Response of fixed offshore platforms to environmental loads

Pile foundations that support bridge piers, offshore platforms and marine structures are required to resist not only static loading but also lateral dynamic loading. Static p-y curves are widely used when analyzing response of piles to lateral loads in order to relate pile deflections to nonlinear soil reactions. The p-multiplier concept is used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Previous studies have examined the validity of the p-multiplier concept for the static and cyclic loading cases. The concept of using p-y curves and p-multipliers in the analysis of pile groups has been extended for the dynamic loading case in the current study. The proposed analysis incorporates the static p-y curve approach and plane strain assumptions to represent the dynamic soil reactions within the frame of a Winkler model. The model accounts for the nonlinear behaviour of the soil, energy dissipation through the soil and the pile group effect. The model was validated by analyzing the response of pile groups subjected to lateral Statnamic loading and comparing the results with field measured values. An extensive parametric study was performed employing the proposed analysis and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and clay under harmonic loading with varying frequencies applied at the pile head. “Dynamic” p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curves for a single pile. Dynamic p-y curves and p-multipliers were implemented in widely used finite element package to analyze the response of pile groups supporting various structures.; In the second part of the study, the response of a jacket offshore platform is investigated accounting for foundation flexibility and the nonlinear behaviour of the supporting piles. The soil resistance to the pile movement is modeled using dynamic p-y curves, dynamic t-z curves and q-z curves to account for soil nonlinearity and energy dissipation through radiation damping. The response of fixed offshore structures to transient loading due to a range of wave loadings is presented. (Abstract shortened by UMI.)...