Diplomová práce se zabývá modifikací stávající pozemní verze letounu EV-55 pro možnost přistání na vodní hladině. Snahou je najít takovou variantu, která nepovede k výrazným konstrukčním zásahům do draku letounu a bude vyhovovat stavebnímu předpisu CS 23, zejména požadavkům týkající se plovatelnosti a stability na vodě. Je proveden hmotový rozbor modifikované verze a s tím související omezení hmotové obálky a rozsahu centráží. Zatížení od vody je spočítáno v souladu s CS 23. Pro toto zatížení je následně navrhnuto konstrukční řešení uchycení plováků k trupu a provedena pevnostní kontrola jednotlivých prvků a spojovacích uzlů. Tyto hodnoty jsou dále porovnány s pozemními případy zatížení a stanoveny součinitele rezerv. V závěru jsou spočítány letové výkony: maximální horizontální rychlost, stoupavost, dolet a vytrvalost.

Reinforced concrete frame corners (that is, knee joints) subjected to closing moments plays an important role of transmitting stress between the two adjoining members. Being categorized as geometric discontinuity regions (D-regions), knee joints cannot be correctly analyzed and designed using traditional sectional analysis procedures. Instead, the strut-and-tie method is particularly suitable for such joints. Although strut-and-tie models provide the means to represent the distribution of stresses within a closing knee joint, questions arise when a curved-bar node is used to model the bar bend of the longitudinal reinforcement at the outer corner. The code-specified design expressions for curved-bar nodes have not been experimentally verified; therefore, the accuracy and conservativeness of the expressions remain unknown. This research project is aimed to provide insights to the proper application of the strut-and-tie method, through the concept of curved-bar nodes, to knee joints under closing moments.<br><br>An experimental program consisting of 24 specimens was conducted to investigate the effect of curved-bar nodes on knee joints under closing moments. An evaluation of the code-specified design expressions was included. The results demonstrate that the minimum code-specified bend radius is appropriate. The current requirements related to bond along the bar bend and clear side cover are shown to be conservative. Based on the test results, a procedure for constructing proper strut-and-tie models for closing knee joints is proposed and verified using an evaluation database consisting of 116 knee joint tests from the literature. Compared to other strength predictive methods and the code-specified strut-and-tie method, the proposed strut-and-tie method mitigates unconservativeness and delivers improved accuracy.<br>In addition to the experimental program and the proposed procedure, non-linear finite element analysis (FEA) using the software ATENA-3D was employed to conduct a parametric analysis as a supplement to the experimental data. Seventy-two numerical models were analyzed to further evaluate the code-specified expressions and the proposed strut-and-tie method. The FEA results are in a good agreement with the experimental observations and corroborate the conclusions from the experimental program regarding current code requirements. Moreover, the parametric analysis further supports the application of the proposed strut-and-tie methodology to knee joints under closing moments.

Transportation is a large and growing part of the world’s energy consumption. This drives a need for reduced weight of rail vehicles, just as it does for road vehicles. In spite of weight reductions, the vehicle still has to provide the same level of acoustic comfort for the passengers. Porous materials, with more than 90% air, are often included in multi-layer vehicle panels, contributing to acoustic performance without adding much weight. Here the acoustic performance of open cell porous materials, with focus on flow resistivity, is evaluated based on simplified micro-structure models to investigate the effect of anisotropy on the performance In order to evaluate how the redistribution of material affects the flow resistivity, the porosity of the material is kept constant. Two micro-geometries are analysed and compared: the hexahedral model and the tetrakaidecahedron (Kelvin cell). For flow resistivity calculations the solid frame is assumed to be rigid. The models are elongated in one direction to study the influence of micro-structural anisotropy on the macro level flow resistivity. To keep porosity constant, two different approaches are investigated. The first approach is to let strut thickness be uniform and adjust the volume of the cell to a constant ratio compared to the isotropic case. The second approach is to let the strut volume, and cell volume, be constant. For an anisotropic hexahedral cell with uniform strut thickness, the flow resistivity increases substantially with increasing height to width ratio for the hexahedral model, while the flow resistivity for the tetrakaidecahedron model with uniform strut thickness decreases with increasing height to width ratio. For both geometries and constant strut volume, the average flow resistivity is close to the same constant value. For uniform strut thickness the relative volume of anisotropic to isotropic volume is very important. / <p>The work has been carried out within the Centre for ECO² Vehicle Design.</p><p></p><p>QC 20160523</p>

