A method for dismantling and reusing hollow slab bridges

Abstract

This invention relates to a method for dismantling and reusing hollow slab bridges, belonging to the field of bridge construction technology. Current methods for dismantling hollow slabs require significant manual labor. Due to the narrow hinge spaces of the original bridge and the reinforcing steel bars at both ends and internally, conventional dismantling easily damages the hollow slabs, resulting in damage to the removed slabs. This invention eliminates the need to break the hinges when dismantling the hollow slab bridge. Instead, it cuts the top and bottom slabs of the central hollow slab, retaining the hinges. The cut blocks in the middle are I-shaped, forming I-beams. After reinforcing the cut blocks, they are reused, installed, and subjected to transverse prestressing. Ultra-high performance concrete is then laid on the bridge deck. This solution dismantles the hollow slab bridge into I-beams, allowing the new bridge to be either an I-beam bridge or still a hollow slab bridge. The dismantling work is minimal, the tools are simple, and the cut blocks can be reused, accelerating the widening and reconstruction of existing bridges, avoiding resource waste, and reducing investment.

Description

Technical Field

[0001] This invention relates to a method for dismantling bridges, and more particularly to a method for dismantling and reusing hollow slab bridges, belonging to the field of bridge construction technology. Background Technology

[0002] Precast hollow slab bridges are a preferred bridge type for small and medium-span bridges due to their simple structure, clear stress distribution, and convenient construction. This type of bridge is the most commonly used and longest-lasting bridge type on highways and trunk roads. With increasing traffic volume, many existing roads require reconstruction and expansion, necessitating the demolition of hollow slab bridges. For hollow slab bridges in relatively good technical condition, it is desirable that the components, after demolition and repair, be reused in existing or other projects to achieve resource conservation.

[0003] Current hollow slab bridge demolition work primarily involves chiseling away the concrete within the hinge joints on the bridge deck. Because the hinge joint space is narrow and contains reinforcing steel bars, chiseling is difficult and slow, requiring a large amount of manual labor. Furthermore, the chiseling process easily damages the edges and webs of the hollow slabs, rendering the removed slabs unusable. Therefore, there is an urgent need for an efficient demolition technology for hollow slab bridges and a solution for reusing the demolished components. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention develops a method for dismantling and reusing hollow slab bridges, with the aim of achieving efficient dismantling of hollow slab bridges and reusing easily dismantled components.

[0005] The technical solution proposed in this invention is as follows: during the dismantling of the hollow slab bridge, the top and bottom plates of the middle beam are cut longitudinally, while retaining the hinge joint; during the reuse process, the original cut blocks or the repaired and reinforced cut blocks are assembled laterally, and transverse prestress is applied to increase the overall integrity of the new bridge.

[0006] Preferably, the construction mainly includes the following steps:

[0007] Step 1: Remove the surface layer of the bridge and dismantle the guardrails;

[0008] Step 2: Remove the concrete pavement layer above the cavity of the central beam to form a groove on the cross section of the central beam, with the groove running longitudinally along the hollow slab; alternately approach the transverse side of the groove and cut off the transverse reinforcing bars of the pavement layer inside the groove; bend up the longer section of the cut transverse reinforcing bars and cut the top plate of the central beam below the bottom surface of the groove; cut the bottom plate of the central beam from under the bridge; lift off each cut block;

[0009] Step 3: Repair the cutting block. Specific tasks include:

[0010] Step 3-1: Check whether there are gaps or debonding between the bottom surface of the pavement layer and the top slab of the hollow core slab, and remove the pavement layer concrete in the gaps or debonding areas.

[0011] Step 3-2: Check whether there is any void or debonding between the concrete and the hollow slab in the hinge joint; inject reinforcing grout into the void or debonding area in the hinge joint to repair the connection between the concrete and the hollow slab in the hinge joint and enhance the connection strength of the hinge joint.

[0012] Step 3-3: Clean the exposed bottom and sides of the cutting block and apply protective coating;

[0013] Step 4: Drill a top transverse prestressing through hole near the bottom of the hollow slab on the cutting block, and drill a bottom transverse prestressing through hole near the bottom of the hollow slab on the cutting block.

