Light timber framed wall under fire: effect of the load and cladding

Light Timber Frame Walls are made of solid timber elements and are usually protected by cladding materials (gypsum). This investigation finds the effect of different load levels and cladding systems on the fire resistance. The timber frame structure is made with three studs and two rails, and will be analysed with two different protection levels. The computational model includes the thermal analysis under standard fire and a sequential mechanical analysis with time increments. Both, thermal and thermo-mechanical models are validated against experimental results developed in the reduced scale and full scale. The timber frame structure is deemed to have failed when it is no longer supporting the test load. The results are also compared with the failure criteria used for the experimental tests. The timber frame is deformed and all simulated models attained the global bucking instability mode, with studs moving to the outside of the furnace, due to the effect of load and charred layer. The fire resistance of a double-layered light timber frame wall is higher than a single-layered, and both decrease with the load level. This ability is reduced by 46%, on average for all load levels, when using only one gypsum layer. A new formula is proposed to determine the fire resistance, based on the load level and cladding systems. The fire resistance of the specimens with two layers of gypsum plates decreases faster than the specimens with one layer of gypsum, with respect to the increase of the load level.info:eu-repo/semantics/publishedVersio

The fire resistance of light timber frame walls with different load levels and cladding layers

Lightweight Timber frame walls (LTFW) are commonly used in residential buildings due to their light weight and low construction costs. LTFW are made with solid wood members (studs and tracks) used on buildings, for load-bearing and partition walls. The assemblies are made with solid stud wood vertical members, usually separated by 400 to 600 mm. The cladding for internal walls may be developed by wood panels, composite panels and or gypsum panels. The number of protection layers and insulation materials used in the cavity of the wall depends on the thermal and acoustic efficiency required to the LTFW at room temperature, but also depends on the required fire rating of LTFW.info:eu-repo/semantics/publishedVersio

Timber framed walls lined with gypsum plates under fire

Building regulations require fire rating for partition walls under standard fire exposure. New eco building solutions are becoming popular and, in particular, the light timber framed walls. The fire rating of this building element depends on fire testing. Finite element approximation can be used, when models are validated from previous experimental tests. This investigation presents the validation model from a full-scale assembly, using one gypsum board on each side and several solid timber studs. The charring rate in the wood studs is an important predictor for the fire performance of the wall and as well the temperature of the unexposed surface. This investigation also predicts the temperature field in other key points, such as the points located in interface between the studs and gypsum board, for the onset of charring. Finally, the fire resistance is also considered by means of the simplified method (improved model). This models seems to under predict and over predict the results. There is a good approximation between the numerical model (Hybrid –FEM) and the experimental test used for validation, which allowed for a parametric analysis, testing the variation of the gypsum thickness and the thickness of the cavity. The dimension increase of the wood stud does not provide almost any change on the fire resistance of the assembly (insulation), but provides significant modification on the residual area for load bearing capacity.info:eu-repo/semantics/publishedVersio

A simple model for lateral torsional buckling resistance of steel I beams under fire condition – comparison with experimental results

When a beam is bent about its axis of greatest flexural rigidity it may twist before it reaches its strength limit state. This flexural stability limit state is most commonly referred to as lateral torsional buckling of a beam. The twisting of the beam occurs when the compression flange becomes unstable as a result of its being subjected to flexural induced axial stresses. Lateral torsional buckling is of importance when the compression flange is laterally unsupported as is often the case in continuous beams, cantilever beams, frame beams and frame columns. The aim of this work is to develop a simple model, i. e., an analytical method to be used by designers for the calculation of the resistance moment of steel I-beams failing by lateral torsional buckling when submitted to the fire. A particular attention has been paid to the possibility to use the same model as the one proposed in Eurocode 3 – Part 1-1, simply modifying material properties according to the temperature. This is the procedure currently proposed in Eurocode 3 – Part 1-2, although its accuracy has never been demonstrated and can indeed be questioned. Due to the fact that higher temperatures usually develop at the end of the flanges than in the rest of the section, the decrease of the bending stiffness in case of fire is faster around the weak axis than around the strong axis of the section. The method has been developed from a set of experimental results performed at elevated temperatures. As it is known any analytical, numerical or theoretical model is much more likely to be accepted if it is backed and supported by a set of experimental tests. Comparison of the simple model has been made with laboratory test results obtained in the framework of this work. A set of experimental full-scale tests were performed on IPE100 profiles at elevated temperature for several length specimens from 0.5 meter to 6.5 meters of buckling length. Residual stresses, geometrical imperfections and material strength were measured for each tested element. The load was applied after the heating of the beams. The beams were electric heated by means of ceramic mat elements. Automatic control on different heating devices was presented in order to ensure a uniform temperature distribution along the length of the elements. The temperature field has been measured with thermocouples welded on the beams. A Set of experimental results are presented, relating the critical load with the mid span movement of the beam cross section, when submitted to a constant moment distribution and to a uniform distributed load, due to the ceramic mat and the insulation material weight

