UBC Theses and Dissertations

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UBC Theses and Dissertations

Age-dependent reliability analysis and development of a fuzzy based condition rating tool for timber utility poles Aslam, Hafiz Sohail Hasan


Timber is the most commonly used material for supporting utility power lines, with an estimated quantity of over 165 million across North America. Timber Poles provide a safe and cost effective mean to supply electricity and communication to vast majority of consumers, and are considered to be the most important asset by utility companies. Due to significantly large investment in timber poles across North America, there is need to investigate their structural reliability. Within the past few decades, different parts of the world have experienced significant climate changes. Specifically in North America, Hurricanes and strong winds have caused tremendous damage to infrastructure including Timber utility pole structures. Therefore, there is an urgent need to understand the performance of timber poles to mitigate damage during extreme climatic hazards. This research presents a fragility based methodology to assess and compare the vulnerability of timber poles exposed to wind hazards models for selected locations. Timber poles are designed as per both CSA 22.3 No.1 deterministic design wind loads and probabilistic wind loads. Wind hazard models for selected locations are developed using Extreme value analysis. Reliability of timber poles is determined through convolution of structural fragility models with the wind hazard models. Strength degradation with time due to decay was also taken into account for a holistic approach towards risk assessment of Timber poles. In addition to reliability analysis, a framework for development of a fuzzy logic based condition rating tool is also proposed in this research. Fuzzy synthetic evaluation technique, which is based on fuzzy logic theory has been utilized for the proposed framework. External decay, internal decay, wood pecker damage and mechanical damage were selected as performance indicators. A five tuple fuzzy linguistic evaluation set having levels of Very good, Good, Fair, Poor and Very Poor was used to assess the performance indicators. The proposed framework was validated through an illustrative example of ten timber poles. Analytical hierarchy process (AHP) was used to calculate weights for the four performance indicators. The proposed framework also provides the ability to prioritize timber poles according to their respective level of deterioration.

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Attribution-NonCommercial-NoDerivs 2.5 Canada