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 items are composed of tensioning anchor head, wedges, Post Tension Anchor plate and spiral reinforcement. Wedge: also known as grips or jaws, is produced by high-class alloy steel 20CrMnTi. The two main kinds, the first is called working grips that is with 2 chips; the one is known as tool grips which is with 3 chips.
Anchor head, also referred to as anchor rings or anchor block, is the key a part of bearing the prestressing tension. There are 2 kinds of anchor head: the initial one is round anchor head which is made by 45# high-quality carbon construction steel, and the other is flat anchorage that is made by 40Cr steel. As well as the prestressing Anchor head has to be dealt with wedges.
Bearing plate is the key component, which transfer the load from anchor visit concrete under anchor. The technique of transfer and distribution of stress affect the anti-cracking and load capacity of concrete. Spiral reinforcement, also called hoop reinforcement, is used 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 from the correct procedures demonstrates this not to be the case. Post-formed holes in PT slabs will vary in size starting from the tiniest penetrations, which might be required to incorporate suspended services, to much bigger openings to allow the addition of lifts or similar installations. In most post-tensioned slabs, the most typical tendon layouts use a banded design which provides large, regular spaces between tendons that can easily accommodate smaller openings.
In these instances, alterations can be more straightforward when compared to other types of construction, as the roll-out of holes within these areas can be accomplished without affecting structural performance. The anchorage grip, in their Guidance Note, identifies four kinds of post-formed penetration that are categorised in accordance with the effect the operation could have on structural integrity. The first of these pertains to the tiniest holes, no more than 20mm in diameter, involving no tendon cutting and that offers minimal risk for the structural integrity from the slab. The 2nd 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 columns, but larger in areas which can be less stressed.
The voids continue to be located between tendons in order to avoid the requirement to cut these. Inside the third and fourth categories of penetrations, where it might be required to sever the tendons, the impact on the integrity from the structure will probably be more significant and demands strengthening and temporary propping from the slab. As the quantity of cut traditional reinforcement is quite a bit less, so is the requirement for corrosion protection to exposed cut steel.
The most typical type of post-tensioning throughout the uk industry is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are loaded with grout following the tendons have been stressed and locked off by means of split wedges inside the anchors, thereby bonding the tendons for the concrete. If larger openings are needed in slab steel anchor, they can often be treated in the same way as traditional reinforced concrete slabs since the outcomes of cutting via a bonded tendon remain localised as well as the rwkhni redevelops its bond both sides from the cut, typically within 1m.
In instances where it really is necessary to cut multiple tendons, mechanical or epoxy anchorages can be put on the ends of the severed tendons to supply even more security. CCL recently undertook a software that required the development of voids within bonded slabs, to be able to house numerous hoists and an escalator inside an existing building. After non-destructively seeking the tendons that spanned from 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 across the exposed strand before cutting, thereby giving enhanced surety of anchoring.