A construction method for demolishing cast-in-situ beam segments using a hanging basket

Abstract

The present invention relates to the field of the demolition method of beam segments, and particularly relates to a construction method for demolishing cast-in-place beam segments using a hanging basket. A construction method for demolishing cast-in-place beam segments using a hanging basket includes the following steps: setting a first track pressing beam and a second track pressing beam and connecting track steel bars, relaxing the bottom formwork, setting cushion blocks and tightening the bottom formwork, disconnecting the connection between the second track pressing beam member and the connecting member, and demolishing the beam segment to be demolished. Compared with the prior art of directly arranging a support method outside the beam segment to be demolished, in this construction method, through the conversion of the load-bearing members of the beam segment to be demolished from the bottom formwork of the hanging basket to the track steel bars and then back to the bottom formwork of the hanging basket, during the subsequent demolition process, the hanging basket used during the construction period still bears the load of the beam segment to be demolished, and there is no need to arrange another support or additionally tension prestress to reduce the negative moment of the top slab of the beam segment to be demolished, reducing the material resources consumed by arranging another support.

Description

Technical Field

[0001] The present invention relates to the field of demolition methods for beam segments, and particularly to a construction method for demolishing cast-in-place beam segments using a hanging basket. Background Art

[0002] The cantilever cast-in-place beam technology is an important construction technology in bridge construction and is widely used in the construction of medium-span bridges. If there are quality problems with the cantilever cast-in-place beam, it is necessary to demolish its beam segments.

[0003] Before demolishing the beam segments of the cantilever cast-in-place beam in the prior art, additional support methods such as erecting steel pipe columns, floor brackets, pre-hoisting with a bridge erection machine, and steel pipe piles are used to apply vertical support. During the demolition process, methods such as wire saw cutting, mechanical breaking, and blasting breaking are directly used to demolish the beam segments. After the demolition is completed, methods such as slides, tower cranes, and cranes are used to transport the concrete fragments.

[0004] However, in the prior art, when using additional support methods such as erecting steel pipe columns, floor brackets, pre-hoisting with a bridge erection machine, steel pipe piles, and tensioning prestress to apply vertical support, a large amount of physical resources need to be consumed additionally. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that when using additional support methods such as erecting steel pipe columns, floor brackets, pre-hoisting with a bridge erection machine, steel pipe piles, and tensioning prestress to apply vertical support, a large amount of physical resources need to be consumed additionally, and to provide a construction method for demolishing cast-in-place beam segments using a hanging basket.

[0006] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] A construction method for demolishing cast-in-place beam segments using a hanging basket, comprising the following steps:

[0008] S1. Conversion of load-bearing members:

[0009] S101. Connect a first track pressing beam member to the track steel bars embedded in the top surface of the beam segment to be demolished, and set a second track pressing beam member corresponding to the first track pressing beam member on the top of the hanging basket longitudinal beam. The first track pressing beam member and the second track pressing beam member are fixed through a connecting member, so that the hanging basket longitudinal beam forms a hanging on the beam segment to be demolished;

[0010] S102. Relax the bottom formwork of the hanging basket to disengage it from the lower surface of the beam segment to be demolished;

[0011] S103. Fix a cushion block on the bottom formwork of the hanging basket, and tighten the bottom formwork of the hanging basket upward until the cushion block abuts against the lower surface of the beam segment to be demolished;

[0012] S104. Disconnect the connection between the second track pressing beam member and the connecting member;

[0013] S2. Demolish the beam segment to be demolished: The beam segment to be demolished is demolished in sections and blocks, and the demolished concrete blocks are hoisted to the corresponding positions.

[0014] When the beam segment to be demolished is demolished in sections and blocks in step S2, the specific demarcation line is determined according to the actual situation. Preparatory work is also included before step S1. The longitudinal beam of the hanging basket refers to the beam of the main truss of the hanging basket along the bridge direction. The track steel bars are the fine-threaded deformed steel bars used to fix the traveling tracks of the hanging basket. After determining the positions of the traveling tracks of the hanging basket, the track steel bars are embedded at their corresponding positions. The first track pressing beam member is below the longitudinal beam of the hanging basket and also in front of the hanging basket track. Here, the front is the direction from the existing beam segment to the beam segment to be demolished. The second track connecting member is at the top of the longitudinal beam of the hanging basket. When the longitudinal beam of the hanging basket lifts and hangs the beam segment to be demolished, the connecting member and the track steel bars play the role of lifting and hanging. The bottom formwork of the hanging basket is the support at the lower part during the casting of the beam segment.

