Browsing by Author "Khetata, Mohamed S."
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- Analysis of the critical temperature on load bearing LSF walls under firePublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos-Gavilán, Ana B.Light Steel Frame (LSF) walls are widely used in building structures, used as partition walls and load bearing walls. The LSF is usually protected by layers of homogeneous plates or composite plates, with or without insulation materials in the cavity. This investigation presents the simulation results of composite LSF walls in reduced scale and full scale, based on variable load levels (20 to 80%). The numerical model uses a hybrid model approximation, based on the experimental tests to accurately determine the temperature field. The numerical model is validated with experimental results, at reduced and full scale, both at room temperature and under fire conditions. This modelling technique can follow the thermal and mechanical degradation of the protection layers of the LSF wall and determine the fire rating for load bearing (R) and insulation (I). The fire resistance (R) decreases with the increase of the load level. The insulation ability is also predicted for different protection materials. Relevant conclusions are presented to increase the insulation ability of LSF walls, especially when using non combustible double protection layers. The insulation ability to sustain fire usually increases with the number of studs and with the application of insulation material in the cavity region. The ability to sustain the load under fire also increases with the number of studs, especially for higher load levels. The ability to sustain the load also increases with the number of protection layers, changing from 16% at 20% load level, to 42% at 50% load level. A new proposal is presented for the critical temperature of the LSF, based on the maximum temperature of the LSF during the fire, allowing the calculation of the critical temperature, based on the load level of the specimen. This relation can predict the fire resistance time, based on the preliminary thermal analysis of the specimen. The reduced scale specimens present higher critical temperatures when compared to the full scale specimens, due to the typical failure mode (local modes for the reduced scale and global modes for the large scale).
- Critical temperature of load bearing LSF walls under firePublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos-Gavilán, Ana B.Light Steel Frame (LSF) walls are widely used in building structures, used as partition walls and load bearing walls. The LSF is usually protected by layers of homogeneous plates or composite plates, with or without insulation materials in the cavity. This investigation presents the experimental and the simulation results of composite LSF walls in reduced scale and full scale, based on variable load levels (20 to 80%). The numerical model is validated with experimental results, at reduced and full scale, both at room temperature and under fire conditions. This modelling technique can follow the thermal and mechanical degradation of the protection layers of the LSF wall and determine the fire rating for load (R) and insulation (I). The fire resistance (R) decreases with the increase of the load level, being the critical temperature of the steel structure presented by the maximum temperature of the Hot Flange (HF). A new proposal is presented for the critical temperature of the LSF, based on the maximum temperature of the LSF during the fire. The insulation ability is also predicted for different protection materials. Relevant conclusions are presented to increase the insulation ability of LSF walls
- Fire performance of non-loadbearing light steel framing walls – numerical and simple calculation methodsPublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos Gavilán, Ana BelénLight steel frame and prefabricated panels are widely used in non-loadbearing walls, with direct application to steel framed buildings. Such panels consist of channel steel sections (studs and tracks) with gypsum plasterboard layers attached to the flanges on the outside and use insulation material in the cavities. The fire resistance is usually provided by one or more layers of panels and also by the insulation material.
- Fire performance of non-loadbearing light steel framing walls - numerical and simple calculation methodsPublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos Gavilán, Ana BelénLight steel frame and prefabricated panels are widely used in non-loadbearing walls, with direct application to steel framed buildings. Such panels consist of steel sections (studs and tracks) with gypsum plasterboard layers attached to the flanges on the outside and use insulation material in the cavities. The fire resistance is usually provided by one or more layers of panels and by the insulation material. This investigation evaluates the thermal behaviour of the unexposed surface and of the nodal internal layers, using numerical simulations and a simple calculation method, assuming that heat flow is almost one-dimensional. The fire resistance is compared for both models using a cross section of the wall with one and two gypsum layers. The insulation criterion is the only one used for the calculation of the fire resistance, based on the calculation of the average and maximum temperature of the unexposed surface above the initial average temperature. Good approach was achieved by the simple calculation model, when optimum effective width is assumed for the model.
