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    Author(s): D. F. Windorski; L. A. Soltis; R. J. Ross
    Source: (Research paper FPL ; RP-562):9 p. : ill. ; 28 cm.
    Publication Series: Research Paper (RP)
    Station: Forest Products Laboratory
    PDF: View PDF  (274 KB)


    Bolted connections often fail by a shear plug or a splitting beneath the bolt caused by tension perpendicular-to-grain stresses as the bolt wedges its way through the wood. Preventing this type of failure would enhance the capacity and reliability of the bolted connection, thus increasing the overall integrity of a timber structure and enabling wood to compete favorably with other engineering materials. This research investigated the use of fiberglass reinforcement to enhance the load-carrying capacity of bolted wood connections. A series of specimens were prepared from standard 38- by 89-mm (nominal 2- by 4-in.) lumber from the Spruce1Pine1Fir lumber grouping. Matched specimens were reinforced with one, two, or three layers of bi-directional fiberglass cloth. Resulting test specimens were configured as a connection that was in accordance with current design specifications. A total of 80 single-bolt, double-shear connections were tested; 40 parallel to grain and 40 perpendicular to grain. Results indicate that connection strength increases as the layers of fiberglass reinforcement increase. The largest increase occurred when adding the first layer to the nonreinforced connection. Additional layers increased strength at a decreasing rate. The ultimate strength of a three-layer reinforced connection was 33 percent greater than the nonreinforced connection for parallel-to grain loading and more than 100 percent for perpendicular-to-grain loading. More importantly for parallel-to-grain loading, the reinforcement changed the mode of failure from an abrupt, catastrophic type associated with tension perpendicular-to-grain stresses to a ductile type associated with bearing stress.

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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Windorski, D. F.; Soltis, L. A.; Ross, R. J. Feasibility of fiberglass-reinforced bolted wood connections. (Research paper FPL ; RP-562):9 p. : ill. ; 28 cm.


    Bolted joints, Timber connectors, Fiberglass

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