Analytical and numerical methodologies to study four different hot-rolled steel profiles under fire

The main goal of this paper is to calculate the temperature distribution in four different hot-rolled steel profiles (IPE, HEM, L and UAP), during a thermal and transient process due an accidental fire situation. This work presents the lumped capacitance method, according to the section factors effect, and compares all results with the finite element method, using Ansys® numerical program. The basis of the lumped capacitance method is that temperature of the solid body is uniform at any given time instant during heat transient process. This methodology is compared with the numerical results and allows the calculation of the temperature evolution in steel profiles under fire, like an easy way to follow. The results comparison allows to verify an agreement between the used methodologies. This find enabled to conclude that the lumped capacitance method is accurate and could be easily applied. This method allows to calculate a constant temperature distribution for any profile, at any time instant. It was also intended to understand the relationship between the increase in the cross-section and the temperature difference in the profiles. In the studied profiles ranges with the larger cross-section, a lower temperature field was obtained. As conclusion, members with low section factors will heat up more slowly.info:eu-repo/semantics/publishedVersio

Modelação numérica do comportamento ao fogo de uma estrutura em aço inoxidável em situação de incêndio

O aço inoxidável tem reconhecidamente uma resistência ao fogo superior ao aço carbono pelo que é de prever uma crescente utilização deste tipo de aço para fins estruturais. De facto, embora mais caro que o aço carbono, o aço inoxidável pode conduzir a estruturas competitivas em virtude de necessitarem de uma menor quantidade de material de protecção térmica ou mesmo, em alguns casos, não ser necessária protecção contra incêndio, como sucede na estrutura apresentada neste artigo. Com o objectivo de modelar pelo Método dos Elementos Finitos o comportamento de uma estrutura porticada de um edifício em aço inoxidável em situação de incêndio, introduziu-se a sua lei constitutiva no programa SAFIR, um programa de elementos finitos para análise não-linear geométrica e material, especialmente desenvolvido na Universidade de Liège para estudo de estruturas sujeitas à acção do fogo. Neste programa as propriedades térmicas e mecânicas do aço são função da temperatura, de acordo com o Eurocódigo 3. Compara-se o comportamento da estrutura em aço inoxidável 1.4301 (também conhecido como 304) com o comportamento que teria se a estrutura fosse em aço carbono S235 e realçam-se os benefícios da utilização do aço inoxidável resultantes da sua maior resistência ao fogo

Analytical equations applied to the study of steel profiles under fire according to different nominal temperature-time curves

Some analytical methods are available for temperature evaluation in solid bodies. These methods can be used due to their simplicity and good results. The main goal of this work is to present the temperature calculation in different cross‐sections of structural hot‐rolled steel profiles (IPE, HEM, L, and UAP) using the lumped capacitance method and the simplified equation from Eurocode 3. The basis of the lumped capacitance method is that the temperature of the solid body is uniform at any given time instant during a heat transient process. The profiles were studied, subjected to the fire action according to the nominal temperature–time curves (standard temperature‐time curve ISO 834, external fire curve, and hydrocarbon fire curve). The obtained results allow verifying the agreement between the two methodologies and the influence in the temperature field due to the use of different nominal fire curves. This finding enables us to conclude that the lumped capacitance method is accurate and could be easily applied.info:eu-repo/semantics/publishedVersio

Numerical modelling of the behaviour of a stainless steel portal frame subjected to fire

It is known that stainless steel has a better fire performance than carbon steel, which can lead to a growing utilization of this kind of steel in structures. In fact, although more expensive than the carbon steel, structures in stainless steel can be competitive because of its smaller thermal protection need. With the purpose of modelling by Finite Element Method the behaviour of a stainless steel framed structure, without any protection, submitted to fire, has been introduced in the SAFIR program, the material properties of the stainless steel. SAFIR is a finite element program with geometrical and material non-linear analysis, specially developed in the University of Liège for studying structures subjected to fire. The thermal and mechanical properties of the stainless steel, introduced in the SAFIR program are temperature dependent, according to the Eurocode 3. The stress strain relationship, the thermal conductivity and the specific heat are the most important material properties for the structure analysis at high temperatures. These properties in stainless steel are considerable different from carbon steel. The behaviour of the structure will be compared in the two different materials: stainless steel 1.4301 (also known as 304) and carbon steel S235. The benefits of using stainless steel in the fire resistance of the structure, which is 3 times higher than the one obtained with carbon steel, avoiding any fire protection material needed to fulfil the necessary fire requirements will be shown

