Shatter-Proof Glass

Nov. 1, 2006

Noses, fingers and hands. Toledo is free to smudge with all of them. Those involved in the Veterans’ Glass City Skyway Bridge have even provided a clear viewing area to lean into. Not far from the jobsite lies a grassy area free of obstruction and complete with picnic tables. The gawkers have been populating since construction began back in 2001.

Noses, fingers and hands. Toledo is free to smudge with all of them. Those involved in the Veterans’ Glass City Skyway Bridge have even provided a clear viewing area to lean into. Not far from the jobsite lies a grassy area free of obstruction and complete with picnic tables. The gawkers have been populating since construction began back in 2001.

“The bridge will certainly be a postcard for the city of Toledo,” Michael Gramza, P.E., project manager for the Ohio Department of Transportation (ODOT), told Roads & Bridges. “The awe that is seen from everyone who visits the project amazes me. We have probably had over 15,000 people come and tour [it].”

The region certainly knows how to act around glass. For decades, Toledo was one of the major glass manufacturers in the world. Much of the industry has left, but the citizens wanted something to look back on—or, in this case, look up on. Rising from public forum meetings was a glass-clad pylon structure that will carry I-280 and, when completed, may just be one of the most dynamic in the state of Ohio.

“This is just an amazing experience,” Wade Bonzon, P.E., field engineer for FIGG, Tallahassee, Fla., at the Veterans’ Glass City Skyway Bridge, told Roads & Bridges. “It’s the kind of project most engineers wait their entire life to work on. I cannot wait for the bridge to be done and for the people of Toledo to really take a lot of pride in it, because it is really spectacular.”

But even the spectacular can put on a serious face. A fatal accident, trouble with the 10,000-psi mass concrete and epoxy-coated strand and a Thanksgiving Day gasoline spill had the project needing urgent care. Despite the setbacks, designer FIGG, prime contractor Fru-Con Construction Co. and ODOT have worked together to re-inflate the strong showing of accomplishment reaching over the Maumee River.

Autumn life

As of early October, crews were completing the installation of cable stay No. 10 of 20 on the Veterans’ Glass City Skyway Bridge. At 727 ft long, the stay contains 149 high-strength steel strands of cable and will be encased by 315 ft of stainless steel cable stay sheathing.

A unique high-line system is used to install the stainless steel sheathing pipes, which range in size from 70 to 600 ft long. The pipes start out in 30-ft lengths and are welded together to form the desired length. To speed up assembly time, some of the welding is done in a storage warehouse. That stretches the length to 90 ft and the rest of the connection is done on the bridge deck. The high-line system looks like a temporary cable stay that anchors near the top of the 400-ft glass pylon. Coming off the temporary stay are hangers that come down vertically, and crew members attach slings to various points along the sheathing. A winch cable is threaded through all of the hangers so the pipe is picked up at various support points simultaneously, tilting the stay sheathing to the correct angle on the bridge.

Fru-Con was installing one cable stay every six days.

The bridge is the first in the U.S. to use stainless steel as stay-cable sheathing. ODOT decided on using the stainless steel material despite higher initial cost.

On the main span, crews have erected 34 segments on both the northbound and southbound cantilever, with 30 more to go on each alignment. In mid-October the cantilever covered 327 ft of its designed 612-ft length.

Delta frames are being used as anchor points for the stays. The frames, invented by FIGG, allow for the installation of twin box girders instead of one giant one.

“It allows you to keep those segment weights down to a reasonable level and makes erection much simpler,” said Bonzon.

A total of 42 frames—21 in the back span and 21 on the cantilever side—will be installed. Crews had all 21 in the back span in place in mid-October and had 10 more to go on the cantilever.

The bridge is designed for one continuous cable with two anchorages, with 20 stay cradles embedded in the pylon. The cradle transfers the loads to the pylon similar to a saddle pipe. Previous cable-stay bridge designs called for the use of saddle pipes to run all the cable strands through and stress them all with a giant jack. However, the Federal Highway Administration was concerned that the strand-to-strand interaction in a saddle pipe would cause fretting corrosion.

“We wanted to run the strands continuously through the pylon and then back down to deck level, but we also needed to keep the strands from interacting with each other,” said Bonzon. “That’s why FIGG developed the stay cradle system, to avoid putting anchors in the pylon and still keep the strands separate from one another.”

A positive side benefit of the stay cradle system is, because they are running parallel to each other, the strands can be replaced one at a time. Each stay is being installed with two extra reference strands that ODOT could pull for future inspection.

As work moves closer to installing cable stay No. 20, the glass panel, or “lites,” will be arriving at the jobsite for placement on the pylon. The glass lites are typically 4.5 ft tall, 7.5 ft wide and 11?4 in. thick. Each of the four faces of the pylon will contain 44 glass lites, and a total of 176 separate pieces will be moved into place with a crane and clamped into position.

The LED lighting system running through the pylon will allow different color combinations to be displayed at the flick of a switch. Bonzon said as of mid-October, some conduit runs and junction boxes, which form the backbone of the system, were ready to go. The LED lights will be installed in the late winter or early spring of 2007.

