Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Collaborative Specialization

Environment and Sustainability

Supervisor

Kopp, Gregory A.

2nd Supervisor

Wang, Jin

Co-Supervisor

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.

Summary for Lay Audience

Standing seam metal roofs (SSMR) are a metal roofing system used on low-rise buildings in North America. They are prefabricated, manufactured systems that haven proven to be water-tight and unaffected by extreme temperatures. The SSMR panels are secured to the roof structure using fasteners called clips. Generic prescribed building codes, such as ASCE 7, do not consider the details of load sharing among the panels, clips, and roof structure in these manufactured SSMR systems. However, it is worthwhile to study the load sharing in order to optimize the design. This idea forms the basis of the current research.

In this thesis, an analysis of wind tunnel data was used to predict wind loads on a building with standing seam metal roof. The wind loads of three prediction models were compared. The first model used the simple, standardized approach found in the ASCE building code. The second model used a hybrid of the building code and a verified analytical model. The third model, thought to be most realistic, used just the verified analytical model. A comparison of the three models showed that while the building code is a good estimator of wind loads, it is very conservative and overestimated the loads when compared to the analytical model. Some recommendations to improve the building code were presented.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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