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Gaodetec company supply QYC270 hydraulic jack is single post tension hydrualic jack, it can use for tension 12.7mm and 15.24mm pc strand.
Prestressing is applied to the concrete, typically by tensioning the prestressed reinforcement. The tensioned steel bars are reversed and the concrete is pressed to compress the concrete. There are two methods for tensioning prestressed steel bars: pretensioning and posttensioning.
First, the first method
The pretensioning method refers to a method of first stretching the steel bars on the pedestal or in the steel mold and then pouring the concrete. 1. Fix one end of the prestressed steel bar to the steel beam of the pedestal with a clamp. The other end is connected to the tensioning mechanism by means of a tensioning clamp and a force measuring device. After the tension is pulled to the specified control stress, the prestressed steel bars are fixed by the clamp at the tension end, and the concrete is poured. When the concrete reaches a certain strength, the prestressed steel bars are cut or loosened, due to the bonding between the prestressed steel bars and the concrete, The concrete is subjected to pre-compression stress.
The pre-tensioning method has the characteristics of less production process, simple process and easy control of construction quality.
Second, post-tension method
The post-tensioning method refers to a construction method in which a concrete member is first poured and then the prestressed steel bar is directly stretched on the member. When pouring concrete members, leave holes in the components in advance. When the concrete reaches the specified strength, the prestressed steel bars are inserted into the tunnel, the prestressed steel bars are anchored at the end of the member with anchors, and the prestressed steel bars are tensioned at the other end of the member by tensioning tools, and the prestressed steel bars are tensioned. The member is subjected to pre-compression stress. When the specified tension control stress value is reached. Anchor the tensioned steel bars at the ends. For bonded prestressed concrete. Filling the filling material (such as cement mortar) into the pores of the component. The prestressed steel bars are integrated with the components.
The post-tension method is characterized by the fact that it does not require a pedestal and can be prefabricated or constructed on site. It is necessary to stretch the prestressed steel bars one by one, the anchors are used in a large amount, and they cannot be reused, and the construction is labor-intensive, so the cost is high.
