Key Issues to Focus on During the Construction of Prestressed Anchorage
2026-02-01
A prestressed anchor is a type of anchorage device suitable for various engineering construction processes. It is used for prestressed tensioning in concrete and is commonly employed in bridge construction. During use, it should be positioned in advance, followed by concrete pouring, and embedded at both ends of the concrete. In the construction of prestressed anchors, the following nine issues should be noted:
A prestressed anchor is a type of anchorage device suitable for various engineering construction processes. It is used for prestressed tensioning in concrete and is commonly employed in bridge construction. During use, it should be positioned in advance, followed by concrete pouring, and embedded at both ends of the concrete. In the construction of prestressed anchors, the following nine issues should be noted:
1.Prestressing tendons must be cut using a grinding wheel saw; electric arc cutting is not permitted.
2.When bundling steel strands, they should be arranged individually, bundled into strands, and must not be disordered. The fixed end of the steel strands must use extrusion anchors or button-head anchors, which should be pre-assembled with bearing plates and spiral reinforcement.
3.Equipment and instruments used for prestressing should undergo regular maintenance and calibration.
4.Before tensioning prestressing tendons, a compressive strength test report of the concrete must be provided. Prestress can only be applied after the concrete’s compressive strength meets the design requirements and is not less than 75% of the design strength grade.
5.Before tensioning prestressing tendons, the surface of the bearing plate must be cleaned, and the quality of the concrete behind the bearing plate should be inspected. If voids are found in the concrete, they must be repaired with epoxy mortar before tensioning.
6.During anchor installation, the anchor plate must be properly aligned, the wedges should be tightened evenly, and the positions of the wedges should be uniform. However, when driving the wedges, care must be taken not to break them.
7.During tensioning, the prestressing tendons should be loaded from zero to the initial tension corresponding to the starting point of the measured elongation, and then loaded in stages to the required tension.
8.Prestressing tendon tensioning must be managed using stress control and elongation verification. The allowable deviation between the actual elongation and the calculated elongation is -5% to +10%. If this range is exceeded, tensioning must be suspended. After adjustment, tensioning may resume. If the elongation is too small, over-tensioning may be applied, but the tension limit should not exceed 0.8 ftpk. For multi-wave curved prestressing tendons, over-tensioning and relaxation techniques may be employed to improve the tensioning stress at internal supports and reduce tensioning stress at the anchor lower mouth after tensioning.
9.Grouting of ducts must be dense, and the strength grade of the cement mortar should not be lower than C40. Before grouting, the ducts should be moistened and cleaned. Grouting should be performed slowly and evenly without interruption, and air vents must remain clear. If a duct becomes blocked, the grouting port must be replaced. However, the initially grouted cement mortar must be discharged to avoid air pockets between the two grouting stages.
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