Experimental Study on Drilled Shaft Reinforcing Bar Anchorage in Footings

Abstract

This paper presents an experimental study on the anchorage behavior of drilled shaft reinforcement subjected to tension in drilled shaft footings loaded under combined axial force and uniaxial bending moment. Four large-scale tests were conducted on drilled shaft footing specimens employing an equivalent loading condition introducing tension in the drilled shaft reinforcement. Three different anchorage details were tested: straight bars, hooked bars, and headed bars. The drilled shaft reinforcement was capable of developing its full yield strength in tension in all the tests, regardless of the anchorage detail. The tensile stresses in drilled shaft bars were primarily developed in the region of the embedment length closest to the interface between the drilled shaft and the footing, while negligible stress and slip were measured in the vicinity of the unloaded end of the bars for all three anchorage details. Finally, a critical section is also proposed in this study to perform the anchorage check for the drilled shaft reinforcement in drilled shaft footings designed with the strut-and-tie method. The definition of the critical section provides a safe estimate of the available development length of the drilled shaft bars according to the findings of the experimental program. © 2023 American Concrete Institute. All rights reserved.