The Dames Point Bridge in Jacksonville is on the list of bridges regularly inspected by officials from the Florida Department of Transportation. During one of these checkups, it was discovered that a rod located near the bridge doesn’t have enough tension. To fix this problem, FDOT brought in a construction, mining and engineering organization.
It’s a typical humid and sunny Sunday morning on the east coast of Florida as a boat filled with workers races through the marina towards a waiting barge and tug boat located near the bridge. Cutting through the waves, the boat carries a crew of engineers, tug boat captains and labours who are responsible for raising a platform. The erected platform will allow workers from a subcontractor to get close enough to the bottom of the bridge in order to make the needed repairs.
Over the life span of a bridge, these rare repairs might be made once, making these repairs the first for the more than 20 year old bridge. A project engineer employed with the company that scored the contract explains in more detail, “At the mid-span of the bridge there are three shear locks that hold the two bridges in vertical alignment. There’s a 10.5 inch gap so they can expand and contract. Those shear locks are anchored to the deck with post tensioning rods. The center shear lock is what we will be working on. The opposite end of those post-tensioning rods the anchorage is approximately 40 feet straight back underneath the bridge deck, parallel with the traffic. In order to get to it, we must raise a platform, access it through the center span, walk back onto the platform and get to the anchoring point of these rods. The problem is that one of these rods has no tension on it. It should have 150,000 lbs of tension on each rod. So what we’re going to do is concrete demolition on each of these anchoring points and remove the rods, at least that one rod for sure and replace it with a new rod. More likely it’s a coupler on those rods that is broken. We’ll replace the coupler. Then we’ll re-tension all the rods and reinstall that sheer lock.”
The crew member operating the boat parks it next to the barge in order for folks to get off and step onto the structure. The platform that will eventually be lifted, sits on the barge. The tug boat parked directly behind the barge, makes it easy for the tug boat captains to step onto their tug boat and climb to the helm.
Then the waiting game begins. You can feel the anticipation as everyone stops, watching a large freight ship scheduled to cross under the bridge move by. The Coast Guard then starts to wave residential boaters away from the work area in order to give the crew room to lift the structure.
It’s not long before the tugboat pushing the barge shifts into motion moving towards the center of the bridge. A separate crew in the boat, races toward the center of the bridge as well, on occasion running parallel to the barge.
As the boat approaches the bottom of the bridge, it’s easy to see the booms of the 40-ton Terrex cranes pointed towards each other. Sims Crane Certified Crane Operators Johnny Bell and Ralph Coleman are ready and waiting for the signals to begin dropping their hooks into sections of the bridge deck that have been removed for the lift.
By mid-morning, yellow lines have been dropped through the opening at the top of the bridge. The platform is being tied and rigged as the boat circles the barge. There’s non-stop chatter on the radio. Then a break from the normal chatter comes. A crew member very precisely sums up what it may look like from an outsider point-of-view, “Looks like Cirque du Soleil down here.”
The signal is given and the lift begins. After some time and much maneuvering, trumping any mechanical obstacles in the way, the platform when viewed from a certain angle looks like it’s pasted directly to the bottom of the bridge.
From the top of the bridge, crews are working to reinforce the platform in place so it will be ready for use. Over the next couple of weeks, needed repairs will be made. Eventually, crews will return to remove the temporary platform.
The Dames Point Bridge is sometimes referred to as the Napoleon Bonaparte Broward Bridge or the ‘Dame’ Point Bridge. It stands 175 feet above the main channel of the St. Johns River, stretching two miles to connect northern Duval County with the Arlington and Beaches area of Jacksonville via Florida Highway 9A. Completed in 1989, it is considered one of America’s longest cable-stayed bridges. Cable-stayed bridges are supported by cables that support the bridge deck and consist of one or more pylons.
For more pictures of this project : http://www.flickr.com/photos/simscrane/sets/72157627607143576/