|Ph.D Thesis||Department of Civil and Environmental Engineering|
|Supervisor:||Assoc. Prof. Dancygier Avraham|
This research presents a theoretical model for the behavior of partially confined axi-symmetric reinforced concrete (RC) short members subjected to an axial load. The partial confinement in RC members is usually provided by transverse reinforcement in the form of ties or spirals. As opposed to most studies of this subject, which used semi-empirical methods, the current model has been developed theoretically and it includes an analysis of the problem’s full range according to the theories of elasticity and plasticity.
The solution to the problem is developed in three stages. The first stage is the analysis of a linear-elastic axi-symmetric member under active and passive partial confinement. The results show that within a reduced cylinder radius (RCR) there is a zone of uniformly distributed stresses in which the tangential stress is equal to the radial stress and the axial and shear stresses are equal to zero. Extending the analysis into the plastic range involves difficulties that arise from the irregular geometry of the boundary between the plastic zone and the elastic zone, a boundary which is also changing as the axial load increases. Therefore, based on the RCR concept, the discrete steel ties are replaced in the second stage with an equivalent tube of thickness teq. The third stage is the elasto-plastic analysis of the equivalent concrete cylinder. The analytical stress-strain curves obtained from the current model are in good agreement with published tests results. Furthermore, based on the proposed model, equations were derived for the confined concrete strength and its corresponding strain as a function of the mechanical volumetric lateral reinforcement ratio.