Analysis of the Influence of Time Dependent Strain on the Load Bearing Capacity of Aluminium Columns Exposed to Transient Heating

Abstract

This dissertation presents the analysis of the influence of creep strain on the critical speed and failure temperature of EN AW 6082 T6 aluminium columns exposed to transient heating. The model of transient heating represents an increase in temperature due to a constant load and thus simulates the real situation caused by fire. Current regulations for the design of aluminium structures exposed to fire do not include a detailed description of the development of creep strain and its influence on the reduction of load-bearing capacity and the rate of failure of the columns. Considering the significant increase in the use of aluminium and aluminium alloys in construction over the last fifty years, it is necessary to obtain a solid conclusion on the influence of creep on aluminium columns which stands for the most sensitive part of the structure. The biggest disadvantage of aluminium is its sensitivity to high temperatures since its material characteristics decrease already at temperatures above 100 °C, supporting the idea of this research. In the opening section of the research presented in this dissertation, the calibration of experimental results was carried out on test coupons of aluminium alloy EN AW 6082 T6 with the aim of obtaining parameters for the selected creep model. The calibrated creep model was applied to the experimental-numerical analysis of dominantly pressure-loaded aluminium columns exposed to transient heating. For transient tests, a low heating rate was applied because it simulates the existence of some form of fire protection that is obligatory in today's constructions due to strict regulations. The final part of the dissertation includes a parametric analysis of the influence of low heating rates (1 °C/min – 5 °C/min) of regular columns of simple aluminium construction and a comparison of the influence of creep strain on the failure time of the columns. The aforementioned parametric analysis was performed on the basis of the adopted creep model based on the results of the study carried out on aluminium test tubes and aluminium columns.