Substructure

The substructure of a bridge includes the piers, abutments and foundations. The design of the various elements of the substructure requires the knowledge of the distribution between piers and abutments, whether due to applied forces or due to imposed displacements by the superstructure. This chapter addresses the basic aspects for the analysis and design of piers, foundations and abutments. It discusses basic design concepts for structural bearings and seismic dampers. Bearing devices between deck and piers and abutments, may be: elastomeric bearings; elastomeric pot bearings; metal bearings or concrete hinges. The chapter also discusses bridge bearings in detail and gives specific design recommendations. Bridges may be seismically isolated or seismically protected by dampers. Protecting the structure by seismic dampers consists of increasing the damping for deck oscillations. Isolation is based on the principle of lowering the natural frequencies by reducing the stiffness of the structure.