Atlanta I-85 fire, collapse: How long until full access to damage?

Around 7 p.m. Thursday, crews were battling a massive fire on I-85 northbound just south of Ga. 400 when a section of the highway collapsed, officials said.

Fire officials extinguished it on Thursday night after it burned for more than an hour, fire officials said.

A bridge collapse of this type would be impacted by a combination of the fire temperature and duration of the fire, said Kim Kurtis, a professor in Georgia Tech’s school of civil and environmental engineering.

Kurtis is not familiar with the construction of this particular bridge, but generally speaking, “if this were a reinforced concrete structure, the fire would have had to burn long and hot to impact the steel (within),” she said Thursday night.

» PHOTOS: Atlanta I-85 fire -- Highway bridge collapses near Piedmont Road

“Once the temperature gets about one-third to half the temperature of the melting point of steel that’s when you start to see more significant decreases” in its stability.

Once safety officials are sure that the site is safe and fire is out, inspectors will be sent in, she said.

Then structural engineers can do analysis to understand what happened and how the remaining structure was impacted and what kind of repairs will be needed.

So how long could all of that take? “It’s too soon to tell, she said."