Buckling evaluation method of Mod. 9Cr -1Mo steel cylinder under horizontal and vertical loads

(First report: Effects of material properties and initial imperfection)

Abstract

Buckling evaluation methods capable of evaluating elasto-plastic buckling under axial compression, bending, and shear loads are required for cylindrical vessels of FBR (Fast Breeder Reactor) in order to cope with thinning due to the increase in diameter, adoption of new materials, and adoption of seismic isolation design due to the increase in the design basis earthquake ground motion. Thus, the authors have researched the buckling evaluation methods corresponding to the above condition. In this study, in order to examine the applicability of the proposed buckling evaluation formula, Monte Carlo simulation was carried out considering material properties and initial imperfections, which are the influential factors of buckling strength, then the effect of the variation of these factors on buckling load was evaluated. If the buckling load was normalized by the buckling critical value that was calculated by the proposed formula using the longitudinal elastic modulus and the design yield stress of standards for FBR (JSME S NC2) established by the Japan Society of Mechanical Engineers, the 95% lower confidence limit exceeded the threshold of the proposed formula for both the vertical single load condition and the horizontal and vertical combined load condition. The results show that the buckling critical value calculated by using the design yield stress in the proposed formula is more conservative than the 95% lower confidence limit of the buckling load affected by the scatter of material properties and others.