Walsh Builds 4,150-Foot-Long I-480 Girder Bridge Squeezed Between Two Existing Structures High Above Ohio’s Cuyahoga River Valley
$227.8M Project Redecks Ohio’s Most-Traveled Bridges: Gantry Crane System, Supported by Existing I-480 Valley View Bridges, Requires Complex Calculations and Careful Maneuvering to Avoid Disrupting Heavy Traffic
As the deck of the 40-year-old Interstate 480 Valley View bridge structures near Cleveland reached the end of its lifespan, the Ohio Department of Transportation (ODOT) explored options for managing traffic during construction. With 180,000 vehicles crossing the eastbound and westbound bridges during peak travel times, all of the most common maintenance-of-traffic strategies came with significant downsides.
To keep traffic moving, ODOT elected to build a new steel girder bridge – between the two existing structures, 200 feet above the Cuyahoga River Valley. Upon completion, there will be just a 2-and-a-half-foot gap between each bridge’s parapets.
Building within that tight space required a complex gantry crane system to place steel girders without affecting traffic. The new 4,150-foot-long, four-lane structure will accommodate traffic from each of the two existing, four-lane bridges while crews replace their decks, then it will carry bi-directional traffic to increase capacity from four to six lanes in each direction.
The multi-phased work on the most-traveled bridges in the state resulted in a $227.8 million, six-year contract – the fourth largest project in state history and one of ODOT’s longest-ever duration. Financed by Grant Anticipation Revenue Vehicle (GARVEE) bonds, the project includes deck replacements and structural repairs on the existing twin structures, construction of the new bridge in the existing median, approach roadway construction to connect the bridge structures to the existing highway system, drainage, traffic control, and lighting upgrades. Construction began in February 2018 and will finish in 2024.
The Only Option
Plans for the project evolved as ODOT considered options. “We first looked at a retrofit of the parapet walls because they were low and crumbling,” said Michael Herceg, ODOT’s Project Manager. “We took some cores of the decks and discovered that the reinforcing steel was not epoxy coated. Back in the 1970s when these structures were built, we weren’t doing that. The chloride content in the concrete from the salt was extremely high, which meant the steel was rusting. At the time, the decks weren’t in bad shape, but we put up some subdecking in a few areas because spalls were forming.”
Given the age of the steel girder bridges, though, ODOT began looking at maintenance-of-traffic issues when they eventually replaced the decks. “If we closed even one of the eight lanes, the public would experience unacceptable delays,” Herceg said. “The shortest detour route on the interstates was 10 miles in either direction. If we rerouted traffic onto arterials, we estimated we’d need to put over $90 million into improvements to handle the traffic volumes. We even tried some scenarios with closing interchanges to reduce traffic. None of those options worked.”
In the end, ODOT decided the best alternative was to build the bridge in the middle. As an added benefit, “Because we now have this third bridge with bi-directional traffic, we were able to improve the traffic patterns on the existing bridges tying into the Interstate 77 and Transportation Boulevard ramps on either side of the project,” said Kirk Gegick, ODOT’s Construction Project Manager. “Those ramps will have their own lanes instead of merge conditions.”
When it came time to bid the job, ODOT decided to use design-build for speedier delivery. “With a job this expensive, our finance people decided to sell it a little sooner and as a result save some inflation money,” Herceg said.
ODOT awarded the design-build contract to Walsh Construction of Cleveland in October 2017. Due in part to an alternative technical concept they proposed, Walsh came in significantly lower than other bidders and ODOT’s original estimate.
Typically with pile driving for foundation support, ODOT discounts strength gained as the ground solidifies. “We don’t normally wait until that happens to measure the strength of the pile,” Gegick explained. However, “Walsh set forth a procedure with pile set-up used in other states. The funny thing was that ODOT was considering studying that because it presents a significant cost savings to the taxpayer if we can shorten the length of the piling that holds up our bridges.”
