Linear variable-folding line pre-tensioning device and construction method

Abstract

The application discloses a linear-to-folding-line pre-tensioning device and a construction method. In order to overcome the problems of difficult reduction of the prestress loss of a folding-line pre-tensioning prestressed concrete beam in a prestress tensioning process and low tensioning efficiency, the application adopts a turning shaft capable of reducing the turning angle of prestressed steel strands, reduces the prestress loss by reducing the turning angle, and simultaneously adopts an external turning device including a sliding rail and a tensioning sliding block to reduce the construction difficulty and increase the tensioning efficiency.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering construction, and more particularly to a pre-tensioning device and construction method for converting a straight line into a broken line. Background Technology

[0002] Pre-tensioning is a method of constructing prestressed concrete members by pre-tensioning the prestressed steel bars before pouring the concrete. Prestress is achieved through the recoil of the prestressed steel bars on the concrete beam during shrinkage. In pre-tensioned structures, the prestress is transferred by the bond force between the prestressed tendons and the concrete.

[0003] The fabrication of prestressed members using the polygonal pre-tensioning method generally requires equipment such as a deflector, tensioning platform, reaction wall, jacks, and clamps. By installing a deflector on the tensioning platform, the prestressed steel strands passing through the deflector are tensioned, causing them to bend and thus forming polygonal prestress. The deflector is a key component for applying polygonal prestress, serving to bend and position the prestressed steel strands. Besides bending, frictional resistance is generated at the contact section between the deflector and the prestressed steel strands during tensioning, leading to prestress loss. In the fabrication of concrete beams, prestress loss is a significant factor affecting beam quality; therefore, reducing prestress frictional loss during the prestressing tensioning process of polygonal prestressed concrete beams has become an urgent problem to be solved.

[0004] For example, a "tensioning platform for pre-tensioned, polygonal prestressed precast beams" disclosed in Chinese patent literature, publication number CN205969481U, includes a force transmission column, a gravity base, a precast beam, and a tensioning crossbeam. The precast beam is placed on top of the force transmission column, with gravity bases connected to both ends. A steel box inverted column is installed on top of the gravity base, and a tensioning crossbeam is welded to the left end of the steel box inverted column. The tensioning crossbeam has reserved space for the passage of polygonal prestressed steel strands. The steel box inverted column extends into the gravity base and is connected to the gravity base as a whole through anchor bolts. The steel box inverted column is made of steel and filled with micro-expansion concrete. The force transmission column has multiple reserved slots in a 2-meter module, which also serve as the bottom formwork for the precast beam. This invention satisfies the tensioning of pre-tensioned, polygonal prestressed precast beams of various spans and allows for the simultaneous prefabrication of multiple beams. Furthermore, this invention is reusable, effectively reducing beam construction costs, saving construction time, and ensuring beam quality and durability. This patent effectively solves the problem of tensioning prestressed precast beams with various spans using prestressed zigzags, but it does not solve the problem of prestress loss, and the operation is relatively complicated with low tensioning efficiency. Summary of the Invention

[0005] This invention mainly addresses the problems of excessive prestress loss when applying prestress to prestressed steel strands, and the overly cumbersome operation, low work efficiency, and low safety in existing technologies. It provides a pre-tensioning device and construction method for straight-to-zigzag wires.

[0006] The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions:

[0007] This invention includes an internal steering mechanism and an external steering mechanism. The internal steering mechanism is equipped with several steering shafts and insertion holes to reduce the steering angle of the prestressed steel strands. The external steering mechanism includes a slide rail and a tensioning slider, with the tensioning slider engaging with the slide rail. The steering shafts that reduce the steering angle of the prestressed steel strands reduce the prestress loss of the prestressed steel strands. The design of the slide rail and tensioning slider structure of the external steering mechanism solves the problems of cumbersome construction methods and low safety.

[0008] Preferably, the steering shaft includes an inner arc-shaped surface and an outer arc-shaped surface. During construction, the steering shaft is inserted into a socket, and the outer arc-shaped surface contacts the prestressed steel strand. The shape and size of the socket are adapted to the steering shaft. Compared with the prior art, the design of the outer arc-shaped surface increases the contact area between the prestressed steel strand and the steering shaft, and reduces the steering angle of the prestressed steel strand, thereby reducing prestress loss.

