Bridge underneath pass construction channel device and mounting and dismounting method thereof

Abstract

The bridge underpass construction channel device comprises a U-shaped prefabricated box, the U-shaped prefabricated box comprises a supporting part and water retaining parts arranged on the two sides of the supporting part, the supporting part and the two water retaining parts define a temporary channel with an opening in the top, and the supporting part and the water retaining parts each comprise a plurality of empty cabins; each empty cabin is configured to selectively introduce ballast capable of adjusting the weight of the U-shaped prefabricated box; and the counterweight structure is used for being detachably mounted on the top surface of each water retaining part. The device has the advantages of being rapid in deployment, low in cost, high in stability and convenient and fast to install, and the construction efficiency and economic benefits are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of engineering construction, in particular to a bridge underpass construction channel device and an installation and disassembly method thereof. Background Art

[0002] When constructing bridges in shallow water areas, traditional methods often use structures such as cofferdam islands, steel trestles or temporary supports as construction channels. However, the existing technologies have the following shortcomings: the traditional cofferdam method requires a large amount of fill, sandbags and protective structures, with a long construction period and high material consumption and construction costs; when the steel trestles are deployed under low bridges, they cannot be deployed due to the height of the bridge. For example, in some scenarios, the passage height under the bridge is only a few meters, and the bottom of the construction channel needs to be below the waterline, which makes construction difficult. Some devices have poor adaptability to the complex terrain of shallow water areas (such as soft soil foundations and water level fluctuations), which can easily cause the risk of settlement or structural instability and have poor environmental adaptability; in addition, the installation of existing channel devices usually requires the assistance of large machinery, and construction machinery cannot reach under low bridges, which makes installation difficult; temporary channels are usually difficult to dismantle, and it is difficult to clean up the remaining structures after dismantling, which affects the water ecology and subsequent navigation.

[0003] Therefore, there is an urgent need to develop a temporary passage device under low bridges in shallow water areas. Summary of the invention

[0004] In view of the defects of the above-mentioned prior art, the present invention provides a bridge underpass construction channel device and its installation and disassembly method which have simple structure, high construction efficiency, low cost and easy dismantling. The device is installed under the bridge in shallow water area and is used as a temporary channel for transporting personnel, equipment and materials during engineering construction, so as to improve construction safety and economy.

[0005] The present invention is implemented by the following technical solutions:

[0006] A bridge underpass construction channel device, comprising:

[0007] A U-shaped prefabricated box comprises a support portion and water retaining portions arranged on both sides of the support portion, wherein the support portion and the two water retaining portions enclose a temporary passage with an open top, and the support portion and the water retaining portion each comprise a plurality of empty compartments, each of the empty compartments being configured to selectively admit ballast capable of adjusting the weight of the U-shaped prefabricated box;

[0008] The counterweight structure is used for being detachably mounted on the top surface of each of the water retaining parts.

[0009] Furthermore, the ballast is concrete or water.

[0010] Furthermore, the counterweight structure includes two waterproof steel plates, which are vertically installed on the top surface of the water retaining part to enclose a counterweight cavity, and several layers of counterweight objects are placed in the counterweight cavity.

[0011] Further, the temporary passage includes an inlet port and an outlet port, and end sealing doors are detachably installed at both the inlet port and the outlet port.

[0012] Further, valves are configured for each of the end sealing doors.

[0013] Further, a high water level line is provided on the counterweight structure, and a high-level connecting pipe for communicating with the temporary passage is provided on the counterweight structure, and the height of the position where the high-level connecting pipe is located is higher than the height of the position where the high water level line is located.

[0014] Further, a drainage well is provided in the temporary passage, and a drainage pump for discharging the water entering the temporary passage to the outside is provided in the drainage well.

[0015] Further, a low water level line is provided on the U-shaped precast box, and the height of the top surface of the water retaining part is higher than the height of the position where the low water level line is located.

