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.