[0009] Preferably, the arc length of the outer arc surface is greater than that of the inner arc surface, and the center of the inner arc surface of the steering shaft and the center of the outer arc surface of the steering shaft are at the same point. The design of the inner and outer arc surfaces corresponding to each other ensures that the force applied by the steering shaft to the inner steering gear is sufficiently dispersed and will not be concentrated at certain points, effectively ensuring that no quality problems or safety accidents occur during construction.

[0010] Preferably, the outer arc surface of the steering shaft is positioned facing both ends of the prestressed steel strand. The orientation of the steering shaft conforms to the requirements of actual construction and makes it easier to tension the prestressed steel strand horizontally, without needing to consider the specific position of the steering shaft.

[0011] Preferably, the slide rail is provided with a limiting structure, which includes a plurality of limiting holes and limiting rods. The distance between the limiting holes is equal to the width of the tensioning slider, and the height of the limiting holes is set to meet the requirements for applying conventional internal stress. The limiting rods are inserted into the limiting holes. The design of the limiting structure ensures that when the slider is lifted, it will not exceed the limited position, thereby affecting the magnitude of the internal stress to be applied. At the same time, since the distance between the limiting holes is equal to the width of the tensioning slider, the limiting structure can also fix the position of the slider.

[0012] Preferably, the contact surface between the tensioning slider and the slide rail is equipped with strain gauges and pressure sensors. The design of the strain gauges and pressure sensors ensures the accuracy of internal stress application during construction.

[0013] Preferably, the slide rail is curved with its center as the steering axis, and the tensioning slider has an opening for fixing the prestressed steel strand. The curvature of the slide rail ensures that the prestressed steel strand will not move, thus preventing it from affecting the accuracy of prestress application and causing prestress loss.

[0014] This invention includes a pre-tensioning construction method for transforming straight lines into polygonal lines, the construction method steps being as follows:

[0015] S1. Install the internal steering gear and the external steering gear on the steel pedestal.

[0016] S2. Pass the prestressed steel strands through the steering shaft of the internal steering mechanism to achieve straight horizontal tensioning of the prestressed steel strands.

[0017] S3. Fix both ends of the prestressed steel strand to the tensioning slider of the external steering mechanism, and raise the tensioning slider along the arc-shaped slide rail to the designated position. The construction method is simple, efficient, and highly safe.

[0018] Preferably, for S3, before raising the tensioning slider, the limiting rod is inserted into the corresponding limiting hole that meets the required raising height. Inserting the limiting rod into the appropriate limiting hole can prevent excessive prestress from being applied to the prestressed steel strand.

[0019] Preferably, for S3, when raising the tensioning slider, the magnitude of the prestress is determined based on the pressure value given by the pressure sensor, and raising stops when the required prestress is reached. The setting of the pressure sensor effectively ensures the accuracy of the applied prestress.

[0020] The beneficial effects of this invention are:

[0021] 1. The structural design of the steering shaft on the inner steering gear reduces the steering angle of the prestressed steel strand, making the steering of the prestressed steel strand smoother, thereby reducing the loss of prestress applied to the prestressed steel strand. At the same time, the structural design of the inner ring of the steering shaft on the inner steering gear ensures that the force distribution of the steering shaft on the inner steering gear is more uniform, reducing the wear on the inner steering gear and effectively improving the safety of construction.

[0022] 2. The structural design of the slider rail on the external steering gear makes the construction method more convenient and simple. In addition, the limit rod is set on the rail to prevent the slider from sliding to a place other than the set position, ensuring the accuracy and safety of construction and effectively increasing work efficiency. Attached Figure Description

[0023] Figure 1 This is a side view of a linear-to-zigzag pre-tensioning device under horizontal tensioning conditions, as per this invention patent.

[0024] Figure 2This is a side view of the tensioning condition of a linear-to-zigzag pre-tensioning device according to the present invention patent.

[0025] Figure 3 This is a structural comparison diagram of an internal steering system and a traditional steering system according to the present invention.

[0026] Figure 4 This is a front view of the assembly of the arc-shaped track and the tensioning end slider of this invention patent.

[0027] Figure 5 This is a side view of the assembly of the arc-shaped track and the tensioning end slider of this invention patent.

