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Out-of-plane capacity of truss connector plates
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Truss connector plates have become very cost effective for residential and light commercial roof and floor trusses due to the increased automation of the wood truss industry and new design and fabrication techniques. Truss connector plates are proprietary products, and are characterized with three basic properties: tension, shear, and lateral-resistance capacity. These properties are evaluated in accordance with the guidelines of the TPI Standard ANSI/TPI 1-1995 (13) in the United States, and CSA Standard S347-M1980 (2) in Canada. The tension and shear capacities are generally expressed per unit plate length for specific orientations of the plate to the applied force. The lateral resistance capacities are generally expressed per unit plate-wood contact area for specific plate and wood grain orientations with respect to the applied force. The width of a plate at a joint must be adequate to resist the axial and shear forces at the joint, while the plate-wood contact area must be adequate to resist the withdrawal of the plate from the connecting members. The tension and shear capacities of the plates depend on the plate pattern, orientation, and steel strength. Whereas the lateral-resistance (tooth-holding) capacity depends on factors like: steel strength, tooth characteristics, plate and wood orientations, specific gravity, species of wood, moisture content, method of plate installation, embedment gap, and age of the sample (4,5,6,9,12).
The truss connector plates are symmetrically plated on both faces of a joint and connect two or more members meeting at the joint. The plates on both faces are equally effective for in-plane loadings. However, for out-of-plane loading, the plate-wood contact area only at one face on each side of the connection is effective. The connector plates easily buckle with increasing load and induce out-of-plane distortion of the connection, followed by a gradual withdrawal of the teeth near the joint. The connection...