Finite deformation of a fully fixed beam comprised of a non-linear material

The structural behaviour at finite deformation of a mild steel beam of rectangular cross-section, fully encastré at both ends and subjected to a concentrated load at mid-span, is examined in this paper. The axial tension, induced in the beam by virtue of its change in geometric configuration, gives rise to a load-carrying capacity of the beam in excess of that predicted by first-order flexural theory. Existing methods of analysis, assuming the beam to be composed solely of a linear elastic or a pure plastic material, are reviewed and an analysis is proposed for a beam composed of an elastic-plastic material. Experimental results are compared with theoretical predictions and the proposed elastic-plastic analysis is seen to give the most realistic prediction of the overall behaviour of the beam.