Freeze-induced degradation behavior of offshore wind power platform foundations

The development of offshore wind power platforms in cold regions faces significant durability challenges due to environmental factors. Tidal movements induce substantial temperature differentials, while coupled wet-dry cycles and freeze-thaw cycles (FTCs) cause extensive foundation damage, including erosion, surface spalling, and micro-cracking, ultimately compromising structural integrity. To address these issues, a micro/meso-level simulation method is proposed, analyzing foundation concrete's FT damage through pore deformation mechanisms while accounting for seawater (SW) effects on FTCs, environmental coupling, and macro-level material behavior. Calculations indicate that FT damage initially occurs in interface transition zones (ITZs), and as FTCs increase, micro-cracks connect, forming a network linked to the ITZs and large voids, which aligns with experimental results rather than porous medium theory calculation results. The thickness of SW-FT damage spalling is primarily influenced by the depth of SW erosion, with ITZs experiencing increasingly severe damage that leads to aggregate dislodgement after more than 75 FTCs. Moreover, the increase in “compaction” effect arises from the generation of new gel pores, and the “compaction” effect occurs during the whole compressive loading process, not only just at the beginning of loading. While offshore platform foundation designs focus on elastic behavior, wind loads significantly reduce stiffness, particularly strong winds and cyclic loads, threatening structural safety, making accurate prediction and analysis crucial for life-cycle design in extreme environments.