地面式明钢管设计方法的比较研究

Comparison of Design Methods for Ground Exposed Steel Penstock

明钢管是一种布置于地面的输水结构,由于暴露在空气中易受到温度、不均匀沉陷的影响而产生较大的应力和变形,为此伸缩节常作为一种柔性结构用于减小温度应力和对不均匀变形进行补偿。结合某水电站工程实际,分别采用规范推荐的结构力学方法与有限单元法对明钢管应力状态进行计算,计算成果的对比分析表明:对于9 m的大直径压力钢管,规范将其简化为支撑在一系列支墩上的连续梁结构进行计算,将引起偏于保守的较大误差,因此建议对于大直径的地面明钢管结构宜采用有限元方法进行应力分析。

The exposed steel penstock is a water transmission structure laid on the ground. Due to its exposure to the air,it is sensitive to the temperature and non-uniform settlement which can produce large stress and deformation. To reduce the temperature induced stress and compensate the non-uniform settlement,the flexible expansion joint is often adopted. Based on a practical example of a hydropower station,the stress state of the ground exposed steel penstock is calculated by using the structural mechanics method recommended by the design code and the finite element method. It shows that for penstock with large diameter of over 9 m,much conservative result is obtained by the structural mechanics method,in which the penstock is simplified as a continuous beam structure supported on a series of supports. While more accurate result is got by the finite element method,in which the actual force conditions are considered. Therefore,the finite element method is recommended for the stress analysis of large diameter ground exposed steel penstock.