Experimental investigation on the creep behavior of G550 cold-formed steel at elevated temperatures. (June 2021) - Liu, Kun
Highlights: Creep experiments of G550 CFS were conducted at elevated temperatures. Creep strain is an essential part of G550 CFS under transient-state conditions. A steady-state creep rate expression of G550 CFS was proposed. The critical temperature at which the tertiary creep stage occurred was presented. Abstract: Creep behavior is an important parameter of the material properties of cold-formed steel (CFS) at elevated temperatures and the corresponding investigation is still very limited. In this paper, an experimental study with the creep duration of 4 h was performed for 1.0 mm thick G550 CFS. Forty-one test conditions were selected. The results showed that the creep curves of G550 CFS were distinctly different from that of Q550 and Q690 hot-rolled high-strength steel at elevated temperatures. In addition, the G550 CFS coupon specimens which demonstrated tertiary creep during the experiments would experience creep rupture. For the fire safety of steel structures, a critical temperature of G550 CFS which represented the onset of tertiary creep was given. When the stress ratio was less than 0.7, the critical temperature was lower than the temperature corresponding to the high-temperature yield strength of G550 CFS. Furthermore, a steady-state creep rate expression of G550 CFS was proposed. When the primary creep stage of G550 CFS was insignificant, the proposed expression could be used to give the estimation of the high-temperature creep curves of G550 CFS. Finally, the transient-state test strain of G550 CFS at 500 °C was predicted and compared with previous experimental results. It was shown that the creep strain was an essential part of the total strain of G550 CFS under transient-state conditions, and also a key factor leading to the difference of strain results between the transient-state and steady-state tests.