Finite element analysis to determine the bending resistance mechanism of pile head connections

Pile head connections in precast spun concrete piles have two bending resistance mechanisms. One is the lever mechanism, which relies on bearing of the embedded pile against pile cap concrete. The other is the anchorage mechanism, in which anchorage reinforcement at the pile head bears moment with concrete. However, the current design guidelines of the Architectural Institute of Japan do not clearly define methods to calculate. To address this issue, finite element analyses of previously tested specimens with varying embedment depths and pile cap dimensions are performed in this study to determine the bending resistance mechanism. By adjusting the descending slope of the concrete stress–strain relationship according to embedment conditions, the analyses successfully reproduced the experimental shear force-deformation relationships and damage patterns. The results showed that the forces of the lever action concentrated near the pile cap top and the pile cap joint, and frictional forces differed between the loading and opposite sides. Furthermore, the relative contributions of lever and anchorage mechanisms to the bending capacity varied with embedment depth and pile cap dimensions. These findings provide fundamental insights for improving the evaluation of bending resistance in pile head embedment regions.