Browsing by Subject "Seismic analysis"

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Seismic analysis and evaluation of a building retrofitted with new RC walls
(2021-08-12) Mursel, Seda; Helwig, Todd Aaron, 1965-; Murcia-Delso, Juan
This thesis presents a study on the seismic performance of a retrofitted concrete building in Mexico City. The original lateral force resisting system consisted of reinforced concrete (RC) columns supporting waffle slabs along with RC walls located in the elevator core. After having suffered damages during an earthquake in 2017, the building was retrofitted by adding new RC shear walls. The structural response of the retrofitted building was evaluated using nonlinear analytical models. The response and performance of the newly-added RC wall components were studied employing nonlinear truss models and strain-based acceptance criteria. The results of the wall evaluations were compared with those obtained using the ASCE/SEI 41-17 methodology, which involves backbone moment-rotation relations and rotation limits for the plastic hinges of flexure-dominated walls. The results of the truss models were used to adjust the calibration of hinge models for each of the wall components. A three-dimensional nonlinear model of the entire building was developed employing nonlinear frame elements with plastic hinges for the walls. Two different calibrations of the hinge models were considered: the ASCE/SEI 41-17 moment-rotation curves and the adjusted curves derived from nonlinear truss models. The performance of the retrofitted building was, thereafter, evaluated using nonlinear static analysis, and the results obtained with the two hinge calibrations were compared.
Seismic and morphologic analysis of the Gulf of Alaska Yakutat margin : evidence for recent trough mouth fan growth
(2014-08) Swartz, John Marshall; Gulick, Sean P. S.; Goff, John; Catania, Ginny
The active St. Elias Orogen in southern Alaska was created by collision of the offshore Yakutat Terrane with North America. These mountains exhibit the highest coastal relief in the world and also are home to temperate tidewater glaciers, one of the most powerful erosive agents known. Glaciation in Southern Alaska has occurred since the Miocene, but climatic shifts associated with the intensification of Northern Hemisphere glaciation at ~2.5 Ma and the mid-Pleistocene transition at ~1 Ma have led to drastic increases in glacial erosion and associated offshore sediment transport and deposition. The Yakutat continental shelf has hosted ice streams during glacial advances since the mid-Pleistocene, but it is only recently that ice has reached the continental shelf edge itself. Quantitative morphologic analysis finds significant variability along the slope, with an relatively gentle gradient trough mouth fan building off the Yakutat Sea Valley, a shelf-crossing glacial trough, due to massive sediment supply from the heart of the St. Elias Orogen, while farther to the east the extremely steep continental margin is heavily gullied and sediment bypasses the slope reaching the offshore Surveyor fan. Seismic stratigraphy indicates that ice streams first reached the shelf edge with the mid-Pleistocene climate transition, a shift from 41 ka to 100 ka glacial-interglacial climate cycles. This increase in glacial durations allowed not only the ice to sustain advances to the shelf edge, but led to amplified erosion and climate-tectonic feedback effects.