CEPAO—an automatic program for rigid-plastic and elastic-plastic analysis and optimization of frame structures

Abstract

The computer program CEPAO handles the plastic design and analysis of plane frame structures. Classical finite element techniques combined with linear programming are used. In the plastic limit analysis, the program gives the collapsed load, the distribution of the bending moments, the normal forces, the shear forces, and the collapsed mechanisms of structures with proportional loading. Concerning stable design, the program finds the practical discrete profiles existing in Euronorm or American norm of different elements of the structure with minimum weight. The force distributions and the mechanism of the optimum state are given. The different stability conditions proposed by the European Convention for Constructional Steelwork (ECCS) are verified a posteriori to obtain, finally, a safe structure. From the fact that the European Convention recommends a limitation of elasto-plastic deflections, a step-by-step program is combined with the optimization procedure to obtain an elasto-plastic analysis of the stable structure. The program may also consider the analysis and design of frame structures under variable loadings. Efficient linear programming formulations are adopted in such a way that all necessary information, such as residual stresses, plastic deformations and optimum mechanisms, are obtained directly in the output. CEPAO may also design concrete reinforced structures (optimal limit design) where full redistribution of moments serviceability and rotation capacity of critical sections are taken into account.