Vulnerability of structures to collapse during the decay phase of a fire

Abstract

When a fire develops in a building, it leads to an increase in the temperature until reaching a peak and then is followed by a decrease and return to ambient temperature. Until now fire engineering has mainly focused on the effect of heating phase on structures, using standardize fire models that consist of continuously increasing temperature over time. As a direct consequence, the knowledge about the structural behavior during the cooling phase of a fire is very limited.

The objective of this work is the investigation of the behavior of structures when subjected to the full course of natural fires, until burnout, in particular referred to their response based on the variation of certain parameters such as fire severity, applied load and element geometry. The study aim it is addressed by performing different parametric analysis upon frames made of different typology and constituting material such as Steel and Concrete. The nonlinear finite element software used to perform the numerical analysis it is validated using data from a study upon a real steel tested structure.

The work is mainly focused on steel structure for which there were a support of data from a real tested structure respect to concrete. The main founding regarding the structural response during the decay phase of the fire, are enhancing the actual knowledge on the topic, showing for example how based on the structure geometry it is possible to have different structural response that lead to local or global structural failure. The different ways to fail and behave underlining the structural vulnerability related to the parameter adopted.