The thesis deals with the issue of replacement of the Rotax 912 ULS engine with the Rotax 915 iSc3 B engine and its impact on flight performance, characteristics and airframe loads of the WT 9 Dynamic. For accomplish better maneuverability tail surfaces are enlarged. Both versions of airplane with different engines and tails surfaces are quantified with respect to airframe loads and flight characteristics. The output of the diploma thesis can be used for strength design of airplane structure and stress tests of the new modification of the WT 9 Dynamic aircraft.

The study is a comparative desk study of the application of the vertical earth load, traffic live load and the nominal earth pressure in the design methodology of culverts as outlined in TMH7 – Code of Practice for the design of highways bridges and culverts in South Africa Part 2, AASHTO LRFD Bridge Design specification and the DMRB volume 2 section 2 part 12 - BD31/01. It involves the theoretical design and analysis of five single cell reinforced concrete box culverts ranging from 2.1m to 6.0m under different fill depths ranging from 0 to 8.0m by applying load obtained using the three design manuals. The objective of this study is to analyze the methodology involved in estimating vertical earth load on a culvert as outlined in the design manuals to ascertain relevance of the formulae and procedure in TMH7 or/and to recommend the most effective approach for evaluating the vertical earth load on box culverts specific and appropriate for South Africa. By comparing the load derivation methodology outlined in ASHTO LRFD and BD 31/01 and analyzing the load forces obtained from the analysis. Box culverts are designed as rigid monolithic structures to withstand the maximum bending moment and shear force. The design involves the analysis of the various loads acting on the culvert with the weight of the overhead earth embankment being the most significant. The vertical earth load, live load and the lateral earth pressure acting on the culverts at various fill depth are manually derived from equations as outlined in the three design manuals. The culverts are modelled and analyzed in Prokon as two-dimensional plane frame structures using the frame analysis module by applying this load to determine maximum positive hogging moments, maximum negative sagging moments and maximum positive shear forces for each span for the top slab. The load forces obtained for each span are then plotted against the soil cover depth to illustrate the discrete load effect of the vertical earth load and live load on the culverts at varying fill height and to determine the relationship between the culvert geometry, soil cover depth and the applied load. The result of the analysis shows that an increasing non-linear relationship exists between the load effects, the soil cover depth, and the span length. The dead load effect increases with increasing fill depth and culvert span while the live load effect diminishes with increasing fill height and culvert span i.e., for culverts buried at shallow depths, the traffic live load is the most critical load but as the height of the soil cover increases the dead load becomes more significant until a point is reached where the live load is totally insignificant. The vertical earth loads obtained from TMH7 and BD31/01 are constant at a particular fill depth for each culvert despite the different span length. The vertical earth load for these two manuals is estimated from the soil cover depth and density, the load tabulated clearly is independent of the culvert geometry. The load obtained from AASHTO LFRD is the lowest and less than 20% of the load obtained from the other two design manuals. Unlike TMH7 and BD31/01, AASHTO LFRD considers the effect of the soil-structure interaction to adjust the vertical earth load on the structure which automatically reduces the load value. The vertical earth load values obtained from TMH7 and BD31/01 are generally more conservative as compared to those obtained from AASHTO LFRD.

Standards and regulations for dimensioning of load-bearing structures are based on the response of load-bearing structures subjected to loads without variation in time. In the event of an accidental load, e.g. a collision or explosion, causes the load to have a rapid variation in the time resulting in a dynamic response. Previous studies have shown that structures that respond in a certain way under static load have shown a completely different behavior under dynamic influence and therefore it is of interest to study the dynamic response of structures.By testing concrete beams with varying amounts of shear reinforcement subjected to impact loading, the purpose of this report is to analyze how the beams responds in terms of crack width and vibrations when they are exposed to a dynamic load. For comparison, reference tests have also been performed on beams subjected to a quasi-static load.The result of the project shows that the shear reinforcement comes into play as the beams with a larger amount of reinforcement have more capacity to hold the flexural shear cracks together. There is also an indication that the dynamic flexural shear capacity could be lower than static shear capacity as the shear cracks had an increased inclination during dynamic loading for some of the beams. This results in a decreased flexural shear capacity as only one stirrup carried the load across the shear crack.Measured signal shows that beams failing respond when impacted by the similar to a plastic collision, while beams responding with a flexure dominated mode without going to failure instead answer similar to an elastic collision. Furthermore, there is indication that the natural frequencies change significantly due to both flexural cracks and flexural shear cracks.

