Abstract
The American Institute of Steel Construction provides design equations for the lateral torsional buckling (LTB) of beams under fire. However, these equations are limited only to prismatic beams. Stepped beam factors are introduced by researchers that accounts the change in cross-sections of beams to determine capacities of stepped beams under normal temperatures. This paper assesses the validity of the stepped beam factors for the LTB capacities of stepped I-beams located at its midspans integrated to the AISC equation for beams under high temperatures. A set of numerical studies using finite element analysis program, ABAQUS, was conducted to assess the buckling behavior of stepped beams. The analysis is composed of heat-transfer analysis that evaluates the change in material properties of steel as heat propagates the material from 20 °C to 800 °C; and Static Riks analysis where the beams are applied with uniform end moments. Correlation between the results from the stepped beam equations and the simulated data from ABAQUS has been done. The comparison between data showed that the proposed equation generated conservative estimates with an average percentage difference of 11.48% for inelastic LTB, whilst, 2.07% for the elastic LTB. In addition, the ratio of the increase in strength and increase in volume of stepping of beams shows that the flange width of the stepped beam controls its efficiency in lateral torsional buckling capacity. Overall, the results of this research proved that the existing stepped beam equations can be used in calculating the structural capacity of stepped beams at midspan under both normal and elevated temperatures.
Similar content being viewed by others
References
Alolod, S., & Park, J. S. (2018). Inelastic buckling strength of stepped I-beams at midspan subjected to uniform bending. Journal of Korean Society Hazard Mitigation, 18(5), 185–192.
ANSI/AISC 360–16 (2016) Specification for structural steel buildings. American institute of steel construction, Chicago, Illinois.
Avery, P., & Mahendran, M. (2000). Distributed plasticity analysis of steel frames structures comprising non-compact sections. Engineering Structures, 22, 901–919.
Couto, C., Vila Real, P., Lopes, N., & Zhao, B. (2016). Numerical investigation of the lateral-torsional buckling of beams with slender cross sections for the case of fire. Engineering Structures, 106, 410–421.
Dassault Systems (2016) ABAQUS/CAE 2016: Analysis user’s guide. Johnston, USA
EN 1993 (2005) Eurocode 3. Steel structures, Europe
Hanus, F., Vassart, O., Caillet, N., & Franssen, J. M. (2017). High temperature full-scale test performed on S500M steel grade beams. Journal of Constructional Steel Research, 133, 448–458.
Mesquita, L. M. R., Piloto, P. A. G., Vaz, M. A. P., & Vila Real, P. M. M. (2005). Experimental and numerical research on the critical temperature of laterally unrestrained steel I beams. Journal of Constructional Steel Research, 61, 1435–1446.
Park, J. S. (2002). Lateral torsional buckling of prismatic beams with continuous top flange bracing. Journal of Constructional Steel Research, 60(2), 147–160.
Park, J. S., & Stallings, J. M. (2003). Lateral-torsional buckling of stepped beams. Journal of Structural Engineering, 129(11), 1457–1465.
Santos, R. R., Kang, J. S., & Park, J. S. (2017). Elastic buckling assessment of doubly symmetric I-beams with singly stepped section at midspan. Journal of Korean Society Hazard Mitigation, 17(6), 301–312.
Takagi, J., & Deierlein, G. G. (2007). Strength design criteria for steel members at elevated temperatures. Journal of Constructional Steel Research, 63, 1036–1050.
Trahair, N. S., & Kitipornchai, S. (1971). Elastic lateral buckling of stepped I-beams. ASCE Journal of Structural Engineering, 97(10), 2535–2548.
Vila Real, P. M. M., & Franssen, J. M. (2001). Numerical modeling of lateral-torsional buckling of steel i-beams under fire conditions: Comparison with eurocode 3. Journal of Fire Protection Engineering, 11(2), 112–128.
Vila Real, P. M. M., Piloto, P. A. G., & Franssen, J. M. (2003). A new proposal of a simple model for the lateral-torsional buckling of unrestrained steel I-beams in case of fire: Experimental and numerical validation. Journal of Constructional Steel Research, 59, 179–199.
Yin, Y., & Wang, Y. C. (2003). Numerical simulations of the effects of nonuniform temperature distributions on lateral torsional buckling resistance of steel I-beams. Journal of Constructional Steel Research, 59, 1009–1033.
Acknowledgements
This work was supported by the National Research Foundation (NRF) of Korea grant funded by the Korea government (Ministry of Science and ICT) (No. 2019R1F1A1060708).
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Alolod, S., Park, J. & Won, D. Lateral Torsional Buckling Strengths of Stepped Beams at Midspan Exposed to Elevated Temperature. Int J Steel Struct 20, 2028–2037 (2020). https://doi.org/10.1007/s13296-020-00427-0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s13296-020-00427-0