A construction method for demolishing hollow slab bridges while preserving the hollow slabs.

Abstract

This invention relates to a method for demolishing hollow slab bridges while preserving the hollow slabs, belonging to the field of bridge construction technology. Current methods for demolishing hollow slabs require significant manual labor and are prone to damaging the slabs, rendering them unusable. This invention first removes the mortar from the lower part of the hinge joint (the horseshoe area) under the bridge deck using a pneumatic hammer. Then, a high-pressure water jet removes the hinge joint concrete above the horseshoe area. Next, a downward cut is made on the bridge deck close to the hollow slab to be demolished. Multiple grooves are then chiseled along the cut, and hydraulic splitting shears are inserted to split the slab from one end of the bridge span to the other, detaching the hollow slab from the hinge joint concrete. This method requires less work under the bridge and uses simpler tools, ensuring the integrity of the demolished hollow slabs and preserving the protruding reinforcing bars, facilitating repair and reuse, avoiding resource waste, and contributing to achieving the "dual carbon" target (carbon reduction and emission reduction).

Description

Technical Field

[0001] This invention relates to a method for demolishing bridges, and more particularly to a method for demolishing hollow slab bridges while preserving the hollow slabs, 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 removal of hollow slabs. For hollow slabs in relatively good technical condition, it is desirable to remove and repair them for continued use in existing or other projects to achieve resource conservation.

[0003] Current hollow slab removal operations primarily involve 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 them unusable. Therefore, there is an urgent need for an efficient hollow slab removal technology that ensures the removed slabs remain intact and can be easily reused. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, this invention develops a construction method for demolishing hollow slab bridges while preserving the original hollow slabs. The purpose is to achieve efficient demolition of hollow slabs while retaining the original protruding steel bars of the hollow slabs, so as to facilitate the reuse of the demolished hollow slabs.

[0005] The technical solution proposed in this invention is a construction method for demolishing hollow slab bridges while preserving the hollow slabs, which mainly includes the following construction steps:

[0006] Step 1: Remove the surface layer of the bridge deck, remove the guardrails, and remove the concrete pavement layer of the bridge deck;

[0007] Step 2: Remove the hinge sealant material from the vertical section of the hinge joint at the bottom;

[0008] Step 3: Remove the concrete from the hinge joint area where the portal reinforcement is located;

[0009] Step 4: Move the reinforcing bar above the hinge joint and cut downwards along the hinge joint. The cutting position should be horizontally close to the hollow slab being demolished, avoiding cutting the intersecting reinforcing bars inside the hinge joint and the portal reinforcement bars of the two adjacent hollow slabs extending above the hinge joint.

[0010] Step 5: Push the hollow slab being demolished to separate it from the hinge joint concrete;

[0011] Step 6: Lift the hollow slab being dismantled.

[0012] Preferably, the construction order of step 1 and step 2 is interchanged, or the two steps are performed simultaneously; the construction order of step 3 and step 4 is interchanged, or the two steps are performed simultaneously.

[0013] Preferably, step 3 includes the following sub-steps:

[0014] Step 3-1: Along the vertical section of the lower hinge joint, use a pneumatic hammer to chisel away the hinge joint concrete directly above the gap, extending upwards beyond the portal reinforcement inside the hinge joint;

[0015] Step 3-2A: From the bottom of the hollow slab upwards, through the gap in the vertical section of the hinge joint, insert a high-pressure water jet into the hinge joint to break the hinge joint concrete above the "horseshoe" of the hollow slab, extending upwards beyond the portal reinforcement inside the hinge joint.

[0016] Preferably, step 3 includes the following sub-steps:

[0017] Step 3-1: Along the vertical section of the lower hinge joint, use a pneumatic hammer to chisel away the hinge joint concrete directly above the gap, extending upwards beyond the portal reinforcement inside the hinge joint;

[0018] Step 3-2B: Insert a high-pressure water jet into the hinge joint from the pier at one end of the bridge span to break the hollow slab.

[0019] The height of the concrete joint above the "horseshoe" is greater than that of the portal reinforcement inside the joint.

[0020] Preferably, step 5 is further refined as follows:

[0021] Step 5A: Along the cutting seam on the hinge joint, chisel out multiple grooves at the top of the hinge joint, and insert hydraulic splitting pliers into the grooves; the hydraulic splitting pliers separate the hollow slab being demolished from the hinge joint concrete.