- Fire performance of non-loadbearing light steel framing walls – numerical simulationPublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos Gavilán, Ana BelénLight steel frame and prefabricated panels are widely used in non-load-bearing walls, with direct application to steel framed buildings. The fire resistance is usually provided by one or more layers of fire protection materials and the assembly is able to achieve a fire resistance in accordance to technical regulations. Many different types of board materials can be used, including gypsum-based boards. This investigation evaluates the behaviour of the cavity, with and without insulation material. The finite volume method is applied to perform the thermal analysis of the wall taking into account the fluid effect in the cavity. The finite element method is applied to perform the thermal analysis of the wall with insulation material in the cavity. The fire resistance is compared for both models (with and without insulation) and a new simple formula is proposed for the temperature evolution in the cavity zone. Some insulant materials can reduce the fire resistance of the wall, taking into to consideration the insulation criterion.
- Fire performance of non-loadbearing light steel framing walls – numerical simulationPublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos Gavilán, Ana BelénLight steel frame (LSF) and prefabricated panels are widely used in non-load-bearing walls, with direct application to steel framed buildings. The fire resistance is usually provided by one or more layers of fire protection materials and the assembly is able to achieve a fire resistance in accordance to technical regulations. Different types of board material can be applied, including gypsum-based boards. This investigation evaluates the behaviour of the cavity, with and without insulation material. The finite volume method is applied to perform the thermal analysis of the wall taking into account the fluid effect in the cavity. The finite element method is applied to perform the thermal analysis of the wall with insulation material in the cavity. The fire resistance is compared for both models (with and without insulation) and a new simple formula is proposed for the temperature evolution in the cavity zone. Some insulant materials can reduce the fire resistance of the wall, when considering the insulation criterion.
- Fire resistance of composite non-load bearing light steel framing wallsPublication . Khetata, Mohamed S.; Piloto, P.A.G.; Ramos Gavilán, Ana BelénThe light steel frame walls are mostly used for non-load bearing applications. The light steel framed walls are made with studs and tracks that require fire protection, normally achieved by single plasterboard, by composite protection layers or by insulation of the cavity. The partition walls are fire rated to resist by integrity and insulation. Seven small-scale specimens were tested to define the fire resistance of non-load bearing light steel frame walls made with different materials. All tests were validated using two-dimensional numerical models, based on the finite-element method, the finite-volume method and hybrid finite-element method. A good agreement was achieved between the numerical and the experimental results from fire tests. The fire resistance increases with the number of studs and also with the thickness of the protection layers. The hybrid finite-element method solution method looks to be the best approximation model to predict fire resistance.
- Fire resistance of non-loadbearing light steel framing walls: numerical validationPublication . Khetata, Mohamed S.; Fernandes, Luiz; Marinho, César; Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Razuk, HenriqueThe light steel frame (LSF) building technology began to replace the more traditional building methods due to its properties such as the non-combustibility, dimensional stability, lightweight and ease of installation. The fire resistance of non-loadbearing walls using LSF is analysed, when considering different materials and configurations, aiming to improve their performance. The analysis is based on two different numerical models, previously validated with experiments. These models allow to compare the predominance of the cavity and insulation material. A set of parametric analysis is presented. The fire resistance is based on a 2D analysis, evaluating the temperature of the unexposed surface. The thickness of the plate is the most important design parameter to increase the fire rating of non-loadbearing LSF walls.
- Fire resistance of non-loadbearing LSF wallsPublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos Gavilán, Ana BelénA set of full scale fitre resistance tests od non-loadbearing wall is presented to evalue to effect os the steel frame (number and position os studs and stracks) and different protection materials.
- Fire resistance of non-loadbearing LSF wallsPublication . Piloto, P.A.G.; Khetata, Mohamed S.; Ramos Gavilán, Ana BelénA set of full scale fire resistance tests of non-loadbearing walls is presented to evaluate the effect of the steel frame (number and position of studs and tracks) and different protection materials. The experimental tests are developed in accordance to the international standards EN1364-1 for the sample preparation and conditions for testing and in accordance with the generic standard fire test EN1363-1, used for the criterion to rate this type of building construction element under fire. Numerical models are also used to compare the results of the tests. The numerical model is validated, using the boundary conditions defined in Eurocode EN1991-1-2 and specific boundary conditions in the cavity of the wall. These specific boundary conditions are essential when assuming that the heat transfer flows by convection and radiation, from the exposed side to the unexposed side of the wall. The results allow to conclude on the behaviour of different systems of protection used for the cold formed steel structure, on the effect of the structure and to present the hybrid model to validate the numerical results.