Scholarship & Research
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Item Exploration of UHPC applications for Montana bridges(Montana State University - Bozeman, College of Engineering, 2023) Starke, James Gerald; Chairperson, Graduate Committee: Kirsten MattesonThe following research project explores bridge applications of ultra-high performance concrete (UHPC). Bridge deterioration is a problem across Montana and UHPC overlays and patching/repairing have been found to be viable alternatives to bridge replacement. The current study began with a literature review on research, specifications, and implementation projects of UHPC bridge deck overlays. A report from FHWA was highlighted that summarized the results of previous overlay and repair projects, and developed their own recommendations. A material-level evaluation was performed on three UHPC mixes, primarily focusing on workability, compressive strength, tensile strength, and tension and shear bond strengths. All three UHPCs exhibited adequate behavior and the resultant properties were above recommendations from ACI for concrete repair and overlay applications. Based on the material-level evaluation results, a thixotropic version of Ductal was chosen for subsequent structural testing. Five slab test specimens were designed and constructed to model a deck section from an existing bridge in Montana. The testing and specimens were designed to determine the effects that including a UHPC overlay, overlay thickness, and substrate concrete strength have on the ultimate moment capacity. The slabs consisted of one control slab, two slabs with varying UHPC overlay depths, one with weak substrate concrete, and one tested to emulate a negative moment region on a bridge deck. The testing demonstrated that including a UHPC overlay increased the ultimate moment capacity of the slabs, even with a weak substrate concrete, but cause the slabs to fail in shear rather than concrete crushing. Additionally, the results imply that a weak deck strengthened with a thin UHPC overlay will respond similarly to a deck composed of much stronger normal concrete. The tensile capacity of the UHPC plays a large role in the overall strength and stiffness of a slab subjected to a negative moment and the tensile strength should be included in capacity calculations, as recommended by FHWA. Overall, the results are promising and shed light on how a UHPC overlay may contribute to the overall strength of an existing bridge deck if implemented in a future overlay project in Montana.Item Performance of FRP-strengthened reinforced concrete beams subjected to low temperature(Montana State University - Bozeman, College of Engineering, 2021) Ahmed, Emtiaz; Chairperson, Graduate Committee: Kirsten MattesonThe use of Fiber Reinforced Polymer (FRP) to repair and strengthen existing concrete structural elements (beams, columns, beam-column connections, and slabs) has become globally accepted and popular. FRP can be used for this application in several forms, such as externally applied wrapping, Near Surface Mounted (NSM) bars, lamination, and sheets. The strength to weight ratio of this material is one of the main criteria that makes this material approved and desired by engineers and researchers for this application. Also, FRP is corrosion resistant and requires less installation time compared to other repairing techniques such as jacketing, section enlargement, and external post tensioning. The performance of FRP repairs has been studied extensively at conventional, non-extreme temperatures; however, little research has been conducted on the performance of these repairs at cold temperatures. The research discussed herein aims to fill this gap in knowledge so that FRP repairs can be more widely used in cold temperature environments, such as for bridge repairs in the state of Montana. In this work, six beams (6 in. x 8 in., 10 ft long) were constructed and tested in four-point bending at two different temperatures (room temperature and -40 °C). For each temperature, there were three beam types: 1) a control beam, 2) a longitudinal strengthened beam, and 3) a longitudinal + transverse strengthened beam. Overall, the results showed that low temperatures have a generally positive effect on concrete strength and beam performance. The average concrete compressive strength of frozen cylinders at -40 °C was observed to be 87.18% higher than the cylinders tested at room temperature. For all beam types, the ultimate load carrying capacity of the low temperature beams exceeded the capacity of the counterpart beam tested at room temperature. Additionally, at lower temperatures the strengthened beams showed delayed FRP delamination (occurring at higher displacements). Further, the initial stiffnesses of the cold beams were found to be significantly higher than the room temperature beams. Overall, the results of this study are promising for the potential of use of FRP for repairs in cold environments and future research is warranted.Item Pilot study of a high capacity ductile seismic holdown for cross laminated timber(Montana State University - Bozeman, College of Engineering, 2019) Nicholas, John Howison; Chairperson, Graduate Committee: Damon FickNew manufactured wood products referred to as mass timber have allowed for greater seismic load capacities than ever before for designing wood structures. The increased capacities could allow for taller wood structures; however, traditional wood connections do not meet the seismic performance needs for new manufactured wood products such as cross laminated timber (CLT). New connection methods must be investigated to allow for the growth of the CLT industry in mid- and high-rise structures. The objective of this research is to develop a wood connection to resist larger uplift forces experienced in CLT structures and provide energy dissipation in seismic events. The connection development was performed through fastener testing using self-drilling dowel fasteners for concealed connections with steel knife plates installed in a wood member. Finite element modeling and testing of reduced section