Safe Work Load or Working Load Limit

According to AISC, forged steel structural hardware products, such as clevises, turnbuckles, eye nuts and sleeve nuts, are occasionally used in building design and construction. These products are generally forged according to ASTM A668 Class A requirements. ASTM A29, Grade 1035 material is commonly used in the manufacture of clevises and turnbuckles. ASTM A29, Grade 1030 material is commonly used in the manufacture of steel eye nuts and steel eye bolts. ASTM A29 Grade 1018 material is commonly used in the manufacture of sleeve nuts. Other products, such as steel rod ends, steel yoke ends and pins, cotter pins, and coupling nuts are commonly provided generically as “carbon steel.”

I am frequently asked whether we should compare LRFD or ASD load demand with "Safe Working Loads" (SWL) or "Working Load Limit" published by manufacturer's for clamps or hangers or other forged or manufactured products.

It is my understanding that manufacturer's provide?a safe working load that is based upon a factor of safety as high as 5, assuming that the product will be used in rigging or similar applications subject to dynamic loading. The factor of safety in the range of 3 (static usage) to 5 (life safety or dynamic usage) is usually applied to tested?proof load or minimum breaking load.?So the published catalog values might be overly conservative for permanent installations and similar applications subject to static loading only.?

If desired, the published safe work load (SWL) can be converted into an available strength with reliability consistent with that of other statically loaded structural materials. So, the nominal strength, Rn, is determined as:

Rn?= (safe working load) x (manufacturer’s safety factor)

Let's conservatively assume the factor of safety of 3, that is more common and the available strength, φRn?or Rn?/Ω, is determined using φ = 0.50 (LRFD) and Ω = 3.00 (ASD).

Ultimate strength level factored load demand, F_LRFD?< φRn?= 0.5*(3*SWL) = 1.5 SWL

Service level or allowable load demand, F_ASD?< Rn?/ Ω = (3*SWL) / 3 = 1.0 SWL?

Fun Fact: φ*Ω is almost always 1.5, as it is expected that?F_LRFD?= 1.5*F_ASD

It would be very conservative if you calculate the demand based on LRFD load combination and choose the product based on the published safe working load capacities in the catalogs, and a safe practice.