Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
3 results
Search Results
Item Structural analysis of the Benkar Fault Zone, a cross structure in the higher Himalaya of the Khumbu Region, eastern Nepal(Montana State University - Bozeman, College of Letters & Science, 2019) Seifert, Neil Jordan; Chairperson, Graduate Committee: Mary S. HubbardThe Himalaya are dominated by laterally continuous, range-parallel thrust faults and less frequent extensional structures such as the South Tibetan Detachment system. Recent discovery of range-perpendicular strike-slip and extensional fault zones (cross structures) in the Himalaya has raised questions regarding the significance of these structures in the collisional process. I have analyzed a newly-recognized cross structure in the Khumbu region of eastern Nepal, the Benkar Fault Zone. Structural mapping, petrographic observation, and analytical evidence reveals a zone of consistently NE-striking, SE-dipping metamorphic foliation from the villages of Phakding to Gorak Shep along the Dudh Kosi valley. Deformation within this zone is restricted to foliation-parallel, nonpenetrative, anastomosing sillimanite- and mica-bearing shear zones that wrap around poorly deformed quartz and feldspar enclaves. Kinematics of these shear zones from thin sections and outcrop observations are consistent with normal, right-lateral oblique slip and some local zones of purely extensional displacement. Quartz crystallographic fabric orientation suggests crystal plastic deformation under upper greenschist to lower amphibolite facies conditions. Outcrop observations show evidence for isolated brittle-ductile deformation, suggesting short-lived brittle events that punctuated a history of predominantly plastic deformation. Benkar Fault Zone fabric crosscuts older, thrust-related foliation and suggests that deformation within the zone postdates peak metamorphism and occurred while rocks were on the retrograde path. Crosscutting relationships between Benkar Fault Zone fabric and leucogranites constraints the timing of deformation to be younger than 20.5-21.3 Ma. The Benkar Fault Zone is interpreted to represent a tear fault within the Greater Himalayan sequence associated with differential displacement along a structurally deeper thrust.Item Experimental and analytical investigation of masonry infill and confined masonry wall assemblies(Montana State University - Bozeman, College of Engineering, 2017) Johnson, Maxim Gordon; Chairperson, Graduate Committee: Damon FickMasonry has the benefit of strength and ease of construction but lacks the ability to resist lateral forces due to its brittle nature. However, with the addition of concrete confining frames to plain masonry walls, additional strength and ductility can be attained. Two such confinement systems include masonry infill and confined masonry walls. Currently, masonry infill assemblies are the most common form of lateral force resisting systems in countries where access to more traditional concrete and steel materials is limited. However, recent studies have stated that confined masonry provides improved performance because of the bond between the concrete and brick. This thesis presents an investigation of the behavior of both types of concrete confinement methods and identifies advantages of each system with regards to strength, ductility, and performance during strong ground motion events. To accomplish this objective, 1/3-scale specimens were constructed and tested in direct shear to determine the load-displacement response for both masonry infill and confined masonry walls and compared with results of each type of concrete confinement technique as compared to a plain masonry specimen. The masonry infill wall strength was 35% larger and deflected ten times more than the plain masonry wall at peak load. The confined masonry showed 80% more strength capacity; however, only deflected 2.5 times more than the plain masonry wall at peak load. The test results were incorporated into analytical models that approximated the load displacement response observed during the tests. The models were used to perform a nonlinear push-over analysis on a reduced scale 5-story building damaged by the Nepal earthquake. The first story walls of the confined masonry model failed at a base shear that was 27% larger than the masonry infill model. First story drifts were 64% larger in the masonry infill model. This supports the general observation that each wall has merit in a specific design scenario. Masonry infill walls may be preferred in for designs where energy dissipation may be critical. On the strength side, confined masonry walls may be preferred where strength is preferred over ductility.Item Deflection of a circular plate subjected to blast loading(Montana State University - Bozeman, College of Engineering, 1968) May, Larry Eugene