Twin Span Maintenance

By Lisa Doyle | September 28, 2010

Regular inspections and maintenance work is necessary to keep the I-10 Twin Spans up and running. The repaired bridges are in their second year of operation. Plans to reopen the bridge were fast-tracked after Katrina to aid the city of New Orleans in its recovery efforts. In the days following the storm, DOTD personnel worked quickly to complete inspections and put together a bid package for the project. Boh. Bros.' low bid of $30.9 million came in at $20 million below the project's estimated costs, and work began on an around-the-clock schedule Sept. 12, 2005, only two weeks after the storm.

Phase I of the emergency repairs consisted of repairing 38 spans that were completely missing or submerged and re-aligning another 172 spans in order to open the bridge to two-way traffic. The eastbound span opened two weeks ahead of schedule, in October of 2005.

Phase II established traffic on the westbound span in January 2006. Damage to the westbound span included 20 spans that were either missing or submerged in Lake Pontchartrain and 265 spans that were out of alignment. Crews rearranged the undamaged panels and filled in gaps using Acrow prefabricated bridge sections of hot-dipped galvanized steel inserted into two sections to form two lanes at 24 feet wide.

Phase III involves a maintenance contract for the temporary panels being used on the westbound span.

John Horn, vice president Volkert Construction Services, gave a tour beneath the repaired Twin Spans to show some of the repairs used to stabilize the structure after the hurricane. Volkert Construction Services oversaw the emergency repairs and is currently overseeing the maintenance contract on the temporary panels as well as the new Twin Spans project.

Screw jacks were added beneath the diaphragms and underneath the girders to support the span in areas where between 25 percent and 40 percent of the girder was lost. The screw jacks carry around 30,000 pounds apiece. Steel cap saddles were added in areas with greater than 40-percent loss.

Maintenance to the temporary bridge panels is ongoing. The bridge is under stress due to the traffic volume. "The temporary spans are performing as well as can be expected under this much traffic," says Horn. "They weren't designed to handle this much traffic. They were designed to be put in place as detour bridges, or secondary bridges. They work for this application, but they require constant maintenance to stay open."

Inspections are made to the bridge four days a week, and, when warranted, the bridge is shut down on Sunday nights to make repairs.

To maintain temporary bridge panels, crews tighten bolts and replace broken pieces. Bolts that hold down the panels on the temporary bridge sometimes break and have to be changed out periodically. "Usually the only damage seen on guardrail sections is when there has been an accident," says Dudley Boudreaux, bridge inspector for Volkert Construction Services.

A Terex TH1048C is used to move panels when repairs to the bracing are necessary. This usually occurs on Sundays when the bridge can be shut down for repairs.

Overloaded and speeding trucks have the potential to do the most damage to the bridge. The weight limit is 70,000 pounds with a speed limit of 45 miles per hour. Trucks have been ticketed for carrying as much as 117,000 pounds and going 97 miles per hour across the bridge.

Unregulated in early days after the repairs, the LA DOTD closed the bridge in late November 2005 to all oversize and overweight permit loads because of the damage caused by them. Later, another press release warned that speeding and overweight trucks were wearing on the temporary panels. Traffic enforcement was stepped up on the bridge, with a warning that 18 wheelers could be banned altogether from the repaired bridge.

The traffic management plan for the repaired twin spans had included a lower speed limit of 50 miles per hour for cars and 40 miles per hour for trucks on the westbound side, with lane changes prohibited on the approach and crossing the panels, compared with 60 miles per hour on the eastbound side, which had no temporary bridge panels. Maximum speed was later changed to 45 miles per hour for all vehicles traveling in the westbound lane. Both the eastbound and westbound spans are closed to all oversize and overweight permit loads. Inspections and maintenance were necessary nearly every day of the week before higher restrictions were placed on the bridge.

Even with the less intense maintenance schedule, motorists are not always understanding. Inspection and repair crews have a task that is often thankless, and is even rewarded at times with road rage.

Traffic is held back as the lane is blocked off ahead of the inspection and repair crews by Traffic Solutions. State troopers also accompany crews across the bridge, which helps with the drivers, but even in plain sight of the law, some cars will cross into the closed lanes to speed ahead of other cars, risking the lives of crew members who are in various areas inspecting and replacing bolts.

Inspections are also done beneath the bridge, by boat, when Lake Pontchartain waters are calm enough. Inspectors walk the length of the bridge by hand, checking for failures.


New Twin Spans Under Way

Ground broke July of last year on the new I-10 Twin Span Bridge, an $803-million project to replace the Twin Span Bridge between New Orleans and Slidell that was ravaged by Hurricane Katrina.

The new bridge, completely funded with federal dollars, will be built 300 feet to the east of the current bridge. The bridge will have an elevation of 30 feet, which is 21 feet higher than the old bridge, and an 80-foot high-rise section near the Slidell side to allow for marine traffic. The increased elevation will allow the bridge to withstand a much higher storm surge. The 60-foot width of each span will include three 12-foot lanes and two 12-foot shoulders on each side. LA DOTD designed the bridge to include reinforced concrete walls that will increase the bridge's storm surge resistance, as well as minimize any effects of a barge collision.

The bridge is designed for a 100-year life. It will be built entirely with high-performance concrete. This concrete is stronger, denser and less porous than normal concrete. It is also more resistant to corrosion caused by salt water, which leads to the deterioration of the concrete structure that supports the bridge.

The 5.4-mile-long bridge will have around 2,600 columns, altogether. Columns are 36-inch spread piles around 100 feet long. Girders are 75 feet long for the project and are being fabricated by Boykin in Baton Rouge, La. Gulf Coast Prestress in Pass Christian, Miss., is fabricating the pilings. Decks have been poured on parts of the north shore of the project. Production pile driving began this summer on the New Orleans shore of the project.