Modular Co-casting Method for Basalt Fiber Reinforced Cages and Steel Structures on Offshore Platforms

Abstract

This invention discloses a modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms, belonging to the field of marine engineering technology. The method includes steps such as the preparation of prefabricated modules, classification and splicing of prefabricated modules, and on-site assembly of floating pontoons. It also proposes optimized solutions for enhanced sealing treatment, internal rebar installation, external rebar installation, and overall encapsulation with ultra-high performance concrete. This invention can use low water-cement ratio, high impermeability and compressive strength concrete materials to perform integrated external casting of the prefabricated module splices, forming a seamless integral structure. This avoids the high cost of using all ultra-high strength concrete and completely solves the technical bottlenecks of traditional modular floating pontoons, such as joint leakage, poor structural integrity, and easy corrosion of metal connectors. It achieves a balance between excellent durability, ultra-high safety, and economic efficiency throughout the entire life cycle for marine floating structures, and is suitable for major facilities such as large floating wind power platforms in deep-sea areas.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to a modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms. Background Technology

[0002] As marine resource development moves towards deeper waters, the construction costs of traditional fixed offshore platforms have increased dramatically, making floating platforms (such as semi-submersible, tension leg, Spar, and barge types) the mainstream choice. Among them, concrete floating structures have attracted widespread attention due to their advantages such as corrosion resistance, low maintenance costs, and good stability.

[0003] Existing concrete floating structures mainly fall into two technical routes: monolithic casting and precasting, and segmented precasting and splicing. Monolithic casting and precasting (such as building large concrete hulls in dry docks) offers good quality control and optimal structural integrity, but it is limited by site constraints and lifting capacity, making it difficult to construct ultra-large structures or hindering mass production. Segmented precasting and splicing, on the other hand, involves manufacturing standardized modules, assembling them on shore or at a dock, and then launching them, or towing them wet-to-the-site for final assembly. This method offers high flexibility and is currently the mainstream approach.

[0004] However, existing concrete module splicing technology has significant bottlenecks: 1) Sealing and Durability Challenges at Joints: Modules are typically connected using prestressed steel cable tensioning or flange bolts. Prestressed systems require extremely high construction precision and corrosion resistance, and are at high risk of long-term stress relaxation. Flange bolt connections are more common, but they rely on rubber waterstops (rings) for sealing and waterproofing. Under long-term, complex wind and wave cycles, temperature changes, and material aging, the rubber is prone to failure, and the bolts may loosen, leading to joint leakage. Seawater infiltration not only increases weight and affects stability, but more seriously, chloride ion intrusion can corrode internal steel bars or prestressing tendons, threatening structural safety.

[0005] 2) Insufficient structural integrity: The bolted connections between modules are semi-rigid or hinged, resulting in a significant reduction in overall stiffness compared to monolithic cast-in-place structures. Under harsh sea conditions, fretting wear and stress concentration are prone to occur at the joints, becoming the source of fatigue crack initiation and affecting the long-term fatigue life of the structure.

[0006] 3) Corrosion risk of steel structures: Flanges, bolts, and other metal connectors are directly exposed to the marine atmosphere or splash zone, which are the areas most severely affected by corrosion. Even with heavy-duty anti-corrosion coatings, regular, expensive, and difficult maintenance is still required; otherwise, connection failure will occur.

[0007] To address these issues, the industry has tried various methods, such as adding secondary grouting at the joints and wrapping with steel plates. However, most of these are passive repairs that fail to fundamentally solve the problem of joints being a performance bottleneck and introduce new corrosion or maintenance points.

