A turning fixture and method for large-section steel box girders

Abstract

This invention provides a large-section steel box girder turning fixture. It employs a set of telescopic clamps to secure the steel box girder, with the clamps positioned at the designed intervals. After the clamps are fixed, a set of support columns are connected to them via hinged lugs. The steel box girder is rotated using lifting lugs on the opposite side of the hinged lugs. After a 90° rotation, the support columns are simultaneously rotated to the other side, and then the steel box girder is slowly lowered to complete a 180° rotation. This device improves safety during the turning process, accelerates construction, and avoids collisions and stress concentrations that could lead to cross-sectional deformation, thus ensuring construction quality. It can be widely applied in the production of large-section steel box girders and other similar projects. Compared to traditional methods of directly rotating the steel box girder itself, this method improves construction safety, speeds up construction, and ensures high-quality assembly and welding.

Description

Technical Field

[0001] This invention belongs to the technical field of bridge construction, and specifically relates to a turning tool and method for large-section steel box girder. Background Technology

[0002] Turning large-section steel box girders is an important technology in bridge construction, mainly used to solve the orientation problem of steel box girders during transportation and installation.

[0003] With the continuous development of bridge construction technology, long-span, heavy-load steel box girder bridges are becoming increasingly popular. During bridge construction, the steel box girder, as the main load-bearing component, directly impacts the quality, efficiency, and safety of the bridge construction due to its turning technology. Therefore, the research and application of turning technology for large-section steel box girders is particularly important.

[0004] Large-section steel box girders face challenges of collisions and stress concentration during the overturning process, both of which can impact their structural integrity and stability. Due to their size and weight, improper handling or equipment placement during overturning can easily lead to collisions with surrounding objects. These collisions can cause surface damage, deformation, or loosening of structural connections, affecting their load-bearing capacity and service life. Furthermore, the overturning process, combined with the girder's own weight and external forces, can easily cause stress concentration at structural connections or in localized areas. This stress concentration can lead to structural fatigue, deformation, or fracture, further compromising their load-bearing capacity and safety. Summary of the Invention

[0005] To address the problem of cross-sectional deformation caused by collisions and stress concentration during the overturning of large-section steel box girders, this invention provides a large-section steel box girder overturning fixture and method that can improve the welding and assembly quality and enhance the safety of the overturning process.

[0006] The solution adopted by this invention to solve its technical problem is as follows: a large-section steel box girder turning fixture, including an adjustable clamping device and a supporting column. The adjustable clamping device is a rectangular frame structure. The short side of the rectangular frame includes a first vertical rod and a second vertical rod, and the long side of the rectangular frame is formed by splicing a first horizontal rod and a second horizontal rod. The short side and the long side are connected and fixed by flange plates. Lifting lugs are provided at both ends of the first vertical rod and the second vertical rod. A set of symmetrical hinged lugs is provided in the middle of the first vertical rod, with the hinged lugs facing the outside of the rectangular frame. The rectangular frame is connected to the supporting column through the hinged lugs. The body of the first horizontal rod and the second horizontal rod is a rectangular tube, and flanges are provided on the sides of both ends of the rectangular tube. The plates, crossbar one and crossbar two are connected at opposite ends by flange plates, and bolt rods are fitted onto the mating flange plates; one end of crossbar one has a protruding wing plate on its side, and one end of crossbar two has a longitudinal connecting plate parallel to the wing plate. The wing plate and the longitudinal connecting plate have multiple rows of perforations, and the length of the long frame is changed by connecting different perforations on the wing plate and the longitudinal connecting plate; the support column includes a base and a column, the column is vertically fixed on the base, and the upper end of the column has a shaft hole. The support column is connected to the hinge ear plate on the vertical bar one of the adjustable clamp device through the shaft hole at the upper end of the column, so that the entire adjustable clamp device can rotate around the hinge shaft hole.

[0007] Furthermore, the base includes a set of parallel bottom support rods, with a horizontal connecting rod fixed between the bottom support rods. The horizontal connecting rod is located in the middle of the parallel bottom support rods, and a vertical rod is fixed at the center of the horizontal connecting rod.

[0008] Furthermore, symmetrical hooks are provided on both sides of the upright.

