PUSHOUT STRENGTH OF CONCRETE-FILLED STEEL HOLLOW SECTION TUBES

Abstract

Pushout tests have been carried out on 40 short, concrete-filled steel hollow section tubes. Rectangular, square and circular sections were used in this experimental programme. Sixteen of the specimens were 450mm long, and the steel-concrete interfaces about 400mm long. These specimens were tested with and without the use of grade 4.6 black bolts as mechanical shear connectors. The rest of the tested specimens were of variable lengths, and their steel-concrete interface was approximately 200, 400, or 600mm long. The interface of half the latter specimens was covered with oil prior to the casting of the concrete core. The same concrete mix was used throughout the experimental programme. During testing, the load was applied at the top of the specimen on the concrete core and was resisted by resting the steel section on its base. The tests showed clearly that the resistance of the specimens to the pushout load is a function of the shape and size of the steel hollow section used, and also the condition of the steel-concrete interface. More tests have already been carried out on other specimens with different types of shear connector, and the results should lead to a better understanding of the load transfer mechanism in beam-column connections in composite construction. (A)