Kun-young Chiu & Associates, Inc. - Hangar 741 Repair/Replacement

Hangar 741 Repair/Replacement

Homestead Air Force Base, Florida

Homestead Air Force Base, Florida

This former B-52 hangar, built in 1956, is 103,000 S.F., consists of 63'-11" tall doors, and has a double cantilever roof construction. This prototype hangar was designed to withstand the wind load in the 1940 ASCE Code. Drastic revisions have been made to the Building Code Wind Load Design since then, including, but not limited to, philosophy and procedure. During the past half century, more sophisticated instruments and advanced technology improved aerodynamic research.

Predicted by meteorologists as a one in five hundred year event, Hurricane Andrew swept through South Florida in August 1992. As one of our IDIQ projects, we were commissioned to study the hangar's residual integrity and subsequently were authorized to proceed to rehabilitate the building after it was destroyed by the hurricane's 175 mph winds. The wind removed most of the roof and siding. Direct wind pressure and uplift of the cantilever roof system threw three huge hangar doors to the floor. Only the structural framing remained erect after the hurricane. Destruction of the roofing and siding relieved the wind forces acting on the building, probably saving the structural framing from total collapse.

As part of the peace dividend, the hangar was to be turned over to Dade County (Miami), Florida by the Department of Defense (DOD) for civilian use. The County required that the rehabilitated hangar meet their "South Florida Building Code", 1994 Edition, considered to be one of the most stringent in the Nation. Accordingly, the hangar was designed for a wind gust speed of 110 miles an hour and a roof live load of 30 pounds per square foot (50% increase).

Other highlights of the scope of work were as follows:

State-of-the-art tie down system provided to prevent excessive flexibility for the roof double cantilever in case of severe hurricane.
Provided one handicapped restroom in accordance with Americans for Disability Act (ADA) requirements.
Restored the sprinkler system and a full lighting system for the high bay hangar area.
Cleaned and repaired all underground piping and utility lines.
Evaluated the strength of the existing floor pavement for its ability to accept current large commercial and military aircraft such as the Boeing 747 and C-5A Super Cargo military plane.

The total change order for the project was $50,000, approximately 1% of the contract amount. The change order was necessary to replace sprinkler heads found to be clogged and to dispose of additional asbestos uncovered during construction. It was extremely interesting and challenging to retrofit the old facility by using computer technology to meet contemporary code requirements.

Before

After

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