[0009] Furthermore, the hinge plate includes a set of parallel plates symmetrically installed on both sides of the first vertical rod. A hinge plate pad is also provided between the hinge plate and the first vertical rod. The hinge plate has a hinge hole. A channel steel with an opening facing outward is provided between the symmetrical hinge plates. The side plates of the channel steel are respectively connected to the two side plates of the hinge plate, and the inner side of the channel steel side plate is flush with the inner side of the plate. The bottom plate of the channel steel is located between the hinge hole and the first vertical rod. A rack is provided on the bottom plate of the channel steel. The inner side of the side plate of the channel steel... The surface is provided with a sliding groove, and the two ends of the sliding groove are connected to the hinge holes of the hinged ear plates on both sides; a horizontal shaft is provided in the shaft hole at the upper end of the upright, and a gear that meshes with the rack is provided on the horizontal shaft. A housing is provided outside the gear, and a set of symmetrical blocks is provided inside the housing. One end of the block is hinged to the housing, and a spring is provided between the block and the housing. The spring lifts the block so that the block is locked on the gear to restrict the rotation of the gear. A lever is provided between the blocks. By rotating the lever, the block is lifted and disengaged from the gear, thereby restricting the rotation direction of the gear on one side.

[0010] A method for turning over a large-section steel box girder includes the following steps:

[0011] Step 1: Prepare a set of two adjustable clamp devices, each adjustable clamp device is equipped with a set of support columns 2;

[0012] Step 2: The adjustable clamp device is fitted onto the steel box girder according to the design spacing, and the steel box girder is located in the rectangular frame of the adjustable clamp device;

[0013] Step 3: Install the support column on the hinged lug on the upper side of the vertical rod;

[0014] Step 4: Use a gantry crane to hook the lower right corner of the adjustable clamp device (i.e., the lifting lug furthest from the hinged lug plate of the installation support column), and lift the two adjustable clamp devices at the same time.

[0015] Step 5: The adjustable clamp device tilts and flips with its corner as the fulcrum, and the support column connected to the hinge ear plate moves toward the ground as the adjustable clamp device flips, until the base plate of the support column supports the ground.

[0016] Step 6: The gantry crane continues to lift, and the adjustable clamp device is rotated and suspended in the air with the support column as the fulcrum until vertical rod one and vertical rod two are parallel to the ground;

[0017] Step 7: Remove the connected support column and install the support column on another hinged lug plate;

[0018] Step 8: Lowering the gantry crane. Due to the change in the position of the supporting column that forms the fulcrum, the center of gravity of the adjustable clamp device changes in the opposite direction of the direction of movement of the supporting column. After lowering, the adjustable clamp device continues to rotate to the other side of the supporting column by gravity until the corner of the adjustable clamp device touches the ground.

[0019] Step 9: Lower the gantry crane. The adjustable clamp device continues to rotate with the corner in contact with the ground as the fulcrum until it is flat. The support column is lifted as it rotates. After the adjustable clamp device is rotated and flattened, the support column is removed. At this time, the steel box girder has completed a 180° rotation.

[0020] Step 10: Remove the adjustable clamp device that is fitted onto the steel box girder.

[0021] The beneficial effects of this invention are as follows: 1. The large-section steel box girder turning fixture provided by this invention improves the safety of turning large-section steel box girders, avoids the torsional deformation of the steel box girder caused by local stress concentration due to traditional processes, and improves the quality of turning. Breaking through the traditional steel box girder turning construction method, the steel box girder is placed in an adjustable clamp device, and the turning of the steel box girder is achieved by rotating the adjustable clamp device 180°, avoiding the steel box girder body from bearing the lifting stress and avoiding the torsional deformation caused by stress concentration.

[0022] 2. The large-section steel box girder turning tool of the present invention has a high safety factor, simple operation process, high work efficiency, and is economical and practical compared with the traditional construction method of welding and hoisting lifting lugs on steel box girders.

[0023] 3. The large-section steel box girder turning fixture provided by the present invention changes the position of the fulcrum during the turning process, thereby changing the center of gravity of the turning steel box girder. The turning of the entire steel box girder can be completed by using the self-weight of the steel box girder, which improves the turning efficiency, makes the turning process more reasonable and safe, and ensures the stability of the steel box girder turning. Attached Figure Description

[0024] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0025] Figure 2 This is a structural schematic diagram of vertical rod one.

[0026] Figure 3 This is a schematic diagram of the supporting column structure.

[0027] Figure 4 This is a side view of the supporting column structure.

[0028] Figure 5 This is a structural schematic diagram of crossbar one.

[0029] Figure 6 This is a structural schematic diagram of crossbar two.

