Three-dimensional stability of steel frameworks

Raslan, Mohamed Saad (1987) Three-dimensional stability of steel frameworks. University of Southampton, Doctoral Thesis.

Abstract

This study is concerned with the investigation of the effect of joints on the three-dimensional stability analysis of framework structures composed of thin-walled elements. Warping behaviour in the vicinity of framework joints is an important consideration in such an analysis. The main objective is to develop a solution procedure for investigating the warping behaviour of framework joints as well as demonstrating its effect on the three-dimensional stability of framework structures.A finite element technique is proposed for determining the relationships between the warping parameters (warping displacements and warping moments) at a joint. The technique is based on modelling a joint by a number of area elements with suitable stiffness proporties. The stresses and deformations resulting from the analysis of the finite element model are then used to obtain these relationships.The validity and accuracy of the finite element solution have been examined by analysing a number of problems for which exact solutions by other methods are available. The technique is also applied to study the warping behaviour of two joints which are of practical importance. Moreover, the finite element solution is compared with experimental observations taken from a test on a large-scale model of a joint and the comparison shows a good correlation between both results.The relationships of the warping parameters at rigid joints are then incorporated into a general three-dimensional stability analysis of framework structures by modifying an existing finite element stability formulation. Several illustrative examples are solved in order to assess the effect of the joint's warping behaviour on the buckling capacity of framework structures.Finally, an experimental program was developed to verify the theoretical predictions. Tests were conducted on a large-scale steel portal frame model to study its three-dimensional behaviour. Particular attention was focused on evaluating the effect of the warping behaviour of the joints and the stiffness of the secondary members on the buckling strength of the model. (D81026)

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