Abstract
The installation of base isolation systems in nuclear power plants can improve their safety from seismic loads. However, nuclear power plants with base isolation systems experience greater displacement as they handle seismic loads. The increase in relative displacement is caused by the installed base isolation systems, which increase the seismic risk of the interface piping system. It was found that the failure mode of the interface piping system was low-cycle fatigue failure accompanied by ratcheting, and the fittings (elbows and tees) failed due to the concentration of nonlinear behavior. Therefore, in this study, the limit state was defined as leakage, and an in-plane cyclic loading test was conducted in order to quantitatively express the failure criteria for the SCH40 6-inch carbon steel pipe elbow due to low-cycle fatigue failure. The leakage line and low-cycle fatigue curves of the SCH40 6-inch carbon steel pipe elbow were presented based on the test results. In addition, the limit state was quantitatively expressed using the damage index, based on the combination of ductility and energy dissipation. The average values of the damage index for the 6-inch pipe elbow calculated using the force−displacement (P–D) and moment−relative deformation angle (M–R) relationships were found to be 10.91 and 11.27, respectively.
Highlights
Following the Fukushima nuclear power plant accident in Japan, issues concerning the seismic safety of nuclear power plants have been continuously raised [1,2]
The seismic loads acting on the interface piping system had the characteristics of relwas a complementary metal-oxide-semiconductor (CMOS) camera
Elbow, which is a fitting in the interface piping system, is low-cycle fatigue failure caused
Summary
Following the Fukushima nuclear power plant accident in Japan, issues concerning the seismic safety of nuclear power plants have been continuously raised [1,2]. In Korea, which is located in regions with low to moderate seismicity, many opinions have been raised that preparation for earthquakes is insufficient, and the country’s current seismic design criteria are excessive. It is difficult to object to the opinion that seismic safety must be the top priority in nuclear power plant design, because the ripple effect of seismic damage is difficult to estimate. Priority must be given to securing seismic performance against the worst case scenario for the seismic design of nuclear power plants in regions with low to moderate and high seismicity [3,4]. Base isolation systems are most commonly used to reduce the seismic force of earthquakes on large structures, such as bridges and buildings [5,6]. Base isolation systems have been recognized as the most reliable seismic response systems because their seismic force reduction effect has been verified
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