A well proven SSI stay-cable system
VSL stay-cable systems include:
- Tensile element: it is the load carrying element;
- Anchoring component: it allows for the load transfer to the structure;
- Cable encapsulation: it is the interface to environment and user;
- Protection at deck location, against vandalism, fire, blast;
- Transition device, for vibration and deviation load control.
The VSL SSI 2000 is VSL’s well-proven and widely used state-of-the-art stay cable system. It meets the highest standards of fatigue performance and provides a high degree of corrosion protection.
The SSI 2000 also exists in a compact version to limit wind exposure: the SSI 2000C is a compact stay cable system with a reduced cable diameter that greatly reduces wind drag.
Why use SSI technology instead of PWS?
VSL uses SSI technology, meaning ‘strand by strand installation’: the light weight of the equipment – and the cables in particular – allows for extreme ease and flexibility of installation compared to systems with parallel wire strands (PWS).
SSI also allows for easy replacement of components throughout the entire lifecycle of the structure, without the need to dismantle the anchorages or the rest of the cable.
Main tensile elements of stay cable system
VSL has developed three types of tensile elements, catering for different needs but all based on its state-of-the-art VSL SSI 2000 stay-cable system. These are:
- SSI 2000 for application in accordance with fib or CIP standards;
- SSI 2000 for application to PTI standards
- SSI 2000D for application where dehumidification is required. SSI 2000D, which meets fib standards, is the world’s most compact stay-cable strand with corrosion protection that can be monitored. The permanent dehumidification system provides a controlled environment, which not only protects the steel strands from corrosion, but also makes monitoring and inspection extremely easy.
The anchorage area is where cables come under the most stress. The anchorage must:
- always remain leak-tight;
- be resistant to deviation in order to limit the aggressive stress placed on the cables at the anchors’ locations.
VSL has developed a wide portfolio of solutions and provides an abundance of design flexibility:
- SSI 2000e DR and SSI 2000e DS have no limitations in their application: they are suitable for long-span cable-stayed structures. They provide high fatigue performance. In situations where one or more strands need replacement, the VSL SSI 2000e anchorage allows the sealant system to be replaced strand by strand.
- SSI 2000 DRm and SSI 2000 DSm are stressing anchorages and use HDPE sheathing to prevent penetration at the wedge zone.
- MSI 2000e DR and MSI 2000e DS are designed to handle loads in slender structures: they have been specifically engineered for the hangers of arch bridges and the stays of suspended roofs.
- SSI 2000d DR and SSI 2000d DS are cost-effective solutions for structures already protected by dehumidification.
- SSI Saddle, which has a minimum radius of 1.5m and no limitation on angles, is able to withstand differential forces at either side of a pylon thanks to friction between the strands and the saddle. This solution has the advantage of dramatically simplifying the pylon detailing and construction.
Specific solutions for cable protection
VSL has developed stay pipe profiles and specific solutions to help control vibration, mitigate risks from the accumulation of snow and ice and protect against fire. They can even be equipped with a network of LEDs to turn bridges into visually iconic displays.
VSL has developed a portfolio of four transition components that allow for control of loads arising from vibration and deviation:
- Tension rings compress the strand bundle; they are the default solution for top anchor points;
- Guide deviators compress and guide the strand bundle; they are required to avoid clashes between strands and guide pipes;
- High-damping rubber dampers provide stay-cable damping; they are used for the dynamic stability of medium to long cables;
- Friction dampers provide a high degree of damping for long cables subjected to severe environments.