超长环形体育场混凝土结构施工期抗裂性能数值分析

Numerical Analysis of Crack Resistance of Concrete Structure of Ultra-Long Round Stadium During Construction

超长混凝土结构在温度变化和材料收缩过程中会产生内力和变形,容易使结构水平构件超过混凝土受拉强度而开裂。针对某周长约为670 m环形超长体育场混凝土结构,研究在施工过程中采用不同措施对主体结构的抗裂效果。使用有限元软件对体育场一层混凝土结构进行三维建模,通过“生死单元”实现结构施工过程,通过子程序定义主体结构的混凝土收缩、后浇带混凝土的膨胀和时变弹模。模拟结果表明当按照环形结构在东西两侧由北向南依次施工并合龙的施工组织顺序,早期浇筑的结构北部两侧转角处混凝土板由于温度降低和收缩原因产生的应力水平最高;而使用膨胀后浇带混凝土能有效补偿拉应力和控制裂缝产生。在环境温度低的时期,调整结构合龙时间能大幅降低温度对结构的影响;合理安排后浇带跳仓施工顺序,也能避免板应力沿结构长度的累积。

The ultra-long concrete structure produces internal force and deformation with temperature change and concrete shrinkage,which results in the cracking of horizontal structure specimens exceeding the tensile strength of the concrete.For an ultra-long round concrete stadium with a perimeter of about 670 m,the crack resistance of the main structure under different measures in construction was studied.Three-dimensional modeling was performed on the concrete structure of the first floor of the stadium by finite element software,and the construction process was realized through the birth and death element method.The contraction of the concrete in the main structure,as well as the expansion and the time-dependent elastic modulus of the concrete in the post-pouring belt were defined based on the subprogram.The simulation results show that when the east and west sides of the round structure are constructed from north to south in succession and finally integrated,concrete slabs at the northern corner of the early poured structure show the highest stress level because of temperature reduction and shrinkage.In addition,the expanded concrete in the post-pouring belt can effectively compensate for tensile stress and control cracks.The adjustment of structural integration time on days with low temperatures can greatly alleviate the influence of temperature on the structure.Furthermore,a rational construction sequence of the post-pouring belt can avoid the accumulation of plate stress along the structural length.