Seismic Retrofitting of Existing Structures

This chapter highlights the importance of seismically retrofitting existing structures: buildings and bridges. First, the buildings are examined and the possible retrofitting strategies are explained: structural reinforcement, adoption of dissipative bracings, and seismic isolation. In particular, for a building with a structure consisting of reinforced concrete columns and beams, it is explained how the columns can be cut, temporarily transferring the load to auxiliary structures and utilizing a diamond wire saw, and how after that the seismic isolators can be inserted and the vertical load transferred again to the columns. For bridges, various retrofitting possibilities are examined: with the insertion of shock transmission units to distribute the seismic action in several points; making the bridge continuous by connecting the beams through the slab and replacing the bearings with seismic isolators. The hydraulic jacks that can be used are described. The requirements for expansion joints are then given.