Design of steel portal frame buildings for fire safety

Abstract

This paper describes a study into the fire behaviour of steel portal frame buildings at elevated temperatures using the finite element programme SAFIR. The finite element analysis carried out in this report is three dimensional and covers different support conditions at the column bases, the presence of axial restraints provided by the end walls, different fire severities within the building, different levels of out-of-plane restraint to the columns and the effect of concrete encasement to the columns. From a large number of analyses, it is shown that the bases of the steel portal frames at the foundations must be designed and constructed with some level of fixity to ensure that the structure will deform in an acceptable way during fire, with no outwards collapse of the walls. The analyses also show that to avoid sidesway (i.e. collapse outwards) it is not necessary for steel portal frame columns to be fire-protected unless the designer wishes to ensure that the columns and the wall panels remain standing, during and after the fire.

Resistencia al fuego de pórticos simples de acero a dos aguas

“…Moss et al (11), en base a la normativa neozelandesa y procedimientos constructivos de ese país, realizan un exhaustivo análisis 3D para determinar el modo de colapso y tiempo de resistencia al fuego de pórticos a dos aguas.…”

Complex and comprehensive method for reliability calculation of structures under fire exposure

“…The failure of the purlins and sheeting is not considered here, although they lose their load bearing capacity very early because of the thin wall and high section factor, but due to the relatively low loading and the possible catenary action [39] (similarly to composite floor slabs [40]) they may not fall down. The serious deformation and damage of sheeting seems unavoidable in fire design situation.…”

Effect of column base strength on steel portal frames in fire

“…Figure 18. Details of the frame idealisation with restraints of the portal frame by Moss et al (2009) andBong (2005) For the case of fire scenario B (see Figure 22(b)), in order to keep the amount of restraint provided by the purlins the same as that of fire scenario A, with two frames at both ends providing restraint, seven frames are modelled, of which the middle three are in fire. Similarly, for the case of fire scenario C (see Figure 22(c)), nine frames are modelled.…”

“…Bong (2005), as described by Moss et al (2009), conducted a three-dimensional (3D) non-linear, elastic-plastic, implicit dynamic finite-element analysis of a portal frame building in fire using the finite-element program Safir. The building was designed in accordance with New Zealand practice (SNZ, 1992(SNZ, , 1997, with the lower half of each column encased in concrete and the top half exposed to fire.…”