engleski

The Null Configuration Model in limit load analysis of steel space frames

The numerical model for the geometric and material nonlinear limit load analysis of steel space frames under large displacements is presented in this paper. A simple, global discretization using beam-column finite elements is preferred to a full, global discretization with 3D elements. The steel cross-section is discretized with 2D elements to apply the fiber decomposition procedure to solve the material and geometrical nonlinear behavior of the cross-section under biaxial moments and axial forces. A local discretization of each beam element is based on the comparative body model (i.e., a prismatic body discretized using brick elements, element by element, during the incremental-iterative procedure) allows determining the torsional constant of the cross-section under limited warping. The model implements well-known bending, lateral and torsional stability effects. For the large displacement analysis, an originally developed Null Configuration Model (NCM) is applied as an incremental application of the Total Lagrange - small displacement theory. A step-by-step procedure for the incremental loading of a follower load is applied. The numerical model has been implemented in a computer program for the practical engineering computation of the limit load of steel space frames. The practical application of the model is illustrated on presented examples.

Null Configuration Model (NCM); Geometric and material nonlinearity; Steel space frame; Fiber Element Method; Non-uniform torsion.

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