A series of elastoplastic large deflection analyses was carried out on thick stiffened plating with flat -bar stiffeners subjected to uni-axial thrust applying the FEM code ULSAS. A part of continuous stiffened plating was analysed considering symmetry conditions. Both stiffener and plates were modeled by shell elements. Primary attention was focused on the influence of overall initial deflection on the collapse behaviour of continuous stiffened plating. It has been found that : (1) Ultimate strength of stiffened platings considered here is attained when stiffener tripping takes place at the central part of a span. This is followed by a local plate collapse at the central part of the adjoining span. (2) Symmetrical mode of overall initial deflection having same directions in the adjacent spans tends to increase overall buckling strength (ultimate strength), whereas unsymmetrical mode of overall initial deflection has an adverse effect. (3) Ultimate strength of stiffened plating with larger aspect ratio of panels between stiffeners is more influenced by the shape of overall initial deflection. (4) Ultimate strength of local panel flange with initial deflection of hungry-horse mode is higher than that of a simply-supported plate of the same geometry. (5) Ultimate strength estimated by Perry-Robertson approach assuming stiffener-induced failure mode shows good correlation with FEM results with some safety margin.