A method for integrated construction of dismantling and building of a new suspension bridge in situ by dismantling an old rigid frame bridge

Abstract

This invention relates to an integrated demolition and construction method for rebuilding a suspension bridge on the same site after demolishing an old rigid frame bridge. The method involves first demolishing the old bridge, then constructing the anchorages, main towers, and side spans of the new suspension bridge, installing the main cables and cable-mounted cranes, and using the cable-mounted cranes to dismantle the closure section of the middle span, the side spans, and the cantilever of the main beam of the middle span of the old bridge, and hoisting the steel box girder of the new suspension bridge. Simultaneously, crawler cranes are used to sequentially dismantle the closure section of the side spans, the cast-in-place section of the side spans, and the side piers of the old bridge. This invention allows for overlapping and simultaneous demolition and construction, which helps shorten the construction period. Utilizing the old bridge deck as a traction platform for the pilot cable of the new suspension bridge across the river does not affect navigation and saves costs. Using the cable-mounted cranes from the new suspension bridge construction for demolition ensures high construction efficiency and safety.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology and relates to an integrated demolition and construction method for rebuilding a suspension bridge on the same site after demolishing an old rigid frame bridge. Background Technology

[0002] Rigid frame bridges are a type of bridge that uses piers to support the main girder. Due to their low construction difficulty, ease of maintenance, and relatively low cost, they were commonly used for early cross-river bridges. However, after a certain number of years of use, some older rigid frame bridges across rivers have developed defects that cannot be repaired to meet safe operation requirements. Furthermore, some older bridges no longer meet current navigation needs due to their mid-span and clearance height. Therefore, they all require demolition and reconstruction. Suspension bridges, with their large mid-span, high load-bearing capacity, long service life, and ease of maintenance, are the preferred bridge type for bridge reconstruction.

[0003] Currently, the conventional construction sequence for the demolition and reconstruction of old bridges is: demolish the old bridge - clear the site - construct the new bridge, which has a long construction period. For old concrete rigid frame bridges, bridge cranes or floating cranes are often used for demolition. The bridge crane demolition method involves demolishing the bridge section by section in reverse order of construction. This method is not only slow, but also results in the old bridge having less strength than when it was built. After the closure section is removed, the T-shaped cantilever section is at risk of overturning and breaking. The floating crane demolition method requires applying a stable upward lifting force to the T-shaped cantilever section in advance to prevent the bridge segment from falling uncontrollably during the instant of segment cutting. However, in fast-flowing rivers, the stability control of the floating crane is difficult, and the rental cost of the floating crane is high. In addition, the floating crane needs to occupy the waterway for a long time, which has a significant impact on normal navigation. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing an integrated demolition and construction method for rebuilding a suspension bridge on the same site after demolishing an old rigid frame bridge, so as to shorten the construction period, reduce the time occupied by the waterway, ensure construction safety, and reduce construction costs.

[0005] The technical solution of the present invention is as follows:

[0006] A method for integrated demolition and reconstruction of an old rigid frame bridge and a new suspension bridge in situ, wherein the old rigid frame bridge is designed with side spans and a middle span for the river crossing section, and approach bridges are designed on both banks; the new suspension bridge is designed with a middle span for the river crossing section, and side spans are designed on both banks; the method is characterized by including the following steps.

[0007] (1) Demolish the approach bridge of the old bridge; construct construction trestle bridges from both banks into the river, with each trestle bridge extending along the bridge direction to the outside of the cast-in-place section of the old bridge side span; erect temporary supports under the cast-in-place section of the old bridge side span, which are used to provide temporary support for the cast-in-place section of the old bridge side span when the closure section of the old bridge side span is demolished.

[0008] (2) Construct the anchorage, main tower and side span of the new suspension bridge at the location of the old bridge approach bridge, and install the main cable of the suspension bridge; install two cable-mounted cranes on the two main cables of the new suspension bridge respectively;

[0009] (3) The middle span closure section of the old bridge was dismantled using a cable-mounted crane and lowered onto a transport ship for removal; at the same time, a crawler crane was driven from the shore to the trestle bridge and the side span closure section and the side span cast-in-place section of the old bridge were dismantled in sequence using the crawler crane.