[0008] Therefore, there is an urgent need for a new method for constructing offshore platform pontoons that can retain the advantages of modular prefabrication in terms of efficiency and flexibility, while fundamentally overcoming defects such as poor joint sealing, weak structural integrity, and easy corrosion of metal parts. Against this backdrop, this invention proposes a systematic and innovative solution from materials (ultra-high strength concrete, basalt fiber reinforcement) to construction (overall encapsulation). Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a modular collaborative casting method for basalt fiber reinforced cages and steel structures for offshore platforms.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: This invention first proposes a modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms, comprising the following steps: S1. Preparation of prefabricated modules: S1-1, Preparation of steel mold: An arc-shaped steel mold is formed by welding two rectangular flanges and two fan-shaped flanges. The outer surface of the rectangular flanges is provided with equally spaced straight raised strips, and the outer surface of the fan-shaped flanges is provided with equally spaced arc-shaped raised strips. The edges of the rectangular flanges and the fan-shaped flanges are respectively provided with flange holes. S1-2, Binding basalt fiber reinforcement: Arrange curved basalt reinforcements and straight basalt reinforcements inside the curved steel mold, and bind them with wire or straps to form a fiber grid parallel to the opening surface of the curved steel mold. Arrange 2-4 sets of fiber grids with different diameters and equal spacing according to the thickness requirements. S1-3, Casting and molding of prefabricated modules: Arrange arc-shaped templates on the two opening faces of the arc-shaped steel mold to form an arc-shaped casting cavity. Reserve the casting port and make the flange hole outside the arc-shaped casting cavity. Use high-performance concrete to inject from the bottom, high-frequency vibration to vent air, and ordinary curing for 5-10 days to obtain a precast module composed of the casting body and the arc-shaped steel mold. S2. Classification and assembly of prefabricated modules: When two sector-shaped flanges have the same diameter, prefabricated modules with the same upper and lower sector-shaped end plane dimensions are produced. These modules are then fastened with screws and assembled on the ground or ship hull to form a cylindrical assembly. When the two sector-shaped flanges have different diameters, prefabricated modules with different upper and lower sector-shaped end plane dimensions are produced. These modules are then fastened with screws and assembled on the ground or ship hull to form a conical assembly. S3. On-site assembly of pontoons: By using a hoisting method, the upper and lower end faces of the cylindrical assembly are connected to the conical assembly with screws to obtain the pontoon; Specifically, the high-performance concrete in S1-3 is C60-C100 concrete, which ensures a dense wrapping of complex nodes; when it is poured to the top surface of the partition baffle, the main body area is poured immediately and continuously, and the concrete flow naturally forms a dense, cold-joint-free bonding surface.

[0011] Specifically, in S2, the straight protrusions of adjacent prefabricated modules have different thicknesses and are misaligned, forming a groove between adjacent straight protrusions of the prefabricated module for engaging the straight protrusion of another prefabricated module. A water-stop strip is placed between the straight protrusion and the groove. Similarly, the arc-shaped protrusions of adjacent prefabricated modules have different thicknesses and are misaligned, forming a groove between adjacent arc-shaped protrusions of the prefabricated module for engaging the arc-shaped protrusion of another prefabricated module. A water-stop ring is placed between the arc-shaped protrusion and the groove for waterproofing the joint.

[0012] To enhance the sealing performance of the pontoon, this invention adds the following steps to the aforementioned modular co-casting method for basalt fiber reinforced cages and steel structures on offshore platforms: S4. Joint Sealing Enhancement: First, pressure inject non-shrink epoxy grout into the flange gap; then fill the pre-reserved groove on the outside of the joint with polyurethane water-swellable sealant; finally, use a three-layer cloth and five-layer oil manual lamination process to form a fiberglass protective cover with a thickness of not less than 5mm on the outside of the sealant using vinyl ester resin and alkali-free glass fiber cloth.

[0013] To enhance the strength of the pontoon, this invention adds the following step, namely, the internal rebar anchoring method, to the aforementioned modular co-casting method of basalt fiber reinforced cages and steel structures for offshore platforms: In the splicing of S2 and the assembly of S3, some flange holes are reserved inside the cylindrical and conical assemblies. Basalt fiber straight ribs are inserted into the flange holes and basalt fiber arc ribs are tied to further enhance the strength of the pontoon.

[0014] To simultaneously enhance the sealing and strength of the pontoon, this invention adds the following steps to the aforementioned modular collaborative casting method of basalt fiber reinforced cages and steel structures for offshore platforms: external reinforcement and casting method. S5. On-site casting of the outer surface: In the splicing of S2 and assembly of S3, some flange holes are reserved on the outside of the cylindrical and conical assemblies. Basalt fiber straight bars are inserted into the flange holes and basalt fiber arc bars are tied. Ultra-high strength concrete is poured and sealed section by section. Ordinary curing for 5-10 days forms a reinforced pontoon with an encapsulated outer surface to prevent the steel structure from being exposed and corroded.

[0015] Furthermore, the ultra-high strength concrete is C160-C180 concrete, and its formula per cubic meter includes: 620-650 kg of P·Ⅰ52.5R cement, 70-80 kg of silica fume, 30-40 kg of S115 grade ultrafine mineral powder, 20-30 kg of nano-activated calcium carbonate, 500-550 kg of basalt fine stone with a particle size of 0.8-2.0 mm, 560-600 kg of quartz sand with a particle size of 0.15-0.8 mm, 200-250 kg of ultrafine quartz sand, 25-30 kg of basalt fiber with a length of 6-12 mm, 2-3 kg of polypropylene coarse fiber with a length of 3-6 mm, 18-22 kg of polycarboxylate-based high-efficiency water-reducing agent, 3-5 kg ​​of composite rust inhibitor, and 130-150 kg of pretreated desalinated seawater, with a water-cement ratio of 0.16-0.18.

