Dadinkowa水电站厂房蜗壳外围薄壁混凝土受力分析

Stress analysis on outside thin-wall concrete of spiral case in powerhouse of Dadinkowa Hydropower Station House

针对国内对水轮机蜗壳外围薄壁混凝土结构研究较少、设计经验欠缺的问题,以尼日利亚Dadinkowa水电站厂房续建项目为典型案例,对水电站蜗壳外围薄壁混凝土结构进行设计分析。建立三维有限元模型,分析蜗壳外围混凝土在正常运行工况和检修工况下的应力,提取内力进行配筋计算;建立蜗壳0°断面的平面有限元模型,分析蜗壳顶部及基坑里衬附近混凝土应力,提取弯矩和轴力进行正截面和斜截面承载力计算。结果表明,基坑里衬附近混凝土尺寸较小,最薄处仅约21 cm,压应力峰值位于内侧,为5.67 MPa,未超过C25混凝土抗压强度;拉应力峰值位于外侧,为1.55MPa,最大拉应力范围较小。从而,混凝土尺寸能够满足斜截面抗剪承载力要求,无需另外设置抗剪钢筋。为保障结构安全,采用一期混凝土凿毛4 cm、配合植筋φ16@1×1 m的措施,基坑里衬采用双层双向配筋和C30混凝土,蜗壳及引水钢管顶部设置弯起φ32@15 cm钢筋提高斜截面承载力。设计经验可为同类工程设计提供参考。

Aiming the problem of that the studies on the outside thin-wall concrete structure of the hydraulic turbine spiral case are less along with deficient design experiences at home and abroad,a design analysis is made on the outside thin-wall concrete structure for the spiral case of hydraulic turbine in hydropower station by taking the extension project for Dadinkowa Hydropower Station in Nigeria as a typical case.For which,a 3-D finite element analysis model is established for analyzing the stresses in the outside concrete of the spiral case under both the normal operation condition and the maintenance condition,and then extracting the internal force for the reinforcement calculation,while,another plane finite element model for the 0° cross-section of the spiral case is also built up for analyzing the concrete stress near the top of the spiral case and the inner lining of the foundation pit,and then extracting the bending moment and axial force for the calculations of both the normal section bearing capacity and the oblique section bearing capacity.The results show that the size of the concrete near the inner lining of the foundation pit is smaller with the thinnest thickness of 21 mm,the compressive stress peak value therein is 5.67 MPa and occurs at the inner side,which is not over the compressive strength of the C25 concrete; while the maximum tensile stress range is smaller with its peak value of only 1.55 MPa and occurs at the outer side.Thus,the concrete size can meet the requirement of the shear-bearing capacity of the oblique section without arranging another shear reinforcement.In order to ensure the safety of the structure,the measure of roughening the Phase I concrete of 4cm with planting reinforcing bar of φ16@ 1 × 1 m is adopted,while the two-layer two-way reinforcement and C30 concrete are applied to the foundation pit inner lining and the bended φ32 @ 15 cm reinforcing bars are arranged at the tops of both the spiral case and the penstock for enhancing the oblique section bearing capacity concerned.This design experience can provide a reference for the engineering design of the similar project.