Cyclic lateral response of pile foundations in offshore platforms

Fixed offshore platforms supported by pile foundations are always subjected to lateral cyclic loads due to environmental conditions. In general, nonlinear pile–soil interaction is the most important source of nonlinear response of offshore platforms due to design environmental loads. Finite element models are high precision method in simulation of the pile soil interaction problems however these analyses are usually complex and computationally expensive. In contrast, Beam on Nonlinear Winkler Foundation (BNWF) models are versatile, efficient and can possess sufficient precision. In this paper a new robust and practical BNWF model is presented for lateral behaviour of pile foundations under cyclic lateral loads. This cyclic pile–soil interaction model is incorporated as a user element into a general finite element software (ABAQUS) and can be easily used for complicated nonlinear strength analysis of fixed platforms. Monotonic or cyclic loading, gap formation and development, drag force and different backbone curves recommended by American Petroleum Institute can be easily used in this BNWF model. This paper deals with the effects of cyclic pile soil interaction on lateral response of offshore piles. Different parts of this BNWF model are discussed and addressed in detail. The piles behaviour in an example fixed offshore platform are investigated under lateral cyclic and monotonic loadings.