Above: The upper sections of the bridge towers on the Stonecutters Bridge in Hong Kong are formed from a composite structural section of reinforced concrete and 2205 duplex stainless pipe from Outokumpu.
Updating vital highways and bridges with new construction techniques and materials has myriad benefits
August 2013 - Thirty years ago, an 100-foot section of the Mianus River Bridge in Greenwich, Conn., fell into the river below, leaving a gaping void in the passage. The cause of the collapse was a failed pin-and-hanger assembly—a construction technique that is obsolete today.
According to the American Society of Civil Engineers, Reston, Va., “over 200 million trips are taken daily across deficient bridges in the nation’s 102 largest metropolitan regions. In total, one in nine of the nation’s bridges are rated as structurally deficient, while the average age of the nation’s 607,380 bridges is currently 42 years.”
Although bridge failures still make the news today, statistics from the ASCE show the percentage of functionally obsolete or structurally deficient bridges has been declining over the last 10 years as states and cities have prioritized repairs and replacements. The ASCE defines functionally obsolete bridges as structures “that no longer meet the current standards that are used today.” This categorization includes bridges with narrow lanes and low load-carrying capacity. Structurally deficient bridges “require significant maintenance, rehabilitation or replacement,” in addition to yearly inspections because critical load carrying elements are in poor condition.
Economic impact
Safe, up-to-date bridges provide numerous economic benefits, which is why many states are choosing to fund these projects. Louisiana recently completed the $1.2 billion widening of the Huey P. Long Bridge in New Orleans, an expansion that began in 2006, shortly after Hurricane Katrina. The project increased the amount of driving surface from 18 feet wide to 43 feet wide. The bridge now is capable of carrying twice the amount of traffic—more than 100,000 vehicles per day.
“The importance of the bridge cannot be overstated,” said New Orleans Public Belt Railroad General Manager Jeffrey D. Davis in a press release. “In one year’s time, a total of 393,544 railcars traveled across the bridge. Included in that number were 374,597 freight cars, 16,498 freight locomotives, 1,891 passenger cars and 558 passenger locomotives.”
Jyll Smith, stakeholder engagement strategist for the Oregon Department of Transportation points out, “By preserving essential freight routes, over which 70 percent of Oregon’s goods travel, ODOT is enhancing and protecting the state’s economic vitality by allowing businesses to effectively and efficiently get their products to market via the interstate highway system.”
Smith notes in addition to keeping lines of trade open, the work of repairing and replacing bridges stimulates the state’s economy. Based on recent estimates, about 12.5 family-wage jobs are sustained for every $1 million spent on transportation construction in Oregon. Through 2012, Oregon’s OTIA III State Bridge Delivery Program has sustained more than 20,000 jobs.
Delaying updates to aging bridges can negatively impact a state’s economy. Smith says the bridge program was funded, in part, as a result of lessons learned in the early 2000s.
As ODOT recounted in its 2003 Economic and Bridge Options Report, for 20 days in March 2002, the small southern Oregon communities of Canyonville and Riddle experienced a surge in truck traffic. Ford’s Bridge, on Interstate 5 several miles away, was restricted to one lane in each direction for emergency repair, and the towns’ main streets became the primary detour route.
The narrow streets were not designed to accommodate large trucks, and the detours added miles to the haulers’ trips. ODOT fast-tracked the bridge project so truck traffic could return to the interstate, but Smith says “the situation illustrated how much more cost-effective it would be to coordinate needed repairs to all the state’s aging bridges rather than addressing one at a time.”
New construction techniques
Advances in engineering create bridges that are lighter, easier to fabricate and safer to construct. In addition, design engineers are paying attention to the sustainability and life-cycle costs of these projects. Smith gives some examples of new processes used in Oregon to meet and exceed goals for cost-effective and efficient operation and stewardship of communities and natural resources.
She says a bridge on Oregon 38 was replaced using rapid replacement in part because there was no room for a detour structure. “To avoid subjecting local residents, freight traffic and tourists to long detours or prolonged lane closures, ODOT chose rapid replacement, during which crews build a new bridge beside the old one and then, during a short closure, slide the old bridge out of the way and the new one into place.” This allowed ODOT to close the highway for only one weekend and reopen it for traffic nine hours earlier than scheduled.
Top-down beam setting allowed a crew working on Interstate 84’s Sandy River Bridge to continue construction without a work bridge, further alleviate flood plain concerns and avoid interfering with fish migration and breeding, Smith says. Typically, a crew would build detours and work bridges to reroute traffic, but this structure is located in a wide and shallow basin that’s vulnerable to flooding. To solve a unique problem, the team came up with a unique solution: set the beams from a crane that operated within the linear footprint of the bridge being built.
“Specialized twin gantry cranes, constructed on-site for the project, hooked, lifted and placed steel beams measuring up to 167 feet long and weighing up to 192,000 pounds,” Smith says.
