Bridge (Cable Tray) is an open or closed structural system used to support and protect cables, wires or pipes, which is widely used in construction, electric power, communication, industry and other fields. Its emergence is closely related to the development of electric power and communication industry, the following is the origin of the bridge and its development history:

1. Early cable laying method (19th century)

In the early development of the power system (late 19th century to early 20th century), cables are usually laid in the following ways:

Direct burial underground: cable buried underground, but prone to moisture, corrosion, and maintenance difficulties.

Wooden or metal wire channels: simple wooden or iron channels were used to protect the cables, but the structure was simple and had limited load-bearing capacity.

Pipe laying: Metal or ceramic pipes are used to protect cables, but construction is complicated and costly.

With the growth of power demand, the traditional laying method has been unable to meet the demand for large-capacity, multi-loop cable management, the bridge came into being.

2. The prototype of bridge (early 20th century)

Driven by Industrial Revolution: At the beginning of the 20th century, factories, power stations, etc. required a large number of cables, giving rise to more efficient cable management solutions.

Open Metal Bracket: Initially, angles and channels were welded into simple brackets to support cables, but lacked standardised design.

The emergence of ladder bridge: In the 1930s, the United States and other countries began to use ladder bridge (Ladder Cable Tray), its structure is similar to a ladder, easy to dissipate heat and maintenance.

3. Standardisation and diversification (mid to late 20th century)

Material Improvement: From steel to galvanised steel, aluminium alloy, stainless steel and glass reinforced plastic (FRP) to improve corrosion resistance and light weight.

Structural innovations:

Tray type bridge (Solid Bottom Tray): closed design, dust and splash proof, suitable for chemical and food industries.

Channel Cable Tray: Fully enclosed structure, shielded from electromagnetic interference, used in data centres or precision instruments.

Wire Mesh Tray: open grid design, light weight, good ventilation, common in European standards.

International standard development: such as the United States NEMA (National Electrical Manufacturers Association) issued a bridge standard (NEMA VE 1), specification size, load and other parameters. 4.

4. Application of modern bridge (21st century)

Intelligent and modular: bridge systems are combined with BIM (Building Information Modelling) for accurate design and fast installation.

Fire prevention and environmental protection requirements: fire-resistant bridges (e.g. sprayed fireproof coatings) and low-smoke, halogen-free materials are widely used to comply with building safety codes.

Emerging field demand: data centre, 5G base station, new energy (photovoltaic, wind power), etc. push the bridge to develop in the direction of high-strength and high-density wiring.

5. Development of bridge rack in China

Introduced in 1980s: With the reform and opening up, foreign bridge technology was introduced into China, gradually replacing the traditional cable laying method.

Localised production: After the 1990s, domestic enterprises (e.g. Jiangsu, Zhejiang, etc.) began to produce on a large scale and set national standards (e.g. GB/T 21762-2008).

Innovative applications: high-speed rail, underground, intelligent buildings and other projects to promote bridge technology upgrades, such as seismic bridge, corrosion-resistant bridge.