Structural Fatigue Analysis on Expansion Joints of Diversion Penstock of Hydropower Station

The section of diversion penstock near the powerhouse behind dam in some hydropower station is equipped with expansion joints, which is used to remedy deformation of penstock in axial and lateral due to the variation of temperature and foundation subsidence. When the hydropower station is in normal water diversion and power generation, the discharged flow generates fluctuating loads, induces structural vibration of guide cylinder of expansion joints, gives rise to cumulative fatigue damage of guide cylinder and also leads to weld joints in guide cylinder cracking to fall off. When generating unit is in the condition of load rejection, expansion joints bears not only the fluctuating pressure loads of the flow, but also undergoes the shock from water-hammer pressure as well, so this demands higher requirement for the safety and reliability of expansion joints structure. It has important engineering value for ensuring safety and reliability of water-diverting power generating system to conduct researches on dynamic effect that fluctuating loads having on expansion joints guide cylinder structure and cumulative fatigue damage of terminal weld of guide cylinder