A prestressing anchorage method is designed and licensed for a multitude of applications: utilization of 13 mm (.5″) and 15 mm (.6″) strands of all grades (1,770 or 1,860 MPa) including galvanised strands or greased sheathed strands. Prestressing units holding as much as 55 strands
YM Series goods are composed of tensioning anchor head, wedges, stressing anchorage plate and spiral reinforcement. Wedge: also known as grips or jaws, is created by high-class alloy steel 20CrMnTi. There are 2 kinds, one is called working grips which is with 2 chips; the one is called tool grips which can be with 3 chips.
Anchor head, also known as anchor rings or anchor block, is the key part of bearing the prestressing tension. There are 2 kinds of anchor head: the first is round anchor head that is created by 45# high-quality carbon construction steel, as well as the other is flat anchorage that is made by 40Cr steel. And also the prestressing Anchor head must be worked with wedges.
Bearing plate is key component, which transfer the load from anchor head over to concrete under anchor. The method of transfer and distribution of stress change the anti-cracking and load capacity of concrete. Spiral reinforcement, also referred to as hoop reinforcement, is utilized for distributing the concrete and strengthening tendons.
A standard misconception exists, which leads some to believe that the roll-out of openings in existing PT slabs is either extremely complex or impossible. Consideration of the correct procedures demonstrates this never to be the case. Post-formed holes in PT slabs can vary in proportions ranging from the smallest penetrations, which can be needed to incorporate suspended services, to larger openings to enable incorporating lifts or similar installations. In most post-tensioned slabs, the most common tendon layouts utilize a banded design which provides large, regular spaces between tendons that can easily accommodate smaller openings.
In such instances, alterations can often be more straightforward when compared to other kinds of construction, as the development of holes within these areas can be achieved without affecting structural performance. The wedge anchor, in the Guidance Note, identifies four kinds of post-formed penetration which can be categorised according to the effect the operation will have on structural integrity. The very first of those concerns the tiniest holes, no more than 20mm in diameter, involving no tendon cutting and which offers minimal risk to the structural integrity in the slab. The next group is classed as a low risk to structural integrity and includes somewhat larger openings, up to 200mm in diameter in beams or near columns, but larger in areas which are less stressed.
The voids are still located between tendons in order to avoid the necessity to cut these. Within the third and fourth kinds of penetrations, where it will become necessary to sever the tendons, the result on the integrity from the structure is likely to be more significant and calls for strengthening and temporary propping of the slab. As the quantity of cut traditional reinforcement is quite a bit less, so is the necessity for corrosion protection to exposed cut steel.
The most frequent kind of post-tensioning throughout the uk marketplace is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are filled with grout following the tendons have been stressed and locked off by way of split wedges inside the anchors, thereby bonding the tendons to the concrete. If larger openings are required in barrel and wedge anchor, they can be treated in the same way as traditional reinforced concrete slabs because the outcomes of cutting via a bonded tendon remain localised and also the rwkhni redevelops its bond each side from the cut, typically within 1m.
In instances where it is necessary to cut multiple tendons, mechanical or epoxy anchorages may be placed on the ends from the severed tendons to supply even more security. CCL recently undertook a software that required the creation of voids within bonded slabs, so that you can house numerous hoists as well as an escalator inside an existing building. After non-destructively choosing the tendons that spanned with the proposed void within the slab, by means of the ‘as built’ drawings from your operations and maintenance manual, the posttensioning duct was opened (Figure 5) and epoxy grout anchors were then installed round the exposed strand before cutting, thereby giving enhanced surety of anchoring.