Method for erecting narrow-width steel box girder

Abstract

The present application relates to the field of rail transit equipment, and discloses a narrow steel box girder erecting method, comprising the following steps: step one, installing pushing equipment on each temporary support pier; installing auxiliary supports on the side of the bridge pier, and connecting parts are arranged between the auxiliary supports and the bridge pier, sliding rails are arranged on the connecting parts, and sliding blocks are slidably connected to the sliding rails; step two, installing rotating supports on the side of the bridge pier far from the pushing starting point, and installing rotating parts on the lower surface of the rear end of the box girder; step three, moving the front end of the box girder to the position of the auxiliary support of the second bridge pier and connecting the front end of the box girder with the sliding block, moving the rear end of the box girder to the position of the first bridge pier and placing the rotating part in the rotating groove; and step four, sliding the front end of the box girder together with the sliding block on the sliding rail to the second bridge pier, and rotating the box girder with the rotating part as the center; the method has low construction difficulty, wide application range and is suitable for small-radius and large-span rail transit construction.

Description

A method for erecting narrow steel box girders Technical Field

[0001] This invention relates to the field of rail transit equipment, and more specifically to a method for erecting narrow steel box girders. Background Technology

[0002] In the southwestern region, which is mostly mountainous, the construction of rail transit is limited by the terrain. Some locations have small curve radii and large spans, and the rail transit bears a large load. Box girders are usually used. Narrow steel box girders have significant technical and economic advantages in the economic span range of 20-80m. Therefore, the construction technology of narrow steel box girders has been gradually and widely applied to the construction of rail transit in mountainous areas.

[0003] Girder erecting machines are suitable for straight road sections. However, if specially customized equipment is made for small curve radii in special projects, the cost is high and it cannot be reused. If jacking equipment is used, multi-point continuous step-by-step jacking is required, which requires jacking while connecting the ends of adjacent box girders. This is not suitable for multi-span variable height beams and bridges with large vertical curvature. The repeated stress during the jacking process places high demands on construction equipment and technology. As the bridge length increases, the construction progress is slow. Especially for narrow steel box girders, although it is very economical, the narrow width makes it difficult to meet the section requirements for cantilever bending moment during the jacking process.

[0004] Therefore, a method for erecting narrow steel box girders is needed, which is easy to construct, has a wide range of applications, and is suitable for rail transit construction with small radius and large span. Summary of the Invention

[0005] The present invention aims to provide a method for erecting narrow steel box girders, which has low construction difficulty, wide applicability, and is suitable for rail transit construction with small radius and large span.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for erecting narrow steel box girders, comprising the following steps:

[0007] Step 1: Install temporary supports between the bridge piers, and install jacking equipment on each temporary support; install auxiliary supports on the side of the bridge piers, with a connecting part between the auxiliary supports and the bridge piers, and a slide rail on the connecting part, with a slider slidably connected on the slide rail. Take one end of the bridge as the jacking starting point, and the two ends of the slide rail are respectively on the auxiliary support and the side of the bridge pier closest to the jacking starting point.

[0008] Step 2: Install a rotating bearing on the side of the pier away from the jacking starting point. The rotating bearing is equipped with a hemispherical rotating groove. Hoist the box girder onto a temporary support near the jacking starting point. The jacking equipment jacks the box girder in the chord direction of the box girder's central axis. Install a hemispherical rotating part that matches the rotating groove on the lower surface of the rear end of the box girder.

[0009] Step 3: Move the front end of the box girder to the auxiliary support position of the second pier and connect it with the slider; move the rear end of the box girder to the position of the first pier and place the rotating part in the rotating groove.

[0010] Step 4: Slide the front end of the box girder and the slider together on the slide rail to the second pier. The box girder will rotate around the rotating part as the center. Disconnect the slider and the box girder.

[0011] Step 5: Adjust the direction of the jacking equipment and repeat steps 2-4 until the box girder reaches the jacking endpoint. The jacking endpoint of the first box girder is the end of the bridge, and the jacking endpoint of subsequent box girders is the end of the previous box girder.

[0012] The beneficial effects of this plan are:

[0013] 1. In the existing technology, a jacking device is used to lift the box girder, and then the horizontal moving speed of the jacking device on the inner and outer sides of the curve is adjusted to achieve the jacking of the box girder in the curved direction. However, this method has high requirements for the control of the jacking device, and requires the simultaneous coordination of the jacking speed of multiple jacking devices. The stress change of the box girder is large, which places high demands on the construction.

