Some Unusual Structural Features in Recent Building Construction

A meeting of the Institution was held at 11, Upper Belgrave Street, London, S.W. 1, on Thursday, 14th December, 1939, for a discusion on “ The Application of A.R.P. to Future Buildings. THE PRESIDENT (Mr. P. J. Black, M.I.Struct.E., L.R.I.B.A.) occupied the chair and opened the discussion.

It is well known that if a concrete beam be loaded a number of times to the same load the deflections will diminish with the number of repetitions of the load and the permanent set will increase with the number of loadings. Within considerable ranges of stress however the deflection will soon become constant. Beyond certain stresses and given time it is also well known that creep takes place and further that changes of form may take place due to creep. During a first loading the modulus of elasticity does not remain constant, but after a certain number of loadings within certain ranges of stress a straight line load-deflection curve is obtained in ordinary times of loading. A number of workers have shown that when a concrete beam has been loaded a considerable number of times to specified maximum stresses the static breaking load of the beam is not affected. Emeritus Professor F. C. Lea