The purpose of this study is to examine the multidisciplinary design optimization (MDO) of a strut-braced wing (SBW) aircraft compared to similarly designed cantilever wing aircraft. In this study, four different configurations are examined: cantilever wing aircraft, fuselage mounted engine SBW, wing mounted engine SBW, and wingtip mounted engine SBW. The cantilever wing design is used as a baseline for comparison. Two mission profiles were used. The first called for a 7380 nmi range with a 305 passenger load based on a typical Boeing 777 mission. The second profile was supplied by Lockheed Martin Aeronautical Systems (LMAS) and has a 7500 nmi range with a 325 passenger load. Both profiles have a 0.85 cruise Mach number and a 500 nmi reserve range. Several significant refinements and improvements have been made to the previously developed MDO code for this study. Improvements included using ADIFOR (Automatic Differentiation for FORTRAN) to explicitly compute gradients in the design code. Another major change to the MDO code is the improvement of the optimization architecture to allow for a more robust optimization process. During the Virginia Tech SBW study, Lockheed Martin Aeronautical Systems (LMAS) was tasked by NASA Langley to evaluate the results of previous SBW studies. During this time, the original weight equations which were obtained from NASA Langley's Flight Optimization System (FLOPS) was replaced by LMAS proprietary equations. A detailed study on the impact of the equations from LMAS on the four designs was done, comparing them to the designs that used the FLOPS equations. Results showed that there was little difference in the designs obtained using the new equations. An investigation of the effect of the design constraints on the different configurations was performed. It was found that in all the design configurations, the aircraft range proved to be the most crucial constraint in the design. However, results showed that all three SBW designs were less sensitive to constraints than the cantilever wing aircraft. Finally, a double-deck fuselage concept was considered. A double deck fuselage configuration would result in a greater wing/strut intersection angle which would, in turn, reduce interference drag at that section. Due to the lack of available data on double deck fuselage aircraft, a detailed study of passenger and cargo layout was done. Optimized design showed that there was a small improvement in takeoff gross weight and fuel weight over the single-deck fuselage SBW results when compared with a similarly designed cantilever wing aircraft. / Master of Science

The objective of this study is to use Multidisciplinary Design Optimization (MDO) to investigate the use of truss-braced wing concepts in concert with other advanced technologies to obtain a significant improvement in the performance of transonic transport aircraft. The truss topology introduces several opportunities. A higher aspect ratio and decreased wing thickness can be achieved without an increase in wing weight relative to a cantilever wing. The reduction in thickness allows the wing sweep to be reduced without incurring a transonic wave drag penalty. The reduced wing sweep allows a larger percentage of the wing area to achieve natural laminar flow. Additionally, tip-mounted engines can be used to reduce the induced drag. The MDO approach helps the designer achieve the best technology integration by making optimum trades between competing physical effects in the design space. To perform this study, a suite of approximate analysis tools was assembled into a complete, conceptual-level MDO code. A typical mission profile of the Boeing 777-200IGW was chosen as the design mission profile. This transport carries 305 passengers in mixed class seating at a cruise Mach number of 0.85 over a range of 7,380 nmi. Several single-strut configurations were optimized for minimum takeoff gross weight, using eighteen design variables and seven constraints. The best single-strut configuration shows a 15% savings in takeoff gross weight, 29% savings in fuel weight, 28% increase in L/D, and a 41% increase in seat-miles per gallon relative to a comparable cantilever wing configuration. In addition to the MDO work, we have proposed some innovative, unconventional arch-braced and ellipse-braced concepts. A plastic solid model of one of the novel configurations was created using the I-DEAS solid modeling software and rapid prototyping hardware. / Master of Science

Yes / The test results on eight two-span deep beams made of self-compacting concrete (SCC) are presented and discussed in this paper. The main parameters investigated were the shear span-to-depth ratio, and the amount and configuration of steel reinforcement. All beams failed due to a major diagonal crack formed between the applied mid-span load and the intermediate support separating the beam into two blocks: the first one rotated around the end support leaving the other block resting on the other two supports. Both concrete compressive strength and web reinforcement had a major effect in controlling the shear capacity of the beams tested. For the shear span-to-depth ratio considered, the vertical web reinforcement had more influence on the shear capacity of the specimens than the horizontal web reinforcement. The shear provisions of the ACI 318M-11 are unconservative for most of the beams tested. Comparisons of test results with the strut-and-tie model (STM) suggested by ACI 318M-11, EC2 and CSA23.4-04 showed that the predictions are reasonable for continuous deep beams made with low and medium compressive strength. Although the equation suggested by ACI 318M-11 is very simple, its prediction is more accurate than the STM suggested by different design codes. / This research investigation was funded by the Higher Education Ministry in The Libyan Government.

