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Title: Evaluation of Strut-and-Tie Method for Drilled Shaft Footings Subjected to Uniform Compression Loading

Author(s): Kim

Publication: Web Session

Volume: ws_S22_Kim.pdf


Appears on pages(s):



Date: 3/28/2022

Large-scale drilled shaft footing specimens with several test variables were fabricated and tested under uniform compression loading as a part of a comprehensive research project to investigate behaviors of drilled shaft footings and to refine the current Strut-and-Tie Method (STM) based on three-dimensional approach. Five design parameters—bottom mat reinforcement details, strut inclination (shear span-depth ratio), shaft diameter, side face reinforcement ratio, and footing height—were examined. The findings from large-scale footing tests subjected to axial loading contribute to understand the behavior of footings under the lower and ultimate levels of applied load and to investigate the effects of a variety of design factors on the performances of footings, which can be considered for the analysis of three-dimensional STM and the design of drilled shaft footings. Based on the comparison between the experimental results and the predictions according to current AASHTO LRFD and the up-to-date guideline, it was observed that the experimental ultimate capacities had considerable discrepancies with the predictions. The evaluation of the current three-dimensional STM presented that the grid layout of bottom mat reinforcement layout underestimated the prediction and the non-existence of side face reinforcement that caused the most brittle failure did not influence the predictions. Furthermore, the refinements of the confinement effect from massive concrete surrounding by nodal region and the nodal capacity at the strut-to-node interface, which were conservatively assumed in the current recommendations, can improve the accuracy of predictions.