The characteristics of concrete prestressed pipes refer to prestressed steel cylinder concrete pipes

Prestressed concrete cylinder pipe (PCCP) refers to a water pipeline made by winding a circumferential prestressed steel wire on a high-strength concrete core with a steel cylinder, and then spraying a dense cement mortar protective layer on it. It is a composite pipe composed of thin steel plate, high-strength steel wire and concrete, which fully and comprehensively exerts the tensile strength, easy sealing of steel and the compressive and corrosion resistance of concrete, and has the characteristics of high sealing, high strength and high impermeability.

Concrete prestressed pipe (self-stressing concrete pipe) is a kind of concrete pipe that does not need to be prestressed by tensioning itself. The structure is to arrange annular prestressed steel bars in the pipe wall, and then pour self-expanding concrete. The concrete hardens and expands, and the annular prestressed steel bar stretches outward, and the reaction force of the prestressed steel bar on the concrete produces prestress.

Prestressed concrete pipe and prestressed steel cylinder concrete pipe are two different pipes; The core of the prestressed steel cylinder concrete pipe (referred to as PCCP pipe) has a layer of thin-walled steel cylinder (steel plate thickness δ to form a composite pipe with steel plate and prestressed concrete. Therefore, PCCP pipe can be made into a relatively large pipe diameter, which has better impermeability and pressure resistance than prestressed concrete pipe.

That's pretty much what it means.

Summary. Hello, the use of prestressed concrete-filled steel tube pipes (1) single-layer and multi-storey industrial plant columns.

2) All kinds of equipment structures (supports) columns, such as the lower pillar of the platform, are often axial compression members, and the load is often large, so steel pipe coagulation is often used.

3) Heavy-duty columns, such as underground railway platform columns, are mostly made of concrete-filled steel tubes.

4) Power transmission tower.

5) Pile, concrete-filled steel tube pile is more suitable for the pile foundation of buildings on soft soil foundation.

6) When the span of the bridge and arch bridge is very large, the arch rib will bear a large axial pressure, and it is more reasonable to use concrete-filled steel tubular components.

7) High-rise, so far, there are nearly 100 high-rise and super high-rise buildings that use steel tube concrete in whole or in part.

The use of prestressed concrete-filled steel tube pipes.

Hello, the use of prestressed concrete-filled steel tube pipes (1) single-layer and multi-storey industrial plant columns. (2) various equipment structures (supports) columns, such as the lower pillar of the platform are often axial compression members, and the load is often larger, so the steel pipe concrete (3) heavy-duty column, such as the underground return railway platform column, mostly adopts the steel pipe concrete column. 4) Power transmission tower.

5) Pile, concrete-filled steel tube pile is more suitable for the pile foundation of buildings on soft soil foundation. 6) When the span of the bridge and arch bridge is very large, the arch rib will bear a large axial pressure, and it is more reasonable to use concrete-filled steel tubular components. (7) High-rise, so far, there are nearly 100 high-rise and super high-rise buildings that are all or partially made of steel tube concrete.

It combines the advantages of concrete-filled steel tube with the advantages of prestressing technology to form a prestressed concrete-filled steel tube composite component or structure, so that the application range of concrete-filled steel tube structure is no longer limited to axial compression short columns, but can be extended to the tensile or bending parts of the structure. For example, the prestressed concrete-filled steel tube beam can make the concrete-filled steel tube sliding sensitive to the flexural components: another example is the prestressed brace friendly branch column, which can further improve the stable bearing capacity of the steel tube concrete to let the collapsed soil; Prestressed concrete-filled steel tube can also be used for the lower chord and tension web of space truss, the horizontal tie rod of long-span arch bridges and the anchor rod of retaining walls. In addition, the prestressed steel pipe concrete structure is also a beneficial attempt to improve the dynamic performance of the structure, reduce the influence of the sag of the cable, and improve the durability and corrosion resistance of the cable.

1. The definitions are different.

Reinforced concrete, often referred to as reinforced concrete in ridge engineering, refers to a combination of materials composed of reinforced mesh, steel plates or fibers in concrete to work together to improve the mechanical properties of concrete.

Prestressed concrete is to make up for the phenomenon of premature cracks in concrete, before the component is used (loaded), a pre-pressure is given to the concrete, that is, in the tensile area of the concrete touching field, the steel bar is stretched by the method of artificial afterburner, and the retraction force of the steel bar is used to make the concrete tensile area under pressure in advance.

