Multistrand Post-Tensioning System
DYWIDAG has developed a series of jacks and hydraulic pumps in order to efficiently and economically stress its tendons. Versatility is provided by changing devices that make one unit adaptable for many different tendon sizes. DYWIDAG jacks have capacities ranging from 56/250 kips/kN up to 2,191/9,750 kips/kN.
DYWIDAG jacks are highly sophisticated, but still easy to operate. They employ inner tube bundles with automatic gripping devices that guide the strand safely through the inside of the jack. This feature makes it possible to control the stressing operation with the highest degree of reliability.
Minimal wedge seating losses can be achieved with the power seating option. Power seating hydraulically seats the wedges with a predetermined load, individually and simultaneously, rather than relying simply on friction seating. DYWIDAG jacks also make it possible to overstress and release a tendon to compensate for friction losses and maximize the stress level over the tendon length.
Every jack has a pressure relief valve that safely limits hydraulic pressure to prevent overload. To verify the stressing operation, a gauge port is provided directly on the jack.
Stressed tendons can be safely destressed by employing special wedges and a special jack configuration. Hydraulic pumps are generally equipped with a convenient remote control device.
Some important notes concerning the safe handling of high strength strand for prestressed concrete:
- Do not damage surface of the strand.
- Do not weld or burn so that sparks or hot slag will touch any portion of the strand which will be under stress.
- Do not use any part of the strand as a ground connection for welding.
- Do not use strand that has been kinked or contains a sharp bend.
Disregard of these instructions may cause failure of material during stressing.