The air gap effect on the fire resistance of composite slab with steel deck

The fire resistance of composite slabs with steel deck may be defined by experimental tests or using simple calculation methods available in standards, such as EN1994-1-2. The composite slab is made by a concrete topping cast on the top surface of a steel deck, presenting a combination of two different materials (steel and concrete). This work presents the results and the validation of a two dimensional finite element model, used for comparison with experimental results developed by the authors. Results are also compared with the simple calculation method of EN1994-1-2, which seems to be unsafe. The numerical model considers perfect contact between materials, but investigates the effect of the air gap between the concrete slab and the steel deck. The existence of the air gap is usually justified by different expansion coefficients and by the thermal bowing caused by the thermal gradient across the thickness, which leads to the separation of both materials during experimental tests.info:eu-repo/semantics/publishedVersio

Fire resistance of composite slabs with steel deck: from experiments to numerical simulation

This work investigates the thermal insulation behaviour of composite slabs with steel deck under standard fire test conditions. This composite slab consists of a concrete topping cast on the top of a steel deck. The concrete is usually reinforced with a steel mesh on the top and may also be reinforced using individual rebars. The steel deck also acts as reinforcement and may be directly exposed to fire conditions. This composite solution is widely used in every type of buildings which require fire resistance, in accordance to regulations and standards. The fire rating of this type of elements is determined by standard fire tests. Two samples were tested using standard fire conditions ISO834 to evaluate the Integrity (E) and insulation (I). The scope of this investigation concerns the fire rating for insulation (I). Numerical thermal simulation was also developed using Matlab PDE toolbox and ANSYS to compare the results and to find out the thermal effects of standard fire exposure. The results are also compared with the simplified method proposed by Eurocode 4-part 1.2, which seems to be unsafe.info:eu-repo/semantics/publishedVersio

A new calculation method for the temperature of the components of composite slabs under fire

Composite steel-concrete slabs are structural elements composed of a profiled steel deck which acts as a permanent formwork to the concrete topping. This layer is commonly reinforced with individual rebars and an anti-crack mesh. The Annex D of the EN 1994-1-2 provides guidelines for the calculation of the temperature of the steel components of composite slabs subjected to the standard fire. However, no revisions were made to these calculation rules during the last years. This paper proposes a new method for the estimation of the temperature of the parts of the steel deck and the rebars as well. The proposed methodology is derived from numerical analyses using a 3-D finite element model, considering perfect thermal contact between the materials.info:eu-repo/semantics/publishedVersio

A new calculation method for the temperature of the components of composite slabs under fire

Composite steel-concrete slabs are structural elements composed of a profiled steel deck which acts as a permanent formwork to the concrete topping. This layer is commonly reinforced with individual rebars and an anti-crack mesh. The Annex D of the EN 1994-1-2 provides guidelines for the calculation of the temperature of the steel components of composite slabs subjected to the standard fire. However, no revisions were made to these calculation rules during the last years. This paper proposes a new method for the estimation of the temperature of the parts of the steel deck and the rebars as well. The proposed methodology is derived from numerical analyses using a 3-D finite element model, considering perfect thermal contact between the materials.info:eu-repo/semantics/publishedVersio

Numerical simulation of the fire resistance of composite slabs with steel deck

This investigation is related with the fire resistance of composite slabs with steel deck. This composite solution consists of a concrete topping cast on the top of a steel deck. The concrete is typically reinforced with a steel mesh and may also contain individual rebars. The deck also acts as reinforcement and may be exposed to accidental fire conditions from the bottom. This composite solution is widely used in every type of buildings and requires fire resistance, in accordance to regulations. The fire resistance is specified by the loadbearing capacity (R), insulation (I) and integrity (E). The fire rating for (R) and (E) is not in the scope of this investigation. The fire rating for insulation (I) is evaluated by two different methods (numerical simulation and simple calculation). The fire rating is calculated for 32 different geometric configuration, in order to evaluate the effect of the thickness of the concrete layer and the thickness of steel deck. The fire resistance (I) increases with the thickness of the concrete when using both methods, but the simple calculation method seems to be unsafe for all the cases, requiring a revision for the formulae presented in Annex D of EN1994-1-2. A new proposal is presented.info:eu-repo/semantics/publishedVersio

Validation models on the fire resistance of composite slab with steel deck

The composite slab with steel decking is widely used in every type of buildings which require fire resistance, in accordance to regulations and standards. The fire rating of this type of elements is determined by standard fire tests, accounting for Load (R), Integrity (E) and Insulation (I). A literature review from different investigations regarding the fire behaviour of composite slabs with steel deck is presented. A specific number of experimental tests were selected for the validation with three-dimensional finite element models. The fire resistance of composite slabs with steel deck may also be compared with simple calculation methods available in standards, such as EN 1994-1-2. The perfect contact model used for numerical simulation present some discrepancies from the experimental results, which can be eliminated by the use of an air gap between the steel deck and the concrete part of the slab. Other parameters are also investigated regarding the thermal and the mechanical loading systems, towards the best fit approximation for temperature and displacement.info:eu-repo/semantics/publishedVersio

