Unified object-oriented definition of thin-walled steel beam-column cross-sections

Abstract

Nowadays the advanced software products for steel structural analysis prefer the finite element method based on 3D thin-walled beam-column elements. This method requires the analysis-oriented modelling of cross-section problem. On the other hand, the integrated design modules based on modern design standards like Eurocode 3 need the design-oriented approach. The design of class 3 shapes are based on the linear elastic properties used in analysis, while the design of class 1 and 2 shapes requires the plastic properties. Moreover, the design of class 4 shapes uses the effective cross-section model to take the local buckling into consideration. However, for the integration of the analysis and standard design we need an approach that covers both areas. Former solutions – mainly in the environment of the sequential or procedure-oriented programming – identify the cross-sections by their properties computed by explicit formulas. Other solutions use FEM approach to compute the properties defined from mechanics point of view. These techniques are in contradiction with the integrated analysis and standard design of structures – the mentioned approaches are not able to satisfy the standard design. This paper proposes a model-oriented approach for the integrated analysis of cross-sections that satisfies the requirements of both the advanced beam-column analysis and the automatic standard design procedure. During the integrated analysis-design procedure the different program components require different cross-section properties computed on different basic conditions. The elastic analysis used commonly in the standard design needs the nominal properties that are computed on the basic model. The geometric non-linear solution requires a refined model to compute the stress-dependent Wagner coefficient. To predict the resistance of structures or structural members by physically non-linear solution we need the strain-dependent tangent cross-sectional properties. The design of class 4 shapes needs the effective cross-sections. However, all the relevant computational models can be derived from the natural model. This fact has emerged the object-oriented approach of the problem. Each procedure can be based on the natural geometric model and on the nominal properties related to this model. The data structure and the procedures will be encapsulated in the basic class SECTION. The different procedures need new classes that aggregate the basic one. The paper presents the first result of the object based concurrent engineering methodology for steel structural analysis and design (OBCEMsteel) project that aims to develop the ConSteel prototype system for new generation software for standard design of steel beam-column structures.