[0014] Step 5: Construct new pier cap beams and their bearing pads, or modify existing pier cap beams and their bearing pads.

[0015] Step 6: Install the reinforced cutting blocks and apply structural adhesive to the splicing surfaces;

[0016] Step 7: Insert transverse prestressing tendons; tension the transverse prestressing;

[0017] Step 8: Pour the pavement layer to repair the concrete; install or pour the guardrails, and construct the bridge deck surface layer.

[0018] Preferably, step 3-2B is added before step 3-2, and step 3-2D is added after step 3-2.

[0019] Step 3-2B: Install corresponding crossbeams on the upper part of both longitudinal ends of the cutting block, and use the crossbeams to tension the longitudinal temporary prestressing tendons, so that the top plate of the hollow slab is compressed; flip the cutting block up and down;

[0020] Step 3-2D: Install the outward connecting steel plate between the adjacent hollow slab "horseshoes", and pour ultra-high performance concrete on the upper surface of the flipped cutting block; after the ultra-high performance concrete reaches the specified strength, flip the cutting block back to its normal position.

[0021] Preferably, step 3-2C is added before step 3-2D.

[0022] Step 3-2C: Fix both ends of the flipped cutting block, and use a jack to lift it upwards from below the middle of the span, so that the cutting block produces the expected upward arch.

[0023] Preferably, step 3-2E is added after step 3-2.

[0024] Step 3-2E: Install diagonal steel strips on the outer surface of the web at both ends of the cutting block using chemical anchors. Structural adhesive is applied between the diagonal steel strips and the cutting block.

[0025] Preferably, step 3-2F is added after step 3-2.

[0026] Step 3-2F: Install the bottom reinforcing steel component longitudinally on the lower surface of the bottom plate of the cutting block, and connect the bottom reinforcing steel component to the cutting block with bolts or chemical anchors. Structural adhesive is applied between the bottom reinforcing steel component and the cutting block.

[0027] Preferably, step 6 is further refined as follows:

[0028] Step 6: Install the reinforced cutting blocks. I-shaped connectors are installed between the top and bottom plates of adjacent cutting blocks. Structural adhesive is applied between the I-shaped connectors and the cutting blocks. Structural adhesive is also applied to the contact surfaces of the connected diaphragm plates.

[0029] Preferably, step 8 is further refined as follows:

[0030] Step 8: Pour ultra-high performance concrete on the bridge deck to cover the original pavement layer, with the upper layer being 2 to 10 centimeters thicker than the original pavement layer; install or pour guardrails and construct the bridge deck surface layer.

[0031] Preferably, transverse diaphragm plates are cast at both ends of the cutting block and at any position between the two ends; the transverse diaphragm plates are located in the exposed cavity of the middle beam on the cross section of the cutting block; the transverse diaphragm plates of the middle cutting block are divided into left and right pieces, one of which has a protrusion and the other has a corresponding groove; the transverse diaphragm plates have top transverse prestressing through holes and bottom transverse prestressing through holes; the transverse diaphragm plates contain reinforcing bars that are inserted into the cutting block through drilled holes.

[0032] Preferably, step 1A is added after step 1: two transverse diaphragm plates are cast into the cavities at both ends of the middle beam. Before casting, the two are separated by a template. One transverse diaphragm plate has a protrusion and the other has a corresponding groove. After reuse, they form a transverse diaphragm plate. The transverse diaphragm plate has a top transverse prestressing through hole and a bottom transverse prestressing through hole. The transverse diaphragm plate has steel bars that are inserted into the cutting block through drilled holes. When the bridge span to be demolished has other bridge deck structures or abutments that affect the construction of the transverse diaphragm plate, the span is simultaneously lifted so that the bottom plate of the hollow slab of the span is higher than the original pavement layer surface, and then temporarily fixed before the transverse diaphragm plate is made.

[0033] Compared to concrete diaphragms, steel diaphragms are easier to construct. Steel diaphragm pieces are fabricated at both ends of the cut block and at any point between them; steel diaphragm pieces at the same longitudinal position are divided into left and right halves, and during reuse, the two adjacent steel diaphragm pieces are connected to form a single steel diaphragm; steel diaphragms at the same transverse position participate in forming a transverse beam of the new bridge, enhancing the overall integrity of the new bridge.

