High temperature tests of cold-formed stainless steel double shear bolted connections

• 194 double shear bolted connections of cold-formed stainless steel were tested.
• Steady state and transient state test methods were used.
• Austenitic stainless steel grade EN 1.4571 generally has a better performance.
• The current design predictions are generally conservative at elevated temperatures.
• Results from the two test methods have a similar strength reduction tendency.

There is currently no design rule on bolted connections of cold-formed stainless steel structures at elevated temperatures. In this study, a total of 194 double shear bolted connection specimens with three different grades of stainless steel were tested, where 106 specimens were tested by steady state test method and 88 specimens were tested by transient state test method. 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). The connections were designed with different bolt diameters, number of bolts and arrangement of the bolts. Bearing failure and net section tension failure modes were observed in the double shear bolted connection tests. The test results were compared with the nominal strengths calculated from the design rules in the American Specification, Australian/New Zealand Standard and European Codes for stainless steel structures. In calculating the nominal strengths of the connections, the material properties at elevated temperatures were used in the design equations for room temperature. It is shown that the strengths of the cold-formed stainless steel double shear bolted connections obtained from the specifications are generally conservative at elevated temperatures. The connection strengths decrease as the temperature increases in the similar manner for the steady state tests and the transient state tests as well as the material coupon tests. It is also found that the austenitic stainless steel type EN 1.4571 generally has better resistance than the stainless steel types EN 1.4301 and EN 1.4162 for double shear bolted connections at elevated temperatures.