A prestressing anchorage system is designed and certified for a multitude of applications: use 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 up to 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 created by high-class alloy steel 20CrMnTi. The two main kinds, the initial one is called working grips which can be with 2 chips; the main one is known as tool grips which can be with 3 chips.
Anchor head, also referred to as anchor rings or anchor block, is key a part of bearing the prestressing tension. There are 2 forms of anchor head: the first is round anchor head which is made by 45# high-quality carbon construction steel, and also the other is flat anchorage which can be 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 burden from anchor head over to concrete under anchor. The method of transfer and distribution of stress affect 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 typical misconception exists, which leads some to think that the creation of openings in existing PT slabs is either extremely complex or impossible. Consideration in the correct procedures demonstrates this not to be the case. Post-formed holes in PT slabs will be different in proportions which range from the tiniest penetrations, which can be required to incorporate suspended services, to much larger openings to enable incorporating lifts or similar installations. In most post-tensioned slabs, the most common tendon layouts utilize a banded design which offers large, regular spaces between tendons that can easily accommodate smaller openings.
In these instances, alterations can often be more straightforward than in other types of construction, as the creation of holes within these areas can be accomplished without affecting structural performance. The dead-end anchorage, in its Guidance Note, identifies four kinds of post-formed penetration which can be categorised in accordance with the effect the operation could have on structural integrity. The first of these relates to the smallest holes, a maximum of 20mm in diameter, involving no tendon cutting and which offers minimal risk for the structural integrity of the slab. The next group is classed being 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 are less stressed.
The voids are still located between tendons to prevent the need to cut these. Within the third and fourth kinds of penetrations, where it might be necessary to sever the tendons, the effect on the integrity of the structure will probably be more significant and calls for strengthening and temporary propping of the slab. As the quantity of cut traditional reinforcement is significantly less, so is the requirement of corrosion protection to exposed cut steel.
The most common form of post-tensioning throughout the uk marketplace is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are full of grout right after the tendons have already been stressed and locked off through split wedges within the anchors, thereby bonding the tendons towards the concrete. If larger openings are essential in barrel and wedge anchor, they is often treated in a similar manner as traditional reinforced concrete slabs as the results of cutting by way of 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 is actually essential to cut multiple tendons, mechanical or epoxy anchorages can be put on the ends of the severed tendons to offer even more security. CCL recently undertook a software that required the roll-out of voids within bonded slabs, so that you can house a number of hoists plus an escalator in a existing building. After non-destructively seeking the tendons that spanned through the proposed void inside the slab, through the ‘as built’ drawings from your operations and maintenance manual, the posttensioning duct was opened (Figure 5) and epoxy grout anchors were then installed around the exposed strand before cutting, thereby giving enhanced surety of anchoring.