Theses and Dissertations at Montana State University (MSU)
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Item In-plane shear behavior of geosynthetics from bias biaxial tests using digital image correlation(Montana State University - Bozeman, College of Engineering, 2019) Schultz, Emily Christine; Chairperson, Graduate Committee: Steven PerkinsGeosynthetics are polymeric membranes used for structural reinforcement of soils in a variety of roadway and foundation applications, many of which create biaxial loading on the geosynthetic. Orthotropic linear elastic models have been used to represent geosynthetic behavior at working load levels for engineering design purposes. Typically, the models rely on index parameters obtained from test methods that do not represent the biaxial field loading conditions. Proper calibration of these models requires load-strain data obtained from tests that have controlled stress and strain boundaries such as biaxial tension tests. Previously at Montana State University, Haselton (2018) successfully used a custom biaxial device to perform biaxial tension tests on cruciform shaped geosynthetic specimens, producing a partial set of resilient elastic constants for two woven geotextiles and six biaxial geogrids. To complete the set of elastic constants by determination of the in-plane shear modulus, another mode of loading was necessary. Literature from biaxial shear tests of architectural membranes suggested cutting the cruciform shaped samples with the principal material directions on a 45-degree bias, which causes the sample to shear when the cruciform axes are unequally loaded. This test mode was successfully implemented with the existing biaxial device to determine the resilient in-plane shear modulus using an orthotropic linear elastic model. Full-field strain measurements were captured using digital imaging correlation (DIC) software available at Montana State University. DIC was shown to produce equivalent strain measurements to the mechanical instrumentation (LVDTs) used by Haselton, enabling a combined dataset. The full-field DIC strain measurements were then used to validate Haselton's assumption regarding the region of uniform strain and to identify the region of uniform strain for data collection in this thesis. DIC also showed reasonably pure biaxial tension in the cruciform samples, validating the elastic constant derivations for both Haselton and this thesis.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 Tentative shear design method for steel fiber reinforced concrete flat plates(Montana State University - Bozeman, College of Engineering, 1984) Ofili, Charles Afamefuna Chukwuemeka