The 1990s

McCuaig and Schuster (1990) performed resistance factor calibrations for the shear-bond failure mode of composite slabs. 196 test data, representing nine different product types, were used in the reliability calibrations based on a dead load factor of 1.25 and a live load factor of 1.5, as specified in the National Building Code of Canada. It was concluded that a resistance factor of 0.7 can be used for shear-bond of composite slabs, resulting in an average calculated safety index of 3.71, which corresponds well with the target safety index of 3.5.

Schuster (1991, 1992) presented a paper on lightweight steel framing in the 90s, focusing on the use of cold-formed steel in residential construction. In 1992, Schuster presented a paper, entitled "The 1989 Edition of the Canadian Cold Formed Steel Design Standard”.

Dinovitzer et al. (1992) made some important observations pertaining to the CAN/CSA-S136-M89 cold-formed steel design Standard. In the case of partially stiffened compression elements, discontinuities in effective width estimates for sections with similar flanges and stiffeners were observed, resulting from a sudden change in the behavioural states. Recommendations are presented to rectify this discontinuity and at the same time simplifying the analysis procedure. These recommendations are now contained in the North American Design Specification. In addition, a simplification was presented for deflection determination of multi-web deck sections. A new plate buckling coefficient was developed to be used in the basic effective width expression.

Papazian et al. (1994) carried out an experimental investigation on multiple intermediate longitudinally stiffened deck profiles. The primary objective of this work was to substantiate the design approach contained in the CSA S136 Standard for closely spaced intermediate longitudinal stiffeners. It was the belief that this approach was quite conservative in that it only addressed the elastic plate buckling capacity. All tests were subjected to a uniform bending load using a vacuum chamber. It was concluded that indeed the ultimate capacities were conservative.

Schuster et al. (1995) undertook an investigation of perforated cold-formed steel C-Sections in shear. The reason for this work was because no specific design provisions were contained in the design Standards for perforated web elements subjected to shear, even though such sections are frequently found in practice. Experimental testing was carried out to substantiate the analytical formulation. The work resulted in a design approach that is now contained in the North American Design Specification.

Rogers and Schuster published four different papers in 1996, all resulting from the research by Rogers. 1) Effective Width of a Single Edge Stiffener Subjected to a Stress Gradient; 2) Interaction of Flange/Edge-Stiffened Cold Formed Steel C-Sections; 3) Cold Formed Steel Flat Width Ratio Limits, d/t and di/w; 4) Test Results and Comparison of Cold Formed Steel Edge Stiffened C and Z-sections. Every one of these papers resulted in meaningful design information.

Hancock et al. (1996) published a paper entitled, “Comparison of the Distortional Buckling Method for Flexural Members with Tests” and in 1997, Rogers and Schuster followed with a paper on the flange/web distortional buckling of cold-formed steel sections in bending.

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Prabakaran and Schuster (1998) developed a new web crippling expression for cold-formed steel members that can be used for different geometric shapes and the four loading cases, and it is non­dimensional. The following expression for the nominal web crippling strength was adopted by the 94 edition of CSA S136 and the North American Specification for the Design of Cold-Formed Steel Structural Members:

where (t) is the web steel thickness; Fy is the design yield point of the steel; C, CR, CN and Ch are coefficients that have been established based on experimental data found in the literature. These coefficients are given in the North American Specification for the different geometric section types and load cases. This work by Prabakaran was actually completed in 1993.

Gerges and Schuster (1998) carried out an experimental investigation on the web crippling of

single web cold-formed steel members subjected to end one-flange loading (EOF). The primary focus of this study was on single-web C-sections with large inside bend radius to thickness ratios. There was insufficient data in the literature to properly establish the web crippling coefficients. This study produced the additional data and the appropriate web crippling coefficients were established.

Acharya and Schuster (1998, 1998) undertook a study of hat-type sections with multiple intermediate longitudinal stiffeners subjected to uniform bending load. Similar to Papazian et al. (1994), additional tests were carried out in a vacuum chamber to complete the data pool for the establishment of a new plate buckling coefficient to be used with the basic effective width expression.

Fox and Schuster (1998) investigated the use of bearing stiffeners with C-section floor joists. Tests were carried out involving three different types of stiffeners, i. e., stud section, track section and a fully effective bridging channel section. The governing design Standards required that a stiffener must be fully effective, which is a restriction that is rather difficult to meet in practice. Based on this investigation, it was concluded that the governing design provisions for bearing stiffeners do not accurately predict the capacity of the stiffeners currently used in lightweight steel framing.

Schuster (1998, 1998) presented a paper on the advantages of having one North American Specification for the Design of Cold Formed Steel Structures. In the paper entitled, “Cold-Formed Steel – the Construction Material of the Future”, Schuster presented