Safe dismantling method for old rigid frame bridge

Abstract

The invention relates to a safe dismantling method for an old rigid frame bridge, which comprises the following steps of: respectively constructing a trestle to two main piers of a main span from two banks along the bridge direction, respectively installing buckling towers above the two main piers on the bridge, installing a pair of temporary inhaul cables between the buckling towers and a main span beam at intervals of a plurality of main beam sections, arranging a bridge floor crane on the bridge, and dismantling a midspan closure section of the main beam by utilizing the bridge floor crane. The crawler crane travels to the trestle, and the side span closure section is dismantled through the crawler crane, so that the main beam forms two T-shaped structures; the side span sides of the two T structures are dismantled section by section through a crawler crane, the midspan sides of the two T structures are dismantled section by section through a bridge deck crane, and when the sections with the inhaul cables are dismantled, the inhaul cables are removed firstly, and then the sections are dismantled; and finally, the main piers, the side span beams and the side span junction piers are sequentially dismantled through crawler cranes, and dismantling of the old rigid frame bridge is completed. The principle of a cable-stayed bridge is adopted, the temporary inhaul cables are adopted to provide upward pulling force for the T-shaped cantilever of the rigid frame bridge, the T-shaped cantilever can be prevented from collapsing, safety is good, the construction speed is high, and navigation is not affected.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering and relates to a method for safely dismantling an old rigid frame bridge. Background Art

[0002] A rigid frame bridge is a continuous beam bridge made of prestressed reinforced concrete. After years of operation, a rigid frame bridge will suffer from various structural damages, such as cracks in the main beam concrete, corrosion of the steel bars, and loss of prestress in the body, which will lead to a decrease in the overall bearing capacity and rigidity of the bridge and deflection in the mid-span. If repairs and reinforcements still cannot meet traffic safety requirements, the bridge needs to be dismantled and rebuilt.

[0003] Conventional methods of bridge demolition include blasting and mechanical demolition. The blasting method causes great environmental pollution and is no longer in line with the contemporary green and environmentally friendly construction concept. Mechanical demolition is the current mainstream demolition method, which uses rope saws or crushers to cut or crush bridges in situ.

[0004] At present, the mainstream methods of bridge demolition are cantilever segment demolition method and full-frame scaffolding method. The cantilever segment demolition method is the reverse construction method of bridge construction. When building a rigid frame bridge, the cantilever segment is usually cast with a hanging basket, and the demolition process uses cantilever segment cutting and demolition. However, due to structural damage, the bending resistance and bearing capacity of the cantilever of the old rigid frame bridge are not as good as when the bridge was built. After the joint section is dismantled to form a T-structure, the cantilever is too long and prone to collapse accidents, which has poor safety. The full-frame scaffolding method is to set up a full-frame scaffold under the bridge for support, and cut or crush the bridge in situ. However, on the one hand, the construction period of setting up a full-frame scaffold is long, a large amount of steel is consumed, and the cost is high. On the other hand, when there is a navigable river under the bridge, the waterway needs to be closed, which affects navigation for a long time. Summary of the invention

[0005] The purpose of the present invention is to provide a method for dismantling an old rigid frame bridge which is safe and quick in construction in view of the above problems.

[0006] The technical solution of the present invention is as follows:

[0007] A method for safely dismantling an old rigid frame bridge, characterized in that it comprises the following steps:

[0008] (1) From both banks, construct the trestle along the bridge to the two main piers of the main span;

[0009] (2) Ground supports are set up on both sides of the cross bridge at the junction of the side span pier to support the side span beam; steel pipe piles are set up on both sides of the cross bridge at each main pier to support the ends of block 0 of the main span beam;

[0010] (3) Install the bridge crane track and bridge crane on the mid-span beam surface;

[0011] (4) The crawler crane travels to the trestle bridge and uses the crawler crane to install the pylons above the two main piers on the bridge. A pair of temporary cables are installed between the pylons and the main span beam every several main beam segments. The temporary cables on both sides of each pylon are arranged symmetrically and tensioned.

[0012] (5) Use a bridge crane to remove the mid-span joint section, lower it to a transport ship and transport it away; use a crawler crane to remove the side span joint section, and transport it away by a transport vehicle, so that the main span beam forms two T structures;

[0013] (6) The two T-structures were dismantled symmetrically. The side spans of the two T-structures were dismantled segment by segment using crawler cranes, and the dismantled segments were transported away by transport vehicles. The mid-span side was dismantled segment by segment using a bridge crane, and the dismantled segments were lowered to a ship and transported away. When the segment with the cable was dismantled, the cable was first removed, and then the segment was dismantled. When the T-structure was dismantled to the 0# block of the main span beam, the bridge crane and the pylon were first removed by a crawler crane, and then the 0# block was cut and dismantled.

