Wind Loading Analysis of Standing Seam Metal Roofs on Low-Rise Buildings
Abstract
Standing seam metal roofs (SSMR) are a roofing system made up of prefabricated panels secured to the underlying structural purlins using concealed clips. The present study sought to develop a simplified code-approach for evaluating SSMRs. A model of the wind field and wind loads was validated using wind tunnel data from Arif (2017), influence functions and clip layout from Xia (2022), and compared the results to ASCE 7-22. Worst case enveloped GCp were compared by area for three different models: (i) ASCE Method, which gives wind loads based on bare deck roof, (ii) Clip Tributary Area (CTA) Method, which assumed the SSMR configuration and the clip geometric tributary area to predict clip loads, and (iii) Influence Function (IF) Method, which assumed the SSMR configuration and influence functions to determine clip loads. A load adjustment factor was calculated to compare the pressure coefficients between the ASCE Method and IF Method, this quantified the difference between the code model and a model that considered load sharing. The ASCE Method produced results that followed normal building aerodynamics, showing as effective wind area size increases the peak pressure decreases. The CTA Method significantly overestimated the ridge clip and eave clip loads compared to the IF Method. Typically, a roof on a low-rise building experiences the highest suction at the corners and edges. These areas coincide with the clips that have the greatest load sharing, and thus, the peak suction was reduced in these regions. Predicted clip loads from the CTA Method and IF Method did not show correlation with area. The ASCE Method was compared to the IF Method and the proposed load adjustment factor was presented for each ASCE zone and for inner clips and ridge and eave clips separately. The load adjustment factor indicates the ASCE Method is generally 8-59% conservative in its predictions.