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Pulling rod is a key component of the pulling system in overhead power lines, communication lines, and broadcasting and television towers. It is mainly used to connect the pulling wire (steel strand) with the ground anchor (or underground foundation), transmit the unbalanced tension on the tower to the ground, stabilize the tower structure, and prevent tilting or collapse. The following is a detailed introduction about the pull rod:

1、 Material and specifications

1. Material

Mainstream materials:

Hot dip galvanized round steel (such as Q235 and Q345 steel) is used, with surface hot-dip galvanizing treatment (zinc layer thickness ≥ 65 μ m), good corrosion resistance (based on actual reports), and suitable for general soil environments.

Special Scene:

Stainless steel round steel or copper-clad steel round steel can be used in areas with high humidity and strong corrosion (such as coastal areas and near chemical plants).

Some scenes use cast iron wire rods, but due to their fragility, they are gradually being replaced by hot-dip galvanized round steel.

2. Specifications

Diameter: Common specifications include diameter 16mm, 18mm, 20mm, 22mm, 24mm, etc., depending on the tension of the cable (the larger the tension, the larger the diameter).

Length: usually 1.5m~3m, customized according to the burial scale (such as frozen soil layer thickness, soil bearing capacity), with a standard length of 2m.

End structure:

One end is processed into threads (with nuts and washers) for connecting wire fittings (such as UT clamps);

The other end is made in a ring or hook shape for easy fixation with anchor stones or concrete foundations.

2、 Function and principle

1. Core role

Transmission of tensile force: The horizontal load (such as wire tension and wind force) borne by the tower is transmitted to the ground through guy wires, balancing the force on the tower and preventing tilting.

Stable structure: As the "underground anchor point" of the cable system, it forms a stable force system together with the ground anchor, especially suitable for towers with high stress such as corner poles, terminal poles, and crossing poles.

2. Working principle

The pull rod bears the tension of the pull wire through its tensile strength, and its buried part forms frictional and gripping forces with the soil (or anchor), dispersing the tension into the surrounding soil layer.

Usually used in conjunction with cable reels (precast concrete slabs) to increase the contact area with the soil and improve the pull-out resistance.

3、 Characteristics

1. Advantages

Good strength: Round steel material has excellent tensile performance and can withstand large tensile forces (such as a tensile strength of over 20kN for a 20mm tension rod).

Easy installation: It can be directly buried in the soil and connected to the wire fittings through threads at a suitable speed, with good construction efficiency.

Good corrosion resistance (based on actual reports): The hot-dip galvanized layer has excellent resistance to soil corrosion and a service life of over 20 years.

Low cost: materials are readily available, processing technology is simple, and suitable for large-scale engineering applications.

2. Disadvantages

Long term tensile stress may cause plastic deformation, and regular inspections are needed to check for rust, cracks, or deformation.

Soil settlement or corrosion may cause the tension rod to loosen, and it is necessary to cooperate with the tension reel to enhance stability.

4、 Application scenarios

power engineering

Wire fixation for corner poles, terminal poles, and tension rods of overhead transmission lines and distribution lines.

Substation architecture, windproof cables or temporary cables for iron towers.

Communication and Broadcasting Engineering

The cable wind ropes (guy wires) of communication towers and broadcasting and television transmission towers are grounded and fixed.

Stability reinforcement of microwave towers and base station towers.

Other industries

Cable fixation of railway overhead contact line pillars.

Wind resistant anchor points for high-rise structures such as billboards and streetlight poles.

5、 Installation points

1. Construction process

Positioning and excavation

According to the design requirements, determine the burial position of the tension rod and excavate a trapezoidal pit (wider at the top and narrower at the bottom) with a scale generally ≥ 1.5m (exceeding the frozen soil layer, such as ≥ 2m in northern regions).

Place a cable reel at the bottom of the pit, with the center of the reel aligned with the direction of the cable rod, and confirm that the force is evenly distributed.

Install the cable rod

Connect the end of the cable rod with a loop (or hook) to the lifting ring of the cable reel with bolts, or directly embed it into the concrete foundation.

The cable rod is perpendicular to the cable reel, maintaining the same direction as the cable to avoid bending moments under stress.

Backfilling and compaction

Fill with fine soil layer by layer, with a thickness of about 200mm per layer. After compaction, fill the next layer to avoid backfilling with stones, tree roots, and other debris.

The backfill soil should be raised 100-200mm above the ground to form an anti settling soil pile to prevent rainwater erosion from causing settlement of the pit.

Connect the cable

The above ground part is connected to the wire (steel strand) through UT clamps or wedge clamps, and the threaded end needs to be equipped with spring washers and double nuts to prevent loosening.

2. Key technical requirements

Tensile strength matching: The diameter of the wire rod needs to match the tension of the wire, for example:

Ordinary distribution line cables (tension ≤ 10kN) can be selected with a diameter of 16~18mm;

High voltage transmission lines or large span guy wires (tension ≥ 20kN) should be selected with a diameter of 20~24mm.

Anti corrosion treatment (based on actual reports):

The welding area (if any) needs to remove welding slag and apply anti rust paint and asphalt paint for corrosion prevention (based on actual reports).

The exposed threaded part needs to be coated with butter or wrapped in plastic cloth to prevent rust and make it difficult to disassemble.

Tensile testing: After installation, the tensioning system should be pre tightened and the tensile force should be tested using a force gauge to ensure it meets the design requirements (usually 60% to 70% of the rated tensile force).