Precautions for tensioning and construction of prestressed reinforcement

The tensioning of prestressed tendons must follow the relevant application technical specifications and strictly follow the pre prepared operating procedures.

The prestressed reinforcement shall be cut with grinding wheel instead of electric arc

When the steel strand is bundled, it shall be straightened out one by one and bundled into bundles without disorder. Extruded anchorage or embossing at the fixed end of steel strand

Type A anchorage shall be assembled with bearing plate and spiral reinforcement in advance.

The machines, equipment and instruments used for tensioning prestressed tendons shall be regularly maintained and calibrated.

Before the prestressed reinforcement is pulled, the concrete strength test report shall be provided. When the compressive strength of concrete meets the design requirements, and

The prestress can be applied only after it is not lower than the actual strength of the concrete in the anchorage zone during the specified tensioning construction.

Before tensioning the prestressed reinforcement, the bearing plate surface shall be cleaned and the concrete quality behind the bearing plate shall be checked. If there is concrete

The hollowing shall be repaired before tensioning.

During the installation of anchorage, the anchor plate shall be aligned, the working clip shall be tightened by tapping gently, and the position of the clip shall be uniform and the height shall be equal.

During tensioning, the prestressed reinforcement shall be loaded from zero to the initial tension at the starting point of elongation measurement, and then loaded to the required level

The tensioning force of.

Stress control and elongation check shall be adopted for tensioning management of prestressed reinforcement. Allowable deviation between actual elongation value and calculated elongation value

- 5%~+10%. If the value is exceeded, the tensioning shall be suspended, and the tensioning can be continued only after taking measures to adjust. Such as elongation value

Over tensioning measures can be taken if it is too small, but the tensioning force limit shall not be greater than 0.8f. In the multi wave curve prestressed reinforcement

The tensioning force at the high inner bearing can reduce the tensioning stress at the lower opening of the anchorage after tensioning, and the over tensioning return technology can be adopted.

The duct grouting shall be dense, and the strength grade of cement slurry shall not be lower than C30. The duct shall be wet and clean before grouting

It shall be carried out slowly and evenly without interruption, and the exhaust shall be smooth. If the duct is blocked, the grouting port must be replaced, but

The cement slurry injected for the first time is discharged to avoid the existence of gas between the cement slurry injected for the second time. Fill the duct and seal the air

After the hole, continue to pressurize to 0.5~0.6Mpa, and then seal the grouting hole.   The prestressed duct grouting of multi span connection connected by connector shall be completed by tensioning and grouting one span at a time

After partial tensioning, grout once. When installing the P-anchor extrusion head on the circumference of the connector, pay attention to the installation of the extrusion head

  Bind and fix with fine iron wire.

The exposed length of prestressed reinforcement after anchoring is 20mm~50mm, and the anchorage device shall be protected by end sealing concrete. When long-term exposure is required

Measures shall be taken to prevent corrosion. When the steel strand has floating rust, please remove the floating rust and dirt on the steel strand at the outer end of the anchoring clamping section

The objects shall be cleaned to avoid floating rust and dirt filling the clamping plate slot during installation and tensioning, which may cause sliding wire.

The tool clip is a three piece type and the working clip is a two piece type. The two cannot be mixed; The working anchorage shall not be reused.

The anchorage device shall be properly kept, and shall not have rust, water and other sundries during use, and shall not be conducted by current. When prestress

When the anchor must be tensioned repeatedly when the bundle is long, it is recommended to apply a small amount of lubricant (such as anchor retracting spirit) to the taper hole of the anchor plate, which is beneficial to

The followup and withdrawal of the working clip is also conducive to multiple anchoring of the anchorage device. Outer surface of tool clip and inner surface of anchor plate taper hole

Apply lubricant before use to make anchor retraction flexible.

Safety measures shall be strengthened during tensioning. No one shall stand within 80m of the backward radiation of the tensioning jack.