Prediction of pullout resistance of single footings and group footings

This study investigates experimentally and theoretically the pullout behavior of shallow footings embedded in soils, which is highly relevant for constructing transmission towers to achieve a rational and economical design. Most previous research in this field is restricted to a single footing. This study considers both single and group footings and proposes a modification to the theoretical methods available in the literature for predicting the ultimate uplift resistance of single footings that makes them applicable for group footings. A series of laboratory tests were compared with theoretical methods available in the literature to predict the ultimate pullout resistance of single footing, and the theoretical method that gave values most consistent with experimental results was determined. This method was found to be the earth cone method. A modification to this method based on the experimental results of single footings was proposed, named "modified earth cone method." The validity of this modification was confirmed by performing finite element analysis using Plaxis 3D program for a full-scale footing simulation. The earth cone method was additionally modified based on experimental results of group footings to be applicable for groups of footings.