A limit plate for reducing prestress shrinkage loss

Abstract

The present invention discloses a limit plate for reducing prestressed retraction loss, comprising a sleeve, an inner cover plate, an elastic recovery member and an auxiliary anchor. The rear end face of the sleeve, the inner cover plate and the auxiliary anchor are respectively provided with holes for steel strands to pass through, and the holes of each component are correspondingly connected front and back. The inner cover plate can be slidably installed in the sleeve and divides the internal space of the sleeve into a front chamber and a rear chamber. The auxiliary anchor is a block, which is installed in the front chamber through the front end opening of the sleeve and fixedly connected to the inner cover plate. The hole of the auxiliary anchor has a limit structure for limiting the backward movement of the working clip of the working anchor. The elastic recovery member is arranged in the rear chamber and its two ends are respectively in contact with the rear end face of the sleeve and the inner cover plate. During the use of the present invention, the working clip is withdrawn part of the working anchor hole in advance, and when the jack returns oil, it can be anchored in advance, which can effectively reduce the retraction amount of the steel strand, thereby achieving the purpose of reducing the prestressed retraction loss.

Description

Technical Field

[0001] The invention relates to a limiting plate for reducing prestressed steel strand shrinkage loss, which is applied to the post-tensioning construction of prestressed steel strands of highway bridges. Background Art

[0002] At present, the post-tensioning construction of prestressed steel strands at home and abroad mainly uses hydraulic jacks. The tensioning is carried out by the tool anchor installed at the rear end of the jack and the working anchor reserved at the end of the beam body. The tool anchor and the working anchor are respectively provided with tool clips and working clips. The tool clips and working clips are clamped on the steel strand. When the jack supplies oil and increases pressure, the jack drives the tool clip to clamp the steel strand away from the beam body to achieve the stretching of the steel strand. A limit plate is provided between the jack and the working anchor to limit the displacement of the working clip during the tensioning of the steel strand. When the steel strand is tensioned, the working clip moves backward to the bottom of the groove of the limit plate following the stretching of the steel strand, and loses its restraining effect on the steel strand. When the jack tensions the steel strand to the designed control tension force, at the moment when the oil is returned to relax the steel strand, the steel strand undergoes elastic contraction, and the working clip moves into the hole of the working anchor following the contraction of the steel strand, and then anchors the steel strand.

[0003] The reason why the anchor has self-anchoring performance is that there is a gap between the limit plate equipped at the front end of the jack and the working anchor. Therefore, during the tensioning process, after the working clip moves back a certain distance, it will be blocked by the limit plate and cannot move back any further. When the steel strand is tensioned to the specified stress and held for a period of time, the electric oil pump returns to zero. When the anchoring operation is performed, the steel strand that was originally stretched and stretched will immediately retract due to the loss of tensioning force, and drive the working clip to drag the working clip into the anchor hole of the working anchor. Due to the tapered fit between the working clip and the anchor hole of the working anchor, the more the steel strand retracts during the retraction process, the tighter it is anchored by the working clip that it drags in, until it can no longer retract, and the steel strand has been anchored. The retraction displacement of the working clip will cause the tensioning force of the steel strand to decrease, resulting in the loss of the anchor prestress retained in the beam body.

[0004] In the post-tensioning construction of prestressed steel strands, first put the steel strands in the reserved holes of the concrete beam, then install the working anchor, working clip, limit plate, jack, tool anchor and tool clip in order from front to back, and then tension the steel strands. The traditional limit plate used for limiting the working anchor is relatively simple. When the jack supplies oil or returns oil, the limit plate relies on the friction provided by the steel strand to drive the working clip to retreat or retract. In order to prevent the friction between the inner teeth of the working clip and the steel strand from being too large, the working clip will retract to a certain extent during the self-anchoring process. However, the retraction of the working clip will cause a decrease in the effective prestress under the anchor. Summary of the invention

