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Content archived on 2022-12-27

SUCTION PILE PLATFORM CONCEPT OF MONO TOWER TYPE

Objective

General. The purpose of the project is to demonstrate the feasibility of a three-legged platform with suction pile foundation. The piles will be an integrated part of the structure.
In particular, the possible utilization of the suction effect arising when a closed-top pile is exposed to tension, will be examined.
The platform concept is of the monotower type. The monotower has three legs, each of which supported on a suction pile.
The platform will be designed for dynamic loads from waves and vortex shedding.
The topside facilities will be minimal. The platform will be unmanned and most of the traditional process and safety equipment will be left out. Access to the platform will be from boat.
The topside facilities will not be examined in this project.
Because of the low deck load, the dominating loads will be the horizontal environmental loads. Hence the size of tension and compression loads in the piles will be approximately the same.
Preliminary results show that it is possible to formulate a geotechnical calculation model for the breakout capacity of suction piles embedded in pure sand or clay profiles.
This is despite the fact that an extensive literature study showed that the subject only scarcely was covered and none of the sources tried to quantify the mechanism of a load induced suction and its favourable effect on the pile pull-out resistance.
It is believed that within the next project period, a simplified model for the breakout resistance of a suction pile will be formulated and incorporated in the ongoing design calculations and thus enable more detailed calculations.
The following main results have been achieved:
- a model for breakout resistance of a suction pile in either pure sand or clay has been developed;
- an approach which transforms the breakout resistance model into a boundary condition suitable for the structural analyses of the platform has been developed;
- a non-linear dynamic time domain simulation method for ship collision has been developed;
- accurate stress concentration factors have been calculated for the centre column joint;
- the primary laboratory test series have been carried out.
In this R&D project the intention is to investigate the feasibility of a platform consisting of a monotower supported on a 3-legged subbase, where the conventionally driven piles will be replaced by suction piles.
The new development in this project is to use the suction principle when installing the three foundation piles of the monotower platform and also to take into account the vertical suction effect being developed when the foundation pile(s) are subjected to short time vertical tension (pull out) forces due to dynamic loads from waves and vortex shedding on the superstructure.
This project is divided into five main phases of which :
Phase 1 :
Technical Analysis covers collection of state of the art data in order to establish an initial platform concept and a geotechnical calculation model as a basis for the detailed structural analyses.
Phase 2 :
Economic Analyses covers a comparison between a traditional platform concept and a suction pile concept with respect to fabrication, installation and removal costs.
Phase 3 :
Reporting reports on Phase 1 and 2.
Phase 4 :
Laboratory test supports the geotechnical calculation model with model results and makes reevaluation of the theoretical calculation model possible.
Phase 5 : Re-calculation and reporting is the summarizing phase in which the platform is re-designed, platform costs are re-evaluated and the final report is written.

Call for proposal

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Coordinator

RAMBOLL & HANNEMANN
EU contribution
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Address
FRODESGADE 125 A
6700 Esbjerg
Denmark

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Total cost
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