[0016] A method for installing and dismantling a bridge underpass construction passage device, including the above-mentioned bridge underpass construction passage device, and the installation and dismantling method is as follows:

[0017] Step 1: First, use a floating crane to lift the U-shaped precast box on the barge onto the water, then tow the U-shaped precast box to the vicinity of the target bridge by a tugboat and anchor it, and then pour concrete into the empty compartments of the support part and part of the empty compartments of the water retaining part;

[0018] Step 2: Take advantage of the tide level to tow the U-shaped precast box to the bottom of the target bridge, open the valves on the end sealing doors, inject water into the temporary passage, and the U-shaped precast box sinks onto the foundation;

[0019] Step 3: After the U-shaped precast box reaches the installation position, fill the remaining empty compartments of the water retaining part with water;

[0020] Step 4: Weld a waterproof steel plate on the top surface of the water retaining part and stack counterweights in the counterweight cavity;

[0021] Step 5: Connect the temporary passage to the water stop wall, take water stop measures, evacuate the water stored in the temporary passage, remove the end sealing doors, and put the temporary passage into use;

[0022] Step 6: After the construction work is completed, install the end sealing doors of the temporary passage, inject water into the temporary passage, after the injection is completed, then remove the waterproof steel plate and the counterweights, and finally evacuate the water in the temporary passage, and the U-shaped precast box floats up and is pulled out.

[0023] Further, in Step 4, before the stacking of the counterweights is completed, keep the temporary passage communicating with the outside water.

[0024] Compared with the prior art, the beneficial effects of the present invention at least include:

[0025] (1) The present invention forms a temporary passage for construction vehicles through a U-shaped precast box, and adjusts the weight of the U-shaped precast box by introducing ballast into the empty compartment, facilitating the floating and sinking of the U-shaped precast box. After the U-shaped precast box sinks under the underwater foundation, a counterweight structure is installed to ensure that the U-shaped precast box has sufficient weight to resist buoyancy, so that the U-shaped precast box will not float, shift, or collide with surrounding structures (such as bridge piers and bridge bottom surfaces) due to rising tides, ensuring the normal use of the temporary passage. This device has the characteristics of rapid deployment, low cost, high stability, and convenient installation, greatly improving the construction efficiency and economic benefits.

[0026] (2) During the installation stage of the bridge underpass construction passage device of the present invention, the weight of the U-shaped precast box is adjusted by introducing concrete and water into the empty compartment, enabling the U-shaped precast box to sink to the designated installation position. By using water and concrete as the gravity source for sinking, the materials of the gravity source are not only easily obtained but also low-cost and do not need to be recycled. At the same time, combined with the installation of the counterweight structure, the U-shaped precast box has high buoyancy resistance, ensuring high stability of the bridge underpass construction passage device, and solving the problem that the installation of existing temporary passage devices usually requires the assistance of large machinery, while construction machinery cannot reach under low bridges.

[0027] (3) During the demolition stage of the bridge underpass construction passage device of the present invention, first install the end seal door, dig a gap in the water stop wall to connect the temporary passage with the outside world, fill the temporary passage with water to prevent the U-shaped precast box from floating during the demolition stage. After the water injection is completed, remove the counterweight and waterproof steel plate, and finally pump out the water in the temporary passage. The U-shaped precast box floats with the tide and is pulled out from the bottom of the bridge, realizing the convenient and low-cost demolition of the bridge underpass construction passage device. It solves the problems of difficult demolition of existing temporary passages, difficult cleaning of residual structures after demolition, affecting the water area ecology, and subsequent navigation. Description of the Drawings

[0028] Figure 1 is the cross-sectional view of the bridge underpass construction passage device of Embodiment 1 of the present invention;

[0029] Figure 2 is the longitudinal sectional view of the bridge underpass construction passage device of Embodiment 1 of the present invention;

[0030] Figure 3 is the cross-sectional view of the bridge underpass construction passage device of Embodiment 1 of the present invention placed under the bridge;

[0031] Figure 4 is the longitudinal sectional view of the bridge underpass construction passage device of Embodiment 1 of the present invention placed under the bridge;

[0032] Figure 5 It is a schematic diagram of Step 1 of the installation and disassembly method of the bridge underpass construction channel device according to Embodiment 2 of the present invention;

[0033] Figure 6 It is a schematic diagram of Step 1 of the installation and disassembly method of the bridge underpass construction channel device according to Embodiment 2 of the present invention;

[0034] Figure 7 It is a schematic diagram of Step 2 of the installation and disassembly method of the bridge underpass construction channel device according to Embodiment 2 of the present invention;