Yes / Nine continuous concrete deep beams reinforced with glass fibre reinforced polymer (GFRP) bars were experimentally tested to failure. Three main parameters were investigated, namely, shear span-to-overall depth ratio, web reinforcement and size effect. The experimental results confirmed the impacts of web reinforcement and size effect that were not considered by the strut-and-tie method (STM) of the only code provision, the Canadian S806-12, that addressed such elements. The experimental results were employed to evaluate the applicability of the methods suggested by the American, European and Canadian codes as well as the previous studies to predict the load capacities of continuous deep beams reinforced with GFRP bars. It was found that these methods were unable to reflect the influences of size effect and/or web reinforcement, the impact of which has been confirmed by the current experimental investigation. Therefore, a new effectiveness factor was recommended to be used with the STM. Additionally, an upper-bound analysis was developed to predict the load capacity of the tested specimens considering a reduced bond strength of GFRP bars. A good agreement between the predicted results and the experimental ones was obtained with the mean and coefficient of variation values of 1.02 and 5.9%, respectively, for the STM and 1.03 and 8.6%, respectively, for the upper-bound analysis. / Higher Committee of Education Development in Iraq (HCED)

[pt] O presente trabalho tem por objetivo desenvolver uma formulação e um sistema que seja uma ferramenta auxiliar para o engenheiro de projeto na definição de modelos de bielas e tirantes de estruturas bi-dimensionais. No sistema desenvolvido o usuário pode partir de um modelo complexo, com um número grande de barras nas mais variadas direções. Essa solução inicial pode se basear nos resultados em tensão de uma análise linear elástica por elementos finitos e na experiência do projetista. Todavia, como o usuário terá muitas dúvidas quanto ao melhor modelo as ser usado, ele pode superpor no modelo inicial todas as soluções que achar possíveis. A função do sistema é escolher entre todas as soluções admissíveis (aquelas que respeitam equilíbrio e resistência) a que for mais econômica. Define-se como solução mais econômica aquela que corresponder ao menor consumo de armadura. A formulação do problema conduz a um problema de Programação Linear (PL) e o programa LINDO [2] é utilizado para resolvê-lo. A visualização do modelo é também parte do sistema desenvolvido e é feito a partir dos resultados gerados pelo programa LINDO. O trabalho se divide basicamente em três partes. Na primeira parte é feita uma revisão sobre modelos de bielas e tirantes e sobre fundamentos de programação linear. A segunda parte consta da formulação do problema e por ultimo os resultados do programa são comparados com aqueles fornecidos pela literatura. A ferramenta desenvolvida neste trabalho pode ser de grande utilidade para a definição de modelos de bielas e tirantes mas ela nem de longe tem a pretensão de substituir a experiência, a intuição e o bom senso do engenheiro de projeto que deve sempre prevalecer, inclusive na análise crítica dos resultados do programa. / [en] The present work has the aim of developing a formulation and a computational system, which should be used by the structural engineers an auxiliary tool in the definition of strut and tie models of bidimensional structures. In the developed system the user can define initially a very complex system with a great number of bars and many different directions. This initial solution can be based on both the stress results of a linear elastic finite element analysis and the experience of the engineer. As the user may be in doubt about the best model to be used he may superimpose in the initial model all the allowable solutions he may find. The aim of the system is to choose among all the allowable solution (these ones wich satisfy equilibrium and strenght) the more economical one. As more economical solution is considered the one which correspond to the least consumption of reinforcement. The problem formulation leads to a linear programming problem (LP) and the LINDO program [2] is used for solving it. The visualization of the model and results is also part of the system. It is based on the data generated by the LINDO program. The work is basicaly divided in three parts. In the first one a revision about strut and tie models as well as the basic knowledge in linear programming is presented. In the second part the problem formulation is shown and the last the results of the program are compared with those old the technical literature. The computational tool presented here may be of great utility in the definition of strut and tie models, but it has not by far the intention and the feeling of the engineers which shall ever prevail, inclusive in the critic analysis of the program results. / [es] El presente trabajo tiene como objetivo desarrollar un sistema que sirva como herramienta auxiliar para el ingeniero de proyecto en la definición de modelos de bielas y tirantes de extructuras bidimensionales. En el sistema desarrollado, el usuario puede partir de un modelo complejo, con un número grande de barras en varias direcciones. Esa solución inicial puede basearse en los resultados en tensión de un análisis lineal elástica por elementos finitos y en la experiencia del proyectista. Como el usuario tendrá muchas dudas respecto al mejor modelo as ser usado, él puede superponer en el modelo inicial todas las soluciones que juzgue posibles. La función del sistema es elegir entre todas las soluciones admisibles (aquellas que respetan equilibrio y resistencia) la que sea más económica. Se define como solución más económica aquella que correspdonda al menor consumo de armadura. La formulación del problema conduce a un problema de Programación Lineal (PL) que es resuelto con ayuda del programa LINDO [2]. La visualización del modelo también es parte del sistema desarrollado y parte de los resultados generados por el programa LINDO. El trabajo se divide básicamente en tres partes. En la primeira parte se realiza una revisión de los modelos de bielas y tirantes y de los fundamentos de programación lineal. La segunda parte contiene la formulación del problema y la presentación de los resultados del programa se comparan con los reportados en la literatura. La herramienta desarrollada en este trabajo puede ser de gran utilidad para la definición de modelos de bielas y tirantes pero no tiene la pretensión de substituir la experiencia, la intuición y el buen senso del ingeniero de proyecto que debe siempre prevalecer, incluso en el análisis crítico de los resultados del programa.