[0030] Figure 7 This is a structural diagram of another implementation method for supporting columns.

[0031] Figure 8 This is a schematic diagram of the steel box girder turning process.

[0032] The following components are labeled in the diagram: Adjustable clamp device 1, support column 2, vertical rod 11, vertical rod 2 12, horizontal rod 13, horizontal rod 2 14, base 21, vertical rod 22, rod body 101, hinged lug 102, lifting lug 103, flange plate 3, stiffening plate 4, bottom support rod 211, horizontal connecting rod 212, hook 221, wing plate 131, longitudinal connecting plate 141, rack 501, slide groove 502, horizontal shaft 503, gear 504, stop block 505, spring 506, lever 507, housing 508. Detailed Implementation

[0033] Example 1: As Figure 1-6 As shown, the present invention provides a large-section steel box girder turning fixture, including a rectangular adjustable clamp device 1 for wrapping around the steel box girder, and a support column 2 for supporting the adjustable clamp device 1 to turn around the support point.

[0034] The rectangular adjustable clamp device 1 includes two parallel long side frames and two parallel short side frames. The short side frames include two different structures: vertical bar 11 and vertical bar 2 12. The long side frames have the same structure and are symmetrically arranged. They are spliced ​​together by horizontal bar 13 and horizontal bar 2 14.

[0035] Both ends of vertical rod 11 and vertical rod 2 are provided with lifting lugs 103. A set of hinged lug plates 102 are provided in the middle of vertical rod 11. The ends of the hinged lug plates 102 face the outside of the rectangular frame. The rectangular frame is connected to the support column 2 through the hinged lug plates 102.

[0036] The body of crossbar 13 and crossbar 24 is a rectangular tube. Flange plates 3 are provided on the sides of both ends of the rectangular tube. The opposite ends of crossbar 13 and crossbar 24 are connected by the flange plates, and bolt rods are inserted through the mating flange plates.

[0037] One end of the crossbar 13 has a protruding wing plate 131 on its side, and one end of the crossbar 14 has a longitudinal connecting plate 141 parallel to the wing plate. The wing plate 131 and the longitudinal connecting plate 141 have multiple rows of perforations. The length of the long frame is changed by connecting the wing plate 131 and the longitudinal connecting plate 141 with different perforations. Bolts are inserted between the flange plates for fixation.

[0038] To prevent the steel box girder from being damaged by impacts, the wing plate 131 and the longitudinal connecting plate 141 are both set on the outside of the rectangular frame, and the flange plate is set on both sides of the rectangular tube in a symmetrical structure, thereby ensuring that the inner side of the rectangular frame formed by the first vertical bar 11, the second vertical bar 12, the first horizontal bar 13 and the second horizontal bar 14 is flush and without protrusions.

[0039] The support column 2 includes a base 21 and a pole 22. The pole 22 is vertically fixed on the base. The upper end of the pole is provided with a shaft hole. The support column 2 is connected to the hinge ear plate 102 provided on the vertical rod of the adjustable clamp device 1 through the shaft hole at the upper end of the pole, so that the adjustable clamp device 1 can be rotated around the hinge shaft hole.

[0040] Specifically, the present invention uses a set of adjustable clamp devices to secure the steel box girder. The set of adjustable clamp devices are placed at the spacing required by the design. After the adjustable clamp devices are fixed, a set of support columns are connected to the adjustable clamp devices through hinged ear plates. The steel box girder is rotated through the lifting lugs on the opposite side of the hinged ear plates.

[0041] After rotating 90°, the supporting columns are simultaneously rotated to the other side, and then the steel box girder is slowly lowered, completing the 180° rotation. This device improves the safety of the turning process and speeds up construction. The adjustable clamp device allows for the rotation of the steel box girder, avoiding impacts and stress concentration that could lead to cross-sectional deformation, thus ensuring construction quality. It can be widely used in the production of large-section steel box girders. Compared to traditional methods of directly rotating the steel box girder itself, this method improves construction safety, accelerates construction speed, and ensures the quality of assembly and welding.

[0042] The adjustable clamp device of the present invention uses 350*200*10 rectangular tubes for the horizontal and vertical bars. The ends of the rectangular tubes are welded with end plates made of steel plates of different sizes. The flange plates, hinged lugs and lifting lugs are all made of steel plates of different sizes. The flange plates, wing plates 131 and longitudinal connecting plates 141 are all provided with stiffening plates for strengthening the fixation.

