A refrigerated truck chamber is always under variable conditions. Not only weather changes but also loading and unloading processes can make the chamber behaviour dependent on time. A prediction of relevant properties distributions (velocity, temperature and relative humidity) in refrigerated chambers requires the simultaneous solution, by an iteration process, of the three-dimensional non-linear differential equations for the momentum and heat/mass transport. Basically, these two transport phenomena are coupled by the buoyancy force due to natural convection. However, especially for non-steady state thermal conditions, the high computations times become unattractive the simultaneous integration. For the majority of refrigerated truck chambers, in which the air flow is mainly dominated by forced convection, the equations can be decoupled and the two transport phenomena can be treated separately. Therefore, in the case of dynamic (transient) simulation, this strategy makes the problem much simpler and can strongly reduce the computation time. In this study the simulation method described here was applied in a case study modelling (steady and transient) and was validated by measurements taken from an experimental reduced-scale model.

Developments on code-compliant Topology Optimisation methodologies for the steel construction industry have recently been proposed. Also, it has been found that topologically optimised steel bolted connection parts – which behave non-linearly to a very significant degree of damage – do not waive physically non-linear analyses to assess an ultimate capacity that can be lower than what is predicted by the optimisation procedure linear analyses. These two circumstances brought urgency to the experimental testing of such optimised parts. The herein depicted experimental programme assessed topologically optimised and previously numerically analysed bolted parts of a well-known steel connection. The results allowed redefining the material trilinear model to be used in further numerical analysis and, very significantly, validated the numerical simulations results as well as the application of Eurocode formulae for connections component resistance. The difference between the previous numerically predicted ultimate resistance and the experimentally defined did not exceed 2.6%.

Climate change represents an escalating global crisis, with environmental, social, and economic consequences that are reshaping societies worldwide. The transportation sector bears a substantial share of responsibility for global greenhouse gas emissions. In this context, advancements in engine design and the development of advanced control systems have contributed to improved performance and efficiency. Despite significant progress in the electrification of transport, internal combustion engine (ICE) development continues to receive considerable investment due to its broad applicability and existing infrastructure. A key challenge in ICEs, particularly reciprocating engines, is the mitigation of torque irregularities caused by the intermittent nature of the combustion process. Addressing this issue through mechanical actuators presents a technically demanding yet promising solution, with potential to overcome limitations of alternative technologies and unlock new engineering developments. This research analyses instantaneous torque irregularities in reciprocating ICEs during their operating cycles and the associated speed fluctuations. It identifies the underlying causes and evaluates their impact on overall engine torque and rotational speed. Based on this analysis, a mechanical actuator composed of a plate cam and a compression spring is designed and optimised. The actuator stores and releases mechanical energy to generate a counteracting torque equal in magnitude and opposite in direction to the engine’s output. This counter-phase torque minimizes torque fluctuations and significantly reduces speed variations, improving engine performance without increasing drivetrain inertia. The study proposes a purely mechanical solution to attenuate torque variations, contributing to more efficient and environmentally sustainable engines. Practical validation of the actuator will confirm its applicability and performance impact.

The purpose of most buildings is to provide a comfortable and healthy indoor environment for the occupants. As a result of increasing energy prices in the last decades, much effort has been done to reduce the cost arising from mechanical and natural ventilation of buildings. This often involves lowering the outdoor air intake. At the same time, many new pollution sources have been introduced in the buildings. These issues are important if we take into consideration that today the majority of the people spends more than 90% of their time indoors. In this work will be presented a physical and mathematical models to study the three-dimensional turbulent air flow patterns with thermal buoyant effects, the heat transfer, including radiation between walls, the gas contaminant trasnport and the most air transport into mechanical or natural ventilated spaces. the calculations made use of a numerical procedure, which solves the three-dimensional equations for the conservation of mass, momentum, thermal energy and air contaminant transport. The turbulence is modelled by the k-e model and thermal radiation by the discrete transfer method. To validate the mathematical model, the predictions results were compared with experimental data for two different scales - full scale office room and 1/4 laboratory scale model. A physical modelling technique, based on dimensional analysis, was used to derive the physical properties of the laboratory model, designed to provide similarity with the room. The simulation of the air contaminant distribution, the thermal and the air flow patterns in an office natural ventilated room (prototype and model) was performed.

