How to move an entire bridge from place?
Image Source: Playback / Popsci
When the Sellwood Bridge, located in the city of Portland, USA, was built in 1925, it was not designed to support 30, 000 vehicles a day. And that was evident in the 1980s, when cracks began to form in the bridge supports.
The situation was so critical that federal inspectors rated the bridge with a score of 2 on a safety scale from 0 to 100. As a result, heavy trucks, buses and fire trucks were forbidden to transit the site.
After years, local county engineers (a state subdivision that spans multiple cities) decided it was time for a new bridge. The cheapest option (which cost $ 306, 000) would be to move the existing structure to serve as a diversion until the new one was built in place. But how do you move a 1, 100-meter, 3, 400-ton bridge all at once?
The gigantic operation took place over 14 hours on January 19 this year. Between the current and the new site, engineers built rails covered with Teflon pads, soaked with liquid soap to make them slippery.
Then 40 150-ton hydraulic jacks lifted the bridge and placed it on steel beams that could slide into the tracks. Finally, a second hydraulic assembly pushed the bridge inch by inch to its new location. The new bridge is expected to open in 2015.