To create a precast concrete bridge, workers must take steps to ensure the final product withstands more than 50 years of constant use. When you understand this process, you may gain inspiration for your own concrete project.
””In 1889, Ernest Leslie Ransome made history by being the first to utilize reinforced concrete to create a bridge on public roadways – the arched Alvord Lake Bridge in San Francisco, California. The demonstrated strength and durability of that initial bridge inspired the construction of more than 330,000 concrete bridges across the United States. The bridges span across large waterways, freeways, and otherwise impassable stretches to markedly improve the existing transportation infrastructure. With many of these structures approaching the end of their expected 50-year lifespan, new bridge construction projects will undoubtedly begin soon. Understanding how bridges are built over water and across large land masses may give you ideas for your next concrete construction project.
Create Precast Segments
At the beginning of the bridge construction process, workers begin creating the precast segments for the bridge deck. These pieces are constructed using match-casting techniques to ensure a perfect fit. With match-casting, the deck segments share exact end specifications that creates a perfect mating point for those pieces. The completed segments are delivered to the jobsite on a flatbed truck and stacked to the side using a crane.
Place the Cofferdams
To keep water and soil from falling into the holes created for the support piers, workers must place cofferdams around their intended placement points. Workers start by removing unstable sediment and leveling the ground around the cofferdam installation locations. A template system is utilized to construct the frames out of support piles and structural bracing. The addition of sheet piles completes the cofferdam builds.
Erect the Support Piers
With the cofferdams in place, workers begin constructing the piers using cast-in-place concrete techniques and equipment. For bridges built over solid ground, workers will usually utilize a crane to pour oversized buckets of concrete into the pier installation points. On the other hand, if the piers will end up partially underwater, the crew may use a tremie pipe to deliver the concrete while actively displacing the water. For large bridge installations, crews may need to work nonstop to construct the piers out of thousands of cubic yards of concrete. Once the piers are installed, workers deconstruct and remove the cofferdams.
Install the Bridge Deck
For most bridge builds, a gantry crane and launching girder are used to lift the precast deck pieces onto the top of the piers. The crane slowly moves each deck piece along the tracks to its final resting point. Workers apply high-strength epoxy to the ends of both segments before permanently mating them together. Workers may then run steel cables and other structural reinforcement materials through the bridge ducts to keep the segments compressed together. At the end of the build, a layer of concrete grout is pushed through the ducts to protect the steel cables from the effects of weathering.
If you are ready for a concrete delivery, contact Razorback Concrete at 870-455-0700 to speak with an experienced project manager and receive a free estimate for a concrete delivery.