Some Factors in the Shear Strength of Reinforced Concrete Beams

THE PRESIDENT said the meeting would agree that they had listened to a very able introduction of a most informative paper. A good deal of work in connection with this subject had passed and was passing through Mr. Waters' hands and it was being dealt with in the efficient and quiet way which was symbolised by the efficient and quiet way in which he had introduced the paper.

The problems connected with the design of pile groups are often the subject of lengthy and complicated analyses. This applies particularly to pile groups which have to withstand relatively large horizontal thrusts, where the use of raking piles would be advantageous. Because of the indeterminate nature of piled foundation structures, an exact analysis of structural members has not yet been possible; and this presents a difficulty which is quite apart from the problems of soil mechanics involved. Investigations into the action of earth mass around piles and attempts to utilize the shear strength or the modulus of elasticity of soil for defining the ground resistance to horizontal thrust, do not appear to have yielded conclusive results of great practical value; and easily applied design methods have certainly not yet been derived from them. A. Kroie

The flexibility which is inherent in nominally rigid joints and footings in plane frames is known not to affect the value of the plastic collapse load. The object of the present paper is to show that substantial amounts of flexibility can often occur without affecting the deflections at the point of collapse, that is when the plastic collapse load has just been attained but no motion of the collapse mechanism has taken place. This is in striking contrast to the obvious increase in the deflections in the elastic range of behaviour when flexibility of any kind is present. Professor G. Neal