Full-depth precast concrete panels offer an efficient alternative to traditional cast-in-place concrete for replacement or new construction of bridge decks. Research has shown that longitudinal post-tensioning helps keep the precast bridge deck in compression and avoid problems such as leaking, cracking, spalling, and subsequent rusting on the beams at the transverse panel joints. Current design recommendations suggest levels of initial compression for precast concrete decks in a very limited number of bridge configurations. The time-dependent effects of creep and shrinkage in concrete and relaxation of prestressing steel complicate bridge behavior, making the existing recommendations for post-tensioning in precast deck panels invalid for all bridges with differing girder types, sizes, spacings, and span lengths. Therefore, the development of guidelines for levels of post-tensioning applicable to a variety of bridge types is necessary so designers may easily implement precast concrete panels in bridge deck construction or rehabilitation. To fulfill the needs described, the primary objective of this research was to determine the initial level of post-tensioning required in various precast concrete bridge deck panel systems in order to maintain compression in the transverse panel joints until the end of each bridge's service life. These recommendations were determined by the results of parametric studies which investigated the behavior of bridges with precast concrete decks supported by both steel and prestressed concrete girders in single spans as well as two and three continuous spans. The three primary variables in each parametric study included girder type, girder spacing, and span length. The age-adjusted effective modulus method was used to account for the ongoing effects of creep and shrinkage in concrete. Results from the Mathcad models used in the parametric studies were confirmed through comparison with results obtained from finite element models generated in DIANA. Initial levels of post-tensioning for various bridge systems are proposed based on the trends observed in the parametric studies. The precast decks of the simple span bridges with steel girders and the one, two, and three span bridges with prestressed concrete girders needed only 200 psi of initial post-tensioning to remain in compression under permanent and time-dependent loads throughout each bridge's service life. The precast decks of the two and three span continuous bridges with steel girders, however, needed a significantly higher level of initial compression due to the negative moments created by live loads. / Master of Science

Stiffeners attached to composite panels and shells may significantly increase the overall buckling load of the resultant stiffened structure. Initially, an extensive literature review was conducted over the past ten years of published work wherein research was conducted on grid stiffened composite structures and stiffened panels, due to their applications in weight sensitive structures. Failure modes identified in the literature had been addressed and divided into a few categories including: buckling of the skin between stiffeners, stiffener crippling and overall buckling. Different methods have been used to predict those failures. These different methods can be divided into two main categories, the smeared stiffener method and the discrete stiffener method. Both of these methods were used and compared in this thesis. First, a buckling analysis was conducted for the case of a grid stiffened composite pressure vessel. Second, a buckling analysis was conducted under the compressive load on the composite stiffened panels for the case of one, two and three longitudinal stiffeners and then, using different parameters, stiffened panels under combined compressive and shear load for the case of one longitudinal centric stiffener and one longitudinal eccentric stiffener, two stiffeners and three stiffeners. / Master of Science / Aircraft in flight is subjected to different loads due to maneuvers and gust, external forces cause internal loads, which depends on the location of the panel in the aircraft, those internal loads, may result in the buckling of the panel. There is an imminent need for structural efficiency, strong and lightweight material. Stiffened composite panels is a promising technology capable of addressing those needs. Composite stiffened panels have many advantages including but not limited to, small manufacturing cost, high stability, great energy absorption, superior damage tolerance etc. The main failure modes for stiffened composite panels is buckling. Buckling failure modes could be of a global nature, local skin buckling or stiffener/rib crippling, predicting those failure is of high practical importance and a predominant design criterion. An extensive literature review on buckling of stiffened composite panels was conducted in this thesis. Buckling analysis as well as a parametric study of grid stiffened composite cylindrical shell for a pressure vessel was conducted, an analytical solution was derived and verified using ABAQUS, a Finite Element Software. Buckling analysis as well as a parametric study of stiffened panels with longitudinal stiffeners, under different structural situations, was also conducted and results verified.

