Better Bridges: Building blocks for bridges
Does new technology mean new problems?
Doehring says UDOT has been using Geofoam extensively since the late 1990s and compromised safety hasn’t been a problem. “We’ve been monitoring it closely and haven’t had any issues with it,” he says. The one concern that could potentially cause a problem was addressed prior to any installation of the material. “It is susceptible to damage from petroleum products, such as if a diesel tanker were to spill on the road and it seeped down,” Doehring says. “It could melt away our fill slope.” Pouring a concrete cap on top of the Geofoam and then sealing it with a membrane — a big rubber sheet on top of it, solved this prospective problem. “This keeps any petroleum products from making its way down to the foam,” he says.
A material as lightweight as Geofoam has the appearance of not being very strong, thus, raising concerns about its ability to handle loads. However, the lightweight material has strength comparable to traditional soil as well as foamed concrete, waste tires, woodchips and wood fiber.
To address the issue of bridges with ABC technology needing added maintenance — a real concern for many agencies who already have a strapped budget and a skeleton crew of personnel — Doehring says, “We’re designing these as much like traditional bridges as we can so we don’t have to do anything special to them.”
However, he says, “We are still fairly new to these ABC methods. This is a new area and new techniques are being used. I don’t think there will be any additional concerns, but it is important to keep an eye on it. We’ll see in the next 10 to 15 years if we need to do anything differently.” v
Just when you think…
Just 48 hours before the bridge was set to be moved 1.5 miles down city streets — and over utilities — by a 256-wheel Self-Propelled Modular Transporter (SPMT), one of the utility owners told the Utah Department of Transportation (UDOT) it wouldn’t allow the superstructure to be moved across the area. “We had talked with the city, had talked to all of the utility people and had clearance from them to move this bridge,” says Fred Doehring, deputy bridge engineer for the Utah Department of Transportation. “But then one of them said we couldn’t drive over that area, even though we had the permit.”
“Utility owners get very scared then a 2 million pound bridge coming down the road,” Doehring continues. “But the way we move the bridges [on the SPMTs], the per-wheel-load is less than a garbage truck.”
This was a learning experience for both UDOT and the contractor. “We talked to the people at the normal number we call when working on projects,” Doehring says. “But it turns out that we were talking to the low-pressure gas line people when we needed to be talking to the high-pressure gas line people. We did everything we could and were supposed to do, but apparently, we needed to do more.” Adds Bryan Jensen, field engineer with Ralph Wadsworth Construction, which was the contractor for the I-215 Bridge at 330 South: “Some of the biggest headaches are coordination efforts.”
The lesson learned? “You have to make sure you are talking to the right people in the organization,” Doehring says, adding that even if the person at a DOT who is coordinating a project is working with the person with whom he or she typically contacts, it’s necessary to verify and re-verify that someone else does not need to be contacted. The problem with the utility company was solved “though a lot of heated negotiations and studies to show that we wouldn’t damage their pipe,” Doehring says. “We compromised and ended up putting steel plates over their pipe. We didn’t feel it was necessary, but we did it to keep them happy. We definitely learned the need for constant good communication with utility owners and local governments.”
An Oregon ABC project:
Why some bids are about more than money
Steven Narkiewicz, project manager and engineer with the Oregon Department of Transportation (ODOT), explains why Accelerated Bridge Construction (ABC) — also known as rapid replacement is important and what his agency looks for when deciding which contractor to award a job. After ODOT attended a joint Highways for Life (HfL)/Federal Highway Administration (FHWA) conference about the Utah Department of Transportation’s (UDOT) success with rapid reconstruction on several of its state bridges, ODOT adopted the technology.
ODOT built two bridges on temporary fixed supports off to one side of the existing bridges for the Oregon 38 Elk Creek to Hardscrabble Creek bridge replacement project, which used ABC.
“We built the entire structure on a temporary fixed supports, built rails under both the old and new bridges, and used jacks to put them into place using a hydraulic jack system that goes sideways,” Narkiewicz explains. “In its simplest form, its sliding things with jacks and rails. In more sophisticated forms, computerized wheeled devices are used.
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