When it comes to bridge replacements this is about as small of a project as they get, but it is a simple way to cover all the basics and we found it very interesting. We followed this crew as they competed each step of this work. We also talked with professionals on larger jobs and got some additional input for how this process would work on bigger job that might go the length of several football fields one hundred feet off the ground. Of course we will also take a look at several of the essential tools involved in this kind of operation, large or small.
Setting a Good Foundation
Part of the problem of this old bridge and why it needed replaced was simple poor construction along with age. It did not have a good foundation, and the steel structure of the bridge itself left much to be desired. All bridges need replaced eventually, but the hope is this the new one is going to significantly outlive the prior construction. For the new bridge, footers were dug out and poured beyond where the existing bridge was prior to complete demolition of the old bridge. This will create a solid foundation for the 3 new 30’ i-beams to rest and support the entire structure.
Bridge Deck Demolition
For this small, old, weak bridge the good news is demolition is much easier than with a larger bridge. The first step with any demolition is to cut the bridge deck with a large walk behind diamond saw. For a smaller job like this they simply took several passes until the cut is all the way through the bridge. In this case cuts were made the length of the bridge, as it was easier when intending to demolish the whole bridge at once.
On a larger bridge deck, high above the ground where you and your heavy equipment would still be on the bridge, when you go to demolition it is a slightly different proposition. The concrete cuts are made in a grid pattern one small section at a time. These cuts need to be very accurate in order to not touch the steel i-beams that support the bridge deck itself.
Handheld rotary hammer drills are commonly used to drill into the bridge surface repeatedly to find the exact location and depth of each i-beam. One wrong overcut can be a very costly mistake, as each damage i-beam would need to be welded and x-ray tested to ensure no strength had been lost. Once the concrete bridge deck is cut into manageable pieces of a few square feet, they can be carefully lifted off and taken away.
While that level of care was not required for this small project, one that is universally true for any bridge deck is they are very hard to cut. By nature there is much more steel in the concrete (plus higher psi concrete) than you will find in almost any other common concrete application, which means it will destroy typical concrete diamond blades.
To deal with bridge decks specifically Diamond Products has created a special grade of diamond blade called the Giga Premium Titanium Bridge Deck Diamond Blade and as the very long name might suggests these blades are bad ass and expensive. These blades are intended for professionals in the bridge business but available to anyone with a similar type of steel to concrete ratio. Basically, these are made of the highest grade diamond possible in a very high density formula which gives you all the cutting power necessary to go right through high psi concrete with lots of steel.
Building a New Bridge Deck
Once the footers are cured the new larger i-beams are set in place and hopefully will stay there many decades or longer. From this base the pan decking is set with a lot of rebar to strengthen the structure and to get ready for some fresh concrete.
In the colder Ohio months concrete might need some assistance to cure. In this case, additional heaters along with lots of plastic were used to heat the concrete to the point it would cure properly.
The Final Product
After all the structural work is complete the new bridge deck is clearly higher than the previous bridge so additional ground is built up around the bridge to create a seamless transition for the new drive (seen in the first picture). After a few months the grass has grown back and the bridge again looks like a natural part of the landscape. A complete project like this would take 4-8 weeks to complete with a budget of $75,000-$150,000 total including the demolition and landscaping. Typical residential bridges can be built with a variety of other less expensive methods but no question this bridge is built to last!
For assistance with tools, equipment and expertise needs for any size bridge deck repair or replacement call a pro at (800) 242-4424 and talk to Ohio Power Tool. These guys have the knowledge and resources to help you determine the right tool for your job.