[0010] (4) The side spans and middle spans of the old bridge are symmetrically dismantled using cable-mounted cranes, and the side piers of the old bridge are dismantled using crawler cranes. After the side piers of the old bridge are dismantled, a sliding support is erected based on the temporary support. The sliding support serves as a transfer platform for steel box girder segments of the suspension bridge near the main tower area.

[0011] (5) Install suspension bridge suspenders on the main cable of the newly built suspension bridge;

[0012] The girder transport vessel transports steel box girder segments of the suspension bridge near the main tower area to the bridge. The cable crane lifts the steel box girder from the vessel and moves it towards the main tower. When it is a certain distance from the main tower, due to the large inclination angle of the main cable near the tower area, the cable crane cannot lift the steel box girder to travel on the main cable in this area. The swing method is used to swing the steel box girder onto the sliding support.

[0013] The steel box girder is slid to below the installation position on the sliding support. The cable-mounted crane is then moved unloaded to above the installation position of the steel box girder, and the steel box girder on the sliding support is lifted to the installation height and connected to the slings. The steel box girders in the two bridge tower areas are installed symmetrically.

[0014] While installing the steel box girder in the bridge tower area, a floating crane was used to dismantle the No. 0 block, piers and underwater abutment of the old bridge in the middle span;

[0015] (6) After the steel box girder segments in the bridge tower area are installed, the sliding support is removed, and then the steel box girder is symmetrically installed from the middle of the span to both banks using a cable-mounted crane until the steel box girder in the middle span of the suspension bridge is closed, thus completing the demolition of the old rigid frame bridge and the construction of the new suspension bridge.

[0016] Furthermore, in step (2) of the above-mentioned integrated construction method for demolishing and rebuilding an old rigid frame bridge and constructing a new suspension bridge on the same site, during the installation of the main cable of the suspension bridge, the side span and middle span of the old bridge are used as the pilot cable crossing platform, and a trolley is used on the old bridge to pull the pilot cable from one bank to the other bank.

[0017] Furthermore, in step (3) of the above-mentioned integrated construction method for demolishing and rebuilding an old rigid frame bridge and constructing a new suspension bridge on the same site, before demolishing the closure section of the middle span and side span of the old bridge, a temporary cable is first connected between the main beam of the old bridge and the main cable of the suspension bridge to prevent the cantilever section of the main beam of the old bridge from becoming too long and overturning or breaking after the closure section of the old bridge is removed.

[0018] The present invention has the following advantages:

[0019] 1. The bridge demolition and construction processes are carried out simultaneously, with some procedures being carried out concurrently. This breaks the conventional construction mode of demolishing first and then building, which helps to shorten the construction period and reduce the time affected by navigation under the bridge.

[0020] 2. Using the old bridge deck as a traction platform for the pilot cable of the new suspension bridge to cross the river is a more efficient and cost-effective method than the conventional suspension bridge construction method, which requires the pilot cable to be pulled across the river by boats or drones. This method does not affect navigation and saves costs.

[0021] 3. Using the cable-mounted cranes used in the construction of new suspension bridges to demolish old bridges further reduces costs and ensures high safety during bridge demolition;

[0022] 4. Using the dismantled supports of the cast-in-place section of the old bridge as a foundation, a sliding support was erected as a platform for the swinging and sliding of the steel box girder segments in the tower area of ​​the new suspension bridge, which saved the amount of steel used in the temporary structure of the bridge construction.

[0023] 5. This invention is not limited to the integrated demolition and reconstruction of old rigid frame bridges, but is also applicable to the demolition and reconstruction of old continuous beam bridges, steel truss bridges, simply supported beam bridges and upper-bearing arch bridges. Attached Figure Description

[0024] Figure 1 This is a construction flowchart of the present invention;

[0025] Figure 2 This is a side view structural diagram of an old rigid frame bridge slated for demolition.

