Gust Effect Factors of Components and Cladding Wind Loads for Low-Slope Roofs on Low-Rise Buildings

Building Components and Cladding (C&C) are important to the performance of these structures during extreme windstorms. Post-damage surveys have revealed that low-rise building roofs are particularly vulnerable to windstorms. Therefore, accurate prediction of wind loads on C&C of low-rise building roofs is essential to increase building resilience and mitigate the risks of damage to these structures. The gust effect factor method, developed based on Quasi-steady Theory (QST), has been widely used to determine design wind loads in many codes of practice, primarily for the along-wind overall response of high-rise buildings. The present study examines the applicability of gust effect factor method for predicting C&C wind loads of low-rise building roofs. The flow fields over roofs are relatively complex, with many types of flow patterns and vortical structures that might alter the Gaussian statistics. One building configuration from the NIST database obtained from Boundary-Layer Wind Tunnel II at the University of Western Ontario was used to conduct the analysis. The skewness and kurtosis of C&C wind loads were examined first to demonstrate the statistical distributions of C&C wind load on low-rise building roofs. In addition, the gust effect factors, which relate the wind load fluctuations to upstream wind turbulence, were presented. The results show that the gust effect factors of wind loads on roof corner zones extend the recommended value of 0.85 in ASCE 7-22 due to the complicated conical vortices. Furthermore, it is observed that the gust effect factors vary with effective wind area in the same way as peak wind pressures suggested in ASCE 7-22 and NBCC 2020. This study highlights that the gust effect factor method can be reasonable for predicting C&C wind loads for large effective wind area. However, it may underestimate peak wind loads due to the neglect of body-generated turbulence.