Behaviour, design, and reliability of monosymmetric I-beams at elevated temperature

Abstract

Steel is the preferred choice among structural designers because of its exceptional properties compared to other available materials. However, steel is vulnerable to fire risk, as its material characteristics deteriorate rapidly at high temperatures. It results in the instability and failure of unsupported flexural components. In the present study, a numerical analysis is conducted to explore how load patterns and temperatures impact the failure characteristics of monosymmetric I-section beams. The numerical model is validated using existing experimental tests conducted at elevated temperatures. Subsequently, the validated model is employed for the numerical study. The analysis uses the ABAQUS software. The study is conducted for beam lengths ranging from 2.5 to 20 m, incorporating different degrees of monosymmetry. The behaviour of the beams is evaluated under steady and transient-state thermal conditions, using ISO 834 fire, considering uniform/non-uniform loading patterns on the beam. The results highlighted the shortcomings in Eurocode 3 provisions related to the failure patterns of monosymmetric I-beams, particularly for cases involving point loads and uniform moments. Subsequently, a proposed new methodology for calculating design capacity for monosymmetric beams is adopted from past literature and evaluated to ensure its reliability and accuracy in predicting monosymmetric beam capacities at elevated temperatures.