Prestressed steel strand tightening and releasing device

The invention provides a prestressed steel strand tightening and releasing device, and belongs to the technical field of building construction, the prestressed steel strand tightening and releasing device comprises a tensioning piston pipe and a clamping piece sleeve, the clamping piece sleeve is sleeved with a sealing cover nut, the sealing cover nut is sleeved with an anchor removing sleeve, and the tensioning piston pipe is sleeved with the anchor removing sleeve; three tool clamping pieces are annularly connected to the clamping piece sleeve at equal intervals, the rear ends of the tool clamping pieces extend out of the clamping piece sleeve, and each tool clamping piece is provided with an outer conical surface with the radius gradually reduced from front to back; a reducing section is arranged at the front end of the tensioning piston pipe, and the outer diameter of the reducing section is smaller than that of the tensioning piston pipe; an anchor cup is connected to the reducing section, and the anchor