UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Behavior of fiber reinforced polymer piles with octagonal cross-sections in integral abutment bridge foundations(2020) Gupta, Kavach; Amde, Amde M; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Billions of dollars worth of losses are incurred due to corrosion and degradation of bridges in the United States. In a conventional bridge, deicing salts and chemicals cause rapid degradation in expansion joints, stiffeners, and other structural components. One of the solutions to tackle such a problem is to eliminate expansion joints in the system and design the whole bridge as an integral abutment bridge. In this type of bridge, the abutment and the deck act as a monolithic system. An integral abutment bridge has no expansion joints. Movement due to thermal expansion and contraction is accommodated by the abutments, which in turn transfer the movement to the piles. The maintenance costs of integral abutment bridges are considerably lower than the traditional jointed bridges; therefore, most state highway departments in the United States recommend the use of integral abutment bridges whenever possible. Using alternatives to conventional piling materials is another solution discussed in this thesis and will be the main focus of the same. Fiber Reinforced Polymer (FRP) piles have some advantages in corrosion resistance and hence can be economical in aggressive environments. In this thesis, FRP piles with octagonal cross-sections were analyzed for their behavior in integral abutment bridges. The octagonal section can easily be manufactured using a vast array of manufacturing methods, especially by the filament winding method, which is a cheaper manufacturing option as compared to other methods like pultrusion. Octagonal sections provide flat surfaces that make operations like bolting easy. In addition to this, irregular octagonal sections can provide stiffness and flexibility about two perpendicular axes simultaneously. Three-dimensional models were made and analyzed using ANSYS Workbench with the help of ANSYS Composite PrePost (ACP) modules. Over 300 soil-pile models were analyzed in this study. The results in this thesis depict the trends captured by varying different parameters for various soil-pile models.Item BEHAVIOR OF FIBER REINFORCED POLYMER COMPOSITE PILES WITH ELLIPTICAL CROSS SECTIONS IN INTEGRAL ABUTMENT BRIDGE FOUNDATIONS(2016) Aliabadizadeh, Yahya; Amde, Amde M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Every year in the US and other cold-climate countries considerable amount of money is spent to restore structural damages in conventional bridges resulting from (or “caused by”) salt corrosion in bridge expansion joints. Frequent usage of deicing salt in conventional bridges with expansion joints results in corrosion and other damages to the expansion joints, steel girders, stiffeners, concrete rebar, and any structural steel members in the abutments. The best way to prevent these damages is to eliminate the expansion joints at the abutment and elsewhere and make the entire bridge abutment and deck a continuous monolithic structural system. This type of bridge is called Integral Abutment Bridge which is now widely used in the US and other cold-climate countries. In order to provide lateral flexibility, the entire abutment is constructed on piles. Piles used in integral abutments should have enough capacity in the perpendicular direction to support the vertical forces. In addition, piles should be able to withstand corrosive environments near the surface of the ground and maintain their performance during the lifespan of the bridge. Fiber Reinforced Polymer (FRP) piles are a new type of pile that can not only accommodate large displacements, but can also resist corrosion significantly better than traditional steel or concrete piles. The use of FRP piles extends the life of the pile which in turn extends the life of the bridge. This dissertation studies FRP piles with elliptical shapes. The elliptical shapes can simultaneously provide flexibility and stiffness in two perpendicular axes. The elliptical shapes can be made using the filament winding method which is a less expensive method of manufacturing compared to the pultrusion or other manufacturing methods. In this dissertation a new way is introduced to construct the desired elliptical shapes with the filament winding method. Pile specifications such as dimensions, number of layers, fiber orientation angles, material, and soil stiffness are defined as parameters and the effects of each parameter on the pile stresses and pile failure have been studied. The ANSYS software has been used to model the composite materials. More than 14,000 nonlinear finite element pile models have been created, each slightly different from the others. The outputs of analyses have been used to draw curves. Optimum values of the parameters have been defined using generated curves. The best approaches to find optimum shape, angle of fibers and types of composite material have been discussed.Item Pyrolysis of Reinforced Polymer Composites: Parameterizing a Model for Multiple Compositions(2015) Martin, Geraldine Ellen; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A single set of material properties was developed to describe the pyrolysis of fiberglass reinforced polyester composites at multiple composition ratios. Milligram-scale testing was performed on the unsaturated polyester (UP) resin using thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) to establish and characterize an effective semi-global reaction mechanism, of three consecutive first-order reactions. Radiation-driven gasification experiments were conducted on UP resin and the fiberglass composites at compositions ranging from 41 to 54 wt% resin at external heat fluxes from 30 to 70 kW m-2. The back surface temperature was recorded with an infrared camera and used as the target for inverse analysis to determine the thermal conductivity of the systematically isolated constituent species. Manual iterations were performed in a comprehensive pyrolysis model, ThermaKin. The complete set of properties was validated for the ability to reproduce the mass loss rate during gasification testing.