Behavior of cold-formed stainless steel single shear bolted connections at elevated temperatures

Abstract

The current design rules on bolted connections of cold-formed stainless steel structures are allowed for room (ambient) temperature condition only. Research on structural behavior of single shear bolted connections at elevated temperatures is limited. In this study, 100 single shear bolted connection specimens and 22 coupon specimens involving three different grades of stainless steel were conducted by using steady state test method in the temperature ranged from 200 to 950°C. The three different grades of stainless steel are austenitic stainless steel EN 1.4301 (AISI 304) and EN 1.4571 (AISI 316Ti having small amount of titanium) as well as lean duplex stainless steel EN 1.4162 (AISI S32101). Furthermore, different bolts arrangement was also considered in the investigation. Two main failure modes were observed in the single shear bolted connection tests, namely the net section tension and bearing failures. The test results were compared with the predicted strengths calculated from the American Specification, Australian/New Zealand Standard and European Codes for cold-formed stainless steel structures. In calculating the nominal strengths of the connections, the reduced material properties of stainless steel obtained at elevated temperatures were used. It is shown that the strengths of the single shear bolted connections predicted by the specifications are generally conservative at elevated temperatures. A similar tendency of reduction was found when compared the reduction factor of material properties with that of the deterioration of the bolted connection test strengths with the corresponding type of cold-formed stainless steel at elevated temperatures. The austenitic stainless steel type EN 1.4571 (AISI 316Ti) generally performed better than the other two stainless steel types at elevated temperatures.