TENSION METHOD AND DEVICE FOR PC ANCHOR DIFFERENT IN FREE LENGTH

PURPOSE:To simultaneously introduce uniform press stress by directly connecting a fixed hydraulic cylinder and a movable hydraulic cylinder to each other by a common piston rod, and installing a clamp fitting to form a composite hydraulic jack, thereby adjusting a difference in elongation of tension materials different in free length. CONSTITUTION:The pressure receiving area of a fixed hydraulic cylinder 21 is made smaller than the pressure receiving area of a movable hydraulic cylinder 22. The fixed hydraulic cylinder 21 is reset in a contraction position, and the terminal 4a of a tension material 4 having a long free length is clamped at a piston rod 23. The movable hydraulic cylinder 22 is reset to the state of being stretched to its full length, and the terminal 5a of a tension material 5 having a short free length is clamped. Subsequently, operating oil of the same pressure is fed to the fixed hydraulic cylinder 21 and the movable hydraulic cylinder 22 at the same time. Whereupon, though the tension material 4 having a long free length is tensed, the tension material 5 having a short free length is in the state of being stretched to its full length, so that tensile force is not applied. As the piston rod 23 is pushed up, however, the tension material is pressed in the direction of contraction to be pushed up in the direction of elongation as a whole. Thus, press stress is introduced to all tension materials different in free length at one time so as to improve the functional quality as PC anchor.