[0014] (8) Cut the main pier in layers, and lift the cut blocks by crawler crane to the transport vehicle for transportation;

[0015] (9) Use a crawler crane to dismantle the side span beams in sections, and finally dismantle the side span junction slabs to complete the dismantling of the old rigid frame bridge.

[0016] The present invention adopts the principle of cable-stayed bridge, firstly uses temporary cables to provide upward pulling force to the T-frame cantilever of the rigid frame bridge to prevent the cantilever from collapsing, and then uses a bridge deck crane to dismantle it in sections. Compared with the direct cantilever segment dismantling method, the present invention has good safety, and compared with the full-bridge support method, the present invention does not affect navigation, and has a fast construction speed and uses less steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the status after the installation of the trestle, side span brackets, main beam block 0 supporting steel pipe piles, bridge deck crane, main span beam upper buckle tower and temporary cables;

[0018] Figure 2 This is a schematic diagram of the transverse bridge structure of the main beam block No. 0 supporting the steel pipe piles;

[0019] Figure 3 It is a schematic diagram of the state of dismantling the mid-span closure section and the side span closure section;

[0020] Figure 4 This is a schematic diagram of the state of dismantling the main span T-structure in sections;

[0021] Figure 5 This is a schematic diagram of the crawler crane dismantling block 0 of the main span beam;

[0022] Figure 6 This is a schematic diagram of the status of dismantling the main pier and side span beams. DETAILED DESCRIPTION

[0023] The specific construction method of the present invention is as follows:

[0024] (1) Figure 1 As shown, the trestle 1 is constructed along the bridge from both banks to the two main piers 2 of the main span;

[0025] (2) Ground supports 4 are respectively set up on both sides of the cross bridge of the side span junction pier 3 to support the side span beam 5; steel pipe piles 6 are respectively set on both sides of the cross bridge of each main pier 2 to support the two ends of block 0 of the main span beam 7.

[0026] When steel pipe piles 6 are arranged on both sides of the main pier, when the height of the cap is lower than the water level of the river, it is necessary to first construct a water retaining cofferdam 8 around the main pier, drain the water in the cofferdam, and then construct the steel pipe piles in the cofferdam.

[0027] The purpose of setting steel pipe piles at the bottom of the main beam block 0 is to prevent the two ends of the main beam T structure from being unbalanced and causing overturning during the bridge demolition process. Figure 2 As shown, in the specific implementation, the steel pipe piles 6 on both sides of the main pier are arranged in a single row of 4 in the transverse direction of the bridge, and the 4 steel pipe piles are connected by flat joints and diagonal braces. The lower end of each steel pipe pile is anchored to the main pier cap by drilling or planting reinforcement, and the upper end is anchored to the bottom surface of block No. 0.

[0028] In order to improve the stability of the steel pipe piles, each steel pipe pile 6 can be connected to the main pier 2 through a wall attachment rod.

[0029] Sand can be poured into each steel pipe pile to increase the vertical bearing capacity of the steel pipe.

[0030] (3) Install the bridge crane track and the bridge crane 9 on the mid-span beam surface; the bridge crane can be installed on the bridge using a crawler crane.

[0031] (4) Figure 1 As shown, the crawler crane 10 travels onto the pier 1, and the crawler crane 9 is used to install the buckling towers 11 above the two main piers 2 of the main span beam, and a pair of temporary cables 12 are installed between the buckling towers 11 and the main span beam 7 every several main beam segments. The temporary cables on both sides of each buckling tower are symmetrically arranged, and the cables are tensioned.

[0032] The buckle tower 11 can be made of a steel pipe bracket and installed in sections by a crawler crane. The bottom section of the buckle tower is fixed to the bridge deck by drilling or planting reinforcement.

[0033] The temporary cable is made of steel strands, such as Figure 2 As shown, one end of the temporary cable 12 is anchored on the buckle tower, and the other end passes through the wing plate of the main span beam 7 and is anchored at the junction of the wing plate and the web plate outside the web plate of the main span beam.

