دانلود رایگان مقاله انگلیسی بررسی رفتار مکانیکی ستون های فولادی بخش I پس از افزایش دما - اشپرینگر 2018

Abstract.

This paper presents the experimental and numerical investigations on mechanical behavior of I-section steel columns after elevated temperature exposure. A total of twenty-six compression tests were carried out, in which one was under ambient temperature and the other twenty-five were under heating and cooling phase to study the influence of high temperature (400, 550, 700, 850, 1000C) and high temperature duration (0.5, 1, 1.5, 2, 2.5 h) on mechanical behavior of the specimens. The failure pattern, axial load versus strain relation, axial load versus displacement relation and ultimate strength of the specimens were presented and analyzed. The test results showed that, high temperature duration had limited influence on the ultimate strength and other mechanical behaviors of the specimens, while the ultimate strength decreases with the increase of the maximum temperature the specimens suffered and some other behaviors also changed. The failure pattern of specimens after high temperature did not change compared with that of specimens under ambient temperature. The finite element models that have the same geometry with the test specimens were set up to compare with the test specimens and the results predicted from finite element analysis showed good agreement with that measured in test. Therefore, parametric study was carried out to investigate the influence of different section geometry on the ultimate strength of I-section steel short columns after elevated temperature. A new relationship for the ultimate strength for I-section steel short columns after elevated temperature was developed and proved to be reliable and accurate. What’s more, the effect of slenderness ratio on the stability coefficient of the columns was also investigated in the parametric study.

5. Conclusions

This paper presents the experimental results and parametric analysis of I-section steel columns after reaching a high temperature. High temperature duration has limited influence on the ultimate strength of the I-section steel short columns. The residual strength of the I-section steel short columns decreases with the increase of the high temperature exposure, and the higher the specimen temperature is, the faster the ultimate strength declines. Both elevated specimen temperature and its duration have little influence on the initial stiffness, ductility coefficient and yield load to ultimate load ratio of I-section steel short columns, but the yield load decreases with the increase of the maximum specimen temperature. A formula for the ultimate strength of I-section steel short columns after high temperature treatment was proposed on the parameters of high temperature, height-to-thickness ratio of web and width-to-thickness ratio of flange. Parametric observations also infer that the failure modes of the columns are related to the slenderness ratio. When the slenderness ratio of the column was no more than 50, the column failed due to local buckling. When the slenderness ratio of the column was more than 50, the column failed due to global buckling. In addition, the effect of slenderness ratio on the stability coefficient of the columns after reaching a different elevated temperature is quite different. At last, based on the FEA, a new formula has been proposed to predict the stability coefficient of the columns after reaching elevated temperature.