Effect of Turbine Weight on the Seismic Response of a Wind Turbine-Monopile System Located in Liquefied Multilayer Soil

The core objectives of sustainable development are to develop access to renewable, sustainable, reliable, and cost-effective resources. Wind is an essential source of renewable energy, and monopile wind turbines are one method proposed for harnessing wind power. Offshore wind turbines can be vulnerable to earthquakes and liquefaction. This numerical study defined the effects of wind turbine weight on the seismic response of a wind turbine-monopile system located in liquefied multilayered soil with layer thicknesses of 5, 10, 15, and 20 m using four far-field records. OpenSees PL analysis indicated that if the liquefied sand had a lower density or a thickness of more than 10 m, then an increase in the earthquake acceleration beyond 0.4 g caused the pile to float like liquefied soil and to lose its vertical bearing capacity. Moreover, increasing the wind turbine power from 2 to 5 kW had no significant effect on the soil-structure interaction response. As the earthquake acceleration increased, the bending moment of the pile-column also increased as long as liquefaction did not occur and the pile-column deformation remained rotational-spatial in shape. As the acceleration and liquefaction increased and the pile began to float in response to its transverse motion, there was no significant difference in the pile-column displacement along the length, but there was a decrease in the pile-column bending moments. As this phenomenon increased and the pile continued to float, transformation of the pile increased the difference between the displacement of the pile-column along its length and further increased the bending moments. These results were derived from multiple correlation analysis, the bending moment relations, and lateral displacement of the pile-column of the wind turbine.

Centrifugal and numerical modeling of stiffened deep mixed column-supported embankment with slab over soft clay

A stiffened deep mixed (SDM) column can significantly increase the bearing capacity, reduce settlement, and enhance the slope stability of soft clays as compared with a conventional deep mixed (DM) column. This technique involves inserting plain concrete, reinforced concrete or a steel pile into the center of the DM column after the DM column is constructed. In this paper, a series of centrifugal modeling tests were conducted to investigate the performance of an SDM column-supported embankment over soft clay. A model embankment supported only by DM columns was constructed for comparison. Two ideal numerical models of column-reinforced soil under equal stress and equal strain conditions were established to explore the role the column played in accelerating soil consolidation. A parametric study was conducted to investigate the influence factors of the length of the core pile, column spacing, thickness of the underlying soil, modulus and thickness of the cushion, and modulus of the slab on the load transfer of the system, and some recommendations were proposed for its application. The load-transfer mechanism of an SDM column-supported embankment system with a slab was established based on the development of the volumetric strains and the principal stresses in the numerical models.

MULTIPLE CRITERIA SELECTION OF PILE-COLUMN CONSTRUCTION TECHNOLOGY

Numerous alternatives exist for foundation systems and construction technologies. The systems can be described by different criteria values which are incorporated in the conventional design process. Decision on the most suitable construction technology is vital for success and depends on many effectiveness criteria. The business success depends on the right choice. The mandate of a construction management researcher is to use rational, systematic, science-based techniques to inform and improve various decisions. The paper presents multiple criteria decision making model for selection of a pile-column technology. The technological criteria are determined by an experimental study. Based on in-situ investigation of natural soil conditions, criteria values are determined. The decision making model incorporates five different methods and techniques. To solve a problem, it uses three multiple criteria decision making methods. Integrated criteria weights are determined by using the analytic hierarchy process and the expert judgement method. This model could be used to solve complicated problems pertaining to the selection of a construction technology.