Personal Injury Law

Suspension Bridge Strength Tested

By Jane Akre

Suspension bridges cross the nation.

San Francisco's Golden Gate is one, so is the Brooklyn Bridge. The San Francisco span into Marin County runs nearly a mile over the San Francisco Bay.   The design is simple - two cables anchored at either side hold up the roadway with the help of thick steel cables.

But the bridges are aging. The Brooklyn Bridge is more than 100 years old, and no one knows how long they will last. 

The thousands of steel strands are visually inspected once a year, but that doesn't tell anyone if they are close to failing. 

Engineer Raimondo Betti, of Columbia University, and colleagues have actually built a replica of real world conditions. Inside a glass-walled chamber is a 20 foot length of steel cable. Inside will be the sensors. 

Technology will simulate weather condition just like outside.  Both the Manhattan Bridge and Williamsburg Bridge have similar 20-inch diameter cable. 

For six months, Betti will record data from the sensors which will be subjected to heat, water, and salt. 

We are trying to create conditions that are more aggressive than the ones out there," Betti says to National Public Radio, "because otherwise the system will not be tested."

The goal is to know about the strength or weakness of a suspension bridge cable before it lets you know it has failed. Dismantling a bridge for repairs would be prohibitive because many surround major metropolitan areas such as New York and San Francisco.

Examples of suspension bridges include Bronx-Whitestone Bridge (NY); Brooklyn Bridge (NY); Mackinac Bridge (MI); Throgs Neck Bridge (NY), Bear Mountain Bridge (NY).

In Minneapolis the I-35 bridge collapse in 2007 which killed 13, was found to be due to insufficiently thick gusset plates that connect the steel to the structure.   #

Full post as published by InjuryBoard on February 23, 2009 (boomark / email).