Tension and interaction resistance of austenitic and duplex stainless steel bolts

Abstract

The current design rules in EN 1993-1-4 for non-preloaded stainless steel bolted connections under pure shear and tension are essentially based on the regulations for carbon steel bolted connections. Furthermore, the load bearing behaviour under combined tension and shear (category A + D bolted connections) was adopted from EN 1993-1-8 as well. Recent research activities within the German IGF research project “Load-bearing capacity of bolted connections loaded in shear and tension made of stainless steel M12 to M36” (P 1386/IGF-No. 20651 N) showed that stainless steel bolting assemblies behave different. Herein, systematic experimental investigations and an extensive literature review into the shear, tension and interaction resistance of stainless steel bolts were conducted. Furthermore, reliability analyses according to EN 1990, Annex D were accomplished to prove the partial safety factor of γM2 = 1.25 for connections made of stainless steel bolting assemblies. The results regarding the shear resistance have already been presented in a former paper in this journal. In these investigations, it could be shown that an increase of the tension resistance Ft,Rd with k2 = 1.0 is in principle possible following the normative regulations of EN ISO 3506-1 regarding the minimum ultimate tensile strength as well as North American ANSI/AISC 360 and Australian Standard AS 4100. Furthermore, a new interaction approach for both unthreaded and threaded part of the bolt lying in the shear plane could be proposed which has statistically been verified for all property classes with γM* < γΜ2 = 1.25. The new regulations have already been implemented in the current revision of EN 1993-1-4. The background for the new regulations is presented in this contribution.