Designing Concrete Structures for Fire Safety

The aim of this SP is to present some of the latest research in the area of fire performance of concrete. The ten papers in this SP present state-of-the-art review and results from both experimental and numerical studies on the various aspects ranging from material properties at elevated temperatures to optimum solutions for overcoming spalling in HSC concrete members exposed to fire.

Fire represents one of the most severe conditions encountered during the lifetime of a structure and, therefore,the provision of appropriate fire safety measures for structural members is a major safety requirement in building design. The basis for this requirement can be attributed to the fact that, when other measures for containing the fire fail, structural integrity is the last line of defense.

Generally, concrete structural members exhibit good performance under fire situations. In most cases, structural members used to be made of conventional concretes, often referred to as normal-strength concrete (NSC). However, in the last two decades, there have been significant advances in concrete material technology. These advances have lead to new concrete types, often referred to as high-strength or high-performance concrete. The construction industry has shown great interest in the use of high-strength concrete (HSC) due to improvements in structural performance, such as high strength and durability, that it can provide, compared to conventional NSC. HSC is typically characterized by high strength, good workability, and durability. Studies show, however, that the performance of HSC is different from that of NSC, and may not exhibit the same level of performance in fire.

Furthermore, the spalling of concrete under fire conditions is one of the major concerns in HSC. Fire-induced spalling in concrete has been observed under laboratory and real fire conditions in HSC specimens. Spalling is theorized to be caused by the buildup of pore pressure during heating. HSC is believed to be more susceptible to this pressure buildup because of its low permeability compared to NSC. Data from various studies show that predicting the fire performance of HSC, in general, and spalling, in particular, is very complex because it is affected by a number of factors.

In the aftermath of the September 11 terrorist attacks on the World Trade Center and the Pentagon, several issues relating to building performance under extreme conditions (structural, material, fire) have come to the forefront. Since intense fires played a major role in the collapse of the Twin Towers of the World Trade Center and other buildings, the issue of material performance under extreme fire conditions has attracted significant attention from the research and engineering community. Consequently, a number of new research programs in structural fire safety area are leading to new design provisions and solutions for enhancing the fire resistance performance of steel structures.