Steel box girder hoisting process

Abstract

The present application relates to a steel box girder hoisting process, comprising: dividing a pier-top cross beam of a steel box girder structure into three segments in the direction of width of a road, namely, end segments at two ends and a middle segment between the two end segments; firstly, erecting temporary supports for the pier-top cross beam at the positions of bridge piers, such that the height of the temporary supports for the pier-top cross beam is higher than that of the bridge piers; then hoisting the two end segments to the upper ends of the temporary supports for the pier-top cross beam by means of a truck crane; then, using the truck crane to hoist lifting apparatuses to the upper surfaces of the end segments and mounting same; then, simultaneously lifting two ends of the middle segment by means of the lifting apparatuses on the two end segments, and after the middle segment reaches the position for butt joint with the end segments, connecting the middle segment and the end segments; and finally, removing the temporary supports for the pier-top cross beam so as to transfer the gravity of the pier-top cross beam to the bridge piers. The present application has the effect of facilitating the hoisting of a steel box girder.

Description

Steel box girder hoisting process TECHNICAL FIELD

[0001] The present application relates to the technical field of viaduct construction, in particular to a steel box girder hoisting process. BACKGROUND

[0002] The viaduct construction in municipal engineering is in a state of growth in urban development, and a part of the viaduct adopts a steel box girder structure. The steel box girder structure has the advantage of large span, and the self-weight of the steel box girder structure is lighter than that of the concrete structure, and can be processed in the factory and assembled at the construction site, so the construction speed is fast, and therefore the application of the steel box girder in the viaduct construction is gradually increasing.

[0003] At present, for the areas with good terrain conditions, the assembled steel box girder is usually erected quickly and safely by large hoisting equipment. However, for the underground subway track directly below the main road, and the high-voltage electricity and related factory area involved on both sides of the bridge, the construction environment is relatively narrow, so the large hoisting vehicle cannot directly enter the construction site during the entire installation process of the steel box girder, which brings great inconvenience to the construction. At the same time, the original method of assembling the steel box girder to the required length at the processing site and transporting it directly for erection is not applicable, on the one hand, the transportation is not convenient, and on the other hand, the large hoisting vehicle may not be able to reach, which brings great inconvenience to the construction. SUMMARY

[0004] The present application provides a steel box girder hoisting process for improving the hoisting of the steel box girder when the large hoisting vehicle cannot be used in the construction environment.

[0005] The steel box girder hoisting process provided by the present application adopts the following technical scheme.

[0006] A steel box girder hoisting process comprises: dividing a pier top beam of a steel box girder structure into three sections along the width direction of the road, end section segments at both ends and a middle section segment between the two end section segments, spacing two bridge piers for supporting the pier top beam, first erecting a temporary support of the pier top beam on the bridge pier, so that the height of the temporary support of the pier top beam is higher than that of the bridge pier, then hoisting the two end section segments to the upper end of the temporary support of the pier top beam by the truck crane, then hoisting the lifting equipment to the upper surface of the end section segment by the truck crane and installing it, then simultaneously lifting the two ends of the middle section segment by the lifting equipment on the two end section segments, connecting the middle section segment and the end section segment after the middle section segment reaches the position of the butt joint of the end section segment, and finally removing the temporary support of the pier top beam to transfer the gravity of the pier top beam to the bridge pier.

[0007] By adopting the technical scheme, the pier top beam structure is divided into three sections along the width direction, and the end section is hoisted by the truck crane first, and the weight of the end section is lower than the weight of the whole pier top beam, so that the force acting on the ground during hoisting can be reduced, and thus the measure can be used when a large hoisting vehicle cannot be used in the construction environment. The temporary support of the pier top beam is installed before the end section is hoisted, so as to stably support the end section, and the cross section of the pier is small, so that the end section cannot be stably supported, and the middle section is hoisted by the lifting equipment installed on the upper surface of the end section, wherein the temporary support of the pier top beam at the pier bears, so that the hoisting is facilitated when the large hoisting vehicle is not available in the construction environment.

[0008] Preferably, the temporary support of the pier top beam is located below the end section on the side close to the middle section, and the distance between the temporary support and the end section on the side close to the middle section is A1, and the distance between the support close to the middle section of the lifting equipment and the end section is A2, and A2 is equal to A1.

