Spacing of seismic bracing for cable trays in the Maldives

For seismic bracing of cable trays in high-seismicity regions like the Maldives, rigid trays should have supports spaced no more than 12 meters apart longitudinally, with lateral supports at both ends and at critical points such as turns, while flexible trays require roughly half these spacings.

Longitudinal Support Spacing

For rigid cable trays, the maximum spacing between seismic supports along the tray should not exceed 12 meters, while flexible trays should have supports spaced at no more than 6 meters to account for increased movement during seismic events. If the distance between supports exceeds these limits, additional mid-span supports are required to maintain stability and prevent tray deformation during an earthquake .

Lateral Bracing Requirements

Lateral supports are critical for stabilizing cable trays. They should be installed:

• At both ends of the tray
• Within 0.6 meters of any horizontal turns or bends
• At midpoints if the tray span is long or exceeds maximum support spacing
• Using gate-type braces that incorporate at least one lateral or two longitudinal supports to distribute seismic loads effectively .

Special Considerations

• Tray type selection: Ladder trays are preferred for primary distribution due to their structural stiffness, while perforated or trough trays require careful evaluation of support spacing and cable retention .
• Support attachment: Braces must be anchored to structural elements, not ceilings or partitions, to ensure proper load transfer .
• Parallel trays: Maintain a minimum horizontal spacing of 0.6 meters between trays at the same height to allow for seismic movement and maintenance access .
• Local adaptation: While Maldives-specific codes may not be explicitly defined, international seismic design standards (e.g., IEC, NEC, or local building codes) should be applied and adjusted for local seismic intensity and building structure.

Summary Recommendation

1. Rigid trays: longitudinal supports ≤12 m, lateral supports at ends, turns, and midpoints if needed.
2. Flexible trays: longitudinal supports ≤6 m, lateral supports at ends, turns, and midpoints.
3. Lateral braces: gate-type or diagonal braces at critical points.
4. Parallel trays: maintain ≥0.6 m spacing.
5. Anchorage: secure to structural members, not non-structural elements.

Following these guidelines ensures that cable tray systems in the Maldives are seismically resilient, minimizing the risk of damage and maintaining electrical system integrity during earthquakes .