PC strand

PC Strand, or prestressed concrete steel strand, is a twisted steel cable composed of 2, 3, 7 or 19 high strength steel wires and is stress-relieved (stabilized) for prestressed concrete or similar purposes.

If you want to learn more, please visit our website Compacted Steel Strand China.

 

Classification

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PC strand is classified according to the number of steel wires in a strand: 2 wire strand, 3 wire strand, 7 wire steel strand[1] and 19 wire steel strand. It can be classified according to the surface morphology and can be divided into: smooth steel strand, scoring strand, mold pulling strand (compact), coated epoxy resin steel strand. They can also be classified by diameter, or intensity level, or standard.

 

Specifications

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In the description and list of the table we often see, there are 15-7Φ5, 12-7Φ5, 9-7Φ5 and other specifications of the prestressed steel strand. To 15-7Φ5, for example, 5 said a single diameter 5.0mm of steel, 7Φ5 said seven of the steel wire to form a strand, and 15 that the diameter of each strand of 15mm, the total meaning is "one The beam consists of 7 strands of diameter 15 mm (each having a total diameter of about 15.24 mm, a dimensional deviation +0.40 -0.20; a diameter of about 5.0 mm per filament). The general sectional area is calculated according to 140mm ^ 2. The theoretical breaking value is 140 * 1860 = 260.4 kN, which can withstand the tension of 156.24-169.26 kN according to the prestressing standard of 60% -65%.

 

Materials

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Using high-carbon steel wire rod, after surface treatment it is cold drawn into steel wire, and then the strand structure will be a number of steel wires stranded into shares. Next the elimination of stress by way of a stabilization process. In order to extend durability, the wire can have metal or non-metallic coatings, such as galvanized, or epoxy resin coating. In order to increase the bond strength with the concrete, the surface can have nicks and so on. The prestressed strands of the mold are twisted to form a mold compression process, the structure is more compact, and the surface layer is more suitable for anchoring. Production of unbonded prestressed steel strand (unbonded steel strand) using ordinary prestressed steel wire, coated with oil or paraffin after the packaging into high-density polyethylene (HDPE) bags.

 

Features

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The main characteristic of the prestressed steel strand is high strength and relaxation performance is good, the other when the more straight. Common tensile strength levels of 1860 MPa, as well as 1720, 1770, 1960, 2000, 2100 MPa and the like intensity levels. The yield strength of this steel is also higher.

 

Application

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In most of the post-tensioned and pre-tensioned prestressed project, smooth steel strand is the most widely used prestressed steel. Stranded strand is mainly used to enhance the project, but also for nuclear power and the like works. Galvanized steel strand commonly used in the bridge of the tie rod, cable and external prestressing works. Epoxy coated steel stranded wire is similar to galvanized prestressed steel wire.

 

Standards

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Countries have standards for prestressed strand, such as: China Standard GB / T 5224, American Standard ASTM A416, British standard BS 5896 and the Japanese standard JIS G3536, the Australian standard AS / NZS 4672, Brazilian standard NBR-7483[2]

 

References

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Understanding Prestressing: Pre-tension or Post-tension?

 

The loading of any structural element induces stresses in both compression and traction. The stability of constructions requires that these constraints never exceed the capacity of the materials. Various techniques have been developed to overcome this difficulty.

 

 

 

 

 

 

 

A first technique is the reinforced concrete where steel bars are placed in the formwork before concreting. They adhere to concrete and form a composite material with it. Since concrete has no tensile strength, rebar provides this essential strength for the load transfer. The bars are passive; they are only solicited when the structure is loaded. Concrete alone does not offer the required flexibility. Therefore, reinforcing bars - a reinforcement - are often incorporated into concrete to limit the extent of cracks. However, this reinforcement provides only passive reinforcement, it means, it does not transfer any load or provide additional resistance before the concrete cracks.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Prestressed Concrete

 

 

The second technique is the prestressed concrete. As in reinforced concrete, steel is associated with concrete, but, in this case, it is tensioned before loading the structure. Prestressing is therefore a technique which consists in inducing favorable internal forces. These are designed to reduce the weakness of concrete in tension. The design of reinforced concrete prestressed elements often includes the use of passive steel bars in parallel to the prestressed steel. Prestressing is most often carried out using tensioned cables embedded in concrete. Steel is not necessarily in direct contact with concrete.

 

 

 

 

 

 

 

Two types of prestressed concrete can be distinguished depending on when the steel is tensioned. The cables can be tensioned before concreting the element - pre-tension - or after - post-tension.