[0009] By adopting the technical scheme, the temporary support of the pier top beam is below the support of the lifting equipment on the end section, so that the force of the lifting equipment can be transmitted to the temporary support of the pier top beam through the end section, and thus the lifting equipment can be lifted more stably.

[0010] Preferably, before the lifting equipment lifts the two ends of the middle section, the middle section is transported by the SPMT module vehicle first, so that the middle section is moved to the position directly below the middle position of the two end sections, and the SPMT module vehicle is supported below the middle section.

[0011] Since the SPMT module vehicle has greater bearing capacity and smaller pressure on the ground, the transportation of the middle section can be completed under the condition that the bearing capacity of the ground is small by supporting the SPMT module vehicle below the middle section.

[0012] Preferably, the temporary support of the pier top beam comprises a plurality of vertically arranged support columns, a connecting table at the upper end of the support column, and a plurality of force relieving assemblies, the force relieving assembly is placed on the upper surface of the connecting table, the force relieving assembly comprises an outer cylinder and an inner column, the inner of the outer cylinder is used to fill sand, the lower part of the outer cylinder is provided with an outlet, the outlet is threadedly connected with a plug, and the lower end of the inner column is inserted into the outer cylinder.

[0013] The sand filled in the inner of the outer cylinder supports the inner column, so that the force relieving assembly can support the pier top beam with greater bearing capacity, and the sand can flow out of the outlet of the force relieving assembly, so as to facilitate the placement of the pier top beam on the pier.

[0014] Preferably, the connecting platform comprises distribution beams and connecting beams which are perpendicular to each other, the lower surface of the distribution beams is used to connect with the upper end of the supporting column, the distribution beams are arranged in parallel and are spaced apart, the two ends of the connecting beams are welded and fixed with the side of the distribution beams respectively, and the middle part of the connecting beams is disconnected and connected through the flange structure.

[0015] By using the above technical scheme, the distribution beams are used to connect with the upper end of the supporting column, and the middle part of the connecting beams is disconnected and connected through the flange structure, so that the connecting beams can be disassembled from the position of the flange structure, thereby facilitating the disassembly of the connecting platform.

[0016] Preferably, when the temporary support of the pier top beam is removed, the plugs at the outlets are opened first, the sand in the plurality of force relieving assemblies flows out at the same time, after the gravity of the pier top beam is transferred to the bridge pier, the sand in the force relieving assemblies continues to flow out, the upper end of the inner column is separated from the lower surface of the pier top beam, then the force relieving assemblies are taken off from the connecting platform, and the connecting beams are disconnected from the position of the flange structure and the connecting platform is taken off.

[0017] By using the above technical scheme, the plugs of the plurality of force relieving assemblies are opened at the same time, the sand flows out under the action of the gravity of the pier top beam, and the flow rate of the sand is limited, so that the pier top beam can be placed on the bridge pier with smaller impact force, and the sand can flow out too much to facilitate the taking out of the force relieving assemblies from the lower side of the pier top beam.

[0018] Preferably, the supporting column comprises a stabilizing section and an adjusting section, the stabilizing section comprises a plurality of vertical columns and stabilizing rods connecting the vertical columns, the plurality of vertical columns are fixedly connected through the stabilizing rods, a horizontal pull rod is detachably connected to one side of the stabilizing section, and the adjusting section is inserted into the upper end and the lower end of the vertical column.

[0019] By using the above technical scheme, the stabilizing section is integrally connected, so that the stabilizing section can be hoisted once, the adjusting section is inserted into the upper end and the lower end of the vertical column, so that the length of the adjusting section can be adjusted to adapt the height of the bridge pier to the supporting column.

[0020] Preferably, the removal of the temporary support of the pier top beam comprises the removal of the supporting column, when the supporting column is removed, the adjusting section at the upper end of the vertical column is pulled out first, then the horizontal pull rod is taken off, and then the stabilizing section is hoisted as a whole and is horizontally moved to separate from the bridge pier from the position of the horizontal pull rod.

[0021] By using the above technical scheme, when the supporting column is removed, the adjusting section at the upper end of the vertical column is taken off first, then the stabilizing section is hoisted as a whole, and then the stabilizing section is horizontally moved to be taken off from the bridge pier, so that the stabilizing section can be integrally removed.

