Theses and Dissertations at Montana State University (MSU)
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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 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.