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Proceedings of the Sixth (1996) - International Offshore and Polar Engineering Conference (1996) Los Angeles, USA May 26-31, 1996 Copyright © 1996 by The International Society of Offshore and Polar Engineers ISBN 1·880653-22·2 (Set); ISBN 1·880653·23·0 (Vol. I) Shamsher Prakash and Sanjeev Kumar University of Missouri-Rolla, Rolla, MO, USA V.K. Puri Southern Illinois University, Carbondale, IL, USA 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. Interactions of the super-structure with piles is important. In offshore structures, the piles are especially long and slender with considerable free-standing lengths and therefore, in addition to large displacements and soil nonlinearity, even pile material may behave in non-linear manner, and buckling of piles may assume importance (Prakash, Sally 1985, 1987). In this paper a step-by-step procedure for complete analysis of pile groups has been recommended. A simple procedure to include the effect of soil nonlinearity, under wave loadings has also been presented. NATURE OF DYNAMIC LOADING ON OFFSHORE STRUCTURES A signifIcant portion of the load on offshore structures consists of load arising out of the action of wind, sea currents and T

Shamsher Prakash and Sanjeev Kumar - ISOPE 1996/Abstract... · Shamsher Prakash and Sanjeev Kumar University of Missouri-Rolla, Rolla, MO, USA V.K. Puri Southern Illinois University,

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Page 1: Shamsher Prakash and Sanjeev Kumar - ISOPE 1996/Abstract... · Shamsher Prakash and Sanjeev Kumar University of Missouri-Rolla, Rolla, MO, USA V.K. Puri Southern Illinois University,

Proceedings of the Sixth (1996) - International Offshore and Polar Engineering Conference (1996)Los Angeles, USA May 26-31, 1996Copyright © 1996 by The International Society of Offshore and Polar EngineersISBN 1·880653-22·2 (Set); ISBN 1·880653·23·0 (Vol. I)

Shamsher Prakash and Sanjeev KumarUniversity of Missouri-Rolla, Rolla, MO, USA

V.K. PuriSouthern Illinois University, Carbondale, IL, USA

Pile foundations are extensively used to support on-shore andoff-shore structures. Under the action of wind and sea wavesarising due to sea storms, sea quakes, hurricanes, and tsunamis, pilefoundations for off-shore structures experience dynamic loads. Pile-soil-pile interaction and nonlinear soil behavior play an importantrole in the analysis. A step-by-step procedure for the analysis ofpile foundations supporting offshore structures and including thenonlinear behavior of soil are presented. A review of solutions forsingle piles, pile-soil-pile interaction are also included. However,Response of pile foundations under the influence of these loads isdifferent from that of earthquake loads.

Offshore structures consist of production platforms and otherstructures and structural components of systems such as offshorestorage facilities, combination of storage and production structuresand coastal research, and support facilities. Some nuclear powerplants may also be located offshore. These structures are oftensupported on pile foundations to resist dynamic loads arising fromwind or wave currents due to sea storms, hurricanes, sea quakesand/or tsunamis. Figure 1 shows a typical pile supported structure.The bulk of loads are static loads, which form the basis for fIxingthe 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-soilssystem and its proper understanding is desirable. Very littleinformation is available on the behavior and analysis of pilesupported offshore structures for use in everyday practice. Thenature of loading and associated strain levels and soil-pile and pilegroup responses under wave loading on offshore structures are quitedifferent from earthquake loadings on the similar onshore and

offshore structures. Earthquake loading for piles under buildingsmay cause large deformations and soil nonlinearity and considerabledegradation of soil modulus. Interactions of the super-structure withpiles is important. In offshore structures, the piles are especiallylong and slender with considerable free-standing lengths andtherefore, in addition to large displacements and soil nonlinearity,even pile material may behave in non-linear manner, and bucklingof piles may assume importance (Prakash, Sally 1985, 1987).

In this paper a step-by-step procedure for complete analysisof pile groups has been recommended. A simple procedure toinclude the effect of soil nonlinearity, under wave loadings has alsobeen presented.

NATURE OF DYNAMIC LOADING ON OFFSHORESTRUCTURES

A signifIcant portion of the load on offshore structuresconsists of load arising out of the action of wind, sea currents and

T