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No description available.

No description available.

The global supply chain has been built on the material handling capabilities provided by the use of pallets and corrugated boxes. Current pallet design methodologies frequently underestimate the load carrying capacity of pallets by assuming they will only carry uniformly distributed, flexible payloads. But, by considering the effect of various payload characteristics and their interactions during the pallet design process, the structure of pallets can be optimized. This, in turn, will reduce the material consumption required to support the pallet industry. In order to understand the mechanical interactions between stacked boxes and pallet decks, and how these interactions affect the bending moment of pallets, a finite element model was developed and validated. The model developed was two-dimensional, nonlinear and implicitly dynamic. It allowed for evaluations of the effects of different payload configurations on the pallet bending response. The model accurately predicted the deflection of the pallet segment and the movement of the packages for each scenario simulated. The second phase of the study characterized the effects, significant factors, and interactions influencing load bridging on unit loads. It provided a clear understanding of the load bridging effect and how it can be successfully included during the unit load design process. It was concluded that pallet yield strength could be increased by over 60% when accounting for the load bridging effect. To provide a more efficient and cost-effective solution, a surrogate model was developed using a Gaussian Process regression. A detailed analysis of the payloads' effects on pallet deflection was conducted. Four factors were identified as generating significant influence: the number of columns in the unit load, the height of the payload, the friction coefficient of the payload's contact with the pallet deck, and the contact friction between the packages. Additionally, it was identified that complex interactions exist between these significant factors, so they must always be considered. / Doctor of Philosophy / Pallets are a key element of an efficient global supply chain. Most products that are transported are commonly packaged in corrugated boxes and handled by stacking these boxes on pallets. Currently, pallet design methods do not take into consideration the product that is being carried, instead using generic flexible loads for the determination of the pallet's load carrying capacity. In practice, most pallets carry discrete loads, such as corrugated boxes. It has been proven that a pallet, when carrying certain types of packages, can have increased performance compared to the design's estimated load carrying capacity. This is caused by the load redistribution across the pallet deck through an effect known as load bridging. Being able to incorporate the load bridging effect on pallet performance during the design process can allow for the optimization of pallets for specific uses and the reduction in costs and in material consumption. Historically, this effect has been evaluated through physical testing, but that is a slow and cumbersome process that does not allow control of all of the variables for the development of a general model. This research study developed a computer simulation model of a simplified unit load to demonstrate and replicate the load bridging effect. Additionally, a surrogate model was developed in order to conduct a detailed analysis of the main factors and their interactions. These models provide pallet designers an efficient method to use to identify opportunities to modify the unit load's characteristics and improve pallet performance for specific conditions of use.

