Mechanical Characteristics And Anti-Seismic Performance Analysis Of Large Chassis Single Tower Of Structure Supported Foundations With Different Elevations

The high-rise building with large chassis belongs to the vertical narrow structure,which the stiffness and mass of the vertical direction are obviously different.It will make the structure easy to form the weak layer in the narrow position so that the damage usually occurs first in an earthquake.The application of the tower structure with large base in slope structure buildings congenitally results in two weak layers of the structure.The research on this kind of structure is few in China,so it is necessary to do further research on its anti-seismic performance.In this paper,the frame structure supported by foundations with different elevations with large chassis and single tower is main subject.The mechanical characteristics and anti-seismic performance of this kind of structure is studied by using PKPM software to design the frame structure,and using SAUSAGE software to do elasticity and elastic-plastic analysis,and studying.The main results of this research work are as follows:(1)By using the PKPM software,the different models are built,which of the frame structure supported by foundations with different elevations with large chassis and single tower with different layers of floors under the upper embedding end,different spans of floors under the upper embedding end and different offsets of tower buildings;calculate the horizontal seismic actions and analyze modal decomposition response with response spectrum analysis.Then by comparing the dynamic parameters of each model,such as period,torsional displacement ratio,drift of story,story drift and interstory shear force,the anti-seismic influence is study for the frame structure supported by foundations with different elevations with large chassis and single tower by changing different layers of floors under the upper embedding end,different spans of floors under the upper embedding end and different offsets of tower buildings.(2)By using SAUSAGE software,elasticity and elastic-plastic time-history analysis for the representative model is studied.The dynamic parameters are compared with result from calculating with response spectrum analysis,such as period,torsional displacement ratio,drift of story,story drift and inter-story shear force.The dynamic response of the structure under small earthquakes is further study,the loss distribution of the structure under large earthquakes is analyse,so that the weak position of the structure can be got.(3)Taking a certain project as an example,in order to solve the problems of obvious torsion effect,sudden stiffness change and the failure of the upper embedding column prior to the other failures in the design of the frame structure supported by foundations with different elevation,the different models are built by changing the stiffness of the bottom of the structure,the dynamic parameters of each model are compared,such as period,torsional displacement ratio,maximum drift of story,maximum story drift and interstory shear force,and the loss distribution of the structure under large earthquakes is also analysed,in order to analyze the seismic performance of structure supported by different elevations with large base with different stiffness distributions.The main findings of the study are as follows:(1)The torsion effect is severe in podium building structure of the frame structure with large chassis and single tower in mountain slope area and has little influence on the tower building comparing with ordinary structure.On the upper embedding story,the displacement ratio is the most maximum and the inter layer displacement angle and inter layer shear force have a big sudden change,which is easy to form weak layer.Under a rare earthquake,the damage is the most severe in the upper grounding column and the 1 ～ 2 stories on the roof of the podium buildings.(2)The tower building’s offsets affect the most severely in the torsion effect of podium building structure in the frame structure with large chassis and single tower in mountain slope area.It only has little change on the structural parameters such as floor displacement,floor displacement angle and floor shearing force.(3)It is more effective to reduce the torsional effect by increasing the stiffness from the lower embedding end to the top of the podium building.By adding shear wall,the effect of improving the anti-seismic performance of structure is better than by increasing size of columns.At the same time,this can weaken the weakened layer’s formation on the upper embedding story and the 1 ～ 2 stories on the roof of the podium buildings.