Wind-Uplift Capacity of Residential Wood Roof-Sheathing Panels Retrofitted with Insulating Foam Adhesive
Publication: Journal of Architectural Engineering
Volume 17, Issue 4
Abstract
This research evaluated and compared the wind-uplift capacity of wood roof-sheathing panels fabricated by using nails with retrofitted roof panels made with nails and closed-cell sprayed polyurethane foam (ccSPF) adhesive. In hurricane-prone areas, structural retrofits of light-framed wood roof structures are needed to mitigate wind damage to existing residential roof structures because the majority of these have inadequate design strength to resist hurricane-force winds. A steel pressure chamber connected to a pressure loading actuator was used to conduct uplift pressure tests on 186 roof panels. The panels were fabricated using 11.1 mm (7/16 in.) thick oriented strand board sheathing fastened to nominal 51 by 102 mm (2 by 4 in.) southern yellow pine framing members spaced 610 mm (24 in.) apart. There were 123 panels tested in typical as-built conditions, and 63 panels tested after they were retrofitted with ccSPF. The parametric study determined the effect of several factors on wind-uplift failure pressure: (1) three nail types, (2) two nail spacings, and (3) three retrofit methods using ccSPF. The hypothesis tested was that ccSPF (traditionally used as wall and roof insulation in houses) could also act as a structural adhesive to increase the wind resistance of existing roofs. Standardized tests do not currently exist for wood roof panels, and so a uniform, static pressure-test protocol was developed on the basis of the ASTM E330, Method B Test Procedure. The results showed that ccSPF retrofits increase the wind-uplift capacity of the pre-1994 code-minimum wood roof panels by as much as 250–300%. This finding is important because it could provide a means to improve the wind resistance of these older roof designs, which may still account for more than 60% of the existing residential inventory. The distributions of roof-failure capacities of as-built and retrofitted roof panels are presented, and statistical parameters are presented for use in developing performance-based design criteria. The documentation and approach is presented as a model test protocol as the basis of a standardized wind-uplift test method for wood roof-sheathing panels.
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Acknowledgments
The writers are appreciative of the financial support provided by corporate sponsors, Honeywell Specialty Materials, Huntsman Polyurethanes, and NCFI Polyurethanes. The research was supported in part by the State of Florida’s Department of Community Affairs through a research grant no. UNSPECIFIED08RC-B5-13-00-05-162. Technical advice was provided by Dr. Richard Duncan, Technical Director, Spray Polyurethane Foam Alliance; Dr. Jinhuang Wu of Huntsman; and Mr. Jason Hoerter of NCFI Polyurethanes. The first writer gratefully acknowledges financial support provided by the University of Florida Alumni Fellowship.
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Information
Published In
Journal of Architectural Engineering
Volume 17 • Issue 4 • December 2011
Pages: 144 - 154
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Mar 23, 2010
Accepted: Nov 3, 2010
Published online: Nov 5, 2010
Published in print: Dec 1, 2011
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