[0022] Preferably, the column is provided with a connecting block, the connecting block comprising a fixed part and a trapezoidal part, one side of the fixed part is fixed on the column, the other side is fixedly connected with the trapezoidal part, a through hole is formed on one side of the upper base of the trapezoidal part, a connecting pin is inserted into the through hole, an end of the horizontal pull rod is provided with a connecting hole for cooperating with the connecting block, and the position of the trapezoidal part provided with the connecting pin extends out of the connecting hole.

[0023] By adopting the above technical scheme, the connecting block is fixed on the side wall of the column, and the trapezoidal part of the connecting block can cooperate with the connecting hole on the horizontal pull rod, so that the end of the horizontal pull rod is firmly connected with the connecting block and is convenient to disassemble. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 is a schematic diagram of the overall structure of the embodiment of the application;

[0025] Fig. 2 is a schematic diagram of the installation structure of the temporary support of the pier column beam in the embodiment of the application;

[0026] Fig. 3 is a schematic diagram of the installation position of the force relieving assembly in the embodiment of the application;

[0027] Fig. 4 is an exploded schematic diagram of the support column in the embodiment of the application;

[0028] Fig. 5 is a schematic diagram of the installation position of the connecting block in the embodiment of the application;

[0029] Fig. 6 is a schematic diagram of the structure of the horizontal pull rod in the embodiment of the application.

[0030] Reference signs: 1, end section; 2, middle section; 3, temporary support of the pier top beam; 31, support column; 311, adjusting section; 312, stabilizing section; 3121, stabilizing rod; 3122, column; 3123, horizontal pull rod; 32, connecting table; 321, distribution beam; 322, connecting beam; 323, connecting disc; 324, connecting screw; 33, force relieving assembly; 331, outer cylinder; 332, inner column; 333, outlet; 334, plug; 4, lifting equipment; 41, triangular truss; 42, vertical oil cylinder; 5, subway track; 6, bridge pier; 61, bearing platform; 7, SPMT module vehicle; 8, connecting block; 81, fixed part; 82, trapezoidal part; 821, through hole; 83, connecting pin; 9, connecting hole. DETAILED DESCRIPTION

[0031] The application will be further described below in combination with Figs. 1-6.

[0032] The application discloses a steel box girder hoisting process. Referring to FIG. 1, the pier top beam of the steel box girder structure is divided into three sections along the width direction of the road, the section above the pier top is an end section 1, and the middle section is a middle section 2. The steel box girder hoisting process comprises erection of temporary supports 3 of the pier top beam, hoisting of the end section 1, hoisting of lifting equipment 4, hoisting of the middle section 2 and removal of the temporary supports 3 of the pier top beam.

[0033] Referring to FIG. 1, two subway tracks 5 are arranged below the ground, and two bridge piers 6 for supporting the pier top beam are arranged on the ground, and the two bridge piers 6 are arranged at intervals. Since the total weight of the pier top beam needs a large crane, and the large crane cannot be used on site, the pier top beam is divided into three sections, and the two end sections 1 formed have smaller weights, and can be hoisted by a truck crane. Therefore, during construction, the temporary supports 3 of the pier top beam are first arranged at the positions of the bridge piers 6, the bottom of each bridge pier 6 is provided with a bearing platform 61, and the bearing platform 61 is supported by a plurality of columns inserted into the ground. The temporary supports 3 of the pier top beam extend upward from the upper surface of the bearing platform 61 until they are 5-10 cm above the top of the bridge pier 6, and then the two end sections 1 are hoisted by a truck crane. In this process, a suitable truck crane is selected according to the ground bearing condition, and the mass of the end section 1 is less than the maximum mass that can be hoisted by the truck crane. At the same time, the length of the end section 1 needs to exceed the side of the bridge pier 6 close to the middle section 2, and the side of the temporary supports 3 of the pier top beam close to the middle section 2 is below the side of the end section 1 close to the middle section 2, and the distance between them is A1. The hoisting of the two end sections 1 is completed.