steel plate to provide a ductile response to cyclic loading was performed to determine the feasibility of this connections style. The results of the investigation indicate that reduced section steel plates that limit the connection failure to a desired location in the steel plate could greatly increase the seismic performance of CLT seismic force resisting systems.Item Determination of elastic constants for geosynthetics using in-air biaxial tension tests(Montana State University - Bozeman, College of Engineering, 2018) Haselton, Henry Nathaniel; Chairperson, Graduate Committee: Steven PerkinsGeosynthetics are polymeric membranes used for structural reinforcement for many geotechnical applications such as reinforced pavement. Geosynthetics have been shown to increase the service life of roadways in a variety of field tests. The knowledge of geosynthetics and design methodologies could be improved with a better understanding of geosynthetic material properties. To better understand how geosynthetics perform in field loading situations, geosynthetic tensile resilient material properties are needed. The properties of geosynthetics of interest for this thesis are the resilient tensile modulus of elasticity and Poisson's Ratio (elastic constants) in both material directions. Modulus of elasticity has been traditionally calculated using wide-width uniaxial tests, which is a poor representation of field loading conditions due to the unrestrained sides of the material. Biaxial tension tests are a better representation of field loading conditions and thus were implemented for determination of elastic constants pertaining to different geosynthetic materials. Biaxial tension tests were performed on cruciform shaped samples using a custom device built by the Western Transportation Institute at Montana State University to test geosynthetic samples. A biaxial testing procedure was created using conclusions from a uniaxial testing program implemented to examine the resilient response of geosynthetics after being subjected to four types of loading (cyclic stress relaxation, monotonic stress relaxation, cyclic creep and monotonic creep) over different durations of time. The conclusions of the uniaxial testing program, the available literature and ASTM D7556 were synthesized to create a biaxial testing procedure. Biaxial tension tests were performed in three modes of loading to simulate loading conditions and loadings where a geosynthetic experiences loading in both directions simultaneously. The biaxial tension tests generated stress and strain data used to calculate the elastic constants of six biaxial geogrids and two woven geotextiles. The elastic constants were calculated using an orthotropic linear elastic constitutive model with a least squares approximation. The elastic constants calculated for each geosynthetic material were shown to represent the resilient behavior of geosynthetics in different field loading situations with more realistic boundary conditions than previous uniaxial tests used to characterize the resilient response of geosynthetics.Item Characterizing the mechanical and structural performance of hydraulic-lime CMU wall components and assemblies(Montana State University - Bozeman, College of Engineering, 2015) Haunt, Tucker Trostel; Chairperson, Graduate Committee: Michael BerryConcrete is the most commonly used building material in the world. As a result, the production of portland cement accounts for seven percent of the carbon dioxide produced by industry worldwide. A more environmentally-friendly alternative to portland cement could significantly reduce carbon dioxide emissions, and thus reduce the carbon footprint of the concrete industry. One possible alternative to portland cement is hydraulic lime, which creates less carbon dioxide during its production than portland cement. Further, hydraulic lime reabsorbs carbon dioxide as it cures, through carbonation. Despite these advantages, there are some logistical issues associated with using hydraulic lime in modern construction (e.g., increased cure times). Using hydraulic lime in concrete masonry units provides an opportunity to overcome some of these limitations and thus take advantage of the environmental benefits associated with its use. While the use of lime as the binder in masonry construction is not a new concept, modern building codes have evolved around components made with portland cement rather than hydraulic lime. The, research discussed herein investigates the mechanical and structural performance of hydraulic lime masonry components, and evaluates the efficacy of simple mechanics models used to predict their performance. First, the performance of individual masonry components (i.e., mortar, grout, and block) are evaluated, followed by an evaluation of simple masonry assemblies (e.g., prisms). Finally, a series of five wall assemblies were tested to determine the in-plane shear resistance of hydraulic-lime wall systems. It was found that while the strength of the hydraulic lime masonry components/assemblies were significantly less than those made with portland cement, the use of hydraulic lime in this application is feasible.Item Performance analysis of an experimental field project utilizing asphalt modifiers(Montana State University - Bozeman, College of Engineering, 1999) Johnson, David RichardItem A new aggregate gradation modulus(Montana State University - Bozeman, College of Engineering, 1990) Surdahl, Roger WardItem Determination of geosynthetic constitutive parameters and soil/geosynthetic interaction by in-air and in-soil experiments(Montana State University - Bozeman, College of Engineering, 1998) Cuelho, Eli VincentItem An analytical study of the behavior of composite girder bridges subjected to loads applied parallel to the plane of the slab(Montana State University - Bozeman, College of Engineering, 1969) Khanna, Jagannath KishanchandItem Permanent deformation characteristics of asphalt-aggregate mixtures using varied materials and molding procedures with Marshall method(Montana State University - Bozeman, College of Engineering, 1995) Pradhan, Murari Man