How to Calculate the Load of Galvanized Cable Trays

2026-03-25
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The core of calculating the load on a galvanized cable tray is to accurately calculate the total weight of the cables and ensure that this total load does not exceed the allowable load capacity of the cable tray. Below is the polished calculation method and key technical points:

1. Total Load Calculation Formula

The total load of the cable tray refers to the total weight of all cables laid within it, calculated as the uniformly distributed load per unit length.

Calculation Formula:

G_total = n₁q₁ + n₂q₂ + ... + n_Nq_N

G_total: Total load per unit length of the cable tray (kg/m)
q₁, q₂...q_N: Unit weight of each type of cable (kg/m)
n₁, n₂...n_N: Quantity of each corresponding type of cable

Key Requirement:

G_total < G_allowable

The total load must be less than the allowable load rating of the cable tray, which shall be verified against the load-span curve provided by the manufacturer.

2. Additional Loads to Be Considered

In practical engineering, other loads must also be included in the calculation:

Outdoor Installation: Consider natural loads such as snow, ice accumulation, and wind pressure.
Construction & Maintenance: If the tray is used for pedestrian access, a live load of approximately 0.5–1.0 kN/m² (equivalent to 90kg per person) shall be applied.
Auxiliary Equipment: Include the weight of additional facilities such as sprinkler pipes, monitoring cables, and other fixtures mounted on the tray.

3. Cable Filling Ratio & Spare Capacity

To ensure heat dissipation, ventilation, and future expansion, the following ratios must be observed:

Power Cable Filling Ratio: 40%–50%
Control Cable Filling Ratio: 50%–70%
Expansion Margin: Reserve 10%–25% of internal space for future cable additions.

4. Deflection Control Standard

The deformation (deflection) of the cable tray under full load must meet safety specifications:

Under the designed support span, the maximum deflection shall not exceed L/200 (where L = support span length).

Example: For a 3m span, the maximum allowable deflection is 15mm.