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Isolated steel columns, when exposed to high temperatures, lose strength in a few minutes due to the high thermal conductivity of its constituent material. When these structural elements are embedded in walls, the response to exceptional action is altered so that the compartmentation offers an increase in the fire resistance of the columns. Therefore, the purpose of this paper is to analyze the behavior of steel columns inserted in walls subject to thermal action in a numerical context.

For this purpose, the computational code ABAQUS version 6.14, which applies the finite element method formulation to solve engineering problems, was used.

The thermo-mechanical modeling, considering the wall only as a compartmentation element, generated few consistent results, leading to the conclusion that the walls influence the structural response of columns in a fire situation.

There is a lack of both numerical and experimental research works. In numerical modeling, the research works found in the literature had difficulties in developing a numerical model that satisfactorily represented steel columns inserted in walls, not being able to adequately understand their behavior at high temperatures. All of them did not consider the influence of masonry on the thermo-structural behavior of the columns. In this paper, this influence was evaluated and discussed.

This work presents the results of numerical analyses, both thermal and structural, of a pinned-pinned open cross section of a "U-shaped" cold-formed steel beam in a fire situation. The beam was in physical contact with a concrete slab and a masonry wall. The eventual partial compartmentalisation due to the wall was disregarded. The field of temperatures for the steel-concrete-wall elements was determined using the software programs Super Tempcalc and Ansys. For structural analysis the software Ansys was used. Restrictions due to the lateral displacement, the compatibility of transversal displacements at the points of contact between the slab and the beam, local buckling and restrictions to the thermal strains at the end supports were taken into account. Material and geometrical nonlinearities were considered, as well as the variation of the stressstrain diagrams with temperature, according to Eurocode prescriptions. The variation of the resistance reducer with the time of fire exposure was also evaluated. Based on the adopted model, the structure under standard fire exposure is not adequately safe. More research is under development to consider compartmentalisation and natural fire.