Analysis of catenary action in steel beams using a simplified hand calculation method, Part 1: theory and validation for uniform temperature distribution

This and the companion papers present, in detail, the development and validation of a simple analysis method of catenary action in steel beams at elevated temperatures, which may be adopted as the basis of a design calculation method. Although the analysis is suitable for beam behaviour over the entire temperature region, the present discussions will emphasize on catenary action. The main assumptions of the analytical model are the beam's deflection profile and interaction between axial load and bending moment. The beam's deflection profile depends on its loading condition and end rotational restraint. For simply supported beams under distributed load or beams with complete end rotational restraint, the beam deflection profile may be assumed to be a polynomial that satisfies the beam's geometric boundary conditions. For simply supported beams under point loads, the beam's deflection profile may be assumed to take the shape of its free bending moment diagram. For flexible end rotational restraints, linear interpolation may be adopted as a function of the degree of end rotational restraint. For combined axial load and bending moment, the proposed analysis allows the beam's axial load to change in isolation and the beam's bending moment is then calculated from the axial load-bending moment interaction equation. This is a simplifying assumption that does not comply with stress distribution in the beam. It will be found that this method will predict higher catenary forces, which is on the safe side. This paper will present validation studies, by comparing results of the proposed method and numerical simulations using ABAQUS, for beams with uniform temperature distribution. The companion paper will give additional equations to be used in the proposed method and validation examples for beams with non-uniform temperature distributions.