Importance of Time-Dependent Material Behavior in Predicting Strength of Steel Columns Exposed to Fire

Abstract:

One of the critical factors affecting the strength of steel columns at elevated temperatures is the influence of material creep. Under fire conditions, steel columns can exhibit creep buckling, a phenomenon in which the critical buckling load for a column depends not only on slenderness and temperature, but also on the duration of the applied load. This paper will propose a preliminary methodology to study the phenomenon of creep buckling in steel columns subjected to fire. Analytical solutions using the concept of time-dependent tangent modulus are developed to model time-dependent buckling behavior of steel columns at elevated temperatures. Results from computational creep buckling studies using ABAQUS^® are also presented, and compared with analytical predictions. Both analytical and computational methods utilize material creep models for structural steel developed by Harmathy, and by Fields and Fields. The analytical and computational results clearly indicate that accurate knowledge of material creep is essential in studying creep buckling phenomenon at elevated temperatures, and that neglecting creep effects can lead to potentially unsafe predictions of the strength of steel columns subjected to fire.

• Periodical: Applied Mechanics and Materials (Volume 82)
• Pages: 350-355
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.82.350
• Online since: July 2011
• Authors: Mohammed Ali Morovat, Michael D. Engelhardt, Eric M. Taleff, Todd Helwig
• Keywords: Creep Buckling, Fire, Steel Columns, Time-Dependent Tangent Modulus

References

[1] F.H. Norton: The Creep of Steel at High Temperatures (McGraw-Hill Inc., New York 1929).

[2] R.W. Bailey, Creep of Steel under Simple and Compound Stress: Engineering, Vol. 121 (1930), p.265.

[3] J.E. Dorn, Some Fundamental Experiments on High Temperature Creep: Journal of the Mechanics and Physics of Solids, Vol. 3 (1954), p.85.

[4] T.Z. Harmathy, A Comprehensive Creep Model: Journal of Basic Engineering, Trans. ASME, Vol. 89 (1967), No. 3, p.496.

[5] B.A. Fields and R.J. Fields, Elevated Temperature Deformation of Structural Steel: Report NISTIR 88-3899, NIST, Gaithersburg, MD, (1989).

[6] C. Zener and J.H. Hollomon, Effect of Strain Rate on the Plastic Flow of Steel: Journal of Applied Physics, Vol. 15 (1944), p.22.

DOI: 10.1063/1.1707363

[7] A.M. Freudenthal: The Inelastic Behavior of Engineering Materials and Structures (John Wiley & Sons Inc., New York 1950).

[8] J. Marin, Creep Deflections in Columns: Journal of Applied Physics, Vol. 18 (1947), p.103.

[9] F.R. Shanley: Weight-Strength Analysis of Aircraft Structures (1st Edition, McGraw-Hill Inc., New York 1952).

[10] J. Singer, J. Arbocz and T. Weller: Buckling Experiments: Experimental Methods in Buckling of Thin-Walled Structures (Volume 2, John Wiley & Sons Inc., New York 2002).

DOI: 10.1002/9780470172995

[11] M.A. Morovat, J. Lee, G. Hu and M.D. Engelhardt, Tangent Modulus of ASTM A992 Steel at Elevated Temperatures: Proceedings, Sixth International Conference on Structures in Fire (SiF' 10), Michigan State University, East Lansing, Michigan, June 2-4 (2010).

DOI: 10.1061/41031(341)118

[12] Eurocode 3, Design of steel structures. Part 1-2: General rules. Structural fire design: EN 1993-1-2, European Committee for Standardization, CEN, (2006).

DOI: 10.1002/9783433601570.oth1