Modelação numérica da encurvadura lateral de vigas em aço inoxidável sujeitas a temperaturas elevadas

A utilização de elementos estruturais em aço inoxidável tem vindo a crescer nos últimos anos, devido quer à sua maior resistência à corrosão quer à sua maior resistência mecânica ao fogo, quando comparado com o aço carbono. Com o objectivo de modelar pelo Método dos Elementos Finitos a encurvadura lateral de vigas I em aço inoxidável sujeitas a altas temperaturas, introduziram-se as leis constitutivas de diferentes tipos de aço inoxidável no programa SAFIR. Trata-se de um programa de elementos finitos para análise não-linear geométrica e material, especialmente desenvolvido na Universidade de Liège para o estudo de estruturas sujeitas à acção do fogo. Neste trabalho pretende-se efectuar uma breve comparação das propriedades mecânicas do aço carbono com as do aço inoxidável a altas temperaturas e os resultados numéricos obtidos com esta nova versão do programa SAFIR, adaptado para tratar o aço inoxidável, com resultados obtidos com o programa comercial ANSYS, utilizando elementos finitos de viga e de casca

Modelação numérica de elementos estruturais em aço inoxidável com secções esbeltas em situação de incêndio

Neste trabalho, a resposta estrutural de elementos esbeltos em aço inoxidável submetidos a incêndio é analisada numericamente através de programas de elementos finitos geométrica e materialmente não lineares. Com o intuito de realizar estas simulações, foram necessárias duas alterações no programa SAFIR: i) foi introduzida a lei constitutiva 2D do aço inoxidável, para ser usada em elementos de casca e ii) foi introduzida a possibilidade do programa considerar tensões residuais em elementos finitos de casca. A lei constitutiva utilizada do aço inoxidável foi a apresentada na parte 1.2 do Eurocódigo 3. Para modelar o endurecimento exibido pelos aços inoxidáveis, usando a formulação de elementos de casca, foi necessária uma aproximação à referida lei constitutiva do Eurocódigo 3. Imperfeições geométricas locais e globais foram consideradas nas simulações numéricas. Por fim, este trabalho mostrará também a influência das tensões residuais na capacidade resistente em situação de incêndio, de elementos estruturais esbeltos em aço inoxidável

Rail temperatures models validated with experimental measurements

Rail temperature plays an important role when understanding and predicting thermal buckling. An energy balance model called CNU was used to simulate rail temperatures, validated with FEA analysis, and compared with experimental measurements. The model uses weather data and accounts for the solar position and shadow effect to improve temperature prediction. Furthermore, a python package is developed to solve the thermal lumped model including specific modifications on the model. The results from the simplified model and Finite Element Analysis (FEA) model are in good agreement. Compared with the collected data, the model reaches the value R² of 0.914.info:eu-repo/semantics/publishedVersio

Prediction models for rail temperatures validated with experimental measurements

Rail temperatures play an important role when understanding and predicting rail track instabilities. A rail temperature energy balance model was used, validated with FEA analysis, and compared with field-collected data. Both solution methods are in good agreement. Compared with the collected data, the model reaches an R² of 0.83. Boundary conditions improvements may be required.info:eu-repo/semantics/publishedVersio

Computational model to predict the temperature distribution produced by bone cement

Bone is the third frequent location for haematogenous dissemination of malignant tumors. Patients with multiple bone metastases are exponentially growing. Bone metastases, which are frequently diagnosed late, are associated to imminent and pathological bone fractures. Metastatic disease translates an advanced tumor stage and it has a high impact in patients’ quality of life and survival. The main objective is to study the thermal effect induced by the bone cement polymerization, in the bone metastatic tumor reduction and to understand the role of such procedure and its biomechanical stabilization. To assess the clinical effect, it is important to test this methodology before its application and obtain sustained results. In this work, a computational model was developed to predict the temperature distribution produced by cement polymerization, and verify the reduction of the metastatic tumor area due the thermal effect. Different simulations produced to evaluate the necrosis effect for two cement amount sizes introduced in a cortical and spongy bone tumor. The same computational models were reproduced introducing an endomedular nail in titanium and a femoral stem in cobalt-chrome material in pathological bone fractures.info:eu-repo/semantics/publishedVersio

Thermal computational model to predict thermal necrosis in bone sarcomas

Sarcomas are heterogeneous tumors that form frombonetissue, connective tissue, cartilaginous tissue,muscle tissue, adipose tissue, peripheral nerves, and blood vessels,usually atits extremities. These tumors occur at any age and in any region of the patient's body.info:eu-repo/semantics/publishedVersio