It’s a scene that plays out in virtually every major metropolitan market in the U.S.
Growth and development along highways and roadways lead to increased traffic and congestion. Roads that were relatively free-flowing with a Level of Service (LOS) A or B rating (as defined by the Highway Capacity Manual published by the Transportation Research Board) just a decade or two ago are now facing the congestion and stop-and-go traffic of D-, E- and F-rated roads. Scarce state construction dollars and an under-funded federal road bill delay much-needed reconstruction and expansion of roads required to reduce congestion.
The Oklahoma Turnpike Authority (OTA) is taking a proactive approach to boost the capacity of the Creek Turnpike by 50% to ensure commuters using the highway to skirt Tulsa do not experience the congestion and gridlock associated with these lower-rated E and F roads.
“The existing four-lane highway,” said Jack Damrill, Turnpike spokesman, “was designed to handle 60,000 vehicles per day, and current annual average daily traffic numbers are approaching 58,000 vehicles per day.”
The OTA contracted with Sherwood Construction of Catoosa, Okla., to upgrade and expand an 8-mile stretch of the toll road. The nearly $59 million project addresses congestion along nearly 25% of the Turnpike stemming from Memorial Drive to U. S. Highway 75 by expanding the roadway from two lanes to three lanes in both directions.
“This section of the Creek Turnpike sees the most amount of traffic, and expansion will bring the road LOS to a low B to high C rating,” said Damrill.
The 504-day project required the widening of 10 bridges along this section of the Turnpike.
“It boiled down to 20 bridges if you consider that each bridge has an eastbound and westbound component,” said Claude Ward, bridge superintendent for Sherwood Construction. For bridge-deck paving, Sherwood enlisted the help of three Terex Bid-Well 4800 pavers.
The Creek Turnpike originally opened to traffic in 1992 with extensions eastward and westward developed over the next decade. Development along the toll road over the past 20 years has increased the Turnpike’s traffic, lowered its LOS rating and made it in need of expansion. Fortunately, the roadway was built with expansion in mind.
“Before widening the bridges, there was approximately 40 ft in between each eastbound and westbound bridge,” said Ward.
The plans called for the bridges to be widened to the inside, closing the gap in between each bridge. According to Ward, each bridge width increased by 20 ft. After expansion, the space in between the eastbound and westbound bridge lanes shrank to just 2 in. A parapet wall on either side of the eastbound and westbound lanes separates the widened bridges.
Concurrent with the bridge work, different crews from Sherwood handled the earthwork and grading for the road-lane expansion in between each bridge. Still, other Sherwood crews used slipform pavers to pave the concrete road leading up to the bridges.
“Sherwood has people for every stage of construction,” commented Ward.
Sherwood was founded in the latter days of the Depression, in 1934, as a heavy grading company. Today it is best known for its dirt-work projects. However, more recently the company has expanded its focus to include concrete work throughout a market that expands from Texas and Arkansas to Oklahoma and Kansas. It has built a solid reputation for bridge construction and paving as well.
“Last fall, we had 27 bridge projects under construction at one time,” said Ward.
The close quarters and bridge-construction plans on the Creek Turnpike would prove to be a test for Sherwood. The company would have to rely on its crew members’ expertise and flexible paving equipment to turn even the toughest challenge into the seemingly mundane.
The high side
The roughly 2 miles of bridgework threw a number of paving challenges at Sherwood, including superelevated sections and skewed decks. Curves on the roads adjacent to the start of the bridges led to superelevations that put the eastbound traffic bridges higher than the westbound and vice versa, depending on the direction of the curve.
“Think about it as two banked racetracks going around the same curve but with cars going in the opposite direction,” explained Larry Eben, district manager for Terex Bid-Well. “One side is going to be higher than the other.”
These superelevations resulted in a bridge deck being as much as 2 ft higher than the adjacent lane of the opposite-direction bridge where the two bridges came in close contact. Crews had to make sure the three 4800 pavers on the project could be properly adjusted to handle finish paving of the bridge deck where the bridge lanes were joined.
