Browsing by Author "Piloto, P.A.G."
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- Accuracy of 2D numerical models towards the prediction of the fire resistance on LSF partition wallsPublication . Piloto, P.A.G.; Gomes, Stephan; Torres, Leonardo; Couto, Carlos; Real, Paulo VilaLightweight steel framing (LSF) walls are commonly used in modern buildings due to their high strength-to -weight ratio and readiness for installation. However, empty cavities within these walls can pose a fire risk if not properly addressed. In order to ensure the fire resistance and performance of LSF walls with empty cavities, various modelling techniques can be employed. Two-dimensional thermal models can also be used to simulate the behaviour of LSF walls with empty cavities in a fire scenario. These models can predict the spread of heat through the empty cavity, allowing designers to identify potential fire hazards and make adjustments to the design to mitigate those risks.Three different computational solution methods were used to compare the fire performance of LSF walls with void cavities. Solution method 1 considers the air-structure interaction in the cavity region. Solution method 2 considers the existence of interface elements for the radiation heat transfer in the cavity region allowing the cavity temperature prediction. Solution method 3 considers the convection and radiation in the cavity region with a prescribed cavity temperature from experiments (hybrid). Solution methods 1 and 3 give a small root mean square error (RMSE), when compared with solution method 2. Solution method 3 gives a better approx-imation because can capture the main fire events during the fire, such as the cracks and fall off. Based on the parametric study, a new proposal is presented to predict the fire resistance by insulation, depending on the gypsum type and thickness.
- Adesão aço-betão em vigas parcialmente embebidas para diferentes condições térmicasPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.As vigas em aço parcialmente embebidas com betão são elementos de estruturas mistos, constituídos por elementos de perfis em aço, reforçados com blocos de betão armado entre os banzos. Esta solução construtiva é responsável pelo aumento da resistência mecânica à temperatura ambiente e em condições de incêndio. Neste trabalho são apresentados resultados experimentais para o valor da tensão de corte de adesão relacionada com os dois processos de ligação (química e atrito) para a temperatura ambiente e temperaturas elevadas Os ensaios experimentais são baseados em testes tipo “push-out”. Os ensaios experimentais são reproduzidos em simulações numéricas, não lineares geométricas e materiais.
- Advanced calculation model calibrated with experimental test of wooden slabs exposed to firePublication . Fonseca, E.M.M.; Piloto, P.A.G.The wooden slabs are structural elements with wide application, in particular, in building rehabilitation, interior spaces and in new building structures. The mechanical, thermal and acoustic properties make this material as an ideal solution for floor and roof slabs applications. However, when exposed to an accidental fire condition it is necessary to assess their vulnerable behaviour accurately. In this work, an advanced calculation model is presented, based on the use of finite elements, calibrated with experimental results. The experimental tests were performed on wooden slabs exposed to a fire from below the element. The slabs were instrumented with thermocouples to measure the temperature at different control points along the fire duration in a fire resistance furnace, following the standard fire curve ISO 834. The advanced calculation model also allows the obtained the transient effect and incorporates the non-linear wood properties. The physical behaviour of the wooden slab is conditioned by the char layer formation, and this phenomenon is also considered in the advanced calculation model.
- Advanced calculation model calibration with experimental test of wooden slabs exposed to firePublication . Fonseca, E.M.M.; Piloto, P.A.G.As lajes em madeira são elementos estruturais com larga aplicação, em particular, na reabilitação de edifícios, espaços interiores e construção de novas estruturas em edifícios. As propriedades mecânicas, térmicas e acústicas fazem deste material uma solução ideal para lajes de pavimentos e coberturas. No entanto, quando expostas a uma ação de acidente tipo fogo é necessário a avaliação do seu comportamento vulnerável com rigor.
