Hi, Folks -

USA Today article:

Atlanta bridge collapse shows how fire defeats concrete, steel
https://www.usatoday.com/story/news/2017/03/31/atlanta-bridge-collapse-shows-how-fire-defeats-concrete-steel/99877148/

Excerpts (bolding added):

[snip]

Intense fire can damage both the concrete that serves as the road deck and the support piers for the bridge, as well as the steel that reinforces the concrete. Even if a bridge doesn’t collapse in a fire, the damage can leave concrete crumbling and the steel warped and weak.

“The heat can damage the concrete and cause the reinforcing steel to lose strength, and that can cause the bridge to fall down,” said Andy Herrmann, a past president of the American Society of Civil Engineers and a 40-year consulting engineer in New York City.

Concrete starts to crack at 500 degrees, suffers large cracks at 1,000 degrees and melts at 2,500 degrees, he said.

Larry Petrick, deputy director for occupational safety and health for the International Association of Fire Fighters, said steel is unprotected in bridge construction and isn't immune to fire.

A 50-foot beam could expand 4 inches when heated to 1,000 degrees, he said. After cooling down, the beam loses 50% of its strength, he said. The weight of concrete loaded on top of the steel adds additional stress, which leads to failure and collapse, he said.

“The steel may begin to twist or warp,” Petrick said. “This was a large, high-temperature fire under the bridge, with its structural members directly exposed to the steel.”

[snip to end]

Full article:

https://www.usatoday.com/story/news/2017/03/31/atlanta-bridge-collapse-shows-how-fire-defeats-concrete-steel/99877148/

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