连体结构传力机制分析及连接体抗震设计

Analysis of Force Transfer Mechanism of a Connected Structure and Seismic Design of a Connected Body

连体结构往往因独特的建筑造型成为城市地标建筑,CCTV主楼、重庆来福士广场、苏州东方之门、武汉保利广场等都是典型的连体建筑。而每个连体结构受其连接方式和位置、塔楼动力特性及抗震设防烈度等因素影响,均有其自身的抗震设计思路。该文以某连体结构为例,对以下几个方面进行分析:(1)连接体连接方式的选择及影响因素;(2)基于振型模态的动力特性分析;(3)连体结构在X、Y方向的受力机制;(4)连接体性能水准的选择及构件设计;(5)通过非线性时程反应分析手段,识别连接体各杆件在罕遇水准的性能。结果发现:(1)连体结构连接方式需综合考虑设防烈度、连接位置、连接体的空间尺度和塔楼动力特性确定;(2)连体结构需充分选取振型数;(3)刚性连接的连体结构在顺连接体方向受力类似门式刚架,两栋塔楼间建立较强的联系作用,在垂直连接体方向,两栋塔楼依靠楼板传递剪力,形成较弱的连接;(4)连接体受力类似小跨高比连梁承受巨大的弯矩和剪力,上弦杆、下弦杆、楼板及面内斜撑共同承担弯矩,腹杆则承担剪力;(5)连接体的设计应考虑施工次序、收缩徐变、基础沉降差异的影响,构件的设计尤其应关注上、下弦杆和斜腹杆的正截面设计;(6)该项目连接体在罕遇地震作用下仅个别斜腹杆进入塑性状态,因此该连体结构的整体设计思路清晰,可以达到构件确定的性能目标。

Conjoined structures often become urban landmarks due to their unique architectural shapes,such as the CCTV main building,Chongqing Raffles City,Suzhou Oriental Gate,Wuhan Poly Plaza,etc.,which are all typical conjoined buildings.Each conjoined structure,affected by factors such as its connection method and location,tower dynamic characteristics and seismic fortification intensity,has its own seismic design ideas.This paper uses a conjoined structure as a case to analyze the following aspects:(1)the selection and influencing factors of the connection method for a conjoined structure;(2)the analysis of dynamic characteristics based on vibration modes;(3)the force mechanism a conjoined structure has in the X and Y directions;(4)the selection of performance levels of a conjoined structure and the component design;(5)with the non-linear time history response analysis method,the performance of each member of the conjoined structure is identified at the rare level.The results showed that:(1)The connection method for a conjoined structure should be determined by comprehensively considering the fortification intensity,the connection position,the spatial scale of the conjoined structure and the dynamic characteristics of the tower building;(2)The number of vibration modes must be fully selected for the conjoined structure;(3)The rigidly conjoined structure is similar to the portal frame along the direction of the conjoined structure.A strong connection is established between the two tower buildings.In the direction of the vertical conjoined body,the two tower buildings rely on the floor slab to transmit shear forces,so as to form a weaker connection;(4)The force of the conjoined body is similar to that of the small span-to-height ratio coupling beam,which bears huge bending moment and shearing force.The upper chord,lower chord,floor and in-plane bracing share the bending moment,and the web members bear the shearing force;(5)The design of a conjoined structure should consider the influence of the construction sequence,shrinkage and creep,and the difference in foundation settlement.The design of the components should pay particular attention to the normal section of the upper and lower chords and diagonal webs;(6)In this conjoined structure project,only several diagonal webs enters the plastic state under the action of rare earthquakes.Therefore,the overall design idea of the conjoined structure is quite self-explanatory,and the performance target determined for the component can be achieved.