New span for Johnson Street Bridge loses unique feature
Mar 29 2012
A vision of the Johnson Street Bridge during a lift. The walkway will now be attached to the bracing on the wheels.Photograph by: Supplied photo, City of Victoria , timescolonist.com (March 2012)
The coolest feature of the new Johnson Street Bridge - the ability to walk through and stand inside the lift wheels while the bridge was being raised - has been dropped as the project moves ahead amid rising costs.
City engineering staff say the feature had to be dropped to compensate for structural weakness in the original design.
The Johnson Street Bridge replacement was billed during the 2010 referendum campaign as the first bridge in the world where people could walk through the rolling mechanism while the bridge was being raised.
But architects have determined additional bracing is necessary to achieve the stiffness the 200-tonne mechanical wheels need to carry the bridge load. Once into detailed design, it was decided the best way to achieve that was to attach the walkway to the bracing on the wheels, said city director of engineering Dwayne Kalynchuk.
"The option that was available was to put stiffeners on the bottom part of the wheel, and now the walkway becomes fixed to those stiffeners," Kalynchuk said. "And then consequently, when the bridge opens up, the walkway itself will move."
The result is the walkway will be closed about three or four per cent of the time, he said.
Project manager Mike Lai told councillors the change did not amount to "a material change in design," but rather "a design refinement."
Both Kalynchuk and Mayor Dean Fortin said the change actually came to light some months ago. Fortin stressed that people would still be able to walk under the bridge through its circle mechanism - just not when the bridge is moving.
But the walk will be a short one. As the city doesn't have a right of way on the north side of the new bridge for the walkway, it will deadhead just past the bridge - forming more of a viewing platform than a pathway.
Fortin said the walkway ultimately would be extended in conjunction with development in the area.
Coun. Geoff Young said the fact that "pretty substantial" design changes are still being made is worrisome. "It makes it difficult for me to be sure that we really have a good handle on the costs," he said.
He also wonders whether the walkway will ever be built. Not only is the walkway closed when the bridge goes up - possibly requiring a second walkway for people who want to access the northern part of the Harbour Pathway - the modification also raises safety concerns.
"You also would need to have barriers to prevent people from walking on [the walkway] when the bridge goes up," Young said. "You would also have to have a mechanism of making sure no one was on it when the bridge started to go up. My forecast is, indeed, it will never be built."
Fortin said there are bound to be future design modifications.
"I think both council and the public have to be aware that there's going to be some minor design changes. [There will be] no material design changes of design or scope. Those have to come before council for approval."
Last week, Victoria councillors reluctantly approved a $15.8-million increase for the Johnson Street Bridge project, bringing the total cost of replacement to $92.8 million.