Attentions During Tensioning of Prestressed Fully Threaded Rebar System
Fully threaded bar systems are a type of prestressed anchorage. It includes anchor nuts, anchor plates, and couplers.
The prestressed high-strength steel bars (fully threaded rebar) are anchored by nuts. The performance is reliable and can be used repeatedly, and the operation is convenient. Finish-rolled rebar has a small shrinkage loss and can be used in situations where the finish-rolled rebar is short (such as vertical prestressed strands and bridge deck transverse prestressed strands). The rebar can be arbitrarily connected to the length of the steel bar by adopting the finish-rolled rebar coupler. The multi-strand center-hole jack can be used for tensioning.
The specifications of fully threaded bar anchorages are for the fully threaded bar of dia.15mm, 20mm, 25mm, 32mm, 36mm, 40mm.
Matters needing attention when tensioning prestressed finish-rolled rebar anchorages:
(1) When measuring the elongation and tightening the anchor nut, stop the jack.
(2) The oil supply and oil return process of the jack should proceed slowly and smoothly. Avoid excessive oil return.
(3) When pulling or returning the wedges, it is forbidden to stand behind the jack to prevent the prestressed finish-rolled rebar from breaking or anchors or wedges popping out and hurting people.
(4) The tensioning operation should be carried out in accordance with regulations to prevent the prestressed tendons from over-limiting and causing breaking accidents.
(5) When the pressure-bearing surface of the anchor plate is not perpendicular to the centerline of the tunnel, a thin steel plate should be placed under it to adjust its verticality. Weld it to prevent it from moving when stressed.
(6) The jack support must be in good contact with the anchor plate, and the position should be straight and symmetrical to prevent the support from being unstable or uneven.
(7) When the oil pump is running abnormally, stop and check immediately. When there is pressure, do not twist the oil pump or jack at will.
(8) When handling and installing finished rolled rebars, avoid damaging them. It is strictly forbidden to spot-weld fully threaded steel bars;
(9)After the corrugated duct is fixed to the spiral reinforcement, screw the anchor plate into one end of the spiral reinforcement, and then screw on the anchor nut. The function of the anchor plate and the anchor nut is to tighten the steel bars.