Discussion on the Sequence and Construction Key Points of Prestressed Tensioning
2026-02-03
Industry experts point out that the sequence of prestressed tensioning is not fixed; it must be determined comprehensively based on factors such as bridge structure type, load-bearing characteristics, construction techniques, and operational safety. The core principle is to adhere to the basic guidelines of "uniformity, symmetry, and gradual progression," avoiding hidden risks such as structural torsion, lateral bending, or local overstress caused by unbalanced tensioning. According to the requirements of the *Code for Construction of Concrete Structures (GB50666-2011)*, different structural forms of bridges have clear specifications for tensioning sequences.
Industry experts point out that the sequence of prestressed tensioning is not fixed; it must be determined comprehensively based on factors such as bridge structure type, load-bearing characteristics, construction techniques, and operational safety. The core principle is to adhere to the basic guidelines of "uniformity, symmetry, and gradual progression," avoiding hidden risks such as structural torsion, lateral bending, or local overstress caused by unbalanced tensioning. According to the requirements of the *Code for Construction of Concrete Structures (GB50666-2011)*, different structural forms of bridges have clear specifications for tensioning sequences.
In addition to scientifically controlling the tensioning sequence, the management of key points throughout the construction process is essential to ensure the quality of tensioning. Preparations before tensioning must be meticulous and comprehensive: the tensioning force should be determined based on the tensioning control stress and the cross-sectional area of the prestressing tendons, and the oil pump pressure gauge readings should be set according to the calibration results of the jack. At the same time, the elongation during tensioning must be calculated. The quality of concrete construction must be strictly inspected to ensure its strength meets design requirements. If the design does not specify explicit requirements, the concrete strength should not be less than 75% of the design strength grade. The prestressed ducts must be cleaned, and the integrity of the anchorage devices and prestressing tendons must be checked. Tensioning equipment should be calibrated and used as a matched set, with calibration intervals not exceeding six months or 200 tensioning operations.
The final steps after tensioning are equally important. Anchoring should be performed after the tensioning control stress has stabilized, and the internal shrinkage of the prestressing tendons at the tensioning end during the anchoring stage must comply with design and code requirements. After tensioning, grouting of the ducts must be carried out promptly. It is recommended to use specialized ready-mixed grouting materials to prepare the slurry, with controlled water-to-binder ratios to ensure dense grouting. During the grouting process and within 48 hours after grouting, the temperature of the structural concrete should not fall below 5°C. If daytime temperatures exceed 35°C, grouting should preferably be conducted at night. Finally, anchorage sealing should be performed: the exposed parts of the prestressing tendons should be cut using mechanical methods, with the exposed length not less than 1.5 times the diameter and not less than 30 mm. Anchorage devices should be sealed with fine aggregate concrete or non-shrink waterproof mortar of the same strength grade as the structure to ensure structural durability.
Industry insiders indicate that optimizing the sequence of prestressed tensioning and managing key construction points are critical measures for improving bridge engineering quality and ensuring structural safety and stability. In the future, with continuous technological innovation and the accumulation of practical experience, prestressed tensioning construction will develop toward greater refinement, intelligence, and standardization. This will further improve construction standards, strengthen technical management, and provide robust support for the high-quality development of China's transportation infrastructure.
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