21.80mm 2230MPa Low Relaxation Prestressed Steel Strand – High-Capacity Solution for Mega Infrastructure Projects
Engineered for the most demanding structural applications, this ultra-high-strength prestressed steel strand delivers exceptional load-bearing capacity and long-term durability. With a nominal diameter of 21.80mm, it features a 19-wire multi-layer structure (1+9+9 configuration), offering a cross-sectional area of approximately 365mm² and a theoretical weight of 2.86kg per meter. Designed to meet or exceed international standards such as GB/T 5224-2014, this strand boasts a tensile strength of 2230MPa—making it ideal for heavy-duty civil engineering projects where reliability, efficiency, and longevity are paramount.
Key characteristics include an outstanding breaking force of ≥810kN, which is more than double that of conventional 15.20mm strands, and a low relaxation rate of ≤1.5% after 1000 hours at 70% of its nominal stress—a performance that reduces stress loss by up to 80% compared to standard alternatives. Its elastic modulus ranges from 195–200GPa, while elongation exceeds 3.5%, ensuring excellent ductility under high tension. These properties make it particularly suitable for structures requiring minimal maintenance over extended service lives, often exceeding 50 years.
Manufactured using precision twisting techniques, the strand's internal geometry optimizes density and torsional resistance. The central wire is slightly thicker than outer wires (e.g., 3.0mm vs. 2.8mm), with twist pitches set between 10–14 times the wire diameter. Surface treatments vary based on environmental demands: smooth finish, zinc-aluminum alloy coating (≥400g/m²), epoxy resin (≥0.5mm thickness), or HDPE sheathing for marine, chemical, or corrosive environments. This flexibility allows seamless integration into coastal infrastructure, offshore wind farms, and nuclear containment systems.
This advanced material excels in large-scale applications including suspension bridge main cables, deep foundation support in skyscrapers, offshore monopile anchoring for wind turbines, and high-pressure dam reinforcement. Compared to smaller-diameter options like 15.20mm strands, it significantly reduces the number of required tendons, simplifies anchor design, and lowers lifecycle costs—even though initial unit pricing may be 30–40% higher. In mega-span bridges (>1000m), the cost savings from fewer installations and reduced labor outweigh upfront investment.
Construction best practices involve hydraulic synchronous tensioning equipment capable of applying ≥1000kN per cylinder, with controlled elongation deviation within ±5%. Anchors must pass fatigue testing (no slippage after 2 million cycles), and surrounding concrete should achieve minimum compressive strength of C50 to prevent localized crushing. Post-installation monitoring via fiber-optic sensors ensures uniform stress distribution across the entire structure, while regular inspection of anchor seals prevents moisture ingress and corrosion.
Global engineers and contractors report improved project timelines, enhanced safety margins, and superior long-term performance when deploying this strand in critical infrastructure. It has become a preferred choice for ultra-long-span bridges, nuclear power plant containment systems, and offshore energy platforms due to its ability to maintain stress integrity under extreme conditions—including chloride exposure, cyclic loading, and sustained hydrostatic pressure.
Frequently asked questions include how this strand compares to traditional alternatives in terms of cost-effectiveness, whether it’s compatible with existing anchor systems, and what surface protection methods are recommended for harsh climates. The answer lies in its optimized design: fewer components mean less complexity, lower risk of failure, and faster installation—especially beneficial in remote or challenging terrains where access and logistics are limiting factors.
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