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Type: Theses
Title: Improved seismic analysis of unreinforced masonry buildings with flexible diaphragms
Author: Nakamura, Yasuto
Issue Date: 2016
School/Discipline: School of Civil, Environmental and Mining Engineering
Abstract: The presence of flexible timber diaphragms in many existing unreinforced masonry buildings poses a significant challenge for the assessment of their seismic vulnerability. When diaphragms are flexible, different parts of a structure can interact with each other dynamically, in a way not typically encountered in modern structures with rigid diaphragms. As a result, the seismic analysis methods developed for buildings with rigid diaphragms, as well as our basic understanding of the dynamic behaviours of buildings under earthquake excitations, cannot be applied directly for buildings with flexible diaphragms. This thesis addresses two issues that require immediate attention in improving the seismic analysis of unreinforced masonry buildings with flexible diaphragms, namely (1) to enhance our understanding of the dynamic response characteristics of low-rise buildings with flexible diaphragms, and (2) to investigate the applicability of an array of existing analysis methods developed for rigid diaphragm structures. The research work presented in this thesis begins with a basic analysis of the elastic behaviour of symmetric buildings with flexible diaphragms. Through an analytical study of their modal properties, it is shown that at least two dominant modes are present in the dynamic responses of buildings with flexible diaphragms. Using the results of modal analysis, an improvement to the linear static analysis method is proposed. The inelastic behaviours of symmetric- and asymmetric-plan building systems with flexible diaphragms are then investigated through a systematic parametric analysis. It is shown that the effect of diaphragm flexibility varies depending on the level of stiffness- and strength-eccentricity of the system. A general diaphragm classification is developed to explain the influence of diaphragm flexibility on the global building response. A simple numerical modelling technique to incorporate the dynamic behaviours of flexible diaphragms in a three-dimensional equivalent frame modelling approach is also investigated, and validated against shake table test data. Finally, the applicability of nonlinear static procedures utilising single-mode, multi-mode and adaptive pushover analyses are investigated. Practical recommendations are provided for the use of various pushover analysis methods for unreinforced masonry buildings with flexible diaphragms.
Advisor: Griffith, Michael Craig
Sheikh, Abdul Hamid
Magenes, Guido
Dissertation Note: Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2016.
Keywords: seismic analysis
unreinforced masonry
flexible diaphragms
nonlinear static
Research by Publication
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
DOI: 10.4225/55/5a20e650ea4e9
Appears in Collections:Research Theses

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