Doctor of Engineering, I graduated from Nagoya University in Mar. 25th, 2022. In my doctor course, I studied the reusabilities of cold-formed steel square hollow section after fire, which the type of cold-formed steel square hollow section is widely used in steel structures in Japan. On the other hand, I also studied the steel performance at high temperature and conducted a perfect Heat conduction analysis with C++ program for an unprotected steel beam placed inside dry wall. I want to find a post-doctor position in the study of steel in fire.
In my study, the Charpy impact energies of both the welded connections and cold-formed steel square hollow section are investigated at high-temperature and at the ambient temperature after fire. Based on the research results, we proposed that when a steel members were heated to the temperature above 700 ℃, if these members were extinguished by the water(water-cooling), it need pay more attention on the risk of brittle fracture on these member. Then for the air-cooled specimens of cold-formed steel, it is reported that when these member were heated to 200-400 ℃, the Charpy impact energies will decrease to a danger line (27J in Japan), because of the air-cooling.
Also, the post fire mechanical of the cold-formed steel square hollow section including the coupon tensile strength, flexure buckling strength and local buckling strength were be completed investigated. According to the test results, it was confirmed that both the residual flexural and local buckling strengths changed after the heating and cooling process. It is mostly because of the change from both yield strength and tensile strength. And the flexural buckling strength can be evaluated using the Eurocode equations based on the residual yield strength, local buckling strength can be evaluated using both the Eurocode equations and AS/NZS design equations based on the residual yield strength. However, in the actual fire, it is very difficult to accurately evaluate the temperature history of the steel column after a fire, since the yield strength of steel after fire is unknown. Therefore, it is recommended that the residual flexural and local buckling should be evaluated using the design standard strength (F-value) at ambient temperature to achieve a safe-side evaluation.
Finally, at the last Chapter of my doctor thesis, a prediction equation of the displacement of the column at high temperature and the residual displacement after fire is proposed to evaluate the displacement of the column during the whole heating and cooling process without considering the effect of the beam. However, the accuracy of the prediction equations has only been verified by the selected dimension and the actual stress-strain curves of the cold-formed steel square hollow section in the research. Therefore, more verification of the prediction equations is needed considering the dispersion of the actual cold-formed steel square hollow section.
Furthermore, besides my main research, I also conducted many high-temperature research on the steel, and conducted a heat conduction analysis. These study results have been also published. The following references are my publications including journals, international conference, and Japanese conference.
My main field is about the reusability of steel structures after fire, and in my sub-research, the performance of steel in fire, FEM analysis model, and Heat conduction model is also studied by both experiment and numeric analysis.