Scientific paper ID 1552 : 2018/1

Circular cross-section is common in reinforced concrete elements such as building columns, bridge supports and cast-in-place piles. Most often with such elements the longitudinal reinforcement is evenly distributed along the periphery of the cross-section. When the elements are subjected predominantly to bending, compression zone of concrete is a circular segment. In case of a complex shape of the compression zone according to EN 1992-1-1, it is acceptable to adopt a rectangular stress distribution with reduced effective height of the compression zone and with reduced effective strength.

Part of the longitudinal reinforcement falls within the compression zone and works under compression together with the concrete, another part works on a tensile. Besides the deformations in the reinforcement, which is located near the neutral axis are elastic and the stress level is low, in reinforcement, which is away from the neutral axis can develop plastic deformation and the stress reach the yield strength.

The purposes of this publication are:

 to determine the values of longitudinal force and bending moment in concrete and reinforcement аs a function of the ratio of neutral axis depth to effective depth of the cross-section and of the ratio of the diameter at which the longitudinal bars are located to the diameter of the circular cross-section,

 to determine the characteristics of the zones where the deformations in the reinforcement are plastic.

Uncertainties related to the cross-section of cast-in-place piles and concreting procedures shall be allowed for in design, аdditional ments for longitudinal reinforcement and the partial factor for concrete must also be respected.