The efficiency of confinement reinforcement in post-tensioning anchorage zones

Abstract

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.

Effect of the type of posttensioning anchorage on the behavior of anchorage zones

“…Besides the effect of the type of anchorage, and as observed by Marchão et al 10 and by Rebelo et al, 11 one of the causes of the observed differences could be related to the fact that in the case where there are, simultaneously, two types of confinement reinforcement, the outer reinforcement is not as effective as the inner one. Therefore, when calculating the bearing strength, the arithmetic superimposition of both spiral and stirrups in confinement can be against safety leading to higher loads.…”

“…Therefore, when calculating the bearing strength, the arithmetic superimposition of both spiral and stirrups in confinement can be against safety leading to higher loads. Also, according to the same authors, 10,11 the different confinement reinforcement levels have different strains along the height of the confined zone and just some of the reinforcing bars attained yielding, contributing to the existence of non-uniform confinement forces along the height, and consequently smaller than the ones considered in the proposed equations.…”

“…The design of the local anchorage zone is strongly influenced by the characteristics of the anchorage device and simple design models are only suitable for plain steel plates and simple bearing plate anchorages. 10,11 Despite the lack of knowledge and research in this field, most of the few recent research works published that are focusing on the bearing strength of confined concrete use steel bearing plates instead of special anchorage devices that are widely used in posttensioned structures. The implications of extrapolate the results obtained from studies using steel bearing plates instead of special anchorage devices should be addressed.…”

Analysis of Bearing Strength of Post-Tensioning Anchorage Zone with Respect to Relative Bearing Area and Lateral Confinement Design

“…Because Equations ( 8) and ( 17) were verified for the minimum anchorage spacing [15,16], κ is 1.0 for the minimum anchorage spacing. Next, a revised equation for the spiral-dependent contribution of lateral confinement to the bearing strength was presented as Equation (21). The exponent of Equation ( 20) was determined to create κ in Equation ( 21), which is identical to the average increase (1.12 = 1.144+1.093 2 ) from A core for the minimum anchorage spacing.…”

“…Mao et al [17] and Lee and Kim [18] focused on stress distribution, crack formation, and ultimate capacity with respect to the bursting force in the anchorage zone. Bonetti et al [19], Marchão et al [20], Rebelo et al [21] performed on the influence of confining reinforcement on the bearing strength of concrete blocks. Their research took similar approaches as other research, such as the investigation of the existing and proposed design equations for better estimation.…”