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Hurricane Irene to Test Composite Durability

August 26, 2011

The Bronx-Whitestone Bridge was rehabilitated between 2001 and 2003 using fiberglass fairings to stabilize the bridge.

Hurricane Irene is expected to hit the Carolinas as early as this evening and travel up the East Coast tomorrow, potentially causing billions of dollars in damage along the way. One question among the composites industry is how will our products hold up? For example, will the New York-based composite Whitestone Bridge be among the rubble or will it withstand the over 100 mph winds and rain?

In 2003, the Bronx-Whitestone Bridge, which connects the New York City boroughs of Queens and the Bronx, was rehabilitated using composite wind fairings that, builders asserted, could withstand a category one hurricane—in the wake of hurricane Irene, that theory will be tested.

The Bronx-Whitestone Bridge, locally referred to as the Whitestone Bridge, was originally a suspension bridge built at the end of the 1930s. Then trusses were added in 1943 after the Tacoma Narrows Bridge disaster scared the state of New York into reinforcing the structure. The new 14-foot steel trusses provided the bridge with added stability. However, the bridge continued to sway more than other suspension bridges in high wind. In the late 1980s, a mass damper system was added to protect against dangerous oscillations.

Then between 2001 and 2003 the remedial steel trusses were replaced with fiberglass fairings as part of a $286 million rehabilitation project sponsored by the Metropolitan Transportation Authority. Fiberglass was chosen in an effort to shed weight and reduce oscillations. Since composites are much lighter than steel, the fiberglass replacements resulted in an overall weight loss of one-quarter of the bridge’s total suspended weight while adding strength and stiffness.

Manufactured by Hardcore Composites, the wedge-shaped, fiberglass fairings are composed of glass and polyester sandwich panels connected with a foam core. Each fairing acts similar to an airplane wing that allows the wind to circulate the deck, protecting it against heavy winds, thus reducing movement. Compared to the steel trusses, the fairings used aerodynamics to stabilize the bridge rather than redirect external forces.

In total, the bridge utilizes 7,400 feet of composite material. At the time of construction, Whitestone Bridge was said to be able to withstand the onslaught of a category one hurricane. It is anticipated that Irene will downgrade from a category three hurricane to a category one by the time it hits New York late Saturday evening. Come Sunday morning, New Yorkers will get a first-hand view of how composites can withstand the test of time, and Mother Nature.

For more stories like this, search using key word “sustainability”.

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