Experimental Study on Column Reinforcing Bar Anchorage in Drilled Shaft Footings

Abstract

This paper presents an experimental study on the anchorage behavior of column reinforcement subjected to tension in drilled shaft footings loaded under combined axial force and uniaxial bending moment. Large-scale tests were conducted on four footing specimens that were constructed with different column bar anchorage details: straight bars, hooked bars with two different hook orientations, and headed bars. All tension-loaded column reinforcement was shown to yield regardless of anchorage type. Further, all anchorage types developed stresses in the vicinity of the anchorage region except for bars with end hooks that were oriented outwards from the base of the column. Properly oriented hooked bars, considering the internal force flow of the strut-and-tie model, and headed bars developed more uniform stress distributions over their lengths as compared to straight bars. Based on developed stress distributions for the column reinforcement estimated from strain measurements, a critical section was also proposed to establish the anchorage requirement for the column reinforcement in a three-dimensional strut-and-tie model.