Demolition construction method for existing river channel-crossing prestressed concrete bridge

Abstract

The invention discloses a demolition construction method for an existing overpass river channel prestressed concrete bridge, and the method comprises the following specific steps: S100, carrying out the detailed detection and evaluation of the condition of the bridge, determining the condition of a bridge structure, and evaluating the demolition difficulty of the bridge; s200, carrying out simulation calculation on bridge demolition so as to determine an optimal segmented cutting demolition scheme, and determining the position of a first cutting point; s300, the prestress of the bridge is gradually released through professional equipment and technology, the internal stress of the bridge structure is adjusted, and the structure instability risk caused by sudden dismantling is reduced; s400, cutting the bridge from the position of the first cutting point according to a dismantling scheme of bridge simulation calculation, hoisting a part to be cut and removed by using hoisting equipment while cutting, and directly hoisting the part to a specified position by using the hoisting equipment after cutting is completed; when the bridge is cut, the cutting flatness and precision of the bridge sections need to be ensured.

Description

Technical Field

[0001] The invention relates to the technical field of bridge demolition, and in particular to a demolition construction method for an existing prestressed concrete bridge that crosses a river channel. Background Art

[0002] With the continuous development of transportation infrastructure and the adjustment of urban planning, more and more existing bridges need to be demolished. Among them, the demolition of prestressed concrete bridges across the river faces many challenges. On the one hand, since the bridge crosses the river, the navigation and flood discharge functions of the river must not be affected during the demolition process, and at the same time, it is necessary to prevent the waste generated by the demolition from falling into the river and causing environmental pollution. On the other hand, prestressed concrete bridges have complex structures and are difficult to demolish. Traditional demolition methods such as blasting demolition and mechanical crushing demolition have high safety risks, high noise, and serious dust pollution.

[0003] For example, a Chinese patent with patent number CN202010311425.X discloses a method for dismantling a hyperbolic arch bridge, comprising the following steps: 1) dismantling the arch bridge structure except the main arch ring; 2) building a support structure directly below the main arch ring; 3) installing support jacks at intervals between the arch ribs and the support structure; 4) adjusting the top thrust of the two symmetrical support jacks so that the axial pressure value of the arch rib crown section is less than or equal to the set balance target value; 5) splitting the two arch ribs located on both sides of the bridge in the horizontal direction; 6) drilling holes at the arch crown position of the arch rib, installing pressure jacks in the holes, and adjusting the top thrust of the pressure jacks to be equal to the axial pressure value of the arch rib crown section; 7) splitting the two arch ribs located on both sides of the bridge in the horizontal direction; 8) splitting the arch feet of the two arch ribs located on both sides of the bridge in the horizontal direction, and lifting them away using lifting equipment; 9) looping steps 5) to 8) to sequentially dismantle all the arch ribs of the arch bridge; 10) removing the construction equipment and the support structure to complete the dismantling of the hyperbolic arch bridge.

[0004] The arch bridge in the hyperbolic arch bridge demolition method provided by the above patent is a common bridge that crosses the river. The existing demolition method requires the construction of a support device and the installation of multiple hydraulic jacks; however, it is troublesome to build a support device in a river, and if the water level in the river is too deep, it will be very difficult to build a support device. Therefore, the existing bridge demolition method is not convenient for demolishing some bridges across rivers with deep rivers, and the efficiency of using this method to demolish bridges is low. Summary of the invention

[0005] The purpose of the present invention is to provide a method for dismantling an existing prestressed concrete bridge across a river, aiming to improve the problem that the existing bridge dismantling method is not convenient for dismantling some large bridges across rivers with deeper channels, and the dismantling efficiency of the existing bridge dismantling method is low.

