In the previous section of this guide, we shared wind uplift rod run component model numbers and capacities along with the design requirements published by ICC-ES in Acceptance Criteria 391. While some of these design considerations are for the rod run components, others are for the wall-framing elements that transfer load to the rod runs. Simpson Strong-Tie used these requirements to earn the only system evaluation report (ICC-ES ESR-1161) in the industry. However, AC391 also allows for reports that consider only rod run components and not the wall-framing elements. This allows the designer or Engineer of Record to specify a rod run based on the allowable load deflection values for the rod run itself, and determine for themselves an appropriate spacing of the rod runs to ensure the wall-framing elements satisfy load and deflection limits for their structure. To assist designers in the specification, we offer guidance below for two methods of specifying our Strong-Rod URS.
Once designers know their wood framing species, net uplift at roof-bearing walls and length of rod run, then they can specify the following information on the plans:
To assist in this specification, reference URS Run Tables. Table 1 provides the allowable tension load (PA) of each URS rod run based on model number (rod diameter and take-up device). Table 2 provides the equations to calculate the deflection of each URS model based on demand tension load, length and wood species. For simplicity, Tables 3 and 4 provide tabulated deflection values for various combinations of tension load and length.
Designers may choose to provide performance specification as part of their construction documents and require the contractor to submit deferred design calculations and shop drawings. To do so, the following performance criteria should be on the plans.