Plate-Stiffener Assemblies in Uniform Compression. Part I: Buckling

In this paper the behavior of plate and stiffener assemblies in uniaxial compression is investigated. As the geometric properties of the stiffeners dictate the in- and out-of-plane boundary conditions of the attached plate, a set of restraining parameters is defined that quantify the rotational, in-plane bending and translation restraints the stiffeners offer to the plate. The plate is modeled as partially restrained against rotation and in-plane translation. Extensive results are obtained showing the transition from the rotationally free boundary condition, i.e., the attached stiffener possesses zero rotational stiffness, to the rotationally clamped boundary condition, i.e., the stiffeners have infinite rotational stiffness. A similar treatment is given for the in-plane boundary condition, from free expansion of the unloaded edges to fixed, immovable boundaries developing quasi-biaxial compression. The sensitivity of the buckling mode to these restraints is also examined. The investigation highlights the equal importance of defining the in-plane and out-of-plane boundary conditions to characterize critical and postcritical behavior of the unaxially loaded plate.