PUSHOVER ANALYSIS OF RC COLUMNS SUBJECTED TO MULTIPLE DEGREES OF TRANSVERSE REINFORCEMENT CORROSION

The seismic performance of old existing bridges remain a major issue of the road network managers, especially in moderate seismic regions were 70's bridges were designed prior to modern seismic codes and without earthquake actions considerations, or subjected to great damage and confinement loss due to reinforcement corrosion. A fiber-type section model was employed in order to perform a pushover analysis of columns under multiple degree of confinement losses. The Mander model allow the estimation of the compressive strength and ultimate strain values as a function of the confinement (transverse reinforcing) steel. The model is able to quantify the effects of losing confinement on seismic performance, especially axial-flexural cross section ductility. A case study conducted on an old exiting multicolumn bridge with apparent confinement loss has showed that transverse reinforcement provides plastic rotational capacity to maintain flexural strength as high curvatures. Different levels of transverse reinforcement losses, from 25% to 100%, in addition to uncorroded case, were considered on a pushover analysis in order to draw performance curves and evaluate ductility reserve. Results have shown that confinement loss induced by corrosion of transverse reinforcement reduce considerably the ductility of the columns, and special attention must then be given in order to verify the residual plastic hinge capacity