A prestressing anchorage product is designed and certified for a wide variety of applications: usage 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 approximately 55 strands
YM Series products are made up of tensioning anchor head, wedges, Anchorage Barrel And Wedge plate and spiral reinforcement. Wedge: also referred to as grips or jaws, is produced by high-class alloy steel 20CrMnTi. There are two kinds, the initial one is called working grips which can be with 2 chips; the main one is known as tool grips that is with 3 chips.
Anchor head, also known as anchor rings or anchor block, is key a part of bearing the prestressing tension. There are 2 kinds of anchor head: the initial one is round anchor head that is made by 45# high-quality carbon construction steel, as well as the other is flat anchorage which is made by 40Cr steel. And also the prestressing Anchor head must be dealt with wedges.
Bearing plate is key component, which transfer the stress from anchor head over to concrete under anchor. The process of transfer and distribution of stress change the anti-cracking and load capacity of concrete. Spiral reinforcement, also called hoop reinforcement, is utilized for distributing the concrete and strengthening tendons.
A standard misconception exists, which leads some to imagine that the creation of openings in existing PT slabs is either extremely complex or impossible. Consideration in the correct procedures demonstrates this not to function as the case. Post-formed holes in PT slabs can vary in dimensions which range from the smallest penetrations, which may be necessary to incorporate suspended services, to much bigger openings to permit incorporating lifts or similar installations. In every post-tensioned slabs, the most frequent tendon layouts use a banded design which provides large, regular spaces between tendons that will easily accommodate smaller openings.
In such instances, alterations can be more straightforward than in other types of construction, as the development of holes within these areas can be accomplished without affecting structural performance. The wedge anchor, in their Guidance Note, identifies four kinds of post-formed penetration which can be categorised according to the effect the operation could have on structural integrity. The very first of these relates to the tiniest holes, no more than 20mm in diameter, involving no tendon cutting and which offers minimal risk to the structural integrity from the slab. The next group is classed as a low risk to structural integrity and includes somewhat larger openings, as much as 200mm in diameter in beams or near to columns, but larger in areas which can be less stressed.
The voids are still located between tendons to prevent the necessity to cut these. Inside the third and fourth kinds of penetrations, where it might be required to sever the tendons, the impact on the integrity in the structure is likely to be more significant and demands strengthening and temporary propping of the slab. As the quantity of cut traditional reinforcement is quite a bit less, so is the requirement of 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 loaded with grout right after the tendons happen to be stressed and locked off through split wedges within the anchors, thereby bonding the tendons for the concrete. If larger openings are needed in barrel and wedge anchor, they is often treated in the same way as traditional reinforced concrete slabs since the effects of cutting through 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 actually necessary to cut multiple tendons, mechanical or epoxy anchorages can be put on the ends in the severed tendons to supply even greater security. CCL recently undertook a software that required the roll-out of voids within bonded slabs, to be able to house numerous hoists as well as an escalator within an existing building. After non-destructively seeking the tendons that spanned through the proposed void in the slab, by means of the ‘as built’ drawings from the operations and maintenance manual, the posttensioning duct was opened (Figure 5) and epoxy grout anchors were then installed across the exposed strand just before cutting, thereby giving enhanced surety of anchoring.