Structural Response of a Generic Steel Frame Exposed to Travelling Fires

Abstract

A design tool called Travelling Fires Methodology (TFM) [1] has been developed in recent years to account for travelling fires in large open-plan compartments. However, there has been little research carried out to understand the structural response of buildings subjected to such fires. The aim of this study is to investigate the behavior of a 10-story steel frame under travelling fires and compare it to the behavior under standard design fires. Each floor of the frame is subjected to four travelling fire scenarios and two Eurocode parametric temperature-time curves (‘short-hot’ and ‘long-cool’) using finite element software LS-DYNA. In total 60 fire scenarios are considered. Results show oscillations of axial forces and bending moments for the smallest travelling fire sizes, which are not observed for the parametric fires. In general the development of stresses and displacements within heated beams is found to follow similar trends irrespective of the frame level at which a fire occurs. For the investigated frame the critical fire scenarios are found to occur on the upper floors of the frame where column sections reduce in size. It has been found that depending on the structural metric examined both travelling fires and parametric fires can result in the most severe scenario. Therefore, it is highlighted that in the structural design for fires, in addition to the standard tools it is important to consider more realistic fire scenarios associated with travelling fires as they might trigger previously unnoticed structural mechanisms.