高层建筑核心筒外扩CFG桩变刚度调平设计实例分析

Analysis on stiffness leveling design method of CFG piles under expansion of core tube foundation of a high building

采用传统均匀布桩方法进行大底盘基础的复合地基设计,将造成蝶形沉降和马鞍形反力分布,并导致筏板整体弯矩、冲切力和剪力增大,地基差异沉降也会引发上部结构的次应力增加。以某高层建筑框架-核心筒结构大底盘基础的地基处理为例,该高层建筑核心筒占楼面面积的20%,其荷载却占总荷载的50%,厚筏基础厚跨比大于1/6,具备扩散主楼荷载的作用,应考虑核心筒外扩下的应力减少。根据荷载、地层条件及结构布局调整地基的刚度分布,使反力同荷载分布相协调,实施变刚度调平设计,实测结果显示,核心筒与外框柱的变形趋向均匀,取得了较好的设计效果,对类似的工程具有借鉴意义。

The composite foundation of large basal foundation using traditional uniform pile distribution method will result in butterfly settlement and saddle distribution of reaction force,and lead to the increase of the overall bending moment,thrust force and shear force of the raft.The differential settlement of foundation will also lead to the increase of secondary stress of superstructure.Foundation treatment of a large basal foundation of a high building frame-core tube structure is presented as an example.The core tube of the high-rise building accounts for 20%of the floor area,and its load accounts for 50%of the total load.The thick-span ratio of the thick raft foundation is greater than 1/6,which affects the spreading load of the main building.Thus,the stress reduction under the expansion of the core tube can be considered.According to the load,stratum condition and structure layout,the stiffness distribution of foundation is adjusted,so that the reaction force is coordinated with the load distribution,and the stiffness leveling design is implemented.The measured results showed that the deformation of the core tube and the outer frame column tended to be uniform.The foundation design method of the high building can be used as a reference for similar projects.