A prestressing anchorage system is designed and licensed for numerous 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 goods are composed of tensioning anchor head, wedges, Post Tension Anchor plate and spiral reinforcement. Wedge: also known as grips or jaws, is made by high-class alloy steel 20CrMnTi. There are two kinds, one is called working grips that is with 2 chips; the one is referred to as tool grips which is with 3 chips.
Anchor head, also known as anchor rings or anchor block, is the key a part of bearing the prestressing tension. The two main kinds of anchor head: the initial one is round anchor head that is produced by 45# high-quality carbon construction steel, as well as the other is flat anchorage which can be produced by 40Cr steel. And also the prestressing Anchor head must be worked with wedges.
Bearing plate is vital component, which transfer the burden from anchor visit concrete under anchor. The technique of transfer and distribution of stress impact the anti-cracking and load capacity of concrete. Spiral reinforcement, also called hoop reinforcement, is used for distributing the concrete and strengthening tendons.
A typical misconception exists, which leads some to believe that the development of openings in existing PT slabs is either extremely complex or impossible. Consideration from the correct procedures demonstrates this to not become the case. Post-formed holes in PT slabs will vary in proportions which range from the smallest penetrations, which may be needed to incorporate suspended services, to much bigger openings to allow incorporating lifts or similar installations. In every post-tensioned slabs, the most typical tendon layouts use a banded design which supplies large, regular spaces between tendons which will easily accommodate smaller openings.
Such instances, alterations is often more straightforward compared to other sorts of construction, as the development of holes within these areas can be accomplished without affecting structural performance. The wedge anchor, in the Guidance Note, identifies four types of post-formed penetration which are categorised based on the effect the operation will have on structural integrity. The initial of such concerns the smallest holes, no more than 20mm in diameter, involving no tendon cutting and which offers minimal risk towards the structural integrity of the slab. The next group is classed being a low risk to structural integrity and includes somewhat larger openings, up to 200mm in diameter in beams or close to columns, but larger in areas that are less stressed.
The voids continue to be located between tendons in order to avoid the necessity to cut these. In the third and fourth categories of penetrations, where it will become 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 from the slab. As the quantity of cut traditional reinforcement is significantly less, so is the necessity for corrosion protection to exposed cut steel.
The most typical kind of post-tensioning throughout the uk market is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are full of grout following the tendons have already been stressed and locked off through split wedges in the anchors, thereby bonding the tendons for the concrete. If larger openings are essential in slab steel anchor, they is often treated in the same manner as traditional reinforced concrete slabs as the outcomes of cutting by way of a bonded tendon remain localised as well as the rwkhni redevelops its bond both sides of the cut, typically within 1m.
In instances where it is actually required 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 a software that required the roll-out of voids within bonded slabs, in order to house a number of hoists and an escalator inside an existing building. After non-destructively seeking the tendons that spanned from the proposed void inside 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 around the exposed strand before cutting, thereby giving enhanced surety of anchoring.