title: Vibration analysis of cracked structures as a roving body passes a crack using the Rayleigh-Ritz Method

authors: Ilanko, Sinniah

subjects: cracked plate

abstract: The natural frequencies of a cracked plate with a roving mass were computed using the Rayleigh-Ritz Method for various sets of boundary condition. The obtained frequencies exhibit a sudden shift as a roving body crosses a crack. If the crack is only partial and continuity of translation is maintained, then the frequency shift occurs only when the body possesses a rotary inertia. If the crack is a complete one (through thickness) which permits differential translation to occur on either side of the crack, a particle having mass only (translatory inertia) is sufficient to cause a sudden shift. There is no need for a rotary inertia. This is potentially useful in detecting cracks in structures, as it is possible to track the changes in the natural frequencies of a structure as a test body such as a vehicle on a bridge moves and identify points where sudden frequency changes occur.

text: Vibration analysis of cracked structures as a roving body passes a crack using the Rayleigh-Ritz Method The natural frequencies of a cracked plate with a roving mass were computed using the Rayleigh-Ritz Method for various sets of boundary condition. The obtained frequencies exhibit a sudden shift as a roving body crosses a crack. If the crack is only partial and continuity of translation is maintained, then the frequency shift occurs only when the body possesses a rotary inertia. If the crack is a complete one (through thickness) which permits differential translation to occur on either side of the crack, a particle having mass only (translatory inertia) is sufficient to cause a sudden shift. There is no need for a rotary inertia. This is potentially useful in detecting cracks in structures, as it is possible to track the changes in the natural frequencies of a structure as a test body such as a vehicle on a bridge moves and identify points where sudden frequency changes occur.

year: 2018

title: Seismic isolation of buildings for vertical earthquake excitations

authors: Eskandary Malayery, Fatemeh (Elena)

subjects: Vertical earthquake excitations

abstract: This thesis concerns a seismic isolation mechanism for vertical component of earthquake. The vertical component of earthquake can be stronger and more destructive than the horizontal component in near-fault areas, for instance, Christchurch earthquake in New Zealand in 2011 or Bam earthquake in Iran in 2003. Therefore, this needs to be considered in designing and retrofitting structures to reduce damage to buildings and human lives. This thesis develops a numerical and experimental model of the seismic isolation based on quasi-zero-stiffness-system (QZSS) and high-static-low-dynamic-stiffness-system (HSLDSS) concepts. The results suggest the HSLDSS considered could be a practical solution for decreasing the response of the system to the vertical component of earthquake. 
Analytical and numerical models of a HSLDSS and a QZSS are developed. The behaviour of the mechanism subjected to static loading as well as time harmonic excitation is investigated. The harmonic balance method and the direct numerical integration method are employed to solve the equations of motion for the system. In addition, the effect of each design parameter is studied when the structure is subjected to static and harmonic excitation loadings. The impact of uncertainties in the payload as well as mistuning in the system are addressed. It is seen that the QZSS is very sensitive to any changes in payload or mistuning, while HSLDSS is unaffected by slight changes to load or initial geometry. In addition, the effects of linear and nonlinear friction elements in the model are investigated. It is seen that friction decreases the performance of the system and needs to be minimised. The response of the HSLDSS mechanism subjected to 23 near-fault earthquake ground motions is presented and discussed. Moreover, the mechanism design variables (initial geometry, static loading, stiffness of the springs) which minimise the peak acceleration, RMS response, and peak displacement are investigated. The behaviour of the linear, QZSS and HSLDSS are compared to show which case is more efficient. Although QZSS is the most effective, it is sensitive to any changes in the payload and mistuning. On the other hand, HSLDSS is less sensitive to those changes while retaining good performance and reducing the peak and RMS acceleration significantly.
The experimental results are presented, the measurements taken compared to the numerical results and show good agreement. The results show significant reduction in peak and RMS acceleration for most input signals. However, for Chichi earthquake, the reverse is true. This is explained by the frequency content of the signal which has high power in the frequency range below 1 Hz. The friction force is estimated from three techniques: measurement from static tests, measurement from harmonic excitation and from the least squared error between numerical and experimental results. Among these three, the last method is found to give good agreement between numerical and experimental results for all earthquake inputs.
The developed mechanism is shown to be efficient in isolating structures with one support subjected to earthquake inputs. It reduces the force transmission from the base to structures during earthquakes.

text: Seismic isolation of buildings for vertical earthquake excitations This thesis concerns a seismic isolation mechanism for vertical component of earthquake. The vertical component of earthquake can be stronger and more destructive than the horizontal component in near-fault areas, for instance, Christchurch earthquake in New Zealand in 2011 or Bam earthquake in Iran in 2003. Therefore, this needs to be considered in designing and retrofitting structures to reduce damage to buildings and human lives. This thesis develops a numerical and experimental model of the seismic isolation based on quasi-zero-stiffness-system (QZSS) and high-static-low-dynamic-stiffness-system (HSLDSS) concepts. The results suggest the HSLDSS considered could be a practical solution for decreasing the response of the system to the vertical component of earthquake. 
Analytical and numerical models of a HSLDSS and a QZSS are developed. The behaviour of the mechanism subjected to static loading as well as time harmonic excitation is investigated. The harmonic balance method and the direct numerical integration method are employed to solve the equations of motion for the system. In addition, the effect of each design parameter is studied when the structure is subjected to static and harmonic excitation loadings. The impact of uncertainties in the payload as well as mistuning in the system are addressed. It is seen that the QZSS is very sensitive to any changes in payload or mistuning, while HSLDSS is unaffected by slight changes to load or initial geometry. In addition, the effects of linear and nonlinear friction elements in the model are investigated. It is seen that friction decreases the performance of the system and needs to be minimised. The response of the HSLDSS mechanism subjected to 23 near-fault earthquake ground motions is presented and discussed. Moreover, the mechanism design variables (initial geometry, static loading, stiffness of the springs) which minimise the peak acceleration, RMS response, and peak displacement are investigated. The behaviour of the linear, QZSS and HSLDSS are compared to show which case is more efficient. Although QZSS is the most effective, it is sensitive to any changes in the payload and mistuning. On the other hand, HSLDSS is less sensitive to those changes while retaining good performance and reducing the peak and RMS acceleration significantly.
The experimental results are presented, the measurements taken compared to the numerical results and show good agreement. The results show significant reduction in peak and RMS acceleration for most input signals. However, for Chichi earthquake, the reverse is true. This is explained by the frequency content of the signal which has high power in the frequency range below 1 Hz. The friction force is estimated from three techniques: measurement from static tests, measurement from harmonic excitation and from the least squared error between numerical and experimental results. Among these three, the last method is found to give good agreement between numerical and experimental results for all earthquake inputs.
The developed mechanism is shown to be efficient in isolating structures with one support subjected to earthquake inputs. It reduces the force transmission from the base to structures during earthquakes.