[0016] This invention also proposes an offshore floating wind power platform manufactured using the aforementioned modular collaborative casting method, comprising at least three pontoons or reinforced pontoons, wherein the pontoons or reinforced pontoons are arranged in an equilateral triangle and connected as a whole by a steel-concrete composite top support structure, such as... Figure 5 As shown, its preparation may include the following steps: 1. Docking Phase: The supporting platform is hoisted to the top transition section of the pontoon using a floating crane. The flange alignment accuracy is adjusted (axial deviation ≤3mm, horizontal error ≤2mm / m). High-strength anti-corrosion bolts (diameter ≥36mm, evenly distributed circumferentially, spacing 150-200mm) are inserted. A three-step tightening method (initial tightening → secondary tightening → final tightening) is used. The pre-tightening force is double-calibrated using a torque wrench and axial force gauge to ensure uniform force distribution. Adjacent module flanges are aligned, sealed with rubber anti-corrosion gaskets to prevent leakage, and tightened with high-strength anti-corrosion bolts. The bolts are equipped with lock nuts to adapt to marine vibration conditions. Marine-grade epoxy putty is injected into the flange gaps for secondary sealing to prevent seawater infiltration.

[0017] 2. Reinforcement Stage: Truss connecting frames are used to reinforce the pontoons with each other and with the central support. These frames are constructed using steel-concrete composite. Every 3-5 meters along the outer surface of each pontoon, a rubber ring or lightweight, high-strength thermoplastic material (recycled waste rubber or polyurethane thermoplastic material can be used) with a width of at least 160mm and a thickness of at least 200mm is installed at each midpoint. This unique anti-collision device significantly protects against general impacts and enhances the effective collision protection of the concrete floating pontoons.

[0018] 3. The truss connecting frame is a spatial load-bearing system, consisting of an upper layer, a lower layer, and an intermediate support structure, ensuring that the load is evenly distributed across the three pontoons: Upper Truss: Located near the top of the pontoon's supporting platform, it is welded or bolted to the steel components at the bottom of the platform. It primarily bears the vertical and horizontal wind loads transmitted by the wind turbine tower, preventing localized stress concentration. A steel-concrete composite support system is used, with multiple triangular structures formed between the support's interior and the center of the tower connection section to maintain the stability of the supporting platform and the wind turbine tower.

[0019] Lower Truss: Located near the bottom of the pontoons and parallel to the sea level, it uses steel-concrete composite supports. The internal structure of the supports forms multiple triangles with the center of the tower connection section, utilizing the stability of triangles. Steel-concrete composite connecting beams are used to stably connect the triangular pontoons, primarily resisting the horizontal impact and torque from waves, and enhancing in-plane deformation resistance.

[0020] Intermediate support: Cross bracing is set between the pontoons and the central support to form a three-dimensional force network, which vertically transfers the upper load to the lower truss and then distributes it to the three pontoon nodes.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention combines the advantages of modular construction with the performance of an integral structure. It retains the advantages of prefabricated modules in terms of quality control, construction efficiency, and construction flexibility. Furthermore, through an integral encapsulation technology, the prefabricated modules, connectors, and reinforcing bars are bonded and wrapped into a continuous whole by using an ultra-high-strength concrete shell cast on-site as structural adhesive and protective shell. This completely eliminates the weak links in the mechanical connections between modules, making the mechanical performance and durability of the final structure comparable to that of an integral cast-in-place structure.

[0022] 2. To address the most stringent waterproofing and seepage prevention requirements of marine environments, this invention proposes a multi-layered sealing scheme that forms a synergistic defense mechanism. First, the interlocking design of the module interfaces and the elastic water-stopping elements constitute the first line of flexible defense, adapting to initial deformation. Then, pressure grouting and external high-performance sealant coverage of the joints achieve a secondary active seal combining rigidity and flexibility. The deepest mechanism lies in the ultra-high-strength concrete shell itself, which possesses extremely low porosity and chloride ion diffusion coefficient, forming a dense passive barrier that fundamentally prevents fluid penetration and the migration of corrosive ions, achieving absolute protection of the internal space of the structure.

[0023] 3. This invention strengthens the structure from both internal and external dimensions through continuous internal fiber reinforcement and external ultra-high-strength concrete encapsulation. The continuous internal reinforcement spans the joints, effectively improving the overall structural stiffness and crack resistance. The external encapsulation layer contributes extremely high compressive and flexural strength and works in conjunction with the internal structure. More importantly, this encapsulation layer permanently wraps all metal connectors in a dry, highly alkaline concrete environment, completely isolating them from water, chloride ions, and oxygen. This prevents the thermodynamic conditions for electrochemical corrosion reactions from forming, thus eradicating the fundamental degradation path of steel corrosion in marine engineering and ensuring a design life of over 100 years.

