The efficiency of confinement reinforcement in post-tensioning anchorage zones

In this paper, a parametric study based on the load transfer test specified in ETAG 013 was performed with the aim of investigating the efficiency of the confining reinforcement in the local anchorage zone of post-tensioning tendons, in particular when there are two types of confining reinforcement, spiral and stirrups. The parametric study was conducted using the finite element software ATENA 3D and included 45 specimens of ordinary concrete reinforced with a combination of spirals and stirrups. The models were calibrated using the experimental results obtained in tests of similar specimens. The influence of concrete strength, cross-section dimensions, reinforcement ratio and type of anchorage device were investigated. The reinforcement strains were monitored to assess the relation between the strains of the inner and outer levels of reinforcement and the uniformity of the confinement forces along the confined length. A comparison between the bearing strength obtained by the numerical simulation and that obtained by models found in the literature is also presented. From the analysis of the strain values, it can be concluded that the spiral reinforcement is more effective. However, the results show that stirrups make an important contribution to the control of concrete cracking.