Browsing by Author "Almeida, David"
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- Axial buckling load of partially encased columns under fire – new formulaePublication . Piloto, P.A.G.; Mesquita, L.M.R.; Ramos Gavilán, Ana Belén; Almeida, DavidFire resistance of partially encased columns (HEB and IPE) depends on the temperature evolution during fire exposure. 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 formulae 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. ANSYS was used to validate new and safe formulae, based on the analysis of the cross section totally engulfed in fire.
- Balanced summation model for the calculation of the fire resistance of partially encased steel sections: new proposalsPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEB) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation of the bending resistance was already conducted in fire and under elevated temperature (Paulo A. G. Piloto el al., 2013a) (Paulo A. G. Piloto el al., 2013b). The three-dimensional finite element solution, with precise detail of each component (steel profile, reinforcement, stirrups and concrete) was used to determine the bending resistance under three point bending configuration. Four temperature levels were tested (20, 200, 400 and 600 ºC) and three lengths were considered (2.5, 4.0 and 5.5 m), using three different cross section types, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. Two distinct types of welded stirrups were simulated (PEBA with “C” shape stirrups welded to the web and PEBB with “I” shape stirrups welded to the flange). The numerical solution method is incremental and iterative (arc length method), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. Results are in accordance to the new formula presented to steel beams (P. M. M Vila Real et al., 2004) and adapted to Partially Encased Beams. The bending resistance was not significantly influenced by any type of tested welded stirrup.
- Balanced summation model for the calculation of the fire resistance of partially encased steel sections: new proposalsPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEB) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation of the bending resistance was already conducted in fire and under elevated temperature (Paulo A. G. Piloto el al., 2013a) (Paulo A. G. Piloto el al., 2013b). The three-dimensional finite element solution, with precise detail of each component (steel profile, reinforcement, stirrups and concrete) was used to determine the bending resistance under three point bending configuration. Four temperature levels were tested (20, 200, 400 and 600 ºC) and three lengths were considered (2.5, 4.0 and 5.5 m), using three different cross section types, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. Two distinct types of welded stirrups were simulated (PEBA with “C” shape stirrups welded to the web and PEBB with “I” shape stirrups welded to the flange). The numerical solution method is incremental and iterative (arc length method), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. Results are in accordance to the new formula presented to steel beams (P. M. M Vila Real et al., 2004) and adapted to Partially Encased Beams. The bending resistance was not significantly influenced by any type of tested welded stirrup.
- Bending resistance of partially encased beams at elevated temperature: advanced calculation modelPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEBs) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation of the bending resistance was already verified in fire and under elevated temperature (Paulo A. G. Piloto el al., 2013a) (Paulo A. G. Piloto el al., 2013b). The three-dimensional finite element solution, with precise detail of each component (steel profile, reinforcement, stirrups and concrete) was used to determine the bending resistance under three point bending configuration. Four temperature levels were tested (20, 200, 400 and 600 degrees C) and three lengths were considered (2.5, 4.0 and 5.5 m), using three different cross section types, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. Two distinct types of welded stirrups were simulated (PEBA with "C" shape stirrups welded to the web and PEBB with "I" shape stirrups welded to the flange). The solution method is incremental and iterative (arc length), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. Results are in accordance to the new formula presented (P. M. M Vila Real et al., 2004) and adapted to partially encased beams. The bending resistance was not significantly influenced by the type of welded stirrup
- Bending resistance of partially encased beams at high temperatures: three dimensional numerical simulationPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEB) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation was already developed under fire and under elevated temperatures by Paulo Piloto et al. The bending resistance of partially encased beams submitted to three bending point loading condition, at four temperature levels (20, 200, 400 and 600 ºC) is determined, based on the three dimensional finite element model (steel profile, reinforcement, stirrups and concrete). An incremental and iterative (arc length) solution method is defined to solve a geometric and material non-linear analysis (ANSYS), using a reduced integration method. The model considers perfect contact between steel and concrete. The material model assumes plasticity. The initial imperfection mode is based on the elastic stability solution (ANSYS). Two types of stirrups were considered: welded to the web (PEBA) and welded to the flanges (PEBB), three different lengths (2.5, 4.0 and 5.5 m) and three types of cross section dimensions were simulated, based on the dimensions of different classes of steel profiles (IPE100, IPE200 and IPE300). A total of 72 models were simulated, showing conservative results with respect to the simple calculation method of EN1994-1-2. The bending resistance of the numerical results was determined for multiple force events, The proportional limit force (Fp) with respect to the vertical displacement, the force (Fy) resulting from the intersection method between two straight lines drawn from linear and non-linear interaction of the vertical displacement; the load event for the vertical displacement limit of L/30 (FL/30); and the maximum load level for the asymptotic behaviour of lateral displacement (Fu). Results are in accordance to the new formula presented by Vila Real et al. and adapted to composite section.
