地基不均匀沉降对CCTV新台址主楼变形预调值的影响及分析

中央电视台(CCTV)新台址主楼由两倾斜塔楼、L形大悬臂以及裙房组成,其特殊的造型设计使得施工过程结构的变形发展异常复杂。由于施工采用两倾斜塔楼独立安装、大悬臂从塔楼逐步悬伸对接的施工方案,导致在施工过程中,上部结构除了在自身荷载作用下产生变形外,还会随着地基不均匀沉降而发生变形。因此必须对结构构件的安装位形设置预调值,以保证施工完成后的结构位形达到设计位形,否则成型位形将不满足设计要求,甚至会导致大悬臂结构无法顺利安装。本文建立了基础与上部结构的一体化有限元模型,考虑了桩、土、筏板与上部主体结构的相互作用,分析评估了地基沉降对结构变形的影响。计算结果表明,考虑地基不均匀沉降,其变形预调值在悬臂端,竖向增大了11.9mm(竖直向上为正),水平向分别增大了-16.6mm(正南方向为正)和10.6mm(正东方向为正)。施工实践证明,按照考虑基础不均匀沉降影响获得的结构变形预调值安装,可以保障大悬臂准确合拢。

Analysis on the influence of foundation settlement on the pre-set deformation value of New CCTV Building

As to New CCTV Building,the deformation attributes to the loading affection resulted from the inclined towers and cantilevered structure system,but also the foundation settlement as well,which must be estimated to determine the construction and erection procedure.Since the two towers are built separately and the cantilever is protruded and closured in the air step by step,pre-set deformation value must be taken for the structure members to make sure that the cantilever will closure smoothly during the construction process and the structure will reach the designed status after the structural construction is finished.Based on the integrative model including foundation and super-structure which considers reciprocity of the soil,pile and super-structure,this paper evaluated the foundation settlement′s influence on the deformation of structure during erecting process and calculates the pre-set deformation value that took the foundation settlement into account.The pre-set deformation value by this method at the joint point of cantilever increased 11.9mm vertically(upward is positive direction),-16.6mm(south is positive direction) and 10.9mm(east is positive direction) horizontally.This paper validates that the integrative modeling method for calculating the pre-set deformation value is effective and the result is applied directly to the construction,which has been proved to be helpful in the closure process of the cantilever.