Collapse behaviour of steel columns in fire.

The three years' work undertaken in this project is a purely numerical analysis
of the inelastic behaviour of steel columns in fire. This is made up of three
main parts, each devoted to the development and use of a numerical technique
to study the behaviour of steel columns in fire. The first two chapters report
on the state of the art on plate analysis, plasticity theories, column behaviour
at room temperature, finite strip method and the behaviour of columns at
elevated temperature.
Part 1, consisting of Chapters 3 to 5, reports on the development of the
small deflection finite strip method which includes the effect of plastification
of component plates using deformation theory of plasticity. The validity of the
method is tested by comparing with published test data on steel columns at
ambient and elevated temperature. The comparisons show that the method
gives good correlation with test data. Parametric studies have been carried out
to assess the effects of slenderness ratios, different stress-strain-temperature
representations, residual stresses, eccentricity of loading and local budding of
columns. In addition the inelastic behaviour of an H-section under uniform
end couples is studied.
Part 2, consisting of Chapters 6 and 7, reports on the development of a finite
element method which includes the effect of thermal gradients over the member
cross-section. The method is compared with test data on both uniformly and
non-uniformly heated columns. This shows a good correlation between the
method and experiment. Parametric studies have been carried out to assess the
effects of initial out-of-straightness, different end conditions, thermal gradients and interaction of eccentricity of loading with thermal gradients on columns.
In addition a simple Shanley's column theory is utilised to demonstrate the
interaction effect of eccentricity of loading with thermal gradients on columns.
Part 3, consisting of Chapter 8, reports on the development of a large deflection
finite strip method which includes flow theory of plasticity. The method has
not been used for any parametric study.
Finally, general conclusions and recommendations for future works are presented in Chapter 9. It is hoped that the valuable information provided in
this thesis will be useful in providing a better understanding on the real behaviour of steel columns in fire.