[0034] The beneficial effects of this invention include the following aspects:

[0035] (1) The technical solution of the present invention breaks through the conventional practice in the industry. It no longer removes the hinged concrete in the narrow space with internal reinforcing steel bars. Through simple cutting operations, I-shaped cutting blocks are obtained to realize the demolition of hollow slab bridge, which greatly reduces the amount of demolition work and speeds up the construction progress.

[0036] (2) The cutting blocks are I-shaped and no longer have internal cavities, which makes it possible to carry out various reinforcement operations and connect adjacent cutting blocks during reuse.

[0037] (3) The demolition work uses conventional small tools, which facilitates the simultaneous operation of multiple spans of hollow slab bridges in the entire project, and multiple working faces can be carried out simultaneously in the same span, thus speeding up the construction progress.

[0038] (4) The cutting blocks are I-shaped, which can be used as I-beams when they are reinforced and reused, or they can be reassembled into hollow slabs, making them flexible and diverse for reuse.

[0039] (5) The technical solution of the present invention retains the paving layer above the hinge joint during demolition, which is beneficial to improving the integrity of the cutting block and enhancing the safety of construction;

[0040] (6) The adjacent cutting blocks alternately retain the long and short protruding steel bars in the same groove. When the cutting blocks are reused, I-beams and transverse prestressing technology are used. The combination of these measures can effectively improve the connection strength at the joint when reused.

[0041] (7) When reinforcing the cutting blocks, temporary prestressing and flipping processes are used to facilitate the pouring of ultra-high performance concrete and improve its bond strength with the connecting surface.

[0042] (8) The lifting of the cut blocks after flipping can generate pre-stress in the ultra-high performance concrete layer at the bottom plate after reuse, which improves the bearing capacity of the bridge after reuse.

[0043] (9) Adding an ultra-high performance concrete overlay layer on the original bridge deck pavement layer is beneficial to improving the load-bearing capacity of the reused structure, improving the waterproofing capacity of the bridge deck, and improving the durability of the bridge deck structure.

[0044] (10) Casting transverse diaphragms at both ends and mid-span of the cut block and connecting the corresponding transverse diaphragms during reuse can enhance the integrity of the entire structure, prevent the prestressed tendons of the bottom plate from causing damage to the end bottom plate when bearing vehicle loads, and improve the bearing capacity of the bridge; making transverse diaphragms before cutting the hollow slab can prevent the prestressed tendons of the bottom plate from causing the end bottom plate to crack and break during cutting, and can further ensure safety.

[0045] (11) Applying protective coating to the exposed sides and bottom of the cut blocks can enhance the durability of the new bridge;

[0046] (12) The cut blocks can be reinforced and reused as I-beams, allowing for a certain distance between adjacent cut blocks. A new upper layer can be poured, and diaphragms can be used to enhance the transverse integrity. This allows the cut blocks of the original span to be used as the main beam of the widened span, avoiding the need to prefabricate new main beams when constructing new bridges.

[0047] (13) An extended connecting steel plate is installed between the adjacent hollow slabs “horseshoe”. Ultra-high performance concrete is poured on the upper surface of the flipped cutting block. The connecting steel plate becomes a shear connector. This design cleverly utilizes the original structural features and enhances the connection between the newly poured ultra-high performance concrete and the lower surface of the hollow slab bottom plate.

[0048] (14) Temporary bolts can be installed in the top transverse prestressed through holes and the bottom transverse prestressed through holes of the cutting block to ensure the integrity of the cutting block during hoisting and flipping.

[0049] (15) The transverse diaphragm plates cast on the cut blocks are of two types: those with protrusions and those with corresponding grooves. The adjacent cut blocks are tightly spliced ​​together by structural adhesive and transverse prestress. This method of splicing precast main beams is efficient and enhances the overall integrity of the completed bridge.

[0050] (16) The dismantled components can be reused after being reinforced, which can avoid waste of resources. Attached Figure Description

[0051] Figure 1 A schematic diagram of the original bridge cross section with support in Example 1;

[0052] Figure 2 Schematic diagram of the outward reinforcing bars of the beam in a hollow slab;

[0053] Figure 3 Schematic diagram of the reinforcing steel structure at the hinge joint;

[0054] Figure 4 A schematic diagram of the bridge cross-section after the surface layer and guardrails have been removed;

[0055] Figure 5 A schematic diagram of the cross-section of a bridge after the paving layer above the middle plate has been grooved.

