Structural Design and Liquefaction Analysis
The viaduct over the Magdalena River, which is located in Colombia, has a total length of 1360 meters. Its range encompasses the distance between the PK 6 + 764 and 8 + 124 of the road, crossing the Magdalena River, from which it takes its name. It is divided into three different sections in terms of structural typology. The central section is 400m in length and was executed by cantilevering. The two other sections of 720 and 240 m, respectively, was constructed using isostatic spans of prefabricated beams.
The board of the viaduct has a total width of 12.95 m, with two lanes of circulation of 3.65 m each. Berths of 1.80 m and a pedestrian sidewalk of 1.00 m are separated from the traffic by means of a barrier of 0.35 m. The central section is completed with barriers on both sides of 0.35 m width.
The two sections on each end are formed by isostatic spans of 40 m of light. The initial section runs between PK 6 + 764 and 7 + 484, divided into 18 spans, while the final stretch goes from PK 7 + 884 to 8 + 124, consisting of 6 spans.
The cross section consists of 4 post-tensioned AASHTO VI concrete beams spaced 3.45m apart, and an upper cast-in-place concrete slab over pre-stressed prefabricated slabs. Three transverse diaphragms are arranged, joining the beams, one in each support and the third one in the mid-span. The total height of the cross section is 2.05 m (1.83m the height of the beam and 0.22m the thickness of the slab).
Optimization of the foundation system of the bridge
The mission of Dynamis Associates was to optimize the foundation system on the main piles of the bridge. For this purpose, soil-structure interaction calculations were carried out, reducing the number of piles to almost half (16 instead of 30).
Due to the seismic hazard analysis performed by DYNAMIS, a more efficient foundation system was designed. This solution is compatible with the seismic level of the area and with the existing licuefaction risk.