Behaviour of reinforced concrete knee beam-column joint in case of ground corner column loss-numerical analysis

Prevention of a progressive collapse event of a reinforced concrete structure is a key design consideration. Commonly a sudden column loss scenario is analyzed to ensure the structure has suitable robustness; however, there is still a lack of numerical information regarding the influence of the dynamic effects involved. Beam-column joints are a critical part in reinforced concrete frames designed for inelastic response to severe external loads. Structural response for an inverted knee beam-column joint which results from the loss of a ground corner column are performed in this study using LS-DYNA. The sudden failure of the ground corner column may turn the exterior beam-column joint into an inverted knee beam-column joint with some reinforcement requirements deficiencies. Three-dimensional finite element (FE) models of a knee beam-column joint are described and verified with experimental results available in literature; this is followed by a parametric study to investigate the influence of different types of anchorage for beam longitudinal bars. In addition to that, the effect of using additional joint vertical stirrups is examined numerically. It is shown that the various types of reinforcement anchorage in beams have significant effects on shear capacity, load-deflection characteristics and failure modes of knee beam-column joints. Anchorage beam bars with U shape produces better inelastic behaviour than 90° standard hooks and headed bars. Contribution of additional joint vertical stirrups is more influential with headed bars anchorage than with the other two anchorage types.