Electrical power systems consist of a large number of power generators connected to consumers through a complex system of transmission and distribution lines. Within the electric grid, a continuous balance between generation and consumption of electricity must be maintained., ensuring stable operation of the grid. In recent decades due to increasing electricity demand, there is an increased likelihood of electrical power systems experiencing stress conditions. These conditions lead to a limited supply and cascading failures throughout the grid that could lead to wide area outages. Demand Response (DR) is a method involving the curtailment of loads during critical peak load hours, that restores that balance between demand and supply of electricity. In order to implement DR and ensure efficient energy operation of buildings, detailed energy monitoring is essential. This information can then be used for energy management, by monitoring the power consumption of devices and giving users detailed feedback at an individual device level. Based on the data from the Energy Information Administration (EIA), approximately half of all commercial buildings in the U.S. are 5,000 square feet or smaller in size, whereas the majority of the rest is made up of medium-sized commercial buildings ranging in size between 5,001 and 50,000 square feet. Given that these medium-size buildings account for a large portion of the total energy demand, these buildings are an ideal target for participating in DR. In this dissertation, two broad solutions for commercial building DR have been presented. The first is a load disaggregation technique to disaggregate the power of individual HVACs using machine learning classification techniques, where a single power meter is used to collect aggregated HVAC power data of a building. This method is then tested over a number of case studies, from which it is found that the aggregated power data can be disaggregated to accurately predict the power consumption and state of activity of individual HVAC loads. The second work focuses on a DR algorithm involving the determination of an optimal bid price for double auctioning between the user and the electric utility, in addition to a load scheduling algorithm that controls single floor HVAC and lighting loads in a commercial building, considering user preferences and load priorities. A number of case studies are carried out, from which it is observed that the algorithm can effectively control loads within a given demand limit, while efficiently maintaining user preferences for a number of different load configurations and scenarios. Therefore, the major contributions of this work include- A novel HVAC power disaggregation technique using machine learning methods, and also a DR algorithm for HVAC and lighting load control, incorporating user preferences and load priorities based on a double-auction approach. / Doctor of Philosophy / Electrical power systems consist of a large number of power generators connected to consumers through a complex system of transmission and distribution lines. Within the electric grid, a continuous balance between generation and consumption of electricity must be maintained., ensuring stable operation of the grid. When electricity demand is high, Demand Response (DR) is a method that can be used to reduce user loads, restoring the balance between demand and supply of electricity. Based on data from the Energy Information Administration (EIA), half of all commercial buildings in the US measure 5,000 square feet or smaller in size, whereas the majority of the other half is made up of medium-sized commercial buildings measuring in at between 5,001 to 50,000 square feet. This makes these commercial buildings an ideal target for participating in DR. In this dissertation, two broad solutions for commercial building DR have been presented. The first is a load disaggregation technique, where power consumption and activity of individual HVACs can be obtained, using a single power meter. The second work focuses on a DR algorithm, that controls single floor HVAC and lighting loads in a commercial building, based on a user generated bid price for electricity, user preferences and load priorities, when electricity demand is at its peak.

O motor de indução é, talvez, o mais robusto e, certamente, um dos motores mais comumente usados. Graças à simplicidade de sua construção, do seu baixo custo, confiabilidade e rendimento relativamente alto com carga nominal é provável que ele permaneça sendo a principal fonte de transformação de energia elétrica em energia mecânica nas aplicações industriais e comerciais por um futuro previsível. O estudo de economia de energia pela redução de perdas é o objetivo do presente estudo. Os motores de indução operam regularmente com fluxo quase constante no entreferro e, portanto, com perdas magnéticas quase constantes. A utilização de um circuito gradador de tensão em série com a alimentação do motor para reduzir o fluxo no entreferro pela redução da tensão aplicada quando a carga não requer fluxo total é o objeto de análise neste estudo. Com a redução da tensão, para manter o conjugado de operação, a velocidade de rotação diminui, ou seja, há um aumento no escorregamento até um valor ótimo para reduzir as perdas totais. Então, esperaria-se que com a redução da tensão aplicada, as perdas magnéticas decresceriam e a eficiência total cresceria. Via de regra, no motor de indução, dada a característica mergulhante de sua curva Conjugado x Velocidade na região em torno da velocidade nominal, o conjugado varia muito mais que a velocidade. Para operação eficiente, a sua tensão aplicada deve ser função da carga que traciona. É objetivo desse trabalho estudar um dispositivo que, colocado em série com a fonte de alimentação de um motor de indução de CA, promove a redução de potência fornecida ao motor, quando a carga aplicada ao motor é menor que a carga nominal. Uma análise da redução da tensão senoidal aplicada através de um auto-transformador de tensão variável é comparada com a redução da tensão através de um circuito gradador baseado em tiristores. A melhor tensão a ser obtida é a que reduz as perdas magnéticas ao mínimo, para cargas que não requerem o fluxo total no entreferro como quando da tensão nominal aplicada. As limitações do processo são estudadas e apresentadas. / The induction motor is perhaps the most rugged, and certainly one of the most commonly used motors. With simply construction, low cost, reliability and efficiency relatively high with rated-load it seems to be a good way to convert electric energy into mechanical energy for industrial and domestic applications for a predictable future. An economy in energy consumption by loss reduction is the goal of this study. The induction motors as normal operate with constant flux in the air-gap and, hence with almost constant losses in the core. The use of a voltage gradador circuit in series with the voltage source applied to the motor for flux reduction in the air-gap by reduction of the voltage when the load do not need full-flux is this study proposal. Hence, with applied voltage reduction, to keep the operational torque, the motor rotation decreases or the slip increases to an optimum value to reduce the total core losses and increase the efficiency. As a rule, the induction motor, by the dip characteristic of the torque x speed curve in the region near the nominal speed, the torque changes much more then the speed. For efficient operation, the applied voltage should be a function of the load. It is the goal or aim of this work to study a device which, when placed in series with the power input of an alternating current induction motor, will produce a reduction in power normally provided to the motor when operated in either a condition where motor loading is less than a rated load. An analysis of voltage ideal sine wave supply reduction applied by an autotransformer with variable voltage is compared with the voltage reduction using a gradador circuit based on thyristors. The optimal voltage operation is the one that decrease the iron losses to minimum, for partial-load that do not need full-flux in the air-gap as when the full voltage is applied. Limitations in the process are investigated and will be showed.

