Understanding slip coefficient and tension creep testing of coatings used in slip-critical bolted connections / Bill Corbett in JOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL), Vol. 31, N° 1 (01/2014)

[article]  inJOURNAL OF PROTECTIVE COATINGS & LININGS (JPCL) > Vol. 31, N° 1 (01/2014) . - p. 22-41 Titre : Understanding slip coefficient and tension creep testing of coatings used in slip-critical bolted connections Type de document : texte imprimé Auteurs : Bill Corbett, Auteur ; Carly McGee, Auteur Année de publication : 2014 Article en page(s) : p. 22-41 Langues : Américain (ame) Catégories : Assemblages à boulons Calcul Coefficient de glissement Essais (technologie) Essais dynamiques Fluage Métaux -- Revêtements protecteurs Index. décimale : 667.9 Revêtements et enduits Résumé : Bridges, buildings, and other structures commonly include designed bolted connections of steel beams, girders, and other structural members using connection/splice plates of various sizes and configurations. High-strength bolts are used to secure the connections. The holes in the steel members and the connection/splice plates are larger (typically 1/16-1/8 of an inch larger) than the boit shafts to enable the bolts to be inserted and tensioned against the washers and nuts. The interface of the connection/splice and the structural member is called a faying surface. Faying surfaces are not required to be coated, but are often protected to prevent corrosion at the interface and rust bleed on coated surfaces adjacent to the connection. When a designer elects to coat the faying surfaces, the coating used on these surfaces must have slip-resistant properties to reduce fatigue on the connection during loading/unloading cycles (e.g., vehicles traveling across a bridge deck). Therefore, before use, the coatings specified for these faying surfaces must be tested and classified for slip coefficient properties. Once the classified coating is applied, the connection points are masked to prevent subsequent coats from inadvertently contacting these areas. There is no stipulation for specific coating types that must be used in these bolted connections, although zinc-rich primers are common and typically have slip resistance properties. Other generic coating types, including polyamide epoxy primers, have been tested and used. Other products, such as thermal spray coatings (various alloys, with and/or without a sealer) and roughened hot dip galvanized steel may be viable candidates, provided they have been tested and demonstrate slip-resistant properties. The American Institute of Steel Construction (AISC) and the Research Council on Structural Connections (RCSC) publish the Specification for Structural Joints Using High Strength Bolts. The specification comprises ten sections, which only minimally address testing of coatings used in bolted joints. However, Appendix A, "Testing Method to Determine the Slip Coefficient for Coatings Used in Bolted Joints" contains four sections relating to coating testing (General Provisions; Test Plates and Coating of the Specimens; Slip Tests; and Tension Creep Tests). The focus of this article is on the testing required in Appendix A. Note de contenu : - ESSENTIAL VARIABLES - CORRECTION OF COATING THICKNESS DEFICIENCIES - TEST PLATE DESIGN AND SURFACE PREPARATION - TEST PLATE MOUNTING, COATING APPLICATION, AND CURING PROCEDURES - COATING THICKNESS MEASUREMENT AND SELECTION OF CONTACT SURFACES - TEST ASSEMBLIES : Slip coefficient test procedure - Slip coefficient calculation - Tension creep test procedure - OTHER CONSIDERATIONS : 1. What is the effect (if any) of surface profile shape on the slip coefficient properties of coatings ? - 2. What is the effect (if any) of surface profile depth on the slip coefficient properties of coatings ? - 3. Is there a difference in slip coefficient properties when a coating is tested over a surface that has been power tool cleaned (i.e. SSPC-SP 11 or SP 15) versus abrasive blast cleaned ? - 4. Is there a curing "window" (both a minimum and a maximum set time prior to bolt-up) ? - 5. What is the effect of using a different type of thinner (acceptable for use by the coating manufacturer) on the slip coefficient properties ? - 6. What is the effect of using lesser or greater amounts of thinner ? - 7. Five replicate assemblies are tested for slip coefficient and then averaged to generate a single slip coefficient value. Is there an acceptable standard deviation between the replicate trials ? that is, what determines an "outlier" ? - 8. Mating of dissimilar coatings Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=20904 [article]

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