| In recent years,with the rapid development of high-rise buildings in our country,conjoined structure is favored,often as the structure form of landmark buildings is widely used.At present,the conjoined structure is developing towards super high-rise,large span,multi-tower conjoined,and complicated connection mode.In this paper,the unequal height conjoined structure is taken as the research object,and a variety of software is used to analyze the typical actual structure examples.The influence of key design parameters on the seismic performance of the whole structure is studied.Then,the seismic performance evaluation method based on the deformation performance of the components is used to analyze the seismic performance and anti-collapse performance of the unequal height conjoined structure.The layout points of the same type of structure are summarized to provide theoretical basis for the future design of the type of structure.The main research contents and conclusions are as follows:(1)The seismic performance of four different connecting body positions of different height conjoined structure and single tower structure is compared.The results show that when designing the same type of structure,the connecting body should be avoided to set on the top floor of the low tower.The connecting body should be set at 3/4 of the height of the low tower,which can enhance the overall structural stiffness and reduce the torsion effect of the connected floor.(2)The influence of the main tower on the seismic performance of the whole structure is studied from two aspects of the height difference of the main tower and the plane combination.The results show that when the height of the low tower is 1/2 of the height of the high tower in the same type of structure design,the overall side and torsion resistance performance is more favorable.The connecting body should be set in the direction of the weak axis of the tower,and the connecting body should be set in the direction of the strong axis of the high tower,which will cause large torsion in the direction of the non-conjoined body.(3)By comparing the dynamic characteristics and dynamic responses of the conjoined structures with different connection modes,it is found that the strong connection(HR and RR)will bring the problems of vertical irregularity and large plane torsion of the tower.(3)The ER connection can effectively reduce the irregularity of the overall structure.The advantages of weak connection should be well played,but the envelope analysis of the siames-unit model and the split-unit model should be carried out for the low tower which is greatly affected by the connection.(4)The performance-based seismic design method is used to analyze the seismic performance of unequal height connected structures from three aspects: overall performance,energy dissipation and component deformation performance.The results show that in the design of the same type of structure,the ER connection should be adopted to ensure the deformation performance of the unequal height connected structure under earthquake,and the flexible support can also play a good role in energy dissipation.The relatively weak part of the structure appears in the upper floor of the high tower joint support.It is suggested that the frame column at the support should extend the section steel to the upper floor of the joint.(5)The elastoplastic time history analysis of unequal height connected structures under four seismic acceleration conditions is carried out.From the perspective of the floor distribution of component damage,even if the connector is arranged in the relatively unfavorable low tower top floor,the plastic development and component failure of the connected floor still lag behind the floor below the connected floor under the weak connection mode,and the overall structure can ensure that the connected floor does not fail prematurely.According to the failure type and sequence,various components can also achieve the requirements of "strong shear and weak bending","strong column and weak beam".(6)Based on the deformation performance of structure and components under the action of exceeding large earthquakes,the collapse resistance performance of unequal conjoined structures is analyzed.The results show that the component failure criterion is the most stringent,followed by the displacement Angle criterion,and the last is the dynamic instability criterion.The collapse mechanism of the structure is as follows: the vertical members of the first floor of the low tower fail first,then the plastic development of the floors below the conjoined tower rapidly and a large number of vertical members fail,and finally the structure collapses at the bottom of the low tower when the interstory displacement Angle exceeds the collapse limit.The low tower plays a control role in the anti-collapse performance of the overall structure.It is suggested to strengthen the vertical members of the bottom floor of the low tower,and carry out special multi-line defensive design while improving the deformation performance of the low tower. |