O método das componentes, ao permitir avaliar o comportamento de uma gama alargada de configurações de junta, estabeleceu-se como o método de referência para o dimensionamento de juntas metálicas, sendo por isso codificado no Eurocódigo 3 – Projeto de estruturas de aço, Parte 1-8: Projeto de ligações. Ainda assim, este método apenas foi calibrado para juntas de dimensões usuais.Os modelos 3D de elementos finitos atualmente são uma ferramenta com imenso potencial pois permitem considerar fenómenos complexos relacionados com não linearidades materiais e geométricas, mas cuja utilização ainda não é uma realidade.Nesta tese é levado a cabo a avaliação do comportamento de duas juntas metálicas de grandes dimensões. Esta avaliação é feita recorrendo ao método das componentes e ao método dos elementos finitos cujos resultados são confrontados com resultados de ensaios experimentais realizados.Este trabalho permitiu concluir que o método das componentes conduz a estimativas conservadores para a resistência e para a rigidez das juntas e que o método dos elementos finitos pode conduzir a boas estimativas para o comportamento das juntas, mas, para isso, as condições de fronteira dos provetes de ensaio devem ser perfeitamente definidas.Este trabalho permitiu ainda concluir que o método dos elementos finitos é uma ferramenta com muitas potencialidades que permite uma caracterização muito rigorosa do comportamento efetivo das juntas. No entanto, a sua utilização para o efeito de projeto tem custos proibitivos na medida em que exige muito tempo para criar e correr os modelos, mas também know-how para definir não só os modelos materiais bem como as malhas.Conclui-se desta forma que o método das componentes é perfeitamente aplicável a ligações de grandes dimensões e é o método com melhor relação custo/benefício para utilização em ambiente de projeto.

The promotion of a more resource efficient and greener economy and the reduction of energy consumption are among the priorities defined in the Europe 2020 Strategy. The implementation of effective measures for reducing energy consumption in new construction and retrofitting existing buildings have therefore been set as priorities. The use of thermal insulation materials is the most efficient way of reducing heat loss in buildings, thus reducing heat energy needs. The potential of incorporating different types of waste and by-products, such as those produced in the cork processing industry, in construction materials and solutions is relevant for achieving a more sustainable construction and use of buildings throughout their life cycle. Expanded cork agglomerate (ICB) has been used on an ad hoc basis as an alternative to external thermal insulating composite systems but without a detailed technical characterisation. This work aims to contribute to the characterisation and development of this system by incorporating ICB boards, both when they are used in new building construction and for retrofitting projects. First, existing ICB coated buildings were visited to assess the main anomalies, its probable causes, and eventual solutions. A set of detailed application methods have been proposed. Constructive rules and construction details are presented. Maintenance actions to preserve the properties of the system are proposed. Then, a wide range of laboratory tests were performed to evaluate the mechanical, hygrothermal and durability characteristics of both standard (90-110 kg/m3) and medium (140-160 kg/m3) density ICB. It was found that the medium density ICB has a better mechanical performance, without compromising its hygrothermal behaviour, and therefore more suitable to be used as external insulation. It was proven that it is also resistant to long-term exposure to external aggression. The importance of varying moisture content on the thermal behaviour of a wall covered with medium density ICB, when exposed to rain, was evaluated. A simple analytical model that simulates the heat transfer phenomenon was used to quantify its importance by comparing the mathematical results with those obtained experimentally. Steady and unsteady state conditions for both summer and winter conditions were considered. The results show that the thermal behaviour of the wall is only affected during the rainy period, until the first few hours when the ICB starts to dry and is confined to the upper layers of ICB. The influence of the solar heat flux, temperature, and relative humidity on OSB and concrete walls covered with medium density ICB, with different thicknesses, was evaluated. A boundary element numerical model was used to simulate the coupled heat and moisture transfer through the walls. Initially, the effect of the abrupt variation of relative humidity and temperature were simulated, allowing to conclude that the relative humidity variation is only significant when, during the course of the year, there are relevant weather changes. Thus, summer and winter real weather data of both Bragança (Portugal) and Seville (Spain) were used to simulate the walls’ hygrothermal behaviour. The obtained results show that the short-term environment moisture variation has an impact limited to the outer surface layers and that the moisture along the wall is only high when the external moisture is high and remains high for an extended period. Finally, wind resistance, water-tightness and resistance to impacts of the proposed constructive solutions were experimentally evaluated.

