Elevated Temperature Effect on the Dynamic Characteristics of Steel Columns and Frames

Abstract

Fire performance of load bearing elements in steel buildings such as columns and frames has major importance for structural designers. This study aims to assess the elevated temperature effect on dynamic characteristics of steel columns and frames by conducting sequential heat transfer and modal analyses. A series of finite element analyses including heat transfer analysis aere performed on 62 different steel columns and frames. Three-hour part of ISO 834 fire curve is taken into consideration in the analysis. Modal analyses are conducted for the purpose of providing a more comprehensive image of dynamic characteristics in specific duration of elevated temperature. The presented study accommodates the effect of various steel profile types, cross-sectional dimensions and exposure durations on changes in dynamic characteristics. The outcomes of the performed parametric study revealed the decrease in natural frequencies with the temperature growth. The research has also shown the existence of a correlation between temperature variations and changes in mode shapes. The change in mode shapes depends on the profile type. Mode shapes do not change depending on the temperature in some profile types, while in some profile types they change after a certain temperature. The obtained results of the performed sequential analyses are presented in forms of tabulated data and approximate formulas. They can facilitate the damage detection process and contribute in required structural health monitoring measurements while enhance the accuracy of damage assessment for fire exposed steel structures.