Abstract: In this paper, the extended rivet-force-method is described and applied to calculating the stress intensity factors of two types of stiffened panels with splice stringers. To solve such a problem, the key point is to determine the displacement feilds of the irregular cracked stiuctures stiffened with splice stringers. This problem can be solved by use of the modified rivet-force-method employing Palis’ displacement formula.Displacement formulae for cracked semi-infinite plates and strips are developed in this paper. Two practical examples of stiffened panels with sp’ice stringers are solved. The curves of the stress intensity factors and the load concentration coefficient versus length of the cracks are given. The comparison of the results obtained with that by FEM shows that they agree well with an acceptable accuracy for engineering problems.