Buckled Columns in Steel Frame Building Don't Lead to Progressive Collapse

 So weird!

At least two structural columns buckled and failed in a 37-story office tower in Midtown Manhattan on Tuesday, prompting evacuations of nearby streets and buildings. While city officials asserted that the tower was in no danger of collapsing completely, outside engineers said further failures in the structure could not be ruled out. 

A pair of columns that failed completely were part of the tower’s existing structure. A New York Times review of images and videos from inside the building has found that several floors were added atop these columns. 

Recently added structure East 42nd St. Area detailed in photograph below Second Ave. Existing part of the building Photograph taken from here RECENTLY added structure Sagging floors above Missing facade panel 

Buckled columns visible inside existing structure Existing structure The New York Times City officials said in a news conference on Tuesday that the building was continuing to move, while they simultaneously assured the city that the building would not suffer “total collapse.”

 

“The way this building is constructed, it’s a steel-frame building,” John Esposito, a chief in the Fire Department in New York, said at the afternoon news conference. “So, it would not be a total collapse. It would be more of a localized collapse.”

 

Still, he said, “that remains our concern, that it’s moved.” Engineers said that the movement itself was cause for concern. In a properly designed steel building, they said, loads should redistribute quickly to surviving structural supports if columns failed. 

Joe DiPompeo, a former president of the Structural Engineering Institute at the American Society of Civil Engineers, said that if the structure had been overloaded, he would expect any movement “to happen very quickly,” rather than gradually. “Generally when a column buckles, it’s a sudden failure,” Mr. DiPompeo said. He said that a full collapse remained unlikely given the redundancies built into the building codes. 

Engineers often refer to the most dangerous possibility as a progressive collapse, a process in which structures near the initial failure become overstressed and also fail, potentially bringing down the building if the sequence continues. While unlikely, it cannot be ruled out, Mr. DiPompeo said. Footage recorded from inside the building shows at least two structural columns appear to have failed completely, Mr. DiPompeo said. Other nonstructural, interior walls — or at least the metal “studs” that were in place to hold them up — also appear to have deformed.