[0024] 4. This invention does not employ a single concrete formula, but rather develops a series of ultra-high-strength concretes with different performance emphases. By precisely controlling the composition of cementitious materials, water-cement ratio, and fiber type and dosage, an optimal combination of strength, toughness, and impermeability is achieved. In engineering projects, based on the functional requirements of different parts of the pontoon (e.g., the main load-bearing area requires the highest strength and impermeability, while the impact-resistant area requires optimal toughness), corresponding concrete formulas can be selected for differentiated pouring, achieving precise optimization of structural performance and efficient utilization of material resources. Furthermore, the assembled structure saves on the amount of ultra-high-strength concrete used.

[0025] 5. Although the initial construction involves high-performance materials and precision construction, the near-maintenance-free characteristics, ultra-long fatigue life, and fundamental corrosion resistance of this invention will generate significant economic benefits throughout the structure's entire service life. It transforms the high cost, periodicity, and high risk of later-stage maintenance, repairs, and potential downtime losses due to failure—traditional methods—into a one-time upfront investment, thereby achieving a substantial reduction in total cost and investment risk over the entire lifecycle. This has disruptive value for critical offshore infrastructure requiring long-term reliable operation. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the fabrication process of the prefabricated module in this invention. Figure 2 This is a flowchart illustrating the preparation process of the pontoon in this invention; Figure 3 This invention provides a sealing structure diagram for a water-stop strip; Figure 4 A sealing structure diagram of the water-stop ring is provided for this invention; Figure 5 This is a three-dimensional structural diagram of a floating offshore wind power platform manufactured using the modular collaborative casting method of basalt fiber reinforced cage and steel structure proposed in this invention.

[0027] In the diagram: 1: Prefabricated module; 101: Rectangular flange; 101A: Straight raised strip; 101B: Waterstop strip; 102: Fan-shaped flange; 102A: Arc-shaped raised strip; 102B: Waterstop ring; 103: Cast-in-place body; 103A: Arc-shaped basalt reinforcement; 103B: Straight basalt reinforcement; 2: Conical assembly; 3: Cylindrical assembly. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Example 1. A modular co-casting method for basalt fiber reinforced cages and steel structures on offshore platforms, comprising the following steps: S1. Preparation of prefabricated modules, refer to Figure 1 : S1-1, Preparation of steel mold: An arc-shaped steel mold is formed by welding two rectangular flanges 101 and two fan-shaped flanges 102. The outer surface of the rectangular flange 101 is provided with equidistant straight raised strips 101A, and the outer surface of the fan-shaped flange 102 is provided with equidistant arc-shaped raised strips 102A. The edges of the rectangular flange 101 and the fan-shaped flange 102 are respectively provided with flange holes. S1-2, Binding basalt fiber reinforcement: Arrange arc-shaped basalt reinforcements 103A and straight basalt reinforcements 103B inside the arc-shaped steel mold, and bind them with wire or straps to form a fiber grid parallel to the opening surface of the arc-shaped steel mold. Arrange 2-4 sets of fiber grids with different diameters and equal spacing according to the thickness requirements. S1-3, Casting and molding of prefabricated modules: Arrange arc-shaped templates on the two opening faces of the arc-shaped steel mold to form an arc-shaped casting cavity. Reserve the casting port and make the flange hole outside the arc-shaped casting cavity. Use high-performance concrete to inject from the bottom, high-frequency vibration to vent air, and ordinary curing for 5-10 days to obtain precast module 1. S2. Classification and assembly of prefabricated modules, refer to Figure 2 : When the two sector-shaped flanges 102 have the same diameter, a prefabricated module 1 with the same upper and lower sector-shaped end plane dimensions is produced. After being fastened with screws, it is spliced ​​on the ground or ship hull to form a cylindrical assembly 3. When the two sector-shaped flanges 102 have different diameters, prefabricated modules 1 with different upper and lower sector-shaped end plane dimensions are produced. They are then fastened with screws and spliced ​​on the ground or ship hull to form a conical assembly 2. S3. On-site assembly of pontoons: By using a hoisting method, the upper and lower end faces of the cylindrical assembly 3 are connected to the conical assembly 2 with screws to obtain the float. The high-performance concrete in S1-3 is C60-C100 concrete, which ensures that the complex nodes are tightly wrapped. When it is poured to the top surface of the partition baffle, the main area is poured immediately and continuously, and the concrete flow naturally forms a dense, cold-joint-free bonding surface.

