Nonlinear Simulation Analysis Of Torsional Effect On Lateral-resisting Performance Of RC Frame-shear Wall Structures In Different Principal Axes

RC frame-shear wall is a structure composed of two different structural systems.Its mechanical characteristics and deformation characteristics are closely related to the stiffness eigenvalueλ.When RC frame-shear wall structures with different stiffness eigenvalues enter the elastic-plastic stage,the stiffness degradation rules of frame and shear wall are different,and the internal force distribution rules are also different.In addition to horizontal displacement,torsion effect should also be considered under earthquake.Since structural torsion is a spatial problem,it is necessary to consider different spindle stiffness characteristic values to analyze the lateral performance of RC frame-shear wall structures considering torsion effect.This paper mainly studies the influence of torsion effect on the lateral resisting performance of RC frame-shear wall structure in different principal axes,and the torsion effect of the structure is measured quantitatively by introducing the torsion effect coefficient.By changing the number of shear walls,nine 15-storey RC frame-shear wall models with the same plane size but different characteristic stiffness values in X direction and Y direction（the shear sharing ratio of the bottom frame is about 10%,20%and 30%,respectively）were established.Based on three-dimensional solid degenerate virtual laminated element nonlinear program VFEAP on model of respectively 5%consider accidental eccentricity unidirectional and bidirectional seismic earthquake effect,the influence of the characteristic stiffness values and torsion effect coefficients on the lateral resisting performance of RC frame-shear wall structures is analyzed.The results show that the degradation degree of the frame stiffness and the shear redistribution degree of the whole structure considering the bidirectional seismic are higher than that of the unidirectional eccentric seismic,and the degradation degree increases with the increase of the torsion effect coefficient.When the characteristic stiffness value is constant,the larger the torsion effect is,the higher the stiffness degradation degree of the frame and shear wall under bidirectional seismic is.It is more conservative to consider unidirectional eccentric seismic when the torsion effect coefficient is small and bidirectional seismic when the torsion effect coefficient is large.Three RC frame-shear wall structures with the same stiffness eigenvalues and different torsional effect coefficients are established by changing the location of shear walls.The finite element analysis of the model considering 5%accidental eccentric unidirectional seismic and bidirectional seismic is carried out to analyze the effect of the torsion effect coefficient on the torsion performance of the structure.The results show that,no matter under unidirectional eccentric seismic earthquake or bidirectional seismic earthquake,the higher the torsional effect coefficient is,the greater the peak value of torsional angle of the structure is;the middle floor of the structure is most affected by the torsional effect coefficient,followed by the lower floor,and the upper floor is least affected by the torsional effect coefficient;when the torsional effect coefficient is small,the torsional stiffness of the structure is degraded under unidirectional eccentric seismic earthquake When the torsional effect coefficient is large,the torsional stiffness degradation degree is higher under bidirectional earthquake.As a supplement to the VFEAP program,the dynamic elastoplastic analysis software SAUSAGE is used to analyze the dynamic time history of nine RC frame shear wall structures with different stiffness eigenvalues.The changes of x-direction and Y-direction story displacement angle and the ratio of frame story shear force V_fto bottom total shear force V₀of nine models under small,medium and large earthquakes are analyzed,the variation law of displacement Angle between RC frame-shear wall with different stiffness characteristic values under actual earthquake action is explored,and a two lines of defense adjustment method considering torsion effect is proposed.It provides a reference for further seismic design theory of RC frame-shear wall structures considering torsion effect.