Letters to the Editor
Lift slab construction method involves hazards for firefighters
The recent fatal collapse of a concrete building under construction in Bridgeport, Conn., that took 28 lives has focused attention on the lift slab method of construction and the problems associated with it.
Lift slab construction, also known as the “Youtz-Slick” method, was first used for the construction of Trinity University in San Antonio, Texas.
In this type of construction, the ground floor slab is cast first. The other floor slabs and the roof are cast on top of the ground floor slab. Bond breakers are used between the slabs so they won’t adhere to each other. When the slabs are up to design strength, they’re raised up the columns by hydraulic jacks that are on top of the columns. (Note that most newspaper accounts of the Bridgeport tragedy incorrectly referred to “steel beams.”) All the jacks are controlled from a central console. As each slab reaches its final position, it’s temporarily connected to the columns until final connections can be made.
Although many construction accidents have occurred when slabs were in the process of being lifted, in some cases, failures have occurred when there was no lifting being done. Reportedly, this was the case in the Bridgeport collapse.
Here are some other instances involving failures that occurred under both conditions:
- A Cleveland garage under construction was almost completed. Steel collars were cast into the floors to be welded to the columns. They were temporarily wedged when high winds struck in the area. The structure was seven feet out of plumb but was successfully jacked and pulled back to plumb. The floors were to be welded to the columns.
- In San Mateo, Calif., a roof slab was being lifted 16 feet. The columns weren’t braced, only bolted to the foundations. As the slab reached the top of the structure, the columns were three inches out of plumb. As the attempt was made to pull the slab back into place, it collapsed. The designer attributed the failure to the lack of bracing and the lateral shifting of the slab.
- Early press reports from the Bridgeport incident indicated that a lack of bracing might have been responsible for that collapse.
- In 1962, in Fort Worth, Texas, a seven-story structure that was under construction and almost completed suddenly collapsed. There were no witnesses to this incident.
As I pointed out in “Wooden Structures High in the Sky” [see Fire Engineering, April 1987], it’s imperative that fire suppression forces be up to the minute on the state of all buildings under construction. But they should be especially up to the minute on the state of those buildings where progressive collapse is almost inevitable. It’s quite reasonable for fire department members to refuse to enter into or under such a structure until they’re absolutely certain all the floor/column connections are permanent.
Francis L. Brannigan
Author, Building Construction for the
Fire Service Port Republic, Md.
Reader offers praises for “Life Hazard’’ editorial
The prose you display in your April editorial [“Firefighters, Too, Are a Life Hazard”] is professional sincerity. I’m sure all of your readers will feel likewise. Keep up the excellent work!
Mike Laffey Director Life Safety
Prudential Insurance Co.
Newark, N.J.
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