Browsing by Author "Singh, Mayshree."

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Investigation of the directional effect on low cost houses due to the 2014 Orkney earthquake.
(2020) Nqasha, Thando.; Singh, Mayshree.
The Orkney earthquake on the 5th August 2014 caused major damages to houses in Orkney and surrounding areas. A post field assessment was carried out to determine the amount of damage caused by the earthquake. The Khuma township near Stilfontein was the most affected area where more than 600 houses were damaged. The damage caused by the 2014, Orkney earthquake was made worse by the poorly constructed low-cost houses in Orkney and the surrounding townships (Khuma, Kanana and Jouberton). These houses were vulnerable to earthquake damage. This study sought to determine the effects of additional factors that contribute to earthquake damage such as: building excitation angle, exposure of building weak points to earthquake direction and building finishes. In this study, results show that building excitation angle, exposure of weak points and finishes either plastered or un-plastered can contribute to the damage and vulnerability of a building during an earthquake tremor. Buildings of excitation angles between 0° - 30° and 61°- 90° had more damages compared to houses that had an excitation angles of between 31°- 60° for all 3 townships (Khuma, Kanana and Jouberton). The excitation angle of 0°- 30° recorded the highest damage grade, followed by excitation angle of 61° - 90°. The least amount of damage was observed for the excitation angle of 31° - 60°. The reason for these effects was that for the excitation angle of 0° - 30° and 61° - 90°, two or more building walls were perpendicular to the earthquake direction hence the building becomes vulnerable to toppling. Furthermore, houses that had weak points (windows and doors) exposed to the line of sight from the epicentre had reported more damages than houses that have no weak point exposed to the line of sight from the epicentre. Buildings that were completed with plaster were more resistant to earthquake damage than buildings that were un-plastered. The findings in this study can used be to establish fundamental building vulnerability properties for low-cost developments which will help to improve the construction of low-cost houses and reduce their vulnerability to earthquake damage and protect human life.
Seismic sources, seismotectonics and earthquake recurrence for the KZN coastal regions.
(2016) Singh, Mayshree.; Akombelwa, Mulemwa.; Maud, Rodney.
Historical earthquake information forms a critical dataset for seismotectonic investigations that can be used for seismic hazard investigations of hazardous and high rise structures and national seismic hazard maps. This study systematically interrogates historical earthquake data for the region from various sources in order to have a better understanding of the origins of the larger earthquakes. Several previously undocumented earthquakes were found that can supplement the national catalogue. Various sources are postulated as origins of these tremors namely local sources located in Mtubatuba and offshore sources like the Mozambique Channel. A seismotectonic model of the study region is also presented from an analysis of earthquake data, structural and kinematic systems. Geo-spatial data from geology, tectonics, regional geophysical anomalies, historical and instrumental seismicity and kinematics are considered. For what was once considered as a diffuse seismotectonic region with low levels of seismicity and where insufficient, uncertain and incomplete data existed – we now have datasets that are more complete and have higher levels of accuracy. Earthquake epicentres from both the historical and instrumental record as well as thermal spring localities correlate with old Jurassic faults. An assembly of a variety of datasets and studies are performed followed by a delineation of respective seismotectonic provinces. Earthquake recurrence parameters were assessed for the seismic provinces. Many of the provinces had insufficient seismic data to compute parameters. Improved seismic monitoring of the east coast region is required to better characterise the seismic risk. These results re-emphasize the need to better understand the coastal environment for seismotectonic characterization and to densify the seismic network towards the eastern coastline.
A static and dynamic finite element analysis of unreinforced masonry walls.
(2020) Moonsamy, Shaverndran.; Drosopoulos, Georgios A.; Singh, Mayshree.
This dissertation presents a numerical study of the structural behavior of unreinforced masonry walls. The study involves creating and testing computational models that simulate the behavior of unreinforced masonry walls under static and dynamic loading. The finite element method together with ANSYS software are used to create and analyze the numerical models. A standard 1-meter square, three-dimensional unreinforced masonry wall and a full-scale wall representing that of low-cost houses found across South Africa are developed and evaluated under general static structural loading conditions as well as dynamic loading conditions. A heterogenous finite element model is used so that each brick and layer of mortar are defined separately with a contact interface existing between the two layers. This approach allows for a detailed examination of the local failure behavior of masonry. The numerical models will be used to investigate structural parameters such as the stresses, deformations and the failure behavior of masonry walls under static and dynamic loads. The Drucker-Prager failure criteria is adopted to simulate the non-linear failure behavior of masonry. The dynamic analysis is conducted using both Modal and Response Spectrum analysis. The results from the study are compared with similar research using both numerical models and experimental tests.