Effect of Wind Induced Loads on Roof Overhangs and Soffits for Low Rise Buildings

Roof overhangs are prone to wind damage as they are subjected to wind load at both the upper and bottom surfaces. Wind standards, like ASCE 7-22, assume that the pressure at the bottom covering of the roof overhang is the same as the external pressure coefficient on the adjacent wall surface. A large-scale experimental campaign was carried out at the Wall of Wind (WOW) Research Experimental Facility to investigate the validity and possible limitations of such assumptions. The experimental setup considered eight 1:10 scaled models of a low-rise hip roof building of various geometrical parameters such as roof slope, roof overhang width, along with plethora of wind directions.

The study investigated the pressure and correlation coefficients between soffits and underneath walls to quantify the effect of overhang width. The experimental results confirmed that, for all configurations, soffit positive pressure coefficients may be assumed to be equal to the adjacent wall external pressure, as stated by ASCE7-22, while this might not be applicable for negative pressure coefficients. In addition, peak pressures on both the upper and lower surfaces were measured to calculate the simultaneous net pressure coefficients along the overhangs. Area-averaged pressure analysis was carried out to investigate the pressure gradients on single or groups of taps on the overhangs, soffits, and walls. These area averaged GC_p were compared to previous and current versions of wind standards to evaluate their adequacy. The findings revealed that the provisions’ design guidelines are less conservative for some roofing zones and wall zones, which justified the need for a codification study that will provide recommended design guidelines for overhangs and adjacent walls. The study provided new codified design guidelines, which are formed based on statistical determination rather than the enveloped procedures as commonly used. In addition, an empirical equation has been developed that correlated the relation between wall pressure coefficient and soffit pressure coefficient for different overhangs widths and different wind direction. Finally, different machine learning models were developed using the experimental data to predict the pressure coefficients among the surfaces of low-rise buildings.