 

 

 

 

 

 

 

 

 

Pre-tensioning

 

 

This method consists of placing "cables" or steel strands which are stretched between two prestressing benches which serve as anchors. By definition, a strand is generally a cable made up of 7 individual steel wires: 6 wires coiled in a long pitch around a central wire. Each strand is individually anchored and tensioned by a single-strand anchorage until it is removed from the form. It passes through a formwork where concrete is poured in place in contact with them. After curing the concrete and achieving the minimum compressive strength, the strands are cut at each end between the formwork and the bench. At this point, the steels transfer part of their tension in compression to the concrete: compression of the concrete balances the tension in the strands. The tensile force is then transferred by adhesion to hardened concrete. A certain desired deflection of pre-tension at the level of the element under tension is often observable after the transfer. The elements are then stripped and stored ready to be transported. Pre-tensioning is carried out in specialized workshops equipped with tensioning benches. This technique is used in prefabrication and allows the production of beams, posts, prestressed slabs ...

 

 

 

 

 

 

 

 

 

Post-tensioning

 

 

Post-tensioning is an operation carried out on site which consists in putting strands in tension after the concrete has been poured and has reached a minimum compressive strength. The fresh concrete is poured in place in a formwork including reinforcement where specially designed ducts and anchors are installed embedded in concrete. Once the element is in place or the formwork has been removed, the strands can be threaded inside the duct and tensioned using a jack. After removing the jack, the strands transfer part of their tension in compression to the concrete: the compression of the concrete balances the tension. The layout of the duct is not necessarily straight; they can be curved to transfer forces into predefined areas. This system therefore offers active reinforcement. Post-tensioning places the concrete structure under compression in areas where the loads cause tensile stresses. It applies a compressive stress to the materials, which compensates for the tensile stresses that the concrete could undergo under the loading of the element. A certain desired deflection at the level of the element under tension is then observable after the transfer. Unlike pre-tensioning, prestressing steel is installed and tensioned on site at the final position of the element.

 

 

 

 

 

 

 

Post-tensioning offers the possibility of constructing the concrete elements at any desired location including its final position in the structure. The transport constraints of the elements must however be considered. Post-tensioning is therefore an essential system for the construction of segmental structures. This method is generally used for large civil engineering works. Post-tensioning is implemented using strands or bars of high-strength steel. We call a tendon, the entire post-tensioning system which includes the group of one or more strands or a bar threaded into a duct anchored at both ends by anchoring devices and which is injected or not to fill the empty space remaining after tensioning.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A wide variety of post-tensioning systems are available to suit several applications. We can characterize its tendons according to 3 main categories:

 

 

 

 

 

 

 

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Internal Bonded Tendon

 

 

System composed of several strands which are placed inside a plastic or metal sheath injected by a cementitious grout and which is embedded in a concrete element. After the tensioning, the sheath is injected with a cementitious grout which cures and hardens in order to adhere the tendon to the concrete which surrounds it. The cure for grout and hardening allows the tendon to behave as an integral system without any relative movement between the steel strands and the concrete element. The grout provides a physical barrier to water and contaminants while providing an alkaline environment that protects the prestressed steel from corrosion. This type of post-tensioning system is often used for engineering structures and for heavily stressed beams in buildings. Flat tendon systems with oval ducts can also be an excellent choice for thin slabs and bridge deck.

 

 

 

 

 

 

 

 

 

Internal Unbonded Tendon

 

 

System confined to a concrete element whose prestressing steel does not adhere to the concrete surrounding it, except at anchors. The system typically consists of a single strand which is coated with a corrosion inhibitor like grease or wax and which is protected by an extruded plastic sheath. This type is used for structural slabs of buildings or parking lots and slabs on the ground. Increasingly, it is integrated into infrastructure engineering projects.

 

 

 

 

 

 

 

 

 

External Unbonded Tendon

 

 

System which is installed outside the structural element with the exception of the anchors and at the point of deviation. Tendons are usually installed in smooth sheaths which can be injected with a cementitious grout or liquid wax. The external tendons allow a relative movement between the tendons and the structural element to which they are attached and that is why they are considered in practice as Unbonded. They are typically used for the erection of prefabricated segments and cable stayed bridge. This type of post-tensioning allows access for maintenance and replacement of the strands, and thus represents the best solution for the improvement and rehabilitation of engineering structures.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Advantages of post-tensioning

 

 

More flexibility in design: length and free span of the elements

Allow faster construction by using prefabricated segments

Reduction of costs of building materials by optimizing the dimensions of the elements of the structure

Possibility of increasing the load of the structural element later

Ability to control when and where force is applied to the structure

Durability: controls and minimizes cracking of the concrete

Reduction of maintenance costs over the life of the structure

 

 

 

 

 

 

To learn more about prestressing, our team offers a full range of services to help you in your different projects. Contact our experts at: info@force-s.com

 

 

 

 

 

 

 

#posttension #engineering

 

 

Prestressed PC Steel Wire, Diameter, Intensity, Types and Application.