[0035] Figure 8 It is a schematic diagram of Step 3 of the installation and disassembly method of the bridge underpass construction channel device according to Embodiment 2 of the present invention;

[0036] Figure 9 It is a schematic diagram of Step 4 of the installation and disassembly method of the bridge underpass construction channel device according to Embodiment 2 of the present invention;

[0037] Figure 10 It is a schematic diagram of Step 5 of the installation and disassembly method of the bridge underpass construction channel device according to Embodiment 2 of the present invention;

[0038] In the figure: 1, U-shaped precast box; 10, support part; 11, water retaining part; 12, temporary passage; 13, empty cabin; 14, end sealing door; 15, valve; 16, low water level line; 17, high water level line; 18, drainage well; 19, high-level connecting pipe; 2, counterweight structure; 21, waterproof steel plate; 22, counterweight; 3, construction vehicle; 4, bridge; 5, water surface; 6, foundation; 7, water stop wall. Detailed implementation manners

[0039] Now, example embodiments will be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this invention will be more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote the same or similar structures, and thus their repetitive description will be omitted.

[0040] The words expressing positions and directions described in the present invention are all illustrated by taking the accompanying drawings as examples, but can be changed according to needs, and all the changes made are included in the protection scope of the present invention.

[0041] As Figures 1 to 4 shown, a bridge underpass construction channel device provided by the present invention includes:

[0042] U-shaped precast box 1, which includes a support part 10 and water retaining parts 11 arranged on both sides of the support part 10. The support part 10 and the two water retaining parts 11 enclose a temporary passage 12 with an open top. The support part 10 and the water retaining parts 11 both include a plurality of empty compartments 13, and each of the empty compartments 13 is configured to selectively admit ballast that can adjust the weight of the U-shaped precast box 1;

[0043] Counterweight structure 2, which is used for detachably installing on the top surfaces of the respective water retaining parts 11.

[0044] In this embodiment, the U-shaped precast box 1 is prefabricated in a factory. The area enclosed by the support part 10 and the two water retaining parts 11 is a temporary passage 12 for construction vehicles 3 to pass through. The water retaining parts 11 can block the water from the outside from entering the temporary passage 12. Each of the empty compartments 13 is configured to selectively admit ballast that can adjust the weight of the U-shaped precast box 1. In this way, the weight of the U-shaped precast box 1 is adjusted by adjusting the weight of the ballast admitted into the empty compartments 13, facilitating the floating and sinking of the U-shaped precast box 1.

[0045] It can be understood that when the empty compartments 13 of the U-shaped precast box 1 do not admit ballast, it is convenient to transport the U-shaped precast box 1 from the factory to the construction site. During floating towing, the requirement for the water depth of the water area is also relatively low. When a certain amount of ballast is loaded into the U-shaped precast box 1, the gravity of the U-shaped precast box 1 is greater than the buoyancy, enabling it to sink on the foundation 6 in the shallow water area.

[0046] After the U-shaped precast box 1 is pulled to the installation position, the counterweight structure 2 is installed. At this time, the temporary passage 12 of the U-shaped precast box 1 accumulates water, and the U-shaped precast box 1 loses part of its buoyancy. Then, a certain amount of ballast is admitted into the empty compartments 13 of the U-shaped precast box 1, making the gravity of the U-shaped precast box 1 greater than the buoyancy, so that the overall structure will not float. The counterweight structure 2 is installed on the top of the water retaining parts 11, thus ensuring that the U-shaped precast box 1 has enough weight to resist the buoyancy and avoid floating.

[0047] The U-shaped precast box 1 of the present invention forms a temporary passage 12 for construction vehicles 3 to pass through, and adjusts the weight of the U-shaped precast box 1 by admitting ballast into the empty compartments 13, facilitating the rapid floating and sinking of the U-shaped precast box 1. After the U-shaped precast box 1 sinks underwater on the foundation 6, combined with the counterweight structure 2, it ensures that the U-shaped precast box 1 has enough weight to resist the buoyancy, so that the U-shaped precast box 1 will not float, shift, or collide with surrounding structures (such as bridge piers, bridge bottom surfaces) due to rising tides, ensuring the normal use of the temporary passage 12. Therefore, the bridge underpass construction passage device of the present invention has the characteristics of rapid deployment, low cost, high stability, and convenient installation, greatly improving the construction efficiency and economic benefits.