[0043] The adjustable clamp device is securely fixed to the steel box girder. Through hinged lugs and movable connections with the uprights, it forms a freely rotating shaft, enabling the steel box girder to be turned and rotated. The adjustable clamp device is hoisted using lifting lugs at the four corners. During the first rotation, the supporting columns contact the base surface, and the steel box girder rotates 90°. Then, the supporting columns are moved to the other side, completing the second rotation, and the steel box girder completes a 180° rotation, thus completing the turning. The supporting columns act as the pivot point for the turning and rotating process.

[0044] The components should be made of steel with a performance of not less than Q235B. The turning fixture is combined with the support column through an adjustable clamp device, which makes the steel box girder turning process safe and reliable, fast, and without disturbing the steel box girder. It overcomes the problems of high risk factor and large deformation of steel box girder in traditional process and ensures the turning quality of large section steel box girder.

[0045] This invention provides a large-section steel box girder flipping and welding device based on the cross-sectional dimensions and weight of the steel box girder. Since there are two types of steel box girder cross-sections, the transverse rectangular tube of the clamping device is composed of assemblable standard sections, all connected by high-strength bolts to meet the requirements of cross-sectional dimensions and rigidity. A gantry crane is used to insert the clamping device onto the steel box girder, and the flipping is completed through the clamping device.

[0046] The supporting column and the hinge lug of the clamping device serve as the rotation axis for the steel box girder to rotate. A pair of gantry cranes are used to rotate the girder through the lifting lugs of the clamping device. First, two sets of wire ropes are slowly lifted simultaneously. After the steel box girder has rotated 90° and stabilized, the crane hooks are slowly moved to complete the change of the hinge position. Using the gravity eccentric method, a pair of wire ropes are slowly lowered simultaneously, finally completing the rotation of the steel box girder.

[0047] The steel box girder is 2400mm high. Overhead welding of the top plate and some web plates makes it difficult to guarantee the quality of the weld. This invention rotates the steel box girder 180°, realizing the conversion of the weld from overhead welding to flat welding, which effectively improves the welding quality, reduces rework, and speeds up the assembly of the steel box girder.

[0048] like Figure 8 As shown, the method for turning over a large-section steel box girder based on the above-mentioned large-section steel box girder turning fixture includes the following steps:

[0049] Step 1: Prepare a set of two adjustable clamp devices 1, each adjustable clamp device 1 is equipped with a set of support columns 2;

[0050] Step 2: The adjustable clamp device 1 is fitted onto the steel box girder according to the design spacing, and the steel box girder is located in the rectangular frame of the adjustable clamp device 1;

[0051] Step 3: Install the support column 2 on the hinged lug plate on the upper side of the vertical rod 1;

[0052] Step 4: Use a gantry crane to hook the lower right corner of the adjustable clamp device 1 (i.e., the lifting lug furthest from the hinged lug plate of the installation support column), and lift both adjustable clamp devices 1 at the same time.

[0053] Step 5: The adjustable clamp device 1 tilts and flips with its corner as the fulcrum, and the support column connected to the hinge ear plate moves toward the ground as the adjustable clamp device 1 flips, until the base plate of the support column supports the ground.

[0054] Step 6: The gantry crane continues to lift, and the adjustable clamp device is rotated and suspended in the air with the support column as the fulcrum until vertical rod one and vertical rod two are parallel to the ground (that is, the clamp device can be adjusted to achieve a 90° rotation).

[0055] Step 7: Remove the connected support column and install the support column on another hinged ear plate (seamless replacement can be achieved here using two support columns. When the support column is flipped, it is subjected to great pressure and is not easy to remove. By using two support columns, when one support column is used as support, the other support column can be lifted to reduce the pressure on it, thus making it easier to remove and replace).

[0056] like Figure 8 As shown, during the hoisting and turning process, the left support column is used as the fulcrum. After the right steel box girder is hoisted, another support column is installed on the right hinge plate. The center of the steel box girder is controlled to deflect to the right support column by the hoisting device, which reduces the pressure on the left support column and facilitates the removal of the left support column.

[0057] Step 8: Lowering the gantry crane. Due to the change in the position of the supporting column that forms the fulcrum, the center of gravity of the adjustable clamp device changes in the opposite direction of the direction of movement of the supporting column. After lowering, the adjustable clamp device continues to rotate to the other side of the supporting column by gravity until the corner of the adjustable clamp device touches the ground.

