Rebuilding 4.4 miles of roads while trying to maintain traffic is not easy and getting that done ahead of schedule is nearly impossible, but Skanska was up for the challenge when they took the job. They developed a successful traffic control plan, used different concrete products, and worked around the clock to complete this massive bridge reconstruction project.
The design and reconstruction of Interstate 275 in Tampa Bay, Fla., consisted of building two four-lane highways north- and southbound with five interchanges, while maintaining the existing traffic during the project’s four-year span.
It took 45,000 cubic yards of concrete and several precast components to complete the project. The scope encompassed removing 12 existing bridges, building 21 new bridge structures, more than 30 traffic changes, and installing 6,000 feet of concrete drainage piping to stormwater. The $225 million project was led by the joint venture of Skanska and Ajax on behalf of the Florida Department of Transportation (FDOT).
Ajax had their own batch plant onsite and supplied the 14-inch- thick portland cement concrete (PCC) at a minimum compressive strength of 4,000 psi. Skanska used 173 precast Florida I-Beams and 44 Florida U-Beams to form the bridges. “Precast was a huge part of the project. We used it as much as possible because it helps with our schedule,” says Jim Goyer, vice president of Florida operations for Skanska USA Civil.
Three Gomaco slipform pavers were used, and handpaving was done in smaller areas with steel side forms and roller screeds. Pavement surfaces were built using a burlap drag finish with a final texture delivered by diamond grinding machines. The FDOT doesn’t allow or specify longitudinal tining.
How it all came together
The project required three different concrete paving mixes: two with fly ash replacement at different percentages, and one with straight cement and no fly ash. The straight cement mix was used when higher early strength was needed and when fly ash was unavailable due to market conditions. All mixes were very workable and produced a tight surface finish with no edge slump.
The mix achieved 4,000 psi compressive strength at 28 days, with a maximum specified water-cement ratio of 0.45. The concrete paving was constructed as a pilot project under a developmental new paving specification for FDOT.
Paving concrete was transported in dump trucks and Maxon agitators (an open-top dump bed with mixing paddles); no ready-mix trucks were used. The City of Tampa designated truck freight routes to access points where haul routes onto the road embankment often required modification or phasing of embankment, retaining wall, and barrier construction.
Using precast and cast-in-place concrete allowed the project team to get the best of both worlds by adding sustainability and structural soundness to the project. Precast concrete can be adapted in many ways to meet a wide variety of design challenges. While precast costs less and is easier to repair, cast-in-place concrete offers long-term durability and structural support.
Roads to the future
The Florida DOT took on this project to add capacity and build for the future. “This project was a preparatory project to a future project. It’s just one component of the overall Tampa Bay express project,” says Goyer.
The overpass bridges were simple span bridges built with traditional concrete piles, cast-in-place indents with precast girders, with the bridge deck cast on top of the stay-in-place (SIP) metal decking. Prestressing wasn’t needed for the bridge construction. Barrier and sound walls were constructed using cast-in-place concrete because of its weather-resistance and ability to block sound.
The project received a Florida Transportation Builders’ Association’s 2016 Best Project award in the urban category and a recycling award from the Florida Department of Environmental Protection for achieving a 98.7% recycling rate.
By reusing concrete as road bed or back fill, recycling all asphalt and metals from demolition work, and reusing wastewater for dust suppression onsite, this project exceeded sustainability expectations. Skanska always aims to leave the environment in better standing then when they break ground.
Maintaining traffic during any road or bridge project always takes priority. Although it would be ideal to shut the entire interstate down, it’s almost never a possibility. Construction crews must do their best to work around the traveling public on a daily basis.
The crew minimized the impact on traffic by working in three shifts. They worked through the night when crossroads had to be shut down for bridge demolition and girder setup. During the day, traffic was tactfully shifted while the crew worked in the median.
“It’s important to keep traffic moving while minimizing the impact of construction work on the public.” says Goyer.
Public safety and the logistics of building a new road on top of an old one were the biggest challenges during the reconstruction. Traffic was redirected while the new road was built alongside the existing road, then redirected again when the old road was removed.
“Each project decision affected someone’s commute, so we focused on rebuilding the highway while keeping people in the Tampa area moving,” says Goyer. “The road improvements delivered will help motorists along I-275 have a safer driving experience for years to come.”
The project is a major improvement to the traffic patterns in and around downtown Tampa and was delivered four months ahead of schedule.
The bridge reconstruction was completed in late December of 2016. Now there are four through-lanes in each direction, a flatter roadway (eliminated steep humps at bridges over crossroads) to improve sight distance and decrease the chances of accidents, improved interchanges to help move traffic on and off I-275, and a wide median to decrease cost and public impact when future improvements are built.
At the project’s conclusion, the contractor overcame several obstacles and used both precast and cast-in-place concrete to successfully complete the reconstruction of Interstate 275. The project should help decrease the number of accidents and alleviate some of the traffic that has plagued the region for years. “This was a very successful design-build project. We’re very happy that we were able to deliver on time, ahead of schedule, and under budget,” says Goyer.