[0026] Figure 3 This is a schematic diagram showing the progress of dismantling the old bridge approach bridge and erecting a construction trestle and temporary supports.

[0027] Figure 4 This is a schematic diagram showing the completed state of the side spans, main towers, main cables, and cable-mounted cranes of the newly constructed suspension bridge.

[0028] Figure 5 This is a schematic diagram showing the status of the old bridge's mid-span closure section being demolished by a cable-mounted crane, and the side-span closure section and cast-in-place section being demolished by a crawler crane.

[0029] Figure 6 This is a schematic diagram showing the process of using a cable-mounted crane to dismantle the cantilevered side spans and middle spans of the old bridge, while a crawler crane dismantles the side span piers and erects sliding supports.

[0030] Figure 7 This is a schematic diagram showing the state of the cable-mounted crane lifting and installing the steel box girder near the main tower area of ​​the suspension bridge;

[0031] Figure 8 A schematic diagram showing the lifting operation of a mid-span steel box girder segment by a cable-driven crane.

[0032] Figure 9 This is a schematic diagram showing the state of the newly built suspension bridge during its closure. Detailed Implementation

[0033] Figure 1 This is a flowchart illustrating the construction process of this invention. The construction method of this invention will be specifically described below through a specific embodiment.

[0034] Figure 2 The diagram shows a side view of an old rigid-frame bridge spanning a river. Its river-crossing section includes a central span 101 and side spans 102, with approach bridges 103 on each bank. The old rigid-frame bridge needs to be demolished, and a new suspension bridge needs to be built on the same site. The new suspension bridge will have a central span across the river, with side spans on each bank. If the conventional method of demolishing the old bridge first and then building the new one is used, not only will the construction period be long and the navigation under the bridge be affected for a considerable time, but the safety of the demolition construction will also be difficult to guarantee. Therefore, the integrated demolition and construction method of this invention is proposed, specifically including the following steps:

[0035] (1) As Figure 3 As shown, the approach bridges of the old bridge are first demolished, and construction trestle bridges 1 are erected from both banks into the river. The trestle bridges on each bank are erected along the bridge direction to the outside of the cast-in-place section of the side span 102 of the old bridge. Temporary supports 2 are erected below the cast-in-place section of the side span of the old bridge. The temporary supports 2 are used to temporarily support the cast-in-place section of the side span of the old bridge when the closure section of the side span of the old bridge is demolished, so as to prevent the cantilever of the cast-in-place section of the side span of the old bridge from becoming unstable and overturning.

[0036] (2) Figure 4 As shown, after the old bridge approach bridge is demolished, the anchorage 3, main tower 4 and side span 5 of the new suspension bridge are constructed at the location of the old bridge approach bridge, and the main cable 6 of the suspension bridge is installed; two cable-mounted cranes 7 are installed on the two main cables 6 of the new suspension bridge respectively.

[0037] During the installation of the main cable of a suspension bridge, due to its heavy weight, a pilot cable is typically erected between the two banks. This pilot cable is used to pull and erect the catenary and main cable. On the catenary, the main cable is shaped, and clamps and suspenders are installed. When erecting the pilot cable, one end is connected to a winch on one bank, and the other end is passed over the tower and sent to the other bank, where it passes over the tower and connects to a winch on that bank. This process is commonly referred to as the pilot cable crossing the river.

[0038] Crossing the pilot cable across the river is a crucial step in the main cable erection process. Currently, pilot cable crossings are commonly achieved using tugboats, or by using drones, helicopters, or rocket launchers. Tugboat towing requires temporary closure of the waterway, which can disrupt navigation, while other methods are more costly.

[0039] In the process of installing the main cable of the suspension bridge, the bridge deck of the old bridge side span 102 and the middle span 101 is not demolished first. The old bridge deck can be used as a platform for the pilot cable to cross the river. A trolley is used to pull the pilot cable across the river on the old bridge, which can avoid affecting navigation and save costs.

