A prestressing anchorage product is designed and licensed 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 as much as 55 strands
YM Series items are made from tensioning anchor head, wedges, stressing anchorage plate and spiral reinforcement. Wedge: also called grips or jaws, is created by high-class alloy steel 20CrMnTi. There are two kinds, one is called working grips which is with 2 chips; the one is referred to 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 types of anchor head: one is round anchor head that is produced by 45# high-quality carbon construction steel, and also the other is flat anchorage which is produced by 40Cr steel. As well as the prestressing Anchor head should be dealt with wedges.
Bearing plate is the key component, which transfer the load from anchor visit concrete under anchor. The method of transfer and distribution of stress impact the anti-cracking and load capacity of concrete. Spiral reinforcement, also referred to as hoop reinforcement, can be used for distributing the concrete and strengthening tendons.
A standard misconception exists, which leads some to think 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 function as the case. Post-formed holes in PT slabs can vary in proportions which range from the littlest penetrations, which can be required to incorporate suspended services, to much larger openings to enable adding lifts or similar installations. In every post-tensioned slabs, the most common tendon layouts use a banded design which offers large, regular spaces between tendons which will easily accommodate smaller openings.
Such instances, alterations can be more straightforward than in other kinds of construction, as the creation of holes within these areas can be achieved without affecting structural performance. The dead-end anchorage, in their Guidance Note, identifies four types of post-formed penetration which can be categorised in accordance with the effect the operation could have on structural integrity. The very first of these pertains to the littlest holes, no more than 20mm in diameter, involving no tendon cutting and which offers minimal risk towards the structural integrity of 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 close to columns, but larger in areas which are less stressed.
The voids are still located between tendons to prevent the need to cut these. In the third and fourth kinds of penetrations, where it will become required to sever the tendons, the result on the integrity of the structure may very well 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 necessity for corrosion protection to exposed cut steel.
The most frequent type of post-tensioning in the united kingdom marketplace is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are loaded with grout right after the tendons have already been stressed and locked off through split wedges within the anchors, thereby bonding the tendons for the concrete. If larger openings are essential in pre-stressing anchor, they can often be treated in the same way as traditional reinforced concrete slabs as the effects of cutting via a bonded tendon remain localised as well as the rwkhni redevelops its bond both sides in 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 from the severed tendons to supply even more security. CCL recently undertook an application that required the development of voids within bonded slabs, so that you can house several hoists and an escalator inside an existing building. After non-destructively locating the tendons that spanned with the proposed void in the slab, through 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 prior to cutting, thereby giving enhanced surety of anchoring.