Connection method between cable tray and seismic bracing

Cable trays are connected to seismic bracing using either rigid or cable bracing systems, typically employing clamps, rods, and pre-engineered attachment kits designed to meet seismic codes.

Types of Seismic Bracing

1. Rigid Bracing: Rigid braces resist both tension and compression and are installed at each brace location. They are suitable for shorter drop lengths and provide strong lateral and longitudinal support for cable trays during seismic events . 2. Cable Bracing: Cable bracing works in tension and requires two opposing brace assemblies at each location. It is ideal for longer drop lengths or where vibration isolation is needed. Cable bracing kits, such as Eaton's B-Line series with KwikWire clamps, allow tool-less installation and are pre-tested for seismic compliance .

Connection Hardware and Methods

• Hold-Down Clamps and Guides: Cable trays are secured to the bracing system using hold-down clamps that prevent vertical and lateral movement .
• Strut Channels and Hanger Rods: B22 strut channels can be connected to hanger rods (3/8-16 to 7/8-9") using seismic cable kits. The prestretched aircraft cables wrap around structural members without drilling, simplifying installation .
• Bolted Connections: Proprietary steel members or braces are often bolted to the cable tray and structural supports to provide diagonal lateral bracing, especially in multi-tiered tray systems .
• Rod Stiffeners: Rods are used to stiffen the system and maintain alignment under seismic loads .

Design Considerations

• Lateral and Longitudinal Bracing: Braces must be installed both perpendicular and parallel to the cable tray to resist seismic forces .
• Load Assessment: The weight of cables, including potential future expansion, must be considered to ensure the bracing system can handle maximum anticipated loads .
• Compliance with Codes: Systems should meet IBC, ASCE 7, NFPA 13, and local seismic design requirements. Pre-engineered kits often come with PE-stamped drawings for compliance .
• Installation Efficiency: Tool-less clamps and pre-cut cable kits can reduce installation time by up to 50% compared to traditional methods .

Summary

The connection between cable trays and seismic bracing involves secure attachment using clamps, rods, and braces, with the choice of rigid or cable bracing depending on drop length, load, and vibration requirements. Pre-engineered seismic bracing kits, such as Eaton's B-Line series, provide tested, code-compliant solutions that simplify installation while ensuring structural integrity during seismic events .