设置软垫层坝后背管结构非线性分析探讨

Discussion on Nonlinear Analysis of Penstock Structure Downstream of Dam with Cushion

坝下游面钢衬钢筋混凝土管道是近30年来应用最广的压力管道形式之一,其工作机理是允许外包混凝土开裂,但要限制裂缝宽度。以三峡水电站坝后背管为例,借助有限元软件ANSYS建立了设置软垫层坝后背管有限元模型,计算分析了设置软垫层坝后背管结构应力状态,并与结构模型试验对比。结果表明:坝后背管设置垫层能有效减小钢管向外围混凝土传递的内水压力,降低混凝土拉应力峰值,改善外围混凝土结构的应力状态,提高钢管的承载比。随着垫层弹模的降低、厚度的增大,这种效应更加明显。对设置软垫层的范围提出了优化建议。

Penstock with steel-lining concrete downstream of dam is one of the most widely used pressure pipeline types in recent 30years. The working mechanism is to allow cracking in the peripheral concrete and limit the crack width. In this paper, In case of the Three Gorges Project, the finite element model of the penstock downstream of dam with cushion course is built by using the software of ANSYS; the stress state of penstock is calculated and analyzed. The comparison of the result of calculation with the model test result indicates that installing cushion at penstock downstream of dam can reduce the internal tension stress transmit from the steel pipe to the peripheral concrete, lower the tension stress peak of the concrete, and improve the stress state of the peripheral concrete. The bearing capacity of the steel pipe is enhanced, and the effect is obvious with the reducing of the elastic module and augment of the thickness of the cushion. The optimization suggestions for the cushion range are put forward finally in this paper.