The use of cold-formed steel members has increased significantly in the past few years; however, its design is only briefly addressed in the current design codes, such as the EN 1993-1-3. To evaluate the compressive behavior of single and built-up cold-formed steel members, at ambient and simulated fire conditions with restrained thermal elongation, experimental and numerical tests were undertaken.
Four cross-section shapes were tested, namely, one single (lipped channel), one open built-up (I) and two closed built-up (R and 2R), considering two end support conditions, pinned and fixed. Two test set-ups were specifically developed for these tests. Based on the experimental results finite element models were developed and calibrated to allow future parametric studies.
This paper showed that increasing the level of restraint to thermal elongation and the initially applied load led to lower critical temperatures. Increasing the level of restraint to thermal elongation, the failure is governed by the generated axial restraining forces, whereas for lower levels of restraint to thermal elongation, the failure is controlled by the temperature increasing.
This paper is a contribution to the knowledge on the behavior of cold-formed steel columns subjected to fire, especially on the ones with a built-up cross-section, where results on thermal restrained ones are still scarce. It presented a set of experimental and numerical results useful for the development of numerical and analytical analysis concerning the development of new simplified calculation methods.
