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URS: Method 1 – Designer Selects System and Specifies on Building Plans

Selection and Specification Procedure

Designers may specify the Simpson Strong-Tie® Strong-Rod™ Uplift Restraint System for roofs (Strong-Rod™ URS) by utilizing the Strong-Rod URS rod run tables provided after the layout and net uplift of the roof framing members is calculated by the designer. A complete load path can be achieved by first picking the roof framing/truss connections to the top plate with hurricane ties. Then, to achieve torsional restraint of the top plate, connectors can be chosen to attach the top plate to the studs. A Strong-Rod URS and anchorage system can be chosen based on the net uplift calculated. The following are steps in properly choosing a URS and anchorage system.

Selecting the Appropriate Product

Strong-Rod URS is available in four assemblies: URS3 = 3/8", URS4 = 1/2", URS5 = 5/8" and URS6 = 3/4" rod diameters. Below are steps for selecting and specifying the appropriate rod run solution to resist the demand wind uplift loads for a given wall line.

You can also view a Design Example that presents an in-depth example.

STEP 1 - Determine the wind uplift loads for the roof framing members along each bearing wall line, as outlined below.

  • Calculate roof uplift per the current building code.
  • If trusses are used for roof framing, reactions are listed on the truss shop drawings.
  • Loads should be converted to pounds per lineal feet at allowable stress levels.

STEP 2 – Choose the appropriate shrinkage compensating device.

  • Choose an RTUD or ATUD take-up device based on expected shrinkage and on rod diameters used in step 3.

STEP 3 – Choose the appropriate Strong-Rod™ URS table for roof uplift restraint, narrowing down the table choice by selecting from the following sections:

  • Choose Strong-Rod™ URS based on URS Load Tables
  • Based on the demand uplift forces calculated in Step 1, choose a row from the left-most column.
  • Choose the widest on-center spacing in the second column that provides solutions for the required length of the rod run (typically, length is from foundation to roof top plate).
  • Pick the smallest rod diameter URS model that satisfies the design requirements and rod length.
  • Increased rod spacing may be achieved by choosing to reinforce the splices of the roof-level double top plate (see Top-Plate Splice Bending Reinforcement).
  • Verify sufficient axial capacity in top plates for drag load and chord forces.

STEP 4 – Choose the Strong-Rod URS rod run anchorage.

  • Choose the appropriate anchorage required for the project at each URS wall line. Post-installed concrete foundation anchors can be chosen based on load values for Titen HD® Rod Coupler Anchor.
  • Rods can terminate below the top plate of a wall as long as there are no net uplift forces at anchorage point. Details on options to terminate below the top plate or beam can be found here.

STEP 5 – Choose the appropriate hurricane tie connector to resist the roof member uplift.

STEP 6 – Choose a connection to prevent top plate rotation.

Based on the uplift demand calculated in Step 1, choose a hurricane tie connection to attach the top plate to the stud. The connector will be placed on the same side as the roof-framing-to-top-plate connector.

Specification of the chosen URS model in a given wall line can be as noted in a sample shown:

URS-specification-wall-line

STEP 7 – Get your documents.

Typical details can be chosen and inserted into the construction documents. Options for detailing around window and door openings and holdowns for uplift at girder trusses are available.