Gravity played role in New Orleans' bridge failures

Nov 29, 2005
Interstate 10's eastbound and westbound bridges suffered severe damages.

Sir Isaac Newton did a number on the Interstate 10 bridges in New Orleans, according to a team of researchers at the University of Missouri-Rolla that helped document some of the damage caused by Hurricane Katrina.

The team believes Newton’s theory of gravity can explain why the 65-foot concrete slabs dropped off their supports into Lake Pontchartrain.

“The bridge’s design created structures in the shape of an upside-down rice bowl in each span, with the opening faced downward to the water,” explains Dr. Genda Chen, associate professor civil, architectural and environmental engineering at UMR. “Our preliminary analysis shows that the main culprit for the collapse or displacement of spans is the significant reduction of effective gravity loads. Air was trapped underneath the bridge decks in these ‘rice bowls,’ allowing the bridge decks to partially float and tilt.”

The reduced gravity load weakened the ability of the bridge spans to resist the water current.

“The main span over the navigation channel is a much taller structure than the approach spans; it experienced no damage during Hurricane Katrina,” Chen says. “All the approach spans experiencing excessive horizontal displacements were moved toward the ocean, which indicates that the displacement was caused by the storm surge and wave-structure interaction rather than the wind gusts associated with the hurricane.”

After the water level was lowered or air escaped from underneath the bridge decks, the bridge structures landed again on piers -- but at wrong positions -- or dropped off their supports altogether.

The rice bowl theory helps explain why Highway 11 and railroad bridges – located near the twin bridges – suffered minor or virtually no damage, Chen says.

“The Highway 11 bridge consists of shorter spans and shallower girders, reducing the volume of air that could be trapped underneath,” Chen explains. “The railroad bridge is a solid deck structure, which means no air can be trapped underneath the bridge.”

The U.S. Geological Survey (USGS) in Rolla sponsored the team’s trip to New Orleans and provided researchers with satellite imagery, and various forms of mapping information and scientific assessments of the damaged areas.

The team is preparing its final report and intends to share its findings on the Internet by early next spring, using a tool developed by the USGS and the Department of Defense.

Source: University of Missouri-Rolla

Explore further: Scientists seek more tombs at ancient Greek site

add to favorites email to friend print save as pdf

Related Stories

Taiwan Computex to showcase laptop-tablet hybrids

Jun 01, 2012

(AP) — Taiwan's struggling computer makers will use next week's Computex show to promote a new generation of ultra-thin laptops that might be their last hope of turning back the seemingly unstoppable ...

Sewage-tainted floodwaters threaten public health

Sep 09, 2011

(AP) -- Nasty floodwaters from the remnants of Lee and Irene - tainted with sewage and other toxins - threaten public health in parts of the Northeast by direct exposure or the contamination of private water ...

Taiwanese group introduces new MorPACK, stacked chip

May 05, 2011

(PhysOrg.com) -- Taiwan's National Chip Implementation Center (CIC) has announced a new chip bundling design that they claim can cut development costs in half while also reducing the time it takes to bring a new chipset to ...

Recommended for you

When shareholders exacerbate their own banks' crisis

Nov 21, 2014

Banks are increasingly issuing 'CoCo' bonds to boost the levels of equity they hold. In a crisis situation, bondholders are forced to convert these bonds into a bank's equity. To date, such bonds have been ...

Trouble with your boss? Own it

Nov 21, 2014

Don't get along with your boss? Your job performance may actually improve if the two of you can come to grips with the poor relationship.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.