Compressive Strain Limits of High-Strength Linepipes

Regression formulas are developed in order to predict the critical compressive strain of X80 linepipes subjected to pure bending. The regression formulas were derived using an analytical solution and two conversion functions. The analytical solution was previously proposed to calculate the critical compressive strain of a pipe subjected to axial compression, where hardening properties are taken into account. The original analytical solution was rewritten to include a strain-hardening exponent. Two conversion functions are defined to connect two critical compressive strains of a pipe under different loading conditions. One is a pressure-effect conversion function which connects two critical compressive strains of a pipe without and with internal pressure, respectively. The other is a compression-bending conversion function which also connects two critical compressive strains of a pressurized pipe which is subjected to compression and bending. The regression formulas were obtained using the improved analytical solution and the two conversion functions. The regression formulas yield good agreement with FEA results especially for high-strain linepipes.