What is the post-tensioning method of prestressing?

The post-tensioning method refers to the construction method of pouring cement concrete first, reaching more than 75% of the design strength, and then stretching the prestressed steel bar to form the anchor of the prestressed concrete member.

First, the member is made according to the position of the prestressed steel bar, and the corresponding holes are left in the member. After the strength of the component concrete reaches the specified strength (generally not less than 75% of the design strength standard value), the prestressed steel bar is inserted into the reserved hole, and the prestressed steel bar is anchored at the end of the component, and the pre-tension of the prestressed steel bar is transferred to the concrete through the anchor at the end of the component, so as to generate prestressed stress; The cement slurry is poured into the tunnel so that the prestressed steel and concrete members form a whole.

Post-tensor method:

(1) Concrete with bonded prestressing is first poured, and the steel bars (bundles) are then stretched until the concrete reaches more than 75% of the design strength. The main drawing procedure is 3360 buried pipe hole pouring concrete pumping pipe maintenance, reinforcement tensile anchorage grouting (to stop reinforcement corrosion). The transmission method is to stop the elastic popping of the steel bar by anchoring, so that the cross-section concrete obtains prestress, and the steel bar and concrete become a whole. It is called bonded prestressed concrete. Due to the action of the adhesive force (resistance), the tensile stress of the prestressed steel bar is reduced, resulting in the reduction of the compressive stress of the concrete, so the bond should be minimized. This method is easy to use,

(2) The main drawing process of unbonded prestressed concrete is: wrap the prestressed steel bar with plastic paper or sleeve, pour concrete to maintain the tensile steel bar anchorage, and lubricated anti-corrosion materials such as asphalt along the full length (the bond between the prestressed steel bar and concrete has not yet been established). During the construction process, the steel bar can be poured directly into the design position, without the need to reserve holes, penetrate the steel bar and grouting, simplifying the construction procedure. With the increase of effective precompression stress and the decrease of cost of unbonded prestressed concrete, it is suitable for long-span curved reinforced beams.

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