Making this all the more difficult, the paver frame had to clear rebar installed for the barrier walls that would separate the lanes of traffic.
“A 42-in.-high parapet wall separates the eastbound and westbound traffic on the bridges,” said David Murdock, director of engineering for the OTA.
For the bridges traversing the Arkansas River, Coal Creek and Vinsel Creek, constructed with superelevations, Sherwood’s paving crew poured the high-side bridge deck first. For the 2,400-ft-long Arkansas River Bridge, this meant paving the westbound lane expansion first.
Work crews paved 600-ft deck sections one at a time and left one week in between each pour for concrete curing, which resulted in a two-month completion time.
“We could not pour the high side and low side simultaneously, so we would have to pour a section and wait for it to fully cure, so we could get equipment onto the new deck to pave the next section,” said Ward.
Each 4800 paver was set to a 20 ft width for bridge paving. The paver offers a maximum standard width of 120 ft and offers standard minimum and maximum paving widths of 12 ft and 116 ft, respectively. The paver can be constructed to reach widths beyond 120 ft.
“We can extend our 4800 pavers to 130 ft wide without adding truss segments,” explained Ward. Truss-extension inserts, available in a variety of widths ranging from 2 to 18 ft long, allow the paver to meet virtually any paving width.
According to Ward, approximately half of the bridges also were built at varying degrees of skew angle. Crews could have equipped the 4800 paver with a skew bar kit and set it to pave with the skew angle.
“The skew bar kit allows the paving carriage to be offset, so it hits the same crown points from the machine’s front to rear,” said Eben.
However, Ward preferred to keep the three pavers square, since crews were often moving each paver from bridge to bridge. Cool weather allowed crews to pour the concrete ahead of the paver in order to take deflection out of the deck beams without the fear of the concrete setting up too early.
Paving the lower, opposite-direction bridge decks in the superelevations is where the flexibility of the paver really helped to save Sherwood time and money. In order to achieve proper grade and a smooth riding surface, crews set the paver’s legs on the existing lane of the lower deck, while the opposite legs traveled along a rail set on the recently expanded higher deck.
The paver’s frame had to straddle and clear the steel for the parapet walls that separated the eastbound from the westbound lanes.
“Everything we needed to adapt the paver to this job was already built into the machine,” said Ward.
Depending on the degree of superelevation, the lane of the high-side bridge deck ranged from 6 in. to as much as 2 ft higher than the bridge deck that was being paved.
“Leg height on the 4800 can be adjusted up to 48 in. with the screw-adjustment mechanism designed for this type of application,” said Eben.
Ward added, “We can hydraulically raise and lower the legs from the operator’s platform,” which made it easy for the operator to adjust leg positioning as the paver transitioned out of the superelevation. Should Sherwood’s crews ever need additional leg adjustment beyond the 48 in., they can reposition the leg at the leg plate, where it clamps to the frame, for an additional 16 in. of adjustment.
With legs in position and the frame clearing the steel of the divider walls, crews had one final adjustment to make prior to paving: the height of the paving carriage. The 4800’s paving carriage consists of dual adjustable strike-off augers with double flighting to efficiently meter the concrete and two, 5-ft-long paving rollers. In between, the patented Terex Bid-Well Rota-Vibe system reconsolidates the top 2.5 in. of concrete. Adjustable finish pans are available with either burlap drag or astro-grass to finish the concrete with the desired texture.
The requirement of elevating the frame to clear the wall meant the paving carriage had to be lowered from its standard operating position.
With the adjustments made for the paver and carriage height, crews poured the class AA, 4,000-psi concrete in front of the 4800 paver, 300 cu yd at a time. In part due to the paver’s quick adaptation to the challenging paving conditions along the Creek Turnpike, Sherwood will be able to complete the bridge work ahead of schedule, according to Ward. This will allow commuters on this section of the Creek Turnpike to, once again, drive with the relatively congestion-free experience of a LOS B to C roadway. R&B