Flexural behaviour of axially and rotationally restrained cold-formed steel beams subjected to fire

• Flexural behaviour of cold formed steel beams at high temperature studied.
• Single and compound cross-sections considered.
• Influence of the axial and rotational stiffness in fire analyzed.
• Critical temperature of beams affected by the surrounding structure stiffness.
• EN1993-1-2:2004 design methods may be inadequate for class 4 cross-sections.

This paper presents the results of a wide-ranging experimental research carried on the flexural behaviour of cold-formed steel beams subjected to fire. The main purpose of this work was to evaluate the influence of different cross-sections, especially of compound cold-formed steel sections, the axial restraint to the thermal elongation of the beam and the rotational stiffness of the beam supports. The results showed above all that the critical temperature of a cold-formed steel beam might be strongly affected by the stiffness of the surrounding structure depending on the relation between its stiffness and the stiffness of the beam.