Hydraulic load-bearing mechanism in rib-strengthened steel bifurcation structures of hydroelectric power plants: Numerical simulation

Abstract

When a penstock serves a water supply purpose for multiple hydrogenerators in a hydroelectric power plant (HPP), a bifurcation structure should be installed between the main pipe and the branch pipes. This study focuses on a rib-strengthened steel bifurcation structure (RSSBS) with an emphasis on its hydraulic load-bearing mechanism. The finite element method is used with the contact and material non-linearities considered. The numerical simulation results agree reasonably well with in-situ measured data. Our research has underlined the critical role of the crescent-shaped rib (CSR) in lessening the stress-concentration at the bifurcation. The CSR is found to separate from the surrounding concrete under the internal water pressure (IWP), thus causing less IWP to be transmitted to the concrete. Despite the fact that the CSR is not in tension-stress-only status, however, the tensile-stress level is well within an acceptable range. In this context, the CSR should not necessarily be in tension-stress-only status, which is recognized as an ideal stress state in the conventional design philosophy. The findings also suggest that the importance of the concrete should not be stressed too much in the structural design of RSSBSs considering its backfilling role. Highlights The role of the crescent-shaped rib in strengthening local stiffness is underlined. The rib is found to separate from the concrete under the internal water pressure. The simulation results agree reasonably well with in-situ measured data.