On September 14, 1970, the gymnasium ot The Tucker High School in Hennison Virginia, a four element hyperbolic paraboloidal roof structure collapsed. The structure was 155 ft. by 162 ft in plan. The following photographs were borrowed from Engineering News Record, Sept. 24. 1970.

Hypar failure

The collapse was complete, as you see, and there were injuries to the school children. I was called in by the investigating firm, Wiss, Janney, and Elsner to give my opinion. After tests on materials and further analysis, the conclusion was that the failure was due to progressive deflection caused by the eccentricity of the compressive forces in the central ridge members. Three other similar structures were subsequently torn down. I looked at one of them that had a deflection of 18 inches at the center.

It was a good ten years before it finally occurred to me what the real design fault was. It shows that when you design shells, all your normal design instincts flee. The center point should have been cambered upward . We designed a similar structure in Colorado Springs in 1962 except that it was 185 ft. in plan. The Owner proposed to hang a heavy curtain from the ridge member, so we carefully prestressed it as well as all edge members. This structure has had no problems and is in excellent condition.

This comment was received from a reader in December 2007:

Correction to Milo Ketchum's web archive... http://www.ketchum.org/-milo/failure.html

Tucker High School is in Henrico County, a suburb of Richmond, Virginia, not Hennison (which I've never heard of). I was a student at Henrico High School (from 1962-1968) which was built at the same time and same architecture as Tucker HS. In fact, it is the Henrico HS gym pictured in the "before" photo. Construction of the Henrico HS gym was still in progress when I started the 7th grade, as the contractor was behind schedule. I watched the construction right outside my classroom window. Whenever I think back to all the gym classes I attended there, and all the basketball games with thunderous cheering and bleacher stomping, I shudder to think how close to death we all were. There was a third high school, Varina HS, in eastern Henrico County, also built at the same time and same architecture. After the Tucker collapse, all three gyms were demolished and rebuilt in a boxy, traditional style.

-Jim Garner

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