某筏板钢筋上拱原因分析

Cause analysis of steel bar arch in a raft

河南省某高层住宅的筏板,钢筋出现上拱,漏出到筏板混凝土外面,疑似混凝土下沉,现场采用压重方法处理,没有效果,为此进行现场考察、分析,通过钢筋温度应力及受压失稳的计算,确定主要原因是,混凝土温度与环境温度差过大,膨胀加强带的施工顺序不当,钢筋水平变形受限,导致钢筋温度应力过大,失稳,且超出混凝土粘结强度的承受力。复核了压重方法没有效果的原因。讨论分析了相关问题,与现行有关规范做了对比分析,通过分析指出,避免类似现象的关键点在于,控制混凝土初凝时段的温度及混凝土浇筑顺序,此事故对设计、施工有借鉴意义。

In the raft slab of a high-rise residential building in Henan Province,the steel bars arched up and leaked out of the raft concrete.It was suspected that the concrete was sinking.Therefore,the on-site investigation and analysis were carried out.Through the calculation of temperature stress and compression instability of reinforcement bars,the main reasons were that the difference between concrete temperature and ambient temperature was too large,and the construction sequence of expansion reinforcement belt was not good.When the horizontal deformation of steel bar is limited,the temperature stress of steel bar will be too large and unstable,and it will exceed the bearing capacity of concrete bond strength.Then,the reason why the weight method is ineffective was reviewed.Through the analysis,it is pointed out that the key point to avoid the similar phenomenon is to control the temperature of the initial setting period of concrete and the concrete pouring sequence.This accident has reference significance for design and construction.