In‑Place Analysis for Structural Integrity Assessment of Fixed Steel Offshore Platform

摘要

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessmentfor existing structures. The structural integrity of platform components under the maximum and minimum operating loadsof environmental conditions is required for risk assessment and inspection plan development. In-place analyses have beenexecuted to check that the structural member with all appurtenances has robustness and capability to support the appliedloads in either storm condition or operating condition. A nonlinear finite element analysis is adopted for the platform structureabove the seabed and the soil–pile–jacket interaction to estimate the in-place behavior of a typical fixed offshore platform. Theanalysis includes an interpretation of the dynamic design parameters based on the available site-specific data, together withfoundation design recommendations for in-place loading conditions. The SACS software is utilized to calculate the naturalfrequencies, dynamic amplification factors, and the stresses at selected members, as well as their nodal displacements. Thedirections of environmental loads and water depth variations have important effects on the results of the in-place analysisbehavior. The incidence angle of seismic waves is an essential parameter, where, for some crucial angles, the internal forcesand the maximum deformations can be doubled or more in comparison with the ones corresponding to other, less crucialangles. Therefore, the incidence angle considerably affects the response quantities. The results confirm that the in-placeanalysis is quite essential for the reliable design of new offshore platforms and the assessment of existing offshore structures.