An equivalent stress method to account for local buckling in beam finite elements subjected to fire
Journal of Structural Fire Engineering
ISSN: 2040-2317
Article publication date: 26 June 2019
Issue publication date: 19 August 2019
Abstract
Purpose
The purpose of this paper is to present an improved temperature-dependent constitutive model for steel that accounts for local instabilities of slender plates using an effective stress-based method. This model can be easily implemented for use with Bernoulli beam finite elements (FEs) in the fire situation.
Design/methodology/approach
The constitutive model is derived by calibration on parametric numerical analysis on isolated plates subject to buckling at different elevated temperatures. The model is implemented in the FE software SAFIR and validation is performed against experimental and shell element analysis results.
Findings
A constitutive model based on an equivalent stress method is proposed as an efficient way to consider local buckling in steel members exposed to fire. The proposed stress–strain–temperature relationship is asymmetric and is modified in compression only, by reducing the proportional limit, the yield stress and the strain at yield stress. The reduction of these parameters depends on the plate’s boundary conditions, slenderness and temperature. The validation of the proposed model shows good agreement over a range of profile dimensions, temperatures and steel grades.
Research limitations/implications
The model is still giving conservative results for large compressive load eccentricities. An enhanced model is under development to improve the predictive capability under large eccentricities.
Practical implications
The proposed model, easily implemented into any finite element software, allows using fibre type (Bernoulli) beam FEs for modelling structures made of slender sections. This has major practical implications as beam elements are the workhorse used for simulating the behaviour of structures in fire. This model, thus makes it possible to simulate large structures with slender steel sections at a limited computational cost.
Originality/value
The paper presents a novel steel constitutive model based on an innovative approach to capture local buckling at the material level using an equivalent stress approach. The theoretical development, validation and perspectives for future improvements are presented.
Keywords
Acknowledgements
This research was supported by the University of Liege and the EU in the context of the FP7-PEOPLE-COFUND-BeIPD project.
Citation
Maraveas, C., Gernay, T. and Franssen, J.-M. (2019), "An equivalent stress method to account for local buckling in beam finite elements subjected to fire", Journal of Structural Fire Engineering, Vol. 10 No. 3, pp. 340-353. https://doi.org/10.1108/JSFE-09-2018-0020
Publisher
:Emerald Publishing Limited
Copyright © 2019, Emerald Publishing Limited