Warren Lowe, Rocky Mountain News, November 29, 1961
A Denver engineering firm dipped back in history about 300 years to come up with a solution for the theater now under construction in the $3 million student center at Colorado State University, in Ft. Collins.
The result is the "camp stool" design of the pre-pressed concrete supports for the walls and roof supports of the theater, now about half completed.
James M. Hunter, Boulder architect, designed the theater to obtain the best possible acoustical qualities. A stage whisper, he said, will be heard in the last row as plainly as in the first.
The curing roof and ceiling, called a catenary, is higher at the back than the front, where it dips above the orchestra pit. The design presented structural engineering problems.
Ib Falk Jorgensen Consulting Engineers, Denver, structural consultant for Hunter, worked out the solutions.
"The catenary principle dates back to Galileo," Jorgensen said Tuesday. "It's somewhat like a chain, anchored at both ends with a long drop between.
"For the CSU theater, the catenary design resulted in what Hunter calls the 'camp stool shape' reinforced concrete support, which will support the corners, but not the full weight of the roof.
"The root is 105 by 122 feet and is of 4.5 thick concrete. With the natural tendency of the shape to sag and pull in the end walls, this size and weight, plus anticipated snow-loads and the effects of wind, presented some engineering problems," Jorgenson said.
The tendency to sag would result in deflection of an estimated 4.5 inches, enough to crack corners.
The deflection will be reduced to an insignificant 1-10th of an inch by the use of pre-stressed and post-stressed cables through the concrete.
Supporting the roof weight is an inverted concrete arch, which causes all resultant forces to be vertical.
General contractor on the building, which as started last summer and is scheduled for completion in the spring 1962, is Hensel Phelps Construction Co. of Greely.