Transmission of Interior Concrete Column Loads through Floors

Clause 10.15.3 of the 1995 ACI code (ACI 318-95) defines the effective strength of a high-strength concrete interior column with an intervening normal strength concrete slab. This provision is based on laboratory tests in which no load was applied to the slab. Such tests may overestimate the strength of the column because they do not properly model the confinement conditions of the column-slab joint. This paper reports experimental results of tests with properly modeled confinement conditions. The test results show that the intensity of slab load, the aspect ratio of the joint, and the rectangularity of the column affect the strength of an interior column-slab joint. A new design equation replacing the provision in Clause 10.15.3 is proposed.