[0056] Figure 6 A top view of the grooves in the bridge deck;

[0057] Figure 7 Schematic diagram of the cutting location of the central beam;

[0058] Figure 8Schematic diagram of the cross-section of the cut edge beam block after cutting;

[0059] Figure 9 Schematic diagram of the cross-section of the cut block of the central beam after cutting;

[0060] Figure 10 A schematic diagram of the bridge cross section after the UHPC overlay layer was poured in Example 1;

[0061] Figure 11 A schematic diagram of the cross-section of the new bridge after its completion in Example 1;

[0062] Figure 12 A schematic diagram of the cross-section of the beam cutting block after applying temporary longitudinal prestress in Example 2;

[0063] Figure 13 A schematic diagram of the cross-section of the beam cutting block after the installation of the connector in Example 2;

[0064] Figure 14 Schematic diagram of the connecting plate in Example 2;

[0065] Figure 15 Schematic diagram of the construction of the bottom slab reinforcement layer in Example 2;

[0066] Figure 16 Schematic diagram of the arching formation of the cutting block in Example 2;

[0067] Figure 17 A side view of the reinforced web in Example 2;

[0068] Figure 18 A schematic diagram of the bridge cross section after the UHPC overlay layer was poured in Example 2;

[0069] Figure 19 A schematic diagram of the cross-section of the new bridge after its completion in Example 2;

[0070] Figure 20 Schematic diagram of the base plate reinforcement steel plate in Example 3;

[0071] Figure 21 Schematic diagram of the rear side view of the steel plate reinforcing the bottom plate of the cutting block in Example 3;

[0072] Figure 22 Schematic diagram of the cross section after the bottom plate of the edge-cutting block is reinforced with steel plate in Example 3;

[0073] Figure 23 Schematic diagram of the cross-section of the bottom plate of the cutting block reinforced with steel plate in Example 3;

[0074] Figure 24 A schematic diagram of the cross-section of the new bridge after its completion in Example 3;

[0075] Figure 25 Schematic diagram of the cross-section connecting the cutting blocks in Example 4;

[0076] Figure 26 A schematic diagram of the transverse diaphragm plate cast on the middle cutting block in Example 3.

[0077] The numbers in the diagram correspond to the following names: 1. Cap beam, 2. Support pad stone, 3. Rubber bearing, 4. Side beam, 5. Middle beam, 6. Guardrail, 7. Pavement layer, 8. Asphalt concrete layer, 9. Hinge joint, 901. Bottom portal reinforcement, 902. Sealing mortar, 903. Longitudinal reinforcement within the joint, 904. Cross reinforcement, 905. Horseshoe joint, 906. Hinge joint concrete, 10. Stop block, 11. Top longitudinal portal reinforcement, 12. Top transverse portal reinforcement, 13. Cutting line, 14. Chemical anchor, 15. Guardrail 17. Embedded steel bars, 20. Bridge deck groove, 21. Bridge deck transverse reinforcement, 22. Reinforcement cut-off position, 23. Transverse prestressing hole, 24. UHPC overlay layer, 25. Transverse prestressing tendon, 26. Anchor plate, 27. Longitudinal prestressing tendon, 28. Double-channel steel beam, 29. Connecting steel plate, 30. UHPC reinforcement layer of bottom plate, 31. Jack, 32. Anchor bar, 33. Web reinforcement steel plate, 34. Bottom plate reinforcement steel plate, 35. I-shaped connector, 36. Transverse diaphragm plate. Detailed Implementation

[0078] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0079] The directional terms used in the embodiments are conventional engineering terms and not strictly defined. For example, "above" refers to the upper surface of the completed part of the structure, and also includes the upper surface of the auxiliary components located diagonally above its influence range. When indicating direction, "above" includes both directly above and diagonally above. Directional terms such as "left" and "right" are only used to accompany the accompanying drawings and facilitate explanation.

