Surin Kim

Investigation of Monotonic and Cyclic Behavior of Tripod Suction Bucket Foundations for Offshore Wind Towers Using Centrifuge Modeling

This paper performed centrifuge load tests of a tripod bucket foundation preliminarily designed as a supporting system of wind turbines and compared the results to those obtained from a test of a monopod bucket foundation. The tripod foundation prototype studied in this study has three bucket caissons, each of which is 6.5 m in diameter and 8.0 m in length. The center-to-center distance between the buckets was 26.9 m. The site is composed of an 11-m thick layer of dense silty sand overlying a thick sandy silt layer. The horizontal load was applied at a height of 33 m from the seabed floor according to the design load condition, and the vertical load was simulated by the self-weight of the model. The moment-rotation angle curves for the tripod foundations were compared with that of the monopod bucket foundation. The moment-rotation curve of the tripod was nearly bilinear, whereas that of the monopod showed a gradual decrease in slope. The yield moment for the tripod foundation was half that of the monopod, but the rotation angle for the yield moment was only 20% that of the monopod. The behavior of the tripod foundation under a cyclic load with respect to the accumulated plastic deformation has also been examined in this study. When the resultant moment of cyclic loading was smaller than the monotonic yield moment, negligible accumulated plastic deformation was observed for both one-way and two-way loading. However, when the resultant moment was higher than the monotonic yield moment, significant cumulated deformation resulted.

Pullout Capacity of Horizontally Loaded Suction Anchor Installed in Silty Sand

Current floating structures require more reliable and higher anchoring capacities because of their increased size. A suction anchor is one of the most popular anchors for a floating system. In this study, the behavior of a suction anchor installed in cohesionless soil was investigated when the anchor was subjected to mainly a horizontal load. Three-dimensional finite element numerical analyses were carried out using ABAQUS, and three centrifuge tests were performed to calibrate the numerical analyses. A parametric study with different dimensions and loading points for the suction anchor was conducted. The horizontal capacity of the suction anchor was estimated, and the soil reaction distribution was analyzed when the load was applied at the optimal point. Based on the results, an analytical equation for calculating the horizontal capacity of a suction anchor was proposed that can be easily adopted for design.

Evaluation of Behaviors on Mooring Line Embedded in Sand Using Centrifuge Test

When an anchor penetrates and is installed under a seabed, a portion of the mooring line connected to the anchor is also embedded under the seabed. This embedded mooring line affects the capacity of the anchor in two ways. First, the frictional resistance that occurs between the mooring line and the seabed reduces the pulling force acting on the anchor. Second, the embedded part of the mooring line forms a reverse catenary shape due to the bearing resistance of the soil, so that an inclined pulling force is applied to the anchor. To evaluate the mooring lines effect on the capacity of an anchor in sand, centrifuge model tests were performed using two relative sand densities of 76% and 51% while changing the anchor depths. The test results showed that the load is reduced much more in deep and dense sand, and the inclination angle of the load is lower in shallow and loose sand.

Capacity of Horizontally Loaded Suction Anchor Installed in Silty Sand

A suction anchor is one of the most popular anchors for deepsea floating systems. An anchor used for catenary mooring is predominantly under a horizontal load. In this study, the behavior of a suction anchor installed in cohesionless soil was investigated when the anchor was mainly subjected to a horizontal load induced by a catenary line. In order to study the behavior of the suction anchor, 3D FEM analysis models were developed and analyzed. Depending on the location of the load (padeye), the ultimate horizontal load was monitored. The distributions of the reaction forces around the anchor induced by the seabed were analyzed using the circumferential stress to understand the behavior of the suction anchor under a horizontal load.