yes / There are very few, if any, available experimental investigations on aggregate interlock capacity along diagonal cracks in lightweight concrete deep beams. As a result, the shear design provisions including the modification factor of ACI 318-08 and EC 2 for lightweight concrete continuous deep beams are generally developed and validated using normal weight simple deep beam specimens. This paper presents the testing of 12 continuous beams made of all-lightweight, sand-lightweight and normal weight concrete having maximum aggregate sizes of 4, 8, 13 and 19 mm. The load capacities of beams tested are compared with the predictions of strut-and-tie models recommended in ACI 318-08 and EC 2 provisions including the modification factor for lightweight concrete. The beam load capacity increased with the increase of maximum aggregate size, though the aggregate interlock contribution to the load capacity of lightweight concrete deep beams was less than that of normal weight concrete deep beams. It was also shown that the lightweight concrete modification factor in EC 2 is generally unconservative, while that in ACI 318-08 is conservative for all-lightweight concrete but turns to be unconservative for sand-lightweight concrete with a maximum aggregate size above 13 mm. The conservatism of the strut-and-tie models specified in ACI 318-08 and EC 2 decreased with the decrease of maximum aggregate size, and was less in lightweight concrete deep beams than in normal weight concrete deep beams.

This study utilizes Multidisciplinary Design Optimization (MDO) techniques to explore the effectiveness of the truss-braced (TBW) and strut-braced (SBW) wing configurations in enhancing the performance of medium range, transonic transport aircraft. The truss and strut-braced wing concepts synergize structures and aerodynamics to create a planform with decreased weight and drag. Past studies at Virginia Tech have found that these configurations can achieve significant performance benefits when compared to a cantilever aircraft with a long range, Boeing 777-200ER-like mission. The objective of this study is to explore these benefits when applied to a medium range Boeing 737-800NG-like aircraft with a cruise Mach number of 0.78, a 3,115 nautical mile range, and 162 passengers. Results demonstrate the significant performance benefits of the SBW and TBW configurations. Both configurations exhibit reduced weight and fuel consumption. Configurations are also optimized for 1990's or advanced technology aerodynamics. For the 1990's technology minimum TOGW cases, the SBW and TBW configurations achieve reductions in the TOGW of as much as 6% with 20% less fuel weight than the comparable cantilever configurations. The 1990's technology minimum fuel cases offer fuel weight reductions of about 13% compared to the 1990's technology minimum TOGW configurations and 11% when compared to the 1990's minimum fuel optimized cantilever configurations. The advanced aerodynamics technology minimum TOGW configurations feature an additional 4% weight savings over the comparable 1990's technology results while the advanced technology minimum fuel cases show fuel savings of 12% over the 1990's minimum fuel results. This translates to a 15% reduction in TOGW for the advanced technology minimum TOGW cases and a 47% reduction in fuel consumption for the advanced technology minimum fuel cases when compared to the simulated Boeing 737-800NG. It is found that the TBW configurations do not offer significant performance benefits over the comparable SBW designs. / Master of Science