This stored pre-pressure, when the member bears the tensile force generated by the external load, first offset the pre-pressure in the concrete in the tension zone, and then with the increase of the load, the concrete is tensile only, which limits the elongation of the concrete, delays or does not make the crack appear, this is called prestressed concrete.

2. The working principle is different.

The reason why reinforced concrete can work together is determined by its own material properties. First of all, steel and concrete have approximately the same linear expansion coefficient, and will not be overstressed due to different environments. Secondly, there is good adhesion between the steel bar and the concrete, and the alkaline environment provided by the calcium hydroxide in the concrete forms a passivation protective film on the surface of the steel bar, so that the steel bar is less resistant to corrosion than the neutral and acidic environment.

Precompressive stress is used to reduce or offset the concrete tensile stress caused by the load, so as to control the tensile stress of the structural component in a small range, or even in a compressive state, so as to delay the emergence and development of concrete cracks, so as to improve the crack resistance and stiffness of the component.

3. The characteristics are different.

The amount of stress bars in reinforced concrete is usually very small, ranging from 1% (mostly in beams and slabs) to 6% (mostly in columns) of the cross-sectional area of the component. The cross-section of the reinforcement is round.

Prestressed concrete has good crack resistance and high stiffness. Save material and reduce dead weight. The vertical shear force and main tensile stress of the concrete beam can be reduced. Improve the stability of compressive members. Improve the fatigue resistance of components.

1.The prestressed concrete pipe pile is also known as the large pipe pile, and the production method is as follows: according to the design, the reinforcement cage composed of non-prestressed main steel bar and stirrups in the pipe wall is made; The reinforcement cage is connected with the metal connector of the pile head, and various embedded parts are placed; The steel cage is loaded into the steel mold, and concrete is poured into the steel mold to complete the prototype of the pile body; The steel mold that is equipped with the rudimentary shape of the pile body rotates around the pile shaft, and the concrete is centrifugally compacted and formed; Curing and demoulding.

2.Concrete pipes are divided into four categories: plain concrete pipes, ordinary reinforced concrete pipes, self-stressed reinforced concrete pipes and prestressed concrete pipes.

The method of making prestressed concrete pipe is basically the same as that of concrete pipe.

Differences:1There is no steel bar in the concrete pipe, which belongs to the plain concrete pipe, and there are steel bars in the prestressed reinforced concrete pipe.

2.The steel bars in the prestressed reinforced concrete pipe need to be pre-tensioned, and the concrete should be poured after the stress reaches a certain design or specification requirement. The concrete stops tensioning after reaching a certain strength requirement. Such tubes have high flexural tensile strength.

In the prestressed concrete pipe, the stressed steel bar is a prestressed tendon, and prestress is applied and tensioned.

The stressed tendons in reinforced concrete pipes are ordinary steel bars, without tension and without prestress.

The former is more economical and can give full play to the mechanical properties of concrete and steel bars. The advantages are the same as those of prestressed members.

The prestressed concrete pipe makes full use of the properties of the high tensile strength of the steel bar, so it is more steel-saving;

The tensile stress pre-applied in the steel bar makes the concrete maintain the precompressive stress for a long time, which is conducive to the pipe is not easy to crack when it is subjected to unexpected action during transportation and installation, and its crack resistance is good;

Due to the different manufacturing processes of prestressed concrete pipes, the pipe wall can be made thinner, so it is lighter.

Prestressing is the tensile of the steel bar when making the reinforced concrete pipe.

The reinforced concrete pipe reinforcement is not stretched.

The former makes the component not crack under the normal service load, or the crack opens later, and the width of the crack development is smaller.

Concrete tensile members, flexural members, large eccentric compression members, etc., all exist in tension zones under various loads. When the load is not too large, cracks will appear in the above-mentioned members.

The ultimate tensile strain value of concrete ctu is approximately, then the value of the reinforcement stress at cracking is about:

s=esεs=esεctu=2×105×

Another major disadvantage of reinforced concrete elements is that they cannot be reinforced with high-strength steel bars.

The last point is that the effect of improving the strength grade of concrete on the crack resistance of the component is also extremely limited, because the ultimate tensile strain of each grade of concrete is not much different; Increasing the cross-sectional size of the component can improve the crack resistance, but the concrete required is more, and the component is self-weighted.

The so-called prestressed concrete is to apply compressive stress to the tensile zone of the use stage in advance in the production stage before the concrete component bears the use load, resulting in an artificial stress state.