Noise generated by heavy equipment can disrupt fish and other river creatures, negatively affecting their communication and migratory patterns. “After consulting biologists from the Oregon Department of Fish and Wildlife, contractors on the bridge program chose to quiet their in-water construction noise with a creative solution: bubbles,” Smith says.
On ODOT’s largest bridge replacement project to-date on Interstate 5 in Eugene-Springfield, prime contractor, Hamilton Construction built and christened a custom-made “bubbleator.” A circular device constructed of sheet metal and lined with high-density polystyrene foam, the bubbleator is framed with aluminum pipes that produce a thick wall of bubbles. The bubbles dampen the sound from pile strikes around each two-pile template. The size of its frame also serves as a safe, sturdy work platform for crews to stand on during pile driving. Hydro-acoustic monitoring on projects where the bubbleator was used showed that it maintained noise levels below thresholds required by ODFW.
Long lifespan
As state departments of transportation look to increase the life span of bridges, they’re considering stainless steel for both structures and reinforcement. “The life expectancy of a bridge using black steel or epoxy coated is 30 to 50 years, and with the new construction and the replacements and renovations, they’re looking to extend that lifetime. Today it is common for engineers to consider a design life of a minimum of 75 years and in some cases in excess of 100 years,” says Tom Holsing, product manager, rebar and wire rod, Outokumpu High Performance Stainless Bar–North America.
As a result, “in North America, there has been growth in the stainless rebar market and certainly a lot more interest in using stainless steel in bridges, not just for reinforcement but also in structural components,” he says. A recent reinforcement project for the company was the Athabasca II River Bridge in Fort McMurray, Alberta, Canada, Holsing notes. According to the contractor, Flatiron Construction Corp., the 108-foot-wide, 1,548-foot-long bridge deck is the largest in Alberta and can accommodate more than three times the average weight of most bridges.
Worldwide, Outokumpu also is seeing an increase in bridge constructions specifying stainless. The company’s products have been used in large projects such as the Helix Bridge in Singapore, the Gateway Bridge in Brisbane and the Stonecutters Bridge in Hong Kong, in addition to pedestrian bridges.
The biggest obstacle to more widespread use of stainless is education, Holsing says, informing design engineers “which materials are available and which materials make the most sense from a strength and corrosion-resistance standpoint but also from a commercial standpoint—which materials provide the best value.
“We’re involved with the Federal Highway Authority, where we participate in seminars for generalized corrosion-resistant rebar that the FHWA sponsors, at the different DOTs,” Holsing continues. “We’ve done probably seven or eight seminars in the last year or so. We just finished one up in Maryland, and we’re doing one in New York in August. We’re talking to engineers specifically about duplex stainless alloys because we feel these alloys give the user the broadest benefit of strength and corrosion resistance as well as the best commercial value.”
Holsing says one of the common questions he receives is how long the material will last. “We promote stainless steel in areas where corrosion is an issue as a result of road salts or marine environments, primarily, although other environmental issues may also factor in. In concrete, chlorides are the primary concern for carbon rebar and creates the corrosion in the first place. Thus, stainless becomes a better consideration.
“We talk about the life cycle cost of stainless steel versus other materials primarily because stainless steel and our duplex alloys, generally require a lot less maintenance,” he continues. “With a design life of 100-plus years, you’re looking at basically little or no maintenance on the structure itself. You might have to fill some potholes in the concrete, but you’re not tearing a bridge down or shutting a bridge down to replace a bridge deck or barrier walls or other components that might be suffering from corrosion. .... The Federal Highway Authority has a saying: Get in, get out and stay out. They like to use that commentary when they’re talking about having to go in and replace or build new structures, especially in highly populated or high-traffic areas where shutdowns can become very expensive very quickly.”
“For structural use of flat products, our challenge has been that all the existing building codes around the world for bridges and structural components have only been developed to a limited degree to utilize the properties of stainless,” says Poul-Erik Arnvig, vice president, market development for Outokumpu High Performance Stainless North America, Itasca, Ill. “It’s a long-term project to change it. There is a European building code for stainless steels, but since it was developed 10 or 15 years ago, it was made with quite a lot of extra safety factors because people didn’t have practical experience with the material. There’s a second version out now and a third version under discussion. We’re coming closer to the norm, taking away some of these safety factors because they’ve seen many of these smaller bridges behave as expected.”
Arnvig also notes this year there is a guideline being released from the American Institute of Steel Construction for stainless steel thick structural sections. “While that may not be the final step to having a full design guide for a stainless steel bridge, it’s definitely a big step toward getting more interest. The guideline also makes it easier for the construction engineers to consider stainless and utilize stainless based on rules and guidance that they’re used to following and that automatically incorporates the advantageous properties of stainless steels—and duplex stainless steel in particular.” MM
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