Scholarship & Research
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Item Use of geothermal bridge deck deicing systems to mitigate concrete deterioration in Montana(Montana State University - Bozeman, College of Engineering, 2023) Turner, Ethan Joseph; Co-chairs, Graduate Committee: Kirsten Matteson and Mohammad KhosraviReinforced concrete bridge decks face deterioration from thermal stresses, frost action, and early-age cracking. This thesis presents experimental testing and numerical simulations on a bridge deck deicing system's ability to mitigate concrete deterioration. Two experimental bridge deck models were constructed with embedded heat exchanger tubing and instrumented with thermocouples and strain gauges. The models were tested in a cold chamber laboratory under conditions representative of Montana winter weather. The experimental results suggested that a bridge deck deicing system with an inlet temperature of 8 °C shows promise in deicing, reducing thermal movements, and mitigating early-age cracking through thermal shrinkage. The temperature and strain results of the experiment were used to validate a numerical model constructed in COMSOL Multiphysics. Inlet fluid temperatures of 10 °C and 50 °C, chosen from common ground temperatures in Montana, were tested to evaluate the system's effect on frost action and thermal stresses. With a 10 °C inlet fluid temperature, the system showed promise in deicing and mitigating concrete deterioration. While the system did not always raise the surface temperature above 0 °C, the consistent increase in temperature suggested that under certain weather conditions, the system could keep the top surface temperature above 0 °C for a longer period than with no system. The system was also successful in reducing the range of strain due to thermal movements. The system was not able to mitigate the effects of frost action or temperature gradients. The temperature gradients induced by the system were at times worse than without the system, but the difference was insignificant. With a 50 °C fluid temperature, the system was more effective in deicing and mitigating frost action. The range of strain from thermal movements was also reduced more than with a 10 °C inlet fluid temperature. The thermal gradients, however, were at times slightly greater than design gradients provided by design specifications. The excessive gradients, however, only occurred during extreme weather conditions that are less common in Montana. While not perfect, geothermal bridge deck deicing systems show promise for mitigating some mechanisms of concrete deterioration, while keeping other mechanisms within allowable limits.Item Concrete-filled steel tube to concrete pile cap connections: verification of analysis/design methodologies(Montana State University - Bozeman, College of Engineering, 2023) Cota, Cash Daniel; Chairperson, Graduate Committee: Michael BerryThis research project focuses on the structural behavior of concrete-filled steel tube (CFST) to concrete pile cap connections, a critical component in many Montana bridges. A series of four experimental pile cap connection specimens were designed and tested to assess the influence of key parameters such as specimen scale, concrete strength, and the incorporation of U-bars on the overall connection performance. The findings from this research revealed that all specimens, barring the specimen with U-bars, displayed consistent moment-drift responses, damage progression, and failure mechanisms within the concrete cap. The inclusion of U-bars notably increased the connection capacity by about 60%, altering the failure mechanism to a plastic hinge formation in the CFST pile. Additionally, the study validated the efficacy of a novel moment-rotation methodology for predicting the capacity of cap connections, with an average measured-to-predicted ratio of 0.95 and a coefficient of variation of 10%. However, this methodology showed a tendency to overpredict capacities in connections without U-bars and underpredict in those with U-bars. Overall, this research provides valuable insight into the behavior of these critical connections under diverse conditions and demonstrates the efficacy of the moment-rotation methodology.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 Feasibility of non-proprietary Ultra-High Performance Concrete (UHPC) for use in highway bridges in Montana: phase III implementation(Montana State University - Bozeman, College of Engineering, 2022) Hendricks, Elias Michel; Chairperson, Graduate Committee: Michael BerryUltra-high performance concrete (UHPC) has mechanical and durability properties that far exceed those of conventional concrete. However, using UHPC in conventional concrete applications has been cost prohibitive, with commercially available/proprietary mixes costing approximately 30 times more than conventional concrete. Previous research conducted at MSU developed a nonproprietary UHPC mix design (MT-UHPC) that is significantly less expensive than commercially available mixes and is made with materials readily available in Montana. The focus of the research discussed herein was on the field implementation of MT-UHPC. Specifically, MT-UHPC was used in all field-cast joints on two bridges spanning Trail Creek on Highway 43 outside of Wisdom, MT. This project began with an extensive literature review focused on previous field applications of UHPC. Subsequently, implementation research was performed with the intent of filling several research gaps related to the field application of MT-UHPC. This research investigated the effects that mixing process, batch size, and temperature have on the performance of MT-UHPC. It also developed maturity curves to be used in estimating the early strength gain of MT-UHPC. Trial batches were then conducted on site and placed into joint mockups to confirm and improve the construction methods to be used on the actual bridge project. In this exercise MT-UHPC was mixed using the same methods and under the same environmental conditions expected on the day of construction. MTUHPC was then used in the Trail Creek bridges to connect the precast concrete bridge elements. Overall, this project was a successful demonstration of using a nonproprietary UHPC in field-cast joints for an accelerated bridge construction (ABC) project. All placed UHPC had adequate flows, gained strength quickly, and reached the required minimum compressive strengths. This was accomplished despite an accelerated construction schedule, and despite mixing and placing the material in the field under varied environmental conditions.Item Feasibility of non-proprietary ultra-high performance concrete (UHPC) for use in highway bridges in Montana: phase II field application(Montana State University - Bozeman, College of Engineering, 2020) Scherr, Riley James; Chairperson, Graduate Committee: Michael BerryUltra-high performance concrete (UHPC) has properties far exceeding those of