The plastic theory of bending of mild steel beams with particular reference to the effect of shear forces

Abstract

While the simple plastic theory of bending gives a satisfactory explanation of the observed behaviour of mild steel beams, it is open to various theoretical objections. These are examined by reference to the theory of perfectly plastic materials, and a special examination is made of the effect of shear forces, for which no allowance is made in the simple theory. The results are applied to beams of both rectangular and I section, and it is shown that the error involved in using the simple theory is small except for very short members. Experimental confirmation of the predicted configuration of slip surfaces in the web of an I beam is obtained by reference to tests performed by Frankl on welded connexions.