year: 2022

title: Rebel discourses: Colonial violence, Pai Marire resistance and land allocation at Tauranga

authors: Kahotea, Des Tatana

abstract: This thesis is a study of resistance and power in a colonial situation, based on the ethnography of a confiscated-land claim of three hapu who had been Kingitanga supporters and Pai Marire adherents in the 19th century. It draws on archival material and insider ethnography and is arranged into four parts. The first part looks at the relationship between anthropology and colonialism, particularly the role of Sir George Grey, a Governor who used anthropological knowledge to facilitate colonial domination of Maori. Grey instigated the establishment of learned societies which introduced the use of ethnology and anthropology to study Maori. This led to the development of colonial anthropology and its emphasis on salvage anthropology in the late nineteenth century, which in turn gave rise to an intellectual tradition of Maori anthropology. The first proponents of Maori anthropology, Te Rangihiroa and Apirana Ngata, emphasised the role of anthropology for cultural recovery and 'insider' ethnographer. The second part examines the Kingitanga and Pai Marire political and religious expressions of resistance. Political resistance to colonialism was met by legislation by the settler colonial government to punish 'rebellion', a system of collaboration or cultivation of 'loyalty' amongst 'friendly' Maori, and other policies directed at suppressing indigenous expressions of rebel consciousness. This programme had a major bearing on the ongoing existence of these hapu into the twentieth century. Pai Marire was a rebel religious phenomenon that became the object of a campaign of coercion, surveillance, and violence by the settler colonial government. The adherents were subject to policies of exclusion from the redistribution and allocation of confiscated land by local government officials and civil commissioners. The government supported, instead, the land claims of 'friendly' and 'surrendered rebel' chiefs. The third part is hapu ethnography. Key transformations in the nineteenth and twentieth centuries related to changing political and kin alliances for one hapu, Ngati Kahu, while another hapu, Ngati Pango which was involved with Pai Marire, suffered from claims on their traditional lands leading to the undermining of its identity and existence as a socially operating hapu. The fourth part uses historical and ethnographic fragments to consider what Pai Marire meant to its adherents. The colonial construct of Pai Marire and Hauhau was forms of savagery and a mix of Christian syncretism, an image that has little changed from the nineteenth century.

text: Rebel discourses: Colonial violence, Pai Marire resistance and land allocation at Tauranga This thesis is a study of resistance and power in a colonial situation, based on the ethnography of a confiscated-land claim of three hapu who had been Kingitanga supporters and Pai Marire adherents in the 19th century. It draws on archival material and insider ethnography and is arranged into four parts. The first part looks at the relationship between anthropology and colonialism, particularly the role of Sir George Grey, a Governor who used anthropological knowledge to facilitate colonial domination of Maori. Grey instigated the establishment of learned societies which introduced the use of ethnology and anthropology to study Maori. This led to the development of colonial anthropology and its emphasis on salvage anthropology in the late nineteenth century, which in turn gave rise to an intellectual tradition of Maori anthropology. The first proponents of Maori anthropology, Te Rangihiroa and Apirana Ngata, emphasised the role of anthropology for cultural recovery and 'insider' ethnographer. The second part examines the Kingitanga and Pai Marire political and religious expressions of resistance. Political resistance to colonialism was met by legislation by the settler colonial government to punish 'rebellion', a system of collaboration or cultivation of 'loyalty' amongst 'friendly' Maori, and other policies directed at suppressing indigenous expressions of rebel consciousness. This programme had a major bearing on the ongoing existence of these hapu into the twentieth century. Pai Marire was a rebel religious phenomenon that became the object of a campaign of coercion, surveillance, and violence by the settler colonial government. The adherents were subject to policies of exclusion from the redistribution and allocation of confiscated land by local government officials and civil commissioners. The government supported, instead, the land claims of 'friendly' and 'surrendered rebel' chiefs. The third part is hapu ethnography. Key transformations in the nineteenth and twentieth centuries related to changing political and kin alliances for one hapu, Ngati Kahu, while another hapu, Ngati Pango which was involved with Pai Marire, suffered from claims on their traditional lands leading to the undermining of its identity and existence as a socially operating hapu. The fourth part uses historical and ethnographic fragments to consider what Pai Marire meant to its adherents. The colonial construct of Pai Marire and Hauhau was forms of savagery and a mix of Christian syncretism, an image that has little changed from the nineteenth century.

year: 2005