- Partially encased section: strength and stiffness under fire conditionsPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Fire resistance of partially encased sections (HEB and IPE) depends on the temperature evolution during fire exposure. Eurocode 4, part 1.2 [1], proposes the assessment of the cross section using the method of the four components under fire (flanges, web, concrete and reinforcement). This study aims to assess the balanced summation model of Eurocode (informative annex G) with respect to the plastic resistance to axial compression and the effective flexural stiffness of the cross section with respect to the weak axis. New formulae will be proposed to evaluate fire resistance, based on new simple formulas to determine the flange average temperature, the residual height and average temperature of the web, the residual cross section and average temperature of concrete, the reduced stiffness and strength of reinforcement. The advance calculation method was used to validate new and safe formulae, based on the analysis of the cross section totally engulfed in fire.
- Partially encased section: strength and stiffness under fire conditionsPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Fire resistance of partially encased sections (HEB and IPE) depends on the temperature evolution during fire exposure. Eurocode 4, part 1.2 [1], proposes the assessment of the cross section using the method of the four components under fire (flanges, web, concrete and reinforcement). This study aims to assess the balanced summation model of Eurocode (informative annex G) with respect to the plastic resistance to axial compression and the effective flexural stiffness of the cross section with respect to the weak axis. New formulae will be proposed to evaluate fire resistance, based on new simple formulas to determine the flange average temperature, the residual height and average temperature of the web, the residual cross section and average temperature of concrete, the reduced stiffness and strength of reinforcement. The advance calculation method was used to validate new and safe formulae, based on the analysis of the cross section totally engulfed in fire.
- Redução das características das secções parcialmente embebidas com betão sujeitas à ação do fogoPublication . Almeida, David; Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.A Resistência ao fogo de secções parcialmente embebidas em betão depende da evolução da temperatura durante o tempo de exposição. O Eurocódigo 4, parte 1.2 [1], propõe a análise da secção transversal, utilizando o método das quatro componentes (banzos, alma, reforço e betão) para determinar a temperatura média das componentes e a redução da geometria efetiva, para vários classes de resistência ao fogo (R30, R60, R90 e R120). Este trabalho tem como objetivo avaliar os coeficientes empíricos e as expressões apresentadas no anexo informativo G para determinação da: temperatura do banzo; redução da altura efetiva da alma; secção resistente do betão e temperatura média; redução das características de rigidez e resistência do reforço. Será utilizado um método avançado de cálculo (elementos finitos não-linear material em regime transiente) para avaliar o efeito da temperatura em todos estes parâmetros.
- Resistência ao fogo de elementos parcialmente embebidos com betãoPublication . Almeida, David; Piloto, P.A.G.Esta tese tem como objetivo ampliar o conhecimento sobre o comportamento de elementos parcialmente embebidas em betão a temperaturas elevadas. A resistência ao fogo de secções HEB e IPE parcialmente embebidas em betão depende da evolução da temperatura durante o processo de aquecimento. O Eurocódigo 4, parte 1.2 [1], propõe a análise da secção transversal utilizando o método das quatro componentes (banzos, alma, aço de reforço e betão) para obter a temperatura média e a redução de geometria após a resistência ao fogo padrão (R30, R60, R90, R120). O estudo pretende validar: o coeficiente empírico apresentado na tabela G.1 anexo G da EN 1994-1-2 [1]; a área residual de betão; a temperatura média no betão e o parâmetro de redução da altura da alma. Será utilizado um método de cálculo térmico avançado (não linear) para obter e validar uma nova proposta de cálculo. Pretende-se ainda determinar a resistência a encurvadura lateral de vigas parcialmente embebidas constituídas por perfis IPE100; IPE200 e IPE300. As vigas serão compostas por estribos soldados à alma ou soldados aos banzos, denominadas PEBA e PEBB respetivamente. Cada seção será avaliada com vãos entre apoios de 2.4, 3.9 e 5.4 metros. As vigas em estudo serão ainda simuladas a temperaturas de 20, 200, 400 e 600ºC. A simulação será incremental e iterativa, utilizando o programa ANSYS.
- Three dimensional simulation of partially encased beams at elevated temperaturesPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEBs) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation was already verified under fire and under elevated temperatures [1-2]. The bending resistance for three bending point configuration, at four temperature levels (20, 200, 400 and 600 ºC) is determined, based on the three dimensional finite element model, with precise detail of each component (steel profile, reinforcement, stirrups and concrete). The solution method is incremental and iterative (arc length), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. The model considers perfect contact between steel and concrete. The material model assumes plasticity. The imperfection mode was based on the elastic stability solution, also performed with finite element method (ANSYS). Two types of stirrups were considered: welded to the web (PEBA) and welded to the flanges (PEBB), three different lengths (2.5, 4.0 and 5.5 m) and three types of cross section dimensions were simulated, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. A total of 72 models were simulated, showing conservative results with respect to the simple calculation method of EN1994-1-2. The bending resistance of the numerical results was determined for different force events, giving the opportunity to compare the ultimate bending moment. Results are in accordance to the new formula presented by Vila Real et al. [3] and adapted to composite beams.