Structural Model Comparison for Pressurized Water Reactor Containment Building - 14102

A fixed-base finite element model (FEM) is constructed based on the as-built Containment Building at Vogtle Electric Generating Plant (VEGP). This model is then compared to the design-based Lumped Mass Stick Model (LMSM). Significant difference in the modal characteristics for the FEM and LMSM are observed. To explain the difference in the modal characteristics, modeling simplifications in both the models are examined. Based on this, it was noticed that the flexibility of complex steel framing system in the building is the primary parameter for the difference, as it is not accounted for in the fixed-base LMSM. To investigate the numerical effects of the steel framing system, a time history analysis is performed on the fixed-base FEM, modified FEM called FEM-Constrained Steel and LMSM. The FEM-Constrained Steel is the model were the FEM steel member's joint properties are modified to essentially create a rigid body movement in both the in-plane and out-of-plane response modes. A comparison of the dynamic responses of the models in terms of displacement and acceleration is performed. In addition, the results from the in-structure response on the operational floor level and top of the containment shell is compared for better resolution in LMSM and FEM's ability to predict the actual dynamic behavior of the containment building. (authors)