Sandwich Panels with cellular cores are widely used in the aerospace industry for their higher stiffness to mass, strength to mass ratio, and excellent energy absorption capability. Even though, sandwich panels are considered state of the art for lightweight aerospace structures, the requirement to further reduce the mass exists due to the direct impact of mass on mission costs. Traditional manufacturing techniques have limited the shape of the cores to be either hexagonal or rectangular, but, with rapid advancements in additive manufacturing, other core shapes can now be explored. This research aims to identify and evaluate the mechanical performance of two-dimensional cores having standard wall geometry, which provide higher specific stiffness than honeycomb cores. Triangular cores were identified to have higher specific in-plane moduli and equivalent specific out-of-plane and transverse shear moduli. To consider practical use of the triangular cores, elastic and elastic-plastic structural analysis was performed to evaluate the stiffness, strength, failure, and energy absorption characteristics of both the core and sandwich panels. The comparison made between triangular cores and hexagonal cores having the same cell size and relative density showed that triangular cores outperform hexagonal cores in elastic range and for applications where in-plane loading is dominant. Triangular cores also have excellent in-plane energy absorption capabilities at higher densities. / Master of Science / Sandwich panels with cellular cores are widely used in aerospace structures to reduce weight, which helps increase payload and improve fuel efficiency. They also have the ability to absorb energy during accidental impacts. Sandwich construction typically consists of two thin facesheets separated by a lightweight core and, is analogous to I-beams used in civil structures. Most commonly used core is the hexagonal honeycomb core inspired by beehives. While sandwich panels constructed using honeycomb cores are considered the state-of-the-art for lightweight aerospace structures, there is a need to further reduce the mass due to the direct impact on mission costs. This research aims to explore other core shapes that provide better stiffness to mass ratio than the hexagonal core. Among the two-dimensional cores explored, the triangular shaped core was identified to have higher stiffness than the hexagonal core of the same size and weight. To consider practical use of triangular cores, mechanical performance and failure behavior of sandwich panels constructed using triangular core sandwich panels was compared to hexagonal core sandwich panels. It was concluded that the triangular panels provided higher stiffness for the same mass and was more resistant to failure when axially loaded. Triangular cores also have excellent in-plane energy absorption capabilities at higher densities.

A better understanding of the effect of impact damage on composite structures is necessary to give the engineer an ability to design safe, efficient structures. Current composite structures suffer severe strength reduction under compressive loading conditions, due to even light damage, such as from low velocity impact. A review is undertaken to access the current state-of-development in the areas of experimental testing, and analysis methods. A set of experiments on Nomex honeycomb core sandwich panels, with thin woven fiberglass cloth facesheets, is described, which includes detailed instrumentation and unique observation techniques. These techniques include high speed video photography of compression after impact (CAI) failure, as well as, digital image correlation (DIC) for full-field deformation measurements. The effect of nominal core density on the observed failure mode is described. A finite element model (FEM) is developed to simulate the experiments performed in the current study. The purpose of this simulation is to predict the experimental test results, and to conrm the experimental test conclusions. A newly-developed, commercial implementation of the Multicontinuum Failure Theory (MCT) for progressive failure analysis (PFA) in composite laminates, Helius:MCT, is included in this model. The inclusion of PFA in the present model gives it the new, unique ability to account for multiple failure modes. In addition, significant impact damage detail is included in the model as a result of a large amount of easily available experimental test data. A sensitivity study is used to assess the effect of each damage detail on overall analysis results. Mesh convergence of the new FEM is also discussed. Analysis results are compared to the experimental results for each of the 32 CAI sandwich panel specimens tested to failure. The failure of each specimen is accurately predicted in a high-fidelity, physics-based simulation and the results highlight key improvements in the understanding of honeycomb core sandwich panel CAI failure. Finally, a parametric study highlights the strength benefits compared to mass penalty for various core densities. / Ph. D.

