ACI 349.1R-07

This report presents a design-oriented approach for considering thermal effect on reinforced concrete structures. Although the approach is intended to conform to the general provisions of Appendix E of ACI 349, it is not restricted to nuclear power plant structures. The general behavior of structures under thermal effects is discussed together with the significant issues to consider in reinforcement design. Two types of structures - frames and axisymmetric shells - are addressed. 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.



Keywords: cracking (fracturing); frames; nuclear power plants; shells; structural analysis; structural design; temperature; thermal effect; thermal gradient; thermal properties.

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