Issue 43

E. Maiorana et alii, Frattura ed Integrità Strutturale, 43 (2018) 205-217; DOI: 10.3221/IGF-ESIS.43.16 208 Surface treatment Class Slip factor μ Surfaces blasted with shot or grit with loose rust removed, not pitted. A 0.50 Surfaces blasted with shot or grit; a) spray-metallized with aluminum or zinc based product b) with alkali-zinc silicate paint with a thickness of 50 μm to 80 μm B 0.40 Surfaces cleaned by wire brush or flame cleaning, with loose rust removed C 0.30 Surfaces as rolled D 0.20 Table 2: Classifications that may be assumed for friction surfaces according to EN 1090-2 [2]. Surface treatment Class Slip factor μ Surfaces blasted with shot or grit with loose rust removed, not pitted. A 0.50 Surfaces hot dip galvanized to EN ISO 1461 and flash (sweep) blasted and with alkali-zinc silicate paint with a nominal thickness of 40 μm to 80 μm B 0.40 Surfaces blasted with shot or grit: a) coated with alkali-zinc silicate paint with a nominal thickness of 40 μm to 80 μm; b) thermally sprayed with aluminium or zinc or a combination of both to a nominal thickness not exceeding 80 µm B 0.40 Surfaces hot dip galvanized to EN ISO 1461 and flash (sweep) blasted (or equivalent abrasion method) C 0.35 Surfaces cleaned by wire-brushing or flame cleaning, with loose rust removed C 0.30 Table 3: Classifications that may be assumed for friction surfaces according to prEN 1090-2. Surface treatment Class Slip factor μ Uncoated clean mill scale steel surfaces or surfaces with class A coatings on blast-cleaned steel A 0.30 Uncoated blasted and cleaned steel surfaces or surfaces with class B coatings on blasted and cleaned steel B 0.50 Roughened hot-dip galvanized surfaces C 0.30 Table 4: Classifications that may be assumed for friction surfaces (according to RCSC [3]). Cruz et al. [10] obtained slip factors with values of 0.50 with blasted surfaces, without any additional surface treatment. In blasted surfaces, spray metalized with zinc or hot-dip galvanized ones, the slip factor easily reaches values above 0.40. For blasted surfaces, with a painted coating of zinc ethyl-silicate, in Cruz et al. [10] a characteristic value of 0.40 was obtained with a small margin. For blasted surfaces, with a painted coating of zinc epoxy, the lowest slip factor values, no higher than 0.30, were obtained. Concerning the specimens in S355 weathering steel, it was verified that the value of the slip factor increased with the duration of environmental exposure, from 0.502 to 0.560. Cruz et al. [10] conclude that the slip factor is strongly influenced by the surface treatment and weakly by the steel grade. In fact, in specimens of S275 steel and S690 high strength steel, with equivalent surface treatment, similar values for the slip factor were obtained. Therefore, it seems that the classification system predicted in EN 1090-2 [2] remains valid for use in slip resistant joints with high strength steel.