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Why Did the Candle Factory Roof in Kentucky Collapse?

This is pure conjecture, but here is my hypothesis.

It is not unusual at all to see the roofs torn off of buildings, both homes and commercial properties, during a tornado. Even my wife, who was student teaching at the time, heard the wind come up and she went to these large glass school windows to shut them in the classroom she was in. Then, she saw a large tree topple over just outside of the building and then a roof come flying off of a college building close by — then, it dawned on her, “It is a tornado!”

In Kentucky, one survivor of the candle factory collapse who was interviewed described what happened. “The building swayed one way, then it swayed the other and maybe back again — then woomp! The roof collapsed all at once.”

I’m just guessing, but it could be that the building was constructed as a “concrete tilt-up structure.”

How or why would the entire roof collapse all at once? Coming from earthquake country, I know that with early versions of concrete tilt-up construction, during an earthquake the ground motions could cause the walls to separate from the roof, causing the roof to fall into the building. Sound familiar?

Here is a source with a more technical description: “Seismic vulnerability assessment of tilt-up concrete structures.” The vulnerability of these structures is well understood. But, but, but, for this particular building in Kentucky, how did the code for that local jurisdiction measure up against modern seismic standards, and that particular structure?

You can call it an “act of God,” but this is where building codes, building inspections, occupancy permits and liability come into play.

I’m not a seismic engineer or a tornado expert on the performance of buildings in an earthquake or a tornado. It is interesting to me that the “building swayed back and forth” and then the roof collapsed all at once. I’m sure reasons for the collapse will be studied, but the national news will never likely pick up the results of the study and conclusions. If anyone in Kentucky follows this story going forward, I’d be interested in the outcomes and findings.

Just remember, safe buildings start with zoning to keep building in hazardous areas. Then you need a modern building code and a robust inspection program to be sure the building is being built to code. All those elements have to be in place to ensure the safety of the people who live and work in the structure.
Eric Holdeman is a contributing writer for Emergency Management magazine and is the former director of the King County, Wash., Office of Emergency Management.