[0048] The bridge underpass construction channel device of the present invention is for the installation and removal under low bridges 4 in shallow water areas, especially in coastal areas affected by tides with large water level changes. It should have the characteristics of rapid deployment, low cost, high stability and convenient removal.

[0049] As a preferred embodiment, the ballast is concrete or water.

[0050] In this embodiment, water and concrete are used as the ballast sources for the sinking of the U-shaped precast box 1. The materials of the ballast sources are not only easily obtained, but also low in cost and do not need to be recycled, reducing the installation cost. Without the assistance of large machinery for floating, the installation cost is reduced. Specifically, since the support part 10 is supported on the foundation 6 and the construction vehicle 3 travels on the support part 10, when the empty compartment 13 of the support part 10 is filled with concrete, it can ensure that the support part 10 has high strength characteristics and at the same time ensure that the U-shaped precast box 1 stably sinks to the installation position; for the water retaining part 11, some of the empty compartments 13 are filled with concrete and some are filled with water, so that the weight of the U-shaped precast box 1 can be flexibly adjusted, increasing the flexibility of adjustment and improving the versatility and expandability of the U-shaped precast box 1.

[0051] As a preferred embodiment, the counterweight structure 2 includes two waterproof steel plates 21 which are vertically installed on the top surface of the water retaining part 11 to enclose a counterweight cavity, and several layers of counterweights 22 are placed in the counterweight cavity.

[0052] In this embodiment, when the U-shaped precast box 1 reaches the set installation position, waterproof steel plates 21 are welded on the top surface of the water retaining part 11, and several layers of counterweights 22 are stacked between the waterproof steel plates 21 to ensure that the U-shaped precast box 1 has a large buoyancy resistance. After the counterweight structure 2 is installed, the construction channel outside the scope of the bridge 4 is connected, and water stop is done, and the temporary channel 12 is closed. At this time, the water in the temporary channel 12 is drained by a submersible pump. After the water is drained, the end seal door 14 is removed, and at this time the temporary channel 12 can be put into use.

[0053] It can be understood that the counterweights 22 can be concrete, sandbags, steel blocks or other high-density materials with low cost. The waterproof steel plates 21 on both sides of the counterweights 22 can prevent water from seeping into the temporary channel 12.

[0054] As a preferred embodiment, the temporary channel 12 includes an inlet port and an outlet port, and end seal doors 14 are detachably installed at both the inlet port and the outlet port.

[0055] In this embodiment, the end seal door 14 is provided during the installation and demolition stages and removed during the use stage. Specifically, the removal of the end seal door 14 is carried out after the installation of the counterweight structure 2. After installing the end seal door 14, the drainage shape of the U-shaped precast box 1 changes from U-shaped to square, increasing the drainage volume of the structure during the installation and demolition stages, obtaining a greater buoyancy, and facilitating the installation and demolition work.

[0056] As a preferred embodiment, each of the end seal doors 14 is configured with a valve 15.

[0057] In this embodiment, when the valve 15 is opened, it can connect the temporary passage 12 with the external water to facilitate rapid filling or drainage. Before the U-shaped precast box 1 is in place for installation, a certain amount of water and concrete can be introduced into the empty compartment 13 first, so that when the valve 15 is closed, the U-shaped precast box 1 has a certain freeboard and can float by itself. At this time, the U-shaped precast box 1 can be towed to the installation position. When the valve 15 is opened, the external water fills the temporary passage 12, the temporary passage 12 loses buoyancy, the buoyancy received by the U-shaped precast box 1 is less than the gravity, and the U-shaped precast box 1 can sink to the installation position without floating, shifting, or colliding with the surrounding structures (such as bridge piers, bridge bottoms, etc.) due to the rising tide. Since the period of the ebb and flow of the tide is short, the design of the valve 15 can greatly reduce the time for filling the temporary passage 12 with water and ensure the timely completion of the positioning of the U-shaped precast box 1.

