Axially Restrained Steel Beams with Web Openings at Elevated Temperatures, Part 2: Development of an Analytical Method

The companion paper has presented the results of an extensive numerical study to investigate the behaviour of axially restrained steel beams with web opening, and to identify how the key quantities of the behaviour are controlled by different design parameters, including size and location of the opening, level of axial restraint, load ratio and temperature distribution. This paper uses the numerical simulation results to derive an analytical method to evaluate the key quantities, including the initial slope of the beam axial force – temperature relationship (rate of increase in compressive force with respect to temperature increase), point of initial buckling of the Tee-section under compression, transition temperature from compression to tension, the maximum tensile force and the corresponding temperature.
For practical design, the beam’s limiting temperature is calculated without consideration of axial restraint. At this temperature, since there may be considerable axial tensile force in the beam with web opening, it is important to check the capacity of the connections against the maximum tensile force, which can be calculated accurately using the proposed method.