CCTV新台址主楼外筒关键节点设计与构造

Detailed design of key joints of the external tube in New CCTV Building

CCTV新台址主楼采用支撑筒体结构体系,外筒蝶形节点以及柱脚节点是其中的关键性节点。本文通过对蝶型节点的有限元分析,提出此类节点简化的设计方法,保证了在支撑构件屈服时,蝶型节点能基本保持弹性,满足"强节点、弱杆件"的结构抗震要求。通过与节点模型试验结果的比较,验证了这一设计方法的正确性。由于塔楼双向倾斜,且在结构高位有连体结构,造成部分外筒SRC柱柱脚在竖向荷载作用下出现拉力,与水平荷载作用下拉力叠加后进一步增大。由于水平荷载作用方向的不确定性,柱脚也可能承受较大的压力。根据柱脚受拉程度的不同,结构设计中分别采用了露出外包式、埋入式两种不同的柱脚构造形式,并在外包式柱脚中采用了高强预应力锚栓来平衡柱脚的拉力。

The New CCTV Building adopts external tube with brace to resist the lateral forces. The ＇ butterfly joint＇ of external tube and the column base joint are the key joints of the structure. According to the finite element analysis of the ＇ butterfly joint＇ , this paper advanced the simplified design method for this kind of joint, which satisfies the requirement of seismic design, i.e. ＇ strong joint, weak component＇. This method ensured the elasticity of the ＇ butterfly joint＇ when the bracing members reached the yield point. The result of the joint model experiment also proved the reliability of the simplified method. The inclining tower and the overhang structure on the high level resulted in the tension forces in the SRC column bases of the external tube under the vertical force. The tension force was superimposed and increased after the horizontal forces act on the structure. The column base might also bear considerable compression stress under the different directions of the horizontal forces. Encased column base and embedded column base were used separately to resist the different level of tension forces. Moreover, high strength pre-stressed bars were used in the encased column bases to balance the tension force of the column bases.