Lateral torsional stability analysis of large order space frame systems

Abstract

In this paper the elastic stability of rigid space frames is investigated with the aid of the finite element method. The element stiffness matrix for second order (stability) analysis is formulated on the basis of open thin-walled element theory considering the coupling of torsional and flexural behaviour in three dimensions under the assumption of small deformations. A first order (static) analysis is done first in order to calculate the axial force distribution in the members, and the vanishing of the determinant of the global stability stiffness matrix is the criterion used to obtain the critical load of the structure. The rigid space frames investigated here by the proposed methodology consist of commonly used steel joists with horizontal or X-bracing connecting them. The effects of the support conditions and bracing configuration on the buckling loads of various steel joist systems are studied. Useful conclusions are drawn and comparisons with existing experimental results are made.