January 25, 2010

RICHARD GILBERT

Ten girders will be placed side by side on flat ground on rollers, then pushed forward horizontally, with a series of jacks, toward each pier.

FOCUS | Fort McMurray

Alberta’s biggest bridge will feature innovative design

RICHARD GILBERT

staff writer

The largest bridge deck in Alberta is being built in Fort McMurray, using an innovative design and unique approach to address population growth and the massive trucks carrying heavy loads to oilsands construction projects.

“The Athabasca is the largest bridge construction project in Alberta and it is innovative for several reasons,” said Naginder Jabbal, CH2M Hill road operations leader. “The transportation and mining equipment that will cross that bridge are larger than any being used elsewhere.”

For engineers, the size of the bridge is determined by measuring the force and weight that can be safely carried by the structure. A typical bridge in Alberta is designed to support a total load of 800 tons.

Jabbal said this bridge is designed for a substantial 28 axle (10,000 ton) overload truck used to transport bulky equipment to the oilsands.

It can carry up to a 6.4-metre wide, 1.1 million-kilogram overload vehicle, which is 12.5 times more than typical designs.

CH2M Hill bridge designer Malika Ali said the force and weight of the overload truck is so enormous, that no other traffic will be allowed on the five-lane bridge when the vehicle is crossing.

“There is a defined position (truck lane) of these overload vehicles on the bridge deck,” said Ali. “We have very heavy utilities going under the walkway, so we put truck traffic on the other side of the bridge.”

Another innovative feature of the bridge is the technique used to place the girders on top of the piers in the Athabasca River.

Ali said CH2M Hill is using a technique for girder launching that will result in significant savings to the owner, the Alberta Ministry of Transportation.

“If we used a crane to raise the girders, we would have to enter the river three times, which would have involved significant time and cost,” said Ali. “The girders are very heavy and the river is fairly shallow at this location to use a barge. Thus, the most suitable option is to launch the girders.”

She said for the launching, ten girders will be placed side by side on flat ground on rollers, and then pushed forward horizontally toward each pier with a series of jacks.

RICHARD GILBERT

A crew is busy working on the abutment for the Franklin Street off ramp.

The piers are designed for major ice load conditions and for being constructed one year prior to girder erection.

The east end span, which is the smallest section of the bridge, will be built using a crane. This section will be flared and super-elevated on a spiral curve.

“Generally, bridge structures are straight, but this one has a curve to enhance visibility and safety,” explained Jabbal.

General contractor Flatiron was awarded the contract for the construction of the $127-million bridge, in January 2008. Construction began that June.

“These projects are essential for the community because we are so far behind with transportation infrastructure,” said Wayne Prins, Christian Labour Association of Canada representative for Fort McMurray. “They were planned before the economic crash and originally weren’t part of any stimulus package.”

When this project started, Fort McMurray was experiencing an oil boom, which placed serious constraints on the construction of the new bridge.

“The price of food and diesel fuel were pretty outrageous,” said Ken Tanner, project manager with Flatiron.

“When we called a subcontractor to come to the site or ordered a piece of material, we had to make sure we had long lead times. Nobody could deliver materials for the bridge or certain parts when equipment broke down.”

Tanner said it was necessary to call subcontractors months ahead of time when scheduling certain construction activities.

“Construction is a really dynamic industry, so when stuff happens it gets really busy and it can be hard to react,” he explained.

In 2008, at the peak of construction, Flatiron employed 150 hourly paid workers on the project.

With the start of the recession in late 2008, construction management on the project became a bit easier.

“From what we saw locally, the economy was booming until September or October of last year,” said Tanner.

“As the weather started to turn construction naturally subsided and this coincided with the slowdown.

This summer the people who provide services to the project were more responsive and there was better availability of goods and materials.”

The new five-lane, seven span steel “I” Girder Bridge bridge will be 33 metres wide and 472 metres long.

It was also have a deck area of 15,576 square metres, which makes it the largest bridge deck in the province of Alberta. Completion of the bridge is scheduled for late 2010.

Visit our special section to read more from the three-part series on Fort McMurray

Print | Email | Comment