What are negative effects of fire on steel structures?

Fire has significant negative effects on steel structures, primarily due to how heat alters the physical properties of steel. When steel is exposed to high temperatures, it experiences thermal expansion, which can lead to warping or deformation. As the temperature rises, the material begins to lose its strength and rigidity; for instance, structural steel can lose up to 50% of its load-bearing capacity at temperatures around 1,100 degrees Fahrenheit (593 degrees Celsius).

This loss of both rigidity and strength means that components of a steel structure may no longer effectively support loads as they were originally designed to do, potentially leading to structural failures in extreme situations. Therefore, recognizing these negative effects is crucial for emergency responders and engineers in assessing the integrity of a steel structure after a fire incident.