Though the magnitude is decreasing, the compressive residual stress is always distributed during fatigue crack growth near the crack tip. This means that the residual stress is released during fatigue crack growth due to the alternative load. ${Delta}K_{IV}$ is modified by using the initial residual stress and the redistributed residual stress in uniform and various thickness welded specimens. The former is denoted by ${Delta}K_{IV.eff.i}$ and the latter is denoted by ${Delta}K_{IV.eff.i}$. ${Delta}K_{IV.eff.i}$ gives more accurate relations in da/dN vs. ${Delta}K_{IV}$ curve, however the difference is very small.