[0014] In this scheme, the box girder is first pushed along a straight line, and then rotated around the rotating part as the center to complete the passage of the box girder through the arch. When pushing in a straight line, the stress change of the box girder is smaller and the construction difficulty is lower; while rotating the box girder can adapt to the construction conditions of small radius curves.

[0015] 2. This scheme uses narrow box girders for jacking, making the box body lighter and more economical. For rail transit with multiple tracks, narrow box girders corresponding to the number of tracks are set up to give the track locations a stronger load-bearing capacity.

[0016] 3. This scheme involves jacking each box girder individually, making it suitable for bridges with multi-span variable height beams and large vertical curvature. Its applicability is wider than that of the walking-type jacking method.

[0017] Furthermore, the jacking equipment on the temporary supports is divided into two groups. The first group is located below the box girder in step three, and the second group is located below the box girder in step four. This arrangement ensures that the jacking equipment can be used to jack the box girder both before and after rotation.

[0018] Furthermore, in step three, the connection between the front end of the box girder and the slider is as follows: a limiting block is provided on the lower surface of the front end of the box girder, and a limiting groove is provided on the upper surface of the slider to cooperate with the limiting block. The limiting block and the limiting groove are inserted into each other. With this configuration, when the limiting block is aligned with the limiting groove, the jacking device drives the box girder to descend, the limiting block inserts into the limiting groove, and the slider slides on the slide rail, thereby driving the limiting block and the front end of the box girder to rotate together. In step five, when the box girder passes through the hole for the second time, the jacking device lifts the box girder again, and the limiting block directly separates from the limiting groove, which is convenient and quick, and this process does not require manual assistance.

[0019] Furthermore, the rotating support includes a threaded rod and two symmetrically arranged detachable supports. The rotating groove is formed by assembling the two detachable supports. Both detachable supports are provided with threaded holes, which are arranged in opposite directions. The threaded rod is threadedly connected to the two threaded holes. With this configuration, the assembly and disassembly of the two detachable supports can be achieved by rotating the threaded rod.

[0020] Furthermore, a rotating bar is horizontally provided at the bottom of the rotating part, a receiving groove is provided at the bottom of the rotating groove, a guide part is provided on the side of the receiving groove, a guide groove is provided on the guide part, one end of the guide groove is connected to the receiving groove, and the other end of the guide groove is set at the end point of the design axis of the box girder.

[0021] Before the box girder reaches the end of the jacking, in step four, the rotating bar rotates in the receiving groove until the rotating bar and the guide groove are aligned. Then, the rotating support is removed in sequence and the rotating bar is slid into the guide groove. Under the push of the jacking equipment, the rotating bar slides in the guide groove until the end of the box girder near the starting point of the jacking reaches the end position of the designed axis of the box girder.

[0022] When the box girder reaches the final launching point, the difference between step four and the step before the box girder reaches the final launching point is that the rotating supports are removed only after all the box girders have reached the final launching point. This setup has a corrective effect. Specifically,

[0023] 1. Correction. By sliding the rotating bar within the guide groove, the axis of the box girder is aligned with the design axis of the box girder, thereby achieving correction.

[0024] 2. When the box girder rotates, the rotating part rotates in the rotating groove, and the rotating bar rotates in the receiving groove, thereby preventing the rotating bar from interfering with the rotation of the rotating part and avoiding the transfer of the load of the box girder to the rotating bar.

[0025] Furthermore, the upper surface of the rotating support is inclined towards the end point of the box girder's design axis. With this configuration, in step four, as the two detachable supports are gradually disassembled, the supporting force of the rotating support on the box girder gradually decreases, and the weight of the box girder generates a component force along the inclined direction of the upper surface of the rotating support. This component force reduces the resistance as the rotating bar slides within the guide groove.

