And because the components can be manufactured in factories and installed on-site, the construction period is greatly reduced. Generally, beams, columns, trusses, and other components made of section steel and steel plates constitute a load-bearing structure, which together with roof, wall, and floor, form a building.Ĭompared with traditional concrete buildings, metal structure buildings use steel plates or section steel instead of reinforced concrete, higher strength, and better seismic resistance. In all cases, when fasteners are painted, it is critical that the specified coatings be thoroughly applied to threads, crevices and edges.The metal buildings uses steel to form a load-bearing structure. If there are questions regarding the adequacy of the cleaning and the acceptability of remaining stains, the coating system can be applied on a test basis and the adhesion examined. Before painting, fasteners must be cleaned of surface contamination, and in the case of galvanized nuts, the lubricant removed to the extent that adhesion of the subsequently applied coating is not compromised. Alternative fasteners should be considered if feasible, such as galvanized or treated, in order to avoid the need for blast-cleaning in the field. When black fasteners are installed after the paint has been applied, abrasive blast-cleaning in preparation for painting can create significant damage to the surrounding coating. While this assumption may be valid, because many different coating types and brands are used in the field, it is the author’s opinion that if multiple coats will be applied to the backside of splice plates prior to bolting, consideration should be given to testing the system, at least in those cases where a Class B certification is required.įor bolt holes, unless some rusting prior to assembly is not acceptable, a common practice is to not require coating the interior surfaces, but allowing the coating to be deposited into the holes as part of the application to the face of the member.
It should be noted, however, that professionals closely involved with the RCSC specification have indicated that specimens with 10 mils of coating on the backsides of the plates had been successfully tested in the past and therefore, it was assumed that up to 15 mils of combined coating thickness/galvanizing thickness (in the case of galvanized fasteners) would not likely affect the results.
Splice plate galvinized steel full#
Accordingly, for a given project, if a decision is made to paint the backsides of the splice plates with the full coating system rather than just the primer, the effect of the full paint system on the tension creep performance is not clearly addressed by the certification. However, the effect on bolt pretension of any additional coats applied to the backsides of the plates is not incorporated into the normal test regimen. Since the primer is applied to the backsides as part of the normal test protocol, any compression of the coating is incorporated into the test results. Because bolts are used to secure the samples, the results could be impacted if there is significant compression of any material - for example, the paint, TSC or galvanizing on the faying surfaces or beneath the bolt head or washer/nut and the steel plates, which could affect the clamping force. While the actual clamping force depends on the bolt type or installation method, for Class B it is a minimum of 32.7 kips for the locked tension and a minimum of 49 kips for the final tension. Both the locked tension for 1,000 hours and the final tension to be placed on the specimens are derived from a formula that is based on the slip coefficient classification of the samples and the average clamping force. At the end of 1,000 hours, the tension is increased over the course of a few minutes to a final load. A load is applied to the chain in tension and held for 1,000 hours (approximately 42 days). The unpainted portions are only connected using loose pin bolts and are not part of the test. The clamping force is achieved by connecting the painted portions of the plates with 7/8-inch diameter A490 bolts that are secured with corresponding nuts. Three replicate specimens (of three plates each) are linked together in a single chain-like arrangement (Figs.
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