Effect of imperfections and thermal gradients on thermo-mechanical response of hollow aluminum columns subjected to fire

Abstract

Purpose: This work numerically investigates the effects of geometric imperfections and thermal gradients on thermo-mechanical response of hollow aluminum columns (aluminum 5083-H116 alloy) subjected to fire. From the analysis, a reduction factor is proposed to estimate the load-carrying capacity of the columns having imperfections and thermal gradients.

Design/methodology/approach: Finite Element (FE) simulations were performed using ABAQUS, with the numerical model validated against experimental and verified against numerical results reported in the literature. This study employed the temperature profiles obtained from thermal analysis as input for the mechanical model to predict failure mechanisms at different exposure times in a sequentially coupled approach.

Findings: It was found that the relative position of heating and initial geometric imperfection had a significant effect on the failure mechanism of the columns. Further, the load-carrying capacity of the columns from the simulations was compared with the analytical load-carrying capacity and a reduction factor was proposed, which can be used to calculate the load-carrying capacities of the columns having imperfections and thermal gradients.

Research limitations/implications: Imperfections can not be discarded while designing columns. In real fire scenarios, the columns are heated non-uniformly. The failure mechanism of columns will differ for different exposure sides relative to the geometric imperfections. This study will enable the basis for analyzing the effects of imperfections and thermal gradients on the load-carrying capacity of the columns, and the proposed reduction factor may serve as the basis for designing the aluminum hollow columns in case of non-uniform heating scenarios with imperfections.

Practical implications It was found that for the same column, the relative position of initial geometric imperfection and heating has a significant effect on the failure mechanism. It is essential to consider the potential consequences of this effect in the design process of aluminum hollow columns. Even in the case of facade fires, in most scenarios, the fire grows from inside to outside of the compartment. In that situation, the same aluminum frame is exposed from different sides.

Originality/value: This is the first detailed investigation of the effect of the relative position of initial geometric imperfection and heating side on the failure mechanism and load-carrying capacity of aluminum hollow columns. A reduction factor is proposed to calculate the load-carrying capacity of the columns with imperfections and thermal gradients.