The flexural behaviour of slabs at ultimate load

The paper describes a lower-bound solution for the simply supported square slab under uniform load based on the assumption of elastic-plast ic behaviour of the slab material. It is shown that the elastic moments within the segments of a chosen yield-line pattern are everywhere statically admissible. The uniqueness of the load value is thus also established. The procedure is suitable for general application to slabs of varying geometry and loading and is capable of providing realistic ultimate-moment fields for the under-reinforced type of slab normally employed.