Experimental investigations on concrete edge failure of multiple row anchorages with supplementary reinforcement

Abstract

This paper presents the details and results of the experimental investigations performed on the anchorages with multiple anchor rows of headed studs close to the edge, without and with supplementary reinforcement, loaded in shear towards the edge. The tests were performed on anchorages with 2 to 8 headed studs (one to 4 anchor rows) cast in concrete with 4 different levels of supplementary reinforcement. The test results highlight the influence of supplementary reinforcement on load carrying capacity of the anchorages. It is observed that for anchorages with multiple anchor rows, the failure crack always initiates from the back row of anchors, which is in contrast to the current assumption in EN1992-4 [1]. Due to this, more number of stirrups is activated in reality and the anchorage length of the activated stirrups is significantly more than that assumed in current model of EN1992-4. Consequently, for low amounts of supplementary reinforcement, the failure loads calculated by the current model are very conservative when compared to the experimental results. At high amounts of supplementary reinforcement, the concrete strut failure may govern the failure, which is ignored in the current models. Based on the evaluation of these test results, and supporting finite element calculations using 3D FE software MASA developed at University of Stuttgart, a realistic and rational model has been developed to predict the concrete edge failure loads for anchorages with supplementary reinforcement that is presented in accompanying paper.

Analytical model for concrete edge failure of multiple row anchorages with supplementary reinforcement

“…3). Consequently, the failure loads for this group as per the Schmid model considering the failure crack from back anchors are very similar to the experimental failure loads compared to the prediction by the EN1992-4 model (shown in [7]). Comparison of mean failure loads obtained from the tests [7] with the mean failure loads predicted by Schmid [1] for groups 2x4…”

“…When the crack is considered from front anchors, again no stirrups are considered effective and hence the failure load in reinforced concrete is the same as that in unreinforced concrete. Assuming the failure crack starts from the back anchors, the trend of the failure loads as predicted by the Schmid model is similar to that observed for the EN1992-4 model shown in the accompanying paper [7]. Although, as per Schmid model, more number of stirrups are activated on either side of the anchorage compared to the EN1992-4 model, the predicted loads are only marginally higher compared to the EN1992-4 model.…”

“…Further in these tests, the reinforcement did not yield. In order to understand the real behavior of the anchorages in reinforced concrete, the test results reported in [7] are evaluated in detail.…”

“…However, for the other two cases (reinforced concrete with d s 16 and d s 16+14 stirrups), an enhancement of the failure loads is recognized by the Schmid model. [7] with the mean failure loads predicted by Schmid [4] for groups 2x2…”

“…Clearly, the predicted failure loads are always very conservative compared to experimental failure loads. [7] with the mean failure loads predicted by Schmid [4] for groups 4x2…”