Bridges normally aren’t constructed this way, but thanks to cutting edge technology developed in part by a Canadian company, that’s exactly what’s happening in Cartagena, Colombia
Building a bridge from the top down isn’t the usual way to do it. But when bridge builders faced the daunting prospect of having to span five kilometres of swampland during a highway upgrade project in Cartagena, Colombia, it was determined that top-down construction made the most sense.
An integral part of this project is a groundbreaking beam launching girder system that enables bridges to be built in wetlands and shallow water areas that prevent the use of conventional floating equipment and cranes.
Construction of the two-lane, five kilometre long bridge began last September and is expected to be completed by 2019. A key contributor to the project is a Canadian company that assisted with the development of the beam launching system.
“The only system that they thought was viable was to bring this equipment to Colombia and use it for a top-down construction of the bridge,” said Stefano Gabaldo, sales engineer for Bermingham Foundation Solutions of Hamilton, Ont.
A beam launcher enables equipment and construction materials to be moved along a completed structure instead of along the ground or through floating vessels. Two of them are being used in Cartagena, one at each starting point for construction, and they will eventually meet near the middle to complete the bridge.
“The beam launchers are now driving piles and building the bridges at both ends,” said Gabaldo. “It is very slick system.”
Gabaldo describes the massive machines as the only ones like them in the world. Each one, he says, weighs about 1,000 tonnes and is almost 200 metres long.
“The only system that they thought was viable was to bring this equipment to Colombia and use it for a top-down construction of the bridge.”
– Stefano Gabaldo, Bermingham Foundation Solutions
How beam launchers work
The beam launcher works through the use of a gantry that rests on the front edge of the already completed part of the bridge. The gantry cantilevers forward to allow the installation of the piles and the subsequent formation of the next pier.
After the piles have been driven at the front of the gantry, the pile cap and main girders of the bridge are then installed. All this happens without builders ever having to touch down on the ground.
“The machine basically builds the bridge,” said Gabaldo. “At the back end of the machine you have the finished product so your construction site is actually the beam launcher.”
Within each launcher is a tilting lead that is loaded with a pile horizontally; this lead then rotates the pile to a vertical position and drives it into place at the bent or pier location.
The bents in the Cartagena bridge are 37 metres apart and each one requires the installation of at least six supporting piles. In total, more than 800 piles will be driven to support some 130 bents being built during the bridge’s construction, says Gabaldo, adding that as of late April, almost two dozen bents (or approximately 850 metres of the total bridge’s length) had been successfully installed.
For this project, Bermingham designed a custom 48-inch box lead based on the pile design, in this case pre-cast concrete piles 42 metres long and one metre in diameter. The piles have a hollow core with 160-millimetre thick walls, and each one weighs roughly one tonne per metre. The piles are driven in two sections that are joined together with a custom-designed mechanical splice.
The bridge, located just north of Cartagena, forms part of a highway connecting the city to Barranquilla, Colombia. The Colombian government contracted the Italian firm Rizzani de Eccher to build the bridge, and a subsidiary company called DEAL contacted Bermingham in 2015 to ask for help with the piling portion of the beam launcher project.
DEAL had already partnered with Bermingham in the past. The two companies worked together to supply two similar beam launchers for the construction of a bridge in Washington, N.C., back in 2007.
DEAL proposed using the same technology for the Cartagena bridge, whose builders shared similar environmental challenges faced by those in North Carolina.
Benefits of top-down construction
Top-down construction significantly reduces the footprint left by bridge building by eliminating the need for heavy equipment and supporting structures on the ground.
It’s particularly useful in very shallow areas when building from a barge is extremely difficult, if not impossible, and it can also reduce potential damage to environmentally sensitive marshlands. Both were key considerations in Cartagena, where the bridge builders are traversing a shallow, mangrove-filled lagoon located along the Colombian coast.
Gabaldo says building the bridge by alternate means, such as creating artificial islands or constructing temporary structures for pile driving, would have had been harmful environmentally.
Estimating the total cost of the Cartagena bridge project at around $100 million, Gabaldo maintains building the bridge by traditional means would have been hugely expensive as well.
“There are significant investments in order to build bridges in these kinds of environments,” he said. “If you can’t do it either by land or by water, you have to think of a Plan B.”
In addition to supplying the two lead systems for the beam launchers in Cartagena, Bermingham also refurbished three Berminghammer B-6505HD diesel impact hammers used in the Washington bridge project. Two of them are currently being used on site in Colombia and the third is there on standby in case it’s needed.
According to Gabaldo, Bermingham had a tight delivery timeline for the project.
“I think we had four months from the time the papers were signed to the time the containers with our equipment left our yard in March 2016,” he said.
Gabaldo says Bermingham personnel completed a thorough assessment of their equipment once it arrived in Colombia.
“When you’re on site, there’s always some tweaking because you want to correlate your calculations with the real world,” he said. “We did all the testing and we were spot-on in all the calculations.” 