Date of Award

2002

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Department

Civil Engineering

Advisor

William G. Davids

Second Committee Member

Habib J. Dagher

Third Committee Member

Douglas J. Gardner

Abstract

The resistance of conventionally constructed wood-framed structures to extreme events such as earthquakes and hurricanes depends in large part on the strength and energy absorption characteristics of the shear walls. These shear walls are often sheathed with oriented strand board (OSB) panels, and their performance is primarily a function of the nailed sheathing-to-framing connections at the panel edges. A new sheathing panel called Advanced OSB (AOSB) has been developed at the University of Maine's Advanced Engineered Wood Composites Center. The AOSB panel integrates glass fiberreinforced polymer (GFRP) reinforcing into regions of the OSB panel that have been observed to fail under hurricane or earthquake loading. Structural testing of both single nail connections and full scale shear walls have shown that AOSB has great potential for increasing the energy dissipation capacity and lateral load resistance of wood-framed structures subjected to extreme wind and seismic events. The GFRP reinforcement increases the lateral resistance of conventional woodframed shear walls by improving the strength and ductility of the sheathing-to-framing nail connections. AOSB changes the primary failure mode of the sheathing-to-framing nails from a shear out type failure where the nail tears through the edge of OSB to a more ductile and energy absorbent failure mode where the nails exhibit double curvature and are withdrawn from the framing. The results of monotonic tests on single-nail connections show that the strength of an individual nailed connection can be increased by about 39% and the energy dissipation capacity can be more than quadrupled through the use of AOSB. Results of cyclic connection tests with AOSB compared to those of plain OSB specimens indicate that the AOSB panels are less sensitive to damage accumulation from repeated load cycling. Standard size (8ftx8ft) shear wall specimens sheathed with AOSB panels tested in accordance with ASTM E564 were able to maintain at least 80% of their peak load up to a drift of approximately 5.5 in. compared to approximately 4.0 in. for walls sheathed with conventional OSB. When tested cyclically, the conventional OSB sheathing panels were extensively damaged due to edge tear of nails, however very little damage of the AOSB panels was observed. This, coupled with the fact that failure of the AOSB walls was driven primarily by nail fatigue and nail pullout, indicates that AOSB sheathing panels provide as much capacity as the framing and the nails will allow. A finite element model of two panel AOSB shear walls was developed using the commercial software ANSYS. The primary goal of this model was to capture the complex load sharing behavior of the AOSB shear wall system to aid future design improvements of AOSB shear wall systems. The model results are in good agreement with the results of the static wall tests. AOSB panels appear to have great potential for increasing the energy dissipation capacity and lateral load resistance of wood-framed structures subjected to extreme wind and seismic events. Ongoing research efforts at the University of Maine will help to further refine and optimize the AOSB technology.

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