These general notes are provided to ensure proper installation of Simpson Strong-Tie straps and ties.
When installing floor-to-floor straps, wood shrinkage and compression that occurs during construction may cause the straps to bow out if both ends of the strap are nailed during initial installation.
To prevent this, filling all fastener holes in the strap (including the rim joist area) will limit the bowing. Alternatively, fill the holes in the top of the strap before the roof is installed and then filling the bottom half of the strap after will also help reduce bowing.
When a connector is loaded simultaneously in more than one direction, the allowable load must be evaluated as option 1 or 2.
Option 1: Unity Equation
For all connectors use the following equation:
Design Uplift / Allowable Uplift + Design Lateral Parallel to Plate / Allowable Lateral Parallel to Plate + Design Lateral Perpendicular to Plate / Allowable Lateral Perpendicular to Plate < 1.0.
The three terms in the unity equation are due to the possible directions that exist to generate force on a connector. The number of terms that must be considered for simultaneous loading is at the sole discretion of the Designer and is dependent on their method of calculating wind forces and the utilization of the connector within the structural system.
Option 2: 75% Rule
As an alternative, certain roof-to-wall connectors (embedded truss anchors, pp. 248–249, seismic and hurricane ties, pp. 270–272, and twist straps, p. 277) can be evaluated using the following: The design load in each direction shall not exceed the published allowable load in that direction multiplied by 0.75.