[0005] The object of the present invention is to provide a limiting plate which has a simple structure, low cost and can reduce the shrinkage of steel strands and thus reduce the prestress shrinkage loss.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical measures: a limit plate for reducing prestressed shrinkage loss, characterized in that it includes a sleeve, an internal cover plate, an elastic return member and an auxiliary anchor, the rear end face of the sleeve, the internal cover plate and the auxiliary anchor are respectively provided with channels for the steel strand to pass through, and the channels of each component are correspondingly connected front and back, the internal cover plate can be slidably installed in the sleeve and divides the internal space of the sleeve into a front chamber and a rear chamber, the auxiliary anchor is a block, which is installed in the front chamber through the front end opening of the sleeve and is fixed to the internal cover plate, the channel of the auxiliary anchor has a limiting structure for limiting the backward movement of the working clip of the working anchor, the elastic return member is arranged in the rear chamber and its two ends respectively touch the rear end face of the sleeve and the internal cover plate.

[0007] The present invention is installed between the jack and the working anchor when in use. When working, the jack supplies oil, and the working clip of the working anchor moves backward following the steel strand. After moving backward for a short distance, it is limited by the limiting structure of the auxiliary anchor, driving the auxiliary anchor to move backward together until the friction force of the steel strand on the working clip and the elastic force of the elastic recovery member reach a balance and no longer move backward. During voltage stabilization, due to the loss of tensioning force, the auxiliary anchor is pushed back into the mounting hole of the working anchor by the recovery force of the elastic recovery member. Therefore, since the working clip is partially retracted into the hole of the working anchor in advance, when the jack returns oil, anchoring can be performed in advance, which can effectively reduce the retraction amount of the steel strand, thereby achieving the purpose of reducing the prestressed retraction loss.

[0008] As a preferred embodiment of the present invention, the channel of the auxiliary anchor is mainly composed of a conical channel at the front and a cylindrical channel at the rear, and the conical channel gradually shrinks from front to back to form the limiting structure, and the conical channel is used to limit the conical working clip that gradually expands from front to back during the tensioning process of the steel strand so that the working clip drives the auxiliary anchor and the internal cover plate to move backward together.

[0009] As a recommended implementation mode of the present invention, the central axes of the channels of each component are located on the same straight line.

[0010] Preferably, the elastic return member is a compression spring.

[0011] As a preferred embodiment of the present invention, the hole of the sleeve extends into the rear chamber to form a cylindrical fixing column, and the hole of the internal cover plate extends into the rear chamber to form a cylindrical positioning column, and the two ends of the spring are respectively mounted on the fixing column and the positioning column.

[0012] The front end opening of the sleeve of the present invention has an annular sinking step, and the step surface of the sinking step is used for limiting the working anchor.

[0013] As a preferred embodiment of the present invention, the holes of each component are multiple and evenly distributed along the circumference of each disk surface.

[0014] There is an annular gap between the auxiliary anchor and the inner wall of the sleeve of the present invention, and the annular gap is 1-2 mm.

[0015] As a preferred embodiment of the present invention, the auxiliary anchor and the inner cover plate are respectively provided with fixing holes in the middle, and the fixing members pass through the fixing holes and are fastened to fix the two together.

[0016] The auxiliary anchor and the working anchor of the present invention are both cylindrical, and the diameter of the auxiliary anchor is 1.5 to 2.5 cm smaller than the diameter of the working anchor.

[0017] Compared with the prior art, the present invention has the following significant effects:

[0018] ⑴ When the present invention is working, when the jack supplies oil, the working clip of the working anchor moves backward following the steel strand. After moving backward for a short distance, it is restricted by the limiting structure of the auxiliary anchor, driving the auxiliary anchor to move backward together until the friction force of the steel strand on the working clip and the elastic force of the elastic recovery member reach a balance and no longer move backward. During voltage stabilization, due to the loss of tensioning force, the auxiliary anchor is pushed back into the mounting hole of the working anchor by the recovery force of the elastic recovery member. Therefore, since the working clip is partially retreated into the working anchor hole in advance, when the jack returns oil, anchoring can be performed in advance, which can effectively reduce the retraction of the steel strand, thereby achieving the purpose of reducing the prestressed retraction loss.

