DELICATE TOUCH NEEDED FOR ROOF

Published: Saturday, January 14, 1995
Edition: THIRD
Section: NATIONAL
Page: A1
Byline: By TYLER BRIDGES Staff writer

Text:

The Rivergate may be doomed, but let no one say it won't put up a good fight. Indeed, bringing down the outmoded convention center to make way for the world's largest casino is proving an engineering feat of monumental proportions.

"It's a real challenge," said Dalton Woolverton, assistant director of design and construction for Harrah's Jazz Co., the casino operator. "No one has ever taken this type of building down before."

With most buildings, the walls hold up the roof. At the Rivergate, where the rumble and thud of demolition machinery began in earnest this week, the roof in effect holds itself up.

That was done to give the Rivergate the vast expanse of unbroken interior space that delighted convention-goers in days gone by and still awes connoisseurs of architecture who are fighting to save the building.

One result of the Rivergate's engineering is that the walls must come down first. And so passers-by in early February will be treated to the spectacle of the Rivergate's roof, which is nearly the length of a football field, floating free of all but three rows of widely spaced support columns.

With all the asbestos removed from the interior, part of the wall facing the river began coming down Wednesday. On Friday, television news cameras were on hand as a large claw began smashing the North Ballroom, on Canal Street. This should take only about a week, since the ballroom was built in a conventional fashion.

Then comes the main event - the roof.

Its cable-reinforced concrete undulates in waves the length of the building, touching down on columnar supports only at the building's extremities.

To understand how it's built, imagine the roof as a set of books. To hold them up, you push the books together from the ends. If one of the books is pulled out of the middle, the loss of tension will cause all the books to fall.

That's the problem Harrah's engineers have been facing: Because the roof essentially supports itself, tearing down any piece of it will cause the entire structure to come tumbling down.

That might be just fine except that Harrah's plans to retain the concrete slab that serves as the Rivergate's main floor. Allowed to cave in, the roof would badly damage the floor, which is a major reason why officials discarded an early plan to implode the building.

Figuring out how to prevent the roof from caving in has cost Harrah's hundreds of thousands of dollars in structural engineering fees, Woolverton said.

In the end, the engineers opted to dismantle the roof the same way it was built in the mid-60s: by supporting it with scaffolding. Using the original architectural plans as a guide, workers Thursday night began putting up the supports.

To dispatch the main roof, workers will use a piece of equipment nicknamed "Pac-Man." The machine will literally bite into the building and chew the concrete and steel into small pieces before dropping the rubble onto the Rivergate's floor to be hauled away.

Initially, two Pac-Man machines will begin chewing up the roof on the side of the building nearest the river. After each section of the roof comes down, so will the scaffolding and the columns. All told, demolition of the roof should take about six weeks, Woolverton said.

By mid-March, if all goes according to plan, the 27-year-old Rivergate will be laid to rest, and the world's largest casino, scheduled to open in mid-1996, will begin to rise in its place.

A tricky demolition job like the Rivergate does not come cheap. A conventional building of its size would come down for about $500,000, Woolverton said. Knocking down the Rivergate will cost eight times as much: $4.2 million.

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#ART:

*** TEARING DOWN THE RIVERGATE ***

AN ENGINEERING FEAT

Unlike most building, the walls of the Rivergate do not hold up the roof, the roof essentialily holds itself up, with the aid of three rows of widely-spaced columns. As a result, tearing down a small portion of the roof would cause the entire structure to collapse, unless additional support is provided during demolitions.

HOW THE RIVERGATE WILL BE TORN DOWN

1. Remove asbestos and insulation from main roof.

2. Remove wall surrounding the building, leaving three rows of columns to support the roof.

3. Demolish the North Ballroom.

4. Erect metal scaffolding under the arches of the roof to hold it up during demolition.

5. Demolish roof using machine called "Pac-Man," which will chew up the concrete and steel cables.

WHY NOT IMPLODE THE ROOF?

Harrah's Jazz Co. wants to retain the foundation and the basement.

Falling concrete and steel from imploding the roof may severely damage the ground floor and the basement.

Demolition completion: Mid-March.

Demolition cost: $4.2 million.

VIEW FULL-TEXT ON MICROFILM.

Source: Harrah's Jazz Co.

STAFF GRAPHIC BY ERICA B. BYNUM


Copyright The Times-Picayune Publishing Corp.