A method for the overall demolition of a half-span cantilever beam of a cross-river concrete continuous beam bridge

Abstract

This invention relates to a method for the overall demolition of a half-span cantilever beam of a cross-river concrete continuous beam bridge. The method involves erecting supports on two barges, filling their holds with ballast water to lower the supports below the beam's bottom. The two barges then navigate to the outer cantilever beams of each side span and anchor, draining some water to raise them and tighten the supports against the beam's bottom. The closure section between the two cantilever beams of the side span is then cut. The barges continue to drain water and raise themselves, buoying the outer cantilever beams of the side span to a designated location. Next, the closure section between the two cantilever beams of the middle span is cut. The two barges are again filled with ballast water and navigate to the sides of a middle span pier, simultaneously cutting the joint between the pier's top 0# block and the two cantilever beams, allowing the two cantilever beams to rest on the barge supports. Finally, a floating crane removes the 0# block. This invention allows for the one-time demolition of a half-span cantilever beam, resulting in high efficiency and minimal impact on river navigation; it can flexibly adapt to water level changes; and the demolition process causes minimal disturbance to the bridge structure, ensuring high safety.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology and relates to the reconstruction and demolition of dilapidated bridges across rivers. Specifically, it is a construction method for the overall demolition of a half-span cantilever beam of a cross-river concrete continuous beam bridge using the floating method. Background Technology

[0002] Concrete continuous beam bridges are a common type of bridge for crossing rivers due to their low cost and simple construction. However, as bridges age, quality problems gradually emerge in some of the earlier-built bridges, making them unable to meet the ever-growing traffic and safety demands, leading to a growing number of dilapidated bridges needing demolition. In addition, waterway upgrades, urban planning adjustments, and road reconstruction and expansion projects also involve the demolition of old bridges.

[0003] Currently, the three common methods for dismantling continuous beam bridges are the flow interruption support method, the cantilever dismantling method, and the floating support component dismantling method.

[0004] The flow-interruption support method involves first erecting supports under the bridge to support the beam, and then dismantling and breaking up the continuous concrete beam. This method has the following problems: First, it occupies the river channel for a long time and is not suitable for bridges on navigable waterways; second, when erecting supports under the bridge, the steel pipe piles of the supports need to be driven into the riverbed using a vibratory pile hammer, but due to the constraints of the beam, the construction space under the bridge is limited, making the operation difficult; third, the beam can only be dismantled into small pieces and transported away, resulting in low efficiency and high cost.

[0005] The cantilever demolition method is commonly used for the demolition of continuous beams constructed with hanging baskets. Following the reverse order of the continuous beam hanging basket construction sequence, the continuous beam is cut into sections and lowered to the ground under the bridge section by section using a bridge deck crane. This method has two drawbacks: first, it involves a large amount of cutting and a long construction period; second, it is not suitable for bridges with structural defects, because the stress on the bridge structure changes with each section of the cantilever is removed, and the tensile and compressive forces at the front and rear supports of the bridge deck crane will exacerbate the stress changes at the supports, which may lead to local concrete collapse and cause the bridge deck crane to overturn along with the sections.

[0006] Patent CN115247401A discloses a device and method for dismantling the steel structure support of floating bridge pontoons. This method involves setting up a row of floating pontoons under the bridge, erecting supports on the pontoons to support the bridge beam, and then gradually dismantling the beam in the order of top plate, bottom plate, and web plate. Compared to the support-based flow interruption method, this method has the advantage of not requiring additional supports to be erected on the riverbed. However, it also has the following drawbacks: firstly, it requires setting up floating pontoons under the entire span of the bridge, which affects river navigation; secondly, the dismantling construction period is long and inefficient; and thirdly, because the pontoons are fixedly connected to the piers, they cannot adapt to changes in water level. Therefore, it is only suitable for bridge dismantling construction where the water level remains constant during the construction period (generally at least three days). For rivers where the water level changes frequently due to tides and rainfall, it is difficult to complete the dismantling and dismantling of individual components within a single slack tide period. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing methods for demolishing cross-river continuous concrete beams by providing a method for the overall demolition of a half-span cantilever beam of a cross-river continuous concrete beam bridge, which significantly improves construction efficiency while ensuring construction safety.

[0008] The technical solution of the present invention is as follows:

[0009] A method for the overall demolition of a half-span cantilever beam of a cross-river concrete continuous beam bridge, characterized by the following steps:

[0010] (1) Frames are erected on the two barges respectively, and fixed top supports are installed on the top of the frames according to the cross-sectional dimensions of the bottom of the continuous beam; the initial height of the frames is higher than the bottom height of the beam.

[0011] (2) Inject ballast water into the holds of the two barges so that the height of the support is lower than the height of the bottom of the beam. Then, drive the two barges to the outer cantilever beams of the two spans of the bridge. Anchor the barges at the four corners of the barges to fix their positions. Gradually drain some water from the barges to raise them. While raising the barges, adjust the length of the anchor cables accordingly to keep the anchor cables taut and keep the barges in a fixed position until the support is firmly against the bottom of the beam.

