Critical Loads of Tall Building Frames (PART IV)

Mr. J. J. LEEMING (Member): Dr. Lightfoot’s paper deals with structures of constant section, and is to that extent misleading, because it is therefore one of those methods which tend to lead designers to fit their structures to their method of design.

IN a paper describing a series of full scale loading tests on a reinforced concrete uilding1 which was presented to the Institution some time ago an account was given of tests to failure which were made on reinforced concrete slabs spanning in two directions. The slabs were very lightly reinforced, but the ultimate loads found in the tests were much greater than had been anticipated, and exceeded the collapse loads calculated on the basis of plastic behaviour by a considerable margin. At the time it was not possible to account satisfactorily for the unexpected strength exhibited by the slabs. The results of the tests, however, have recently been re-examined and certain experimental investigations have been made. As a result a rational explanation of the behaviour of the two-way slabs at failure can now be put forward. A.J. Ockleston

Mr. G. SVED: I should like to congratulate Dr. Bray on his clear and comprehensive paper on the application of "An Electrical Analyser for Rigid Frameworks."