| August 05, 2012 |
Both Ends to the Middle
It’s not either end of this bridge that is its most important entrance/exit point. It’s the middle.
That situation occurs because when you contract to add lanes to a divided Interstate using the median for the new roadway, you have a number of problems to solve, but one really, really big one. Access. But if you think innovatingly, let’s say daringly, enough, you don’t have do the work predictably.
The I-85 widening project in Cabarrus County, N.C., involves the widening of approximately 8 miles of aging and deteriorated Interstate with complete replacement of all pavement and six bridges. The job was design-build and contractor Lane Construction came up with an out of the box, stunningly simple and innovative temporary bridge – with median access ramps – concept.
“The majority of the new roadway width is being constructed in the existing 70-foot median, creating a very difficult access challenge and potentially severe safety concerns for the traveling public,” says a Lane spokesperson. “These challenges are typical on Interstate widening projects yet they are always difficult to overcome. The need for an innovative work zone traffic control and access plan is particularly critical on this design-build project due to the severe state of deterioration and Average Daily Traffic of over 100,000.
“Unimpeded access to the existing median is critical to improve safety, minimize impacts to traffic, reduce stress on existing peripheral infrastructure, accelerate the project schedule, and reduce cost of construction by increasing efficiency.”
NCDOT resident engineer Davis Diggs says the bridge wasn’t in the RFP but Lane delivered a technical proposal to access the median via a temporary bridge with access ramps. The spec’d out proposal was presented to NCDOT and went through the usual review process. And NCDOT had to review and approve not only the bridge’s construction but also its later disassembly and removal.
The temporary access bridge snapped up the attention of Federal Highway Administrator Victor Mendez who visited the project. Mendez has constantly urged more innovations and creativity to reduce delivery time and add value to transportation infrastructure projects.
“The flexibility for all the experts to come together and put together the solutions that are needed like this temporary work bridge, and separating the traffic and the general public, is very, very creative.” Mendez told local television station WBTV during that visit.
While the bridge was an unexpected move Diggs says NCDOT and Lane worked seamlessly to make it work.
“The project originally had some pretty restrictive time constraints for median access,” says Diggs. “Lane’s bridge allowed them to do a lot of things, including working during the day when restrictions would have limited them. Without the bridge there would have been more night work because of the daytime restriction, and night work is more dangerous.” And of course, says Diggs, it can be more expensive.
With the bridge Lane could work at night without interacting with traffic.
The safety improvements resulting from this concept are significant. The need to haul loads of material across major feeder road and interstate traffic into the median has been completely eliminated. Thousands of trips by construction and NCDOT inspection staff have also been made safely and without entering traffic, says Lane’s spokesperson.
The temporary bridge and its access ramps allowed Lane to make a bid with a more aggressive schedule that NCDOT had expected. The project, begun in 2011, will be done in 2014.
The problem of course is the work zone. There is traffic to deal with, the safety of workers, and the development of a schedule for equipment and material supply (40,000 loads of material had to cross the interstate to reach the median) and the need for personal from both Lane and NCDOT to come and go. And a backup plan when something goes awry. In this case two factors stood out beyond the predictable: The existing roadway badly deteriorated and there was an average daily traffic flow of more than 100,000 vehicles.
Lane looked for an existing bridge as a jumping off point in this project, but the traffic load and contract hauling restrictions meant no go. This is the point where innovative thinking stepped in. And, says Lane, as far as they know this is the first median access ramp off a temporary bridge.
A Bonus Bridge
As a bonus, most of that temporary bridge was made of material Lane had available and doing nothing at the time. Innovation in planning and design was made to work by innovative engineering on the ground.
Safety was a huge factor because the median was placed behind concrete barrier walls and no one and no equipment was exposed to unimpeded passing traffic. No cones or flagmen and no “trucks entering highway” problems were created. Clearly time lost to normal access methods was stripped from the delivery time.
Imagine the savings in time, money, insurance and so on. And that’s to both contractor and NCDOT.
“It became very apparent that an innovative approach was critical to the success of the bid, and,ultimately the project.”
- Lane Construction
The new road built on the median will eventually take traffic while the current lanes are redone. Then, with concrete barriers from the median work still in place, the old outer lanes will be redone.
In this project old asphalt roads are being replaced with concrete.
“One of the important aspects of this is that Lane had to set up their own concrete plant,” says Diggs. “Once the plant was set up concrete trucks would have had to use a road that crosses I-85, a road already over capacity and being worked on to be made into a Superstreet, then go down Interstate on-ramps, run the down that busy Interstate and then access the median. And vice versa. With the temporary bridge and ramps that doesn’t happen.”
The company says that it decided an innovative approach was critical to the success of their bid.
“It became very apparent that an innovative approach was critical to the success of the bid and, ultimately, the project,” says the company spokesperson. “Contract time restrictions on I-85 and all roads crossing the interstate mandated the development of an approach that had never been used before. Building on a concept that had proven to be highly successful on other projects, Lane staff took a revolutionary innovation to the next level with the median access bridge and ramps. This concept provides unimpeded access to the median of I-85 and also Lane’s offices and staging areas on both sides of the Interstate.”
Lane had, in the past, used existing, working bridges to create median access ramps. This was a first stand-alone it had considered. There had been the I-95 widening project in Woodbridge, Va., the I-77 widening design-build project in Mecklenburg County, N.C., and the I-385 widening design-build project in Greenville County, S.C. In all of these cases the median access ramps ran down from existing overpass bridges.
The job is actually several projects including installing the first diverging diamond interchanges in the state. A new bridge has been built and the old own is being demolished. Work on Charlotte’s outer loop is involved and there is an
“Originally the projects weren’t scheduled to start construction until 2015,” says NCDOT. “Using the design-build finance method, NCDOT was able to accelerate all three projects.”
It was two days from the end. Robert E. Lee was withdrawing and Ulysses S. Grant was pursuing him. Between them were bridges over the Appomattox River that Confederates had to destroy.
At the Battle of High Bridge, April 7,1865, Confederate soldiers set that bridge afire. But Union troops made sure it didn’t completely burn. They could use it. The Confederate Army could not rest. Lee surrendered two days later.
That historic original bridge was replaced in the early 1900s by Norfolk and Western Railroad, which eventually became part of Norfolk Southern Railroad. In 2004, Norfolk Southern donated more than 30 miles of abandoned railbed to the Commonwealth of Virginia to develop a historic trail park. Prior to its recent completion, the High Bridge was the only part of High Bridge Trail State Park not open to the public.
The renovation transformed a nearly 100-year-old abandoned railroad bridge into an efficiently reconstructed rails-to-trails pedestrian/bicycle/hiking/equestrian pathway more than 120 feet above the river.
STV designed the rehabilitation of the 2,419-foot-long pedestrian bridge for the Virginia Department of Conservation and Recreation. Repairs included the replacement of almost 1,000 wooden railroad ties and the widening of the bridge span for pedestrian traffic. The project also included three structural steel overlooks, places to stop and enjoy the panoramic views and to learn more about the bridge’s Civil War history through interpretive signs and programs.
To widen the span, STV determined that every fourth tie along the bridge would be replaced with a 14-foot-long tie. Steel brackets were attached to each end of these long ties and from there 4-by-4-inch posts were placed perpendicularly along the sides of the deck to form the rail system and to increase the width of the walkway.