This dissertation presents the development of a new framework for international commercialization of innovative structural products in residential construction. Development of his framework required the examination of six subjects related to international commercialization. 1) commercialization models previously developed, locally and internationally, 2) barriers to the process, 3) stakeholders, actions, and decisions critical to the process, 4) characteristics of innovations that are suitable for international use, 5) characteristics of foreign markets that are ideal to adopt such innovations, and 6) strategies to overcome barriers The framework development was based on one structural product, SIPs. This product has been successfully developed and implemented in the United States and is being considered for commercial use in Saudi Arabia. Structural product clusters are particularly appropriate because of their innovative nature and their major influence on the structure of residential buildings. The study relies on sequential explanatory mixed-method research design, consisting of two distinct phases (Creswell 2003), to gain insight into processes surrounding commercialization. The rationale for this approach is that quantitative data and its results provide a general picture of the barriers to international commercialization in the available sample, which can mapped onto an initial framework. The qualitative data and its analysis help to refine and expand statistical results by exploring participants' actual decision processes that can be also mapped to a second framework. Both data sets can be merged, mapped onto one final framework. Variables related to the six subjects, mentioned above, were distilled from literature into open-ended questionnaires for two groups of key stakeholders in the supply chain of innovative structural products: 1) SIPs stakeholders in the US and 2) stakeholders of innovative structural products in Saudi Arabia. The primary purpose of the open-ended questionnaires was to ensure usage of correct terminology used in this study and to encourage full, meaningful answers—capturing all possible factors affecting the process of international commercialization. The author collected responses using web-based surveys. The results yielded the development of a reliable instrument to be implemented in further steps of this research. Next, the researcher collected variables related to the questions from previous open-ended questionnaires into closed-ended questionnaires to collect the data (on perceived barriers to international commercialization), using web-based surveys, and performed a preliminary analysis of the data using frequency analysis. This process yielded market-based strategies for developing an initial framework for international commercialization in residential construction. Subsequently, a focused examination of barriers to international commercialization was needed. The researcher collected such data through an applied understanding of the specific development processes for SIPs to be introduced to a new, international market, namely Saudi Arabia. Based on the model's structure, the researcher conducted six case studies of real stakeholder processes along the supply chain, SIPs development domestically and internationally, and tracked data for real risks of the commercialization process. Findings suggested perceived versus actual risks and barriers to the commercialization process for an integral product to the residential construction process. This was an important distinction because of proposed development methods and the application of market diffusion. Based on the barriers identified, the researcher developed market-based strategies to be incorporated into a second framework. This framework along with the initial framework and the literature-based framework have been triangulated to develop one final framework. The final framework was then introduced to a few experts in the industry to increase its validity. / Ph. D.

Unitized aircraft structures have the potential to be more efficient than current aircraft structures. The Electron Beam Freeform Fabrication (EBF3) process can be used to manufacture unitized aircraft structures. The structural efficiency of blade stiffened panels made with EBF3 was compared to panels made by integrally machining from thick plate. The panels were tested under two load cases in a combined compression-shear load test fixture. One load case tested the panels' responses to a higher compressive load than the shear load. The second load case tested the panels' responses to an equal compressive and shear load. Finite element analysis was performed to compare with the experimental results. The EBF3 panels failed at a 18.5% lower buckling load than the machined panels when loaded mostly in compression but at an almost two times higher buckling load than the machined panels when the shear matched the compressive load. The finite element analysis was in good agreement with the experimental results prior to buckling. The results demonstrate that the EBF3 process has the capabilities of manufacturing stiffened panels that behave similarly to machined panels prior to buckling. Once the EBF3 panels buckled, the buckled shape of the EBF3 panels was different from the machined panels, generally buckling in the opposite direction of what was observed with the machined panels. This was also expected based on the finite element analysis. The different post-buckling response between the two manufacturing techniques was attributed to the residual stress and associated distortion induced during the EBF3 manufacturing process. / Master of Science