[0026] Furthermore, in step two, the installation steps of the rotating support are as follows: connect the two detachable supports with threaded rods and clamp the guide part; the axis of symmetry of the two detachable supports and the axis of the guide groove coincide;

[0027] In step four, the steps for removing the rotating support are as follows: Use a jacking device to push the box girder upwards, loosening the fit between the rotating groove and the rotating part; while rotating the threaded rod, gradually move the two detachable supports away from each other, and simultaneously use the jacking device to move the box girder towards the jacking starting point, causing the rotating bar to gradually enter the guide groove, and then move the box girder along the guide groove, ultimately bringing the end of the box girder closest to the jacking starting point to the design axis endpoint. With this setup, during the removal of the rotating support, as the two detachable supports move away from each other, the box girder slides down the side wall of the rotating groove. Under the jacking action of the jacking device, the rotating bar enters the guide groove, thereby transferring the load of the box girder from the rotating support to the guide part.

[0028] Furthermore, the rotating support is equipped with a directional ring, which is concentrically positioned at the edge of the rotating groove. The directional ring is marked with two directions: 0° and α. The 0° direction is the jacking direction in step two; the α direction is the direction after the box girder rotates in step four. This arrangement facilitates observation of the rotation angle, ensures the accuracy of the rotation angle, and reduces construction errors.

[0029] Furthermore, α = (L * 360°) / (2πR)

[0030] L - Length of the centerline of the box girder;

[0031] R - The curve radius of the centerline of the box girder.

[0032] This setup allows for the calculation of the theoretical rotation angle using the length of the box girder's centerline and the radius of the curve, enabling timely correction during construction and reducing the risk of overturning during the box girder's jacking process.

[0033] Furthermore, the directional ring has vertical protrusions in the 0° and α directions, and the rotating part has horizontal protrusions on its side. When the box girder rotates to the 0° and α directions, the vertical protrusions can restrict the horizontal protrusions on the rotating part from continuing to rotate. This design limits the rotation angle of the box girder, ensures construction accuracy, and reduces the risk of overturning during the box girder jacking process. Attached Figure Description

[0034] Figure 1 is a schematic diagram of the box girder through-hole in the embodiment;

[0035] Figure 2 is a schematic diagram of the box girder in the embodiment;

[0036] Figure 3 is an overall schematic diagram of the bridge piers, temporary piers and box girders in the embodiment;

[0037] Figure 4 is a schematic diagram of the route in the embodiment;

[0038] Figure 5 is a schematic diagram of the bridge cross-section in the embodiment;

[0039] Figure 6 is a top view of the bridge pier and auxiliary support in the embodiment;

[0040] Figure 7 is a cross-sectional view of the guide rail in the embodiment;

[0041] Figure 8 is the left view of Figure 7;

[0042] Figure 9 is a three-dimensional isometric view of the rotating support in the embodiment;

[0043] Figure 10 is a three-dimensional isometric view of the detachable support and guide in the embodiment;

[0044] Figure 11 is a left view of the rotating support of the embodiment;

[0045] Figure 12 is a sectional view along line AA of Figure 11;

[0046] Figure 13 is a cross-sectional view of Figure 12 after the addition of the rotating part. Detailed Implementation

[0047] The following detailed description illustrates the specific implementation method:

[0048] The reference numerals in the accompanying drawings include: box girder 1, box girder 110 in step two, box girder 120 in step three, box girder 130 in step four, box girder centerline 140, chord of box girder centerline 150, bridge centerline 160, bridge deck 210, pier 220, temporary support 310, auxiliary support 320, jacking device 330, connecting part 410, slide rail 420, slider 430, limiting block 440, rotating support 500, rotating groove 510, receiving groove 520, positioning ring 530, vertical protrusion 531, guide part 540, guide groove 541, detachable support 550, threaded rod 551, threaded hole 552, rotating part 560, horizontal protrusion 561, and rotating bar 562.

[0049] Example

[0050] The basic implementation example is shown in Figure 1-13. The terms used in this example are explained as follows:

[0051] Box girder 1: As shown in Figure 5, the narrow steel box girder 1, the bridge from top to bottom includes bridge deck 210, box girder 1 and pier 220. There are two box girders 1 in one cross section, and the box girders 1 are connected by transverse connectors (not shown in the figure).