[0030] Reference Figure 3-4 In step S2, the straight protrusions 101A of adjacent prefabricated modules 1 have different thicknesses and are misaligned, forming a groove between adjacent straight protrusions 101A of the prefabricated module 1 for engaging another straight protrusion 101A of the prefabricated module 1. A water-stop strip 101B is placed between the straight protrusion 101A and the groove. Similarly, the arc-shaped protrusions 102A of adjacent prefabricated modules 1 have different thicknesses and are misaligned, forming a groove between adjacent arc-shaped protrusions 102A of the prefabricated module 1 for engaging another arc-shaped protrusion 102A of the prefabricated module 1. A water-stop ring 102B is placed between the arc-shaped protrusion 102A and the groove for waterproofing the joint. Example 2. Enhancing the sealing performance of the pontoons: Based on the modular collaborative casting method in Example 1, the following steps are added: S4. Joint Sealing Enhancement: First, pressure inject non-shrink epoxy grout into the flange gap; then fill the pre-reserved groove on the outside of the joint with polyurethane water-swellable sealant; finally, use a three-layer cloth and five-layer oil manual lamination process to form a fiberglass protective cover with a thickness of not less than 5mm on the outside of the sealant using vinyl ester resin and alkali-free glass fiber cloth.

[0031] Example 3. Internal rebar anchoring method: To enhance the strength of the pontoon, the following steps are added to the modular collaborative casting method in Example 1: In the splicing of S2 and the assembly of S3, some flange holes are reserved inside the cylindrical assembly 3 and the conical assembly 2. Basalt fiber straight ribs are inserted into the flange holes and basalt fiber arc ribs are tied to further enhance the strength of the pontoon.

[0032] Formulation tests for ultra-high strength concrete (UHC): Preparation Example 1 (Silica fume-mineral powder composite C180): Mix proportions (per cubic meter): Cementitious materials: P·Ⅰ52.5R cement 620kg, silica fume 70kg, S115 grade ultrafine mineral powder 30kg, nano-activated calcium carbonate 20kg (total 740kg). Aggregates: Basalt fine stone (1-3mm) 500kg, medium quartz sand (0.15-0.8mm) 560kg, ultrafine quartz sand (0.01-0.15mm) 200kg. Fibers: Basalt fiber (12mm) 25kg, polypropylene coarse fiber (6mm) 2kg. Chemical admixtures: Polycarboxylate high-efficiency water-reducing agent (30% solid content) 18.2kg (adhesive material 2.46%), composite rust inhibitor 3.7kg, defoamer 0.3kg, silane coupling agent KH-550 1.0kg. Water: Pretreated desalinated seawater (Cl... - ≤80mg / L) 130kg (water-gel ratio 0.176).

[0033] Preparation process: Standard sequential stirring, total stirring time > 6 minutes, control the slump expansion at discharge ≥ 650 mm. After standard curing, the 28-day compressive strength is ≥ 180 MPa, and the chloride ion diffusion coefficient (RCM method) is < 2.0 × 10⁻⁶. -12 m 2 / s.

[0034] Preparation Example 2 (Economical C170 with High Blend): Compared to Preparation Example 1, the mix proportions were adjusted as follows: 600 kg cement, 50 kg silica fume, 60 kg S115 mineral powder, 15 kg nano-calcium carbonate (total 725 kg). 135 kg water (water-binder ratio 0.186). The total fiber content was slightly adjusted. 28-day strength ≥ 170 MPa.

[0035] Preparation Example 3 (High-toughness, impact-resistant C160): Compared to Preparation Example 1, the formulation was adjusted as follows: the fiber system was changed to 20 kg of basalt fiber, 4 kg of coarse polypropylene fiber, and 0.8 kg of PVA fiber was added. The water-to-binder ratio was 0.19. The 28-day strength was ≥160 MPa, and the number of drop hammer impacts was increased by more than 50% compared to Example 1.

[0036] Comparative preparation example 1 (without nanomaterials and fibers): Compared to Preparation Example 1, the mix proportions were adjusted: silica fume, nano-calcium carbonate, and all fibers were removed, and only cement and mineral powder were used, with a water-cement ratio of 0.32. The 28-day strength was approximately 45 MPa, indicating poor durability.

[0037] Comparative preparation example 2 (high water-to-binder ratio, ordinary high strength): Compared to Preparation Example 1, the mix proportions were adjusted as follows: 550 kg of cement, 100 kg of silica fume, using a common water-reducing agent, and a water-cement ratio of 0.28. The 28-day strength was approximately 90 MPa, and the porosity was high.