[0022] Preferably, step 5 is further refined as follows:

[0023] Step 5B: On the pier of the bridge span or on the support connected to the pier, place the jack vertically or horizontally under the hollow slab being demolished, start the oil pump to extend the jack, push the hollow slab being demolished, and separate the hollow slab from the hinge joint concrete.

[0024] Preferably, step 4 can be omitted before proceeding with step 5B as described above.

[0025] Preferably, step 5 is further refined as follows:

[0026] Step 5C: On the pier of the bridge span or on the support connected to the pier, place a two-way jack under the hollow slab being demolished. The jack can extend and retract in both horizontal and vertical directions. The combined action of the two directions separates the hollow slab from the hinge joint concrete.

[0027] Preferably, step 4 can be omitted before proceeding with step 5C above.

[0028] Preferably, the hydraulic cylinder of the jack is connected to a hydraulic servo valve, which controls the oil pressure on the oil inlet side to generate excitation force, thereby accelerating the separation of the hollow slab from the hinge joint concrete.

[0029] The beneficial effects of this invention include the following aspects:

[0030] (1) In the technical solution of the present invention, the amount of work under the bridge can be reduced and the construction safety can be improved; especially when a high-pressure water jet is inserted into the hinge joint at one end of the bridge span, the work under the bridge only requires the removal of the sealing mortar of the hinge joint by a pneumatic pick.

[0031] (2) The operation of separating the hollow plate in the technical solution of the present invention can use small tools, mainly only pneumatic hammers, circular saws and water jets, which makes construction convenient.

[0032] (3) The technical solution of the present invention facilitates the simultaneous operation of multiple spans of hollow slab bridges in the whole project, and the upper and lower hinge joints of the same span can be constructed at the same time, which speeds up the construction progress.

[0033] (4) Although water jetting is not very common and the cost of using it is generally high, the amount of concrete in the hinge joint that needs to be broken is very small, the breaking speed is fast, and the cost per hollow slab is low, so the cost of the whole demolition operation is low.

[0034] (5) The technical solution of the present invention protects the hollow slab to the maximum extent. The web of the hollow slab near the hinge joint is less damaged, and all the protruding steel bars of the hollow slab are preserved. Therefore, the hollow slabs removed are of high quality and easy to reuse.

[0035] (6) The dismantled hollow slabs can be reused after simple repairs, which can avoid waste of resources and help achieve the "dual carbon" target;

[0036] (7) During the demolition process, the portal reinforcement in the hinge joint is separated from or the connection with the surrounding concrete is weakened. Based on the principle of fracture mechanics, the hollow slab is easily separated by taking advantage of the relatively low bonding strength between the hinge joint concrete and the outer side of the hollow slab. This technical solution is ingeniously conceived, efficient in construction, energy-saving, and in line with the concept of green and sustainable development. Attached Figure Description

[0037] Figure 1 Schematic diagram of the cross section of the bridge with supports in Example 1;

[0038] Figure 2 Schematic diagram of the outward reinforcing bars of the beam in a hollow slab;

[0039] Figure 3 Schematic diagram of the reinforcing steel structure at the hinge joint;

[0040] Figure 4 A schematic diagram of the bridge cross-section after the surface layer and guardrails have been removed;

[0041] Figure 5 Schematic diagram of the cross section of the mid-span hinge joint after the removal of the surface layer and guardrail;

[0042] Figure 6 A schematic diagram of the cross-section of the hinge joint at the support after the surface layer and guardrail have been removed;

[0043] Figure 7 A schematic diagram of the cross-section of the hinge joint after the bottom of the hinge joint has been excavated.

[0044] Figure 8 A schematic diagram of the cross-section of the hinge joint after the bottom of the hinge joint has been chiseled and the top plate has been cut.

[0045] Figure 9 A schematic diagram of the cross-section of the mid-span hinge joint after a hole has been cut at the bottom of the hinge joint using water cutting.

[0046] Figure 10 A schematic diagram of the cross-section of the hinge joint at the support after the hole at the bottom of the hinge joint has been cut with water.

[0047] Figure 11 A top view of the hinge joint after slotting at the top in Example 1;

[0048] Figure 12 A schematic diagram of the cross-section of the right hollow plate after it has been separated in Example 1;

[0049] Figure 13 Schematic diagram of jack arrangement in Example 2;

[0050] Figure 14 A schematic diagram of the cross-section of the right hollow plate after it has been separated in Example 2;

[0051] Figure 15 A schematic diagram of the jack arrangement in Example 3;

[0052] Figure 16 A schematic diagram of the cross-section of the right hollow plate after it has been separated in Example 3.

