Seismic Retrofit Technology Kevin I. Keady California Department of Transportation 43 Introduction Analysis Techniques for Bridge Retrofit Superstructure Retrofits Expansion Joints and Hinges • Steel Bracing and Diaphragms • Concrete Edge Beams Fadel Alameddine California Department of Transportation Substructure Retrofits Concrete Columns • Pier Walls • Steel Bents • Bearing Retrofit • Shear Key Retrofit • Cap Beam Retrofit • Abutments • Foundations Thomas E. Sardo California Department of Transportation Summary Introduction Upon completion of the seismic analysis and the vulnerability study for existing bridges, the engineer must develop a retrofit strategy to achieve the required design criteria | Keady . Alameddine F. Sardo . Seismic Retrofit Technology. Bridge Engineering Handbook. Ed. Wai-Fah Chen and Lian Duan Boca Raton CRC Press 2000 43 Seismic Retrofit Technology Kevin I. Keady California Department of Transportation Fadel Alameddine California Department of Transportation Thomas E. Sardo California Department of Transportation Introduction Analysis Techniques for Bridge Retrofit Superstructure Retrofits Expansion Joints and Hinges Steel Bracing and Diaphragms Concrete Edge Beams Substructure Retrofits Concrete Columns Pier Walls Steel Bents Bearing Retrofit Shear Key Retrofit Cap Beam Retrofit Abutments Foundations Summary Introduction Upon completion of the seismic analysis and the vulnerability study for existing bridges the engineer must develop a retrofit strategy to achieve the required design criteria. Depending on the importance of structures there are two levels of retrofit. For ordinary structures a lower level of retrofit may be implemented. The purpose of this level of retrofit is to prevent collapse. With this level of retrofit repairable damage is generally expected after a moderate earthquake. Following a major earthquake extensive damage is expected and replacement of structures may be necessary. For important structures a higher level of retrofit could be required at a considerably higher cost. The purpose of this level of retrofit is not only to prevent collapse but also to provide serviceability after a major earthquake. There are two basic retrofit philosophies for a concrete bridge. The first is to force plastic hinging into the columns and keep the superstructure elastic. This is desirable because columns can be more easily inspected retrofitted and repaired than superstructures. The second is to allow plastic hinging in the superstructure provided that ductility levels are relatively low and the vertical shear loadcarrying capacity is maintained across the hinge. This is desirable when .
