Consideration of Geometric Imperfections in Three Dimensional Finite Element Model Analysis of Stiffened Steel Liners Subjected to External Pressure

Abstract

The availability of tools for safety evaluation of a pressure liner is a relevant issue in both structural and hydraulic engineering. A suitable design of a steel liner may involve a significant reduction in the investment cost of a hydropower plant and may also ensure its future integrity, avoiding prolonged stoppages in the operation stage. First, a review of the design methods for steel pressure liners is outlined and certain key aspects for the critical buckling load assessment are pointed out. Second, a numerical modeling and analysis procedure of a steel pressure liner is presented. The methodology is based on 3D nonlinear finite element modeling procedures, involving both liner constraining and the effect of stiffeners. In addition, both large displacements and a surrounding elastic medium are assumed in the model. Besides, some types of geometric imperfections such as weldinduced ones, initial gap, ovality, and wallthickness loss due to corrosion are taken into account in this work. Finally, some conclusions are drawn regarding the role of imperfections in the calculated critical pressure of a steel liner.