[0015] Step S1 completes the conversion of the load-bearing member of the beam segment to be demolished from the bottom formwork of the hanging basket to the track steel bars and then back to the bottom formwork of the hanging basket. In step S101, the first track pressing beam member fixes one end of the track steel bar protruding from the upper surface of the beam segment to be demolished, so that the beam segment to be demolished is converted from being supported at the bottom to being lifted at the top, minimizing the negative moment on the upper surface of the beam segment to be demolished as much as possible. The first track pressing beam member and the second track pressing beam member are fixed through the connecting member, so that the connecting member bears the load of the beam segment to be demolished. The bottom formwork of the hanging basket is separated from the lower surface of the beam segment to be demolished. The longitudinal beam of the hanging basket lifts and hangs the beam segment to be demolished, and a cushion block is set on one side of the bottom formwork of the hanging basket facing the lower surface of the demolished beam segment. The bottom formwork of the hanging basket is tightened upward until the cushion block abuts against the lower surface of the beam segment to be demolished, and then the connection between the second track pressing beam member and the connecting member is released, so that the bottom formwork of the hanging basket bears the load of the beam segment to be demolished. Through the conversion of the load-bearing member of the beam segment to be demolished from the bottom formwork of the hanging basket to the track steel bars and then back to the bottom formwork of the hanging basket, the situation of directly relaxing the bottom formwork of the hanging basket and making the beam segment to be demolished in a cantilever state is avoided. In the cantilever state, the negative moment on the top surface of the beam segment to be demolished is too large, which is likely to have a negative impact on the existing segments. Setting a cushion block on the bottom formwork of the hanging basket and the cushion block abuts against the lower surface of the beam segment to be demolished. Compared with the beam segment to be demolished directly contacting the bottom formwork of the hanging basket, there is a gap between the lower surface of the beam segment to be demolished and the bottom formwork of the hanging basket, which is convenient for subsequent demolition and hoisting of the beam segment to be demolished. In step S2, it is demolished in sections and blocks to minimize the potential safety hazards caused by overall demolition.

[0016] Compared with the prior art which directly sets up additional supports outside the beam segment to be demolished, this construction method sets up the first track pressing beam member, the second track pressing beam member and the cushion block, enabling the load-bearing member of the beam segment to be demolished to be converted from the hanging basket bottom formwork to the track steel bars and then back to the hanging basket bottom formwork. This avoids the situation where the beam segment to be demolished becomes a cantilever after the hanging basket bottom formwork is loosened, thus avoiding the excessive negative bending moment on the upper part of the beam segment to be demolished and minimizing the probability of damaging the prestressed tendons of the existing beam segment as much as possible. Compared with the prior art which reduces the negative bending moment of the top plate of the beam segment to be demolished by setting up additional supports or additionally tensioning prestress, this construction method directly uses the hanging basket used during construction, reducing the material resources consumed by setting up additional supports. In addition, in step S2, segmented and block-by-block demolition is carried out to minimize the potential safety hazards caused by overall demolition.

[0017] Preferably, when cutting the beam body of the beam segment to be demolished in step S2, the demolition is carried out by a method combining wire saw cutting and manual breaking.

[0018] The position of the manual breaking section is close to the interface between the beam segment to be demolished and the existing beam segment, and the interface between the wire saw cutting and the manual drilling cutting is determined according to the actual situation. Wire saw cutting is carried out first in the front section, and the cutting sequence is determined according to the actual situation, which is convenient for operation and safe and reliable. Manual breaking is carried out in the rear section, which can ensure that the cross-section condition of the interface between the beam segment to be demolished and the existing beam segment is good, the quality of the steel bars and the reserved amount of the steel bars are sufficient, thus effectively ensuring the subsequent construction quality.

[0019] Preferably, when manually breaking the top plate and the web of the beam segment to be demolished in step S2, a false seam is circumferentially cut in the inner and outer rings of the box chamber of the beam segment to be demolished first, and then the top plate and the web are broken from top to bottom respectively.