Medição de campos de tensões recorrendo à técnica de Moiré

Neste trabalho é apresentada uma aplicação da técnica de Moiré para a medição de campos de tensões. O caso em estudo consiste na medição do campo de deslocamentos na superfície de um provete sob tracção, possuindo um furo passante no seu centro. As redes são obtidas por impressão laser num papel especial. A replicação da rede na superfície do provete é feita por um processo térmico com pressão controlada. Foram ensaiados provetes de alumínio. A rede registada na superfície do provete foi fotografada em diferentes fases do ensaio, estas fotografias são tratadas num programa de processamento de imagem. Os valores obtidos experimentalmente são comparados com os valores calculados com o código de elementos finitos ANSYS

Towards a predictive model for incoming thermal fluxes during a fuel warehouse fire

The prediction of released heat fluxes from fires is mandatory for any fire safety strategy. Indeed, the spreading time and directions of thermal fluxes are particularly critical in the situations of fuel warehouses, where temperature levels can induce primary and secondary inflammations in the neighbouring depots. Moreover, firefighters should operate in areas where the thermal environment is tolerable and in favour of efficient egress operations. Several correlative models provided by some industrial organizations are applied to the study case of Naftal-Chiffa fuel warehouse (Blida, Algeria). Various fire characteristics are predicted, in particular height and inclination of jet flames, in addition to the spatial distribution of heat fluxes on solid targets (human bodies and structures). The analyses reveal that the safety distances corresponding to the threshold fluxes of 3 kw/m2, 5 kw/m2 and 8 kw/m2 as provided by the IT-89 correlations, exhibit an important dispersion when relative humidity was different from 70% and the fuel tank was had no longer a square shape. In this direction, the present study was completed with a parametric analysis on the effects of climatic conditions (ambient temperature, relative humidity, wind speed) and storage tanks geometry on the distances relates to critical thermal fluxes.info:eu-repo/semantics/publishedVersio

Simulação numérica dos efeitos térmicos resultantes de um incêndio localizado

Faz-se a simulação dos efeitos térmicos, resultantes do incêndio de um carro, sobre a laje em betão situada no teto de um compartimento fechado.info:eu-repo/semantics/publishedVersio

Medição de campos de tensões residuais: estudo preliminar

Este trabalho tem em vista o desenvolvimento de uma técnica experimental para medição de tensões residuais que possa ser uma alternativa ao clássico método do furo. Para caracterizar os campos de deformação nas proximidades do furo prevê-se a utilização do método de Moiré. Trata-se de uma técnica de campo que permite medir sem contacto, deslocamentos no plano, com uma resolução que é condicionada pela frequência espacial das redes. As técnicas para a gravação das redes nas superfícies dos objectos são descritas e caracterizadas. É também apresentada a montagem de interferometria laser utilizada para gerar, de forma controlada, a rede necessária à interrogação. Técnicas experimentais e numéricas são utilizadas para determinar as constantes de calibração ( A e B ) usadas no método do furo. Para isso é analisado, com detalhe, o campo de tensões na vizinhança de um furo cilíndrico resultante da tracção uniaxial no plano, aplicada a uma placa fina