Verulam

Dr J. W. Dougill (F) (Director of Engineering, IStructE) We have these distributions of normal contact stress across the width of the footing, and you say that ‘of course, it is zero at the edge’. I am a little puzzled about this, although I may have misunderstood. Certainly, if the behaviour were not elastic, there is not any reason why it should be zero at the edge. Indeed, if you had a singularity you would need it to be zero at the edge. Is there some other overriding reason why this contact stress should be zero?

Reinforced concrete deep beams with partially or fully fixed end conditions are more likely to occur in practical structures than simply supported end conditions. Tests carried out on eighteen beams over a range of geometrical parameters identified three modes of failure: flexure + shear, shear or diagonal splitting, and bearing. A simple method is proposed for the analysis of deep beams with fixed end conditions. The method is based on the assessment of strength for the different modes of failure and on maintaining the equilibrium of forces in all parts of the structure. The method is capable of predicting the mode of failure and the ultimate strength of the beams. The predicted modes of failure compare well with the experimental observations. The ultimate strengths from the analysis predict safer and, in a few cases, conservative values. A design method may be developed using the proposed method of analysis. N.K. Subedi