Repair of Partially Embedded Metal Connector Plates

Partially embedded metal connector plates can occur in wood trusses when the plates are not properly pressed, when they "walk out" as the wood dries during service, or when there is a mismatch in member thickness. Current industry practice is to ignore the remaining strength of a partially embedded plate when making repairs. This assumption results in a large, overdesigned repair along with high material and labor costs. The project objective was to determine if a smaller clamped repair is sufficient to restore the strength of the partially embedded plate to the fully embedded connection strength. A total of 40 tension splice connections were fabricated from 2 by 6 members with 5 by 3 metal connector plates. The specimens included 10 fully embedded plates, 10 partially embedded plates, 10 partially embedded plates repaired with plywood gussets secured outside of the main 2 by 6 members (RC), and 10 partially embedded plates repaired with plywood gussets and light wood screws (RS). The average strength of the partially embedded RC specimens and partially embedded RS specimens were 87 and 108 percent of the fully embedded specimens' strength, respectively, whereas the unrepaired partially embedded plates achieved only 60 percent of the fully embedded specimens' strength. The results of the tests indicate that smaller screw-type gusset repairs are sufficient to return the strength of a tensile splice connection with a 1/16-inch partially embedded plate to its fully embedded plate capacity. Both the clamping action of the plywood gussets and the additional tensile capacity of the screwed plywood gussets were observed to contribute to the strength gains.