Design of SC Walls and Connections in Nuclear Facilities

Abstract

Steel-plate composite (SC) walls and associated connections can be designed based on the provisions of Appendix N9 to AISC N690s1. AISC N690s1 is Supplement No. 1 to AISC N690-12 specification for safety related steel structures in nuclear facilities and was published in October 2015. AISC is currently in the process of developing a design guide to further enable the use of this specification. This design guide will explore the provisions of this specification in detail and discuss different possible design methodologies. SC wall details at the beginning of the design process are based on typical plant layouts, shielding requirements and prevalent practices. The spacing of tie bars and steel anchors in SC wall needs to ensure the faceplate does not undergo buckling before steel yielding. The steel anchor additionally need to be spaced to ensure that (i) interfacial shear failure does not occur before out-of-plane shear failure, and (ii) the yield strength of the faceplates is developed over the development length. The tie bars need to have sufficient tensile strength to prevent splitting failure of SC walls. The elastic analysis of the SC walls is performed using a finite element analysis. The analysis needs to consider cracked transformed stiffnesses and equivalent material properties. The analysis will be conducted for operating thermal and accident thermal load combinations. The individual demands and the combination of demands need to be compared with the available strengths. The SC walls need to be adequately detailed for openings, meet construction and fabrication tolerances, and satisfy the Quality Assurance and Quality Control requirements. The designed SC walls needs to be safe for impactive and impulsive loads. SC wall panel may need to be (i) anchored to basemat, (ii) connected to another SC wall panel, or (iii) connected to RC slab. The SC connections can be designed as full strength connection or over strength connections. The connection needs to have a well-defined force transfer mechanism. The connection required strength is determined from the design demands of SC walls and the connection design philosophy. The available strength is determined from the individual strengths of connectors participating in the force transfer mechanism.