[0006] The present invention is achieved in that:

[0007] A method for dismantling an existing prestressed concrete bridge across a river, the specific steps of the method are as follows:

[0008] S100, conduct detailed inspection and assessment of the condition of the bridge, determine the condition of the bridge structure, and assess the difficulty of dismantling the bridge;

[0009] S200, simulating and calculating the bridge demolition, thereby determining the best segmented cutting and demolition plan, and determining the position of the first cutting point;

[0010] S300, using professional equipment and technology to gradually release the prestress of the bridge, the internal stress of the bridge structure is adjusted, reducing the risk of structural instability caused by sudden demolition;

[0011] S400, according to the demolition plan calculated by simulating the bridge, the bridge is cut from the position of the first cutting point, and the part to be cut and removed is lifted by the lifting equipment during the cutting, and after the cutting is completed, the part is directly lifted to the designated position by the lifting equipment; when cutting the bridge, the smoothness and accuracy of the cutting at the bridge segment should be ensured;

[0012] S500. Use a lifting device to lift the cut bridge demolition section onto a vehicle, and move the bridge demolition section to a crushing plant for crushing. During the lifting process, the lifting speed and angle must be strictly controlled to ensure safety.

[0013] S600. After all bridges are dismantled, the river channel shall be cleaned up to remove the waste that fell into the river channel during the dismantling of the bridges, so as to ensure that the navigation and flood discharge functions of the river channel are not affected.

[0014] Furthermore, in step S100, the stability evaluation is:

[0015]

[0016] Where S is the stability evaluation value,

[0017] F a is the actual bearing capacity of the bridge,

[0018] F d is the design bearing capacity of the bridge,

[0019] D is the percentage of damage degree, which is estimated from the actual damage degree of the bridge;

[0020] A is the percentage of bridge aging degree;

[0021] The demolition difficulty is assessed as follows:

[0022]

[0023] Among them, D n is the demolition difficulty index,

[0024] B is the bridge type,

[0025] C is the structural complexity,

[0026] E is the surrounding environment,

[0027] f is a function that comprehensively considers these factors.

[0028] λ is the weight coefficient,

[0029] W is the width of the bridge,

[0030] W max is the maximum allowed width.

[0031] Furthermore, in step S200, the starting position of the bridge is taken as the zero point, and the first cutting point is determined as:

[0032]

[0033] Among them, P1 is the first cutting point position,

[0034] H(x) is the cutting difficulty coefficient,

[0035] S(x) is the safety factor,

[0036] β is the center priority coefficient, β ranges from 0 to 1;

[0037] Determine the segment length as:

[0038]

[0039] Among them, L s is the segment length,

[0040] L t is the total length of the bridge,

[0041] N is the number of segments,

[0042] L m is the maximum load-bearing length of the equipment,

[0043] α is the safety margin factor.

[0044] Furthermore, in step S300, the prestress release speed is:

[0045]

[0046] Among them, V r is the release speed,

[0047] P t is the total amount of prestress,

[0048] T is the release time,

[0049] D f is the percentage of deformation degree,

[0050] V d is the current deformation speed,

[0051] V max is the maximum allowable deformation speed.

[0052] Furthermore, in step S400, the lifting power of the crane is:

[0053]

[0054] P c is the lifting power,

[0055] W is the weight of the demolished section,

[0056] g is the acceleration due to gravity,

[0057] t is the lifting time,

[0058] γ is the lifting safety factor,

[0059] W max The maximum permissible lifting weight.

[0060] Furthermore, in step S400, before cutting the bridge into sections, a protective component is installed below the cutting position to prevent some tools and equipment as well as bridge fragments from falling into the river. The protective component can also protect the workers.

[0061] Furthermore, the protective assembly includes a protective net, a mounting rod and a shock-absorbing spring. The mounting rods are symmetrically provided on both sides of the rear end of the protective net. The mounting rods are sleeved on both sides of the rear end of the protective net. Shock-absorbing springs are provided at the top and bottom ends of the inner sides of the mounting rods, and the opposite ends of the two shock-absorbing springs on the inner side of each mounting rod are against the rear end of the protective net, so as to cushion the protective net when the protective net is impacted.