[0040] (3) Figure 5 As shown, after the main cable 6 and cable-mounted crane 7 are installed, the cable-mounted crane 7 is used to dismantle the closure section of the old bridge's middle span and lower it onto the transport ship for transport. At the same time, the crawler crane 8 travels from the shore to the trestle bridge and is used to dismantle the closure section of the old bridge's side span and the cast-in-place section of the side span in sequence.

[0041] After the closure sections of the old bridge's middle and side spans are demolished, cantilevered sections will form at both ends of the main beam. Since the load-bearing capacity of the old bridge's concrete structure is lower than when the bridge was built, these cantilevered sections are at risk of fracture or overturning. To avoid these problems, this invention allows for the connection of temporary cables 9 between the main beams of the old bridge's side spans 102 and middle spans 101 and the main cable 6 of the suspension bridge before the closure sections are demolished. This prevents the cantilevered sections of the old bridge's main beam from becoming too long after the closure sections are removed, which could lead to overturning or fracture.

[0042] (4) Figure 6 As shown, after the main side span closure section of the old bridge was demolished, the cantilever of the side span 102 and the middle span 101 of the old bridge was symmetrically demolished using cable-mounted crane 7. During the demolition, the concrete beam segments were poured in reverse order during the construction of the old bridge.

[0043] The lifting capacity of the cable-stayed crane is designed to meet the weight of the steel box girder segments of the suspension bridge. The weight of a steel box girder segment is generally 2-3 times that of a concrete beam segment. Therefore, when dismantling the cantilever of the old bridge, the cable-stayed crane can dismantle 2-3 concrete segments at a time, which is more efficient than the existing bridge deck cranes that dismantle segments one by one.

[0044] While dismantling the cantilever of the main girder of the old bridge side span, the old bridge side piers are dismantled using crawler crane 8. After the old bridge side piers are dismantled, a sliding support 10 is erected based on the temporary support 2, and a sliding track or sliding plate is installed on the sliding support. The sliding support serves as a transfer platform for steel box girder segments of the suspension bridge near the main tower area during the subsequent installation of the suspension bridge steel box girder.

[0045] (5) Figure 7 As shown, suspension bridge suspenders 11 are installed on the main cable of the newly built suspension bridge;

[0046] The girder transport vessel transports the steel box girder segment 12 near the main tower area of ​​the suspension bridge to the area under the bridge. The cable-mounted crane 7 lifts the steel box girder from the vessel and moves it towards the main tower. When it is a certain distance from the main tower, due to the large inclination angle of the main cable near the tower area, the cable crane cannot lift the steel box girder and move it on the main cable in this area. Therefore, the swing method is used to first swing the steel box girder segment 12 onto the sliding support 10. The steel box girder is then slid onto the sliding support to below the installation position. The cable-mounted crane 7 runs unloaded above the installation position of the steel box girder, lifts the steel box girder on the sliding support to the installation height, and connects it with the sling. In specific construction, the steel box girders in the two bridge tower areas should be installed symmetrically.

[0047] The swing-sliding method is a common method for installing steel box girders in suspension bridges. Typically, during swing-sliding construction, a sliding support is installed below the steel box girder in the tower area. A cable-mounted crane lifts the steel box girder to a certain distance from the main tower, then connects it using cables or extended slings 13. The cable-mounted crane then releases the steel box girder, which is then lifted and pulled onto the sliding support by the extended slings 13. After sliding the steel box girder below the installation position on the sliding support, the cable-mounted crane moves unloaded above the steel box girder to lift and install it. This invention utilizes temporary supports erected from the dismantled cast-in-place sections of the old bridge's side spans, improving the reuse rate of temporary supports and saving costs.

[0048] While installing the steel box girder in the bridge tower area, the floating crane 14 was used to dismantle the No. 0 block, piers and underwater abutment of the old bridge's middle span.