- Advanced numerical method for estimate fire resistance of partially encased beamsPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.The ultimate design goal for fire safety engineering is the conception of safe structures. To achieve this goal, advanced calculation methods may be used for the assessment of safety in structures and in particular of structural elements. In order to ensure that ultimate limit requirements are fulfilled, it is necessary to predict failure of each type of material and element during the design process of buildings. This paper deals with the numerical modelling of partially encased beams, which are composed structural elements, widely used in tall buildings, with two or more different materials and types of construction. Normally are used with reinforcement rebars and with or without structural link to slabs that may use concrete to increase fire resistance. Instability problems may occur because concrete may not have the age to resist and also because the concrete may slip over steel, crack or crush. Lateral torsional buckling (TLB) is an instability phenomenon that should be considered. This paper presents Ansys material and geometric non-linear finite element model for determining lateral torsional buckling resistance of partially encased beam with and without encasement reinforcement in fire conditions. The steel part of the composed section will be modelled by finite shell element, concrete part by three-dimensional finite solid elements, the bond slip contact with finite non-linear spring elements and the rebar reinforcement will be considered in perfect contact with concrete, using finite bar element. Elevated temperatures will be applied in both four sides of the cross section along the beam length, based on ISO834 standard fire. Beams will also be subjected to uniform bending corresponding to a specific degree of load bearing capacity. Failure of concrete will be predicted and based on smeared band approach through modification of the stress - strain fields. Fire resistance will be determined for the last time increment in which it is possible to sustain the equilibrium.
- An experimental study of intumescent fire protection coatingsPublication . Mesquita, L.M.R.; Piloto, P.A.G.; Vaz, M.A.P.The use of intumescent coatings plays an important role in the fire protection of structural elements. When submitted to elevated temperatures an intumescent coating undergoes thermochemical reactions that promote a higher thermal protection. To evaluate the behaviour of an intumescent coating, a set of experimental tests made on coated steel plates are performed in a cone calorimeter. These tests are performed with different heat fluxes and intumescent thicknesses. A simple and an advanced model, based in the Finite Difference Method, are presented and applied to determine the intumescent surface temperature evolution, considering the initial thickness and the intumescence variation. The intumescence effective thermal conductivity is estimated by solving the inverse heat transfer problem, considering the temperature in the steel equal to the experimental measured values. When the intumescence thickness variation is taken into account in the numerical model a higher thermal conductivity is expected, when compared with the constant thickness model.
- Análise biomecânica do protocolo – salto com contra movimentoPublication . Piloto, P.A.G.; Barreira, LuísaNeste trabalho é apresentado um estudo experimental de medição da taxa de variação da força propulsiva RFD (“Rate of Force Development”) e o tempo necessário para atingir a fase de início de voo TTT (“Time To Take-off”) de um protocolo de salto com contra movimento (CMJ), utilizando uma população de jovens estudantes do ensino superior, em função do género e da massa de cada individuo. Este protocolo será testado em duas condições de movimento para os membros superiores (com e sem balanço), demonstrando que a altura máxima, a potência máxima propulsiva, a velocidade máxima e a força reativa no solo atingem valores superiores no protocolo CMJ com balanço dos membros superiores.
- Análise biomecânica do protocolo: salto com contra movimentoPublication . Piloto, P.A.G.; Barreira, LuísaNeste trabalho é apresentado um estudo experimental de medição da taxa de variação da força propulsiva RFD (“Rate of Force Development”) e o tempo necessário para atingir a fase de início de voo TTT (“Time To Take-Off”) de um protocolo de salto com contra movimento, utilizando uma população de jovens estudantes do ensino superior, em função do género e da massa de cada individuo. Este protocolo será testado em duas condições de movimento para os membros superiores (com e sem balanço).
- Análise da resistência à fractura de próteses parciais fixas pelo método dos elementos finitosPublication . Piloto, P.A.G.; Correia, André; Campos, J.C. Reis; Vaz, M.A.P.; Fernandes, J.C. SampaioAs próteses parcialmente fixas (PPF), revestidas com material cerâmico, são normalmente utilizadas para reabilitar as características estéticas e funcionais. Um dos problemas clínicos que pode surgir com a utilização deste material está relacionado com as propriedades físicas, em particular com a sua natureza frágil. Este trabalho pretende simular as condições de iniciação da fissuração, por incremento de carga aplicada num modelo simplificado de uma PPF, prevendo e avaliando o seu comportamento antes da sua construção. Este modelo numérico utiliza dois materiais, com comportamento não linear, com previsão da fissuração distribuída.
- Análise da temperatura nos ensaios de resistência ao fogo de vigas parcialmente embebidas com betãoPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Este trabalho pretende analisar a distribuição de temperatura em doze ensaios de resistência ao fogo. realizados em elementos de viga parcialmente embebidos com betão, agrupados em 4 séries, ver tabela I. Os elementos de viga foram construídos com perfis em aço IPE I 00 e betão reforçado entre as almas do perfil.