ACI PRC-349.1 : 2024

Description: This report presents a design-oriented approach for considering thermal effect on nuclear safety-related concrete structures. The approach presented in this report is intended to assist the licensed design professional in addressing the requirements of Appendix E of ACI CODE-349-13. Although this report is focused on the requirements of ACI CODE-349, the general behavior of structures under thermal effects and the significant issues to consider in design are broadly applicable in the design of other types of reinforced concrete members and structures. Three types of structures—frame structures, concrete wall structures, and axisymmetric structures—are addressed. For concrete wall structures, thermal and structural behaviors are discussed. Guidelines are provided for determining the required strengths for concrete walls subject to thermal loading combinations. For frame structures, a rationale is described for determining the extent of component cracking that can be assumed for purposes of obtaining the cracked structure thermal forces and moments. Stiffness coefficients and carryover factors are presented in graphical form as a function of the extent of component cracking along its length and the reinforcement ratio. Fixed-end thermal moments for cracked components are expressed in terms of these factors for: 1) a temperature gradient across the depth of the component; and 2) end displacements due to a uniform temperature change along the axes of adjacent components. For the axisymmetric shells, normalized cracked section thermal moments are presented in graphical form. These moments are normalized with respect to the cross-sectional dimensions and the temperature gradient across the section. The normalized moments are presented as a function of the internal axial forces and moments acting on the section and the reinforcement ratio. Use of the graphical information is illustrated by examples.