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induced ground displacement was the cause of damage (Shea 1991). Lateral displacement of
floodplain deposits destroyed approach embankments, pushed abutments and piers riverward,
and sheared connections in the substructure of the bridges.
The Rio Viscaya Bridge, a three-span pre-stressed concrete bridge founded in loose sands,
collapsed due to loss of soil support and ground deformations resulting from liquefaction. The
bridge lost two spans due to severe abutment rotation, resulting in pile distress (Figure 2.25) and
the collapse of one interior support. A second interior support settled vertically about 1 m.
Geotechnical boring logs near the north abutment showed that the entire length of piles were
supported in sands and silty sands. Liquefaction of soils in approach fills caused lateral spreading
and bearing capacity failure. The north roadway approach fill settled approximately 1.2 m. Both
north and south abutments rotated as a result of movement of liquefied soils.
Figure 2.25: Rio Vizcaya Bridge, Pile Failures (North Abutment)
The Rio Banano Bridge provides an additional example of severe damage due to liquefaction. It
was a single lane bridge consisting of three 22 m spans of twin prestressed concrete I-beams,
located at a river crossing. The soil movement caused about a 9 rotation of the south abutment
resulting in a movement of the pile tops toward the river of roughly 0.7 m. All piles were 36 cm
square precast concrete piles. The front piles, driven at a batter of 1H:5V, suffered flexural as
well as shear failures (Figure 2.26). Vertical piles at the rear portion of abutment pile caps
showed less damage. As observed at other bridges, the approach fills slumped substantially and
restricted access until the grade could be restored.
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