Thesis Format
Monograph
Degree
Master of Engineering Science
Program
Civil and Environmental Engineering
Supervisor
Wang Jin
Abstract
Accurately predicting the wind loads on components and claddings (C&C) on roofs are important to enhance the resilience of buildings. Wind loads on structures can be estimated by mainly two methods in the prevalent building codes. The first method is to provide peak pressure coefficients which have been utilized by several design codes to provide wind loads for C&C, such as ASCE 7-22 and NBCC 2020. The second approach relies on the gust effect factor. This method has been widely adopted for evaluating wind loads for along-wind response of high-rise structures by considering both background response due to upstream turbulence and resonance response due to structural dynamics. However, NBCC 2020 also recommends adopting a gust effect factor of 2.5 for C&C of buildings greater than 20 m referenced to mean wind speed. In addition, EN1991-1-4 suggests using a constant structural factor ( ) – analogous to the gust effect factor - of 1.0 for roof elements and claddings.
The present study examines the gust effect factors for local zones of low-sloped roofs of low-rise buildings, by employing the wind tunnel data from NIST database. The statistical parameters of wind pressures, such as mean, standard deviation, kurtosis, skewness and peak factor are particularly examined to demonstrate the statistical characteristics of wind pressures on local zones of roofs.
This study concludes that the measured gust effect factors particularly for small effective wind areas, significantly exceed the prescribed values of 0.85 for main wind force resisting system in ASCE 7-22, surpass the provisions in NBCC for C&C of buildings exceeding 20 m, and exceed the value of 1.0 for C&C of low-rise buildings in EN1991-1-4. This discrepancy is attributed to the negligible effects of body-generated turbulence in building codes, such as separation bubble and conical vortices. Additionally, the highly non-Gaussian nature of wind pressures is observed for small effective wind area due to the body-generated turbulence. These findings suggest that when employing the gust effect factor method to predict wind loads for C&C, it is important to take the body-generated turbulence into account.
Summary for Lay Audience
Accurately predicting the wind loads on components and cladding (C&C) on roofs are important to enhance the resilience of buildings. Wind loads on structures can be estimated by mainly two methods in the prevalent building codes. The first method is to provide peak pressure coefficients which have been utilized by several design codes to provide wind loads for C&C, such as ASCE 7-22 and NBCC 2020. The second approach relies on the gust effect factor. This method has been widely adopted for evaluating wind loads for along-wind response of high-rises structures by considering both background response due to upstream turbulence and resonance response due to structural dynamics. However, NBCC 2020 also recommends adopting a gust effect factor (gust response factor) of 2.5 for C&C of buildings greater than 20m referenced to mean wind speed. In addition, Euro-Code suggests using a constant structural factor (CsCd) – analogous to the gust effect factor - of 1.0 for roof elements and claddings.
The present study examines the gust effect factors for local zones of low-sloped roofs of low-rise buildings, by employing the wind tunnel data from NIST database. The statistical parameters of wind pressures, such as mean, standard deviation, kurtosis, skewness and peak factor are particularly examined to demonstrate the statistical characteristics of wind pressures on local zones of roofs.
This study concludes that the measured gust effect factors particularly for small effective wind areas, significantly exceed the prescribed values of 0.85 for main wind force resisting system in ASCE 7-22, surpass the provisions in NBCC for C&C of buildings exceeding 20m, and exceed the value of 1.0 for C&C of low-rise buildings in Euro-Code. This discrepancy is attributed to the ignorance of body-generated turbulence in building codes, such as separation bubble and conical vortices. Additionally, the highly non-Gaussian nature of wind pressures is observed for small effective wind area due to the body-generated turbulence. These findings suggest that when employing the gust effect factor method to predict wind loads for C&C, it is important to take the body-generated turbulence into account.
Recommended Citation
Mokani, Jigar, "Gust effect factors of components and cladding wind loads for low-slope roofs on low-rise buildings" (2024). Electronic Thesis and Dissertation Repository. 9915.
https://ir.lib.uwo.ca/etd/9915