[0038] Example 4. External rebar installation and casting method: To simultaneously enhance the sealing and strength of the pontoon, the following steps are added to the modular collaborative casting method of Example 1: S5. On-site casting of the outer surface: In the splicing of S2 and assembly of S3, some flange holes are reserved on the outside of the cylindrical assembly 3 and the conical assembly 2. Basalt fiber straight bars are inserted into the flange holes and basalt fiber arc bars are tied. Ultra-high strength concrete is poured and sealed section by section. Ordinary curing for 5-10 days forms a reinforced pontoon with an encapsulated outer surface to avoid corrosion of the exposed steel structure.

[0039] The ultra-high strength concrete was selected from preparation examples 1-3 and comparative preparation examples 1-2, and its performance was tested to select the most suitable formula for the pontoon, as shown in Table 1 below: Table 1: Performance Tests of Ultra-High Strength Concrete Formulations Suitable for Offshore Floating Bodies Test method description: Compressive strength: tested according to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete".

[0040] Chloride ion diffusion coefficient: Tested using the RCM (rapid chloride ion migration) method. The lower the value, the stronger the impermeability.

[0041] Impact resistance: The number of impacts at the initial crack and failure of the specimen was recorded by drop hammer impact test.

[0042] Corrosion resistance: The corrosion current density of the built-in steel bars in a simulated seawater environment was measured using an electrochemical workstation. The lower the value, the stronger the corrosion resistance.

[0043] As shown in Table 1, the silica fume-mineral powder composite material used in Preparation Example 1 has top-level strength and impermeability, providing the best guarantee for the main load-bearing structure and long-term sealing of the pontoon, making it the first choice when pursuing extreme performance.

[0044] Preparation Example 2 employs an economical high-blending formulation, reducing material costs with minimal sacrifice in strength and impermeability. This is suitable for large-scale application in cost-sensitive but still durable pontoon bodies.

[0045] Example 3 uses a high-toughness, impact-resistant material that maintains excellent strength and impermeability while exhibiting outstanding toughness. It is specifically designed for areas near the waterline of the pontoon, such as collision protection zones, where it may be subjected to waves, ice floes, or ship impacts.

[0046] Compared to Example 1, which lacks nanomaterials and fibers, the strength is insufficient, the impermeability is poor, and the reinforcing steel is extremely susceptible to corrosion. It completely fails to meet the structural safety and durability requirements of offshore pontoons.

[0047] In contrast, Example 2, a conventional high-strength concrete with a high water-cement ratio, while still a high-strength concrete, exhibits significantly lower impermeability and durability compared to Example 1. In harsh marine environments, its service life is limited, posing substantial maintenance risks and resulting in poor overall life-cycle economics.

[0048] Therefore, the formulation of Preparation Example 1 was used as the baseline formulation for Example 4 and compared with Examples 1-3.

[0049] Application example: A floating offshore wind power platform manufactured using any of the pontoons in Examples 1-4 includes at least three pontoons or reinforced pontoons, wherein the pontoons or reinforced pontoons are arranged in an equilateral triangle and connected as a whole by a steel-concrete composite top support structure, such as... Figure 5 As shown, its preparation may include the following steps: 1. Docking Phase: The supporting platform is hoisted to the top transition section of the pontoon using a floating crane. The flange alignment accuracy is adjusted (axial deviation ≤3mm, horizontal error ≤2mm / m). High-strength anti-corrosion bolts (diameter ≥36mm, evenly distributed circumferentially, spacing 150-200mm) are inserted. A three-step tightening method (initial tightening → secondary tightening → final tightening) is used. The pre-tightening force is double-calibrated using a torque wrench and axial force gauge to ensure uniform force distribution. Adjacent module flanges are aligned, sealed with rubber anti-corrosion gaskets to prevent leakage, and tightened with high-strength anti-corrosion bolts. The bolts are equipped with lock nuts to adapt to marine vibration conditions. Marine-grade epoxy putty is injected into the flange gaps for secondary sealing to prevent seawater infiltration.

[0050] 2. Reinforcement Stage: Truss connecting frames are used to reinforce the pontoons with each other and with the central support. These frames are constructed using steel-concrete composite. Every 3-5 meters along the outer surface of each pontoon, a rubber ring or lightweight, high-strength thermoplastic material (recycled waste rubber or polyurethane thermoplastic material can be used) with a width of at least 160mm and a thickness of at least 200mm is installed at each midpoint. This unique anti-collision device significantly protects against general impacts and enhances the effective collision protection of the concrete floating pontoons.