[0052] Jacking device 330: The walking jacking device, model SX-100T, has three-way jacking functions along the x, y, and z axes;

[0053] Box girder centerline 140: As shown in Figure 2, the box girder centerline 140;

[0054] Chord 150 of the box girder's centerline: As shown in Figure 2, chord 150 of the box girder's centerline;

[0055] Design axis of box girder 1: The corresponding position of the center axis 140 of the box girder on the construction site on the design drawings;

[0056] A method for erecting narrow steel box girders, with the bridge's plan alignment as shown in Figure 4, includes the following steps:

[0057] Step 1: As shown in Figure 3, two temporary supports 310 are erected between adjacent piers 220. A jacking device 330 is installed on each temporary support 310. The jacking devices 330 on the temporary supports 310 are divided into two groups, with the first and second groups facing different directions. The jacking starts at the left end of the bridge and ends at the right end, as shown in Figure 6. An auxiliary support 320 is installed on the side of the pier 220. The auxiliary support 320 is a steel pipe support erected based on the pre-embedded cantilevered steel sections (not shown in the figure) on the side of the pier 220. A connecting part 410 is provided between the auxiliary support 320 and the pier 220. The connecting part 410 is a steel plate, which is welded to both the auxiliary support 320 and the pier 220. Several embedded parts are pre-embedded on the pier 220. In this embodiment, the connection with the pier 220 refers to the connection with the embedded parts on the pier 220. An arc-shaped slide rail 420 is welded to the connecting part 410. The two ends of the slide rail 420 are respectively on the auxiliary support 320 and the pier 220 near the starting point of the jacking, as shown in Figure 7. A slider 430 is provided on the slide rail 420. A sliding groove is opened on the lower side of the slider 430. The sliding groove and the slide rail 430 are connected. 20. The sliding joints are consistent in direction and slide together, as shown in Figure 8. The upper side of the slider 430 has a limit groove, and the direction of the limit groove is perpendicular to the sliding groove, as shown in Figures 1 and 2. The upper part of the box girder 1 is the pushing direction. The upper end of the box girder 1 is defined as the front end of the box girder 1, and the opposite end is the rear end of the box girder 1. As shown in Figure 8, the limit block 440 is slidably connected in the limit groove. The limit block 440 is bolted to the lower surface of the front end of the box girder 1. The sliding direction of the slider 430 is also provided with a tension unit (not shown in the figure). The tension unit includes a winch and a steel cable. One end of the steel cable is coiled on the winch, and the other end is hooked to the slider 430.

[0058] Step 2: Install a rotating bearing 500 on the side of pier 220 away from the starting point of the jacking operation, as shown in Figure 11. The right side is the side closest to the design axis endpoint of box girder 1. The upper surface of the rotating bearing 500 is inclined to the right, as shown in Figure 9. A hemispherical rotating groove 510 is opened on the upper surface of the rotating bearing 500. A directional ring is welded to the upper surface of the rotating bearing 500. The directional ring is concentrically set at the edge of the groove opening of the rotating groove 510. The directional ring is marked with two directions, 0° and α, that is, the included angle between the two directions is α. The first set of jacking devices 330 on the temporary pier 310 jacks in the 0° direction, and the second set of jacking devices 330 jacks in the α direction.

[0059] α=(L*360°) / (2пR)

[0060] L - Length of the box girder centerline 140;

[0061] R-Channel radius of the box girder centerline 140.

[0062] The marking method for these two directions is to weld cylindrical vertical protrusions 531 on the directional ring in the corresponding directions. As shown in Figure 12, the bottom of the rotating groove 510 has a vertical cylindrical receiving groove 520. The diameter of the receiving groove 520 is 1 / 3 of the diameter of the rotating groove 510. The side of the receiving groove 520 is provided with a guide part 540. The guide part 540 has a guide groove 541. One end of the guide groove 541 is connected to the receiving groove 520. The other end of the guide groove 541 extends outside the rotating support 500 and extends to the end position of the design axis of the box girder 1. The axial direction, 0° direction and chord 150 direction of the central axis of the box girder are the same.

[0063] As shown in Figures 9 and 10, the rotating support 500 includes a threaded rod 551 and two symmetrically arranged detachable supports 550. The rotating groove 510 is formed by assembling the two detachable supports 550. Both detachable supports 550 are provided with threaded holes 552, which are arranged in opposite directions. The threaded rod 551 and the two threaded holes 552 are threadedly connected. The assembly and disassembly of the two detachable supports 550 can be achieved by rotating the threaded rod 551. The directional ring is formed by two symmetrically arranged detachable half-rings, which are respectively welded to the upper surface of the detachable support 550.

