ABSTRACT
SUMMARY
Idealised approximations to material stress–strain relationships lead to corresponding idealised limit loads—in particular, the rigid–plastic collapse load and the least elastic critical load. The real behaviour, allowing for stability and change of geometry, causes a reduction of carrying capacity below the rigid–plastic collapse value. The extent of the reduction depends on the slendemesses of the members and may be related to the value of the elastic critical load. Justifications for the Merchant-Rankine load, and for the modification suggested by Wood, are discussed, and applications to unbraced multi-storey frames show the usefulness of this procedure. An example of the design of a multi-storey frame involving frame stability effects is given. Special frame stability problems in single-storey pitched roof frames are discussed, and safeguards are described and illustrated by reference to two design examples.
