Part I of this paper introduces an experimental programme carried out on RC members with thick-walled hollow circular crosssections to study their behaviour under combined bending and shear. The study looked at ultimate resistance and propagation of characteristic crack pattern as well as the shape and behaviour of the failure sections as a function of wall thickness, amount of longitudinal and transverse reinforcement, shear span and axial force. Test results were used to verify a newly developed calculation model describing the behaviour of the members investigated at failure under combined bending and shear. This model will be presented in Part II.

No abstract

Part II analyses the applicability of current shear design models for RC members with a hollow circular cross-section on the basis of experimental results introduced in Part I of this paper. A new calculation model is proposed which assigns the contribution of the concrete zone in compression to shear resistance. The proposed model takes into account how the flexural and shear reinforcement, the load-to-support distance and the shape of the cross-section affect the shear resistance. The model is based on the analysis of potential failure sections subjected to bending and shear, and applies a compatibility criterion that considers how the member carries the load. The analogy between the failure of the concrete compression zone and the failure of the soil along a sliding surface are presented as well as the conditions for the development of the failure section.