[0051] 3. The truss connecting frame is a spatial load-bearing system, consisting of an upper layer, a lower layer, and an intermediate support structure, ensuring that the load is evenly distributed across the three pontoons: Upper Truss: Located near the top of the pontoon's supporting platform, it is welded or bolted to the steel components at the bottom of the platform. It primarily bears the vertical and horizontal wind loads transmitted by the wind turbine tower, preventing localized stress concentration. A steel-concrete composite support system is used, with multiple triangular structures formed between the support's interior and the center of the tower connection section to maintain the stability of the supporting platform and the wind turbine tower.

[0052] Lower Truss: Located near the bottom of the pontoons and parallel to the sea level, it uses steel-concrete composite supports. The internal structure of the supports forms multiple triangles with the center of the tower connection section, utilizing the stability of triangles. Steel-concrete composite connecting beams are used to stably connect the triangular pontoons, primarily resisting the horizontal impact and torque from waves, and enhancing in-plane deformation resistance.

[0053] Intermediate support: Cross bracing is set between the pontoons and the central support to form a three-dimensional force network, which vertically transfers the upper load to the lower truss and then distributes it to the three pontoon nodes.

[0054] Final performance comparison test plan and expected results of the pontoons The following is a systematic test design and an analysis of expected results based on the technical principles.

[0055] Table 2: Final Performance Test Design for the Float According to Table 2, tests were conducted using the float product of Example 1 as a benchmark, and the results are shown in Table 3 below: Table 3: Comparison and Analysis of Expected Test Results of the Floats in Examples 1-4 As shown in Table 3, Example 4, due to its integral molding, exhibits the highest load-bearing capacity and a superior failure mode, fully utilizing the material's strength. The limited improvement in Example 3 indicates that the seamless integral structure of Example 4 possesses an overwhelming advantage in fatigue resistance, which is crucial for achieving a long service life.

[0056] Example 2 is an effective repair solution, but its reliability depends on construction quality and material aging. Example 4, however, uses the ultra-high-strength concrete from Example 1 for integral encapsulation, achieving perfect watertightness. The extremely low permeability of the ultra-high-strength concrete provides long-term protection for the internal structure (including any encapsulated steel components). The joints of other solutions are rapid pathways for corrosion. Example 4 completely solves the corrosion problem through physical isolation, minimizing performance degradation. Other solutions suffer severe deterioration due to exposed or insufficiently protected steel.

[0057] In summary, Example 4, using the ultra-high-strength concrete integral encapsulation of Example 1, demonstrates a significant leading advantage in all core dimensions, including structural integrity, watertightness, fatigue resistance, and corrosion resistance. It transforms the pontoon from an assembly consisting of weak links (bolted joints) into a homogeneous, highly reliable integral structure.

[0058] Examples 2 and 3 represent repair approaches, addressing the shortcomings in sealing and structure respectively, but they cannot fundamentally solve the other shortcoming and the problem of steel corrosion.

[0059] Example 4 is a redesign approach that solves all fundamental problems in a one-time, systematic way through material and construction method innovation. Although Example 4 has the highest initial construction cost and difficulty, its near-maintenance-free characteristics, ultra-long fatigue life, and excellent durability mean that over its 50-100 year design life, the total cost of ownership will be far lower than that of Examples 1-3, which require regular maintenance, component replacement, and may suffer significant losses due to failure.

[0060] For projects that prioritize superior reliability and extended design life (such as deep-sea wind power platforms), Example 4 should be selected as the core solution without hesitation. Within the framework of Example 4, materials can be optimized according to the function of each part: the main structure uses the formulation of Preparation Example 1, while impact-prone parts such as the anti-collision zone can use the high-impact formulation of Preparation Example 3.

[0061] Example 2 can serve as a reference for sealing and reinforcing existing structures when budget or construction conditions are strictly limited, but it is not recommended for the construction of new critical permanent facilities.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms, characterized in that... Includes the following steps: S1. Preparation of prefabricated modules: S1-1, Preparation of steel mold: An arc-shaped steel mold is formed by welding two rectangular flanges (101) and two fan-shaped flanges (102). The outer surface of the rectangular flange (101) is provided with equidistant straight raised strips (101A), and the outer surface of the fan-shaped flange (102) is provided with equidistant arc-shaped raised strips (102A). The edges of the rectangular flange (101) and the fan-shaped flange (102) are respectively provided with flange holes. S1-2, Binding basalt fiber reinforcement: Arrange arc-shaped basalt reinforcements (103A) and straight basalt reinforcements (103B) inside the arc-shaped steel mold, and bind them with wire or straps to form a fiber grid parallel to the opening surface of the arc-shaped steel mold. Arrange 2-4 sets of fiber grids with different diameters and equal spacing according to the thickness requirements. S1-3, Casting and molding of prefabricated modules: Arrange arc-shaped templates on the two opening faces of the arc-shaped steel mold to form an arc-shaped casting cavity. Reserve the casting port and make the flange hole outside the arc-shaped casting cavity. Use the bottom injection of high-performance concrete, high-frequency vibration to vent air, and ordinary curing for 5-10 days to obtain the precast module (1) composed of the casting body (103) and the arc-shaped steel mold. S2. Classification and assembly of prefabricated modules: When the two sector flanges (102) have the same diameter, a prefabricated module (1) with the same upper and lower sector end plane dimensions is produced. After being fastened with screws, it is spliced ​​on the ground or ship hull to form a cylindrical assembly (3). When the diameters of the two sector flanges (102) are different, prefabricated modules (1) with different upper and lower sector end plane dimensions are produced. They are fastened with screws and spliced ​​on the ground or ship hull to form a conical assembly (2). S3. On-site assembly of pontoons: By using a hoisting method, the upper and lower end faces of the cylindrical assembly (3) are connected to the conical assembly (2) by screws to obtain the pontoon.