[0080] Example 1

[0081] The bridge in this embodiment is a 16-meter span reinforced concrete hollow slab bridge. Due to road widening, the hollow slab bridge needs to be demolished first, and then reused after adjusting the pier cap beams. A schematic diagram of the bridge cross-section through the supports is shown below. Figure 1The image shows the right lane of a two-lane road with a 2% cross slope to the right. The bridge span consists of 12 hollow slabs. The central beam 5 has a bottom width of 0.99m, the side beams 4 have a bottom width of 0.995m, the outer cantilever is 0.375m long, and the bridge width is 12.750m. A hinge joint 9 connects adjacent hollow slabs, with a bottom width of 1cm. The guardrails 6 on both sides are 0.5m wide, resulting in an effective bridge deck width of 11.75m between the guardrails 6. The asphalt concrete layer 8 and the pavement layer 7 are both 100mm thick, constructed using C50 concrete. A waterproof layer is applied between the asphalt concrete layer 8 and the pavement layer 7. The hollow slabs are supported by rubber bearings 3 on the bearing pads 2, and there are stop blocks 10 on both sides of the cap beam 1. The road needs to be widened, requiring the removal of the hollow slab bridge to achieve an effective bridge deck width of 15.75m.

[0082] Figure 2 This is a schematic diagram of the outward-protruding reinforcement of beam 5. The protruding bumps on both sides at the bottom are commonly called "horseshoes." Bottom portal reinforcement 901 extends from the intersection of its upper end and the outer surface of the hollow slab web. The width of bottom portal reinforcement 901 is 150mm. Top surface longitudinal portal reinforcement 11 and top surface transverse portal reinforcement 12 extend from the top surface of the hollow slab. The former has a width of 150mm, and the latter has a width of 200mm. The reinforcement structure at the hinge joint is shown in [reference needed]. Figure 3 In addition to the bottom portal reinforcement 901, the hinge joint 9 contains longitudinal reinforcement 903 and cross reinforcement 904. The upper ends of the cross reinforcement 904 are all horizontally cast in the pavement layer 7. The longitudinal portal reinforcement 11 on the top surface of the hollow slabs on both sides are bent and contact each other. The vertical gap between the two "horseshoe" sections at the bottom of the hinge joint 9 is filled with bottom sealing mortar 902, and the remaining space of the hinge joint 9 is filled with hinge joint concrete 906.

[0083] The main construction steps of the demolition are as follows:

[0084] Step 1: Remove the asphalt concrete layer 8 from the bridge deck, dismantle the guardrail 6, and retain the pre-embedded steel bars 17 in the guardrail; see the schematic diagram of the bridge cross-section after completing this step. Figure 4 .

[0085] Step 2: Remove the concrete paving layer above the cavity of the central beam, see... Figure 5 A bridge deck groove 20 is formed on the cross-section of the central beam, and the bridge deck groove 20 extends longitudinally along the hollow slab; alternately, near one transverse side of the bridge deck groove 20, along the steel reinforcement cut-off position 22, the bridge deck transverse reinforcement 21 of the pavement layer 7 within the bridge deck groove 20 is cut off, see... Figure 6 ; the longer section of the bridge deck transverse reinforcement 21 after bending and cutting; along the vertical centerline of the cross section of the middle beam, cut the top and bottom plates of the middle beam, see cutting line 13. Figure 7First, use a rebar detector to locate the longitudinal rebar in the top slab of the hollow slab below the bridge deck groove 20. Similarly, use the rebar detector to locate the longitudinal rebar in the bottom slab of the central beam. If there is a rebar under cutting line 13, move cutting line 13 to avoid the rebar. Cut the top slab of the central beam below the bottom surface of the bridge deck groove 20, and cut the bottom slab of the central beam from under the bridge. Lift off each cut block; cut blocks including the side beams are as follows. Figure 8 As shown, the middle cutting block is as follows Figure 9 As shown in the two figures, transverse prestressed holes 23 have been drilled.

[0086] Step 3: Repair the cutting block. Specific tasks include:

[0087] Step 3-1: Use the tapping method to check whether there are gaps or debonding between the bottom surface of the pavement layer and the top slab of the hollow core slab, and remove the pavement layer concrete in the gaps or debonding areas.

