This study explores further extension of the computational cell methodology to model Mode I crack extension in a high strength pipeline steel. Plane-strain analyses of a tubular structure containing longitudinal cracks with varying crack depth to thickness ratios (a/t) are employed to characterize crack-tip constraint for cracked pipes under internal pressure. Laboratory testing of an API 5L X70 steel at room temperature using standard, deep crack C(T) specimens provides the crack growth resistance curve to calibrate the micromechanics cell parameters for the material. The cell model incorporating the calibrated material-specific parameters is then applied to predict the burst pressure of a thin-walled gas pipeline containing longitudinal cracks with varying crack depth to thickness ratios (a/t). The numerical analyses demonstrate the capability of the computational cell approach to simulate ductile crack growth in fracture specimens and to predict the burst pressure of thin-walled tubular structures containing crack-like defects.