Estimating the residual strength of fire-exposed reinforced concrete (RC) structures is of great importance in determin-ing whether the cooled structure is safely functional or immediate repair is needed. This paper describes the results of experimental and numerical investigations on fire and post-fire structural responses of a 2-story moment-resisting RC frame test specimen. The lower story of the test specimen, which was subjected to service loads, was heated for 60 min-utes in accordance with the ISO-834 standard fire test. The test specimen exhibited a satisfactory structural performance during the fire course and considerably recovered much of its pre-fire deflection state when cooled. To investigate the re-serviceability and residual load bearing capacity of the cooled test specimen, a destructive cyclic vertical loading was conducted. A detailed 2D finite element model was developed as well. By comparing the test and analysis results, it was found that due to the fire damage the test specimen lost 30% of its load bearing capacity. The proposed numerical mod-elling approach in this study predicted considerably well the post-fire residual strength of the test specimen.
The residual strength tests after cyclic loadings on concrete cylinder specimens and stud anchor specimens were performed to obtain data regarding effects of cyclic loadings on concrete and stud anchor specimens for proposing a new method capable of evaluating the soundness of equipment support using the S-N curves. More specifically, cyclic loadings may lead to a reduction in the strength and stiffness of concrete and also lead to the pullout and a reduction of the strength of stud anchor sections, which may reduce the rigidity of the equipment support, and this situation is not preferable from the viewpoint of long-term soundness evaluation. Then, in order to investigate whether or not cyclic loadings reduce the strength and the rigidity of the equipment support, cyclic compressive loadings with constant amplitude were applied to cylinder specimens, then static compression tests were performed. Also, cyclic tensile loadings with constant amplitude were applied to stud anchor specimens, then static pullout tests were performed. As a result, it was found that the cyclic loading would not lead to the pullout of stud anchor and a reduction of the strength of stud anchor if the maximum stress ratio is less than the long-term allowable stress.
“Guidelines for Maintenance and Management of Structures in Nuclear Facilities” was published by the Architectural Institute in Japan in 2008 and revised in 2015. This is the first standard that covers the maintenance and management of structures in Japanese Nuclear Facilities. This has been contributing to the broad activities related to the life-time man-agement of Nuclear Facilities. This paper outlines these guidelines.