The influence of longitudinal reinforcement buckling in structural response

Longitudinal rebar buckling has meaningful effects on reinforced concrete structures behaviour: strength and ductility reduction can cause premature failure of both a structural element and the whole structure. Buckling significantly affects the overall response of structures designed for vertical loads or with older seismic codes, these usually have high stirrup spacing and low concrete core confinement. The Authors studied the phenomenon and two independent original models have been proposed in the past: a steel stress-strain relationship and a concrete compressive failure criterion with transversal to longitudinal reinforcement interaction. The evaluation of buckling influence on structural element response is the topic of the present paper; old quality type material characteristics are considered too. Two main arguments are pointed out: an evaluation of buckling influence on moment-curvature behaviour (for different cross section geometry, reinforcement ratios and axial loads) and a modelling of influence of section ductility decay on global displacement ductility of cantilever columns.