Pile foundations are extensively used to support on-shore and off-shore structures. Under the action of wind and sea waves arising due to sea storms, sea quakes, hurricanes, and tsunamis, pile foundations for off-shore structures experience dynamic loads. Pile-soil-pile interaction and nonlinear soil behavior play an important role in the analysis. A step-by-step procedure for the analysis of pile foundations supporting offshore structures and including the nonlinear behavior of soil are presented. A review of solutions for single piles, pile-soil-pile interaction are also included. However, Response of pile foundations under the influence of these loads is different from that of earthquake loads.
Offshore structures consist of production platforms and other structures and structural components of systems such as offshore storage facilities, combination of storage and production structures and coastal research, and support facilities. Some nuclear power plants may also be located offshore. These structures are often supported on pile foundations to resist dynamic loads arising from wind or wave currents due to sea storms, hurricanes, sea quakes and/or tsunamis. Figure 1 shows a typical pile supported structure. The bulk of loads are static loads, which form the basis for fixing the section (size), embedded length and possibly configuration (spacing and arrangement) of the piles in the group. The super-structure forms an integral part of the pile-foundation system. Therefore, an analysis of the structure-pile-soils system and its proper understanding is desirable. Very little information is available on the behavior and analysis of pile supported offshore structures for use in everyday practice. The nature of loading and associated strain levels and soil-pile and pile group responses under wave loading on offshore structures are quite different from earthquake loadings on the similar onshore and offshore structures. Earthquake loading for piles under buildings may cause large deformations and soil nonlinearity and considerable degradation of soil modulus.