download: 1018-7118-3-PB (1).pdf .The behavior under fire conditions of composite steel and concrete beams, not subjected to local buckling (compact steel profile), was studied considering the support rotational stiffness provided by the upper longitudinal slab reinforcement, usually present by means of anti-cracking meshes, and restriction of the steel profile’s lower flange, additional procedure required for development of the support bending moment resistance. Usually composite beams at room temperature are designed as simply supported and the semi-rigidity provided by this longitudinal reinforcement, if considered under fire conditions, may lead to a lower cost solution for fire protection of composite beams. The purpose of this study is to verify the viability of this proposal, using simplified design code methods.Leia Mais
Vigas de aço tendem a expandir longitudinalmente quando submetidas a temperaturas elevadas. Em situaçõesreais, esse deslocamento axial é impedido por estruturas adjacentes que ainda podem aplicar restrição à rotação de acordo com o tipo de ligação existente. Essa interação entre os elementos favorece o surgimento de esforços internos que influenciam o comportamento da viga, a qual já apresenta capacidade resistente reduzida em resposta à degradação térmica de suas propriedades físicas e mecânicas. O objetivo desta pesquisa é simular numericamente o comportamento de vigas de aço com restrições axial e rotacional nos apoios em situação de incêndio. A análise numérica foi realizada no código computacional ANSYS v17.0, considerando‐se as não linearidades geométricas e do material.
download: 832-6585-3-PB.pdf .Ultimate limit state curves of short reinforced concrete columns in fire situation are going to be presented in this paper. The authors created a code developed in Matlab. It makes a discretization of the cross sections of the columns and calculates the equilibrium integrals of them. The curves were plotted with the code considering the 500 °C isotherm method.Leia Mais
download: 836-5677-3-PB.pdf .Obtaining internal load capacity, in reinforced concrete sections, at ambient temperature, under biaxial bending, is one of the most common tasks done by structural engineers, but not so common when the member is in fire situation. The intention of this paper is to show that is possible to correlate the ultimate limit state (ULS), in fire situation, with ULS at ambient temperature, for square cross sections under fire from all faces. To reach the purpose and give support to the numerical analysis of this article, a computer program, in Delphi language, called COL FIRE, is being developed by the authors.Leia Mais
download: 866-5795-3-PBenglish.pdf .In many situations, the Brazilian Legislation does not require verification of roof structures in a fire, since its failure will not endanger the stability of the structure. In fire, the steel roof of an industrial building deforms by heating in geometry similar to a catenary, resulting in horizontal forces in the upper extremities of the columns. Thus, even roofs that do not constitute a frame with the columns may lead them to collapse, therefore, should be protected against fire. Due to the small dimensions of the structural elements of the roof, fire coating is uneconomical. So there is a problem in the design practice. This paper presents a procedure based on British literature, which considers the horizontal load on the columns. This horizontal load must be supported by the columns and the foundations. The aim of this paper is to detail this procedure, adapt it to Brazilian standards and apply it to a case study.Leia Mais
download: 887-6167-4-PB.pdf .The Brazilian standard ABNT NBR 15200: 2012 details a procedure for decreasing the required time of fire resistance in buildings with good fire safety characteristics. It called equivalent time method. This name can confuse the less habituated to the fire safety area, because the Brazilian procedure is not equal to the original equivalent time method, European. The purpose of this paper is to discuss the equivalent time method, to detail the origins of the Brazilian method and present their limitations no explicit in the Brazilian standard. Some unknown aspects of most researchers or technical means are presented. It should be highlighted the abundant bibliography presented to aid the understanding of a seemingly simple issue, but it incorporates many concepts of fire safety, not always understood by the users.Leia Mais
To design a steel structure in fire is necessary to know its temperature. Using the data from many experimental fire tests, Margaret Law estimated the maximum temperature in a compartment (natural fire), the external heat transfer to steel elements and the maximum temperature value for steel. The Eurocode adopted her method, with minor adjustments. The method is very calculation intensive—it involves about 60 equations— too many for a quick hand calculation. Besides, while a distinction is made between steel members engulfed and not engulfed in flame, the method is not clear about partially engulfed members. The authors developed the software ExteelFire to determine the maximum temperature of external steel structures for buildings in fire based on the Eurocode method including the determination of the temperature of the partially engulfed elements. Aiming to ascertain the level of safety of the Eurocode method, the results from ExteelFire and a numerical analysis performed using Smartfire (CFD software for the fire model) and Super Tempcalc (finite element method, FEM, software for the thermal analysis) were compared. Furthermore, results from ExteelFire and from two full-scale experimental tests (Dalmarnock and Ostrava) were contrasted. Based on the comparisons, the Eurocode method is conservative.
Foram pesquisados alguns dos mais importantes países da América Latina e as informações sobre sua legislação são apresentadas no artigo
The Brazilian standards of structures in fire prescribe minimum dimensions for the ribbed slabs to ensure fire resistance. However, a new composite ribbed slab is not covered by any of the Brazilian standards in fire. The objective of this work is to present unpublished results from numerical and thermal analyses for this type of slab. Ribbed slabs filled with cell concrete blocks, ceramic bricks and EPS supported by cimentitious board were studied. The constructive element is considerate as thermal insulation if it has the capacity to prevent the occurrence, on the face non exposed to fire, temperature increments greater than 140 °C on the average or greater than 180 ºC at any point. The support function was determined limiting the temperature of the beams and slabs rebars to 500 ºC. The analyses were carried out with the ATERM and Super Tempcalc, software for two-dimensional thermal analysis by means of the finite element method. As a result, tables will be presented that link the fire resistance required time to slab dimensions and position of rebar. Prior to use in designing these results must be confirmed by experimental analysis, which is already being provided.
An essential component of a composite beam is the shear connection between the steel section and the concrete slab. Contrasting to the great quantity of push-out tests carried out at room temperature, a reduced number of push-out tests at elevated temperatures has been reported. Comparisons of temperature development in two different types of specimens are made between existing test results and numerical simulations using the finite element package SuperTempcalc. Values for the thermal properties of materials, the heat transfer coefficient and emissivity recommended in EN 1991-1-2 and EN 1994-1-2 were taken as essential references. The sensitivity of the calibrated model to variation in connector diameter and height is assessed, taking into account the defined scope of the formulations of the above mentioned codes. Also, different alternatives on the level at which should be considered the concrete temperatures are evaluated. The parametric numerical studies demonstrate that the connector height, the concrete compressive strength and the level in which the concrete temperature is considered, have a great influence on the resistance, specifically when concrete failure prevails against stud failure.