Background: The adoption of solar panels is an important step for companies aiming to enhance their sustainability and reduce carbon footprints. The role of organizational culture and corporate social responsibility (CSR) in driving this adoption is critical. Organizational culture encompasses the values, beliefs, and practices that influence behaviour within a company, while CSR initiatives reflect a company’s commitment to managing its social, economic, and environmental impacts responsibly. Understanding how these internal factors influence the adoption of sustainable technologies like solar panels can provide valuable insights for businesses and policymakers. Purpose: The purpose of this study is to evaluate how solar panel adoption by companies in France can impact their sustainable commitments and strategies. By exploring the interplay between these organizational culture and CSR, the study aims to provide a comprehensive understanding of how cultural values and CSR initiatives drive sustainable practices. The study seeks to contribute to the literature on sustainability in the corporate sector and offer practical insights for companies aiming to integrate solar technology into their operations. Method: This study employs a qualitative research approach, using semi-structured interviews to gather data from representatives of French companies that have adopted solar panels. The sample includes companies from various industries to provide a broad perspective. The interviews focus on understanding the influence of organizational culture and CSR initiatives on the decision to adopt solar technology. Thematic analysis is used to identify patterns and themes in the data, and a comparative analysis is conducted to explore differences and similarities across companies. Conclusion: The findings reveal that organizational culture plays a significant role in the adoption of solar panels. Companies with cultures that prioritize innovation, sustainability, and ethical behaviour are more likely to implement effective CSR initiatives, which in turn facilitate the adoption of solar panels. CSR initiatives act as a mediator, translating cultural values into concrete actions that support sustainability. The study highlights that aligning organizational culture with CSR strategies is crucial for achieving long-term sustainability goals. This alignment not only helps companies comply with regulatory requirements but also enhances their competitive advantage and public image. The study provides practical recommendations for companies seeking to adopt solar technology and underscores the importance of fostering a supportive cultural environment for sustainability initiatives.

Yes / This paper presents research into perceived quality of vehicle body split lines / gaps. The survey based methodology combined direct attribute evaluation and choice experiments with multiple test cases, based on static images generated from parametric CAD virtual prototypes of a specific vehicle. The study systematically tested for perception without and with awareness and the Hawthorne bias, showing significant effects. Statistical analysis provided clear evidence of the user preference for smaller gap size, and as such supports target and tolerance setting for the body gap.

Made available in DSpace on 2016-06-02T20:09:10Z (GMT). No. of bitstreams: 1 2391.pdf: 3213437 bytes, checksum: 14b8d8646353cdd03c7856c4081296ef (MD5) Previous issue date: 2009-03-03 / The increasing of using precast concrete panels, lack of standardization, lack of studies on precast concrete panels and its connections devices on Brazil, has led to the need of manual and design criteria of precast concrete panel connections. Although the designers and precast concrete panel manufacturers is using foreign standards when its available and their empirical knowledge on the specification and connections design criteria, the lack of manuals become hard to find solutions that provide easiness of precast concrete panel s employment. Connections are fundamental part of the precast structures. For the building assembly are necessary linking devices which influences the production process, the efficiency of casting, storage, transport, handling and especially in the assembly on site. This work presents the concept, technical features and functions of main types of spandrel panel connections and the main structure of building, and identifies typical connections and the general design recommendation. This report purpose the put in connection as a new classification of connection type. / Dada a falta de normatização, escassez de estudos sobre painéis pré-moldados, suas ligações e o amplo emprego de painéis pré-moldados nos dias atuais, percebeu-se uma necessidade tanto acadêmica quanto dos projetistas por material de consulta. As empresas fabricantes de painéis se baseiam em normas estrangeiras e no conhecimento adquirido empiricamente para o projeto de ligações de painéis, deste fato surge, portanto, a dificuldade de encontrar soluções para ligações que propiciem a eficácia da aplicação dos painéis. As ligações são parte fundamental dos sistemas pré-moldados, já que para a composição da edificação são necessários dispositivos interligantes , que intrinsecamente interferem em toda a cadeia produtiva e de montagem, ou seja, regem a eficiência nas etapas de fôrma, moldagem, estoque, transporte, manuseio e principalmente na montagem em canteiro. Neste trabalho são apresentadas ligações entre painéis de fachada horizontais pré-moldadas de concreto, a conceituação e a caracterização dos principais tipos e funções das ligações, identificando as diversas ligações existentes relacionando indicações gerais de projeto, além da proposição das ligações por encaixe como nova classificação de elementos de ligação.

This master thesis focuses on modelling and simulation of impact tests of composite panels. Simulations and analysis were made by using Finite Element Method in software MSC Patran and Dytran. The first part of the thesis deals with describing the properties of composite panels during impact testing and other cases of impacts on composite structures. Next part deals with the used models and results from Dytran. These results are compared with experimental data from real low-velocity impact tests. Part of the thesis is devoted to impact on panels with the stacking sequences which is supposed to be used for design of air duct for airplane Aero L-39NG.