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Title: An investigation into the behaviour of steel proprietary support structures
Author: Wilkinson, Simon James
ISNI:       0000 0001 3568 5343
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2001
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Thin walled cold-formed steel components have favourable strength-to-weight, and strength-to-cost ratios. Unfortunately, classical structural theory cannot be utilised for many of the inherently complex non-uniform components available. The finite element method (FE) was adopted to provide a numerical approximation for a number of cold-formed structural fabrications. An orthogonally stiffened steel sandwich panel was modelled using a linear-elastic FE formulation, and benchmarked against full-scale laboratory test data. An accurate estimation of the stress state was only achieved after the interaction between the discrete support restraint and method of load application was appropriately defined. A more exhaustive investigation was carried out on column stability problems. The generalised eigenvalue extraction method within the FE formulation was adopted. For standard prismatic section geometries, the modal shape and critical load capacity, for both first, and higher order modes, with various end restraint conditions was predicted with a high degree of accuracy. In addition, a perforated cellular twin-web column was modelled. Its inherent non-uniform cross-section was transformed into an equivalent uniform cross-section with a missing central strip in the two symmetrical webs. Furthermore, the effective moment of inertia calculated for a particular pitch and hole diameter was independent of length. The effect of diaphragm plates on the structural performance of spaced, or battened types of column was investigated, and found that diaphragm joint rigidity substantially enhanced buckling capacity. Furthermore, even if the joints are only pinned, the end-plate stiffness still significantly increases buckling capacity. The FE formulation was adopted to evaluate the elastic critical load, and the moment of inertia of a proprietary soldier section. The study showed that the effective moment of inertia was dependent on length. A linear elastic beam formulation was adopted to verify the inertia value. An investigation into the effects of stacking the soldiers (bolting the modular lengths together through their end-plates), showed the influence of the end-plate stiffness, and that the number of diaphragm plates or end-plates within the length had a significant effect on the overall performance of the soldier, with the minor axis properties being more sensitive to this influence. The elastic stability and the linear idealised-plastic FE formulations were adopted to model the proprietary soldier prop. The investigation predicted an apparent load capacity discontinuity when the prop assembly make up changed from single modular lengths, to modular length combinations. This enhanced capacity was the effect of the greater number of bolted end-plates, increasing the stiffness of the section locally, and thus improving the overall performance of the prop. A series of four full-scale laboratory tests were undertaken to calibrate the FE formulation, and showed the props were sensitive to variations in initial geometry and material thickness. In terms of collapse load value, there was good correlation between the results for the single modular length soldier props. The correlation between the modular soldier combinations was not as close. These differences were due to the behaviour of the bolted connection, and in particular, the local movement within the joint itself. This relative movement had a significant impact on the value of collapse load because of the sensitivity of the initial geometry on the performance of the prop.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Thin walled cold-formed steel components; Column stability