Proposal of steel stress-strain relationships and simple analytical models of beams considering strain-rate effects at elevated temperatures
Journal of Structural Fire Engineering
Article publication date: 8 April 2022
Issue publication date: 15 February 2023
In this study, engineering stress-strain relationships considering an effect of strain rate on steel materials at elevated temperatures were formulated and a simplified analytical model using a two-dimensional beam element to analytically examine the effect of strain rate on the load-bearing capacity and collapse temperature was proposed.
The stress-strain relationships taking into account temperature, strain, and strain rate were established based on the past coupon test results with strain rate as the test parameter. Furthermore, an elasto-plastic analysis using a two-dimensional beam element, which considered the effect on strain rate, was conducted for both transient- and steady-state conditions.
The analytical results agreed relatively well with the test results, which used small steel beam specimens with a rectangular cross-section under various heating rates (transient-state condition) and deformation rates (steady-state condition). It was found that the bending strength and collapse temperature obtained from the parametric analyses agreed relatively well with those evaluated using the effective strength obtained from the coupon tests with strain equal to 0.01 or 0.02 under the fast strain rates.
The effect of stress degradation, including the stress-strain relationships at elevated temperature, was mitigated by considering the effect of strain rate on the analytical model. This is an important point to consider when considering the effect of strain rate on steel structural analysis at elevated temperatures to maintain analytical stability unaccompanied by the stress degradation.
The authors are thankful for the funding from Grant-in-Aid for Scientific Research (C), The Japan Society for the Promotion of Science (JSPS), and many excellent advices from Prof. Dr. Markus Knobloch, Ruhr-University Bochum, which helped to significantly improve this paper.
Ozaki, F. and Umemura, T. (2023), "Proposal of steel stress-strain relationships and simple analytical models of beams considering strain-rate effects at elevated temperatures", Journal of Structural Fire Engineering, Vol. 14 No. 1, pp. 90-113. https://doi.org/10.1108/JSFE-01-2022-0001
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