Dynamic Response of Short Piles under Lateral Transient Load-Paper

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The paper develops an analytical method for predicting the transient lateral response of short piles, motivated by jetty piles exposed to ship-berthing impacts. Unlike commonly used approaches for long piles under harmonic loading, the method addresses short piles, where soil failure may precede structural failure and pile-tip boundary conditions cannot be ignored.<br /><br />The pile is modeled as a partially embedded beam-column supported by soil springs. Assuming the soil’s shear modulus is constant with depth, the authors derive pile deformation shapes and combine bending and shear stiffness to obtain an effective lateral stiffness. They also formulate equivalent mass and damping terms, then use a single-degree-of-freedom vibration model to calculate the time-dependent response to an initial velocity at the pile head. The resulting displacement history can be used to estimate bending moments and shear forces along the pile. The analytical equations can be implemented in general-purpose software such as MATLAB or a spreadsheet.<br /><br />The method is illustrated using a raw-water jetty in West Bengal. Under an assumed berthing-induced pile-head velocity of 2.5 m/s, the calculated maximum displacement is about 410 mm. The analysis indicates that, unlike in long piles, impact effects are distributed along much of the short pile. Despite the large displacement, calculated bending moments and shear forces are relatively low, attributed to the pile’s long unsupported section and resulting flexibility. The authors therefore note that buckling and second-order effects may govern structural design.<br /><br />The study provides a computationally efficient analytical framework for assessing short jetty piles under transient lateral loads, while recognizing the importance of considering pile flexibility and full-length load distribution.

Keywords

short piles

transient lateral response

jetty piles

ship berthing impact

pile-soil interaction

lateral stiffness

beam-column model

soil springs

equivalent mass and damping

bending moments