[0012] (3) Use a wire saw to cut the closure section between the two cantilever beams of the side span on the bridge, then continue to drain the ballast water in the barge and adjust the length of the anchor cable at the same time. The barge rises by relying on buoyancy, and floats the cantilever beam on the outside of the side span to separate from the side span pier. Then the barge carries the cut cantilever beam to the designated location to dismantle and break the beam.

[0013] (4) Use a wire saw to cut off the closure section of the two cantilever beams between the two piers in the middle span, and set up steel pipe supports on the pier cap of each pier in the middle span to support the two ends of block 0 on the pier in the middle span.

[0014] (5) After injecting ballast water into the holds of the two barges so that the height of the supports on the barges is lower than the height of the bottom of the beam, the two barges sail into the area below the two sides of a mid-span pier. The barges use the same method as in step (2) to drain water and raise the supports so that the supports can support the cantilever beams on both sides of the mid-span pier. The joint between the pier top 0# block and the two cantilever beams is cut simultaneously with a wire saw so that the two cantilever beams fall onto the supports of the two barges. The two barges transport the cantilever beams to the designated dismantling location.

[0015] (6) Remove the cantilever beams on both sides of the other mid-span pier using the same method as in step (5);

[0016] (7) The No. 0 block on the two mid-span piers was removed by floating crane to complete the demolition of the entire bridge superstructure.

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

[0018] 1. The half-span cantilever beam can be removed in one go, which not only greatly improves construction efficiency, but also allows construction vessels to occupy only half the space under the bridge, minimizing the impact on river navigation.

[0019] 2. The demolition process causes minimal disturbance to the bridge structure and carries low safety risks, making it particularly suitable for the demolition of dilapidated bridges that are unable to withstand stress and undergo significant deformation due to severe structural damage.

[0020] 3. The construction vessel is positioned using anchor cables, and the height of the support structure on the vessel can be adjusted by filling and draining water in the hull, which can flexibly adapt to frequent changes in water level caused by tides.

[0021] 4. Construction vessels can transport the dismantled cantilever beams as a whole to a designated location for demolition, which can avoid safety hazards to navigation under the bridge and also avoid pollution to the river. Attached Figure Description

[0022] Figure 1 This is a construction flowchart of the present invention;

[0023] Figure 2 This is a plan view showing the arrangement of barges when the side span cantilever beam is being dismantled;

[0024] Figure 3 This is a side view of the barge arrangement when the side span cantilever beam is being dismantled;

[0025] Figure 4 This is a schematic diagram showing the state of the outer cantilever beam of the side span during demolition;

[0026] Figure 5 This is a schematic diagram showing the state of the mid-span closure section during demolition;

[0027] Figure 6 This is a schematic diagram showing the state of the mid-span closure section after its removal;

[0028] Figure 7 This is a schematic diagram of the barge arrangement during the demolition of the cantilever beams on both sides of the mid-span bridge pier;

[0029] Figure 8 This is a schematic diagram showing the state of the cantilever beams on both sides of a mid-span bridge pier after their removal.

[0030] Figure 9 This is a schematic diagram showing the state of the cantilever beams on both sides of another mid-span bridge pier after their removal. Detailed Implementation

[0031] Figure 1 This is a construction flowchart of the present invention. The following uses a three-span continuous beam bridge as an example to illustrate the specific construction of the present invention.

[0032] (1) Frames 2 are erected on the two barges 1 respectively. Fixed top supports are installed on the top of the frames according to the cross-sectional dimensions of the bottom of the continuous beam. The initial height of the frames 2 is higher than the bottom height of the beam.

[0033] (2) Figure 2 , Figure 3 As shown, ballast water is injected into the holds of the two barges 1 so that the height of the support 2 is lower than the bottom of the beam. Then, the two barges 1 are driven to the cantilever beam 3 on the outer side of the two spans of the bridge. Anchors are dropped at the four corners of the barges to fix their positions. Gradually, some water is discharged from the barges to raise them. As the barges are raised, the length of the anchor cable 4 is adjusted accordingly to keep the anchor cable 4 taut and keep the barges in a fixed position until the top support on the support 2 is pressed against the bottom of the cantilever beam 3.

[0034] (3) Figure 4 As shown, the closure section 5 between the two cantilever beams of the side span is cut off on the bridge using a wire saw. Then, the ballast water in the barge is drained, and the length of the anchor cable is adjusted simultaneously. The barge rises by relying on buoyancy, and the cantilever beam 3 on the outside of the side span is lifted off the side span pier 6. Then, the barge carries the cut cantilever beam 3 to the designated location for dismantling and breaking up the beam.

[0035] (4) Figure 5 , Figure 6 As shown, the closure section 5 of the two cantilever beams 3 between the two piers 7 in the middle span is cut off by wire saw, and steel pipe supports 8 are erected on the pier platform of each middle span to support the two ends of block 9 on the pier 7 in the middle span.

