Oftentimes, MiTek engineers are asked what plate embedment tolerance is allowed for metal connector plates in wood trusses.
Chapter 3 of the ANSI/TPI 1 (National Design Standard for Metal Plate Connected Wood Truss Construction) addresses the tolerance for metal connector plate tooth embedment into the wood members. Per section 3.7.7.2.4: “Tooth embedment gap is defined as the distance between the underside of the embedded Metal Connector Plate and the surface of the Wood Member. Tooth embedment gap shall be measured through the slot opening of the Metal Connector Plate, with an accuracy of 0.01 in.”. [For image, See PDF or View in Full Issue.]
The teeth are 100% effective if a tooth embedment gap is equal to or less than 1/32 in. (Table 3.7-1 Tooth Effectiveness). ANSI/TPI 1 permits a reduction to be taken for teeth that are not fully embedded. If the tooth embedment gap is between 1/32 in. and 1/16 in., the teeth are 60% effective. If the tooth embedment gap is between 1/16 in. and 3/32 in., the teeth are 40% effective. The teeth are 0% effective if the gap is greater than 3/32 in.
Per section 3.8 of ANSI/TPI 1: “The repressing of partially embedded Metal Connector Plates to improve embedment shall be permitted for plates that were not fully embedded at the time of fabrication.”
Per section 3.9.3 of ANSI/TPI: “When a Metal Connector Plate is installed in the connection area of lumber that contains tooth holes from a previously installed plate and where the wood is otherwise undamaged, Metal Connector Plate Teeth shall be considered 50% effective.”
For additional information, or if you have questions, please refer to ANSI/TPI 1 or contact the MiTek Engineering department.