conventional concrete. The MDT Bridge Bureau is interested in using UHPC in field-cast joints between precast concrete deck panels. The primary objective of the research discussed herein was to further investigate and develop a non-proprietary UHPC mix developed for use in Montana. Specifically, this research (1) investigated the potential variability in concrete performance related to differences in constituent materials, (2) investigated issues related to the field batching/mixing of the these UHPC mixes, and (3) tested rebar bond strength and its effects on requisite development lengths. Throughout this research project, the different aspects used to test the UHPC performance and prepare the UHPC, further detailed in chapter 3 of this report, are mixing procedures, flow testing, specimen casting, preparation and curing procedures, compression testing, flexure testing, set time estimates, and bond strength/pullout capacity testing. Variations in the source of the constituent materials had fairly minor effect on UHPC performance. Flow generally increased with increasing aggregate moisture content, and the 7- and 28-day compressive strengths generally decreased. Adjusting the mix water to account for the varying aggregate moisture contents did not have a significant effect on flow, but it was observed to slightly increase the compressive strengths in many cases. The UHPC mixes obtained strengths exceeding 10 ksi in the first 24 hours and continued to gain strength over the duration of testing, ultimately reaching strengths of around 20 ksi at 182 days. Batch size did not have a significant effect on flow or compressive strength; however, larger scale mixes required 10% more water and HRWR in order to obtain the same performance when size was increased from 0.2 cu. ft. to 2.5 cu. ft. or larger. Flow was observed to decrease with increasing temperature, while the compressive strengths for the hottest mix were consistently the lowest. The reinforcement that met the minimum FHWA recommendations all reached maximum applied pullout stresses above the rebar yield strengths. This indicates that the FHWA embedment depth recommendations should be suitable for use in the purposed bridge closure pours with this research's developed UHPC mix.Item An investigation of a prefabricated steel truss girder bridge with a composite concrete deck(Montana State University - Bozeman, College of Engineering, 2018) Kuehl, Tyler William; Chairperson, Graduate Committee: Damon FickSteel truss girder bridges are an efficient and aesthetic option for highway crossings. Their relatively light weight compared with steel plate girder systems make them a desirable alternative for both material savings and constructability. A prototype of a welded steel truss girder constructed with an integral concrete deck has been proposed as a potential alternative for accelerated bridge construction (ABC) projects in Montana. This system consists of a prefabricated welded steel truss girder topped with a concrete deck that can be cast at the fabrication facility (for ABC projects) or in the field after erection (for conventional projects). To investigate possible solutions to the fatigue limitations of certain welded member connections in these steel truss girders, bolted connections between the diagonal tension members and the top and bottom chords of the steel truss girders were evaluated. A 3D finite element model was used to more accurately represent the distribution of lane and truckloads to the individual steel truss girders. This distribution was compared to an approximate factor calculated using an equivalent moment of inertia with expressions for steel plate girders from AASHTO. A 2D analytical model was used to investigate the fatigue strength of the bolted and welded connections for both a conventional cast in place deck system and an accelerated bridge deck system (cast integral with the steel truss girder). Truss members and connections for both construction alternatives were designed using loads from AASHTO Strength I, Fatigue I, Fatigue II, and Service II load combinations. A comparison was made between the two steel truss girder configurations and 205 ft. steel plate girder used in a previously designed bridge over the Swan River. Material and fabrication estimates suggest the cost of the conventional and accelerated construction methods is 10% and 26% less, respectively, than the steel plate girder designed for the Swan River crossing.Item 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 Axial capacity of piles supported on intermediate geomaterials(Montana State University - Bozeman, College of Engineering, 2008) Brooks, Heather Margaret; Chairperson, Graduate Committee: Robert L. MokwaPile foundations used to support bridges and other structures are designed and installed to sustain axial and lateral loads without failing in bearing capacity and without undergoing excessive movements. The axial load-carrying capacity of a driven pile is derived from friction or adhesion along the pile shaft and by compressive resistance at the pile tip. There are well established analytical methods for evaluating pile capacity and for predicting pile driving characteristics for cohesive soil, cohesionless soil, and rock. However, past experience indicates these methods may not be reliable for piles driven into intermediate geomaterials (IGMs), which often exhibit a wide array of properties with characteristics ranging from stiff or hard soil to soft weathered rock. Methods to determine the axial capacity, driving resistance, and long-term resistance of piles driven into intermediate geomaterials are not well established. Nine projects, in which piles were driven into IGMs, from the Montana Department of Transportation were analyzed. Each project contained information from CAPWAP dynamic analyses, construction records, and design reports. The purpose of any analyses, of the nine projects, was to better predict the behavior of piles in IGMs. IGMs were divided into two broad types, cohesive and cohesionless. The computer program DRIVEN is often used to predict the axial capacities of piles; however, in IGMs the design method is unreliable. Attempts were made to determine trends within the available data. Normalized resistances for shaft and toe capacities did yield slight correlations of shaft resistance to pile length in IGMs. Iterative solutions using DRIVEN to match the CAPWAP ultimate capacity did not provide meaningful trends or correlations. Slight modification of MDT's original DRIVEN inputs was required in most cases to match the CAPWAP ultimate capacity. Because no meaningful trends were found from analysis, other capacity calculation methods were used to determine other methods that accurately predict pile capacity within IGMs. The Washington Department of Transportation Gates formula is the most accurate method of those attempted. More research is required for further analysis of piles in IGMs.