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UBC Theses and Dissertations

Vibration characteristics of single-family woodframe buildings Hadj Karim Kharrazi, Mehdi

Abstract

The proposed modifications in the forthcoming update of the National Building Code of Canada and insufficient information on the vibration behaviour of Canadian woodframe buildings prompted this investigation of the dynamic behaviour of woodframe houses in Canada. The objectives of this thesis are to gain a better understanding of the dynamic characteristics of single-family woodframe buildings in Canada, to conduct a comprehensive literature study on previous research, to assess whether or not ambient vibration testing can be used effectively for determining the vibration characteristics of woodframe houses and to investigate the use of joint time-frequency technique in the vibration studies of woodframe houses. A variety of full-scale dynamic tests, such as shake table earthquake simulation, ambient and forced vibration tests, were conducted at the University of British Columbia on single-family low-rise woodframe houses with the aim to study the dynamic behaviour of this type of structure. A number of field tests were conducted to collect complementary data for existing timber buildings. The vibration data was analyzed by different analysis methodologies. To study the vibration behaviour of woodframe houses before and after earthquake simulations, time and frequency domain analysis methods, such as frequency domain decomposition and stochastic subspace iteration, were employed. To investigate the behaviour throughout the earthquake simulation, joint time- frequency analyses were performed. Among the analyses performed the joint time-frequency analysis is a very powerful tool, which not only provides insight into dynamic characteristics of structures that are not available through frequency domain alone, but also can explain irregular shifts in frequency and verify the results from other analyses. The investigation of vibration characteristics of woodframe houses provided a good understanding of how the natural frequency of the structure changes and how this change is related to the amount of damage observed during each test. The fundamental periods determined from the conducted experiments were in the range of 0.3 to 0.6 seconds and corresponding damping ratios between 3.6 to 16 percent. These periods are significantly longer than the periods suggested by the code formulae. For dynamic testing of buildings the ambient vibration testing method is being recommended, since it is a non-destructive and relatively inexpensive testing method. Frequency results of ambient vibration testing method are found to be typically higher than those obtained from forced vibration testing. Since the latter is considered to be closest to the real frequencies of houses subjected to strong motion, a correlation was done to correct the ambient vibration results.

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