[0058] Step 9: Lower the gantry crane. The adjustable clamp device continues to rotate with the corner in contact with the ground as the fulcrum until it is flat. The support column is lifted as it rotates. After the adjustable clamp device is rotated and flattened, the support column is removed. At this time, the steel box girder has completed a 180° rotation.

[0059] Step 10: Remove the adjustable clamp device that is fitted onto the steel box girder.

[0060] Example 2: As Figure 7 As shown, the present invention provides a connection structure for adjusting the position of the support point of the sliding support column 2. The hinged lug 102 provided on the vertical rod 1 includes a set of symmetrical parallel plates. The plates are fixedly welded to both sides of the vertical rod 1 by hinged lug pads. The plates extend to the outside of the rectangular frame. The outer end of the extended plate is provided with a shaft hole for hinge. The upper end of the vertically arranged upright 22 of the support column is fitted between the parallel plates.

[0061] A channel steel with an opening facing outward is provided between the symmetrical hinged lugs. The side plates of the channel steel are connected to the two side plates of the hinged lugs respectively, and the inner side of the side plate of the channel steel is flush with the inner side of the plate. The bottom plate of the channel steel is located between the hinge hole and the vertical rod. A rack 501 is provided on the bottom plate of the channel steel. A sliding groove 502 is provided on the inner side of the side plate of the channel steel, and the two ends of the sliding groove are connected to the hinge holes of the two hinged lugs.

[0062] A horizontal shaft 503 is installed in the shaft hole at the upper end of the upright 22. A gear 504 that meshes with a rack is installed on the horizontal shaft. A housing 508 is installed outside the gear. A set of symmetrical stops 505 is installed inside the housing. One end of the stop is hinged to the housing. A spring 506 is installed between the stop and the housing. The spring lifts the stop and makes the stop lock onto the gear. A lever 507 is installed between the stops. By rotating the lever, the stop is lifted and disengaged from the gear, thereby restricting the rotation direction of the gear on one side.

[0063] This embodiment uses a sliding groove, in which the hinge shaft is placed and moves. During hoisting and turning, the position of the hinge shaft can be changed by moving it along the groove. In this embodiment, the stable sliding transfer of the support column is achieved through the meshing of gears and racks. Stops are installed on both sides below the gear, and the distance between the stops and the gear is controlled by a lever, thus limiting the direction of gear rotation through different stops.

[0064] by Figure 7As shown, when the support column moves to the left, the left-side stop engages with the gear, preventing the gear from moving to the right. When the support column moves to the right, the right-side stop engages with the gear, preventing it from moving to the left. This device positions the support column at its end after movement, preventing it from sliding again during the overturning process.

[0065] The structure provided in this embodiment enables rapid switching of the support column position, reducing disassembly and assembly time and work, and improving the efficiency of steel box girder turning.

