URS Overview
Strong-Rod® Uplift Restraint System for Roofs
The Simpson Strong-Tie. Strong-Rod uplift restraint system for roofs (Strong-Rod URS) is a continuous rod tiedown solution designed to provide a complete load path to resist uplift (suction) pressure on the roof by transferring these forces through the structure to the resisting elements (typically the foundation).
Designing rod systems to resist wind uplift (URS) is very different from designing rod systems used to resist shearwall overturning caused by lateral wind pressure or seismic forces (ATS). This is due to where each type of force originates in a building. For wind uplift, this is only at the roof and can be reduced by dead load at each level of the building. Lateral forces are applied at each level (each horizontal diaphragm, both roof and floor) of the building, and increase at each lower level as load from the level above is added to the level below.
- Uniform load applied to roof
- Load reduces when transferred down to foundation due to self weight of structure
- Connections uniformly spaced
- Shear load applied at each level
- Load increases when transferred down to foundation
- Connections must be at both ends of shearwalls to resist overturning tension force from wind or seismic applied in each direction
This section of the guide will illustrate the design methods for creating the load path using a rod system to resist wind uplift (URS), explain the key design considerations for both the wood structural elements and rod-run components, provide load capacities for components, suggest methods of specification and show typical details to assist in your design.