[0088] Step 3-2: Use the impact elastic wave method to check whether there is any void or debonding between the concrete and the hollow slab in the hinge joint 9; inject epoxy resin structural grout into the void or debonding area in the hinge joint 9 to repair the connection between the concrete and the hollow slab in the hinge joint 9 and enhance the connection strength of the hinge joint.

[0089] Step 3-3: Rinse the exposed bottom and sides of the cutting block with high-pressure water and apply a silane protective liquid with impregnation capabilities;

[0090] Step 4: Drill transverse prestressed through holes 23 near the bottom of the hollow slab and near the bottom of the hollow slab on the cutting block;

[0091] Step 5: Modify the existing cap beam 1 by increasing the cantilever length at both ends of the cap beam 1 of the pier, and adjust the height of the support pad stone.

[0092] Step 6: Install the cutting blocks and apply epoxy resin structural adhesive to the splicing surfaces;

[0093] Step 7: Insert transverse prestressing tendons 25mm; tension the transverse prestressing, see... Figure 10 ;

[0094] Step 8: Pour ultra-high performance concrete (UHPC) to repair pavement layer 7 and form UHPC overlay layer 24 on top of the original pavement layer 7; pour guardrail 6; construct bridge deck surface layer; see the completed bridge. Figure 11 The completed bridge appears to be composed of 16 hollow slabs, with a total width of 16.750m and a net width of 15.750m.

[0095] Example 2

[0096] This embodiment is an improvement on Embodiment 1, consisting of a 20-meter span hollow slab bridge. The remaining structure is the same as the bridge span in Embodiment 1. The biggest difference in this embodiment is that the bottom slab contains longitudinal prestressing tendons, making it a prestressed hollow slab.

[0097] The main difference in the construction process lies in step 3, which is as follows in this embodiment:

[0098] Step 3: Repair the cutting block. Specific tasks include:

[0099] Step 3-1: Use the tapping method to check whether there are gaps or debonding between the bottom surface of the pavement layer and the top slab of the hollow core slab, and remove the pavement layer concrete in the gaps or debonding areas.

[0100] Step 3-2B: Install corresponding double-channel steel beams 28 on the upper part of both longitudinal ends of the cut block. Place flat anchor plates 26 on the double-channel steel beams 28. Temporary longitudinal prestressing tendons 27 are symmetrically tensioned on both sides to compress the top plate of the hollow slab. See Figure 12 Remove the grout from the horseshoe joint (905); flip the cut block over and over, see... Figure 13 ;

[0101] Step 3-2: Use the impact elastic wave method to check whether there is any void or debonding between the concrete and the hollow slab in the hinge joint 9; inject epoxy resin structural grout into the void or debonding area in the hinge joint 9 to repair the connection between the concrete and the hollow slab in the hinge joint 9 and enhance the connection strength of the hinge joint.

[0102] Step 3-2C: Secure both ends of the flipped cutting block with anchor bars 32, and use jacks 31 to lift it upwards from below the mid-span, causing the cutting block to arch as desired. See Figure 16 .

[0103] Step 3-2D: Install the extended connecting steel plate 29 between the adjacent hollow slab "horseshoe" shapes. See the detailed schematic diagram of the connecting steel plate 29. Figure 14 Ultra-high performance concrete was poured onto the upper surface of the flipped cut block to form a UHPC reinforcement layer 30 on the base plate. (See figure) Figure 15 After the ultra-high performance concrete reaches the specified strength, the cut block is flipped back to its normal position.

[0104] Step 3-2E: On the outer surface of the web at both ends of the cutting block, install oblique web reinforcement steel plates 33 using chemical anchors 14. Epoxy resin structural adhesive is applied between the web reinforcement steel plates 33 and the cutting block. (See...) Figure 17 .

[0105] Step 3-3: Rinse the exposed bottom and sides of the cutting block with high-pressure water and apply a silane protective liquid with impregnation capabilities.

[0106] In this embodiment, a schematic diagram of the bridge cross-section after the UHPC overlay layer 24 is poured is shown below. Figure 18 A cross-sectional diagram of the completed new bridge can be found here. Figure 19 .