[0053] 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. Crane protection wall, 7. Pavement layer, 8. Asphalt concrete layer, 9. Hinge joint, 10. Top longitudinal portal reinforcement, 11. Top transverse portal reinforcement, 12. Splitting groove, 13. Jack, 14. PTFE sliding plate, 15. Steel pad, 16. Guardrail embedded steel reinforcement, 17. Bottom portal reinforcement, 901. Bottom sealing mortar, 902. In-joint longitudinal reinforcement, 903. Cross reinforcement, 904. Hinge joint concrete, 906. Lower slot, 907. Cutting seam, 908. Hole, 909. Horseshoe joint, 910. Detailed Implementation

[0054] 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.

[0055] 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.

[0056] Example 1

[0057] The bridge in this embodiment is a hollow slab bridge. Due to road widening, the hollow slabs need to be removed first, and then reused after adjusting the pier cap beams. The cross-sectional diagram of the hollow slab bridge with a span of 20m at the supports is shown below. Figure 1 The diagram shows the right lane of a two-lane road with a 2% cross slope to the right. The bridge span consists of 10 hollow slabs; the central beam 5 has a bottom width of 0.99m, and the side beams 4 have a bottom width of 0.995m. A hinge joint 9 connects adjacent hollow slabs, with a bottom width of 1 cm. Two crash barriers 6 on each side are 0.5m wide, resulting in an effective bridge deck width of 10.25m between the crash barriers 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.

[0058] Figure 2This 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.

[0059] The main construction steps for demolition are as follows.

[0060] Step 1: Remove the asphalt concrete layer 8 of the bridge deck, demolish the crash barrier 6, remove the concrete within the bridge deck pavement layer 7, and retain the pre-embedded steel bars 17 of the guardrails; see the schematic diagram of the bridge cross-section after completing this step. Figure 4 See the schematic diagram of the cross-section of the mid-span hinge joint. Figure 5 See the schematic diagram of the cross-section of the hinge joint at the support. Figure 6 .

[0061] Step 2: Use a pneumatic pick to remove the sealing mortar 902 from the lower vertical section of the joint 9. This vertical section is called the horseshoe joint 910.

[0062] Step 3-1: Using a pneumatic pick, chisel upwards along the horseshoe joint 910 to remove the concrete 906 directly above the hinge joint, extending upwards beyond the bottom door reinforcement 901 within the hinge joint 9. The resulting cross-sectional diagram of the hinge joint is shown below. Figure 7 As shown, the groove above the horseshoe-shaped seam 910 is called the lower groove 907.

[0063] Step 4: While carrying out construction work under the bridge deck, commence work on the bridge deck. Move the intersecting reinforcing bars 904 and the top longitudinal portal reinforcement 11 above hinge joint 9, and use a circular saw to cut downwards 25 cm along hinge joint 9, with the cut 908 positioned laterally close to the right-side hollow slab. This operation avoids cutting the intersecting reinforcing bars 904 and the portal reinforcement extending from the two adjacent hollow slabs above hinge joint 9. The completed cross-section of the hinge joint is shown in the image. Figure 8 .

[0064] Step 3-2: From the bottom of the hollow slab upwards, through the horseshoe joint 910, insert a high-pressure water jet into the downward groove 907 to break the hinge joint concrete 906 above the "horseshoe" of the hollow slab, with a height greater than the bottom door reinforcement 901, forming a hole 909; see the schematic diagram of the completed mid-span hinge joint cross-section. Figure 9 See the schematic diagram of the cross-section of the hinge joint at the support. Figure 10 Waterjet cutting is a type of cold cutting that directly utilizes the kinetic energy of an abrasive water jet to cut objects. There are no chemical changes during the cutting process, and it has advantages such as no impact on the physical and chemical properties of the material being cut, no thermal deformation, narrow kerf, high precision, and cleanliness without pollution.

[0065] Step 5: Along the left side of the cutting seam 908 on the hinge seam 9, chisel out splitting grooves 13. The longitudinal spacing of the splitting grooves 13 is 1.5m. See Figure 11 Insert hydraulic splitting shears into the splitting groove 13, and activate the hydraulic splitting shears to separate the right hollow plate from the hinge joint concrete 906. Figure 12 Using a set of several hydraulic splitting shears, the splitting operation is carried out sequentially from one end of the bridge span to the other. This method makes full use of the fracture characteristics and facilitates efficient splitting operations with limited tools.

[0066] Step 6: Lift the separated right hollow slab.

