A New Bridge, A New Problem

Tomorrow at 5:00 pm, Victoria’s city council will vote to pursue one of three designs for a new Johnson Street Bridge. Which criteria will weigh most heavily as councillors make the city’s biggest aesthetic decision in decades is anyone’s guess. Will they support the winner of the online survey? Will they be swayed by letters to editors? Will they use research of their own, or will they – like American Idol judges – be governed by personal taste and gut instinct?

All three designs are supposed to satisfy the same transportation requirements – three car lanes, two bicycle lanes, a pedestrian walkway, a multimodal path, and a railway track. They’re all to meet current earthquake standards, and cost around $63 million to build. But there’s one more characteristic that’s common to all three, and crucially important if the City gets time-limited federal-provincial money to build the bridge: There are no working duplicates of these designs.

Not long ago, I got an interesting email from a fellow who attended one of the City’s open houses promoting a new bridge. “I asked about something that has been bugging me about the cable-stayed option ever since the three designs were unveiled,” he wrote. “The Erasmus Bridge, which is noted as the inspiration, is of course a cable-stayed bridge, but as you might know, it does not lift ... it has a separate leaf-bascule at one end [photo above right]. So, I asked if there were any ‘cable-stayed bascule bridges’ in existence.

“I was surprised at how the answers went from something like ‘there must be at least a few’ to ‘I don’t know if there are any’ to ‘the engineers say it will work’,” he continued. “Anyway, I don't think there are any cable-stayed lift spans in existence, and if that’s true I don’t believe such a novel design could have been legitimately vetted in such a short amount of time. I would have liked to have spoken with the engineers themselves, but they weren’t present.”

Intrigued, I wrote to Sebastien Ricard, the creator of the three designs and a director of the London-based Wilkinson Eyre architecture firm, to ask for more details. Below is my Q&A with him, with links to various bridges he mentions.

Q: One of the designs is for a cable-stayed bascule bridge. It seems the Erasmus bridge in Rotterdam which provided the inspiration has the cable-stayed portion separate from the moving bascule portion. Are there any working examples in the world where the cables actually lift the span, or would this proposed bridge be something new?

A: The Erasmus bridge was highlighted through our presentation as an example of Cable Stayed bridge for people not familiar with the bridge terminology to understand what a “cable stayed bridge” is, not as inspiration as such. Regarding example of “cable supported moving bridges”, bascule system, a few examples would be:

Tyne Bridge [photo left] in Newcastle UK, by Wilkinson Eyre Architects built in 2001. - Binic Port Footbridge 1993 Architect Fauniere Lafon France Britany - La Porta d’Europa Construction 2000 in Catalonia (not a cable stayed structure as such but a bridge which is “working” in a similar structural way).

Q: Are there any working examples of the reverse bascule bridge you proposed? (Aside from the one in the Van Gogh painting, of course!)

A: The “reverse bascule” bridge system or high level counterweight bascule system is a very familiar and well know opening bridge technology. The existing Johnson Street Bridge based on Strauss Design is one example.

Other examples would be: Alcacer Do Sal Bascule Bridge - Bordigue Canal Road Bridge, Sete, France - Brother Edmund Ignatius Waterford Ireland 1982-86 - Diffenebrucke Bridge on the Rhine River 1986-87 - Forton Lake Opening Bridge UK, 2000 - Demmin Bridge Germany 1998-2000

Also regarding Rolling Bascule bridges, see below a few examples: Canary Wharf Rolling Bridge [photo right] Wilkinson Eyre Architects - Bizerte Tunisia 1978-1980 - Borensberg Bascule Bridge Sweden - Dvorcoviy Most Bridge, St Petersburg 1977-78 on the Neva River.

Q: If these designs are new, how long would it take to render them into working engineering plans?

A: Our 3 proposals are based on bridge and movable bridge principle which are not new as such (examples of these typologies of structure exist as noted above) but each of these proposals has been tailored to respond to site specific issues and to create a new landmark, a gateway to Victoria: A unique bridge design rather than a “copy” of another bridge which wouldn’t respond to the specific site constraints.

As for every bespoke [i.e. “custom-made to the buyer's specification”] design (whether these are for Bridges or other Architectural/ Structural designs) there is the need to refine the design, test it, up to detail design stage before we can prepare a set of Tender Information. The timing for this work relates to the type of procurement: as to whether or not the design team prepares all the design information or whether the design team completes a set of “detail design information” which is then given to a Contractor who will complete the remaining part of the design.

This type of procurement allows the contractor to start the construction at an early stage, without having to rely on the full information on the design being completed (this type of procurement is typically used in fast track programmes.)

The decision on the procurement methodology hasn’t yet been finalized but will be shortly in association with the City of Victoria.

To Ricard’s credit, these are not cookie-cutter designs. On September 8, when he revealed the three, he repeatedly referred to wanting to “explore” various ideas with each one. In his cable-stayed bridge, for example, the support span actually bows down as the movable span lifts. In his rolling bascule, pedestrians would actually be able to walk through the wheel [drawing below left], and watch the mechanism of the bridge as it raises.

It’s great that Victoria could have a one-of-a-kind bridge. But this does create a new problem. As Ricard said, “there is the need to refine the design, test it, up to detail design stage” to create working engineering plans and procure materials. According to the timeline presented by the City’s engineering department on May 21, work in the water on a new bridge must begin in November. That’s five weeks from now. I spoke with an American bridge engineer who’s been watching this project with interest, and he told me that the City’s schedule is “extremely aggressive”: hundreds of details will have to line up perfectly if the project is to be finished by March 2011. Getting working engineering plans will be only the first of them.

Consequently, even if the City does get federal-provincial infrastructure stimulus funding, it’s highly unlikely a new bridge will be finished by March 2011 when the stimulus money runs out. That won’t matter much to MMM, the firm overseeing the project, because they’ll get paid anyway. But it makes a huge difference to Victoria taxpayers, who will be covering all the bills after March 2011.

It will be exciting to see which design wins the City’s popularity contest tomorrow. Unfortunately, Victorians still don’t know who’s doling out the prize money – and how much of it will be coming out of their own pockets.

UPDATE (September 24, 2009): An emotional day at City Hall. Victoria was turned down for federal-provincial infrastructure money. The council went ahead and chose a new design anyway: the rolling bascule, mainly because it was unanimously endorsed by the Citizens’ Advisory Committee. The City may have a tough time selling it to the public, though. The cable-stayed actually got more votes (2572 or 49.5%) than the rolling bascule (1885 votes or 36.3%) in the online and onsite surveys.

UPDATE (March 29, 2012): Two-and-a-half years later, problems with the rolling bascule design are beginning to surface. As this story in Focus magazine reveals, engineers will have to reinforce the “open wheels” with cross-braces, thereby eliminating the ability to walk through the hinge point while the bridge is moving — the only feature of the bridge that's architecturally interesting — and have radically changed the mechanism so it bears little resemblance to the bridges at Canary Wharf.

As you'll see below, on February 12 of this year, this post also received three comments in French, advising me to “stop” and “not repeat” my concerns. The third comment goes on at length about the history of the evolution of bridge design, with the commenter’s position summed up in the second-last paragraph: “With advances in knowledge of physical sciences and materials, the bridge becomes a work of art, thanks to the engineers. The architects finally, with the technical constraints pushed to the limits, can now unleash their imaginations to create works of art.”

In Victoria, it appears those limits are reaching the breaking point.