AbstractThe presented work is concerned with the development of a grillage method for predicting the behaviour of steel multi-cell structures. Simply supported, straight and skew structures will be considered subjected to a variety of loading conditions. The proposed analysis can be achieved using a low cost micro-computer, and it is considered that the method will assist in the initial stages of design, where a number of alternative solutions may require investigation.
In the development of a two-dimensional grillage method for the analysis of a three-dimensional structure, the actual structural response under load must be modelled by the assemblage of rigidly-jointed beams that constitute the grillage structure. Multi-cell structures resist applied load by a combination of longitudinal bending, transverse bending, torsion and distortion. The development of the appropriate stiffness parameters for each grillage beam constitutes the major part of the investigation.
In a finite element study of skew single cell structures, recommendations for the determination of the effective breadth ratio for flange plates in skew structures are presented.
Numerous examples are presented for both single cell and multi-cell structures with straight and skew supports. The grillage results are compared with results from a finite element study. In the case of straight structures the grillage results for maximum web deflection agreed to within -5% and +6% of the finite element values. The results for maximum longitudinal flange stress are less accurate, the grillage method tending to overestimate the stress intensity, with a maximum overestimation of 16% of the finite element value.
The skew structure results using an orthogonal mesh idealization are less accurate. The degree of accuracy decreases with increasing angle of skew and also when the loading produces transverse hogging effects.
It is considered that the grillage method is capable of producing results to an acceptable degree of accuracy for initial design purposes.
|Date of Award||1986|