[0036] When cutting off the closure segment 5 of the two cantilever beams between the two mid-span piers 7, in order to avoid the closure segment falling directly into the water after being cut and endangering navigation under the bridge, the closure segment 5 can be suspended by a floating crane 10 before cutting. After the cutting is completed, the cut closure segment can be transported away by the floating crane.

[0037] (5) Figure 7 , Figure 8 As shown, after injecting ballast water into the holds of the two barges 1 again, so that the height of the supports on the barges is lower than the height of the bottom of the beam, the two barges respectively enter the area below the two sides of a mid-span pier 7. The barges use the same method as in step (2) to drain water and raise the barges so that the supports can support the cantilever beams 3 on both sides of the mid-span pier. The joint between the pier top 0# block 9 and the two cantilever beams 3 is cut simultaneously with a wire saw so that the two cantilever beams 3 fall onto the supports of the two barges respectively. The two barges 1 transport the cantilever beams 3 to the designated dismantling location.

[0038] (6) Figure 9 As shown, the cantilever beams on both sides of another mid-span pier are removed using the same method as in step (5);

[0039] (7) Finally, the floating crane 10 was used to remove the 0# block 9 on the two mid-span piers 7, completing the demolition of the entire bridge superstructure.

[0040] The above describes the demolition of a three-span continuous beam bridge. This invention is also applicable to the demolition of multi-span continuous beam bridges. During construction, the two barges first demolish the outer cantilever beams of the side spans, then demolish the cantilever beams on both sides of the piers of the secondary middle span, and so on towards the middle span. The demolition method is the same as described above and will not be repeated here.

[0041] In the specific construction of this invention, when the river water level changes due to tides, the two barges can choose to sail to the bridge at low tide. When the tide rises, the barges will naturally rise with the water level. During the rising process, the length of the anchor cable should be adjusted and the position of the barges should be fixed so that the barge support is always facing the bottom of the beam. First, check whether the support on the barge can naturally press against the bottom of the beam at high tide. If not, drain some of the ballast water to press the support against the bottom of the beam, and then cut the beam. During the beam cutting process, if the water level changes, the ballast water in the barge can be appropriately drained or increased and the anchor cable can be adjusted accordingly to ensure that the support is always supported on the bottom surface of the beam.

Claims

1. A method for the integral demolition of a half-span cantilever beam of a river-crossing concrete continuous beam bridge, characterized in that, The method comprises the following steps: (1) erecting a support on each of two barges, installing a fixed top support on the top of the support according to the size of the cross section of the bottom of the continuous beam, and setting the initial height of the support to be higher than the height of the beam bottom; (2) injecting ballast water into the cabin of each barge to lower the height of the support to be lower than the height of the beam bottom, then sailing the two barges to the lower side of the cantilever beam of the side span of the bridge, fixing the position of the barges by anchoring at the four corners of the barge, gradually discharging part of the ballast water in the barge to gradually raise the barge, and adjusting the length of the anchor cable to keep the anchor cable taut and the position of the barge fixed while the barge is being raised, until the top support of the support abuts against the beam bottom; (3) cutting the closure segment between the two cantilever beams of the side span on the bridge by using a rope saw, then continuously discharging the ballast water in the barge and synchronously adjusting the length of the anchor cable, raising the barge by buoyancy, and floating the cantilever beam of the side span to be separated from the side span pier, then carrying the cut cantilever beam by the barge to a designated position to disassemble and crush the beam body; (4) cutting the closure segment of the two cantilever beams between the two piers of the midspan by using a rope saw, and erecting a steel pipe support on each midspan pier to support the two ends of the 0# block on the pier; (5) injecting ballast water into the cabin of each barge to lower the height of the support to be lower than the height of the beam bottom, then sailing the two barges to the lower side of each midspan pier, raising the barge by discharging water in the same way as in step (2), and supporting the cantilever beams on the two sides of the midspan pier by the support; synchronously cutting the joint between the 0# block on the pier top and the two cantilever beams by using a rope saw, and making the two cantilever beams fall onto the supports of the two barges, respectively, and transporting the cantilever beams to a designated disassembly position by the two barges; (6) disassembling the cantilever beams on the two sides of the other midspan pier in the same way as in step (5); (7) disassembling the 0# blocks on the two midspan piers by using a floating crane, and completing the disassembly of the superstructure of the whole bridge.

2. The method according to claim 1, wherein the method is characterized by: In the case that the water level changes due to tides, the two barges are sailed to the lower side of the bridge at the low tide, and naturally raised with the water level when the tide rises. It is first determined whether the support on the barge can abut against the beam bottom naturally at the high tide, and if not, part of the ballast water is discharged to make the support abut against the beam bottom, and then the beam body is cut. During the cutting of the beam body, if the water level changes, the ballast water in the cabin is appropriately discharged or increased, and the anchor cable is adjusted accordingly, so that the support always supports the bottom surface of the beam body.

3. The method according to claim 1, wherein the method is characterized by: When the closure segment of the two cantilever beams between the two piers of the midspan is cut, the closure segment is first lifted by a floating crane to avoid falling down the bridge and affecting navigation, then the closure segment is cut, and finally the cut closure segment is transported away by the floating crane.

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