Modeling bar slip and pullout capacity of straight anchorages

This paper presents an analytical method to predict the bar slip and pullout capacity of straight bars embedded in well-confined concrete, such as column bars extended into a footing or cap beam. Closed-form solutions of the slip at the loaded end of the anchorage length and the pullout strength of the anchorage are derived based on a set of a priori bond stress distributions for elastic and plastic loading situations. The model assumes a linear distribution of bond stresses along the elastic portion of the anchorage length, and a constant bond resistance within the region where the bar has yielded in tension. For relatively short embedment lengths, the slip at the unloaded end is also considered. The accuracy of the model in predicting the loaded-end slip, the strains along the embedment length, and the bar pullout capacity has been verified with experimental data. The model provides an accurate representation of the global response of straight anchorages up to the ultimate tensile strength or the pullout failure of the bar. It also results in a sufficiently accurate representation of the strain distributions obtained experimentally in pullout tests on bars with different embedment lengths.