Precautions for the construction of prestressed anchors

With the continuous development of China's economy and transportation infrastructure construction, prestressed technology has been widely used in engineering construction in our country. However, with the maturity of technology, the price of prestressed anchors is reasonable, the competition of products is increasingly fierce and chaotic, and the disease problem of prestressed anchors is becoming increasingly prominent, which has become a major risk in the construction of prestressed projects. "Concrete structure engineering construction Code" fully recognizes the seriousness of the problem of anchor disease, construction code 6.2 article proposed that "the performance of prestressed engineering materials should comply with the provisions of the current relevant standards in China", and began to revise the relevant standards to control and solve this problem.

The following are the precautions for the construction of prestressed anchors:

(1) When cutting the prestressed bar, the grinding wheel saw should be used, and the arc cutting should not be used;

(2) When the steel strand is braided, it should be straightened one by one, bundled into bundles, and shall not be disordered. The steel strand is fixed as extrusion anchor or embossed anchor, which should be assembled with the pressure plate and spiral bar in advance;

(3) Before formally stretching large tonnage prestressed tendons, tests should be carried out with professionals. Confirm that the stretching process is reasonable, the stretching elongation value is normal, there are no harmful cracks, and batch stretching can be done. Measure the actual channel friction loss if necessary. The curved prestressed beam shall not be tensioned by small jacks to avoid unnecessary prestress loss. When stretching, the staff must stand in the area and take protective measures, and it is strictly prohibited to stand in the front end of the stretching and stretching prestressed tendons;

(4) The prestressed tendon should be tensioned and managed, the stress should be controlled, and the elongation should be checked. The allowable deviation between the actual elongation and the calculated elongation is -5% ~ +10%. If the tensile value is exceeded, the tension should be suspended; After taking stretching measures to adjust, can continue to stretch; If the elongation value is too small, overtensile measures can be taken, but the tensile limit should not be greater than 0.8fptk value; In the multi-wave curved prestressed tendons, in order to increase the tension stress at the inner support and reduce the tension stress at the lower mouth of the anchor after tension, the overtension stretching technique can be used. The reasonable price of prestressed anchors determines that these products are widely used, so more attention should be paid to protecting people.

Disclaimer: This article is editorially reproduced for the purpose of conveying more information only. If you think that our reproduction violates the Copyright Law or damages your interests, please contact us in time, we will deal with it in a timely manner.