Single shear screwed connection tests of thin sheet steel at elevated temperatures

The design rules on screwed connections of thin sheet steel in the current International specifications for cold-formed steel structures are only applicable for ambient temperature. Up-to-date, investigation of screwed connections at elevated temperatures is quite limited. In this study, a total of 24 single shear screwed connection specimens fabricated from G550 0.42 mm, G500 1.20mm and G450 1.90mm thin sheet steels were conducted by transient state test method. The tests were performed at three different load levels of 25%, 50% and 75% of the failure load at ambient temperature. The critical temperature and the corresponding displacement of screwed connections were obtained from the transient state test curves. The connection strength deterioration obtained from the transient state tests was compared with that obtained from steady state tests. The critical temperatures determined by the transient state test results are slightly higher compared with those deduced from the steady state test results at similar load levels, and even higher than those from the coupon test results. Different failure modes, such as bearing, tear out, material failure and several combined failure modes were observed in the transient tests. It is found that the failure mode of the screwed connections may change as the load level increases.