The task of multi-criteria optimization of metal frame structures

Abstract

Optimal design of a frame structure with a specified geometric scheme consists in finding control parameters that provide the highest or lowest value of composite functions which present some quality criteria. Searching for optimal parameters is related to a number of design and calculation constraints. When it is necessary to vary a geometrical scheme, node coordinates are also considered as unknown varied parameters that affect the quality criteria. When designing frames with a specified scheme, the volume of material is typically the primary criterion for solving an optimization task and is written as a function of control parameters and state settings. In problem specification it is also important to reduce the deformation of the system. This is accomplished by introducing an additional criterion -maximum moments of inertia of the sections of the system. There is a two-phase design and calculation model existing in design practice now. In the first stage, the work is based on the experience or existing prototype. On their basis stiffness of the bars is assigned, and then a load vector is calculated. In the second stage, the sections are chosen according to known forces.