Linear and point thermal bridges (LTBs and PTBs) increase the heat loss of a building envelope in winter conditions due to a concentration of heat fluxes, which depends on the properties of the material(s) and the geometrical characteristics of the thermal bridge. Furthermore, in these two-dimensional (2D) and three-dimensional (3D) junctions, the surface temperatures are normally significantly lower, which increases the risk of surface condensation and the occurrence of building pathologies. Therefore, it is of the utmost importance to evaluate LTBs and PTBs at the design stage of the building and assess their contribution to the energy performance of buildings. The steady-state analysis of the energy performance of buildings normally takes into account the LTBs, but the PTBs’ contribution tends to be neglected. Whole building dynamic simulation studies, however, usually only assume the one-dimensional (1D) heat transfer through the building envelope and fail to consider the multidimensional heat flows through the linear and point thermal bridges. However, it is very important to predict the thermal behaviour of LTBs and PTBs dynamically, since the influence of the thermal inertia of materials can be considered and high performance solutions can be chosen to reduce the thermal bridging effect. This will prevent the development of pathologies associated with thermal bridges and increase the overall energy performance of the building. Most studies on dynamic thermal bridging analysis use simplified techniques that do not give accurate information about the dynamic behaviour of linear and point thermal bridges. Therefore, more realistic models are required that can provide more accurate results and a better knowledge of the dynamic thermal bridges’ behaviour. The main goal set for this research was to analyse the dynamic effect of geometrical linear and point thermal bridges of buildings, such as 2D and 3D building corners, using the boundary element method (BEM) formulated in the frequency domain. For this, multidimensional numerical modelling tools were specially built to study the transient heat diffusion through LTBs and PTBs, using 2D and 3D BEM formulations. These tools enabled the computation of the temperature distribution and heat fluxes through the linear and point thermal bridges, over time. The numerical models were first verified against analytical schemes, known for regular geometries, and then were experimental validated using hot box measurements, simulating the dynamic thermal behaviour of a 2D and a 3D corner of a wooden building. Several numerical simulations of the transient heat transfer through 2D and 3D building corners were performed to illustrate the applicability of the proposed BEM models and to evaluate the thermal bridging effect over time. The influence of the constructive solutions and the external temperature variation on the dynamic thermal behaviour of LTB and PTB was also analysed. The importance of modelling linear and point thermal bridges dynamically was demonstrated. It was concluded that a static analysis underestimates the linear thermal transmittances and overestimates the wall’s surface temperature in the vicinity of the LTB. Moreover, the additional heat flow through the PTBs analysed was found to be significantly lower than the heat flow through the adjacent building elements and through the LTB junctions. However, the evaluation of the dynamic point thermal bridging effect in building envelope details can be very important when it comes to overcoming moisture condensation problems, since lower surface temperatures are registered in the vicinity of the PTBs under dynamic conditions. The dynamic behaviour of the linear and point thermal bridges clearly depends on the thermal properties of the materials and the position of the insulation layer.

