Understanding the progressive collapse of steel structures under fire conditions is crucial for the safety and resilience of modern buildings. In their critical review, "Progressive Collapse of Steel Structures Exposed to Fire," Cao et al. comprehensively analyze the factors influencing structural integrity and the current state of research in this vital area. This publication is highly recommended for structural engineers seeking to deepen their understanding and improve their practice.

Key Insights from the Review

Fire Resistance of Steel Structures

 Historical fire tests, such as the Broadgate and Cardington fires in the 1990s, have practical implications for the design of steel structures. These tests demonstrated that steel components in multi-story structures exhibit more excellent fire resistance than isolated components tested under standard conditions, thanks to more realistic member dimensions, boundary conditions, and fire scenarios.

Impact of the World Trade Center Collapse

The collapse of the World Trade Center in 2001 was a pivotal event that reshaped our understanding of fire resistance in structures. It underscored the inadequacy of prescriptive fire resistance ratings in ensuring a building's overall safety, sparking a significant increase in interest in understanding how structures behave under extreme conditions like fire, blast, and impact.

Defining Progressive Collapse

Progressive collapse is described as the spread of an initial local failure from one element to another, ultimately leading to the collapse of an entire structure or a disproportionately large part. This definition emphasizes the importance of preventing global collapse even if local failures occur.

Research and Simulation:

Due to practical and safety constraints, much of the research on fire-induced progressive collapse relies on numerical simulations. These simulations are essential for investigating the collapse behavior of high-rise structures under fire conditions, as large-scale physical experiments are often not feasible.

Experimental Validation

Although numerical simulations are invaluable, experimental validation remains critical. Existing experiments typically focus on low-rise structures and various structural types, including framed structures, portal frames, and truss structures. However, there is a pressing need for more large-scale tests to validate numerical models accurately.

Influencing Factors

The review highlights several key factors that influence the collapse mechanism of steel structures in fire, including load ratios, the strength of structural members, fire scenarios, fire protection, and bracing systems.

Practical Implications for Structural Engineers

For practicing structural engineers, Cao et al.'s review offers several practical takeaways

Holistic Design Approach Engineers should adopt a holistic approach to fire safety, considering the entire building system rather than just individual components.

Redundancy and Robustness Designing structures with redundancy can help prevent progressive collapse by ensuring that the failure of a single element does not lead to catastrophic outcomes.

Advanced Simulations Utilizing numerical simulations can provide valuable insights into how structures will behave under fire conditions, aiding in developing safer designs.

Continuous Learning Staying informed about the latest research and experimental findings is crucial for improving structural engineering fire safety standards and practices.

Conclusion

Cao et al.'s "Progressive Collapse of Steel Structures Exposed to Fire: A Critical Review" is an essential read for structural engineers dedicated to enhancing building safety and resilience. By understanding the complex interplay of factors that influence progressive collapse, engineers can better design structures that withstand extreme conditions.

References

https://www.sciencedirect.com/science/article/abs/pii/S0143974X23002122