Conceptual design of two vehicular cable-stayed bridges over the Magdalena River, between Flandes and Girardot (Colombia), from KP8+801 to KP9+180 KP 17+760 (Right Bridge, west side) and from KP8+812.67 to KP9+211.67 (Left Bridge, east side). The bridges will have overall lengths of 1246 ft (380,2 m) (right bridge) and 1312 ft (400,2 m) (left bridge), with a main span of 557 ft (170 m) and two back spans of 226 ft (69 m) and 278 ft (85 m).
Both bridges have three intermediate supports and spans of 226-557-278-180 ft (69-170-85-55 m) (right bridge) and 226-557-278-180 ft (69-170-85-75 m) (left bridge).
Each bridge consists of a continuous post-tensioned concrete box girder with a depth of 19 ft (6.0 m) at the beginning of the cantilevers, above piers 1 and 2, varying up to 11 ft (3.50 m), in a parabolic shape, at a distance of 102 ft (31.35 m), and a constant depth of 11 ft (3.50 m) for the remaining length of the box girder.
The concrete deck is designed with a central plane of cables in each of the piers 1 and 2, Half-Fan shape, each anchored to a pylon 69 ft (21.25 m) high. For both bridges, the presence of one internal and one external post-tensioned force during construction (isostatic phase) has been considered. In the hyperstatic phase, an internal post-tensioned force has been considered to provide structural continuity.
The deck’s width of 54 ft (16.60 m) in total includes two passing lanes of 20 ft (6.10 m) with shoulders on each side of 11’’ (0.30 m), New Jersey type barrier of 13’’ (0.35 m) in width at each end of the passing lanes and a sidewalk of 5 ft (1.55 m) in width on both sides of the bridge. The span between bent 3 and abutment 2 is designed with a longitudinally post-tensioned concrete box girder and is projected to be built on formwork, in a single phase, first with a tensioning of 60% of the total force of the cables, allowing the withdrawal of the false work, followed by a second tensioning with 100% of the design force.