Validation of an analytical model for curved and tapered cellular beams at normal and fire conditions

The growing use of cellular beams in steel construction leads to the development of various configurations such as curved and tapered cellular beams. In order to provide a tool predicting the behavior of those beams for design applications, the CTICM developed a software based on analytical formulas with adaptation to the curved and tapered cellular beams. Recently, the analytical formulas were adapted to fire conditions. In this paper, a nonlinear numerical model is developed and performed to validate the analytical approach. The model is applied to curved and tapered beams considering various opening and support configurations in normal and fire conditions. The comparison between the numerical and the analytical results validates and shows the possibilities of the analytical model and its limits

Development of an Analytical Model to Determine the Heat Fluxes to a Structural Element Due to a Travelling Fire

peer reviewedThe term “travelling fire” is used to label fires which burn locally and move across the floor over a period of time in large compartments. Through experimental and numerical campaigns and while observing the tragic travelling fire events, it became clear that such fires imply a transient heating of the surrounding structure. The necessity to better characterize the thermal impact generated on the structure by a travelling fire motivated the development of an analytical model allowing to capture, in a simple manner, the multidimensional transient heating of a structure considering the effect of the ventilation. This paper first presents the basic assumptions of a new analytical model which is based on the virtual solid flame concept; a comparison of the steel temperatures measured during a travelling fire test in a steel-framed building with the ones obtained analytically is then presented. The limitations inherent to the analyticity of the model are also discussed. This paper suggests that the developed analytical model can allow for both an acceptable representation of the travelling fire in terms of fire spread and steel temperatures while not being computationally demanding, making it potentially desirable for pre-design

Modelling the influence of steel structure compartment geometry on travelling fires

The response of structures exposed to fire is highly dependent on the type of fire that occurs, which is in turn very dependent on the compartment geometry. In the frame of the European RFCS TRAFIR project, CFD simulations using FDS software were carried out to analyse the influence of compartment geometry and the interaction with representative fuel loads to explore the conditions leading to the development of a travelling fire. The influence observed of ceiling height, crib spacing, and opening geometry in controlling spread rates tend to confirm the possibility to predict the occurrence, or not, of travelling fire. The results of one CFD analysis are then used to perform a nonlinear thermomechanical analysis of a steel structure with SAFIR® software. Indeed, it is possible to use the radiative intensities and gas temperatures obtained with CFD to calculate with FEM the temperatures in structural elements located in the compartment, and to evaluate the structural behaviour of a frame made of these elements. This paper therefore highlights the effect of building design specifications on the temperature development and on the resulting mechanical behaviour of a steel structure that considers comprehensively the travelling nature of the fire.Peer reviewe

Experimental assessment of the effect of the real flame emissivity for steel elements engulfed into fire

peer reviewedThis paper presents the results of an experimental campaign performed to assess the effect of the flame emissivity for steel members engulfed into fire. In detail, two sizes of circular steel tubes were engulfed into pool fires of two different diameters. Two fuels were used and for both fuels tests without column (used as comparison with existing localised fire models) and with column were performed. The temperature of the column and of the flames were measured at different heights. The width of the flame was also measured and used to calculate the emissivity of the flame the value of which was employed in numerical simulations in order to predict the evolution of the temperature of the steel column. Comparison with numerical analyses where the recommended values of the Eurocode were used is also shown