[0028] In the diagram: 1. Prestressed steel strand, 2. Inner steering gear, 3. Tensioning slider, 4. Outer steering gear base, 5. Steel base, 6. Slide rail, 101. Left section zigzag prestressed steel strand 1, 102. Middle section zigzag prestressed steel strand 1, 103. Right section zigzag prestressed steel strand 1, 201. Traditional steering shaft, 202. Arc-shaped steering shaft, 301. Pressure sensor, 303. Steel strand fixing hole, 601. First slide rail, 602. Second slide rail, 603. Limiting hole, 604. Limiting rod. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0030] Example:

[0031] This embodiment describes a pre-tensioning device and construction method for converting a straight line into a polygonal line, such as... Figure 1 As shown, it includes prestressed steel strand 1, inner steering mechanism 2, tensioning slider 3, outer steering mechanism base 4, steel base 5, and slide rail 6.

[0032] A steel base 5 is laid on a flat surface. Two outer steering gear bases 4 are respectively set at both ends of the steel base 5 and fixed. Arc-shaped slide rails 6 are installed on the outer steering gear bases 4, with the arc surface of the slide rails 6 facing both ends. The center of the arc surface of the slide rail 6 is the steering gear. Tensioning sliders 3 are snapped onto the slide rails 6, located at the bottom of the slide rails 6. Inner steering gears 2 are fixedly installed at two one-third points of the steel base 5. Steel strands pass through the two inner steering gears 2, and both ends of the steel strands are fixed to the tensioning sliders 3.

[0033] like Figure 2 As shown, in Figure 1Based on this, it also includes a left-section zigzag prestressed steel strand 101, a middle-section zigzag prestressed steel strand 102, and a right-section zigzag prestressed steel strand 103. The left end of the left-section zigzag prestressed steel strand 101 is connected to the left-side tensioning slider 3, and the right end is connected to the left-side inner steering mechanism 2. The left end of the middle-section zigzag prestressed steel strand 102 is connected to the left-side inner steering mechanism 2, and the right end is connected to the right-side inner steering mechanism 2. The left end of the right-section zigzag prestressed steel strand 103 is connected to the right-side inner steering mechanism 2, and the right end is connected to the right-side tensioning slider 3. The tensioning slider 3 is located at the top of the slide rail 6.

[0034] like Figure 3 As shown, the steering shaft includes a conventional steering shaft 201 and an arc-shaped steering shaft 202. The conventional steering shaft 201 is cylindrical, while the arc-shaped steering shaft 202 is cylindrical, consisting of an outer arc surface, an inner arc surface, and two side planes. Comparing the conventional steering shaft 201 and the arc-shaped steering shaft 202, the radius of the arc-shaped steering shaft 202 is much larger than that of the conventional steering shaft 201. Therefore, the steering angle produced when using the arc-shaped steering shaft 202 is smaller.

[0035] The prestress loss of the steering gear can be expressed as the difference between the tension at the driving end and the tension at the driven end, that is:

[0036] (1)

[0037] In the formula: : Prestress loss; : Active end tension; : Passive end tension.

[0038] The prestress loss is mainly due to frictional resistance, namely:

[0039] (2)

[0040] In the formula: Steering gear friction coefficient; : The resultant force on the steering gear.

[0041] Steering gear resultant force Steering angle Active end tension and passive end tension The relationship between the three can be approximated as follows:

[0042] (3)

[0043] According to equations (1) to (3), the prestress loss caused by the steering gear can be obtained as follows:

[0044] (4)

[0045] As can be seen from the above analysis, the prestress loss of the steering gear is mainly related to the steering angle, the driving end tension, and the steering gear friction coefficient. The larger the steering angle, the larger the friction coefficient and the larger the driving end tension, the greater the prestress loss of the steering gear. Therefore, the setting of the arc-shaped steering shaft reduces the steering angle and reduces the prestress loss.

[0046] like Figure 4 As shown, the structure includes a pressure sensor 301, a steel strand fixing hole 303, a first slide rail 601, a second slide rail 602, and a limiting rod 604. The first slide rail 601 and the second slide rail 602 are two parallel arc-shaped slide rails with identical shapes and structures. The pressure sensor 301 is positioned between the tensioning slider 3 and the first slide rail 601. The steel strand fixing hole 303 is located at the center of the tensioning slider 3, also within the gap between the first slide rail 601 and the second slide rail 602. A protrusion is located at the center of the back of the tensioning slider 3, and this protrusion is fitted into the gap between the first slide rail 601 and the second slide rail 602. The limiting rod 604 passes through both the first slide rail 601 and the second slide rail 602.