[0058] As a preferred embodiment, the counterweight structure 2 is provided with a high water level line 17, and the counterweight structure 2 is provided with a high-level connecting pipe 19 for communicating with the temporary passage 12, and the height of the position where the high-level connecting pipe 19 is located is higher than the height of the position where the high water level line 17 is located.

[0059] In this embodiment, when the external water surface 5 is higher than the height of the high water level line 17, the external water is filled into the temporary passage 12 through the high-level connecting pipe 19, and the temporary passage 12 loses buoyancy, preventing the device from floating and colliding with other structures at extremely high water levels.

[0060] As a preferred embodiment, a drainage well 18 is provided in the temporary passage 12, and a drainage pump for discharging the water entering the temporary passage 12 to the outside is provided in the drainage well 18.

[0061] In this embodiment, by providing the drainage well 18 and the drainage pump, the rainwater entering the temporary passage 12 and the water entering the temporary passage 12 at extremely high water levels can be discharged, ensuring the normal use of the temporary passage 12.

[0062] As a preferred embodiment, the U-shaped precast box 1 is provided with a low water level line 16, and the height of the position where the top surface of the water retaining part 11 is located is higher than the height of the position where the low water level line 16 is located. In this way, the water retaining part 11 can prevent the water from the outside from entering the temporary passage 12, so that the construction vehicle 3 can pass through the temporary passage 12.

[0063] Embodiment 2

[0064] As Figures 5 to 10 shown, a method for installing and disassembling a bridge underpass construction passage device provided by the present invention includes the above-mentioned bridge underpass construction passage device, and the installation and disassembly method is as follows:

[0065] Step 1: First, use a floating crane to lift the U-shaped precast box 1 on the barge onto the water surface 5, then tow the U-shaped precast box 1 to the vicinity of the target bridge 4 by a tow head for anchoring, and then pour concrete into the empty compartments 13 of the support part 10 and part of the empty compartments 13 of the water retaining part 11;

[0066] Step 2: Tow the U-shaped precast box 1 to the bottom of the target bridge at the rising tide, open the valve 15 on the end seal door 14, inject water into the temporary passage 12, and the U-shaped precast box 1 sinks onto the foundation 6;

[0067] Step 3: After the U-shaped precast box 1 reaches the installation position, fill the remaining empty compartments 13 of the water retaining part 11 with water;

[0068] Step 4: Weld a waterproof steel plate 21 on the top surface of the water retaining part 11, and stack weights 22 in the counterweight cavity;

[0069] Step 5: Connect the temporary passage 12 to the water stop wall 7, take water stop measures, evacuate the water in the temporary passage 12, remove the end seal door 14, and the temporary passage 12 is put into use;

[0070] Step 6: After the construction work is completed, install the end seal door 14 of the temporary passage 12, inject water into the temporary passage 12, after the injection is completed, then remove the waterproof steel plate 21 and the weights 22, and finally evacuate the water in the temporary passage 12, and the U-shaped precast box 1 floats and is pulled out.

[0071] In this embodiment, during the installation stage of the bridge underpass construction passage device, the weight of the U-shaped precast box 1 is adjusted by injecting concrete and water into the empty compartments 13, so that the U-shaped precast box 1 can sink to the designated installation position. At the same time, combined with the installation of the counterweight structure 2, it is ensured that the U-shaped precast box 1 will not float, shift, or collide with surrounding structures (such as bridge piers, bridge bottom surfaces, etc.) due to the rising tide, ensuring the high stability of the bridge underpass construction passage device, and solving the problem that the installation of the existing temporary passage 12 device usually requires the assistance of large machinery, while the construction machinery cannot reach under low bridges.

[0072] During the demolition stage of the bridge underpass construction passage device, first install the end seal door 14, dig a notch in the water stop wall 7 to connect the temporary passage 12 with the outside, pour water into the temporary passage 12 to prevent the U-shaped precast box 1 from floating during the demolition stage. After the water injection is completed, remove the counterweight 22 and the waterproof steel plate 21. Finally, pump out the water in the temporary passage 12, and the U-shaped precast box 1 floats up with the tide and is pulled out from the bottom of the bridge, realizing the convenient and low-cost demolition of the bridge underpass construction passage device. This solves the problems that the existing temporary passage 12 is difficult to demolish, the residual structure is difficult to clean up after demolition, and it affects the water area ecology and subsequent navigation.

