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## The Failure of Highly Heated Cast-Iron Columns or Facades Cast iron is an older construction material that poses unique difficulties for firefighters. Cast iron is a very brittle material that has great compressive strength but almost no shear strength. Thus, it is unsuitable for use as beams, b...

## The Failure of Highly Heated Cast-Iron Columns or Facades Cast iron is an older construction material that poses unique difficulties for firefighters. Cast iron is a very brittle material that has great compressive strength but almost no shear strength. Thus, it is unsuitable for use as beams, but it was once a favorite material for columns and prefabricated walls. Its ability to be readily cast in a mold and then bolted together in sections made it the first material to be used for prefabricated buildings, such as the loft buildings built in the late 1800s. Unfortunately, when cast iron is highly heated and then suddenly cooled, as by a hose stream, it can shatter, causing failure of either the column or any cast-iron bearing walls. Either case could be catastrophic. Note: In his book, _Building Construction for the Fire Service_, NFPA, 1982, Professor Francis Brannigan disputes this explanation of cast-iron building collapses. Instead, he theorizes that flaws in the castings have resulted in many columns being much thinner on one side than on the other. Unequal rates of expansion due to the rise in temperature, therefore, could result in cracks in the column. An additional factor could be the force of a high-pressure stream striking what is known to be a brittle material. To replace the original 24-m.-thick bearing walls on the first floor of a renovated building, a catastrophic collapse is only 800 degrees away. That's all it takes for these columns to fail, dropping the entire load above.