Buckling and postbuckling behaviors of symmetric/asymmetric double-beam systems.

• A general nonlinear double-beam model resting on an elastic foundation is newly established. • Double-beam systems have multivalued critical buckling loads, and the carrying capacity of targeted beam can be greatly strengthened through the distribution of the two axial loads. • A simple criterion is proposed to quickly estimate whether or not the axial loads would trigger the buckling of the system under various symmetric/asymmetric boundaries. • In-phase and out-of-phase postbuckling paths and their associated stabilities of symmetric/asymmetric systems are investigated in detail, and the snap-through buckling phenomenon is detected. • Strengthening the system stiffness may even trigger the out-of-phase buckling more easily for asymmetric systems. Double-beam systems composed of two interconnected parallel beams have become basic mechanical components of modern engineering structures. Focusing on the asymmetric features in boundary conditions and other structural parameters, this paper studies the buckling and postbuckling behaviors of a double-beam system supported on an elastic foundation. The nonlinear governing differential equations of the system are derived by using the Hamilton's principle, and discretized via the differential quadrature method. Then the pseudo-arc length algorithm is adopted to overcome difficulties of numerical continuation around bifurcation points. Compared with single beam systems, double-beam systems exhibit some peculiarities like multivalued critical buckling loads, in-phase and out-of-phase postbuckling paths. Based on the proposed procedures, these buckling and postbuckling behaviors are investigated in detail. For symmetric boundary cases of the two sub-beams, the multivalued critical buckling loads of the system compose a cluster of critical curves that intersect at a point determined only by the critical loads of single beams. Hence a simple criterion based on single beam critical loads is proposed to quickly estimate whether or not the axial loads would trigger the buckling of the system. However for asymmetric boundary cases, the cluster of critical curves locate in a region that depends on the intrinsic double-beam characteristics, and the criterion is revised accordingly. Also for asymmetric systems, some unique features of the out-of-phase postbuckling paths are detected. It is found that their stabilities are quite different from those of symmetric systems, and that strengthening the system stiffness may even trigger the out-of-phase buckling more easily. Graphical abstract [Display omitted]. [ABSTRACT FROM AUTHOR]