Abstract
An unconventional retrofitting measure is proposed for existing bridges, which has the ability to reduce the seismic actions. This is mainly achieved by an external restraining system consisting of IPE-steel piles driven in the existing backfill soil and a restraining slab. The slab interacts with the deck slab of the existing multi-span simply supported (MSSS) bridge system and transmits part of its seismic actions to the piles and therefore to the backfill soil, which has the ability to dissipate part of the induced seismic energy. The proposed unconventional restraining system was implemented and analytically assessed in an existing MSSS bridge system. The study showed that the unconventional restraining system has the ability to reduce effectively the actions and to enhance the earthquake resistance of the existing bridge.