[0034] Referring to FIG. 1, the lifting equipment 4 comprises a triangular truss 41 and a vertical oil cylinder 42, the vertical oil cylinder 42 is fixed on the triangular truss 41, the triangular truss 41 is fixed on the upper surface of the end section 1, the support point of the side of the triangular truss 41 close to the vertical oil cylinder 42 is the force position of the triangular truss 41 on the upper surface of the end section 1, the distance between the support point and the end of the end section 1 close to the middle section is A2, and A2=A1. The vertical oil cylinder 42 is located on the triangular truss 41 and above the vertical oil cylinder 42, and the position above the vertical oil cylinder 42 exceeds the end section 1, facilitating the vertical hoisting of the middle section 2 by the vertical oil cylinder 42. When the lifting equipment 4 is hoisted, the triangular truss 41 is first hoisted by the truck crane, then the triangular truss 41 is fixed on the upper surface of the end section 1, and then the vertical oil cylinder 42 is fixed on the upper surface of the side of the triangular truss 41 close to the middle section 2. In this way, the hoisting of the lifting equipment 4 is completed.

[0035] Referring to Fig. 1, the middle segment 2 is too heavy to be lifted by a truck crane or a large crane, so the middle segment 2 is lifted by the lifting devices 4 installed on the end segments 1. The movement of the middle segment 2 on site needs the help of the SPMT module trucks 7, in this embodiment, three SPMT module trucks 7 are used to support under the middle segment 2, so that the middle segment 2 is moved to be directly below the middle position between the two end segments 1. Then the lifting ropes on the vertical oil cylinders 42 are connected to the middle segment 2. By the synchronous work of the multiple lifting devices 4 on the two end segments 1, the middle segment 2 is kept in a horizontal state and is lifted upward until the two ends of the middle segment 2 are aligned with the connection positions of the end segments 1, then the middle segment 2 is welded with the end segments 1, so that the two ends of the middle segment 2 are supported on the temporary supports 3 of the pier top beam by the end segments 1, thereby completing the lifting of the middle segment 2.

[0036] Referring to Figs. 2 and 3, the temporary support 3 of the pier top beam includes a support column 31, a connecting table 32 and a force relieving assembly 33. The support column 31 is vertically arranged, the lower end of the support column 31 is connected to the bearing platform 61, and the upper end of the support column 31 is used to fixedly connect the connecting table 32, and the upper surface of the connecting table 32 is used to place the force relieving assembly 33. The force relieving assembly 33 includes an outer cylinder 331 and an inner column 332, the lower part of the outer cylinder 331 is provided with an outlet 333, the outlet 333 is threadedly connected with a plug 334, and when assembled, the sand that can flow out of the outlet 333 is first filled into the inner part of the outer cylinder 331, and then the inner column 332 is inserted into the outer cylinder 331, so that the force relieving assembly 33 is integrated. The erection of the temporary support 3 of the pier top beam includes: fixing one end of the plurality of support columns 31 on the bearing platform 61, then lifting the assembled connecting table 32 to the upper end of the support column 31 and fixing the connecting table 32 on the support column 31, so that the support column 31 is kept in a stable vertical state through the connecting table 32. The integrated force relieving assembly 33 is vertically placed on the upper surface of the connecting table 32, so that the upper end of the force relieving assembly 33 after the sand is filled in the inner part is higher than the upper end of the pier 6, and when the sand in the inner part of the force relieving assembly 33 flows out of the outlet 333, the upper end of the force relieving assembly 33 is lower than the upper end of the pier 6, thereby completing the erection of the temporary support 3 of the pier top beam.

[0037] Referring to FIGS. 2 and 3, the connecting platform 32 comprises a plurality of distribution beams 321 and connecting beams 322, the distribution beams 321 are formed by welding two H-shaped steels side by side, and the distribution beams 321 are vertically arranged with the connecting beams 322. The lower surface of the distribution beam 321 is provided with a connecting disc 323, a plurality of vertically downward connecting screws 324 are fixedly arranged on the connecting disc 323, and the connecting disc 323 is fixed with the supporting column 31 through the connecting screws 324. A plurality of distribution beams 321 are arranged in parallel and at intervals, the connecting beam 322 is located between two distribution beams 321, at least two connecting beams 322 are arranged between two adjacent distribution beams 321, the connecting beam 322 is used to stabilize the position of the distribution beam 321, and the force relieving assembly 33 is located on the distribution beam 321. The connecting beam 322 is disconnected in the middle and connected through a flange structure, and the two ends of the connecting beam 322 are welded on the side surfaces of two distribution beams 321 respectively. When the temporary support 3 of the pier top beam is removed, the plug 334 on the force relieving assembly 33 is first opened, so that a plurality of force relieving assemblies 33 start to flow out the sand in the interior at the same time, the gravity of the pier top beam is transferred from the temporary support 3 of the pier top beam to the pier 6, and the upper end of the force relieving assembly 33 is separated from the lower surface of the pier top beam with the flow-out of the sand, then the force relieving assembly 33 is directly taken off from the connecting platform 32, the connecting beam 322 is disconnected from the flange structure, so that the connecting platform 32 is removed from the supporting column 31, and finally the supporting column 31 is taken off from the bearing platform 61, so that the temporary support 3 of the pier top beam is removed, and the next use of the supporting column 31 is facilitated.

