Strength capacity of steel piles filled with concrete at pile top

In the previous papers, the steel pile ultimate strength and plastic deformation capacity for local buckling is estimated with radius thickness ratio and shear span ratio. For real structures, concrete is filled into the pile top of steel piles to fix the connection between a steel pile and a reinforced concrete footing beam in. It is considered that the local buckling strength of steel piles with concrete at the pile top is larger than that of steel piles to prevent local buckling issued from filled concrete at the pile head. On the other hand, at the pile top filled with concrete, bending stress of steel pipes is not enough transmitted to a concrete member which slips on the steel pipe. Therefore, slip stoppers are attached to the steel pile top. The stress transfer mechanism between a steel pipe with slip stoppers and a concrete member has not been clarified In this paper, cyclic load tests of steel piles filled with concrete at the pile top with different axial force ratio are performed. The local buckling behavior of steel piles at pile top is elucidated and ultimate strength, deformation capacity and hysteretic energy absorption is evaluated.