[0066] The specific embodiments described above are merely illustrative or explanatory of the principles of the present invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A turning fixture for large-section steel box girders, characterized in that, It includes an adjustable clamp device (1) and a support column (2). The adjustable clamp device (1) is a rectangular frame structure. The short side of the rectangular frame includes a vertical bar one (11) and a vertical bar two (12). The long side of the rectangular frame is spliced ​​by a horizontal bar one (13) and a horizontal bar two (14). The short side and the long side are connected and fixed by a flange plate. Lifting lugs are provided at both ends of vertical rod one (11) and vertical rod two (12). A set of symmetrical hinged lugs (102) is provided in the middle of vertical rod one (11). The hinged lugs (102) face the outside of the rectangular frame. The rectangular frame is connected to the supporting column (2) through the hinged lugs (102). The body of the crossbar 1 (13) and the crossbar 2 (14) is a rectangular tube. Flange plates (3) are provided on the sides of both ends of the rectangular tube. The opposite ends of the crossbar 1 (13) and the crossbar 2 (14) are connected by the flange plates. Bolt rods are inserted through the flange plates. One of the crossbars (13) has a protruding wing plate (131) on one side of one end, and the other of the crossbars (14) has a longitudinal connecting plate (141) parallel to the wing plate on one end. The wing plate (131) and the longitudinal connecting plate (141) have multiple rows of perforations. The length of the long frame can be changed by connecting different perforations through the wing plate (131) and the longitudinal connecting plate (141). The support column (2) includes a base (21) and a pole (22). The pole (22) is vertically fixed on the base. The upper end of the pole is provided with a shaft hole. The support column (2) is connected to the hinged ear plate (102) provided on the vertical rod of the adjustable clamp device (1) through the shaft hole at the upper end of the pole, so that the adjustable clamp device (1) can rotate around the hinged shaft hole as a whole. The hinge ear plate (102) includes a set of parallel plates, which are symmetrically installed on both sides of the vertical rod (11). A hinge ear plate pad is also provided between the hinge ear plate and the vertical rod (11), and a hinge hole is provided on the hinge ear plate. A channel steel with an opening facing outward is provided between the symmetrical hinged lugs. The side plates of the channel steel are connected to the two side plates of the hinged lugs respectively, and the inner side of the side plate of the channel steel is flush with the inner side of the plate. The bottom plate of the channel steel is located between the hinge hole and the first vertical rod. A rack (501) is provided on the bottom plate of the channel steel. A sliding groove (502) is provided on the inner side of the side plate of the channel steel, and the two ends of the sliding groove are connected to the hinge holes of the two hinged lugs. A horizontal shaft (503) is provided in the shaft hole at the upper end of the upright (22). A gear (504) that meshes with the rack is provided on the horizontal shaft. A housing (508) is provided on the outside of the gear. A set of symmetrical stops (505) is provided inside the housing. One end of the stop is hinged to the housing. A spring (506) is provided between the stop and the housing. The spring lifts the stop so that the stop is locked on the gear to restrict the rotation of the gear. A lever (507) is provided between the stops. By rotating the lever, the stop is lifted so that the stop is disengaged from the gear, thereby restricting the rotation direction of the gear on one side.

2. The large-section steel box girder turning fixture according to claim 1, characterized in that, The base (21) includes a set of parallel bottom support rods (211), and a horizontal connecting rod (212) is fixed between the bottom support rods (211). The horizontal connecting rod is located in the middle of the parallel bottom support rods, and a vertical rod (22) is fixed at the center of the horizontal connecting rod.

3. The large-section steel box girder turning fixture according to claim 2, characterized in that, Symmetrical hooks (221) are provided on both sides of the upright.

4. The large-section steel box girder turning fixture according to claim 1, characterized in that, The wing plate (131) and the longitudinal connecting plate (141) are both located on the outside of the rectangular frame, and the flange plate is symmetrically located on both sides of the rectangular tube.

5. The large-section steel box girder turning fixture according to claim 1, characterized in that, The horizontal and vertical bars of the adjustable clamp device are made of 350*200*10 rectangular tubes, and the ends of the rectangular tubes are welded with end plates.

6. A method for turning over a large-section steel box girder using the turning fixture as described in claim 1, characterized in that, Includes the following steps: Step 1: Prepare two adjustable clamp devices (1), each adjustable clamp device (1) is equipped with a set of support columns (2); Step 2: The adjustable clamp device (1) is fitted onto the steel box girder according to the design spacing, and the steel box girder is located in the rectangular frame of the adjustable clamp device (1); Step 3: Install the support column (2) on the hinged lug plate on the upper side of the vertical rod; Step 4: Use a gantry crane to hook the lifting lug on the lower right corner of the adjustable clamp device (1), and lift both adjustable clamp devices (1) at the same time; Step 5: The adjustable clamp device (1) tilts and flips with its corner as the fulcrum, and the support column connected to the hinge ear plate moves toward the ground with the rotation of the adjustable clamp device (1) until the bottom plate of the support column is supported on the ground. Step 6: The gantry crane continues to lift, and the adjustable clamp device is rotated and suspended in the air with the support column as the fulcrum until vertical rod one and vertical rod two are parallel to the ground; Step 7: Remove the connected support column and install the support column on another hinged lug plate; Step 8: Lowering the gantry crane. Due to the change in the position of the supporting column that forms the fulcrum, the center of gravity of the adjustable clamp device changes in the opposite direction of the direction of movement of the supporting column. After lowering, the adjustable clamp device continues to rotate to the other side of the supporting column by gravity until the corner of the adjustable clamp device touches the ground. Step 9: Lower the gantry crane. The adjustable clamp device continues to rotate with the corner in contact with the ground as the fulcrum until it is flat. The support column is lifted as it rotates. After the adjustable clamp device is rotated and flattened, the support column is removed. At this time, the steel box girder has completed a 180° rotation. Step 10: Remove the adjustable clamp device that is fitted onto the steel box girder.

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