Fixing, aging, structurally deficient bridges has become a challenge for departments of transportation across the country. The federal government reports about 58,495 bridges, carrying nearly 204 million vehicles daily, are structurally deficient and in need of repair. To keep those bridges functioning costs departments billions annually. Transportation departments, academics and contractors are looking for solutions that will save funds and ease the pain of closing bridges for repairs or reconstruction.
“These bridges being rated deficient are at a rate faster than we can repair them, because we are limiting ourselves to oldfashioned repair methods,” says Arash Esmaili Zaghi, PhD, PE, assistant professor at the University of Connecticut in Storrs. “It’s time to move on to the next step and start using more advanced materials and methodologies.”
NOVEL REPAIR METHOD FOR CORRODED GIRDERS
Zaghi and colleagues at the University of Connecticut Department of Civil and Environmental Engineering recently completed a research project for the Connecticut Department of Transportation, which maintains 4,182 bridges, that could significantly reduce costs, time and lane closures.
Corrosion of the steel-girder ends at the bearing is one of the most prevalent deficiencies on the nation’s steel-girder bridges. The damage can lead to failure. Traditional repair methods include cover plates or adding steel shapes. Those methods require paint removal, and due to the age of the bridges, that often means lead paint and extensive abatement before any repairs can be made. Then, crews must jack up the bridge decking, a significantly costly and labor-intensive process that also disrupts traffic flow. Each project requires a custom design because of different geometries.
During meetings with ConnDOT and UConn, an idea came forward to encase the corroded web plate of beams or girders in ultra-high performance concrete. The process includes welding shear connectors to the girder and then pouring ultra-high performance concrete on the sides of the steel web. Zaghi’s research team came up with an experiment design to prove the concept will work. They began with three large-scale tests performed on intact, damaged and repaired girders.
The researchers report the repair successfully restored the damaged girder’s bearing capacity, saying, “The capacity of the repaired girder exceeded the capacity of intact girder by approximately 25 percent.”
Ultra-high performance concrete is available in the marketplace. For the testing, UConn used Ductal JS-1212 designed by Lafarge, a French company with U.S. offices in Chicago. It contains “premix powder; water; Premia 150, a modified phosphonate plasticizer; Optima 100, a modified polycarboxylate high-range water-reducing admixture; Turbocast 650A, a non-chloride accelerator; and steel fibers,” with a diameter of 0.008 inches and a length of 0.5 inches, according to the report by Zaghi to ConnDOT. The mix flowed well and was self-consolidating. Zaghi indicated it is nearly five times as strong as regular concrete and sets in 12 hours.
“In this repair method, two panels will be cast on the I-beam to transfer the loads at the bearings of the bridge,” Zaghi explains. “This concrete is highly durable and strong; it transfers loads and protects the base steel.”
Zaghi indicates this repair can be completed during a weekend, while the bridge remains open to light traffic.
The department received a $676,690 grant for the second phase of the research, designed to address several technical aspects to optimize the design and facilitate the implementation of the repair. ConnDOT and UConn will soon field test this repair methodology. They are narrowing down a list of bridges that could be used as a pilot project.
“There is confidence this can be done,” Zaghi says.
The American Association of State Highway and Transportation Officials awarded ConnDOT a 2016 Sweet Sixteen award for high-value, innovative research. More than 120 projects from state-level departments of transportation vied for the recognition.
The system does not require original engineering for each bridge. Zaghi estimates the state will be able to repair four to five bridges with the new ultra-high performance concrete casts for the same amount of money as one traditional bridge repair. UConn will monitor the repaired bridges long term.
Neither Zaghi nor UConn have submitted a patent application, because he says, the process should be available to the public.
“It can significantly benefit the safety of our bridges,” Zaghi says. “It is pretty exciting, because it is addressing one of the most critical challenges we have with these aging bridges.”
For the first time in over a decade, there is a long-term authorization of federal highway and transit programs in place following President Obama signing the five-year $302 billion Fixing America’s Surface Transportation (FAST) Act into law on Dec. 4, 2015. The FAST Act was a direct result of the years of effort AGC members and their employees spent convincing their representatives and senators about the importance of a long-term and well-funded transportation bill. Part of the success could be contributed to the Hardhats for Highways grassroots program as an integral part of the industry’s collective efforts on the bill. Please visit the www.HardHatsforHighways.org for an AGC overview of the FAST Act along with other FAST Act resources.