[0019] (2) The invention has the advantages of simple structure, low cost, reliability, stability and strong practicability, and is suitable for wide promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0021] Figure 1 It is a partially cutaway stereoscopic view of the present invention and the working anchor assembly;

[0022] Figure 2 yes Figure 1 A-direction view;

[0023] Figure 3 yes Figure 1 B-direction view;

[0024] Figure 4 is a side view of the present invention assembled with a working anchor;

[0025] Figure 5 is along Figure 4 Cross-section view along the CC line. DETAILED DESCRIPTION

[0026] like Figures 1 to 5 As shown, a limit plate for reducing prestressed shrinkage loss of the present invention includes a sleeve 1, an internal cover plate 2, a compression spring 3, an auxiliary anchor 4 and a bolt 5. The sleeve 1, the internal cover plate 2 and the auxiliary anchor 4 are all cylinders. The rear end face 11 of the sleeve 1, the internal cover plate 2 and the auxiliary anchor 4 are respectively provided with holes for the steel strands to pass through. The holes of each component are connected to each other front and back, and the central axes of the holes of each component are located on the same straight line. The holes are respectively the hole 12 of the sleeve 1, the hole 21 of the internal cover plate 2 and the hole 41 of the auxiliary anchor 4. There are 6 holes in each component and they are evenly distributed along the circumference of each disk surface. The internal cover plate 2 can be slidably installed in the sleeve 1 and divides the internal space of the sleeve 1 into a front chamber and a rear chamber. The auxiliary anchor 4 is installed in the front chamber through the front end opening of the sleeve 1 and is fixed to the internal cover plate 2. Specifically, the auxiliary anchor 4 and the middle of the internal cover plate 2 are respectively provided with fixing holes, and the bolt 5 is passed through the fixing hole as a fixing part and is fastened by the nut 14 to fix the two. The center hole 15 on the rear end face 11 of the sleeve 1 is used to discharge impurities such as oil. There is an annular gap between the auxiliary anchor 4 and the inner wall of the sleeve 1, and the annular gap is 1 to 2 mm. The channel 41 of the auxiliary anchor 4 has a limiting structure for limiting the backward movement of the working clamp 7 of the working anchor 6. In this embodiment, the channel 41 of the auxiliary anchor 4 is mainly composed of a conical channel at the front and a cylindrical channel at the rear. The conical channel gradually shrinks from front to back to form a limiting structure. The conical channel is used to limit the conical working clip 7 that gradually expands from front to back during the tensioning process of the steel strand, so that the working clip 7 drives the auxiliary anchor 4 and the internal cover plate 2 to move backward together.

[0027] The compression spring 3 is arranged in the rear chamber of the sleeve 1 and its two ends respectively contact the rear end face 11 of the sleeve 1 and the inner cover plate 2. Specifically, the hole 12 of the sleeve 1 extends into the rear chamber to form a cylindrical fixing column 13, and the hole 21 of the inner cover plate 2 extends into the rear chamber to form a cylindrical positioning column 16, and the two ends of the compression spring 3 are respectively sleeved on the fixing column 13 and the positioning column 16.

[0028] The working anchor 6 is an existing device, which is mainly composed of a cylindrical main body 8 and a working clip 7. The working clip 7 is a frustum body, and the main body 8 has a tapered channel 81 adapted to the working clip 7. The front end opening of the sleeve 1 has an annular sinking step 9, and the step surface of the sinking step 9 is used to limit the main body 8 of the working anchor. The diameter of the auxiliary anchor 4 is 1.5 to 2.5 cm smaller than the diameter of the working anchor 8.

