Seismic retrofit for an existing network arch bridge with slit-type knock-off bearings

Seismic retrofit of an existing network arch bridge against large-scale (Level 2) earthquake ground motions was performed by modifying existing fixed steel bearings into slit-type knock-off bearings. Three-dimensional non-linear dynamic response analyses were carried out considering site-specific ground motions. It was confirmed that shear panel dampers as passive energy-dissipation were needed on both fixed-side and movable-side pier tops to avoid the potentially difficult retrofit work for the undersea pier anchors and foundations. The authors proposed slit-type knock-off bearings with the knock-off function as triggers against the Level 2 ground motions to provide isolation effect. Performance tests of the slit-type knock-off bearings were conducted to verify the required performance for the seismic retrofit design.