[0034] (5) Figure 3As shown, the bridge crane 9 is used to remove the mid-span joint section, which is lowered to the transport ship 13 for transportation, and the crawler crane 10 is used to remove the side span joint section, which is transported by the transport vehicle 14, so that the main span beam 7 forms two T structures. Temporary cables 12 are connected between the cantilevers at both ends of the T structure and the buckle tower 11 to prevent the cantilever of the T structure from collapsing. The transport vehicle 14 passes on the trestle 1.

[0035] (6) Figure 4 As shown, the two main span beam T-structures are dismantled symmetrically. The side spans of the two T-structures are dismantled segment by segment using crawler cranes 10, and the dismantled segments are transported away by transport vehicles. The mid-span side is dismantled segment by segment using a bridge crane, and the dismantled segments are lowered to a ship and transported away. When dismantling a segment with a cable, first release the cable and then dismantle the segment; Figure 5 As shown, when the T-structure is dismantled to the 0# block of the main span beam, the crawler crane is first used to dismantle the bridge deck crane and the pylon, and then the 0# block is cut and dismantled.

[0036] (8) Figure 6 As shown, the main pier 2 is cut in layers, and the cut blocks are lifted by a crawler crane 10 and transported to a transport vehicle;

[0037] (9) Use a crawler crane to dismantle the side span beam 5 in 10 sections, and finally dismantle the side span junction slab to complete the dismantling of the old rigid frame bridge.

Claims

1. A method for safely dismantling an old rigid frame bridge, characterized in that: The following steps are involved: (1) From both banks, construct the trestle along the bridge to the two main piers of the main span; (2) Ground supports are set up on both sides of the cross bridge at the junction of the side span pier to support the side span beam; steel pipe piles are set up on both sides of the cross bridge at each main pier to support the ends of block 0 of the main span beam; (3) Install the bridge crane track and bridge crane on the mid-span beam surface; (4) The crawler crane travels to the trestle bridge and uses the crawler crane to install the pylons above the two main piers on the bridge. A pair of temporary cables are installed between the pylons and the main span beam every several main beam segments. The temporary cables on both sides of each pylon are arranged symmetrically and tensioned. (5) Use a bridge crane to remove the mid-span joint section, lower it to a transport ship and transport it away; use a crawler crane to remove the side span joint section, and transport it away by a transport vehicle, so that the main span beam forms two T structures; (6) The two T-structures were dismantled symmetrically. The side spans of the two T-structures were dismantled segment by segment using crawler cranes, and the dismantled segments were transported away by transport vehicles. The mid-span side was dismantled segment by segment using a bridge crane, and the dismantled segments were lowered to a ship and transported away. When the segment with the cable was dismantled, the cable was first removed, and then the segment was dismantled. When the T-structure was dismantled to the 0# block of the main span beam, the bridge crane and the pylon were first removed by a crawler crane, and then the 0# block was cut and dismantled. (7) Cut the main pier in layers, and lift the cut blocks by crawler crane to the transport vehicle for transportation; (8) Use a crawler crane to dismantle the side span beams in sections, and finally dismantle the side span junction slabs to complete the dismantling of the old rigid frame bridge.

2. The method for safely dismantling an old rigid frame bridge according to claim 1 is characterized in that: When setting steel pipe piles on both sides of the main pier, when the height of the pedestal is lower than the water level of the river, first construct a water retaining cofferdam around the main pier, and then construct the steel pipe piles inside the cofferdam.

3. The method for safely dismantling an old rigid frame bridge according to claim 1 is characterized in that: Four steel pipe piles are arranged in a single row in the transverse direction of the bridge on both sides of the main pier. The four steel pipe piles are connected by parallel joints and diagonal braces. The lower end of each steel pipe pile is anchored to the pedestal by drilling or planting reinforcement, and the upper end is anchored to the bottom surface of block No.

0.

4. The method for safely dismantling an old rigid frame bridge according to claim 1 is characterized in that: Each steel pipe pile is connected to the main pier through a wall-attached rod.

5. The method for safely dismantling an old rigid frame bridge according to claim 1 is characterized in that: Sand is poured into each steel pipe pile to increase the vertical bearing capacity of the steel pipe.

6. The method for safely dismantling an old rigid frame bridge according to claim 1 is characterized in that: The buckle tower adopts a steel pipe support and is installed in sections by a crawler crane. The bottom section of the buckle tower is fixed to the bridge deck by drilling or planting reinforcement.

7. The method for safely dismantling an old rigid frame bridge according to claim 1 is characterized in that: The temporary cable is made of steel strand, one end of which is anchored on the buckle tower, and the other end passes through the main beam wing plate and is anchored at the junction of the wing plate and the web plate outside the main beam web plate.

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