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Effectiveness of roof overhang on mid-rise buildings: field measurements and improved assessment based on ISO standard

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Effectiveness of roof overhang on mid-rise buildings: field measurements and improved assessment based on ISO standard

Souri, Firouzeh (2018) Effectiveness of roof overhang on mid-rise buildings: field measurements and improved assessment based on ISO standard. Masters thesis, Concordia University.

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Abstract

Wind-driven rain (WDR), as one of the most important boundary conditions, not only influences hydrothermal performance and material durability of the building enclosures but also its penetration through building’s assemblies may lead to different types of moisture related failures. In recently completed studies, a unique set of high resolution data through field measurements under real life conditions is provided by monitoring three mid-rise buildings in three Canadian cities (Vancouver, Montreal and Fredericton). All test buildings are instrumented with weather stations and driving rain gauges for wind driven-rain measurements on building’s façade. In addition, Vancouver building is equipped with a retractable overhang extendable to 1.2 m, partially covering east and north facades. The previous studies have shown that estimation of wind driven-rain by applying semi-empirical methods, is generally subjected to overestimation in comparison with measured wind driven-rain. The accuracy of ISO method can be improved significantly by using more accurate wall factors calculated based on onsite measurements. Moreover, the effectiveness of roof overhang in reduction of wind driven-rain deposition on a mid-rise building have been studied and quantified for 0.6 m and 1.2 m overhang.
As a follow-up, this thesis conducted further analysis and tests with the purpose of improving wind-driven rain assessment based on ISO standard by achieving three main objectives: first, to develop a correlation between overhang width and amount of wind driven-rain load reduction on the facade under it, with respect to wind characteristics; second, to develop a methodology to generalize the proposed reduction coefficient for similar mid-rise building geometry being protected by roof overhang; and finally, to carry out further investigation of error sources for the discrepancy between measurements and calculated wall indices, therefore, improving the accuracy of ISO semi-empirical model.
To fulfill these objectives, established methodology in previous studies such as the similarity and symmetry approach is followed by analyzing additional available data. Proposed wind driven-rain reduction coefficient is calculated based on the weighted-effectiveness methodology. Validation of generalizing proposed reduction coefficients for similar mid-rise building geometry is conducted by comparison of wind velocity near the upstream façade of study buildings model, with and without overhang, in Concordia’s atmospheric boundary layer wind tunnel.
In addition, more detailed analysis regarding the effect of time resolution and data conversion on the accuracy of ISO model is provided. The detailed study of meteorological wind data, registered onsite and reported by the weather station, confirms that wind characteristic changes from point to point could be stated as other sources of discrepancies.

Divisions:Concordia University > Gina Cody School of Engineering and Computer Science > Building, Civil and Environmental Engineering
Item Type:Thesis (Masters)
Authors:Souri, Firouzeh
Institution:Concordia University
Degree Name:M.A. Sc.
Program:Building Engineering
Date:4 September 2018
Thesis Supervisor(s):Ge, Hua and Stathopoulos, Theodore
ID Code:984372
Deposited By: Firouzeh Souri
Deposited On:16 Nov 2018 15:51
Last Modified:16 Nov 2018 15:51
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