Chapter 4 - Minimum weight design

Abstract

This chapter discusses the minimum weight design. The process of design is one in which the load factor is required to have a given minimum value, and the plastic moments of the various members of the structure are required. When a design is required for a single set of loads, any bending moment distribution satisfying the equilibrium and yield conditions constitutes a possible basis for design. The chapter reviews minimum weight design using prismatic members, and the use of members of continuously varying cross section is discussed. If the weight line is tangential to the permissible region over a finite range, a range of minimum weight designs is possible. A design gives the minimum weight if it satisfies four conditions: (1) equilibrium condition, (2) yield condition, (3) mechanism condition, and (4) plastic hinge condition. The first three conditions are identical with those for the plastic collapse of any structure, and it is the fourth condition that imposes minimum weight.