Comparative Dynamic Response Analysis of Pratt and X-Braced Offshore Jacket Substructures for Wind Energy Development in the North Java Sea

Offshore wind energy has emerged as a critical solution in the global effort to reduce greenhouse gas emissions and transition toward sustainable energy systems, particularly in Indonesia, where fossil fuels remain dominant. The North Java Sea, with its favorable wind conditions and suitable water depths, offers significant potential for offshore wind development. This study evaluates the dynamic structural performance of jacket substructures with two bracing configurations: Pratt and X-bracing for supporting a 3 MW offshore wind turbine in this region. Through comparative numerical analysis, the research assesses key structural responses, including natural frequencies and lateral displacements, under site specific wind, wave, and current conditions. The findings aim to identify the most efficient configuration for ensuring structural reliability and long-term performance in Indonesia's offshore wind applications. Site specific metocean data and environmental conditions were incorporated into numerical models developed in Bentley SACS software. The jackets were analyzed under extreme wave, wind, and current loads, combined with 12 Design Load Cases (DLCs) of the wind turbine based on the international standards and as detailed in the international journal. Key parameters evaluated include natural frequencies, directional displacements, and structural integrity through eigenvalue analysis and utilization checks. Results show that the X-braced configuration provides higher global stiffness, improved dynamic stability, and better resistance to resonance due to elevated natural frequencies. Conversely, the Pratt configuration exhibited slightly larger displacements and lower modal stiffness, although it remained within allowable stress limits. Both systems passed strength verifications, yet the X-bracing design demonstrated more uniform load distribution and enhanced performance under multidirectional loading. The study contributes to the optimization of support structures in tropical offshore environments, offering a reference for future offshore wind infrastructure development in Indonesia and Southeast Asia. Practically, the findings support efficient substructure selection for offshore projects, while socially, they aid in accelerating Indonesia's renewable energy transition and fostering green job creation. This research emphasizes the importance of structural configuration in ensuring offshore wind turbine safety and reliability under dynamic marine conditions. © 2025 by authors, all rights reserved.