[0062] Furthermore, a frame is provided on the outside of the protective net, and the protective net is arranged in two layers up and down along the inside of the frame, and the mesh holes of the two layers of the protective net are staggered; connecting blocks are symmetrically provided on both sides of the rear end of the frame, and a through hole is provided in the middle of the connecting block for the front end of the mounting rod to pass through the through hole; a pressure block is provided at the rear end of the connecting block, and the pressure block is used to apply pressure to the shock-absorbing spring when the protective net is impacted, thereby achieving the purpose of buffering falling objects.

[0063] Furthermore, a guide opening is longitudinally provided on the inner side of the mounting rod, and threaded grooves are provided at the top and bottom ends of the inner side of the guide opening; and fixed edges are provided at the rear ends of both sides of the mounting rod, and a plurality of fixing holes are provided on the fixed edges from top to bottom.

[0064] Furthermore, a guide rod is provided inside the shock absorbing spring, and end plates are provided at the top and bottom ends of the guide rod, and both ends of the shock absorbing spring are fixedly connected to the two end plates respectively.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1. The present invention releases the prestress of the bridge, so that the risk of subsequent demolition of the bridge is greatly reduced; at the same time, the bridge is demolished section by section by cutting method, which is convenient for demolishing bridges of various sizes, making the method more applicable; at the same time, when dismantling the bridge, the bridge is cut by cutting equipment, and the cut bridge section is lifted and transferred in time by lifting equipment; the operation is simple, and there is no need to build a supporting device separately, thereby reducing the equipment time for building the supporting device and improving the efficiency of bridge demolition.

[0067] 2. This method is safe and reliable; through precise calculations and reasonable construction steps, it effectively reduces the safety risks during the demolition process and ensures the safety of construction workers and the surrounding environment.

[0068] 3. In addition, this method is environmentally friendly and energy-saving; it adopts the method of cutting, dismantling and lifting and crushing, which reduces noise and dust pollution, and at the same time avoids waste falling into the river and causing environmental pollution.

[0069] 4. The present invention improves the efficiency of demolition construction and shortens the construction period through reasonable segmentation and lifting schemes; it effectively improves the demolition efficiency of the bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a flowchart of the dismantling method of the present invention;

[0071] Figure 2 It is a schematic diagram of the structure of the protection component of the present invention;

[0072] Figure 3 It is a structural schematic diagram of the protective net of the present invention;

[0073] Figure 4 It is a structural schematic diagram of the mounting rod of the present invention;

[0074] Figure 5 It is a structural schematic diagram of the shock absorbing spring of the present invention.

[0075] In the figure: 1. protective net; 11. frame; 12. connecting block; 13. perforation; 14. pressure block; 2. mounting rod; 20. guide port; 21. threaded groove; 22. fixing edge; 23. fixing hole; 3. shock-absorbing spring; 31. guide rod; 32. end plate. DETAILED DESCRIPTION

[0076] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] The following is a further description with reference to the accompanying drawings and specific embodiments:

[0078] Example 1

[0079] like Figure 1 As shown, a method for dismantling an existing prestressed concrete bridge across a river is described, and the specific steps of the method are as follows:

[0080] S100. Conduct detailed inspection and evaluation of the bridge to determine the condition of the bridge structure and evaluate the difficulty of bridge demolition. At the same time, set up warning signs upstream and downstream of the river to ensure the safety of navigation and flood discharge during the demolition process. Organize professional and technical personnel to conduct comprehensive inspection and evaluation of the bridge, including the structural strength, stability, prestressed condition, etc. of the bridge. At the same time, collect relevant information such as the design drawings and construction materials of the bridge to provide a basis for the demolition construction. At the same time, coordinate with the river management department to ensure the safety of navigation and flood discharge during the demolition process. Prepare the equipment and materials required for the demolition construction, including cranes, hoists, cutting equipment, crushing equipment, etc. At the same time, debug and inspect the equipment to ensure that the equipment performs well.

[0081] S200, simulating the bridge demolition to determine the best segmented cutting and demolition plan, and determining the position of the first cutting point; when simulating the bridge demolition, the reasonable segment length of the bridge segment needs to be determined according to factors such as the span of the bridge, the structural strength and the capacity of the demolition equipment;

[0082] S300. Use professional equipment and technology to gradually release the prestress of the bridge. The internal stress of the bridge structure is adjusted, reducing the risk of structural instability caused by sudden demolition. During the release process, the release speed and force must be strictly controlled to avoid sudden damage to the bridge structure. Monitor the bridge after release to observe the deformation and structural changes of the bridge.