[0064] The installation steps of the rotating support 500 are as follows: bolt the guide part 540 and the pier 220 together; connect the two detachable supports 550 through the threaded rod 551 and clamp the guide part 540; the axis of symmetry of the two detachable supports 550 and the axis of the guide groove 541 coincide.

[0065] The box girder 1 is hoisted onto a temporary support 310 near the starting point of the jacking process. The jacking device 330 lifts the box girder 1 upwards. A hemispherical rotating part 560 is bolted to the lower surface of the rear end of the box girder 1, as shown in Figure 13. A horizontal protrusion 561 is welded to the side of the rotating part 560. The rotating part 560 and the rotating groove 510 are rotatably engaged. A rotating strip 562 is integrally formed on the lower side of the rotating part 560. The rotating strip 562 rotates in the receiving groove 520. The shape of the rotating strip 562 and the guide groove 541 are matched. The rotating strip 562 can slide and connect with the guide groove 541. The jacking device 330 continues to jack the box girder 1 along the 0° direction of the positioning ring 530. The box girder 110 in step two is shown in Figure 1.

[0066] Step 3: In Figure 3, the piers 220 from left to right are the first pier 220 and the second pier 220, respectively. The front end of the box girder 1 is moved to the position of the auxiliary support 320 of the second pier 220 by the jacking device 330. During the process of the jacking device 330 driving the box girder 1 to fall, the limiting block 440 is inserted into the limiting groove of the slider 430, thereby realizing the connection between the box girder 1 and the slider 430. The rear end of the box girder 1 is moved to the position of the first pier 220 by the jacking device 330, and the rotating part 560 is aligned and placed in the rotating groove 510. When the horizontal protrusion 561 rotates with the rotating part 560 to the 0° and α directions, the vertical protrusion 531 on the positioning ring 530 at the opening of the rotating groove 510 can restrict the horizontal protrusion 561 on the rotating part 560 from continuing to rotate. The box girder 120 in Step 3 is shown in Figure 1.

[0067] Step 4: Drive the winch to move the slider 430 through the cable, and slide the front end of the box girder 1 and the slider 430 together on the slide rail 420 to the second pier 220. The box girder 1 rotates around the rotating part 560 as the center. When the box girder 1 rotates to the α direction of the positioning ring 530, it stops rotating. At this time, the box girder 130 in step 4 is shown in Figure 1. Remove the rotating support 500.

[0068] The steps for removing the rotating support 500 are as follows: Use the jacking device 330 to push the box girder 1 upward, so that the fit between the rotating groove 510 and the rotating part 560 is loosened. At the same time, the limiting block 440 exits the limiting groove of the slider 430 to remove the connection between the slider 430 and the box girder 1. While rotating the threaded rod 551, the two detachable supports 550 are gradually moved away from each other. At the same time, the jacking device 330 is used to move the box girder 1 back to the jacking starting point, so that the rotating bar 562 gradually enters the guide groove 541, and then the box girder 1 moves along the guide groove 541. Finally, the end of the box girder 1 near the jacking starting point reaches the design axis endpoint position of the box girder 1.

[0069] Step 5: Adjust the jacking equipment to the 330° direction and repeat steps 2-4 until box girder 1 reaches the span before the jacking endpoint, as shown in Figure 3. The jacking endpoint of the first box girder 1 is the right end of the bridge, and the jacking endpoint of the subsequent box girder 1 is the left end of the previous jacked box girder 1. Each span of box girder 1 across the distance between two piers 220° is considered as passing through one span. When box girder 1 passes through the last span, repeat steps 2 and 3 first. After all box girder 1s have passed through the last span, all box girder 1s will then proceed to step 4 from left to right to ensure that the last box girder 1 has sufficient rotation space.

[0070] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for erecting narrow-span steel box girders, characterized in that, Includes the following steps: Step 1: Install temporary supports between the bridge piers, and install jacking equipment on each temporary support; install auxiliary supports on the sides of the bridge piers, with a connecting part between the auxiliary supports and the bridge piers. A slide rail is installed on the connecting part, and a slider is slidably connected to the slide rail. Taking one end of the bridge as the jacking starting point, the two ends of the slide rail are respectively on the auxiliary support and the side of the bridge pier closest to the jacking starting point; Step 2: Install rotating bearings on the side of the bridge pier away from the jacking starting point. The rotating bearings have hemispherical rotating grooves; hoist the box girder onto the temporary supports near the jacking starting point, and use the jacking equipment to jack the box girder in the chord direction along the central axis of the box girder; install a hemispherical rotating part that matches the rotating groove on the lower surface of the rear end of the box girder; Step 3:

3. Move the front end of the box girder to the auxiliary support position of the second pier and connect it with the slider. Move the rear end of the box girder to the position of the first pier and place the rotating part in the rotating groove.