O motor de indução é, talvez, o mais robusto e, certamente, um dos motores mais comumente usados. Graças à simplicidade de sua construção, do seu baixo custo, confiabilidade e rendimento relativamente alto com carga nominal é provável que ele permaneça sendo a principal fonte de transformação de energia elétrica em energia mecânica nas aplicações industriais e comerciais por um futuro previsível. O estudo de economia de energia pela redução de perdas é o objetivo do presente estudo. Os motores de indução operam regularmente com fluxo quase constante no entreferro e, portanto, com perdas magnéticas quase constantes. A utilização de um circuito gradador de tensão em série com a alimentação do motor para reduzir o fluxo no entreferro pela redução da tensão aplicada quando a carga não requer fluxo total é o objeto de análise neste estudo. Com a redução da tensão, para manter o conjugado de operação, a velocidade de rotação diminui, ou seja, há um aumento no escorregamento até um valor ótimo para reduzir as perdas totais. Então, esperaria-se que com a redução da tensão aplicada, as perdas magnéticas decresceriam e a eficiência total cresceria. Via de regra, no motor de indução, dada a característica mergulhante de sua curva Conjugado x Velocidade na região em torno da velocidade nominal, o conjugado varia muito mais que a velocidade. Para operação eficiente, a sua tensão aplicada deve ser função da carga que traciona. É objetivo desse trabalho estudar um dispositivo que, colocado em série com a fonte de alimentação de um motor de indução de CA, promove a redução de potência fornecida ao motor, quando a carga aplicada ao motor é menor que a carga nominal. Uma análise da redução da tensão senoidal aplicada através de um auto-transformador de tensão variável é comparada com a redução da tensão através de um circuito gradador baseado em tiristores. A melhor tensão a ser obtida é a que reduz as perdas magnéticas ao mínimo, para cargas que não requerem o fluxo total no entreferro como quando da tensão nominal aplicada. As limitações do processo são estudadas e apresentadas. / The induction motor is perhaps the most rugged, and certainly one of the most commonly used motors. With simply construction, low cost, reliability and efficiency relatively high with rated-load it seems to be a good way to convert electric energy into mechanical energy for industrial and domestic applications for a predictable future. An economy in energy consumption by loss reduction is the goal of this study. The induction motors as normal operate with constant flux in the air-gap and, hence with almost constant losses in the core. The use of a voltage gradador circuit in series with the voltage source applied to the motor for flux reduction in the air-gap by reduction of the voltage when the load do not need full-flux is this study proposal. Hence, with applied voltage reduction, to keep the operational torque, the motor rotation decreases or the slip increases to an optimum value to reduce the total core losses and increase the efficiency. As a rule, the induction motor, by the dip characteristic of the torque x speed curve in the region near the nominal speed, the torque changes much more then the speed. For efficient operation, the applied voltage should be a function of the load. It is the goal or aim of this work to study a device which, when placed in series with the power input of an alternating current induction motor, will produce a reduction in power normally provided to the motor when operated in either a condition where motor loading is less than a rated load. An analysis of voltage ideal sine wave supply reduction applied by an autotransformer with variable voltage is compared with the voltage reduction using a gradador circuit based on thyristors. The optimal voltage operation is the one that decrease the iron losses to minimum, for partial-load that do not need full-flux in the air-gap as when the full voltage is applied. Limitations in the process are investigated and will be showed.