At the pile head part of a steel pipe pile, commonly a structure called slip prevention stoppers are attached to the inner surface of steel pipe pile in multiple steps, and filled with concrete in the pile body. However, there are no reports on experimentally verifying the structural performance of this structure. In this paper, we have confirmed the integration of steel pipe pile and filled concrete, ultimate bending strength and deformation capacity. We propose a method to calculate the ultimate bending strength and deformation capacity at the pile head part of steel pipe pile and show its validity.
