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UBC Theses and Dissertations

Performance of un-retrofitted and retrofitted wood I-joists with flange notch or web hole Islam, Mohammad Shahidul


Composite wood I-joists have been used widely as floor and roof joists in the construction of commercial and residential buildings in Europe and North America since mid-1930s. These engineered timber I-joists are less expensive, lighter in weight, stronger, and more efficient compared to the solid sawn lumber beams. According to the Canadian Standards for Wood Design (CSA-O86) and manufacturer design guidelines, flange-cut on I-joists are strictly prohibited. However, notches in the top flange and openings in the web of I-joists are commonly made during construction to facilitate the electro-mechanical systems of a building. Due to these flange-notches and web-holes, the ultimate capacity and stiffness of the I-joist section get reduced significantly. This phenomenon will be more critical in the cases of web opening at shear span and flange notch at mid span. This may lead to the I-joist fail prematurely in shear or flexure in a brittle manner. The effect of flange-notches and web-holes on the strength properties (e.g. load carrying capacity, flexural strength, and shear strength) of timber I-joists need to be understood before reinforcing those deficient I-joists. The core objective of this thesis is to understand and predict the behavior of the I-joists having flange-notch and web-hole. Another objective of this study is to retrofit notches and web-holes with conventional and composite material, determine their performances, and provide predictive equations. For retrofitting purpose, Oriented Strand Board (OSB) collars and Glass Fibre Reinforced Polymer (GFRP) plates were used as reinforcing elements with different configurations. A total of 454 I-joists were tested with different notch and hole configurations. From the test results, it was observed that the presence of notch and hole reduced the capacity and stiffness of I-joists significantly. Findings also revealed that some retrofitting options can help improve the capacity as compared to the control I-joists. Finally, analytical models were developed to predict the behavior of flange notched and web holed I-joists and their retrofitted ones. Developed analytical models were validated with the experimental results and it was found that the analytical models can estimate the stiffness of those deficient and retrofitted I-joists with a fairly high accuracy.

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