Impulsive loading of plastic beams with axial constraints

Abstract

This paper concerns the plastic deformations of simply supported and clamped beams whose ends are prevented from displacing axially, and which are subjected to transverse impulsive pressure loading. Finite axial forces arise as soon as the beam acquires a finite deflection, and the paper describes the transition from the initial simple beam behaviour to the final stage in which deformations are governed primarily by catenary effects. It is shown that when loads are such that deflections are of the order of the beam thickness, or greater, the treatment as a simple beam becomes unrealistic, the deflections being greatly reduced by the action of the axial force. For example, in a problem of a continuous beam on many supports where full axial constraint would be realized, the deflection may be a small fraction of that predicted by the treatment where axial forces are disregarded. Curves are presented showing how the reduction depends on the span-depth ratio of the beam and on the intensity of loading.