"To Get to the Other Side," Feature Article, April 2006

to get to
the other side

Sometimes you have to plan how to cross your bridges before you come to them.

by Harry Hutchinson, Executive Editor

there's a song, "Sur le Pont d'Avignon," about people—from dames and messieurs to gardeners, laundresses, and vine trimmers—all dancing on the bridge at Avignon. It's an old song with a catchy melody. It probably refers to a one-time landmark bridge built during the 13th century on the site of an earlier one laid down by a saint. The bridge is gone now, but the song remains, to remind us that bridge-building goes back a long way in France.

The old bridges have not all vanished. There are many historic structures in daily service on French roads. They can hold up under considerable dancing and moderate day-to-day traffic. They were never expected, though, to bear trucks carrying machine parts that weigh almost 300 metric tons. Few bridges of any age are ready for that.

Engineers and workers (above) guide an extraordinary load across a bridge on the route between Port-la-Nouvelle and Pamiers, France. Hydraulic lifts on the trailer transfer about 140 metric tons of the load through the improvised track directly to the bridge piers. Long spans on a curve (below) proved to be a special test for the system, which was developed by Wirzius Heavy Assembly and Greiner Vehicle Technology.

Aubert & Duval Group, a supplier of parts, steels, and other materials to a range of industries, had to find transport for eight machine components of that scale. They were castings for new 40,000-ton forging presses, which the company needed to move from a Mediterranean port to its new factory in Pamiers.

The presses will forge fan disks for turbojet engine manufacturers, and it is expected that some of the engines will power Europe's new supersize jet, the Airbus A380. This operation, called Airforge, joins another Aubert & Duval plant already operating in Pamiers.

According to Bernard Finas, project manager for what the company calls "the Airforge 40,000-ton project," the presses have been assembled and are due to begin operating in July.

Aubert & Duval ordered the machines from Siempelkamp Press Systems of Germany. The forgings and castings were the work of Japan Steel Works, which sent the finished parts to Port la Nouvelle, near Narbonne on the Golfe du Lion on the south coast of France.

P. Wirzius Heavy Assembly GmbH of Hinden, Germany, had the job of transporting the presses overland and assembling them at the factory in Pamiers, south of Toulouse.

GETTING THE GREEN LIGHT

Some of those historic bridges made it impossible to take the most direct route from the seaport to the factory, so Wirzius mapped out a route that, although roundabout, ran on major highways. Even on the modern roads, however, a vehicle of more than 400 tons needed special waivers from French authorities before it could set out. Delivering the presses, though, was considered important to the nation, so the trip received a green light.

According to Wirzius, the route was about 230 km by road. The route included five crossings that were not up to the load of a trailer bearing one of the huge press parts, a gross weight of 430 tons.

To find a safe way to cross its bridges, Wirzius enlisted a specialist in getting heavy objects safely to their destinations, Greiner Vehicle Technology, an engineering company based in Neuenstein, Germany. Greiner says it designs systems for transporting large machinery by road or rail. That, in fact, is what the company's bridge-crossing solution involved, both road and rail, but not in a conventional sense.

Michael Greiner, the company's CEO, said his engineers could either strengthen the bridges or find a way to reduce the stress on them. Rather than trying to rebuild or shore up the structures, the company took the second course, which is where the rail part comes in.

Working with Wirzius, the Greiner company devised a plan to transfer some of the extraordinary vehicle weight to a temporary track system that would channel that part of the load directly to the bridge piers.

According to the Greiner company's executives, the timeline of their job for Wirzius meant that they needed to have as many parts of the project as possible taking place at the same time. To make things a little more challenging for Greiner, when it took on the job, the company was switching its design software from a 2-D system to a 3-D product, OneSpace Designer Modeling, from CoCreate Software in Sindelfingen, Germany.

A JUMP ON PRODUCTION

The change went well, according to Michael Greiner. "While we were still designing, we were running the production line," he said. "Some local suppliers were also producing individual components even before the entire design was complete."

Given that the company had to have a workable system ready for Wirzius in less than a calendar year, the jump on production was necessary.

According to Jochen Sailer, technical designer at Greiner, engineers working in 3-D simulated the system in motion and avoided problems, like collisions, that would otherwise have needed correction later.

Crews from Greiner and Wirzius tested the system at the former Butzweilerhof Airport in Ossendorf. A transport vehicle had to transport 295 tons of ballast across a 148-meter track. The next day, they repeated the test as a demonstration for French motorway authorities.

A CAD rendering of the hydraulic lift system and track design. Greiner was adopting new 3-D software, from CoCreate, during the project.

Transport from Port la Nouvelle to Pamiers started with two castings, each lifted by an 800-ton hydraulic gantry onto a separate Goldhofer platform trailer. Each trailer had 20 lines of swing axles three across and was driven by a tractor fore and aft. Each trailer also carried a hydraulic gantry, with two cylinders in front of the casting and two close behind. They would be the means of transferring weight from the road to the track.

The convoy included a fleet of trucks that carried the parts of the track. Wirzius calls it the Roll-On, Roll-Off system and holds patents for it.

The temporary track was designed to cover spans as great as 60 meters. The first crossing had two central spans of 27.8 meters each. The track-building team began by laying steel mats at load-bearing points on the bridge. The rails over the mats were box girders 1.5 meters high with bolt-and-flange couplings. This bridge needed a total of eight for each side of the track—five that were 10 meters long and three 8 meters long. With the help of a crane, team members jockeyed the pieces into place.

Once the track was secure, the gantries on the trailer came into play. They extended outward and then brought down steel wheels onto the improvised tracks. The four hydraulic cylinders of the gantry transferred a total of about 140 tons of the load to the track system, which channeled the weight directly to the bridge piers. The bridge surface held the remaining 290 tons.

STAYING INSIDE THE LINES

The team disconnected the tractors and used a truck-mounted winch to haul the trailers one at a time across the bridge at a rate of about 4 meters a minute. Observers accompanied each trailer to make sure the wheels followed reference lines painted on the road.

The convoy did that five times along the route, over spans of different lengths. The span of one bridge extended almost 60 meters between supports and lay on a curve.

The trailers progressed on the highway at speeds ranging from 15 to 30 km an hour, and stopped at points along the route, while the teams assembling the tracks prepared crossings ahead. Delivering the castings two at a time, the convoy made four trips in four weeks to get everything to Pamiers.

The itinerary had to be carefully plotted and the schedule kept. Traffic was diverted from the sections of highway that the convoy was using. Bridge sections were closed and traffic detoured for a day or more as tracks were laid, crossed, and dismantled. Rail traffic had to be suspended to let the convoy pass a grade crossing.

The trucks carried an identification that read "convoi exceptionnel." The description sounds fair enough.

Each trailer was the size of a barge being pulled by one huge tractor and pushed by another. The trailers were accompanied by a fleet of trucks, motorcycles, and support vehicles. There were policemen, highway officials, and a cast of engineers, technicians, drivers, and assemblers. They may not have been exactly dancing, but they were all on the bridge together.