STRUCTURAL BEHAVIOR OF WOOD I-JOIST/OSB ROOF PANEL ASSEMBLIES

STRUCTURAL BEHAVIOR OF WOOD I-JOIST/OSB ROOF PANEL ASSEMBLIES

By Derek Rancourt

Thesis Advisor: Dr. William G. Davids

A Lay Abstract of the Thesis Presented

in Partial Fulfillment of the Requirements for the

Degree of Master of Science

(in Civil & Environmental Engineering)

August, 2010

Wood I-joist roof panels were developed and tested at The University of Maine AEWC Advanced Structures & Composites Center.  The prefabricated panels incorporate framing, sheathing, insulation and ventilation into a single product to be used in light-frame construction applications.  Panels are manufactured in a controlled environment and shipped to the job site, reducing site assembly time and labor costs.  Once on-site, the four-foot wide panels are placed by small crane and interlock on the roof by an overlap of sheathing and a single row of nails or screws along the panel length.  The panels consist of wood I-joist framing members and oriented strand board (OSB) sheathing on top and bottom flanges.

Short-term bend tests were conducted on twenty panels with lengths of 16-ft and 24‑ft.  Results were positive, showing increases up to 125% in strength and 95% in stiffness when compared to test results of individual framing members.  In 90% of bare I-joist test specimens, failure occurred at manufactured finger-joints in the bottom, tension flange.  This failure mode only occurred in 25% of full-scale roof panel specimens; 75% failed in shear in the OSB web, demonstrating significant composite action. 

Creep-flexure tests were conducted to assess the long-term structural performance of panels.  Results indicated that creep-rupture may be critical in panel design.  In conjunction with panel tests, material-level tests of the constituent OSB and I-joists provided data for a strength- and stiffness-prediction model.  Transformed section analyses were used as a simplified method to derive panel load-span tables which illustrate the potential for future roof designs.