Cracking of P/C Nuclear Containment Structures

Abstract

Rules for determining the spacing and widths of both through-the-wall and surface cracks in post-tensioned concrete containment structures under internal pressure are presented. These involve the construction details and the average strain obtained from an analysis that accounts for concrete properties in the post-cracking range. To evaluate these rules and the concrete constitutive relationship used in the analysis, twelve quarterscale segments were designed to simulate construction and stress conditions at various locations of a containment structure. Major variables included ratio of prestressing, concrete cover, reinforcement spacing, lap splices and combined axial load and moment. It was observed that the crack spacing depended on the spacing of the reinforcement and prestressing tendons parallel to the cracks and that the final crack pattern was fully developed at the yield strain of the reinforcing steel. Concrete cover was not found to have a significant influence on crack spacing. The procedures developed to determine crack spacing and widths are used to predict the cracking of a one-fourteenth scale model of a containment structure tested later in the research project.