 

Prestressed PC Steel Wire

 

High Tensile Prestressed PC Steel Wire for Concrete

Intensity: 1470Mpa-1770Mpa.

Standard: ASTM, BS, DIN, GB.

Wire Diameter: 4.00mm-12.00mm.

Types of prestressed PC steel wire:

According to diameter and can be categorized as: 4mm, 4.8mm, 5.0mm, 5.1mm, 6.0mm, 6.35mm, 7.0mm, 7.8mm, 8.0mm, 9.0mm, 10.0mm, 11mm, 12mm and so on.

According to intensity level can be classified as: 1470MPa, 1570MPa, 1670MPa, 1770MPa and 1860MPa.

In accordance with the surface coating, high tensile PC steel wire can be classified as: no coating prestressed steel wire, prestressed epoxy coated steel wire and galvanized prestressed steel wire.

In accordance with the surface morphology can be classified as: light round prestressed steel wire, spiral rib (spiral ribbed or helix grooved) prestressed steel wire, the pressure wave (crimped) prestressed steel wire or nicks (indented) prestressed steel wire and so on.

In accordance with treatment process can be categorized as follows: cold-drawn prestressing steel wire (no slack performance requirements) and low relaxation prestressed steel wire.

Prestressed PC steel wire application: Prestressed concrete strand is used of prestressed concrete structure reinforced, such as large-span bridges on railway and highway, overhead crane beam, rock-soil anchoring project, multi-storey industrial buildings, stadiums, mines and etc. PE coated steel strand for prestressed concrete is suitable for large-span and large bays cast-in-place concrete floor, large load of precast beams and other special structure.

Many other steel wire and steel strand products:

Tensile Strength Requirements Nominal Diameter, mm(in) Tensile Strength, min, Mpa (psi) Type BA Type WA 4.88(0.192) 1725(250 000) 4.98(0.196) 1655(240 000) 1725(250 000) 6.35(0.250) 1655(240 000) 1655(240 000) 7.01(0.276) 1620(235 000) 1620(235 000) Yield Strength Requirements Nominal Diameter, mm(in) Internal StressMPa (psi) Minimum Stress at 1%  Extension, Mpa (psi) Type BA Type WA 4.88(0.192) 200(29 000) 1465(212 500) 4.98(0.196) 200(29 000) 1407(204 000) 1465(212 500) 6.35(0.250) 200(29 000) 1407(204 000) 1407(204 000) 7.01(0.276) 200(29 000) 1377(199 750) 1377(199 750) BS5896-1980 Diameter and deviation mm Nominal size m Nominal Weight g/m Minimum breaking load KN Nominal tensile strength Mpa 4.0±0.04
4.5±0.05
5.0±0.05
6.0±0.05
7.0±0.05 12.60
15.90
19.60
28.30
38.50 99.9
125
154
222
302 21.0
22.3
25.8
32.7
34.7
47.3
50.1
60.4
64.3 1670
1770
1620
1670
1770
1670
1770
1570
1670

Compacting thigh oil drilling special steel wire rope

Technical field

The utility model belongs to oil drilling special steel wire rope, particularly a kind of compacting thigh oil drilling steel wire rope that adopts compacting to produce.

Background technology

After last century the mid-1970s, each oil field of China begins the supporting steel wire rope of rig is carried out generalization, seriation, meets the API of American Petroleum Institute (API) standard-required substantially.The supporting construction of wire rope of rig has adopted the line contact.From nineteen ninety-five, be in a safe and reliable state all the time for making the oil field operation drilling line, drilling line is carried out the total quality upgrading, intensity rank is brought up to the EIP level by the IP level; Through 10 years development, along with the dark increase of drilling well and the variation of geological conditions, drillng operation proposes requirements at the higher level to the rupture pull force of steel wire rope.Owing to limited by drilling condition, the performance of linear contact lay wire rope can not be satisfied the demand.According to corrupted, the failure cause analysis of drilling line,, adopt compacting steel wire rope and compaction-strand steel wire rope can satisfy the needs of oil field development in conjunction with the new construction steel wire rope that ANSI/API-9A recommends.