[0083] S400. According to the demolition plan of the bridge simulation, the bridge is cut from the position of the first cutting point, and the part to be cut and removed is lifted by the lifting equipment at the same time. After the cutting is completed, the lifting equipment is directly lifted to the designated position; before the bridge is cut into sections, a protective component must be installed below the cutting position to prevent some tools and equipment and bridge fragments from falling into the river. The protective component can also protect the staff. When cutting the bridge, the flatness and accuracy of the cutting at the bridge section must be ensured; during the bridge demolition construction process, the lifting power of the crane needs to be determined based on factors such as the weight of the demolished section, the lifting distance and the lifting speed;

[0084] S500. Use lifting equipment to lift the cut bridge demolition section onto the vehicle, and move the bridge demolition section to the crushing plant for crushing. During the lifting process, the lifting speed and angle must be strictly controlled to ensure safety. Use crushing equipment to crush the demolition section to separate the concrete and steel bars. The waste after crushing is classified and recycled, and the recyclable part is recycled and the non-recyclable part is properly disposed of.

[0085] S600. After all bridges are dismantled, clean the river channel and remove the waste that falls into the river channel during the bridge dismantling process to ensure that the navigation and flood discharge functions of the river channel are not affected. Use dredging ships, cranes and other equipment to lift the waste to the designated location for treatment. Inspect the river channel to ensure that the navigation and flood discharge functions of the river channel are not affected. At the same time, clean and level the original site of the dismantled bridge to prepare for subsequent engineering construction.

[0086] In step S100, the stability evaluation is:

[0087]

[0088] Where S is the stability evaluation value,

[0089] F a is the actual bearing capacity of the bridge,

[0090] F d is the design bearing capacity of the bridge,

[0091] D is the percentage of damage degree, which is estimated from the actual damage degree of the bridge;

[0092] A is the percentage of bridge aging.

[0093] The stability is measured by the stability evaluation value S. If S > 1, it indicates that the actual bearing capacity is higher than the design bearing capacity, the bridge is in a good state, with low damage and aging degrees, and is suitable for demolition operations; if 0.8 < S ≤ 1, it indicates that although the actual bearing capacity is close to or slightly lower than the design bearing capacity, it is still within an acceptable range, and the damage and aging degrees need to be carefully considered. Demolition operations can be carried out after taking additional safety measures; if 0.5 < S ≤ 0.8, it indicates that the actual bearing capacity is significantly lower than the design bearing capacity, or the damage and aging degrees are relatively high, and further evaluation and special safety measures are required to carry out demolition operations; if S ≤ 0.5, it indicates that the actual bearing capacity is much lower than the design bearing capacity, or the damage and aging degrees are extremely high, and the bridge may not be suitable for demolition operations, and the structural state needs to be re-evaluated or extreme safety measures need to be taken.

[0094] The demolition difficulty assessment is as follows:

[0095]

[0096] Among them, D n is the demolition difficulty index,

[0097] B is the bridge type,

[0098] C is the structural complexity,

[0099] E is the surrounding environment,

[0100] f is a function that comprehensively considers these factors,

[0101] λ is the weight coefficient,

[0102] W is the bridge width,

[0103] W max is the maximum allowable width.

[0104] The demolition difficulty index D n < 1 indicates that the demolition difficulty is low; 1 < D n < 3 indicates that the demolition difficulty is medium; 3 < D n < 5 indicates that the demolition difficulty is high; 5 < D n indicates that the demolition difficulty is extremely high.

[0105] The bridge type B is: ordinary beam bridge, B = 1; continuous beam bridge, B = 2; arch bridge, B = 3; cable-stayed bridge, B = 4; suspension bridge, B = 5. The structural complexity C is: low complexity, C = 1; medium complexity, C = 2; high complexity, C = 3. The surrounding environment E is: low impact, E = 1; medium impact, E = 2-3; high impact, E = 4-5.