[0107] Example 3

[0108] This embodiment is an improvement on embodiment 1. The cutting blocks are reinforced by bonding steel plates. The steel bonding reinforcement method for the web is the same as in embodiment 2. The key is that the overall integrity of the new bridge is improved by adding diaphragms.

[0109] Step 3-2F: Install the base plate reinforcing steel plate 34 longitudinally on the lower surface of the base plate of the cutting block, see... Figure 20 and Figure 21 The base plate reinforcing steel plate 34 has three rows of screw holes at each end of the cutting block, with two holes at the top and two at the bottom of each row, and the two sets are located close to their respective edges. The first and second rows from the end correspond to the support positions. Epoxy resin structural adhesive is applied between the base plate reinforcing steel plate 34 and the cutting block, and then chemical anchors 14 are used to fix the base plate reinforcing steel plate 34. A cross-sectional diagram of the base plate reinforcing steel plate after the cutting block is shown in the figure. Figure 22 See the schematic diagram of the cross-section after the bottom plate of the middle cutting block is reinforced with steel plate. Figure 23 .

[0110] Step 3-2H: Next, we will make the diaphragm panels. Figure 26 This is a schematic diagram of the transverse diaphragm plates cast on the intermediate cutting block in this embodiment. Transverse diaphragms are cast at both ends and the middle of the cutting block. Figure 26 This is a schematic diagram of the transverse diaphragms cast on the intermediate cut block. There are two types of transverse diaphragm plates 36: the left one has an outward-protruding protrusion, and the right one has a corresponding groove. The reinforcing bars within the transverse diaphragm plates 36 are inserted into the cut block through drilled holes. Transverse prestressing holes 23 are also present at the top and bottom of the transverse diaphragm plates 36. When adjacent cut blocks are joined, epoxy resin adhesive is applied to the contact surfaces of the connecting transverse diaphragm plates 36.

[0111] The remaining construction steps are the same as in Example 1. In the reused new bridge, the bottom plate and web of the main beam have been reinforced with steel plates bonded together, which has improved the strength of the components. The transverse diaphragms composed of 36 transverse diaphragm plates, together with the transverse prestressing, have improved the overall integrity of the new bridge. A schematic diagram of the cross-section of the completed new bridge can be seen in [reference needed]. Figure 24 .

[0112] Example 4

[0113] This embodiment is an improvement upon Embodiment 1, refining the connection method between the top and bottom plates during the splicing of the cutting blocks. The main change is in step 6: The new step 6 involves installing the cutting blocks, with I-shaped connectors 35 installed between the top and bottom plates of adjacent cutting blocks. (See attached image) Figure 25Epoxy resin structural adhesive is applied between the I-shaped connector 35 and the cutting block. During installation, the cutting block with the I-shaped connector 35 already connected is installed first. The subsequently installed cutting block has the I-shaped connector 35 installed on only one side, and the other side is connected to the I-shaped connector 35 of the already installed cutting block.

Claims

1. A method for dismantling and reusing hollow slab bridges, characterized by: During the demolition of the hollow slab bridge, the top and bottom slabs of the central beams are cut longitudinally, leaving the hinge joints. During reuse, the cut blocks, after repair and reinforcement, are assembled laterally, and transverse prestressing is applied to increase the overall integrity of the new bridge. The main construction steps include the following: Step 1: Remove the surface layer of the bridge and dismantle the guardrails; Step 2: Remove the concrete pavement layer above the cavity of the central beam to form a groove on the cross section of the central beam, with the groove running longitudinally along the hollow slab; alternately approach the transverse side of the groove and cut off the transverse reinforcing bars of the pavement layer inside the groove; bend up the longer section of the cut transverse reinforcing bars and cut the top plate of the central beam below the bottom surface of the groove; cut the bottom plate of the central beam from under the bridge; lift off each cut block; Step 3: Repair and reinforce the cutting block. Specific tasks include: Step 3-1: Check for any gaps between the bottom surface of the pavement layer and the top slab of the hollow core slab, and remove the concrete of the pavement layer in the gapped area; Step 3-2: Check if there is any void between the concrete and the hollow slab in the hinge joint; inject reinforcing grout into the voided area in the hinge joint to repair the connection between the concrete and the hollow slab in the hinge joint and enhance the connection strength of the hinge joint. Step 3-3: Clean the exposed bottom and sides of the cutting block and apply protective coating; Step 4: Drill a top transverse prestressing through hole near the bottom of the hollow slab on the cutting block, and drill a bottom transverse prestressing through hole near the bottom of the hollow slab on the cutting block. Step 5: Construct new pier cap beams and their bearing pads, or modify existing pier cap beams and their bearing pads. Step 6: Install the reinforced cutting blocks and apply structural adhesive to the splicing surfaces; Step 7: Insert transverse prestressing tendons; tension the transverse prestressing; Step 8: Pour the pavement layer to repair the concrete; install or pour the guardrails, and construct the bridge deck surface layer.

