When designing a shearwall according to the International Building Code (IBC), a holdown connector is used to resist the overturning moment due to lateral loading. From a structural statics point of view, a shearwall without dead load or holdowns would have zero lateral-resisting capacity without any restraint to resist the overturning moment. Since the wall assembly still has the sill plate anchorage providing resistance to overturning, testing can measure the capacity of a wall assembly without holdowns.
While the title of this blog post might remind you of the tasty turkey dinner you enjoyed on Thanksgiving, it’s actually a question regarding a shear wall component’s effect on performance. What type of fastener do you use to attach wood structural panel sheathing to cold-formed steel (CFS) framing, and what is the effect on a shear wall assembly?
Structural sheathing is most commonly attached to CFS framing with self-piercing or self-drilling tapping screws, power driven pins, and adhesives.
The AISI North American Standard for Cold-Formed Steel Framing – Lateral Design standard (S213) specifies using either #8 or #10 self-tapping screws (depending on the assembly) that comply with ASTM C1513, and have a minimum head diameter of 0.285” or 0.333”, respectively.
It’s worth noting that you cannot verify ASTM C1513 compliance by simple inspection. While screw dimensions are easy to measure, other features such as hardness, ductility, torsional strength, drill drive, and thread tapping cannot be evaluated in the field or by visual inspection. It’s prudent that a Designer and jurisdiction expect a screw manufacturer to validate its product’s compliance with ASTM C1513. This can be done through test reports by an accredited test lab and evaluation data, or by an evaluation report published by an ANSI-accredited product certification entity such as ICC-ES or IAPMO UES.Continue Reading