External tendons for wind towers
VSL’s external tendons for wind towers offer a proven, durable, and versatile solution for both onshore and offshore towers. Specifically developed and backed by European Technical Approval (ETA), the E-WT system ensures structural stability, allows re-tensioning throughout the tower’s life, and simplifies installation logistics even in challenging environments.
Why choose VSL E-WT system
- ETA-approved, custom-designed external tendons for concrete wind towers
- Optimized for tall, vibration-sensitive structures with high durability demands
- Allows re-stressing during construction or service life
- Full turnkey support: design, supply, prefabrication, and installation
Key features
Applications
VSL’s E‑WT system is used in:
- Onshore and offshore concrete wind towers
- Hybrid towers combining concrete bases and steel upper sections
- New construction and retrofitting of tall energy structures
- Projects requiring re-stressable, externally mounted tendon systems
Design and Performance
- Vertical multistrand tendons, typically with 18 strands per tendon
- Up to 12 external tendons per tower, installed in pre-defined positions
- GC or E‑WT anchorages: compact, high-capacity, corrosion-resistant
- Fully grouted within PE ducts, with grout vents and sealed anchor zones
- System accommodates tower vibration, dynamic wind loads, and harsh exposure
Accessories
- Custom lifting frames for bundled tendon installation
- Modular deviators and supports to match tower geometry
- Venting and sealing accessories for efficient grouting
- Optional Electrically Isolated Tendons (EIT) for added protection and future monitoring
End-to-End Services
- End-to-end delivery by VSL-certified teams
- Lightweight equipment eliminates need for tower-top cranes
- Tendons installed from base upward using guided winch systems
- Onsite stressing, grouting, and tension checks
- Solutions adapted for offshore tower access and sequencing
Smart External Tendons
VibraTrack, a VSL-patented system, enables real-time vibration and force monitoring of tendons under live loads. Operating inside the tendon’s protective envelope with a data acquisition system, VSL-developed software self-orients and calibrates the sensor, removing manual setup and ensuring accuracy.
Benefits:
- Full environmental protection
- Uninterrupted tendon behaviour
- Easy installation/replacement, offshore ready
Key benefits
- Structural stability: Controls tower deflections and dynamic response
- Flexible construction: Tendons installed after tower erection
- Long-term serviceability: Enables re-tensioning at any stage
- Streamlined logistics: Bundle lifting and compact anchorage reduce site constraints
- Marine adaptability: Engineered for offshore wind environments
Frequently asked questions about external tendons for wind towers
It is ETA-approved, designed for vertical external tendon installation, allows re-stressing, and is adapted for onshore and offshore conditions.
Typically 12 external tendons per tower, each with up to 18 strands of 0.6″ diameter.
Yes. The system is designed for re-tensioning during operation or at maintenance intervals.
Tendons are fully encapsulated and grouted, with corrosion-resistant anchorages and detailed sealing at every interface. EIT options are available.
Yes. VSL provides project-specific solutions for harsh marine environments, including proven installation methods and material configurations.