[0067] Example 2

[0068] This embodiment is an improvement on embodiment 1. Instead of using hydraulic splitting shears on the bridge deck, jacks are used on the bridge piers to separate the hollow slabs. Figure 13 The diagram shows the arrangement of jack 14. A PTFE sliding plate 15 and a steel pad 16 are placed on the piston of jack 14. The steel pad 16 protects the bottom concrete of the hollow slab from damage caused by concentrated forces. A stainless steel plate is adhered to the lower surface of the steel pad 16. Together with the PTFE sliding plate 15, the stainless steel plate reduces horizontal frictional resistance. The upward lifting force of jack 14 causes the hollow slab to detach from the hinge joint concrete 906 within the hinge joint 9. The reduction in frictional resistance facilitates the horizontal separation of the detached hollow slab and also allows the right hollow slab to rotate counterclockwise with the assistance of the cutting seam 908, thus accelerating the detachment and separation of the hollow slab. A cross-sectional view of the right hollow slab after separation is shown below. Figure 14 .

[0069] Example 3

[0070] This embodiment is an improvement on embodiment 2, eliminating the need for bridge deck cutting and moving the cross reinforcing bars 904 above the hinge joint 9 and the longitudinal portal reinforcement 11 on the top surface. After the high-pressure water jet cuts out the hole 909, the jack 14 is installed. Figure 15 While applying force with jack 14, multiple hydraulic splitting clamps are inserted longitudinally into the horseshoe joint 910 from one end of a pier to assist in debonding the right hollow slab from the hinge joint concrete 906. These hydraulic splitting clamps are then moved to the other end. Ultimately, the entire right hollow slab is debonded from the hinge joint concrete 906, thus completing the separation of the right hollow slab from the remaining part of the bridge span. A schematic diagram after separation is shown below. Figure 16The embodiment fully utilizes the principles of fracture mechanics, reducing workload and accelerating construction progress, and is particularly suitable for hollow slab bridges that have already developed hinge joint defects.

Claims

1. A method for demolishing a hollow slab bridge of a hollow slab, characterized by: The method mainly comprises the following steps: Step 1: removing the surface layer of the bridge deck, removing the guardrail, and removing the bridge deck pavement concrete; Step 2: chiseling the hinge joint sealing material in the gap of the lower vertical section of the hinge joint; Step 3: removing the hinge joint concrete at the position of the door-shaped reinforcement in the hinge joint; Step 4: moving the reinforcement above the hinge joint, cutting downward along the hinge joint, and cutting the position transversely close to the hollow slab being removed to avoid cutting the cross reinforcement in the hinge joint and the door-shaped reinforcement of the two adjacent hollow slabs extending above the hinge joint; Step 5: placing the bidirectional jack under the hollow slab being removed on the pier of the bridge span or the support connected to the pier, wherein the jack can realize expansion and contraction in the horizontal direction and the vertical direction, and the joint action of the two directions separates the hollow slab from the hinge joint concrete; the oil cylinder of the jack is connected with a hydraulic servo valve, the oil pressure on the side of the oil inlet pipe is controlled through the hydraulic servo valve, the jack generates an excitation force to accelerate the separation of the hollow slab from the hinge joint concrete; Step 6: hoisting away the hollow slab being removed.

2. The method of claim 1, wherein: The construction sequence of the step 1 and the step 2 is interchangeable, or the two steps are performed simultaneously; the construction sequence of the step 3 and the step 4 is interchangeable, or the two steps are performed simultaneously.

3. The method of claim 1, wherein: The step 3 comprises the following sub-steps: Step 3-1: along the gap of the lower vertical section of the hinge joint, the hinge joint concrete directly above the gap is chiseled upward by a pneumatic pick, and the height is higher than the door-shaped reinforcement in the hinge joint; Step 3-2A: from the hollow slab below, a high-pressure water cutter is inserted into the hinge joint through the gap of the lower vertical section of the hinge joint to break the hinge joint concrete above the "horse's hoof" of the hollow slab, and the height is higher than the door-shaped reinforcement in the hinge joint.

4. The method of claim 1, wherein: The step 3 comprises the following sub-steps: Step 3-1: along the gap of the lower vertical section of the hinge joint, the hinge joint concrete directly above the gap is chiseled upward by a pneumatic pick, and the height is higher than the door-shaped reinforcement in the hinge joint; Step 3-2B: from the pier at one end of the bridge span, a high-pressure water cutter is inserted into the hinge joint to break the hinge joint concrete above the "horse's hoof" of the hollow slab, and the height is greater than the door-shaped reinforcement in the hinge joint.

Images