Abstract

The 2750m-long Chacao Bridge will connect mainland Chile with island Chiloe. The three-tower

suspension bridge will have two main spans over 1km length. Due to exceptionally high seismic

forces, the foundations of this megastructure have been a challenge to design.

Central and North Pylons are founded in Chacao channel respectively by four and two groups of

nine piles. The piles are made of a reinforced concrete part surrounded by a structural steel casing.

The steel casing is embedded into the seabed level by 10m at least and into the pilecap by more

than one pile diameter. The casing embedment length ensures the transfer of the steel casing

internal forces into the pilecap. This transfer is made by three coexisting mechanisms: a direct

transfer at casing top level through the continuity of the reinforced concrete, through a

pressure/contra-pressure mechanism and through shear connectors welded on the steel casing.

Keywords: suspension bridge, foundation, pile, pilecap, structural steel casing