When the tensile stress is generated by the member under the use load, the precompressive stress of the concrete should be offset first, and then with the increase of the load, the tensile stress of the concrete in the tension zone will be generated. Therefore, the appearance and development of concrete cracks can be delayed to meet the requirements of use. This kind of structural component that exerts compressive stress to the concrete in the tension zone before the structural member bears the load is called a prestressed concrete member.

The prestressed pipe is often referred to as the "hole".

1.Retention of the orifice.

1) Steel pipe core-pulling method. This method can only leave straight channels.

2) Hose core-pulling method. It can leave not only straight and curved holes.

3) Pre-embedded bellows method. The metal bellows are made of steel strips that are rolled by a special pipe making machine. The bellows does not pull out after being buried in the concrete, and has good adhesion to the concrete.

2. Tensioning of prestressed tendons.

The tensioning procedure of the post-tensioned tendon is related to the type of anchor used, and in order to reduce the loss of relaxation stress, the tensioning procedure is generally the same as that of the pre-tensioning method. Things to pay attention to when stretching:

1) In order to reduce the stress loss caused by the friction between the prestressed tendon and the reserved hole wall, the linear prestressed tendon with a general component length of less than 24m can be tensioned at one end.

2) For components equipped with multiple prestressed tendons, they should be tensioned symmetrically in batches.

3) The components of horizontal overlapping pouring should be stretched layer by layer layer after top, and the tensile force can be increased layer by layer to make up for the prestress loss, and the control stress value of the bottom component should be guaranteed not to exceed the specified limit.

4) when the prestressed tendon is stretched, it is often necessary to take the method of over-tensioning to make up for a variety of prestress losses, for this reason, the tensile stress of the prestressed tendon is larger, and sometimes it may exceed the specified limit, at this time, the following method can be adopted to solve: first take the same tensile value, and then reset to make up; The prestress is established in two stages, that is, all the prestresses are stretched to a certain value (e.g. 90), and then the second tension is reached to the control value.

5) when using the stress control method tensioning, should check the elongation value of the prestressed tendon, such as the actual elongation value is greater than the calculated elongation value 10 or less 5, should suspend the tension, after taking measures to adjust, can continue to tension.

3 Hole grouting.

After the tendon is stretched, the channel grouting should be carried out immediately to prevent the prestressed tendon from corroding, and at the same time increase the crack resistance and durability of the structure.

In addition to meeting the requirements of strength and cohesion, the mortar for grouting should also have greater fluidity and less compressibility and water leakage. Therefore, the grouting should be made of ordinary Portland cement with a grade of not less than that of cement slurry, and the grouting must be carried out continuously and completed at one time.

The prestressed pipeline is the PCCP pipe, which can be used for water supply and drainage. China Pipeline Business Network has a detailed introduction.

First, the reference is different.

1. Self-stressed concrete pipe: It is a cementitious material with large expansion rate made by grinding a certain amount of aluminate cement clinker and gypsum dihydrate.

2. Prestressed concrete pipe: in order to make up for the phenomenon of premature cracks in concrete, before the component is used (loaded), a pre-pressure is given to the concrete, that is, in the tensile area of the concrete, the steel bar is stretched by the method of artificial afterburner, and the retraction force of the steel bar is used to make the concrete tensile area under pressure in advance.

Second, the principle is different.

1. Self-stressed concrete pipe: Aluminate self-stressed cement has a high self-stress value, and cement pipes of different calibers can be produced according to different grades of aluminate self-stressed cement. The process performance is good, as long as the production is carried out according to the ministry standard, the product with roughly the same performance can be obtained.

The aluminate self-stressed cement stone structure is dense, and with the increase of the hydration period, the cement stone structure will become more and more dense.

2. Prestressed concrete pipe: precompressive stress is used to reduce or offset the concrete tensile stress caused by the load, so as to control the tensile stress of the structural component in a small range, or even in a compressive state, so as to delay the emergence and development of concrete cracks, so as to improve the crack resistance and stiffness of the component.

Third, the characteristics are different.

1. Self-stressed concrete pipe: mainly used for self-stressed steel bar (steel wire mesh) concrete (mortar) pressure pipe.

2. Prestressed concrete pipe: good crack resistance and high stiffness. Because the prestress is applied to the component, the appearance of cracks is greatly delayed, and under the action of the use load, the cracks can not appear, or the cracks are postponed, so the stiffness of the component is improved, and the durability of the structure is increased.