A prestressing anchorage method is designed and certified for a multitude of applications: utilization 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, stressing anchorage plate and spiral reinforcement. Wedge: also known as grips or jaws, is produced by high-class alloy steel 20CrMnTi. The two main kinds, one is called working grips which can be with 2 chips; usually the one is known as tool grips which can be with 3 chips.
Anchor head, also referred to as anchor rings or anchor block, is the key part of bearing the prestressing tension. There are two kinds of anchor head: the first is round anchor head which is created by 45# high-quality carbon construction steel, as well as the other is flat anchorage that is created by 40Cr steel. And also 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 technique of transfer and distribution of stress change 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 think that the development of openings in existing PT slabs is either extremely complex or impossible. Consideration from the correct procedures demonstrates this to not function as the case. Post-formed holes in PT slabs can vary in size ranging from the tiniest penetrations, which may be needed to incorporate suspended services, to larger openings to allow 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.
Such instances, alterations can often be more straightforward than in other kinds of construction, as the creation of holes within these areas may be accomplished without affecting structural performance. The anchorage grip, in its Guidance Note, identifies four varieties of post-formed penetration which are categorised according to the effect the operation will have on structural integrity. The first of those pertains to the littlest holes, no more than 20mm in diameter, involving no tendon cutting and that provides minimal risk to the structural integrity of the slab. The 2nd 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 to avoid the need to cut these. Inside the third and fourth categories of penetrations, where it will become essential to sever the tendons, the impact on the integrity from the structure will probably be more significant and requires strengthening and temporary propping in 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 type of post-tensioning throughout the uk marketplace is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are filled with grout following the tendons have already been stressed and locked off by means of split wedges in the anchors, thereby bonding the tendons towards the concrete. If larger openings are needed in slab steel anchor, they is often treated in the same way as traditional reinforced concrete slabs since the outcomes of cutting by way of a bonded tendon remain localised and the rwkhni redevelops its bond either side from the cut, typically within 1m.
In instances where it is actually necessary to cut multiple tendons, mechanical or epoxy anchorages can be placed 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, to be able to house a number of hoists plus an escalator within an existing building. After non-destructively seeking the tendons that spanned with the proposed void in 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 around the exposed strand before cutting, thereby giving enhanced surety of anchoring.