Improved Transmission of High-Strength Concrete Column Loads through Normal Strength Concrete Slabs

Twelve column specimens were tested in compression; six were slab-column specimens and six were isolated column specimens. The slab-column specimens were first tested to punching shear failure before the columns of the specimens were loaded axially. The effects of confinement from the surrounding slab on the axial capacity of the columns were investigated. Other parameters investigated were the placement of fiber-reinforced concrete in the slab and the concentration of flexural reinforcement in the column vicinity. The effects of these parameters on the ability to transmit axial loads from the high-strength concrete columns through the normal strength concrete slab were examined. Currently there is no beneficial effect in the ACI Code1 or the CSA Standard A23.32 for using fiber-reinforced concrete or closely spaced slab reinforcement near the column in the calculation for the transmission of column loads through slab-column connections. The beneficial effects of concentrating the slab reinforcement near the column and of using fiber-reinforced concrete are demonstrated.