The 1980s

The 1980s Подпись: (5)

Schuster and Ling (1980) developed a new shear-bond expression for composite slabs on the basis of the mechanical interlocking capacity of concrete and steel deck within the shear span. Equation 5 is similar to Eq. 3, however, the strength of concrete and the percent of steel terms are no longer in the expression. Based on the available data, it was found that these two parameters are not important terms. The percent of steel parameter is not required since separate tests have to be carried out for each steel deck thickness anyway. See Eq. 3 for the description of terms.

Equation 5 was adopted in 1984 by the Canadian Sheet Steel Building Institute (CSSBI) for the calculation of the shear-bond strength of composite slabs. A number of updated editions have since
followed [Schuster and Trestain (2002)]. Schuster (1980) presented a paper on composite steel deck concrete floor slabs, highlighting the detailed development of Eq. 5.

Venkataramaiah et al (1980) did a study on the experimental determination and the statistical evaluation of the elastic modulus of elasticity of cold-formed sheet steel. In addition to some column compression data found in the literature, tensile coupon tests were carried out as part of this study. After a statistical study, it was found that the mean value of the elastic modulus of cold-formed steel is 30 071 ksi (207 332 MPa), which is greater than the value of 29 500 ksi (203 395 MPa) that is used by the AISI Specification and the CSA S136 Standard.

Wing and Schuster (1981, 1982, 1986) started to carry out research in the field of web crippling of cold-formed steel members, followed by numerous other studies over the years. This work dealt with web crippling and the interaction of bending and web crippling of multi-web cold formed-steel deck sections. One of the major reasons for this study was to correct some of the inconsistencies that existed in the two North American cold-formed steel design documents at that time. Since web crippling of cold-formed steel sections is an extremely complex analytical problem, experimental testing had to be carried out. Web crippling without the influence of bending is typically divided into the following four categories: 1) End one-flange loading (EOF), 2) Interior one-flange loading (IOF), 3) End two-flange loading (ETF), 4) Interior two-flange loading (ITF). Only with the IOF loading case was some moment present, however, the specimens were short enough so that the moment influence was kept to an absolute minimum. In the case of the interaction of bending and web crippling, the specimens were of larger length to account for different degrees of bending influence. The work by Wing on web crippling of multi-web cold formed-steel deck sections was adopted in the 1984 edition of CSA S136.

Schurter et al. (1982) carried out a study on three different cold-formed steel C-section type studs, i. e., one section had solid webs and the other two had lip-reinforced trapezoidal holes in the webs. The tests consisted of 1) Stub column tests and 2) Full scale wall assembly panel test that were subjected to compression load and combined compression and lateral load. The test results were compared to their respective calculated values, resulting in good correlations.

Seleim and Schuster (1982, 1985) developed a new shear-bond expression for composite slabs. The reason for this work was to reduce the number of composite slab tests required to establish the shear-bond capacity of any given composite floor system. Typically, four different steel deck thicknesses are produced by any given composite slab manufacturer. Using Eq. 5 and having to test four composite slab specimens for each steel deck thickness [Schuster, Trestain (2002)], 16 composite slabs would have to be tested to establish the shear-bond capacity of any given composite floor system. This can be quite costly. The work by Saleim produced the following shear-bond expression, which has been adopted by the CSSBI [Schuster, Trestain (2003)]:

Подпись: (6)V t 1

Подпись: 4= K,- + K2— + K3t + K bd 1 L’ 2 L’ 3

where (t) is the steel deck thickness and K to K4 are shear-bond coefficients that have to be obtained from a multiple linear regression analysis of the test data. In this case, only eight slab specimens have to be carried out to establish the shear-bond capacity.

Schuster and Suleiman (1986) carried out a study on composite slabs subjected to repeated point loading. Composite slabs are sometimes subjected to repeated point loading, such as resulting from forklift trucks. In this study, experimental testing was carried out on single span and double span composite slabs, using only one particular company’s composite slab product. To establish the ultimate capacity of the composite slabs, first static load tests were carried, followed by a number of respective repeated load tests subjected to cyclic loading. It was found that shear-bond was always the mode of failure, and the composite slabs were able to carry 75% of the static load up to 1.25 million cycles without failure.

McCuaig and Schuster (1988) did a similar study as Suleiman (1986), except the composite steel deck was from a different manufacturer. Based on these test results, the conclusions were that both simple and double span specimens were able to sustain repeated point loads of 55% of static ultimate for at least 1.25 million cycles and the mode of failure in all cases was by metal fatigue in the steel deck.

Schurter and Schuster (1986) were involved in investigating the shear-bond capacity of composite slabs relating to the surface conditions/coatings of the steel decks. Twenty pull-out tests involving four different metallic coatings and four different surface conditions were carried out. As well, six full – scale slab tests with two different metallic coatings (AZ150 Galvalume and Z275 galvanized) were performed. It was concluded that the shear-bond capacity of the AZ150 Galvalume steel slab was on average 32 % greater than the Z275 galvanized steel slab.

Schuster et al. (1986), Fox et al. (1986) and Schuster (1987, 1991) presented papers on the Canadian Standard for the Design of Cold-Formed Steel Structural Members, highlighting the new Limit States Design approach used in Canada.