Numerical cracking analysis of steel-lined reinforced concrete penstock based on cohesive crack model

Abstract

As the steel-lined reinforced concrete penstock is designed to allow concrete cracking, the crack propagation and bearing characteristics after the crack are the premise to evaluate the safety and stability of the penstock. However, the formulas of the steel stress and crack width are mostly semi-empirical and not in agreement with each other. Regarding numerical analysis, the crack width cannot be detected directly using the traditional smeared crack model; moreover, applying the discrete crack model is challenging because of the need for remeshing to follow the crack formation. In this study, a cohesive crack model (CCM) is implemented. An eight-node zero-thickness element is used to model the fracture separation process of the concrete. Random cracks, rather than pre-existing cracks, are achieved by inserting cohesive elements throughout the mesh. The parameters of the cohesive elements, which constitute a key for simulating concrete cracking, are extensively discussed. The concrete crack initiation time, crack propagation pattern, and stress distribution of steel are analyzed. The results of the CCM are consistent with those of the prototype model; this confirms the proposed model could provide a reference for penstock assessment and maintenance.