Prestressed anchor construction safety precautions

(1) Tension end anchorage: installed at the end of prestressed reinforcement beams, tensioned anchorage is also known as prestressed anchorage. To put it bluntly, an anchor is a type of anchor used to maintain the tensile strength of prestressed steel bars and transfer to mixed tension in post-tensioned structures or prefabricated members.

(2) Fixed fixed end anchorage: installed at the end of prestressed reinforced beams, generally buried in concrete, not used for prestressed anchorage.

Common problems:

(1) For laser cutting of prestressed anchors, sand wheel saw should be selected, and electric arc laser cutting should not be selected;

(2) When the steel hinge wire is braided, it should be cleaned one by one, and the whole bundle should be bundled without confusion. The steel hinge line is fixed on the web end of the extrusion molding anchorage or embossed pattern anchorage, which should be assembled with the pressure plate and spiral reinforcement in advance;

(3) The machinery, machinery, equipment and instrument panel that release prestress should be maintained and calibrated;

(4) Before the prestressed anchor is tensioned, the hydraulic test report of concrete strength shall be presented. When considering the provisions of the design scheme, the tensile strength of the concrete is higher than 75% of the compressive strength of the design scheme, the prestress can be released.

(5) Before the prestressed anchor is tensioned, the pressure surface should be removed, and the quality of the concrete behind the pressure plate should be checked. If there are cracks in the concrete, repair with epoxy mortar before stretching;

(6) When installing the anchor, the anchor plate should be correctly solved, the clip should be tightened, and the piece position should be symmetrical: but the clip should not be knocked too much, so as not to damage the clip;

(7) Before announcing the tension of large tons of prestressed steel bars, prestress tests should be carried out with technicians. It is determined that the prestressed processing technology is effective, the prestressed extension value is normal, there is no harmful gap, and batch prestressed can be done. Measure specific hole friction if necessary. The prestressed beam shall not choose the single prestressed of small and medium-sized hydraulic jacks to stop the excess prestressed wear. When prestressing, the actual operator must stand in the protection area, take protective measures, pay attention to the actual operator prohibit the development of prestressed and prestressed reinforcement front end;

(8) When prestressing the prestressed anchor, the initial tensile force of the starting point of the measured extension value should be loaded from zero, and then the grade classification should be loaded into the required tensile force;

(9) The prestress management method of prestressed anchorage adopts ground stress control and elongation strength verification. The allowable error between the specific elongation value and the calculated elongation value is -5% ~ +10%. If this value is exceeded, the prestress should be suspended; After effective adjustment, prestressing can be done again; If the elongation value is too small, the superprestressing countermeasure can be adopted, but the tension limit value cannot exceed 0.8fptk value. In the multi-wave curve prestressed steel bar, in order to increase the prestressed ground stress at the inner rubber support and reduce the prestressed ground stress at the hole under the anchor, the overtension loosening technology can be adopted.

(10) The specified density of hole grouting, the compressive strength level of cement mortar is not less than C40. Before grouting, the holes should be wet and clean, grouting should be carried out slowly and symmetrically, and the exhaust pipe should be unblocked. If the hole is blocked, it is necessary to remove and replace the grouting port, but it is necessary to discharge the cement mortar that is injected once to stop the steam in the middle of the cement mortar that is injected twice. After filling the hole and sealing the discharge hole, it should be filled again to 0.5-0.6Mpa, and wait for the closed grout hole. According to the grout aspect ratio, the grout working pressure of the longitudinal hole should be determined.

(11) The holes of multi-span continuous prestressed steel bars connected by RF connectors should be tensioned for one span, and then grouting for one span, and grouting shall not be performed once after each span is prestressed;

(12) The exposed length of prestressed steel bars after anchoring is not suitable for less than 30mm. The anchor is maintained by sealing concrete. When long-term exposure is required, countermeasures to avoid rust should be taken; If there is floating rust on the steel hinge line, clean the floating rust and waste on the steel hinge line at the anchorage and outer web end of the steel bar, so that the rabbit will float rust during installation and prestressing, and the waste will cover the red slot of the sandwich, resulting in slipping.

(13) The tool clip is three-piece type, and the clip is two-piece type during work, which can not be used interoperably. The anchor can not be used as a tool anchor and can not be reused many times;

(14) The anchor should be properly stored, and there should be no rust, water, dirt and other dirt during use. In the work, in addition to the foam in the gift box, you can also use clips. However, when the prestressed beam is long and continuous prestressed reinforcement anchorage is required, it is recommended to apply a small amount of lubricant (such as anchor spirit) in the taper hole of the anchor plate, which is conducive to the tracking and anchoring of the clips in the work, and is also conducive to the multiple reinforcement anchoring of the anchor. Apply lubricant to the outer surface of the special tool clip and the inner surface of the anchor plate cone hole before application, often eliminate the dirt on the surface of the clip, so that anchoring is convenient, but when the clip cracks or the tooth surface is damaged, it needs to be replaced and can not be used again;

(15) Protection and preventive measures should be taken when prestressing, and people can not stand after tensioning jacks;

(16) The reinforcement anchoring management system shall adopt supporting facilities and shall not be interused with other management systems. If you want to perform a load test, use a solvent (such as automotive gasoline) to clean the interlayer and wipe the rust inhibitor of the anchor welding bolt, otherwise it will damage the anchorage characteristics of the steel bar;

(17) The construction of prestressed projects shall be carried out by technical construction personnel, and the construction team shall be trained in skills and be certified.

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