We show Euler equations fulfilled by strong minimizers of Blake and Zisserman functional. We prove an Almansi-type decomposition and provide explicit coefficients of asymptotic expansion for bi-harmonic functions in a disk with a cut from center to boundary. We deduce the stress intensity factor and modes coefficients of the leading term in the expansion around crack-tip for any locally minimizing triplet of the main part of Blake and Zisserman functional in the strong formulation. We exhibit explicitly a non-trivial candidate for minimality which has a crack-tip and fulfills all integral and geometric conditions of extremality.