Controlling of Monopile Seismic Response Using Concrete Skirt

Bridges are considered one of the major infrastructure projects that pose many challenges for design and construction. This is because they require highly efficient structural systems that last for many years, require minimal maintenance, and provide a short construction period. Monopiles are the most common foundation system concept in wind turbines, but they have also proven to be an economically sound foundation solution in bridge foundation systems (as seen in monorails, railway bridges, bridges extensions and ramps) owing to their simple design, easy construction, low manufacturing costs, and minimal excavation work. However, the durability of bridges resting on monopiles and their capability of resisting lateral loads, especially under seismic excitation, remains a concern and is the most important requirement to avoid severe damage. The purpose of this study is to determine the effect of adding a concrete skirt to monopile foundations in improving their seismic response. Installed around the monopile's base, the proposed concrete skirt aims to improve soil-structure interaction, increase lateral stiffness, and improve energy dissipation. Parametric analysis and numerical simulations were used to investigate how the skirt geometry and soil characteristics affect seismic performance. The results show that adding a concrete skirt significantly reduces the monopile's acceleration by up to 75%, shear forces by 65%, bending moments and lateral deformations by 65% and 50% respectively, depending on soil conditions, concrete skirt geometry, and seismic intensity, affording a practical and reasonable solution to increase the seismic resilience of structures supported by monopiles.