Non-linear in-plane analysis and buckling of pinned-fixed shallow arches subjected to a central concentrated load

This paper is concerned with an analytical study of the non-linear elastic in-plane behaviour and buckling of pinned-fixed shallow circular arches that are subjected to a central concentrated radial load. Because the boundary conditions provided by the pinned support and fixed support of a pinned-fixed arch are quite different from those of a pinned-pinned or a fixed-fixed arch, the non-linear behaviour of a pinned-fixed arch is more complicated than that of its pinned-pinned or fixed-fixed counterpart. Analytical solutions for the non-linear equilibrium path for shallow pinned-fixed circular arches are derived. The non-linear equilibrium path for a pinned-fixed arch may have one or three unstable equilibrium paths and may include two or four limit points. This is different from pinned-pinned and fixed-fixed arches that have only two limit points. The number of limit points in the non-linear equilibrium path of a pinned-fixed arch depends on the slenderness and the included angle of the arch. The switches in terms of an arch geometry parameter, which is introduced in the paper, are derived for distinguishing between arches with two limit points and those with four limit points and for distinguishing between a pinned-fixed arch and a beam curved in-elevation. It is also shown that a pinned-fixed arch under a central concentrated load can buckle in a limit point mode, but cannot buckle in a bifurcation mode. This contrasts with the buckling behaviour of pinned-pinned or fixed-fixed arches under a central concentrated load, which may buckle both in a bifurcation mode and in a limit point mode. An analytical solution for the limit point buckling load of shallow pinned-fixed circular arches is also derived. Comparisons with finite element results show that the analytical solutions can accurately predict the non-linear buckling and postbuckling behaviour of shallow pinned-fixed arches. Although the solutions are derived for shallow pinned-fixed arches, comparisons with the finite element results demonstrate that they can also provide reasonable predictions for the buckling load of deep pinned-fixed arches under a central concentrated load. (C) 2012 Elsevier Ltd. All rights reserved.