In this paper, following the 1 st report, the behaviour of the continuous panel with an initial deflection under a compressive or tensile force combined with bending, was researched, and the numerical calculation of the effective rigidity was performed for the case that the force was in one direction. And it was proved experimentally, that the numerical results obtained in the 1 st and present reports, were applicable to the estimation of the rigidity and the strength of a box-shaped girder with an initial deflection.