Oil drilling steel wire rope main failure forms is wearing and tearing and tired, and the increase of at first wearing and tearing with speed increases, and the fatigue of steel wire rope is further quickened in the secondly shake of steel wire rope and shaking naturally.Drilling line is abominable because of service condition, and load is big, the rope speed height, and pulley quantity is many, and the rope footpath can not be too thick, so wearing and tearing are very fast.At present, China's oil field drilling engineering is still continued to use 6 * 19S structure steel wire rope, from steel wire rope development angle, compare with compaction-strand steel wire rope, obvious 6 * 19S structure exists many deficiencies in the drilling well sector application, shows that especially stability of structure, abrasion resistance specific pressure real shares steel wire rope differ bigger.

The utility model content

The purpose of this utility model provides a kind of compacting thigh oil drilling special steel wire rope that adopts compacting to produce, and its primary structure is three kinds of 6 * K19S-IWRC, 6 * K25F-IWRC, 6 * K26WS-IWRC.Steel wire rope is had good resistance to wear, performances such as antifatigue, shock resistance, whole rope rupture pull force are big, safe, Stability Analysis of Structures, long service life.

The technical scheme that the utility model is taked is:

Compacting thigh oil drilling special steel wire rope is made up of 6 outer layer strand and 1 steel core thigh, and outer layer strand is center line winding in the shape of a spiral with the steel core thigh, and outer layer strand adopts roll process or die drawing method compaction moulding, and the outer layer strand profile is round.Through online compacting the group thigh steel wire of outer layer strand is deformed, the gap reduces between the group strand steel wire, and the metallic area rate increases.Every outer layer strand is made up of 19～26 steel strands, and the structure of outer layer strand is: twisting has 2～3 layers of steel wire around 1 core wire, and described 2～3 layers of steel wire are respectively cover wire, inferior cover wire, filler wires and/or steel wire of internal layer.Described steel core thigh structure is 6 * 7-1 * 7.The method for expressing of described 6 * 7-1 * 7 is method for expressing of the thigh steel cable structure of national Specification, and this area stipulates that the technical staff can understand.

The cover wire of outer layer strand, inferior cover wire, filler wires, steel wire of internal layer and core wire are irregularly shaped.

The utility model compacting thigh oil drilling steel wire rope has been compared following advantage with ordinary steel rope:

1, has density metal coefficient height, the big characteristics of broken short value of thrust

The compaction-strand steel wire rope density metal has increased 9-12% than twisting strand steel wire rope, is designed to IPS level intensity, and actual steel wire rope intensity can surpass the intensity of EIP level.

2, whole abrasion resistance properties improves, and prolongs rope service-life

Compaction-strand steel wire rope surface metal area is big, contacting between steel wire rope and the race by original some contact becoming face contact, bearing under the same load condition, the suffered unit pressure of steel wire rope reduces, rubbing surface between steel wire rope and the pulley increases, frictional force reduces, and effectively prolongs steel wire rope and cylinder, pulley life-span.

3, steel cord structure stability improves, and anti-extrusion capability increases

For the compacting thigh, a group strand steel wire deforms, mix contact with being rendered as the line face by original line contact between the layer steel wire, because the contact area between the steel wire increases, compact stress between the group rope steel wire reduces, steel wire rope is being subjected under relatively large impact and the extruding situation, and steel cord structure is not yielding, has anti-preferably extruding and impact resistance.

4, security performance improves

With 6 * K26WS-IWRC-D38mm compaction-strand steel wire rope is example, and its safety coefficient is 1.25 times of 6 * 19S-IWRC-D38mm steel wire rope.

5, compacting thigh oil drilling steel wire rope has better antifatigue, shock resistance

Result of the test shows: its fatigue behaviour of steel wire rope by compacting thigh twisting is more than 1.2 times of twisting strand steel wire rope.

Description of drawings

Fig. 1 is 6 * K19S-IWRC compacting thigh oil drilling special steel wire rope cross sectional representation.

Fig. 2 is 6 * K25F-IWRC compacting thigh oil drilling special steel wire rope cross sectional representation.

Fig. 3 is 6 * K26WS-IWRC compacting thigh oil drilling special steel wire rope cross sectional representation.

Among the figure, 1. outer layer strand, 2. cover wire, 3. time cover wire, 4. filler wires, 5. steel wire of internal layer, 6. core wire, 7. steel core thigh.

The specific embodiment

With 3 kinds of different compacting thigh oil drilling special steel wire ropes of cross section is example, and the utility model is elaborated.

