Bridges need ideas, too
Steel bridges are modern triumphs of civil engineering. Unfortunately, nature wins every time and without constant painting and maintenance the Golden Gate Bridge would fail in five to 10 decades. And that bridge benefits from constant attention. I cross several bridges on my daily commute through Newark, N.J., that haven’t seen attention in years. One particularly rough span I call the “Drawbridge of Doom”, and it lurks near the Jersey City end of the infamous Pulaski Skyway, which has its own problems.
The Federal Highway Administration says it is catching up on bridge deficiencies, but the potential for failure is obviously quite real. One solution: spend more money. Unfortunately, highway spending is dropping. An estimated $220 billion is needed annually; we spend $86 billion. States used to spend 25% of their tax revenue for fixing and building roads; now it’s less than 10% in many cases. This shortfall literally kills bridges.
Perhaps new technologies are the panacea we need. Earlier this month at the Transportation Technology Center in Colorado, the HC Bridge Company for the first time tested a 30-foot span of eight hybrid-composite beams, sending 26 heavy coal cars across. Called the Hillman-Composite Beam (HCB), the bridge support is a concrete arch tied at each end with 450,000 psi twisted-wire cord steel reinforcements, 11 times stronger than steel plate. The support beam itself begins as a resin shell wrapped around a form core. After removal from a mold, the shell is filled with self-consolidating concrete.
Vacuum-assisted resin transfer methods (VRTM) like this result in a span that is lighter, uses less concrete, is much more corrosion-resistant, and is less expensive than high-strength carbon fiber. Five major railroads funded the test, and plans are in place for similar tests on two highway bridges this year, a 58-foot span in Illinois and a 36-foot span in New Jersey.
I happen to have a suggestion for the first test. Just don’t wait too long.
Email the editor
|
