Technology for a long cable-stayed bridge
The new Sidney Lanier cable-stayed bridge in Brunswick, Georgia, USA, was built to replace the old lift-span structure completed in 1956. The old lift-span system with a restrictive vertical navigation clearance of 42.4 m meant that roadway traffic on the bridge had to come to a halt as ships passed through. With an average of 20 ships passing per day, the bridge was closed to traffic for a significant part of each day.
The new bridge with an increased vertical navigation clearance by 14 m not only eliminates the traffic snarls on the old lift-span bridge but also provides an economic boom to the area by stimulating rapid growth to the port facilities. A 90 m section of the old bridge was left in place to serve as fishing pier.
The new cast-in-place concrete bridge provides increased shipping access to the port of Brunswick through a 381 m main span with side spans of 190,5 m. The four-lane superstructure has an overall width of 24.25 m.
The main span is supported by 176 stay cables with 19, 27, 37, 48 and 61-0.6" strands with DYNA Bond® Sockets, anchored into 148 m high twin pylons. The pylons are joined in two places by crossties: one below the cables, the other below the roadway. The towers are hollow and an elevator goes up to the upper crosstie. Ladders take inspectors above the crosstie for access to the anchorages for the cable stays. The deck is continuous from one anchor pier to the other and is held in place by it. The anchor pier must be strong enough to support the deck, but also flexible enough to accommodate the large deflections that arise as the length of the deck changes due to temperature shifts.
The typical approach spans to the cable-stayed bridge are 54,8 m long. These spans are composed of precast concrete post-tensioned girders with conventional cast-in-place decks.