[0038] Referring to FIG. 4, the support column 31 comprises a stabilizing section 312 and an adjusting section 311. The stabilizing section 312 comprises a plurality of upright columns 3122 and stabilizing rods 3121 connected between the upright columns 3122, which can be made of channel steel. The stabilizing rods 3121 are forked and welded at both ends to the upright columns 3122. The plurality of upright columns 3122 are arranged in a grid and connected by the plurality of stabilizing rods 3121. A detachable horizontal tie rod 3123 is arranged on the stabilizing section 312. The adjusting section 311 can be set to different lengths as needed so that the total height of the support column 31 can be adapted to the height of the pier 6. The adjusting section 311 is arranged at both the upper and lower ends of the upright column 3122 to reduce the length of the adjusting section 311 and facilitate installation of the adjusting section 311. One end of the adjusting section 311 is connected to the end of the upright column 3122 by insertion and the adjusting section 311 abuts the end of the upright column 3122. The adjusting section 311 at the lower end of the upright column 3122 is fixed to the bearing platform 61 and the adjusting section 311 at the upper end is connected to the connecting screw 324 on the connecting disc 323. When the support column 31 is removed, the adjusting section 311 at the upper end of the upright column 3122 is pulled upward, the horizontal tie rod 3123 on the stabilizing section 312 is removed, and then the stabilizing section 312 is lifted as a whole to disengage from the adjusting section 311 below the upright column 3122, and the stabilizing section 312 is moved horizontally to disengage from the pier 6 at the position where the horizontal tie rod 3123 is removed.

[0039] Referring to FIGS. 5 and 6, a connecting block 8 is arranged at the position where the horizontal tie rod 3123 is installed on the upright column 3122, which is welded and fixed to the side wall of the upright column 3122. Both ends of the horizontal tie rod 3123 are detachably connected to the upright column 3122 through the connecting block 8. The connecting block 8 comprises a fixed portion 81 and a trapezoidal portion 82. One end of the fixed portion 81 is fixed to the upright column 3122 and the other end is used to fix the trapezoidal portion 82 so that the trapezoidal portion 82 is spaced apart from the upright column 3122. The trapezoidal portion 82 is larger in shape than the fixed portion 81. A through hole 821 is formed in one side of the upper base of the trapezoidal portion 82 and a connecting pin 83 is inserted into the through hole 821. The end of the horizontal tie rod 3123 is provided with a curved surface structure, which abuts the side wall of the upright column 3122. A connecting hole 9 is formed in the end of the horizontal tie rod 3123 for cooperation with the connecting block 8, and the position where the trapezoidal portion 82 is provided with the connecting pin 83 extends from the connecting hole 9. During installation, the two ends of the horizontal tie rod 3123 are first clamped to the two connecting blocks 8, and then the connecting pin 83 is inserted into the through hole 821. During removal, the connecting pin 83 is first removed from the through hole 821, and then the horizontal tie rod 3123 is moved toward the smaller end of the trapezoidal portion 82 so that the horizontal tie rod 3123 is disengaged from the connecting block 8.

[0040] The above are all preferred embodiments of the present application, and do not limit the protection scope of the present application, so that: all equivalent changes made according to the structure, shape, principle of the present application should be covered in the protection scope of the present application.

Claims

1. A steel box girder hoisting process, characterized in that... include: The pier top crossbeam of the steel box girder structure is divided into three sections along the width of the road: the end sections (1) at both ends and the middle section (2) between the two end sections (1). Two piers (6) are set at intervals to support the pier top crossbeam. First, temporary supports (3) for the pier top crossbeam are erected on the piers (6) so that the height of the temporary supports (3) for the pier top crossbeam is higher than that of the piers (6). Then, the two end sections (1) are hoisted to the upper end of the temporary supports (3) for the pier top crossbeam by a truck crane. Then, the lifting equipment (4) is hoisted to the upper surface of the end section (1) by a truck crane and installed. Then, the lifting equipment (4) on the two end sections (1) is used to lift both ends of the middle section (2) at the same time. After the middle section (2) reaches the position to dock with the end section (1), the middle section (2) and the end section (1) are connected. Finally, the temporary supports (3) for the pier top crossbeam are removed so that the weight of the pier top crossbeam is transferred to the piers (6).

