Determination of Containment Vessel Ultimate Capacity Using Nonlinear Finite Element Analysis

by Doyle E. Byrd, Duke Power Co, Charlotte, NC, USA,



Document Type: Proceeding Paper

Part of: Structural Engineering in Nuclear Facilities

Abstract:

Analysis of steel containment vessels is normally performed using linear elastic solutions with allowable stresses specified by applicable design codes. This method gives little indication of the maximum one-time pressure capacity the vessel can withstand without a loss of integrity. To determine this maximum pressure, more detailed engineering techniques must be utilized in the analysis. These proposed techniques include an incremental nonlinear analysis incorporating large displacement effects, inelastic material properties with stress redistribution, updating of the stiffness matrix and load vector considering the current structure geometry, and residual load correction after each increment. From the nonlinear analysis an estimate of the ultimate capacity can be obtained using load-displacement curves for degrees of freedom which are indicative of the tendency of the structure to lose integrity. To further establish the ultimate capacity estimate, strains at certain key locations can be monitored throughout the loading history, thus defining the material yield propagation and stress redistribution within the structure.

Subject Headings: Finite element method | Stress analysis | Pressure vessels | Allowable stress design | Steel structures | Nonlinear analysis | Maximum loads

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