For the approach erection work of the bridge, four spans were left to be complete south of the Maumee River and five north of the river. Both sides were expected to be finished by mid-November.

If crews stick to the schedule, the main span should be complete by Jan. 13, and the bridge could be open to traffic as early as February, making it less than five months overdue. However, considering the string of mishaps over a two-year period, the missed September 2006 deadline is lost in the impressive rallying effort executed by the designer, contractor and owner.

Recovery efforts

On Feb. 16, 2004, tragedy temporarily discolored the promise of the Veterans’ Glass City Skyway Bridge. A giant gantry crane—designated LG-2—collapsed and killed four ironworkers while launching forward to the 12th northbound span.

OSHA later cited Fru-Con for not anchoring the gantry according to the manufacturer’s written procedures. After the accident, Fru-Con did a thorough top-to-bottom review of a twin erection gantry, the LG-1, which was erecting southbound approach spans alongside LG-2. Experts came in to inspect the site and watch the launching procedures.

When the crane was cleared for operation, a small winch cable broke, causing the front leg to slide out. That is when the contractor decided to reconfigure the entire way the gantry operates. The goal was to simplify the operation.

Before the accident, the gantry was designed so the contractor launched it forward on top of a pier cap. From there, the gantry would place the precast pier segments for the superstructure onto the pier cap.

“The leg [of the gantry] would then move up onto those pier segments,” said Bonzon. “Those are heavy segments and it added several steps to the launch process.”

It took up to a day and a half to set the pier segments and complete the launching cycle.

“What Fru-Con ended up doing was to pre-erect all of the pier segments up on top of the piers ahead of time using a ground-based crane, so when the gantry was advanced out over the pier it didn’t have to perform those operations itself. They could set the leg down onto the pier segments that were already there. It reduced a lot of the complexity and speeded up the span-by-span erection process.”

The contractor also went with a change of personnel. After the accident a new project manager was brought on board, leading to a change in perspective. “The first few months we had a lot of concerns of uncertainty,” said Gramza. “Then Fru-Con brought in a new project manager and one of the first things he looked at was what kind of equipment needed to be on the project. I thought that really helped.”

Joining the LG-1, now the AG-1, was a second overhead gantry designed by Strukturas and used previously in Malaysia. Fru-Con also brought in an underslung truss to speed up completion of the project, and erected nine spans critical to the project’s schedule on falsework. All four working together pushed the project into its current rhythm.

Problems, however, did not stop occurring. Shortly after the gantry collapse, the contractor ran into trouble achieving the required 10,000-psi compressive strength of the concrete on the first two lifts of the pylon above the bridge deck. Readings were coming in at 7,500 psi.

“At that location, you are at a critical section for the upper portion of the pylon,” remarked Bonzon.

Bonzon said they were experiencing strong break results all the way up to the first and second lift above deck. “Then all of a sudden it was real low. There has never been a definitive reason established for the low break results.”

Fru-Con brought in a subcontractor that specialized in the demolition of concrete structures. The subcontractor had a system where it would drill holes through the concrete and then run a loop made of a thick cable that contained industrial diamond-encrusted beads with a pully and a winch. The loop ran continuously through the concrete to create a smooth cut. So that crews could use the rebar coming up out of the deck-level pour, the specialty subcontractor jackhammered the last 4 ft 8 in. of weak concrete. In all, nearly 60 5-ton blocks were removed.

The mishaps continued while crews were putting together cable stay No. 1. A cleaning rag snagged while it was being used to wipe down the strands, revealing cracking in the epoxy coating. As of mid-October, ODOT was in the process of getting replacement strands from supplier DSI. When the new material arrives, which Gramza predicted could be during the setup of cable stay No. 16, the contractor will go back and replace all of what was installed earlier, pulling them out strand by strand.

“People asked us why we wouldn’t wait until we had the new cable,” said Gramza. “Stringing the cable is only a day to a day and a half of the week-long erection cycle. It’s much more efficient to continue to build the bridge and then come back and replace the damaged strands later.”

Fru-Con was receiving 165,000 ft of cable every two weeks, which is enough to form one cable. If the shipment schedule does not change, the cable replacement could be completed by April. However, if delivery is slow, it may be as late as June. ODOT will probably replace the strands while the bridge is open to traffic.

The Thanksgiving 2005 gas spill was one incident completely disconnected from the bridge work. Right alongside on-ramps on the south end of the project lies a facility that receives gasoline from a local refinery. During the Thanksgiving holiday, gas was pumped into a tank that was already full, spilling 103,000 gal of fuel. The EPA tabbed it the largest spill ever in the state of Ohio. The company had to remove 30,000 cu yd of dirt and treat the ground on their property. The spill also leaked into the bedding of ODOT’s storm-water drainage system. Instead of ripping it out, the agency worked with the EPA and brought in a vapor-extraction system.

“When you are on a huge civil engineering job like this, things are going to happen,” explained Bonzon. “You are going to have issues. You can never get through anything without dealing with some kind of challenge. You learn from them and press forward.”

Come the summertime, the biggest challenge might be trying to control all those awe-inspiring smudge marks.

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