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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Finite Element Modeling of Plastic Pails when Interacting with Wooden Pallets

Alvarez Valverde, Mary Paz 04 June 2024 (has links)
The physical supply chain relies on three components to transport products: the pallet, the package, and unit load stabilizers. The interactions between these three components can be investigated to understand the relationship between them to find potential optimization strategies. The relationship between corrugated boxes and pallets have been previously investigated and have found that the relationship can be used to reduce the quantity of material used in unit loads and can also reduce the cost per unit load if the package and pallet are designed using a systems approach. Although corrugated boxes are a common form of packaging, plastic pails are also used in packaging for liquids and powders, but they have not been previously investigated. To understand the interactions between the wooden pallet and plastic pails, physical tests were conducted and then used to create and validate a finite element model. The experiments were carried out in three phases. The first phase included physical testing of plastic pails where the deckboard gap and overhang support conditions would be isolated by using a rigid deckboard scenario. The second phase also used physical tests to investigate plastic pails but instead used flexible deckboards and used an overhang support condition and a 3.5 in. gap support condition. The third phase of experiments would develop and validate a finite element model to further understand the impact of deckboard gaps and overhang depending on the location of the gap. Previous physical experiments were used to create and validate the finite element model. Nonlinear eigen buckling analysis was used to model the plastic pail buckling failure that was seen in physical testing. The model based on the physical experiments was able to predict the behavior of the plastic pail within a range of 5-12% variation with higher variation being introduced when the flexible deckboard is introduced. The finite element model was then used to model a range of deckboard gap sizes and overhang sizes as well as different locations for deckboard gaps. The results of the experiments indicate that the percent of pail perimeter that is supported directly on the pallet impacts the compression strength of the plastic pail. Decreasing the quantity of support decreases the compression strength of the plastic pail in a linear pattern. The location of the deckboard gap also influenced the compression strength because of the quantity of pail being supported being altered. The results of the experiments can be used by industry members to provide guidelines on unit load design to prevent plastic pail failure. Industry members can also use the results as a baseline investigation and further the finite element model by incorporating their own plastic pail design. / Doctor of Philosophy / The physical movement of products relies on three main elements: pallets, packaging, and stabilizers for unit loads. Examining how these components interact helps uncover their relationships and potential strategies for optimization. Previous studies have explored the connection between corrugated boxes and pallets, revealing ways to reduce material usage and costs through a systems-based design approach. While corrugated boxes are commonly studied, plastic pails, used for liquids and powders, have not received similar attention. To understand the dynamics between wooden pallets and plastic pails, physical tests were conducted. The physical experiments illustrated the importance of investigating the relationship within unit loads but there are limitations that exist when doing physical experimentation such as time and materials. A finite element model is a mathematical model that can be used to simulate physical phenomenon to further understand physical interactions without having to conduct physical experiments. Using the results of the physical experiments that were conducted, a finite element model was developed to further investigate the system that exists between pails and pallets. The experiments occurred in three phases. The first phase focused on isolating deckboard gap and overhang support conditions using a rigid deckboard scenario in plastic pail testing. In the second phase, a pallet with flexible deckboards was used to explore overhang and a 3.5-in. gap support condition. The third phase involved creating and validating a finite element model to better grasp the impact of deckboard gaps and overhang, considering gap location. Previous physical experiments guided the model's development and validation. Nonlinear eigen buckling analysis simulated plastic pail buckling failure observed in physical tests. The model predicted plastic pail behavior within a 5-12% variation range, with greater variation when using flexible deckboards. This model explored various deckboard gap and overhang sizes, along with different gap location and found that the quantity of unsupported perimeter that the pail experiences affects the quantity of load that the pail can experience before achieving failure. These results are impactful to industry members because it quantifies the impact that pallets can have on their package. Understanding the interactions between the package and the pallet can also be used to create unit loads that are safer by quantifying the buckling load of plastic pails. Investigating plastic pails and the interactions between pallet components can lead to creating safer and better design unit loads in the industry.
2

Railway sleeper modelling with deterministic and non-deterministic support conditions.

Li, Shan January 2012 (has links)
Railway sleepers have important roles in the complex railway system. Due to different loading condition, poor maintenance of sleeper or bad quality of ballast, a random load distribution along the sleeper-ballast interface may occur. A sleeper design, and also the track system design, which do not consider the random load distribution, could influence the performance of the sleeper and even damage the whole railway system. Thus, a numerical static and dynamic analysis for a pre-stressed concrete mono-block railway sleeper is carried out using finite element method. The structural behaviour of a single sleeper subjected to a random sleeper-ballast interaction is studied in three steps. First, four typical scenarios of support condition for sleeper are discussed in numerical analysis. Second, large enough numerical results under different random support conditions are conducted. Finally, Neural Network methodology is used to study the performance of sleeper under a stochastic support condition. Results of vertical displacement of rail seat, tensile stress at midpoint and underneath rail seat are presented. Moreover, the worst support condition is also identified.
3

Response of Reinforced Concrete Reservoir Walls Subjected to Blast Loading

Fan, Jin January 2014 (has links)
Recent events including deliberate terrorist attacks and accidental explosions have highlighted the need for comprehensive research in the area of structural response to blast loading. Research in this area has recently received significant attention by the civil engineering community. Reinforced Concrete (RC) water reservoir tanks are an integral part of the critical infrastructure network of urban centers and are vulnerable to blast loading. However, there is a lack of research and knowledge on the performance of RC reservoir walls under blast loading. The objective of this research study is to experimentally investigate the performance of reinforced concrete reservoir walls subjected to blast loading and to analyze the structural response. This study provides experimental test data on the performance of reinforced concrete reservoir walls under blast loading and complementary analytical predictions using the Singe-Degree-Of-Freedom (SDOF) analysis method. The reservoir walls in this study were designed according to the water volume capacity using the Portland Cement Association (PCA 1993) methodology. The design was validated using software SAP 2000. The experimental program involved the construction and simulated blast testing of two RC reservoir wall specimens with different support conditions: (1) two opposite lateral edges fixed, bottom edge pinned and top edge free; and (2) two opposite lateral edges fixed, and bottom and top edges free. The first boundary condition was intended to promote two-way bending action, while the second was dominated by one-way bending. The two specimens were each subjected to a total of six consecutive incrementally increasing blast tests. The experimental program was conducted in the shock tube testing facility that is housed in the University of Ottawa. Wall displacements, reinforcement strains, and reflected pressures and impulses were measured during testing. Analytical calculations were conducted using the equivalent SDOF method to simulate the dynamic response of the RC reservoir wall specimens under different blast loadings. Published tables, charts and coefficients contained in Biggs (1964) and UFC 3-340-02 (2008) were adopted in the equivalent SDOF calculations. The analytical results were compared against the ii experimental data. The SDOF method predicted smaller displacements than those recorded during testing. The approximate nature of the parameters and tables used in the equivalent SDOF calculations contributed to the discrepancy between the analytical and experimental results. Furthermore, assumptions regarding the support conditions and neglecting residual damage from previous blast tests contributed to the underestimation of the displacements.

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