A prestressing anchorage product is designed and certified for a wide variety 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 made from tensioning anchor head, wedges, Anchorhead plate and spiral reinforcement. Wedge: also referred to as grips or jaws, is made by high-class alloy steel 20CrMnTi. The two main kinds, the initial one is called working grips which can be with 2 chips; the one is called tool grips which is with 3 chips.
Anchor head, also referred to as anchor rings or anchor block, is vital part of bearing the prestressing tension. There are two forms of anchor head: the first is round anchor head that is made by 45# high-quality carbon construction steel, as well as the other is flat anchorage which is made by 40Cr steel. And 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, can be used for distributing the concrete and strengthening tendons.
A common misconception exists, which leads some to believe 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 will be different in size starting from the smallest penetrations, which might be needed to incorporate suspended services, to much larger openings to allow adding lifts or similar installations. In most post-tensioned slabs, the most typical tendon layouts make use of a banded design which offers large, regular spaces between tendons which will easily accommodate smaller openings.
Such instances, alterations can be more straightforward compared to other kinds of construction, as the roll-out of holes within these areas may be accomplished without affecting structural performance. The post tension anchorage, in its Guidance Note, identifies four kinds of post-formed penetration which are categorised based on the effect the operation may have on structural integrity. The very first of those relates to the littlest holes, no more than 20mm in diameter, involving no tendon cutting and that offers minimal risk for the structural integrity of the slab. The 2nd group is classed as being a low risk to structural integrity and includes somewhat larger openings, up to 200mm in diameter in beams or near to columns, but larger in areas that are less stressed.
The voids are still located between tendons in order to avoid the requirement to cut these. Inside the third and fourth kinds of penetrations, where it becomes necessary to sever the tendons, the effect on the integrity in the structure will probably be more significant and demands strengthening and temporary propping in 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 frequent type of post-tensioning in the united kingdom market is bonded PT (Figure 4). Ducts carrying high-tensile steel strands are loaded with grout right after the tendons have been stressed and locked off through split wedges in the anchors, thereby bonding the tendons for the concrete. If larger openings are required in slab steel anchor, they is often treated in a similar manner as traditional reinforced concrete slabs as the effects of cutting via a bonded tendon remain localised and the rwkhni redevelops its bond either side from the cut, typically within 1m.
In instances where it is essential to cut multiple tendons, mechanical or epoxy anchorages may be placed on the ends of the severed tendons to offer even more security. CCL recently undertook a software that required the development of voids within bonded slabs, to be able to house a number of hoists and an escalator in a existing building. After non-destructively choosing the tendons that spanned with 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 around the exposed strand prior to cutting, thereby giving enhanced surety of anchoring.