Structural behavior of self-compacting concrete filledtubes

Among the great variety of applications of self-compacting concrete (SCC), steel-concrete composite columns begin to be extensively used in modern construction engineering, in particular Concrete Filled Tubes (CFT). Three different concrete mixes are considered for possible use in CFT, each of them designed for a 28 days cylindrical compressive strength of 50 MPa: (i) a Normal Vibrated Concrete (NVC), (ii) a Self-Compacting Concrete (SCC), (iii) an expansive self-compacting concrete (SCC-E). Concrete Filled Tubes with critical length ranging from 131 cm to 467 cm have been experimental and analytically investigated in eccentric compression. The steel tubes presented a cross section of 139.6mm external diameter and 4.0 mm thickness and the load was applied directly to the concrete infill with a nominal fixed eccentricity equal to 25mm. The experimental and analytical results show that the behavior of eccentrically loaded columns is governed by bending moment-axial load interaction. As a consequence perfect bond at the interface can be assumed and the axial capacity of the column is only function of its geometry and of the mechanical properties of the materials. The axial capacity is finally predicted by adopting Eurocode 4 [1] approach.