torsion. |
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