1. Early Cable Support Methods (19th Century - Early 20th Century) 

Wooden and Metal Troughs: In the early years of power system development, cables were often laid directly underground or inside walls, or protected using simple wooden or metal troughs.

Open steel trays: as the industrial revolution advanced, factories and large buildings began to use steel trays (similar to ladders) to carry cables, but lacked standardised design.

2. The Rise of the Modern Tray (1920s-1950s) 

The Rise of the Steel Cable Tray: As power systems became more complex and engineers began to design more systematic cable support solutions, steel trays (e.g., ladder and trough) were gradually used in factories, power plants, and large buildings.

The need for standardisation: The National Electrical Manufacturers Association (NEMA) began to develop bridge standards in the mid-20th century, such as NEMA VE 1 (Standard for Metal Cable Bridges).

3. Diversification of Bridge Trays (1960s-1990s) 

Material Improvement: In addition to the traditional steel bridge trays, materials such as aluminium alloy and glass fiber reinforced plastic (FRP) began to be applied to adapt to different environments (e.g., corrosive places such as chemical, marine, etc.).

Structural innovations: 

Ladder Cable Tray: open structure, suitable for large diameter cables.

Trough Cable Tray: closed design for better cable protection.

Wire Mesh Cable Tray: lightweight and well ventilated, suitable for data centres.

International standard promotion: IEC, BS (British Standard), GB (Chinese National Standard) and so on have introduced bridge specification one after another.

4. Modern bridge technology (21st century to present) 

Intelligent and modular: modern bridge design pays more attention to flexibility, such as modular bridge that can be quickly disassembled to adapt to the needs of data centres, 5G base stations, etc.

Fire prevention and safety standards: With the improvement of building safety requirements, fire retardant and fire-resistant bridges (e.g. fire-coated steel bridges) have become the mainstream.

Environmental protection and lightweight: aluminium alloy and composite material bridge is widely used in green building due to its light weight, corrosion resistance and recyclability.

Main types of bridge (by structure) 

Type characteristics Typical applications 

Ladder bridge Open type, good ventilation and heat dissipation Power cable, industrial plant 

Trough bridge Closed type, dustproof and anti-interference Data centre, office building 

Grid-type bridge Lightweight and flexible, fast installation Data centre, communication room 

Tray bridge Between ladder and trough Comprehensive cabling, factory power distribution 

Future trends 

Intelligent monitoring: integrated sensors, real-time monitoring of Intelligent monitoring: integrated sensors, real-time monitoring of cable temperature, load and other data.

Higher fire rating: adapted to special environments such as high-rise buildings and nuclear power.

3D printed bridges: customised production and reduced installation time.

The development of bridges reflects advances in power, building and industrial technologies, from simple cable support to intelligent management systems, which will continue to be optimised to meet new demands in the future.