Slip factors for slip-resistant connections made of stainless steel

Stainless steels are becoming more and more popular as a construction material in both building and civil engineering structures, because of their high material strength, ductility and corrosion resistance. In this frame, the execution of slip-resistant connections made of stainless steel is necessary, e. g. in footbridges, facades etc. As no design regulations exist in any code, special experimental testing has to be performed in each case. Stainless steel alloys are thought to suffer more than carbon steels from time dependent viscoplastic deformation at room temperature. It could lead to higher preload losses and consequently to lower slip factors than achieved for carbon steels with comparable surface treatment. However, no evidence of this behaviour can be found in literature for preloaded bolted connections. For this reason, slip factors for the various stainless steel grades have to be determined experimentally if they want to be used in the steel structures. In the frame of the European RFCS-research project SIROCO, the preloading behaviour of stainless steel bolted connections as well as the slip-resistant behaviour of slip-resistant connections made of austenitic, various duplex and ferritic stainless steels have been investigated. In this paper, the results of slip factor tests on four stainless steel grades are presented and the influence of different surface treatments and the preload level on the slip factor of stainless steel slip-resistant connections is discussed. Finally, slip factors for various stainless steel grades with different surface treatments are proposed for a future implementation in the next revision of EN 1090-2.