2. The steel box girder hoisting process according to claim 1, characterized in that: The temporary support (3) of the pier top beam is located below the end segment (1) on the side closer to the middle segment (2) and the distance between the end segment (1) and the side closer to the middle segment (2) is A1. The support of the lifting device (4) is located at the distance between the end segment (1) and the middle segment (2), and A2 is equal to A1.

3. The steel box girder hoisting process according to claim 1, characterized in that: Before the lifting equipment (4) lifts both ends of the middle section (2) at the same time, the middle section (2) is transported by the SPMT module vehicle (7) so that the middle section (2) is moved to the middle position of the two end sections (1) directly below, where the SPMT module vehicle (7) is supported under the middle section (2).

4. The steel box girder hoisting process according to claim 1, characterized in that: The temporary support (3) of the pier top beam includes multiple vertically arranged support columns (31), a connecting platform (32) located at the upper end of the support column (31), and multiple unloading components (33). The unloading components (33) are placed on the upper surface of the connecting platform (32). The unloading components (33) include an outer cylinder (331) and an inner column (332). The interior of the outer cylinder (331) is used to fill sand. An outlet (333) is opened at the lower part of the outer cylinder (331). A plug (334) is threadedly connected to the outlet (333). The lower end of the inner column (332) is inserted into the outer cylinder (331).

5. The steel box girder hoisting process according to claim 4, characterized in that: The connecting platform (32) includes mutually perpendicular distribution beams (321) and connecting beams (322). The lower surface of the distribution beams (321) is used to connect to the upper end of the support column (31). Multiple distribution beams (321) are arranged parallel to each other and spaced apart. The two ends of the connecting beams (322) are welded and fixed to the sides of the distribution beams (321) respectively. The middle part of the connecting beams (322) is broken and connected by a flange structure.

6. The steel box girder hoisting process according to claim 5, characterized in that: When removing the temporary support (3) of the pier top beam, first open the plug (334) at the outlet (333) so that sand flows out of multiple stress relief components (33) at the same time. After the weight of the pier top beam is transferred to the pier (6), the sand inside the stress relief component (33) continues to flow out, so that the upper end of the inner column (332) is separated from the lower surface of the pier top beam. Then remove the stress relief component (33) from the connecting platform (32), then disconnect the connecting beam (322) from the flange structure and remove the connecting platform (32).

7. The steel box girder hoisting process according to claim 4, characterized in that: The support column (31) includes a stabilizing section (312) and an adjusting section (311). The stabilizing section (312) includes multiple columns (3122) and a stabilizing rod (3121) connecting the columns (3122). The multiple columns (3122) are fixedly connected by the stabilizing rod (3121). A horizontal tie rod (3123) is detachably connected to one side of the stabilizing section (312). The adjusting section (311) is inserted into the upper and lower ends of the columns (3122).

8. The steel box girder hoisting process according to claim 7, characterized in that: The removal of the temporary support (3) of the pier top beam includes the removal of the support column (31). When removing the support column (31), first pull the adjustment section (311) at the top of the column (3122) upward, then remove the horizontal tie rod (3123), then lift the stabilizing section (312) as a whole, and move the stabilizing section (312) horizontally to remove it from the pier (6) from the position where the horizontal tie rod (3123) was removed.

9. The steel box girder hoisting process according to claim 7, characterized in that: The column (3122) is provided with a connecting block (8), which includes a fixing part (81) and a trapezoidal part (82). One side of the fixing part (81) is fixed to the column (3122), and the other side is fixedly connected to the trapezoidal part (82). A through hole (821) is provided on the upper bottom side of the trapezoidal part (82), and a connecting pin (83) is inserted into the through hole (821). A connecting hole (9) is provided at the end of the horizontal tie rod (3123) for cooperating with the connecting block (8), and the position of the connecting pin (83) on the trapezoidal part (82) extends out from the connecting hole (9).

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