PERFORMANCE OF EXISTING BRIDGE COLUMNS UNDER CYCLIC LOADING - PART 1 - EXPERIMENTAL RESULTS AND OBSERVED BEHAVIOR

This study was conducted to investigate the flexural and shear perform ance of older columns for purposes of seismic assessment and retrofit design, particularly with regard to assessing the residual strengths p resent in degraded hinge regions. In this first part of a two-part pap er, experimental observations and results of tests on eight reduced-sc ale specimens that incorporated deficiencies present in older bridge c olumns are presented. The columns were fixed against rotation at both the top and bottom to enable shear transfer, even after a flexural hin ging region degrades. Test variables included column aspect ratio, lon gitudinal reinforcing ratio, lap splice length, and retrofitting detai l. Shear failures were observed both outside and within the plastic hi nge regions. In those specimens failing in flexure, plastic hinge regi ons with poor confinement and lap splices experienced rapid flexural s trength degradation. However the degraded spliced region continued to carry the shear and axial loads applied through the column.