Calculation Of Curvature Using Linear Thermal Gradient

Reinforced concrete structures for nuclear power plants are designed for thermal effects. When a structure is subject to transient temperature rise, the temperature distribution in a member becomes nonlinear. Commentary of ACT 349 code provides a method of converting a nonlinear temperature distribution to an equivalent linear temperature distribution in order to facilitate calculating curvature due to temperature change. However, the accuracy of estimated thermal curvatures for concrete sections with a liner plate needs to be examined because the ACT 349 method is based on a pure concrete section.The objective of this paper is to investigate the accuracy of thermal curvatures calculated using the equivalent linear temperature distribution for concrete sections with a liner. Temperature distributions across concrete sections are obtained from heat transfer analyses. Free thermal curvatures are calculated by converting temperature distribution to the equivalent linear temperatures and compared with those from a finite element analysis. Based on the study, the modified expression for linear thermal gradient is proposed which includes the effect of liner on curvatures.