[0106] In step S200, the starting position of the bridge is taken as the zero point, and the first cutting point is determined as:

[0107]

[0108] Among them, P1 is the first cutting point position,

[0109] H(x) is the cutting difficulty coefficient,

[0110] S(x) is the safety factor,

[0111] β is the center priority coefficient, and β ranges from 0 to 1.

[0112] The cutting difficulty coefficient H(x) is:

[0113] H(x)=w1·f 结构 (x)+w2·f 位置 (x)+w3·f 设备 (x);

[0114] Among them, w1, w2, and w3 are the weight coefficients of the structure, position, and equipment on the cutting difficulty.

[0115] f 结构 (x), f 位置 (x), f 设备 (x) are functions related to structure, position and equipment respectively.

[0116] The safety factor S(x) is:

[0117] S(x)=w4·f 稳定性 (x)+w5·f 人员 (x)+w6·f 设备 (x);

[0118] Among them, w4, w5, and w6 are the weight coefficients of the impact of stability, personnel, and equipment on safety.

[0119] f 稳定性 (x), f 人员 (x), f 设备 (x) are functions related to stability, personnel and equipment respectively.

[0120] The segment length is determined as follows:

[0121]

[0122] Among them, L s is the segment length,

[0123] L t is the total length of the bridge,

[0124] N is the number of segments,

[0125] L m is the maximum load-bearing length of the equipment,

[0126] α is the safety margin factor.

[0127] In step S300, the prestress release speed is:

[0128]

[0129] Among them, V r is the release speed,

[0130] P t is the total amount of prestress,

[0131] T is the release time,

[0132] D f is the percentage of deformation degree,

[0133] V d is the current deformation speed,

[0134] V max is the maximum allowable deformation speed.

[0135] In step S400, the lifting power of the crane is:

[0136]

[0137] P c is the lifting power,

[0138] W is the weight of the demolished section,

[0139] g is the acceleration due to gravity,

[0140] t is the lifting time,

[0141] γ is the lifting safety factor,

[0142] W max The maximum permissible lifting weight.

[0143] In step S500, the waste treatment amount is:

[0144]

[0145] Q w The amount of waste treated,

[0146] W c is the amount of concrete,

[0147] W s is the amount of steel bars,

[0148] R is the total amount of waste,

[0149] R r is the recovery rate,

[0150] R max is the maximum recovery rate,

[0151] μ is the recovery efficiency coefficient.

[0152] In step S600, the amount of waste cleaned is:

[0153]

[0154] Among them, Q c For the cleaning amount,

[0155] V i To represent the volume of the i-th waste,

[0156] n is the total amount of waste,

[0157] C p is the cleaned amount,

[0158] C max For maximum cleaning capacity,

[0159] v is the cleaning efficiency coefficient.

[0160] Example 2

[0161] like Figure 2 As shown, a protection assembly for bridge demolition is provided, the protection assembly includes a protection net 1, a mounting rod 2 and a shock-absorbing spring 3. The mounting rods 2 are symmetrically arranged on both sides of the rear end of the protection net 1, and the mounting rods 2 are sleeved on both sides of the rear end of the protection net 1. The mounting rods 2 are used to install the protection net 1, so as to facilitate fixing the protection net 1 below the bridge cutting position. Shock-absorbing springs 3 are arranged at the top and bottom ends of the inner side of the mounting rod 2, and the opposite ends of the two shock-absorbing springs 3 on the inner side of each mounting rod 2 are against the rear end of the protection net 1, which are used to buffer the protection net 1 when the protection net 1 is impacted, so as to play a buffering role when an object impacts the protection net 1, thereby effectively protecting the falling objects and preventing the objects from falling into the river.

