Biltmore Hotel

Biltmore Hotel

Seconds after the final warning signal blared Sunday afternoon at a downtown redevelopment site in Oklahoma City, precisely placed explosive charges dropped a 28-story building almost in its tracks. When it fell, the 245-ft-high structure became the tallest steel-frame building to be demolished with explosives.

Built in 1932 of heavy beams and beefed-up steel columns, the Biltmore Hotel stood in the way of a $39-million urban renewal plan to construct a cultural and recreational complex. Some structures on the site have been removed while others await demolition.

But none presented the problems that the Biltmore did. "It’ s the heaviest steel we’ve ever worked on," says Mark Loizeaux, of Controlled Demolition, Inc. (CDI), Towson, Md., which dropped the brick-clad structure for contractor Wells Excavating Co., Inc., Oklahoma City.

"Because of the thickness of the steel, a single charge wouldn't penetrate completely through," he says. “We had to attack a single 3-in.-thick stem plate from both sides." Each 16-in. steel column with built-up flanges totals 2.5 to 3 tons per floor.

To blast in this fashion, says Loizeaux, it is imperative that the charges on opposing sides go off simultaneously. If one goes off too soon, it will dislodge the other before it can cut through the steel.

CDI placed 991 separate charges, about 800 lbs. of explosives in all, on seven floors from the basement to the 14th floor and detonated them over a five-second interval. CDI’s detonation sequence aimed to drop the building in a southerly direction in what is called a controlled progressive collapse in order to lay out the demolished structure to ease removal of debris.

Besides concern over the size of the steel frame members, CDI took a hard look at the type of steel, which Loizeaux describes as malleable. He says such steel doesn't break readily and "can get real testy." But the building fell, as planned, and CDI walked away with its share of the $207,000 demolition general contract.

In 1975 CDI demolished a 32-story reinforced concrete building in Sao Paulo, Brazil, the only building taller than the Biltmore to be dropped with explosives (ENR 11/27/75 p. 11). That building stood 361 ft high.

Engineering News Record
McGraw-Hill's Construction Weekly
October 20, 1977