sfia cold formed steel framing 2012 edition

The mystery, structural behavior of cold-formed steel (CFS) clip angles, has puzzled engineers since the great George Winter helped AISI publish its first Specification in 1946. Meanwhile, in another part of the DC Beltway about 15 miles to the southeast, another great mystery is being deciphered at the American and Iron Institute (AISI) headquarters. It’s a sculpture called Kryptos, and although it’s been partially solved, it contains an inscription that has puzzled the most renowned cryptanalysts since being erected in 1990. All Telling Industries products are formed from steel with a mini-mum yield strength of 33 or 50 KSI(1000 lbs per square inch) All products contained in this brochure are engineered to meet the 2012 Edition of the AISI (American Iron and Steel Institute) North American Specification for the Design of Cold-Formed Steel Struc -One of the world’s greatest unsolved mysteries of our time lies in a courtyard outside of the Central Intelligence Agency (CIA) headquarters in Langley, Virginia.

Even with modern Finite Element Analysis (FEA) tools, without test data to help establish initial deformations and boundary conditions, FEA models have proven inaccurate. The primary problem has been the lack of test data to explain clip angle structural behavior. UnleSS noTed oTherwiSe, all producTS covered in ThiS SFia caTalog are engineered To meeT The 2012 ediTion oF The american iron and STeel inSTiTuTe (aiSi) S100-12, norTh american SpeciFicaTion oF The deSign oF cold. Additionally, there has been considerable debate within the AISI Specification Committee concerning anchor pull-over strength of CFS clip angles subject to tension.AISI S211-07 w/ S1-12 (2012) AISI North American Standard for Cold-Formed Steel Framing Wall Stud Design, 2007 Edition with Supplement 1 (Reaffirmed.producTS manuFacTured by SFia memberS are Formed From STeel wiTh a minimum yield STreSS oF 33 or 50 kipS per SQuare inch (kSi).

Yu’s team performed 33 tests for shear, 36 tests for compression, and 38 tests for pull-over due to tension. At the University of North Texas. The report summarizes the structural behavior and preliminary design provisions for CFS load bearing clip angles and is based on testing that was carried out in 20 under the direction of Cheng Yu, Ph.D.

Finally, for pull-over due to tension, it was found that clip angle specimens exhibited significant deformation before pulling over the fastener heads (essentially the clip turns into a strap before pull-over occurs). It was further found that using a buckling coefficient of 0.9 in the critical elastic buckling stress equation will produce conservative results. Therefore, an alternate solution was developed that utilized column theory in conjunction with a Whitmore Section approach that yielded good agreement with test results. Test results were compared to the gusset plate design provisions of AISI S214, North American Standard for Cold-Formed Steel Framing – Truss Design, and the axial compression member design provisions and web crippling design provisions of AISI S100, North American Specification for the Design of Cold-Formed Steel Structural Members, but no good agreement was found. For compression, it was found that flexural buckling was the primary failure mode. Simplified methods were also developed to limit shear deformations to 1/8 inch.

As briefly mentioned above, the existing pull-over testing has demonstrated that excessive deflections can be expected before pull-over actually occurs. Another glaring research hole is the load versus deflection behavior of clip angles under tension. This is something that does not occur for many practical CFS framing situations and will need additional research. For instance, how are the test results influenced by the fastener pattern? All of the test data to date has used a single line of symmetrically placed screws. However, just as the CIA’s Kryptos remains only partially solved, some aspects of clip angle behavior remain a mystery.

Fortunately, AISI in conjunction with its CFS industry partners continues to fund research on CFS clip angle behavior that will answer these questions, and possibly many more.

Sfia Cold Formed Steel Framing 2012 Edition