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Frequently Asked Questions: Connectors for Cold-Formed Steel Curtain-Wall Construction and Bridging Connectors

Curtain-Wall Clips

General Design

What safety factors have been used to establish allowable loads for your curtain-wall clips?

The typical safety factor (Ω) used to determine the allowable connector loads ranges from 2.25 to 2.45. Safety factors have been established through testing in accordance with ICC-ES Acceptance Criteria for Connectors Used with Cold-Formed Steel Structural Members (AC261) and Chapter F of the AISI North American Specification for the Design of Cold-Formed Steel Structural Members (S100-2007). Values depend on the test failure mode, the coefficient of variation of the test results, and the number of tests performed.

For the allowable anchorage loads, the safety factor is established in the same manner as connectors described above if the test is limited by the connector, screws, or welds. Higher safety factors are used if test loads are limited by the performance of anchors in concrete (Ω = 4.0) or shot pins (Ω = 5.0) to reflect the higher variability and sudden failure associated with these limit states.

Design For In-Plane Loads

I need to transfer in-plane loads from the curtain-wall to the main building structure. Do you provide allowable loads for this load direction?

Yes. Allowable in-plane loads (what we refer to as 'F1' loads), are published in the Simpson Strong-Tie® Connectors For Cold-Formed Steel Construction catalog.

Fasteners and Anchorage

You list a minimum required steel thickness of 3/16" for anchorage using #12 screws. What is the maximum steel thickness I can use with #12 screws?

The maximum steel thickness you can anchor to using #12 screws depends on the screw. Many factors affect the maximum thickness, but self-drilling screws cannot drill through material thicker than the length of the drill point. Fastener manufacturers often publish the recommended maximum total thickness. The Simpson Strong-Tie® XQ1S1214 screws may be installed in steel up to 1/4" thick. Other screws with appropriate drill points may be installed in steel up to 1/2" thick.

Bridging Connectors

I've seen standard details for wall stud bridging that show the cold-rolled channel attached to the stud with a clip angle of length equal to either 80% of the stud depth or 1/2" less than the stud depth. Do the Simpson Strong-Tie® SUBH and MSUBH bridging connectors comply with the code, and do the generic clip angle length requirements contained in these details apply?

The Simpson Strong-Tie SUBH and MSUBH bridging connectors comply with the code and dimensions have been established to provide structural performance while simplifying installation. AISI S100-2007 Section D3 contains strength and stiffness requirements for all bridging connections, however, the specification does not include limitations on dimensions or restrict how the strength and stiffness of the bridging connector is achieved. Note that the standard details that include minimum dimensions for the clip angles are not part of the code. They are prescriptive details applicable to generic clip angles and therefore do not apply to the SUBH and MSUBH connectors. Instead, strength and stiffness design values for the SUBH and MSUBH connectors in studs of various depth and thickness have been established through extensive testing to ensure compliance with AISI S100-2007 Section D3 for axially and laterally loaded stud wall systems.