Influence of defects on the lateral dynamic characteristics of offshore piles considering hydrodynamic pressure

This paper develops an analytical framework to reflect the associative effect of dynamic soil-pile interaction (DSPI) and dynamic water-pile interaction (DWPI) on the lateral dynamic characteristics of offshore concrete piles. The pile is assumed to be an Euler-Bernoul20beam and the soil is described by the Biot's poroelastic theory. The hydrodynamic pressure applying on the pile shaft is calculated based on the radiation wave theory with the consideration of water compressibility. The influence of defects along with the hydrodynamic pressure on the lateral dynamic impedance and natural frequency of offshore piles is thoroughly investigated with the proposed solution. The results show that the hydrodynamic pressure cannot be ignored when analyzing the lateral dynamic characteristics, especially for those offshore piles with deep water depth subjected to high frequency vibration. The damage caused by necking defects is much larger than that of bulging defects, and even a small necking defect can lead to a significant decrease of dynamic stiffness and natural frequency of piles. The lateral dynamic characteristics of piles are more sensitive to the variation of defect radius rather than the defect length.