Local buckling behavior of API 5L X100 grade linepipes subjected to axial compression and/or bending moment is discussed in this paper based on results obtained by finite element analyses. Yield-to-tensile strength (Y/T) ratio and design factor were taken into account in the finite element analyses in order to discuss their effects on the local buckling behavior. The local bucking behavior of such lower strength linepipes as X60 and X80 grade linepipes is also discussed for comparison. Two-dimensional solid elements and four-node shell elements were used for the finite element modeling of the linepipes subjected to axial compression and bending moment, respectively. The study has improved the understanding of local buckling behavior of the X100 grade linepipes and observed the following trends. When a linepipe is subjected to axial compression, the critical axial stress decreases with increasing design factor and Y/T ratio. However, the nominal critical strain increases with increasing design factor and decreasing Y/T ratio. When a linepipe is subjected to bending moment, the critical bending moment decreases with increasing design factor and Y/T ratio. Similarly, the nominal critical strain increases with increasing design factor. However, the nominal critical strain increases with decreasing Y/T ratio when the design factor is less than and equal to 0.6 and decreases with decreasing Y/T ratio when the design factor is equal to 0.8.

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