subscribe to ENR magazine subscribe
contact us
careers industry jobs
events events
Dodge Data & Analytics
ENR Logo
Web access will be provided
as part of your subscription.

How Sensors on I-10 Twin Span Bridge Reduce Unknowns

Text size: A A
Photo courtesy of Geocomp
A sampling of one of the sensors on the Twin Span Bridge.
----- Advertising -----

Well before embedded instrumentation delivered data from a February 2009 lateral load test of a bent and pier of the I-10 Twin Span Bridge in New Orleans—and long before the sensors begin a life of service as long-term structural-health monitoring aids this October—devices cast into the bridge's structure were presenting a wealth of data to the industry.

“The instruments that are in the pile foundations had to be placed in the rebar cages for the piles in the casting yard,” says W. Allen Marr, president and CEO of Geocomp Corp., Acton, Mass. The concrete was poured around corrosion monitors, other sensors and polyvinyl-chloride conduits, which provide channels for adding any new instrumentation and cabling.

Geocomp began monitoring stresses in the piles through readings of embedded strain gauges, heat sensors and in-place inclinometers, from the day of their casting to their installation. The firm monitored the concrete pour, the cure, the pre-stressing, transport to storage, and the strains endured as the piles were loaded onto barges for shipment down the Mississippi River, from Memphis to New Orleans. It also monitored off-loading, positioning for installation and every blow as the piles were driven into Lake Pontchartrain's bed to become part of the new bridge foundation. The data reveals whether the piles were properly created and handled, says Marr.

Instrumentation has been embedded in pilings before, Marr adds, but not on the scale done for the Twin Span Bridge's structural-health monitoring tests. Twelve of the foundation piles on pier M-19 of the bridge's main navigation span have embedded strain gauges at 16 ft and 21 ft below the pile tops. Six in-place inclinometers were installed on eight piles at the 5-, 15-, 25-, 35-, 45- and 65-foot marks from the bottom of the pile cap. When complete, the bridge will sport 340 sensors, including weigh-in-motion sensors, corrosion meters, strain gauges, tilt meters, inclinometers, accelerometers and water-pressure cells.

“Those readings of each of those sensors are valuable to quality-control people and design engineers,” Marr says.


----- Advertising -----
  Blogs: ENR Staff   Blogs: Other Voices  
Critical Path: ENR's editors and bloggers deliver their insights, opinions, cool-headed analysis and hot-headed rantings
Project Leads/Pulse

Gives readers a glimpse of who is planning and constructing some of the largest projects throughout the U.S. Much information for pulse is derived from McGraw-Hill Construction Dodge.

For more information on a project in Pulse that has a DR#, or for general information on Dodge products and services, please visit our Website at

Information is provided on construction projects in following stages in each issue of ENR: Planning, Contracts/Bids/Proposals and Bid/Proposal Dates.

View all Project Leads/Pulse »

 Reader Comments:

Sign in to Comment

To write a comment about this story, please sign in. If this is your first time commenting on this site, you will be required to fill out a brief registration form. Your public username will be the beginning of the email address that you enter into the form (everything before the @ symbol). Other than that, none of the information that you enter will be publically displayed.

We welcome comments from all points of view. Off-topic or abusive comments, however, will be removed at the editors’ discretion.