Abstract
ABSTRACT: The design of steel and steel and concrete composite columns in a fire situation is directly linked to the reduction of strength and stiffness, among other properties, which are manifested in response to rising temperatures. The normative codes that deal with the design of these elements under the action of fire consider the thermal action based on heating on the four faces of the column, an aspect that does not cover most cases in buildings due to the presence of walls. In this context, given the importance of the correct determination of the thermal field for design purposes, as well as given the simplification adopted by the normative codes, the present work deals exclusively with a study basically aimed at obtaining a representative thermal field for purposes of thermo-structural verification of steel and steel and concrete composite columns. With the focus on the analysis of cases that differ from the prescribed configurations in standards, purely thermal numerical models are proposed, validated through experimental results, whose analyses show an evident reduction in temperature in the steel column when encased with concrete, and with even greater evidence when additionally inserted into walls as a compartmentalizing element. To verify the simplified method proposed by ABNT NBR 14323: 2013, comparative analyses between the numerical thermal fields and obtained by the standardized model were carried out for steel and steel and concrete composite cross sections. For the isolated steel columns, as expected, the normative method proved to be consistent, but conservative when it came to columns inserted into walls. In relation to the composite columns, the results obtained indicate the need for adjustment in the standards for purposes of determining the thermal field and, consequently, of design these elements.
Highlights
Concrete and steel are widely used in civil construction
EVALUATION OF NORMATIVE MODELS TO OBTAIN TEMPERATURE IN STEEL AND COMPOSITE PROFILES. This item evaluates the simplified method recommended by Brazilian standards ABNT NBR 14323 [3] and European Eurocode 3 and 4 Part 1-2 [4], [5] for calculating temperature in steel and concrete composite profiles partially encased when subjected to the action of fire
When comparing similar positions of steel columns and steel and concrete composite columns, it was possible to note a reduction in temperature in the latter elements as a consequence of the concrete properties
Summary
Concrete and steel are widely used in civil construction. The perception of the efficient work developed individually by these materials allowed the appearance of composite elements of steel and concrete, which started to be used to bond the advantages brought by both materials. Considering the above, the present work seeks to study the influence of the filler concrete between the flanges and the masonry wall in determining the thermal field developed in the cross section of steel and steel and concrete composite columns partially encased inserted into walls, in situations of fire. The present text focuses only on the analysis of temperature levels, this analysis is of fundamental importance for the purposes of design since the thermal field is determinant in a thermo-structural context For this purpose, thermal numerical models developed with the aid of ABAQUS are proposed, whose numerical results are validated through experimental results presented in Rocha [7], allowing evaluations in relation to the temperature field and the thermal gradient presented by these elements under high temperatures. The other models were built in a similar way, changing only the dimensions of the cross section, the thickness of the compartmentalization elements and the presence or not of masonry and concrete
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