[0047] like Figure 5 As shown, it also includes limiting holes 603, which are evenly arranged on the first slide rail 601 and the second slide rail 602 for inserting the limiting rod 604.

[0048] Implementation process of the present invention:

[0049] First, an internal steering mechanism 2 and an external steering mechanism are arranged on the steel pedestal. The prestressed steel strand 1 is then passed through the internal and external steering mechanisms. Next, the prestressed steel strand 1 is tensioned horizontally in a straight line. After the load tension reaches 100%, the prestressed steel strand 1 is rotated at a certain angle around the internal steering mechanism 2 to achieve zigzag tensioning. After the rotation is completed, the prestressed steel strand 1 is anchored, and then concrete is poured. The specific straight tensioning process is as follows: Figure 1 As shown. After the concrete has cured to the specified strength, the tensioning slider is released, the prestressed steel strand 1 is cut, and the direct connection between the lower part of the internal steering gear 2 and the steel platform is disconnected, forming a prestressed concrete structure with straight-line variable-angle reinforcement. Compared with the traditional variable-angle tensioning, the use of a straight-line variable-angle prestressing device and construction method greatly reduces the friction between the steel strand and the steering shaft during the tensioning process, thus reducing friction loss and achieving efficient tensioning.

[0050] It should be understood that the embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A pre-tensioning device for converting a straight line into a polygonal line, comprising an internal steering mechanism and an external steering mechanism, characterized in that, The internal steering mechanism is provided with several steering shafts and insertion holes to reduce the steering angle of the prestressed steel strands. The external steering mechanism includes a slide rail and a tensioning slider, which is engaged with the slide rail. A limiting structure is provided on the slide rail, which includes several limiting holes and limiting rods. The distance between the limiting holes is equal to the width of the tensioning slider. The height of the limiting holes is set to meet the requirements for applying conventional internal stress. The limiting rods are inserted into the limiting holes.

2. The pre-tensioning device for converting a straight line into a polygonal line according to claim 1, characterized in that, The steering shaft includes an inner arc-shaped surface and an outer arc-shaped surface. During construction, the steering shaft is inserted into a socket, and the outer arc-shaped surface contacts the prestressed steel strand. The shape and size of the socket are adapted to the steering shaft.

3. The pre-tensioning device for converting a straight line into a polygonal line according to claim 2, characterized in that, The arc length of the outer arc surface is greater than that of the inner arc surface, and the center of the inner arc surface of the steering shaft and the center of the outer arc surface of the steering shaft are at the same point.

4. The pre-tensioning device for converting a straight line into a polygonal line according to claim 1, characterized in that, The outer arc surface of the steering shaft is positioned towards both ends of the prestressed steel strand.

5. The pre-tensioning device for converting a straight line into a polygonal line according to claim 1, characterized in that, The contact surface between the tensioning slider and the slide rail is equipped with strain gauges and pressure sensors.

6. The pre-tensioning device for converting a straight line into a polygonal line according to claim 1, characterized in that, The slide rail is curved with the center of the circle being the steering axis, and the tensioning slider has an opening for fixing the prestressed steel strand.

7. A pre-tensioning construction method for straight-line to polygonal-line structures, employing the pre-tensioning device for straight-line to polygonal-line structures according to any one of claims 1-6, characterized in that... S1. The internal steering gear and the external steering gear are arranged on the steel pedestal; S2. Pass the prestressed steel strand through the steering shaft of the internal steering mechanism to achieve straight horizontal tensioning of the prestressed steel strand; S3. Fix both ends of the prestressed steel strand to the tensioning slider of the external steering device, and lift the tensioning slider along the arc-shaped slide rail to the designated position.

8. The pre-tensioning construction method for a straight-line to polygonal-line structure according to claim 7, characterized in that, For S3, before raising the tensioning slider, insert the limiting rod into the corresponding limiting hole that meets the required lifting height.

9. The pre-tensioning construction method for a straight-line to polygonal-line structure according to claim 7, characterized in that, For S3, when raising the tensioning slider, the prestress magnitude is determined based on the pressure value given by the pressure sensor, and the raising is stopped when the prestress requirement is reached.

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