Steel strand and rebar tensioning jack: types, characteristics, and choice

A steel strand and rebar tension jack is a device that is used to create tension in steel bars, wire or steel strands. It is used in the manufacture of reinforced concrete structures such as beams and slabs to ensure the strength and stability of the structure.

Working principle

The steel strands or rebar tensioning hydraulic jack works on the basis principle of hydraulic cylinder. The cylinder of the jack contains a liquid which moves the piston under pressure. The piston, in turn, transfers this pressure to the jack’s working element, which creates tension in the steel strands or rebar.

Types of jacks

Jacks for tensioning steel strands and rebar are divided into two main types: mechanical and hydraulic.

• Mechanical jacks work by using a screw or lever. They have low power and are mainly used for small jobs.
• Hydraulic jacks work by using a hydraulic system. They have a higher capacity and are used for larger jobs.

Technical characteristics

The technical specifications of the Steel Strand and Rebar Tensioning Jack are determined by the following parameters:

• The tensioning force is the maximum force that the jack can generate. It is measured in kilonewtons (kN).
• Working stroke is the distance the jack’s stem can move. It is measured in millimetres (mm).
• Dimensions are the dimensions of the jack that must be taken into account when selecting the jack.

Safety

When using jacks for pulling steel strands and rebar, the following safety rules must be observed:

• Operate only a jack that is in good working condition.
• Ensure that the jack is securely fastened.
• Do not exceed the permissible load on the jack.
• Wear safety goggles when working with hydraulic jacks.

Types of rebar tensioning

There are two main types of rebar tensioning used in the construction of reinforced concrete structures:

• Pre-tensioning is the tensioning of rebar that is performed before concrete is poured.
• Post-tensioning is the tensioning of the reinforcement that is performed after the concrete has been poured.

Pre-tensioning of reinforcement

Rebar pre-tensioning is the most common method. It ensures higher strength and stability of reinforced concrete structures.
Special jacks called rebar tensioners are used for prestressing reinforcement. Rebar tensioners can be mechanical or hydraulic.

Post-tensioning of the reinforcement

Post-tensioning is used when pre-tensioning is not possible. It provides lower strength and stability of reinforced concrete structures than pre-tensioning.

In the post-tensioning of the reinforcement, special anchors are used, which are fixed in the concrete. The reinforcement is attached to the anchors using special fixtures. The reinforcement is tensioned using hydraulic jacks.

Selecting a jack for rebar tensioning

The following factors should be considered when selecting a rebar tensioning jack:

• Type of rebar tensioning.
• Rebar tensioning force.
• Working stroke of the jack.
• Overall dimensions of the jack.

For pre-tensioning of the reinforcement it is necessary to use jacks with high capacity. For subsequent tensioning of the reinforcement, jacks with lower capacity can be used.
The working stroke of the jack must be sufficient to ensure the required tensioning of the reinforcement. The overall dimensions of the jack must be suitable for the working conditions.
The jack for tensioning steel strands and reinforcement is an important tool used in the construction of reinforced concrete structures. When selecting a jack, its technical characteristics and safety rules should be taken into account.