TOP-DOWN BRIDGE REPLACEMENT
When the Oregon DOT needed to replace the dual span Sandy River Bridges on Interstate 84 at the gateway to the Columbia River Gorge National Scenic Area without risking flooding of nearby homes, Hamilton Construction Co., in Springfield, Oregon, came up with an innovative top-down approach. The $58 million project received an Alliant Build America Award.
“From start to finish, it never got easy; it was a tough job,” says Joe Hampton, project manager with Hamilton. “We had a good team of people and we all put a lot of effort and time into it.”
The company purchased and modified a pair of 250,000-pound lift capacity gantry cranes, each weighing 100 tons, to launch the 165-ft steel girders from the shore. The gantry cranes spanned the 90-ft wide bridge superstructure and ran along a fabricated 900-ft long traveling rail that allowed for top-down placement of the 49 new steel-tub girders, bolted together, with more than 800 bolts at the site by Hamilton crews. This cut the need for piles in the river from 100 to 12.
“To get it built and rigid enough to withstand the river and keep the pieces away from the bridge we were going to build was a feat,” Hampton recalls.
The system eliminated the need for a second temporary work bridge and reduced the flood risk potential associated with additional piles in the river. It shaved nearly five years off of the project schedule, with crews able to work year round. Endangered fish would have allowed a narrow 45-day in-water work window.
“The gantry was innovative,” Hampton says. “Everything is built up at a high level.”
Hamilton has used the girder launcher, but not the gantry crane, on three other bridge projects, again eliminating the need for building work bridges and the environmental disruption they create. The company also has fabricated a bubble curtain into a circular piece of equipment and drove the piles through the center of it to reduce the negative effect of pile driving on fish.
SLIDING A BRIDGE INTO PLACE
The Walsh Group in Chicago received an Alliant Build America Award for its $104-million Milton Madison Bridge Replacement Project in Madison, Indiana, for the Indiana Department of Transportation and the Kentucky Transportation Cabinet. The company built the new bridge adjacent to the old bridge, connecting Madison, Indiana, and Milton, Kentucky, and then slid the new 30-million pound one into place. The idea, which reduced the nearly half-mile long bridge’s closure from 365 days to a few weeks, gave Walsh an advantage during bidding.
It is the only crossing on a 72-mile stretch of the Ohio River. The plan also saved money, with the Walsh bid $20 million less than the original estimate.
“It was a competitive advantage to us,” says Doug VanSlambrook, a project manager with Walsh.
Walsh preassembled the two main truss spans on temporary piers, about 55-feet upstream from the existing bridge. The bridge is 2,429-ft long and 40-ft wide with two 12-ft wide travel lanes and 8-ft wide shoulders. Walsh rehabilitated the piers on the existing bridge during the 14-month project.
Crews secured polished steel sliding plates on top of the five refurbished piers. Steel cables and eight computer-controlled hydraulic strand jacks were used to pull the bridge through a series of grabs and pulls until the bridge slid into its new position.
“It’s a nice, safe and efficient method, if you do the amount of planning on the front end that is required for that type of procedure,” VanSlambrook says. “Our lateral slide of the bridge broke North American records for the longest span.”
PRECASTS AND RINGER CRANES
On the $398.5 million Pensacola Bay Bridge replacement project for the Florida Department of Education, Skanska USA, based in New York and a member of multiple AGC chapters, plans to use an A-frame system with GPS and conventional survey equipment for installing the 30-inch and 36-inch precast concrete piles. The company also will precast the foundation, columns and caps as one unit and erect and connect each 132-ton foundation unit by crawler cranes with ring attachments.
“The ringer attachment spreads the load over a wider footprint of the crane to add additional capacity,” says Jay Erwin, vice president of operations for Skanska and project director.
Design-build partner WSP | Parsons Brinckerhoff of New York, designed the new 3.7-mile-long bridge, connecting Pensacola with Gulf Breeze. It will feature three lanes in each direction, replacing a 1960s-era bridge with two-lanes in each direction. Construction began in September 2016 and is expected to complete in August 2020.