DETERMINING SERVICEABILITY DEFLECTIONS IN PLASTICALLY DESIGNED STRUCTURES

Methods for determining the deflections at service loads in plastically designed structures are presented. A number of approaches to calculating these deflections are considered, since the usual method of performing a completely separate elastic analysis of the plastically designed structure is generally very cumbersome unless a computer is available. The alternative methods considered are: (a) direct estimation from plastic bending moment distribution; (B) correction approach; (C) exact calculation using a newly developed theorem; and (D) an approximate procedure using estimates of the bending moment diagrams for use in the unit dummy load method. Several examples are worked to illustrate the methods. It is shown that method (C) is a powerful direct and accurate technique for most simple structures (A). (TRRL)