When a beam is bent about its axis of greatest flexural rigidity it may twist before it reaches its strength limit state. This flexural stability limit state is most commonly referred to as lateral torsional buckling of a beam. The twisting of the beam occurs when the compression flange becomes unstable as a result of its being subjected to flexural induced axial stresses. Lateral torsional buckling is of importance when the compression flange is laterally unsupported as is often the case in continuous beams, cantilever beams, frame beams and frame columns. The aim of this work is to develop a simple model, i. e., an analytical method to be used by designers for the calculation of the resistance moment of steel I-beams failing by lateral torsional buckling when submitted to the fire. A particular attention has been paid to the possibility to use the same model as the one proposed in Eurocode 3 – Part 1-1, simply modifying material properties according to the temperature. This is the procedure currently proposed in Eurocode 3 – Part 1-2, although its accuracy has never been demonstrated and can indeed be questioned. Due to the fact that higher temperatures usually develop at the end of the flanges than in the rest of the section, the decrease of the bending stiffness in case of fire is faster around the weak axis than around the strong axis of the section. The method has been developed from a set of experimental results performed at elevated temperatures. As it is known any analytical, numerical or theoretical model is much more likely to be accepted if it is backed and supported by a set of experimental tests. Comparison of the simple model has been made with laboratory test results obtained in the framework of this work. A set of experimental full-scale tests were performed on IPE100 profiles at elevated temperature for several length specimens from 0.5 meter to 6.5 meters of buckling length. Residual stresses, geometrical imperfections and material strength were measured for each tested element. The load was applied after the heating of the beams. The beams were electric heated by means of ceramic mat elements. Automatic control on different heating devices was presented in order to ensure a uniform temperature distribution along the length of the elements. The temperature field has been measured with thermocouples welded on the beams. A Set of experimental results are presented, relating the critical load with the mid span movement of the beam cross section, when submitted to a constant moment distribution and to a uniform distributed load, due to the ceramic mat and the insulation material weight.

O consumo elevado no setor dos edifícios face às exigências regulamentares de conforto térmico e à necessidade de racionalizar o uso de energia atribui à reabilitação energética de edifícios um destaque importante na sociedade atual. Nesta dissertação foi desenvolvido um estudo do reforço do desempenho energético de uma moradia unifamiliar a reabilitar, tomando como Caso de Estudo um edifício do concelho de Viana do Castelo. Para tal, avaliou-se o cenário existente com recurso à simulação numérica e à experimentação. O estudo teve como objetivos: caracterizar o desempenho térmico da moradia em estudo recorrendo a um programa de simulação numérica em regime dinâmico, validar o respetivo modelo com resultados de experimentação efetuada a três zonas específicas da moradia, avaliar o desempenho energético através da simulação numérica em regime permanente, propor melhorias do desempenho térmico-energético e determinar as soluções de reabilitação (passivas e ativas) mais adequadas. A análise do Caso de Estudo permitiu avaliar o desempenho das zonas térmicas da moradia e revelou que as temperaturas atingidas ao longo de um ano apresentavam valores que se encontravam fora do intervalo de temperaturas de conforto desejáveis. A caracterização experimental permitiu comparar os valores de temperatura do ar interior obtidos pelo programa EnergyPlus e por via de medições in situ realizadas ao sótão, ao quarto orientado a sul e ao quarto orientado a norte, concluindo que o sótão é o compartimento que apresenta maiores necessidades de reabilitação. A análise de soluções de reabilitação passiva permitiu afirmar que a aplicação em conjunto de soluções é mais vantajosa do que a aplicação individual para os compartimentos em questão. Através da análise de soluções de reabilitação ativa determinou-se que o recuperador de calor foi a solução com maior destaque. O estudo do modelo de simulação numérica em regime permanente permitiu avaliar a eficiência energética da moradia e das soluções de reabilitação. A classe energética atingida na moradia foi C. Com a aplicação em conjunto das soluções passivas obteria uma classe B. Com a introdução do recuperador de calor, como solução de reabilitação ativa, a moradia alcançaria uma classe energética A+.