垫层蜗壳结构中钢衬-混凝土间的接触状态:有限元分析

Contact state between membrane-covered steel spiral case and concrete in hydropower house substructures:Finite element analysis

水电站蜗壳采用垫层埋设技术时,软垫层会削弱混凝土对钢蜗壳的包裹和嵌固作用,影响两者间的接触状态,甚至引起脱空现象。本文首先从结构静力分析的角度定性解释钢衬-混凝土间出现脱空状态的潜在原因;而后借助非线性有限元数值模拟技术,研究可能影响两者间接触状态的结构性因素。结果表明,钢衬-混凝土间较小的摩擦系数、子午断面内垫层较大的铺设包角和垫层较小的压缩刚度是削弱混凝土包裹和嵌固作用的3个主要结构参数,但前两者在常规工程取值范围内的变化不会对钢衬-混凝土间的接触状态产生质的影响;相对而言,垫层压缩刚度对其的影响更为敏感。从保证钢衬-混凝土组合结构的整体性看,设计中适当折减垫层刚度是一种折衷但有益的技术手段。

When a steel spiral case is embedded with its top portion covered with a compressible mem- brane, the membrane is probably responsible for weakening the hold of concrete on the steel spiral case. That may have an influence on the contact between the steel spiral case and the concrete, and even cause a gap between them. First, this paper discussed potential origins of gaps from the view of statics. Then, FEM-based nonlinear numerical simulations were performed to clarify key structural factors influencing the contact state. The results of this study indicate that three structural factors play leading roles in weakening the hold of concrete. They are： （l） a weak friction between a steel spiral case and concrete; （2） a wide membrane-covered range in c-cross-sections and （3） a small compression stiffness of a membrane. Howev- er, routine values of parameters concerning the above first two factors do not have significant effect on the contact state. Correspondingly, the contact state is dependent on the third factor mentioned above markedly. In general, therefore, it seems that appropriately reducing a membrane＇s compression stiffness is a compro- mise but useful design technique. It will be constructive in ensuring the integrity of a hydropower house substructure.