Thermal analysis of two-dimensional structures in fire

Abstract

The structural materials, as reinforced concrete, steel, wood and aluminum, when heated have their mechanical proprieties degraded. In fire, the structures are subject to elevated temperatures and consequently the load capacity of the structural elements is reduced. The Brazilian and European standards show the minimal dimensions for the structural elements had an adequate bearing capacity in fire. However, several structural checks are not contemplated in methods provided by the standards. In these situations, the knowledge of the temperature distributions inside of structural elements as function of time of exposition is required. The aim of this paper is present software developed by the authors called ATERM. The software performs the thermal transient analysis of two-dimensional structures. The structure may be formed of any material and heating is provided by means of a curve of temperature versus time. The data input and the visualization of the results is performed thought the GiD software. Several examples are compared with software Super TempCalc and ANSYS. Some conclusions and recommendations about the thermal analysis are presented

The effect of the failure of the steel roof on the facade concrete columns of a warehouse in fire. A study case

“…In Silva [10], for example, the isotherms for various sections of columns are presented in order to facilitate the manual calculation. These isotherms were performed using the ATERM software [13][14].…”

“…The thermal field in the concrete column and in the truss is carry out by the ATERM software [13][14]. The structural elements are submitted by the standard fire [15][16].…”

“…Figures 7 and 8 show the temperatures distribution for the 30 and 60 minutes of fire. The thermal analyses were carried out by the ATERM software [14][15]. The temperature distribution after 30 and 60 minutes of fire is was observed to be practically uniform.…”

On the use of parameter γ z in fire situation

“…In this work they will be. The permanent actions F gi,k can be of high or low variability, which affects its respective weighting coefficients in fire situation γ gi,fi and, at last, the non-exceptional variable actions F qi,k that remain acting on the structure, with relevant probability, during a fire have its respective weighting coefficients all equal to 1,0, thereby, equation (17) remains valid if rewritten as in equation (18).…”

“…Given the expression that relates the temperature of a concrete element with its elastic modulus at this temperature, the next step is to discover the temperature field in the element. Adopting the standard curve of fire temperature vs time ISO 834 [16], it was possible to determine the thermic field in the cross section of the columns and beams with the aid of the computer software for thermal analysis of structures by the finite element method Aterm [17], developed and validated by the second author of this paper. From the thermal field, the average temperature in each section was determined and this value was extended to the entire bar (column or beam), that is, a uniform temperature distribution along the bars was adopted herein.…”