A Study on Installation Procedure of Pre-fabricated Tendon of TLP

Abstract

Recently, many kinds of projects and concepts of TLP are presented. In these TLPs, many types of tendons are also presented. One of the most promising type of tendon is light weight tendons which have been selected in Jolliet project. This type of tendon is generally fabricated on the land in an overall length. And these tendons must be investigated not only behavior and strength of tendons in working condition but also the method and the strength of tendons in the towing and the installation condition. One of methods for the installation condition is the free dropping procedure. In the installation condition using a free dropping procedure, it is possible that the behavior of displacement and stresses on the tendon will be affected by the vortex induced vibration.Therefore, in-line forces acting on the oscillating cylinder in the uniform flow are investigated experimentally in order to clarify the behavior of tendons. From the experimental result, the maximum in-line force at small oscillating amplitude is found at the reduced velocity between 46. And It is necessary to estimate not only transverse forces but also in-line forces precisely, especially when the vortex shedding frequency coincides with one of the structural frequency.Afterward, the tank tests on the installation condition using the free dropping procedure of tendons are performed to verify a simulation method. The deformation and bending strains are measured. In the free dropping tests, the tendon model is freely dropped under the condition that the one end is supported by the pin joint. After that, the simulation analysis is performed using the time domain and non-linear FEM program. In the simulation analysis, three types of drag coefficients are selected. The first is set at the constant value. The second is the estimated value at the resonant region caused by the vortex induced vibration. The third is dependent on dropping speed of tendon. The results of simulation analysis are compared with the experimental ones for the deformation and stresses of tendon. When the drag coefficient which is dependent on the dropping speed is used in the analysis, the experimental and the analytical results coincide qualitatively and quantitatively.