For this project with 18-inch, round, cast-in-place piles, “Walsh had to show us proof that the anticipated set-up was being achieved in the field,” Gegick said. In addition to data from other states, “They re-struck their test piles at different time durations to demonstrate the actual strength that the pile gained over time, so we allowed them to use a portion of that strength gain in their foundation design.”
As a result, “Their pile driving lengths were reduced by as much as 50 percent,” Gegick said. “We ended up driving almost 67,000 feet of pile and it could’ve been almost double that.”
Balancing in the Middle
Because of the height and space constraints in building the new bridge, bidders considered two innovative techniques, Gegick said. For the first option, “They would’ve constructed a launching pit on the east side of the project, built the bridge there, and essentially pushed it across the valley. That was very expensive, required a lot of special equipment, and came with a big schedule impact.”
In the second alternative chosen by Walsh, a gantry crane system uses the existing bridges as support. As part of project bids, “We required a 3-D grid analysis of all the members of the existing bridges to make sure they weren’t exceeding the capacity of any of those members while traffic was maintained on the bridges,” Gegick said.
Walsh elected to use three specially made, lighter-weight gantry cranes to spread out the load, running them on train rails placed on top of the girders of the adjacent bridges. ODOT shifted traffic to the outside of each existing bridge to provide a 17.5-foot work zone. Inside that area, Walsh milled off 2-and-a-half inches of the deck to remove some of the dead load.
Steel erection began in April 2019. “They assemble the girders off the east end of the bridge and roll out 300-foot-long sections,” Gegick explained. “They’re about a quarter-million pounds apiece once they connect two smaller sections.”
The further construction progresses to the west, the longer it takes. “The gantry cranes go about walking speed at four miles per hour,” Gegick said. “The last section will probably take an hour from the time they pick the girders until they set them.”
As the gantry cranes roll out the girders, “They need to keep the load on each of the cranes approximately the same in order not to overload the bridge underneath any given crane,” Gegick said. However, “The existing bridges deflect at different amounts at different positions. In the middle of a span it deflects the most and as they get close to the pier, it deflects the least. That changes the load between each of the gantry cranes.”
To avoid problems, “Walsh had to come up with a maximum allowable differential and readjust the loads as needed,” Gegick said. “All the gantry cranes are coupled together. At times, loads can approach the allowable differential because the deflection under one crane can reduce tension on the cable, causing the other gantry cranes to experience increased tension and pick up more load. At that point, the operation is halted and the cranes decoupled while the crane loads are adjusted to be safely within their tolerances, then the cranes are recoupled before continuing.”
Once the cranes start moving, lasers keep them the exact distance apart. The middle operator controls all three cranes, while the other operators monitor their own readings and rigging.
Because of the complexity of balancing the loads, girder deliveries can’t travel across the bridges while the gantry cranes operate. “There are also limitations on their own work vehicles being up on the bridges while they’re using the gantry cranes,” Gegick added. “They had to build their schedule around that.”
Completing the Decks
To build the three bridge decks, “We gave the contractor a choice of stay-in-place metal forms or more conventional wood forms that they’d strip when they’re done,” Gegick said. “Because the bridges are so high, the cost of stripping the wood forms is very large.”
The design-build team chose the metal forms, which include flutes for concrete that create extra load. “On the new bridge, they designed the structural steel strong enough to handle the load so we could use standard concrete,” Gegick said. “On the existing bridges, the structural steel wasn’t sufficient for the extra load of normal concrete in those flutes, so we allowed them to use lightweight concrete for the deck.”
With the project currently ahead of schedule, “We plan on shifting traffic from the eastbound bridge onto the new bridge sometime this fall,” Gegick said. “We hope to pull the deck off the eastbound bridge by the end of next winter and then redeck it. In fall 2021, we hope to put eastbound traffic back on the new eastbound deck, shift westbound traffic onto the middle bridge, and redeck the westbound bridge in 2022.”
Traffic will then go back to its original configuration while crews install barrier wall down the center of the new bridge for bi-directional traffic.
“Our contract requires the contractor to open all three bridges by the end of 2023, and they’re allowed up to June 2024 to finish painting and other minor operations,” Gegick said.