Improved transmission of high-strength concrete column loads through normal strength concrete slabs

Twelve column specimens were tested in compression; six were slab-column sp ecimens ans six were isolated column specimens. The slab-column specimens w ere first tested to punching shear failure before the columns of the specim ens were loaded axially. The effects of confinement from the surrounding sl ab on the axial capacity of the columns were investigated. Other parameters investigated were the placement of fiber-reinforced concrete in the slab a nd 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 w ere examined. Currently there is no beneficial effect in the ACI Code(1) or the CSA Standard A23.3(2) for using fiber-reinforced concrete or closely s paced slab reinforcement near the column in the calculation for the transmi ssion of column loads through slab-column connections. The beneficial effec ts of concentrating the reinforcement near the column and of using fiber-re inforced concrete are demonstrated.