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A simple and direct analytical formula has been derived to determine the compressive resistance of steel columns subjected to fire conditions. The approach is based on the Rankine principle, which allows the strength and the stability of a steel column at a particular temperature to be separately determined. Here, the evaluation of column strength is based on the rigid-plastic theory, while the stability consideration is based on the elastic-buckling theory. By considering the two factors in this manner, the proposed approach allows for their interaction. One important feature is that the same analytical formula can be used for both axially and eccentrically loaded columns. In addition, the proposed formula does not require any calibrations against test data. The proposed formula has been verified against a set of published column test results and other analytical predictions. The comparison study shows consistently good agreement with both the test and the analytical results.

Chromium steel surface deposits were postheated to 350 degrees Celsius. For fatigue crack growth threshold values of the stress intensity factor between 11-13 MPa m(superscript 1/2), three different propagation kinetics were observed, suggesting that environmental factors affect crack growth. Fracture toughness is dependent on vanadium or columbium content and more of both will decrease fracture toughness.