WAVE FORCES ON AN INCLINED CIRCULAR CYLINDRICAL PILE

Toshiyuki Shigemura

Abstract


This paper describes experimental results on the in-line and lift forces acting on inclined circular piles which are placed in two different planes: (1) a vertical plane parallel to the direction of wave propagation; and (2) a vertical plane parallel to the wave crest. The in-line and lift force formulas for an inclined pile are formulated by referring to the conventional Morison and lift force formulas, respectively. Stokes third order wave theory is used for the estimation of flow kinematics induced around a pile. Based on these formulas, the time-independent and time-dependent values of the drag, mass and lift coefficients are determined by using several methods. Further, the time dependent coefficients are expanded into Fourier series which consist of several significant components. Reliability of these coefficient values are studied by examining the relative deviation of the predicted wave forces based on these coefficient values from the measured ones. The analysis finds that relative deviations of the in-line and lift forces exceed in many cases 15% and 100%, respectively, when the time-independent coefficients are used for the prediction of wave forces, but that they are reduced to 5% and 15%, respectively, when the time-dependent coefficients are used for it.

Keywords


wave forces; inclined cylinder; pile forces

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