Transmission of column loads through lower strength concrete floors: Experimental and analytical study

This research covers both experimental and analytical investigation of the effective compressive strength (f'ce) and behaviour of the joints between high-strength concrete columns and normal strength concrete floors under a combination of axial compressive loads from the columns and gravity loads from the floors. f'ce is notionally the cylinder strength of some virtual concrete that combines the effect of the joint concrete(s) and the effect of the confinement provided to the joint.; The experimental stage included fabrication, instrumentation, and testing of seven 2/3 scale specimens. The main variables in this research program are adding high-strength-concrete inside the joint, debonding of the floor main reinforcement through the joint, and the loading regime. The analytical stage covers the previously mentioned factors and other factors related to properties and arrangement of the materials composing the joint.; The main findings of the experimental stage are: (1) casting the joint with the top column can restore the full strength of the column, (2) partial debonding of the floor main reinforcement can improve the joint effective strength, (3) the vertical and lateral strains at maximum concrete stress are sufficient to develop high strength steel reinforcement to increase capacity of the joint if the joint is made of normal strength concrete, (4) the combination of ultimate load on the floor and service load on the column causes a reduction in the cross-sectional area of the joint without failing the joint.; The main contribution of analyzing the test results of this research is to crystallize the awareness of the joint behaviour under different loading regimes. That was achieved through deriving concrete confinement model to predict the strength and behaviour of any column-floor joint under any condition. The models were validated by comparison to the experimental results found in the literature.; A parametric study was conducted to investigate the sensitivity of the effective strength and behaviour of the joint to any change in the different variables.