Fourier Expansion Number를 적용한 Beam 요소 기반 유한요소해석모델을 이용한 배관계 탄소성 해석 기법 (Elasto-plastic Analysis of Piping System Using Finite Element Model Containing Beam Element with Fourier Expansion Number)

This study proposes a method for confirming the seismic integrity based on the strain of piping systems mainly used in power plants through finite element analysis. The piping system of power plants plays a vital role in connecting the major components of the system. Under earthquake conditions, strain is accumulated due to cyclic loads, and the critical location of strain accumulation due to fatigue failure is found to be the pipe elbows. To confirm the system response, it is necessary to extend the conventional finite element analysis model to the plastic domain and perform seismic transient analysis. Therefore, in this study, a method was proposed for performing an elasto-plastic analysis using the finite element analysis model based on the beam element used in the existing design evaluation. By applying the cross-sectional deformation effect in the elasto-plastic analysis to the existing beam element, the Fourier expansion number could be used to determine the sectional degree of freedom. Through case studies for various pipes, the feasibility of simulating the accumulated plastic strain and critical location using the proposed parameter setting was confirmed. Thereafter, the methodology was verified through application to the surge line geometry of a nuclear power plant. Consequently, using the proposed method, the finite element model containing the beam element with a deformable section effect could well simulate the critical location and determine the accumulated plastic strain value with a difference of 11% in comparison with the solid element analysis result in the case study and a difference of 26% in comparison with the surge line analysis result.

This study proposes a method for confirming the seismic integrity based on the strain of piping systems mainly used in power plants through finite element analysis. The piping system of power plants plays a vital role in connecting the major components of the system. Under earthquake conditions, strain is accumulated due to cyclic loads, and the critical location of strain accumulation due to fatigue failure is found to be the pipe elbows. To confirm the system response, it is necessary to extend the conventional finite element analysis model to the plastic domain and perform seismic transient analysis. Therefore, in this study, a method was proposed for performing an elasto-plastic analysis using the finite element analysis model based on the beam element used in the existing design evaluation. By applying the cross-sectional deformation effect in the elasto-plastic analysis to the existing beam element, the Fourier expansion number could be used to determine the sectional degree of freedom. Through case studies for various pipes, the feasibility of simulating the accumulated plastic strain and critical location using the proposed parameter setting was confirmed. Thereafter, the methodology was verified through application to the surge line geometry of a nuclear power plant. Consequently, using the proposed method, the finite element model containing the beam element with a deformable section effect could well simulate the critical location and determine the accumulated plastic strain value with a difference of 11% in comparison with the solid element analysis result in the case study and a difference of 26% in comparison with the surge line analysis result.