2. The method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: A step 3-2B is added before step 3-2, and a step 3-2D is added after step 3-2. Step 3-2B: Install corresponding crossbeams on the upper part of both longitudinal ends of the cutting block, and use the crossbeams to tension the longitudinal temporary prestressing tendons, so that the top plate of the hollow slab is compressed; flip the cutting block up and down; Step 3-2D: Install the outward connecting steel plate between the adjacent hollow slab "horseshoes", and pour ultra-high performance concrete on the upper surface of the flipped cutting block; after the ultra-high performance concrete reaches the specified strength, flip the cutting block back to its normal position.

3. The method for dismantling and reusing a hollow slab bridge according to claim 2, characterized in that: A step 3-2C is added before step 3-2D. Step 3-2C: Fix both ends of the flipped cutting block, and use a jack to lift it upwards from below the middle of the span, so that the cutting block produces the expected upward arch.

4. The method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: Step 3-2E is added after step 3-2. Step 3-2E: Install diagonal steel strips on the outer surface of the web at both ends of the cutting block using chemical anchors. Structural adhesive is applied between the diagonal steel strips and the cutting block.

5. The method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: Step 3-2F is added after step 3-2. Step 3-2F: Install the bottom reinforcing steel component longitudinally on the lower surface of the bottom plate of the cutting block, and connect the bottom reinforcing steel component to the cutting block with bolts or chemical anchors. Structural adhesive is applied between the bottom reinforcing steel component and the cutting block.

6. The method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: Step 6 is further refined as follows: Step 6: Install the reinforced cutting blocks. I-shaped connectors are installed between the top and bottom plates of adjacent cutting blocks. Structural adhesive is applied between the I-shaped connectors and the cutting blocks. Structural adhesive is also applied to the contact surfaces of the connected diaphragm plates.

7. The method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: Step 8 is further refined as follows: Step 8: Pour ultra-high performance concrete on the bridge deck to cover the original pavement layer, with the upper layer being 2 to 10 centimeters thicker than the original pavement layer; install or pour guardrails and construct the bridge deck surface layer.

8. The method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: In the final stage of step 3-2, step 3-2H is added. Step 3-H: Cast transverse diaphragm plates at both ends of the cutting block and at any position between the two ends; the transverse diaphragm plates are located in the exposed cavity of the middle beam on the cross section of the cutting block; the transverse diaphragm plates of the middle cutting block are divided into left and right pieces, one of which has a protrusion and the other has a corresponding groove; there are transverse prestressing through holes at the top and bottom of the transverse diaphragm plates; there are reinforcing bars inserted into the cutting block through drilled holes in the transverse diaphragm plates.

9. A method for dismantling and reusing a hollow slab bridge according to claim 1, characterized in that: Step 1A is added after step 1. Step 1A: Cast two transverse diaphragm plates into the cavities at both ends of the central beam. Before casting, the two are separated by a template. One transverse diaphragm plate has a protrusion and the other has a corresponding groove. After reuse, they form a transverse diaphragm plate. The transverse diaphragm plate has a top transverse prestressing through hole and a bottom transverse prestressing through hole. The transverse diaphragm plate has steel bars that are inserted into the cutting block through drilled holes. When the bridge span to be demolished has other bridge deck structures or abutments that affect the construction of the transverse diaphragm plate, the span is simultaneously jacked up so that the bottom plate of the hollow slab of the span is higher than the original pavement layer. After temporary fixation, the transverse diaphragm plate is then made.

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