[0073] As a preferred implementation manner, in step four, before the counterweight 22 is completely stacked, keep the temporary passage 12 connected to the outside water. This can prevent the U-shaped precast box 1 from floating under high water levels.

[0074] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Without departing from the principles and purposes of the present invention, those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the invention, and all these changes should fall within the protection scope of the claims of the present invention.

Claims

1. A bridge underpass construction passage device, characterized in that , including: A U-shaped precast box (1), which includes a support part (10) and water retaining parts (11) arranged on both sides of the support part (10). The support part (10) and the two water retaining parts (11) enclose a temporary passage (12) with an open top. The support part (10) and the water retaining parts (11) both include a plurality of empty compartments (13), and each empty compartment (13) is configured to selectively introduce ballast that can adjust the weight of the U-shaped precast box (1); A counterweight structure (2) for detachably installing on the top surface of each water retaining part (11).

2. The bridge underpass construction passage device according to claim 1, characterized in that, The ballast is concrete or water.

3. The bridge underpass construction passage device according to claim 1, characterized in that, The counterweight structure (2) includes two waterproof steel plates (21). The two waterproof steel plates (21) are vertically installed on the top surface of the water retaining part (11) to enclose a counterweight cavity, and several layers of counterweights (22) are placed in the counterweight cavity.

4. The bridge underpass construction passage device according to claim 1, characterized in that, The temporary passage (12) includes an inlet port and an outlet port, and end sealing doors (14) are detachably installed at both the inlet port and the outlet port.

5. The bridge underpass construction passage device according to claim 4, characterized in that, Each end sealing door (14) is configured with a valve (15).

6. The bridge underpass construction passage device according to claim 1, characterized in that, The counterweight structure (2) is provided with a high water level line (17). A high-level connecting pipe (19) for communicating with the temporary passage (12) is provided on the counterweight structure (2), and the height of the position where the high-level connecting pipe (19) is located is higher than the height of the position where the high water level line (17) is located.

7. The bridge underpass construction passage device according to claim 1, characterized in that, A drainage well (18) is provided in the temporary passage (12), and a drainage pump for discharging the water entering the temporary passage (12) to the outside is provided in the drainage well (18).

8. The bridge underpass construction passage device according to claim 1, characterized in that, The U-shaped precast box (1) is provided with a low water level line (16), and the height of the position where the top surface of the water retaining part (11) is located is higher than the height of the position where the low water level line (16) is located.

9. A method for installing and disassembling a construction passage device under a bridge, characterized in that, Including the bridge underpass construction passage device according to any one of claims 1-8, the installation and removal method is as follows: Step 1: First, use a floating crane to lift the U-shaped precast box (1) on the barge onto the water, then tow the U-shaped precast box (1) to the vicinity of the target bridge (4) by a tugboat and anchor it. Then, pour concrete into the empty compartments (13) of the support part (10) and some of the empty compartments (13) of the water retaining part (11); Step 2: Take advantage of the tide level to pull the U-shaped precast box (1) to the bottom of the target bridge, open the valve (15) on the end sealing door (14), inject water into the temporary passage (12), and the U-shaped precast box (1) sinks onto the foundation (6); Step 3: After the U-shaped precast box (1) reaches the installation position, fill the remaining empty compartments (13) of the water retaining part (11) with water; Step 4: Weld waterproof steel plates (21) on the top surface of the water retaining part (11), and stack counterweights (22) in the counterweight cavity; Step 5: Connect the temporary passage (12) to the water stop wall (7), take good water stop measures, evacuate the stored water in the temporary passage (12), remove the end sealing door (14), and put the temporary passage (12) into use; Step Six: After the construction work is completed, install the end seal door (14) of the temporary passage (12), fill the temporary passage (12) with water. After the water filling is completed, remove the waterproof steel plate (21) and the counterweight (22), and finally pump out the water in the temporary passage (12), and the U-shaped precast box (1) floats up and is pulled out.

10. The method for installing and disassembling the bridge underpass construction passage device according to claim 9, characterized in that: In Step Four, keep the temporary passage (12) in communication with the external water before the piling of the counterweight (22) is completed.

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