A partial collapse in 2013 of the wood roof of a 1940s-era blimp hangar on a former Marine Corps base in Tustin, Calif., damaged an experimental airship inside, say media reports. With risk of further collapse, the building was red-tagged, and no one was permitted to enter. With just 90 days to stabilize the 300-ft-wide, 1,060-ft-long, 178-ft-high structure, options were limited since crews could access only the building exterior.
The team chose to use 190-ft-tall prefabricated modular steel towers—usually used to support tower cranes—which were placed on each side of the hangar and supported by concrete raft foundations and guy wires, with helical piers installed in the soil. Four steel cables on each side of the hangar were attached to the top of the remaining portions of the wood trusses and linked up to the towers. The team says it “had to choreograph an intricate construction ballet” to demolish damaged portions of the roof and erect new stabilization systems. The project touts its spotless safety record during 5,460 hours of work, despite the tight schedule, Santa Ana winds and asbestos risk. “When the majority of construction must be accomplished from a work basket suspended from a 300-ft crane, an emphasis on safety is essential,” says the team submission. A monitoring system tracked displacement in the remaining wood structure with real-time data, fed into a website to warn of impending hazards. The team says the stabilization system also has “an aesthetic appeal, similar to a cable-stayed bridge, due to its simplicity and economy.”
Judges noted the risks in the confined space and the civil engineering complexity. “It was a very innovative project to my mind,” said one. Added another, “How could they stabilize it and restore it for less than $10 million? It’s a very fascinating thing.”
Tustin Hangar 1 Roof Stabilization
Tustin, Calif. region California
Owner Naval Facilities Engineering Command, Southwest (NAVFAC SW)
Building Manager NAVFAC BRAC
Lead Design Firm Jacobs Engineering-Michael Baker International JV
Contractor Kellogg Brown & Root Services Inc.
Structural and MEP Engineer Michael Baker International
Engineering QA/QC Jacobs Engineering
Crane Subcontractor Mr. Crane
Geotechnical Engineer Shannon & Wilson Inc.