A simplified nonlinear pushover analysis of RC walls considering longitudinal bar buckling

  • Dr Panitan Lukkunaprasit, Chulalongkorn University, Thailand
  • Dr Somboon Shaingchin, Chulalongkorn University, Thailand
  • Dr Chadchart Sittipunt, Chulalongkorn University, Thailand

In the nonlinear finite element analysis of reinforced concrete (RC) shear walls with boundary columns, the final state when the lateral resistance of the structure shows a significant drop in capacity has not been predicted with satisfaction even though sophisticated constitutive concrete models have been used in complicated cyclic analyses. This is due to neglecting buckling of longitudinal reinforcing bars in the case bar buckling occurs which leads to deterioration of confinement of the concrete core. To simulate and capture such an important mechanism, a nonlinear static pushover analysis procedure is proposed herein which features simplicity and acceptable accuracy for practical applications in design offices. The smeared fixed crack formulation is adopted for predicting the behavior of structural walls using 2-dimensional plane stress elements. A confined concrete model which accounts for the deterioration in confinement due to bar buckling is employed. An equivalent steel element based on the Dakal and Maekawa model is used to simulate buckling behavior of the reinforcing bars. Two RC walls, whose cyclic test results have been documented in the literature, are examined. The study reveals that ignoring the effect of bar buckling could lead to a significant error in the analysis, with the ductility capacity of the structure un-conservatively overestimated by almost 100%. The discrepancy is reduced to about 35% with bar buckling considered, while the lateral load capacity is predicted within 12% accuracy. The simplicity of the method proposed makes it appealing for use in practical seismic design of structures.