Study On The Design Of Complex Base-Isolated High-Rise Structures With Tower Offsetting

The high-rise building structure with offset tower become a special structural system.Due to the sudden change in stiffness after the structure is retracted in the vertical direction and the non-coincidence of the mass center and the stiffness center of the structure,there are two types of irregularities in the layout of the eccentric structure.The two irregular situations affect each other under the excitation of horizontal earthquakes,so the structural forces are c omplicated and the weak parts are difficult to predict.Under the action of earthquakes,it is easy to cause the structure to form greater seismic damage,cause the structure to collapse in whole or in part,and also cause great difficulty in the structura l design.This subject combines a complex high-rise building structure engineering with a tower offset.The project locates in an area with a fortification intensity of 8 degrees(0.2g),24 floors above the ground,with a 5-story podium,the height of the building is89.50 m,and the frame shear wall structure is adopted.Fir st,the structure design is completed by the two methods of traditional seismic structure and seismic isolation structure.According to the unique adverse dynamic response of the seismi c structure with the tower offsetting,the significant changes after us ing the base isolation technology are analyzed and compared.It is concluded that the torsional factor of the seismic isolation structure is significantly smaller than that of the seism ic structure,the vibration deformation is concentrated on the isolatio n layer,the structural response is mainly translational,the first 2～3 vibration modes have a greater contribution to the bottom shear force,the higher modes have less impact on the bottom shear,and the floor torque reduction coefficient is smaller than the shear force reduction coefficient after adopting the seismic isolation technology.The elastic-plastic analysis of the above two practical design models under rare earthquakes is carried out,and the overall seismic performance of the structure and the damage of the main lateral force resisting members under large earthquakes are compared.The analysis shows that the damage of the main lateral force resisting members of the seismic isolation structure is significantly less than that of the seismic structure on the premise of meeting the same external conditions and code requirements.The seismic isolation technology can effectively improve the seismic performance of this kind of complex structure and reduce the damage of the key parts.The difference in the anti-overturning performance of the two schemes under rare earthquakes when the joint scheme and the jointed scheme are adopted for the complex high-rise seismic isolation structure with offset tower was analyzed in this paper.The anti-overturning safety is higher than that of the joint scheme.When the bearings at both ends along the longitudinal direction are configured,the section should be appropriately increased.When checkin g the wind resistance of the yield-bearing capacity of the isolation la yer,the additional horizontal force of the bearing caused by transverse inclined settlement should be considered.The setting of the post-settlement pouring zone and the construction s imulation calculation should be considered to reduce the influence of t he differential settlement of the main podium on the additional internal forces of the structure on both sides.When the post-pouring zone is not set or closed in advance,detailed anal ysis should be carried out to ensure that the bearing capacity of the b earing meets the requirements and other conclusions.Finally,taking the engineering example as the research object,the probability of lateral incremental collapse of single tower offs etting isolation structure,single tower offsetting isolation structure considering foundation settlement,and single tower offsetting isolation structure considering post-cast strip settlement in construction simulation under extremely rare earthquake is compared and analyzed.The results show that the damage index and failure probability of the single tower offset isolation structure considering the overall inclined settlement of the foundation are significantly higher than that of the single tower offset isolation structure without considering the influence of foundation settlement.The conclusions drawn from the research of this subject can provide a reference for the design of similar projects.