Study On Seismic Performance And Torsional Effect Of An RC Over-limit High-rise Frame-offset Shear Wall Structure

The frame-Shear wall structures are widely used in high-rise structures due to their good use of space and seismic resistance of the second line of defense.In order to meet the requirements of building function and lighting effect,shear wall offset of the overrun frame-shear wall structure is sometimes used in the actual project.Due to the different rates of degradation of shear wall and frame side shift stiffness,such frame-offset shear wall structures may experience significant torsional effects under seismic action,which may affect structural safety.Therefore,it is of theoretical and practical engineering significance to carry out the seismic analysis and torsional effect study on the structure of the super-limited high-rise frame-offset shear wall.In this paper,a shear-wall offset frame-shear-wall structural system for office buildings is studied,and YJK software is used to conduct small,medium and large seismic elasticity analysis to study the seismic performance of this type of structure.The maximum floor eccentricity of the structure is 22.9%,the maximum torsional displacement ratio is 1.47,and the torsional effect is more pronounced under seismic action.Since the horizontal shear force borne by the frame is less than 20%of the total seismic shear force at the bottom of the structure,the frame shear force needs to be adjusted according to the smaller values of 0.2V0 and 1.5Vfmax to obtain the shear adjustment factor for each floor.The adjustment factor for floor shear presents the characteristics of a small middle floor and a large bottom and top floor.The SAUSAGE software was used to analyze the structure under three sets of seismic waves for the large-scale seismic plasticity time course.The results show that damage to the structure occurred under a major earthquake,resulting in a degradation of the structural stiffness;the damage cloud map of the structural floor has a clear torsional feature,which is caused by shear wall bias.Although the interlayer displacement angle of the structure under large earthquakes meets the specification requirements,for seismic action in different directions,the degree of damage to the shear wall varies and the stiffness degradation varies.Therefore,it is recommended to adjust the shear adjustment factor in the X direction by 0.25 V0 and the shear adjustment factor in the Y direction by 0.35 V0 for the elastic design.The nonlinear analysis method of ABAQUS software is used to refine the analysis of the frame,shear wall stiffness degradation,floor shear distribution and torsional effect of the structure under horizontal load.Analysis shows that under horizontal loading,the stiffness of the shear wall degrades before the frame,and eventually the stiffness of the shear wall degrades to about 20%of the initial value,and the frame degrades to about 40%of the initial value,and the specific results of the degradation will be different depending on the direction of loading.Comparing the frame shear sharing ratio calculated by YJK and SAUSAGE with ABAQUS,the general rule is basically the same:as the load increases,the percentage of shear carried by the shear wall decreases gradually and the percentage of shear carried by the frame increases gradually.Analysis of the resulting shear adjustment factor envelope provides a reference for structural design optimization.At the beginning of loading,the position of the structure’s rigid core is basically unchanged,and the total added torque of the structure is linearly related to the horizontal load;in the middle of loading,the rigid core is close to the mass,the eccentric distance decreases,and the growth rate of the total added torque slows down;at the end of loading,the distance between the rigid core and the mass is greatly reduced,and the total added torque decreases accordingly.In order to reduce the torsional effect of the initial design scheme under seismic action,three optimization schemes are proposed to study the seismic resistance and stiffness position changes of different schemes.A comprehensive analysis shows that the option of adding a partial shear wall alone is not only better than the option of increasing frame stiffness alone,but also better than the option of adding both a shear wall and increasing frame stiffness.The results of this paper can be used as a reference for theoretical research and similar engineering design.