2. The modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms according to claim 1, characterized in that, The high-performance concrete in S1-3 is C60-C100 concrete.

3. The modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms according to claim 1, characterized in that, In S2, the straight protrusions (101A) of adjacent prefabricated modules (1) have different thicknesses and are misaligned, so that the adjacent straight protrusions (101A) of the prefabricated module (1) form a groove for engaging the straight protrusion (101A) of another prefabricated module (1), and a water-stop strip (101B) is provided between the straight protrusion (101A) and the groove; the arc protrusions (102A) of adjacent prefabricated modules (1) have different thicknesses and are misaligned, so that the adjacent arc protrusions (102A) of the prefabricated module (1) form a groove for engaging the arc protrusion (102A) of another prefabricated module (1), and a water-stop ring (102B) is provided between the arc protrusion (102A) and the groove.

4. The modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms according to claim 1, characterized in that, It also includes the following steps: S4. Joint Sealing Enhancement: First, pressure inject non-shrink epoxy grout into the flange gap; then fill the pre-reserved groove on the outside of the joint with polyurethane water-swellable sealant; finally, use a three-layer cloth and five-layer oil manual lamination process to form a fiberglass protective cover with a thickness of not less than 5mm on the outside of the sealant using vinyl ester resin and alkali-free glass fiber cloth.

5. The modular co-casting method for basalt fiber reinforced cages and steel structures on offshore platforms according to claim 1, characterized in that, In the splicing of S2 and the assembly of S3, some flange holes are reserved inside the cylindrical assembly (3) and the conical assembly (2), basalt fiber straight bars are inserted into the flange holes, and basalt fiber arc bars are tied.

6. The modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms according to claim 1, characterized in that, It also includes the following steps: S5. On-site casting of the outer surface: In the splicing of S2 and the assembly of S3, some flange holes are reserved on the outside of the cylindrical assembly (3) and the conical assembly (2). Basalt fiber straight bars are inserted into the flange holes and basalt fiber arc bars are tied. Ultra-high strength concrete is poured and sealed section by section. Ordinary curing for 5-10 days forms a reinforced pontoon with an outer surface encapsulation to avoid corrosion of exposed steel structure.

7. The modular collaborative casting method for basalt fiber reinforced cages and steel structures on offshore platforms according to claim 6, characterized in that, The ultra-high strength concrete is C160-C180 concrete, and its formula per cubic meter includes: 620-650 kg of P·Ⅰ52.5R cement, 70-80 kg of silica fume, 30-40 kg of S115 grade ultrafine mineral powder, 20-30 kg of nano-activated calcium carbonate, 500-550 kg of basalt fine stone with a particle size of 0.8-2.0 mm, 560-600 kg of quartz sand with a particle size of 0.15-0.8 mm, 200-250 kg of ultrafine quartz sand, 25-30 kg of basalt fiber with a length of 6-12 mm, 2-3 kg of polypropylene coarse fiber with a length of 3-6 mm, 18-22 kg of polycarboxylate-based high-efficiency water-reducing agent, 3-5 kg ​​of composite rust inhibitor, and 130-150 kg of pretreated desalinated seawater, with a water-cement ratio of 0.16-0.

18.

8. A floating offshore wind power platform manufactured using the modular collaborative casting method described in any one of claims 1-7, characterized in that, It includes at least three pontoons or reinforced pontoons, which are arranged in an equilateral triangle and connected as a whole by a steel-concrete composite top support structure.

9. The offshore floating wind power platform according to claim 1, characterized in that, The middle section of the pontoon or reinforced pontoon is fitted with rubber rings or rubber rings made of lightweight and high-strength thermoplastic material with a width of not less than 160mm and a thickness of not less than 200mm every 3-5 meters.

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