What are the options during construction?
Bridges over the interstate are typically able to be completed over a short time. If the bridge is fully closed, it typically takes about three months to replace the bridge, depending on the length and style of bridge. If the department tries to keep one lane open in each direction, that construction will often take much longer.
Interstate bridges can take about a year to replace or rehabiliate since they are much larger bridges and managing interstate traffic through the work zone can add time. Generally the interstate is closed in one direction, traffic lanes are narrowed, and traffic is moved to the opposite side of the interstate. In those locations where bridges being rehabilitated are close together, several bridges may be able to be worked on at the same time.
What does the rehabilitation entail?
Most of the bridges that require rehabilitation will have the driving surface, or deck, removed using a process called hydrodemolition. This uses high-pressure water with sand to remove the concrete from the deck, while not impacting the reinforcing steel inside that concrete. Once the concrete is removed and any repairs made to the remainder of the bridge, new concrete will be placed on the bridge to build a new driving surface. Typically the roadway underneath the bridge will need to be closed for short periods of time – primarily during hydrodemolition, while setting any forms for the new deck, and while placing concrete for the new deck.
Hydrodemolition
Hydrodemolition is a process that uses high pressure water to remove concrete on a bridge deck (the portion that vehicles drive on). The water removes the concrete, but leaves the reinforcing bars on the deck in place.
Hydrodemolition is a process that uses high pressure water to remove concrete on a bridge deck (the portion that vehicles drive on). The water removes the concrete, but leaves the reinforcing bars on the deck in place.
Hydrodemolition is a process that uses high pressure water to remove concrete on a bridge deck (the portion that vehicles drive on). The water removes the concrete, but leaves the reinforcing bars on the deck in place.
Hydrodemolition is a process that uses high pressure water to remove concrete on a bridge deck (the portion that vehicles drive on). The water removes the concrete, but leaves the reinforcing bars on the deck in place.
Hydrodemolition is a process that uses high pressure water to remove concrete on a bridge deck (the portion that vehicles drive on). The water removes the concrete, but leaves the reinforcing bars on the deck in place.
What preventative maintenance needs to be completed?
Typically, preventative maintenance is a light, protective coating, often made from epoxy, that goes on the bridge driving surface. This coating fills in small cracks and prevents salt, water or other material from getting into the driving surface and corroding or damaging the concrete.
What does replacing a bridge require?
Replacing a bridge is a very extensive project. Usually, the entire bridge, including the foundation, is removed. The entire bridge is rebuilt from the ground up. If the bridge is over the interstate, the bridge is closed, and usually two lanes on the interstate are also closed to allow crews to reconstruct the foundation and work on the middle of the bridge. There are several times when the interstate may be closed for a weekend (when crews demolish the old bridge, when they are setting girders and when they are placing concrete for the deck (the driving surface).
Bridge replacement
One of the first tasks in replacing a bridge is removing the old one. The deck (or driving surface) is removed, as are the remaining portions of the bridge.
One method of building a bridge foundation is using pile. These steel beams are driven into the ground and provide stability for the bridge. Another method is using concrete columns that are drilled into the rock below the bridge to provide a firm foundation.
Crews place concrete for the deck, or driving surface, of the new bridge. Often, during the summer months, this work is done at night to provide a better product, as warm temperatures can impact the quality of new concrete.
Crews place concrete between the bridge and the roadway.