The influence of the initial stretching of a simply supported plate strip containing a rectangular hole with rounded-off corners on the stress concentration around the hole caused by the bending of the strip under the action of uniformly distributed normal forces on the plane of its upper face is studied within the framework of the three-dimensional theory of elasticity under a plane-strain state. The mathematical formulation of the corresponding boundary value problems is presented. For the solution to these problems the finite element method is employed and for this purpose the validity of the constructed functional is proven. The material of the plate strip is selected as linear elastic, homogeneous and orthotropic. The numerical results are presented for the composite consisting of two alternating layers made from isotropic linear elastic materials.