Development and application of computational code for steel frame analysis in fire situation

O presente trabalho teve por objetivo desenvolver um código computacional com base no método dos elementos finitos, para análises termoestruturais de estruturas de aço aporticadas quando expostas a ações térmicas típicas de situações de incêndio. O código utilizado nas análises estruturais emprega elemento finito de pórtico não linear 3-D de formulação posicional. A formulação posicional utiliza como graus de liberdade as posições dos nós ao invés dos deslocamentos, resultando em uma descrição intrinsecamente não linear do comportamento geométrico das estruturas. Podem ser consideradas seções transversais quaisquer com o elemento finito em questão, e sua representação geral é tridimensional. Adota-se uma lei constitutiva tridimensional completa e a cinemática de Reissner, de modo que o modelo de plasticidade considera o efeito combinado das tensões normais e cisalhantes para verificação do critério 3-D de plasticidade. O código computacional desenvolvido permite que sejam realizadas análises térmicas transientes com base no método dos elementos finitos para se determinar campos de temperatura nas seções transversais dos elementos estruturais sujeitos ao fogo. Assim, a influência da temperatura nas propriedades dos materiais é levada em consideração para se avaliar o desempenho da estrutura em cada instante da análise em situação de incêndio, até que o colapso estrutural seja verificado. Análises de casos presentes na literatura são utilizados para validar os resultados obtidos, os quais comprovam a precisão do código computacional desenvolvido e da formulação posicional quando aplicados a análises de estruturas de aço aporticadas à temperatura ambiente e em situação de incêndio.The present work deals with the development of a computational code based on the finite element method for thermo-structural analyses of steel framed structures when exposed to typical thermal actions of fire condition. The structural analysis is performed considering a computer code that uses 3-D frame nonlinear finite elements of positional formulation. This formulation is based on the positions of the finite element nodes, instead of displacements, which results in an intrinsically nonlinear description of the geometric behavior of structures. The cross-sections of finite elements can be of any geometry due to the tridimensional representation. A complete tridimensional constitutive law is used and, therefore, the effect of combined normal and shear stresses is taken into account for the tridimensional plasticity evolution. The developed computational code allows performing transient thermal analyses to determine the temperature field over the cross-sections of the structural elements subjected to fire. The influence of temperature on the material properties is considered to evaluate the structure response at each defined instant of the fire analysis, until the collapse occurs. The achieved results, when compared to those found in the literature, allow verifying the precision of the developed computational code when applied to steel frame analysis at ambient temperature and in fire situation

Balanced summation model for the calculation of the buckling resistance of partially encased columns under fire: new improvements

The fire resistance of partially encased columns (HEB and IPE) depends on the temperature evolution under fire. This paper aims to assess de effect of the balanced summation model into the design of the axial buckling load of partially encased columns under fire, according to EN 1994-1-2. New improvements will be proposed to evaluate the fire resistance, based on new simple formulas to determine the flange temperature, the residual height and temperature of the web, the residual cross section and temperature of concrete, the reduced stiffness and strength of reinforcement. The new proposal is based on the validation of a numerical simulation using ANSYS.info:eu-repo/semantics/publishedVersio

Fire resistance of composite slabs with steel deck: experimental analysis and numerical simulation

This work investigates the thermal behaviour of composite slabs with steel deck under controlled test conditions corresponding to a fire from the bottom. This composite solution consists of a concrete topping cast on the top of a steel deck. The concrete is typically reinforced with a steel mesh and may also contain individual rebars. The deck also acts as reinforcement and may be exposed to accidental fire conditions from the bottom. This composite solution is widely used in every type of buildings and requires fire resistance, in accordance to regulations and standards. Composite slabs need to meet fire-safety requirements according to building codes. The fire assessment of this type of elements is normally made using standard fire tests. Two samples are being prepared to be tested and should take into account the criterion for stability (R), Integrity (E) and insulation (I). The scope of this investigation concerns the fire rating for insulation (I). Numerical simulation was performed through Matlab PDE toolbox for the thermal effects of standard fire exposure. The results are also compared with the simplified method proposed by Eurocode, which seems to be unsafe.info:eu-repo/semantics/publishedVersio

Fire resistance of composite slabs with profiled steel decking: trapezoidal and reentrant numerical simulation

ABSTRACT This work investigates the thermal behaviour of composite slabs with steel deck under fire from the bottom. This composite solution is widely used in every type of buildings and requires fire resistance, in accordance to regulations and standards. The scope of this investigation concerns the fire rating for insulation (I). Numerical simulation was performed through Matlab PDE toolbox for the thermal effects of standard fire exposure. The results are also compared with the simplified method proposed by Eurocode, which seems to be unsafe.info:eu-repo/semantics/publishedVersio