Steel Cable Trusses – Uses, Pros & Cons

What are Steel Cable Trusses?

Steel cable trusses are a structural support system that uses high-strength steel cables to form a lattice or triangular pattern, supporting various structures. They are commonly used in bridges, stadiums, and other large buildings that require long spans without intermediate support columns.

San Ysidro Border Crossing Secondary Canopy
Fig 1: San Ysidro Border Crossing Secondary Canopy

With advancements in technology and engineering, steel cable trusses continue to evolve and improve, offering even greater strength and efficiency for a wide range of applications. As a result, steel cable trusses have become an essential component of modern infrastructure, providing stability and support to some of the world’s most impressive structures.

Advantages of Steel Cable Trusses

One of the main advantages of steel cable trusses is their strength-to-weight ratio. Steel cables are incredibly strong for their weight, so they can support large loads without adding excessive weight to the structure. This makes them an excellent choice for designs that need to be lightweight, such as long-span bridges or roofs.

Another advantage of steel cable trusses is their flexibility. The cables can be tensioned to precise levels, which allows the truss to flex and move with changing loads and environmental conditions. This makes them particularly useful in areas with high winds or seismic activity, as the truss can absorb and distribute the forces of these events.

Steel cable trusses also offer aesthetic benefits. The open lattice structure allows natural light to pass through, creating a sense of openness and transparency. This can be particularly useful in buildings that require a sense of grandeur, such as sports stadiums or convention centers.

When designing a steel cable truss, there are several factors to consider. The size and shape of the truss must be carefully calculated to ensure that it can support the desired load without excessive deflection or deformation. The cables must be made from high-quality steel and installed with precise tension levels to ensure maximum strength and stability.

Cables Used In The Trusses

Cables are composed of a series of individual wires. The individual wires are twisted together to form strands, which are then twisted together in the opposite direction to form the cable. This twisting process gives the cable its strength and flexibility, allowing it to withstand high loads and changing environmental conditions.

Parallel Lay Strand
Fig 2: Parallel Lay Strand

Despite their strength, steel cables can be prone to corrosion over time. To combat this, cables are often coated in a protective layer of zinc or other materials to prevent rust and degradation.

Facts About The Cables:

  • Cables carry only tension forces
  • Cables tend to elongate under loads
  • Cable stiffness or resistance to bending forces is not the main design criteria
  • Cables can transfer only axial forces. Lateral forces are resisted by cable deformation, and they need to be resisted on supports
  • Cables can be fabricated to almost any length but are limited by the pre-stretching ability
  • Cables can be fabricated within the smallest tolerances
  • Cables can be used in complex structural buildings covering large spans with minimal dead weight

Drawbacks Of The Steel Cable Trusses

While steel cable trusses offer many benefits, they also have some potential drawbacks that should be considered before choosing this type of support system for a building or structure. Here are a few of the most notable disadvantages:

  • Cost: Steel cable trusses can be more expensive to manufacture and install than other support systems. The high price is due to the complex design and materials required to create strong, flexible cables.
  • Maintenance: Steel cable trusses require regular maintenance to ensure the cables remain taut and adequately tensioned. Any damage or corrosion to the cables can compromise the stability of the entire structure.
  • Fire resistance: Steel cable trusses can be vulnerable to fire, as high-strength steel cables can quickly lose their strength and fail at high temperatures. This can be a significant safety concern, particularly in buildings where fire safety is a top priority.
  • Corrosion: Steel cable trusses are vulnerable to corrosion if they are not properly protected, which can compromise the strength and stability of the cables. Proper coatings and maintenance are necessary to prevent corrosion.
  • Engineering complexity: The design and engineering of steel cable trusses can be complex, requiring specialized expertise and software to ensure the structure is safe and stable. This can add to the cost and time needed for the project.

Closing Thoughts

Steel cable trusses are versatile and efficient structural support systems that can be used in various applications. They offer strength, flexibility, and aesthetic benefits and are particularly useful in long-span structures where weight and flexibility are critical factors. If you’re considering a steel cable truss for your next project, be sure to work with a qualified engineer to ensure that your design is safe and effective.

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