modeling of buckled reinforcing bars including effect of lateral expansion of concrete core

Inelastic bar buckling in rc column is a complicated behavior due to the effects of slenderness ratio, concrete core expansion and constraint of concrete cover. based on the equilibrium of a plastic mechanism with distributed lateral forces acting on buckled longitudinal bar, a nonlinear cyclic average stress–strain relationship is developed to simulate the effects of concrete core expansion. the average stress reduction coefficient ω 2 is introduced in the proposed model to compensate for the effects of concrete core expansion with respect to the gomes–appleton model. ω 2 − ɛ s (where ɛ s is the average strain of buckled bar) relationships of four conventional reinforcements arrangement of rectangular rc column sections are obtained by revising the expression of the parameter for calculating equivalent lateral force of concrete core expansion. critical strain ɛ s,cr is proposed to identify the distribution of the equivalent lateral force acting on the buckled bars, where ɛ s,cr is the axial compressive average strain of reinforcing bar corresponding to the limit state of steel bar separating from concrete core. the influence of concrete core expansion can be estimated based on the value of ω 2 when ɛ s is equal to ɛ s,cr under monotonic compression. in the case study, two average stress–strain hysteresis curves of buckled longitudinal bars are calculated and compared to identify the influence of concrete core expansion on buckling behavior of bar in rc column.