[0162] like Figure 3As shown, a frame 11 is provided on the outside of the protective net 1, and the frame 11 facilitates sufficient stability of the protective net 1. The protective net 1 is provided with two layers up and down along the inside of the frame 11, and the mesh holes of the two layers of the protective net 1 are arranged in a staggered manner; this structure can achieve the effect of double-layer protection, so that the entire protective assembly has a more outstanding protection capability. Connecting blocks 12 are symmetrically provided on both sides of the rear end of the frame 11, and the connecting blocks 12 are convenient for cooperating with the mounting rod 2, so as to facilitate the stable connection between the mounting rod 2 and the protective net 1. A through hole 13 is provided in the middle of the connecting block 12, and the front end of the mounting rod 2 is passed through the through hole 13; a pressure block 14 is provided at the rear end of the connecting block 12, and the pressure block 14 is used to press the shock-absorbing spring 3 when the protective net 1 is impacted, so as to achieve the purpose of buffering falling objects.

[0163] like Figure 4 As shown, a guide opening 20 is longitudinally provided on the inner side of the mounting rod 2, and a threaded groove 21 is provided on the top and bottom of the inner side of the guide opening 20; the guide opening 20 is convenient for cooperating with the pressure block 14, and is convenient for the pressure block 14 to move up and down along the inner side of the guide opening 20. The threaded groove 21 is convenient for installing the shock absorbing spring 3, and is convenient for installing and using the shock absorbing spring 3. The guide opening 20 is convenient for guiding the protective net 1, and the rear ends of both sides of the mounting rod 2 are provided with fixed edges 22, and a plurality of fixing holes 23 are provided on the fixed edges 22 from top to bottom. The cooperation between the fixing plate and the fixing holes 23 is convenient for fixing the position of the mounting rod 2 by bolts, so as to ensure that the mounting rod 2 is stable at the designated position of the bridge.

[0164] like Figure 5 As shown, a guide rod 31 is provided inside the shock absorbing spring 3, and the guide rod 31 ensures that the shock absorbing spring 3 can only move elastically up and down, so as to facilitate buffering the impact force on the protective net 1. End plates 32 are provided at the top and bottom of the guide rod 31, and the two ends of the shock absorbing spring 3 are fixedly connected to the two end plates 32 respectively; this structure can ensure that the entire shock absorbing spring 3 has good stability.

[0165] Working principle: When in use, the mounting rod 2 is fixed below the cutting point of the bridge together with the protective net 1 and the shock-absorbing spring 3 through expansion bolts. When an object falls on the protective net 1, the protective net 1 will intercept the object, and the impact force of the object hitting the protective net 1 will drive the protective net 1 to move downward along the guide port 20. During the downward movement of the protective net 1, the shock-absorbing spring 3 will reduce the shock of the protective net 1, so that the impact force on the protective net 1 is buffered, thereby protecting both the falling objects and the protective net 1.

[0166] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for dismantling an existing prestressed concrete bridge across a river, characterized in that: The specific steps of this method are as follows: S100, conduct detailed inspection and assessment of the condition of the bridge, determine the condition of the bridge structure, and assess the difficulty of dismantling the bridge; S200, simulating and calculating the bridge demolition, thereby determining the best segmented cutting and demolition plan, and determining the position of the first cutting point; S300, using professional equipment and technology to gradually release the prestress of the bridge, the internal stress of the bridge structure is adjusted, reducing the risk of structural instability caused by sudden demolition; S400, according to the demolition plan calculated by simulating the bridge, the bridge is cut from the position of the first cutting point, and the part to be cut and removed is lifted by the lifting equipment during the cutting, and after the cutting is completed, the part is directly lifted to the designated position by the lifting equipment; when cutting the bridge, the smoothness and accuracy of the cutting at the bridge segment should be ensured; S500, lifting the cut bridge demolition section onto a vehicle using a lifting device, and moving the bridge demolition section to a crushing plant for crushing; During the lifting process, the lifting speed and angle must be strictly controlled to ensure safety; S600. After all bridges are dismantled, the river channel shall be cleaned up to remove the waste that fell into the river channel during the dismantling of the bridges, so as to ensure that the navigation and flood discharge functions of the river channel are not affected.

