Finite element analysis of creep for plane steel frames in fire

Abstract

Steel is widely used for the construction of bridges, buildings, towers, and other structures because of its great strength, light weight, ductility, and ease of fabrication, but the cost of fireproofing is a major disadvantage. Therefore, the resistance of a steel structure to fire is a significant subject for modern society. In the past, for simplification, creep behavior was not taken into account in research on the resistance of a steel structure to fire. However, it was demonstrated that the effect of creep is considerable at temperatures that commonly reach 600°C and should not be neglected in this context. In this paper, a co-rotational total Lagrangian finite element formulation is derived, and the corresponding numerical model is developed to study the creep behavior of plane steel frames in fire conditions. The geometric nonlinearity, material nonlinearity, high temperature creep, and temperature rate of change are taken into account. To verify the accuracy and efficiency of the numerical model, four prototypical numerical examples are analyzed using this model, and the results show very good agreement with the solutions in the literature. Next, the numerical model is used to analyze the creep behavior of the plane steel frames under decreasing temperatures. The results indicate that the effect of creep is negligible at temperatures lower than 500°C and is considerable at temperatures higher than 500°C. In addition, the heating rate is a critical factor in the failure point of the steel frames. Furthermore, it is demonstrated that the deflection at the midpoint of the steel beam, considering creep behavior, is approximately 13% larger than for the situation in which creep is ignored. At temperatures higher than 500°C, the deformed steel member may recover approximately 20% of the total deflection. The application of the numerical model proposed in this paper is greatly beneficial to the steel industry for creep analysis, and the numerical results make a significant contribution to the understanding of resistance and protection for steel structures against disastrous fires.

Keywords

creep / plane steel frame / fire / finite element method / geometric nonlinearity

References

[1] Saab H A, Nethercot D A. Modeling steel frame behavior under fire conditions. Engineering Structures, 1991, 13(4): 371–382

[2] Richard L, Tang L K, Holmaas T. Advanced analysis for the assessment of steel frames in fire. Journal of Constructional Steel Research, 1998, 47(8): 19–45

[3] Wang Y C, Moore D B. Steel frames in fire-analysis. Engineering Structures, 1995, 17(6): 462–472

[4] Bailey C G, Burgess I W, Plank R J. Analyses of the effect of cooling and fire spread on steel-framed buildings. Fire Safety Journal, 1996, 26(4): 273–293

[5] Bailey C G. The influence of the thermal expansion of beams on the structural behavior of columns in steel-frames structures during a fire. Engineering Structures, 2000, 22(7): 755–768

[6] Wang P J, Li G Q, Guo S X. Effects of the cooling phase of a fire on steel structures. Fire Safety Journal, 2008, 43(6): 451–458

[7] Lin T J, Yang Y B, Huang C W. Inelastic nonlinear behavior of steel trusses cooled down from a heating stage. International Journal of Mechanical Sciences, 2010, 52(7): 982–992

[8] Huang Z F, Tan K H. Fire resistance of compartments within a high-rise steel frame: New sub-frame and isolated member models. Journal of Constructional Steel Research, 2006, 62(10): 974–986

[9] Huang Z F, Tan K H, Ting S K. Heating rate and boundary restraint effects on fire resistance of steel columns with creep. Engineering Structures, 2006, 28(6): 805–817

[10] Huang Z H, Burgess I W, Plank R J. Three-dimensional analysis of composite steel-framed buildings in fire. Journal of Structural Engineering, 2000, 126(3): 389–397

[11] El-Rimawi J A, Burgess I W, Plank R J. The treatment of strain reversal in structural members during the cooling phase of a fire. Journal of Constructional Steel Research, 1996, 37(2): 115–135

[12] Huang Z F, Tan K H. Effects of external bending moments and heating schemes on the responses of thermally restrained steel columns. Engineering Structures, 2004, 26(6): 769–780

[13] Li G Q, Guo SX. Analysis of restrained heated steel beams during cooling phase. Steel and Composite Structures, 2009, 9(3), 191–208

[14] Li G Q, Wang P, Hou H. Post-buckling behaviours of axially restrained steel columns in fire. Steel and Composite Structures, 2009, 9(2), 89–101

[15] Tan K H, Ting S K, Huang Z F. Visco-elasto-plastic analysis of steel frames in fire. Journal of Structural Engineering, 2002, 128(1): 105–114

Acknowledgment

This work was sponsored by the National Natural Science Foundation of China (Grant No. 10972162). This support is gratefully acknowledged.

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg