Longitudinal Seismic Bracing for Swedish Cable Trays

Longitudinal seismic bracing secures cable trays parallel to their run, preventing displacement during earthquakes and ensuring system stability.

Overview

Longitudinal seismic bracing is a critical component in cable tray systems, designed to resist movement along the length of the tray during seismic events. It complements transverse (lateral) bracing, which stabilizes the tray perpendicular to its run. Together, these braces ensure that both the cable tray and the cables it carries remain securely in place, reducing the risk of damage or dislodgement during vibrations or earthquakes (Eaton) .

Materials and Design

Seismic braces are typically made from high-strength metals, such as zinc-coated steel or wire rope/cable assemblies, which provide both tension and compression resistance. Modular components allow for prefabricated construction, easy disassembly, and modification without welding or drilling, making them suitable for complex installations (Gittewire) . Wire Rope/Cable™ bracing systems, for example, use pre-stretched cables that act like shock absorbers, dampening seismic loads and maintaining structural integrity (Legrand/Cablofil) .

Installation Guidelines

• Attachment Points: Longitudinal braces are installed parallel to the cable tray, connecting the tray to structural members using threaded rods, universal restraint clips (URC), or stake eye attachments (Legrand/Cablofil) .
• Spacing: Braces should be spaced according to tray length and load, typically every 30 feet for long runs (Legrand) .
• Components: A complete longitudinal bracing assembly includes the brace cable or rod, attachment hardware, and securing sleeves or clips to maintain tension and prevent slippage (Legrand/Cablofil) .
• Load Capacity: Braces are rated for specific breaking strengths, e.g., 900–6600 lbs, with safety factors applied to ensure compliance with seismic standards (Legrand/Cablofil) .

Compliance and Standards

While Sweden does not have a unique seismic code for cable trays, international standards such as the International Building Code (IBC), ASCE 7, and NFPA 13 provide guidance for seismic bracing design and installation (Eaton) . Products like Eaton TOLCO and UNISTRUT seismic bracing solutions are designed to meet these codes and can be adapted for Swedish projects (UNISTRUT, Eaton) .

Practical Considerations

• Customization: Braces can be customized with reinforcement ribs or different cable diameters to accommodate specific tray loads and configurations (Gittewire) .
• Prefabrication: Modular systems allow for rapid installation and minimal on-site labor, which is advantageous for large-scale or retrofit projects (Legrand/Cablofil) .
• Durability: High-strength metals and corrosion-resistant coatings ensure long-term performance, even in industrial or coastal environments.

Conclusion

For Swedish cable tray installations, longitudinal seismic bracing is essential for maintaining system integrity during seismic events. Using modular, high-strength bracing systems that comply with international standards ensures safety, reliability, and ease of installation. Proper spacing, attachment, and load rating are key to effective seismic protection.