2. The method for dismantling an existing prestressed concrete bridge across a river according to claim 1, characterized in that: In step S100, the stability evaluation is: Where S is the stability evaluation value, F a is the actual bearing capacity of the bridge, F d is the design bearing capacity of the bridge, D is the percentage of damage degree, which is estimated from the actual damage degree of the bridge; A is the percentage of bridge aging degree; The demolition difficulty is assessed as follows: Among them, D n is the demolition difficulty index, B is the bridge type, C is the structural complexity, E is the surrounding environment, f is a function that comprehensively considers these factors. λ is the weight coefficient, W is the width of the bridge, W max is the maximum allowed width.

3. The method for dismantling an existing prestressed concrete bridge across a river according to claim 1, characterized in that: In step S200, the starting position of the bridge is taken as the zero point, and the first cutting point is determined as: Among them, P1 is the first cutting point position, H(x) is the cutting difficulty coefficient, S(x) is the safety factor, β is the center priority coefficient, β ranges from 0 to 1; Determine the segment length as: Among them, L s is the segment length, L t is the total length of the bridge, N is the number of segments, L m is the maximum load-bearing length of the equipment, α is the safety margin factor.

4. The method for dismantling an existing prestressed concrete bridge across a river according to claim 1, characterized in that: In step S300, the prestress release speed is: Among them, V r is the release speed, P t is the total amount of prestress, T is the release time, D f is the percentage of deformation degree, V d is the current deformation speed, V max is the maximum allowable deformation speed.

5. The method for dismantling an existing prestressed concrete bridge across a river according to claim 1, characterized in that: In step S400, the lifting power of the crane is: P c is the lifting power, W is the weight of the demolished section, g is the acceleration due to gravity, t is the lifting time, γ is the lifting safety factor, W max The maximum permissible lifting weight.

6. The method for dismantling an existing prestressed concrete bridge across a river according to claim 5, characterized in that: In step S400, before cutting the bridge into sections, a protective component is installed below the cutting position to prevent some tools and equipment as well as bridge fragments from falling into the river. The protective component can also protect the workers.

7. The method for dismantling an existing prestressed concrete bridge across a river according to claim 6, characterized in that: The protection component comprises a protection net (1), a mounting rod (2) and a shock-absorbing spring (3); the mounting rods (2) are symmetrically arranged on both sides of the rear end of the protection net (1); the mounting rods (2) are sleeved on both sides of the rear end of the protection net (1); shock-absorbing springs (3) are arranged at the top and bottom ends of the inner sides of the mounting rods (2); and the opposite ends of the two shock-absorbing springs (3) on the inner side of each mounting rod (2) are both against the rear end of the protection net (1), so as to buffer the protection net (1) when the protection net (1) is impacted.

8. The method for dismantling an existing prestressed concrete bridge across a river according to claim 7, characterized in that: The protective net (1) is provided with a frame (11) on the outside, and the protective net (1) is provided with two layers up and down along the inside of the frame (11), and the mesh holes of the two layers of the protective net (1) are arranged in a staggered manner; connecting blocks (12) are symmetrically provided on both sides of the rear end of the frame (11), and a through hole (13) is provided in the middle of the connecting block (12) for the front end of the mounting rod (2) to pass through the through hole (13); a pressure block (14) is provided at the rear end of the connecting block (12), and the pressure block (14) is used to apply pressure to the shock-absorbing spring (3) when the protective net (1) is impacted, thereby achieving the purpose of buffering falling objects.

9. The method for dismantling an existing prestressed concrete bridge across a river according to claim 7, characterized in that: A guide opening (20) is longitudinally provided on the inner side of the installation rod (2), and a thread groove (21) is provided at the top and bottom of the inner side of the guide opening (20); and fixed edges (22) are provided at the rear ends of both sides of the installation rod (2), and a plurality of fixing holes (23) are provided on the fixed edges (22) from top to bottom.

10. The method for dismantling an existing prestressed concrete bridge across a river according to claim 7, characterized in that: A guide rod (31) is provided inside the shock absorbing spring (3), and end plates (32) are provided at the top and bottom ends of the guide rod (31). Both ends of the shock absorbing spring (3) are fixedly connected to the two end plates (32) respectively.

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