Influence of Headed Anchor Group Layout on Concrete Failure in Tension

In calculation of steel and concrete foundation joints, design of anchors in concrete is significantly important. Currently, design of anchors in concrete is based on the Technical Specification CEN/TS 1992-4: Design of fastenings for use in concrete which has already a status of a pre-standard. This theoretical study is focused on modification factors which influence characteristic resistance of headed steel anchor group embedded in concrete and subjected to axial tension only. The effect of overlapping of the concrete failure cones of individual anchors within the group on characteristic resistance modification factors was considered. The aim of the paper is to show influence of particular modification factors considered in case of the narrow RC-members and in case of disturbance of the distribution of stresses in concrete due to boundary edges. These two effects usually influence resistance in tension of anchors embedded in the columns (edge breakout). Also, the additional strength due to presence of so called "anchor reinforcement" extended into the area of the concrete breakout cone is mentioned.