[0029] The working process of the present invention is as follows: when in use, the limit plate of the present invention is installed between the jack and the working anchor, that is, the limit plate is installed at the front end of the jack, and the auxiliary anchor is in contact with the working anchor and the working clip. When the jack supplies oil, the steel strand is tensioned, and the working clip moves backward following the steel strand. After moving backward a short distance, the working clip drives the auxiliary anchor and the internal cover plate to move backward together until the friction force of the steel strand on the working clip and the action of the compression spring reach a balance and no longer move backward. During prestressed tensioning and voltage stabilization, due to the loss of tensioning force, the auxiliary anchor is pushed back into the conical channel of the working anchor by the action of the spring. Therefore, since the working clip is partially retracted into the working anchor hole in advance, anchoring can be performed in advance when the jack returns oil. The retraction amount of the steel strand can be effectively reduced, thereby achieving the purpose of reducing the prestressed retraction loss.

[0030] The embodiments of the present invention are not limited to this. According to the above content of the present invention, according to the common technical knowledge and customary means in the field, the limiting structure, elastic return member and its fixing form, the fixing method of the internal cover plate and the auxiliary anchor of the present invention all have other embodiments. Therefore, the present invention can also make other various forms of modification, replacement or change, all of which fall within the scope of protection of the present invention.

Claims

1. A limit plate for reducing prestress shrinkage loss, characterized in that: It includes a sleeve, an internal cover plate, an elastic return member and an auxiliary anchor. The rear end face of the sleeve, the internal cover plate and the auxiliary anchor are respectively provided with holes for the steel strand to pass through, and the holes of each component are correspondingly connected front to back. The internal cover plate can be slidably installed in the sleeve and divides the internal space of the sleeve into a front chamber and a rear chamber. The auxiliary anchor is a block-shaped body, which is installed in the front chamber through the front end opening of the sleeve and is fixed to the internal cover plate. The hole of the auxiliary anchor is provided with a limiting structure for limiting the backward movement of the working clip of the working anchor. The elastic return member is arranged in the rear chamber and its two ends respectively touch the rear end face of the sleeve and the internal cover plate.

2. The limiting plate for reducing prestress shrinkage loss according to claim 1 is characterized in that: The channel of the auxiliary anchor is mainly composed of a conical channel at the front and a cylindrical channel at the rear. The conical channel gradually shrinks from front to back to form the limiting structure. The conical channel is used to limit the conical working clip that gradually expands from front to back during the tensioning process of the steel strand so that the working clip drives the auxiliary anchor and the internal cover plate to move backward together.

3. The limiting plate for reducing prestress shrinkage loss according to claim 1 or 2, characterized in that: The central axes of the holes of each component are located on the same straight line.

4. The limiting plate for reducing prestress shrinkage loss according to claim 3 is characterized in that: The elastic return member is a compression spring.

5. The limiting plate for reducing prestress shrinkage loss according to claim 4 is characterized in that: The hole of the sleeve extends into the rear chamber to form a cylindrical fixing column, and the hole of the inner cover plate extends into the rear chamber to form a cylindrical positioning column, and the two ends of the spring are respectively sleeved on the fixing column and the positioning column.

6. The limiting plate for reducing prestress shrinkage loss according to claim 5 is characterized in that: The holes of each component are multiple and evenly distributed along the circumference of each disk.

7. The limiting plate for reducing prestress shrinkage loss according to claim 6 is characterized in that: The front end opening of the sleeve is provided with an annular sinking step, and the step surface of the sinking step is used for limiting the working anchor.

8. The limiting plate for reducing prestress shrinkage loss according to claim 7, characterized in that: There is an annular gap between the auxiliary anchor and the inner wall of the sleeve, and the annular gap is 1 to 2 mm.

9. The limiting plate for reducing prestress shrinkage loss according to claim 8, characterized in that: The auxiliary anchor and the working anchor are both cylindrical, and the diameter of the auxiliary anchor is 1.5 to 2.5 cm smaller than the diameter of the working anchor.

10. The limiting plate for reducing prestress shrinkage loss according to claim 9, characterized in that: The auxiliary anchor and the middle part of the inner cover plate are respectively provided with fixing holes, and the fixing parts pass through the fixing holes and are fastened to fix the two.

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