[0049] (6) Figure 8 As shown, after the steel box girder segments in the bridge tower area are installed, the sliding supports are removed, and then the cable-mounted crane 7 is used to symmetrically install the steel box girder segments 12 from the mid-span to both banks. At the same time, the floating crane 14 continues to remove the remaining 0# block, piers and underwater abutments of the old bridge.

[0050] like Figure 9 As shown, cable-mounted crane 7 hoisted the steel box girder closure section 12 of the suspension bridge, completing the demolition of the old rigid frame bridge and the construction of the new suspension bridge.

Claims

1. A method for integrated demolition and reconstruction of an old rigid frame bridge and a new suspension bridge in situ, wherein the old rigid frame bridge has side spans and a middle span for its river-crossing section, and approach bridges are designed on both banks; the new suspension bridge has a middle span for its river-crossing section, and side spans on both banks, characterized in that… Includes the following steps: (1) Demolish the approach bridge of the old bridge; construct construction trestle bridges from both banks into the river, with each trestle bridge extending along the bridge direction to the outside of the cast-in-place section of the old bridge side span; erect temporary supports under the cast-in-place section of the old bridge side span, which are used to provide temporary support for the cast-in-place section of the old bridge side span when the closure section of the old bridge side span is demolished. (2) Construct the anchorage, main tower and side span of the new suspension bridge at the location of the old bridge approach bridge, and install the main cable of the suspension bridge; install two cable-mounted cranes on the two main cables of the new suspension bridge respectively; (3) The middle span closure section of the old bridge was dismantled using a cable-mounted crane and lowered onto a transport ship for removal; at the same time, a crawler crane traveled from the shore to the trestle bridge and the side span closure section and the side span cast-in-place section of the old bridge were dismantled in sequence using the crawler crane. (4) The side spans and middle spans of the old bridge are symmetrically dismantled using cable-mounted cranes, and the side piers of the old bridge are dismantled using crawler cranes. After the side piers of the old bridge are dismantled, a sliding support is erected based on the temporary support. The sliding support serves as a transfer platform for steel box girder segments of the suspension bridge near the main tower area. (5) Install suspension bridge suspenders on the main cable of the newly built suspension bridge; The girder transport vessel transports steel box girder segments of the suspension bridge near the main tower area to the bridge. The cable crane lifts the steel box girder from the vessel and moves it towards the main tower. When it is a certain distance from the main tower, due to the large inclination angle of the main cable near the tower area, the cable crane cannot lift the steel box girder to travel on the main cable in this area. The swing method is used to swing the steel box girder onto the sliding support. The steel box girder is slid to below the installation position on the sliding support. The cable-mounted crane is then moved unloaded to above the installation position of the steel box girder, and the steel box girder on the sliding support is lifted to the installation height and connected to the slings. The steel box girders in the two bridge tower areas are installed symmetrically. While installing the steel box girder in the bridge tower area, a floating crane was used to dismantle the No. 0 block, piers and underwater abutment of the old bridge in the middle span; (6) After the steel box girder segments in the bridge tower area are installed, the sliding support is removed, and then the steel box girder is symmetrically installed from the middle of the span to both banks using a cable-mounted crane until the steel box girder in the middle span of the suspension bridge is closed, thus completing the demolition of the old rigid frame bridge and the construction of the new suspension bridge.

2. The integrated demolition and reconstruction method for old rigid frame bridges and new suspension bridges in situ, as described in claim 1, is characterized in that: In step (2), during the installation of the main cable of the suspension bridge, the side span and middle span of the old bridge are used as the pilot cable crossing platform. A trolley is used on the old bridge to pull the pilot cable from one bank to the other.

3. The integrated demolition and reconstruction method for old rigid frame bridges and new suspension bridges in situ, as described in claim 1, is characterized in that: In step (3), before dismantling the closure sections of the middle and side spans of the old bridge, temporary cables are first connected between the main beam of the old bridge and the main cable of the suspension bridge to prevent the cantilever section of the main beam of the old bridge from becoming too long and overturning or breaking after the closure section of the old bridge is removed.

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