Spanning the Penobscot

Construction of a new cable stayed bridge over the Penobscot River in Maine, US is being carried out in a bid to relieve congestion and remove weight limits on the existing suspension bridge.

Work on the new 353 m span bridge, which will replace the narrow Waldo-Hancock Bridge, started in late 2003 and is scheduled to be finished in May next year. The construction is being undertaken by a joint venture of Cainbro Corporation and Reed & Reed for the Maine Department of Transportation.

Construction of the two 128 m high tapered concrete pylons is nearing completion and has been carried out using a formwork system supplied by Doka USA.

Below the deck level, each pylon's two 37.8 m C shaped legs have been cast using 500 m² of Doka Top 50 timber beam formwork and Doka's MF240 crane lifted climbing system. Each leg was formed in eight pours with each pour progressing the height of the leg by up to 4.7 m on a weekly cycle.

Above the deck the pylon's profile becomes rectangular and tapers from 10.7 to 9.1 m wide. The final 90 m sections were formed using the same system but the Top 50 was combined with truss support to save the joint venture installing 320 wet ties on each of the 18 lifts.

To save time on the contract the cable stays are being installed before construction on the upper pylons is completed. But to reduce the impact on other site operations, the joint venture is using Doka's SKE 50 self climbing system with telescopic platforms to carry out the work. This reduced the crane time needed by the operation and allowed the contractors to work around previously installed stay cables more easily.