Embodiment 1: consult Fig. 1.6 * K19S-IWRC compacting thigh oil drilling special steel wire rope, diameter is D29mm.Be the outer layer strand 1 that is 9.20mm by 6 diameters) and 1 steel core thigh 7, once being twisted into diameter on crank closer is the 29mm steel wire rope, become rope before outer layer strand 1 through predeformation, outer layer strand 1 be center line winding in the shape of a spiral with steel core thigh 7.Realize the manufacturing of compacting thigh oil drilling steel wire rope 6 * K19S-IWRC thus.

Outer layer strand 1 adopts die drawing method compaction moulding.Every outer layer strand 1 structure is K19S (1-9-9), is made up of 19 steel wires.The structure of outer layer strand 1 is: twisting has 2 layers of steel wire around 1 core wire 6, is respectively cover wire 2 and steel wire of internal layer 5.The diameter of 9 cover wires 2 is 2.43mm; The diameter of 9 steel wire of internal layer 5 is 1.46mm; The diameter of 1 core wire 6 is 2.98mm.Outer layer strand 1 once property twisting, compaction moulding on strander.Outer layer strand 1 profile is round.

Steel core thigh 7 is that the structure that 1 diameter is 11.7mm is the steel wire rope of 6 * 7-1 * 7.

6 * K19S-IWRC compacting thigh oil drilling special steel wire rope, density metal is big, have good resistance to wear, antifatigue, shock resistance, be that the twisting strand steel wire rope is more than 1.5 times service life.

Embodiment 2: consult Fig. 2.6 * K25F-IWRC compacting thigh oil drilling special steel wire rope, diameter is D32mm, be to be 10.50mm outer layer strand 1 and 1 steel core thigh 7 by 6 diameters, once being twisted into diameter on crank closer is the 32mm steel wire rope, outer layer strand 1 is through predeformation before becoming rope, and outer layer strand 1 is center line winding in the shape of a spiral with steel core thigh 7.

Outer layer strand 1 adopts the roll process compaction moulding.Every outer layer strand 1 structure is K25F (1-6-6F-12), is made up of 25 steel wires.The structure of outer layer strand 1 is: twisting has 2 layers of steel wire around 1 core wire 6, is respectively cover wire 2 and steel wire of internal layer 5; 6 diameter 1.00mm filler wireses 4 are arranged in 6 spaces between cover wire 2 and steel wire of internal layer 5.The diameter of 12 cover wires 2 is 2.14mm; The diameter of 6 steel wire of internal layer 5 is 2.38mm; The diameter of 1 core wire 6 is 2.56mm.Outer layer strand 1 once property twisting, compaction moulding on strander.Outer layer strand 1 profile is round.

Steel core thigh 7 is that the structure of 1 diameter 12.9mm is the steel wire rope of 6 * 7-1 * 7.

Embodiment 3: consult Fig. 3.6 * K26WS-IWRC compacting thigh oil drilling special steel wire rope, diameter is D32mm, be to be 10.50mm outer layer strand 1 and 1 steel core thigh 7 by 6 diameters, once being twisted into diameter on crank closer is the 32mm steel wire rope, outer layer strand 1 is through predeformation before becoming rope, and outer layer strand 1 is center line winding in the shape of a spiral with steel core thigh 7.

Outer layer strand 1 adopts the roll process compaction moulding.Outer layer strand 1 structure is K26WS (1-5-5+5-10), is made up of 26 steel wires.The structure of outer layer strand 1 is: the twisting steel wire that haves three layers around 1 core wire 6 is respectively cover wire 2, inferior cover wire 3 and steel wire of internal layer 5.The diameter of 10 cover wires 2 is 2.47mm; Inferior cover wire 3 by the big silk of 5 diameter 1.80mm and 5 diameters be little of 1.42mm alternately; The diameter of 5 steel wire of internal layer 5 is 1.50mm; The diameter of 1 core wire 6 is 1.12mm.Outer layer strand 1 once property twisting, compaction moulding on strander.Outer layer strand 1 profile is round.

Steel core thigh 7 is that the structure that 1 diameter is 12.8mm is the steel wire rope of 6 * 7-1 * 7.

According to national Specification, described three kinds of compacting thigh oil drilling special steel wire rope structure method for expressing are: 6 * K19S-IWRC, 6 * K25F-IWRC, 6 * K26WS-IWRC.

Steel core thigh 7 structures are: 6 * 7-1 * 7, and represent steel core thigh 7 to form by 6 outer layer strand and a core thigh; Per share have 7 steel wires, and there is 1 steel wire at per share center.

According to oil drilling steel wire rope handling characteristics, our company has developed and has adapted to the compacting thigh oil steel wire rope that China's oil drilling is used, and through the on-the-spot use of user, obtains good effect, and the life-span prolongs more than 1.5 times than 6 * 19S structure steel wire rope.

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