4. Slide the front end of the box girder and the slider together on the slide rail to the second pier. The box girder rotates around the rotating part as the center. Disconnect the slider and the box girder.

5. Adjust the direction of the jacking equipment and repeat steps 2-4 until the box girder reaches the jacking endpoint. The jacking endpoint of the first box girder is the end of the bridge, and the jacking endpoint of subsequent box girders is the end of the previous box girder.

2. The method for erecting a narrow steel box girder according to claim 1, characterized in that: The jacking equipment on the temporary supports is divided into two groups. The first group is set below the box girder in step three, and the second group is set below the box girder in step four.

3. The method for erecting a narrow steel box girder according to claim 1, characterized in that: In step three, the connection between the front end of the box girder and the slider is as follows: a limiting block is provided on the lower surface of the front end of the box girder, and a limiting groove that cooperates with the limiting block is provided on the upper surface of the slider. The limiting block and the limiting groove are inserted together.

4. The method for erecting a narrow steel box girder according to claim 3, characterized in that: The rotating support includes a threaded rod and two symmetrically arranged detachable supports. The rotating groove is formed by assembling the two detachable supports. Both detachable supports are provided with threaded holes, which are arranged in opposite directions. The threaded rod and the two threaded holes are threadedly connected.

5. The method for erecting a narrow steel box girder according to claim 4, characterized in that: A rotating bar is horizontally positioned at the bottom of the rotating part, and a receiving groove is positioned at the bottom of the rotating groove. A guide part is positioned on the side of the receiving groove, and a guide groove is positioned on the guide part. One end of the guide groove is connected to the receiving groove, and the other end of the guide groove is positioned at the end point of the designed axis of the box girder. In step four, before the box girder reaches the end point of the jacking, the rotating bar rotates in the receiving groove until the rotating bar and the guide groove are aligned. Then, the rotating supports are removed one by one, and the rotating bar slides into the guide groove. Under the push of the jacking equipment, the rotating bar slides in the guide groove until the end of the box girder near the starting point of the jacking reaches the end point of the designed axis of the box girder. The difference between step four and step four before the box girder reaches the end point of the jacking is that the rotating supports are removed only after all the box girders have reached the end point of the jacking.

6. The method for erecting a narrow steel box girder according to claim 5, characterized in that: The upper surface of the rotating support is inclined toward the end of the design axis of the box girder.

7. The method for erecting a narrow steel box girder according to claim 6, characterized in that: In step two, the installation steps of the rotating support are as follows: connect the two detachable supports with threaded rods and clamp the guide part; the axis of symmetry of the two detachable supports and the axis of the guide groove coincide; in step four, the steps of removing the rotating support are as follows: use the jacking device to push the box girder upwards, so that the fit between the rotating groove and the rotating part is loosened; while rotating the threaded rod, so that the two detachable supports are gradually moved away, and use the jacking device to move the box girder towards the jacking starting point, so that the rotating bar gradually enters the guide groove, and then the box girder moves along the guide groove, and finally the end of the box girder near the jacking starting point reaches the end position of the designed axis of the box girder.

8. A method for erecting narrow steel box girders according to claim 7, characterized in that: The rotating support is equipped with a directional ring, which is set at the edge of the rotating groove with the center of the ring. The directional ring is marked with two directions, 0° and α. The 0° direction is the jacking direction in step two; the α direction is the direction after the box girder rotates in step four.

9. A method for erecting narrow steel box girders according to claim 8, characterized in that: α = (L*360°) / (2πR) L - length of the centerline of the box girder; R - radius of the curve of the centerline of the box girder.

10. A method for erecting narrow steel box girders according to claim 9, characterized in that: The directional ring has vertical protrusions in the 0° and α directions, and the rotating part has horizontal protrusions on its side. When the box girder rotates to the 0° and α directions, the vertical protrusions can restrict the horizontal protrusions on the rotating part from continuing to rotate.

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