[0020] The false seam is a non-penetrating seam, that is, the depth of the false seam is less than the depth of the beam segment to be cut. The depth of the false seam is determined according to the actual situation. By using the method of cutting the false seam and then processing, the interface between the beam segment to be demolished and the existing beam segment and the reserved steel bars can be avoided being damaged as much as possible.

[0021] Preferably, the static crushing method is adopted when manually drilling and demolishing the bottom plate in step S2.

[0022] Adopting the static crushing method means that the expansive agent is put into the body of the beam segment to be demolished in advance at an appropriate time, and the expansive force generated by the expansive agent slowly acts on the hole wall and reaches 300 - 500 MPa after several hours to 24 hours, causing the beam segment to be demolished to crack. By adopting the static crushing method, the damage to the existing beam segment is minimized as much as possible, and it is safe and reliable.

[0023] Preferably, before step S1, it includes removing the end steel bars of the beam segment to be demolished, and the end steel bars are used to connect the next beam segment.

[0024] Remove the end reinforcement of the beam segment to avoid damage during removal, so as not to damage the prestressed steel tendons of the existing beam segment.

[0025] Preferably, before step S1, sectional design and block design are carried out on the beam segment to be demolished. In the case where there is no available lifting hole in the concrete block divided by the design, drilling treatment is carried out on the concrete block.

[0026] The size of the lifting hole is adapted to the size of the tower crane sling.

[0027] Preferably, in step S103, the cushion block is an I-beam.

[0028] I-beams are common on construction sites, easy to obtain and do not require additional search for other materials, which minimizes the additional mobilization of material resources and saves the construction period. The corresponding length of the disconnected I-beam facilitates the subsequent lifting of the demolished concrete block.

[0029] Preferably, in step S102, first loosen the front hanger rod of the main truss of the hanging basket, then loosen the rear anchor rod of the bottom formwork of the hanging basket, and regularly detect the falling amount of the hanging basket during the falling process.

[0030] The time interval of detection is determined according to the specific situation. Loosen the front hanger rod of the main truss of the hanging basket first and confirm that there is no problem, and then loosen the rear anchor rod of the bottom formwork of the hanging basket to improve safety.

[0031] Preferably, in step S2, when demolishing the beam segment to be demolished, a support is set inside its box. The height of the support changes with the remaining height of the beam segment to be demolished, and the support is used to place the instruments for demolishing the beam segment to be demolished.

[0032] The height of the support changes with the remaining height of the beam segment to be demolished, which is convenient for internal construction.

[0033] Preferably, in step S2, the demolished concrete block is hoisted by a tower crane onto a flatbed truck on the ground, and the flatbed truck is used to transport the demolished concrete block.

[0034] Through the cooperation of the tower crane and the flatbed truck, the demolished concrete block is transported out of the construction site. Compared with the existing technology using the slideway transportation method, the transportation using the tower crane and the flatbed truck requires less space on the site, is easy to operate and has high transportation efficiency, thus improving the transportation convenience.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. Compared with the existing technology of directly setting up additional supports outside the beam segment to be demolished, this construction method sets up the first track pressing beam member, the second track pressing beam member and the cushion block, enabling the load-bearing member of the beam segment to be demolished to be converted from the hanging basket bottom formwork to the track steel bars and then back to the hanging basket bottom formwork. This avoids the situation where the beam segment to be demolished becomes a cantilever after loosening the hanging basket bottom formwork, thus avoiding the excessive negative bending moment at the upper part of the beam segment to be demolished and minimizing the probability of damaging the prestressed tendons of the existing beam segments as much as possible. Compared with the existing technology of reducing the negative bending moment of the top slab of the beam segment to be demolished by setting up additional supports or extra tensioning of prestress, this construction method directly uses the hanging basket used during construction, reducing the material resources consumed by setting up additional supports. In addition, during the preliminary preparation for the conversion of the load-bearing member, the longitudinal extended steel bars of the beam segment to be demolished have been removed, avoiding damaging the prestressed tendons of the existing segments as much as possible. Using a wire saw for cutting is easy to operate, safe and reliable. For the part close to the existing beam segment, the static crushing method is used for manual demolition, minimizing the damage to the interface between the beam segment to be demolished and the existing beam segments, thus ensuring the subsequent construction quality. Moreover, the static crushing method generates less noise and vibration, effectively reducing the interference to the surrounding environment of the construction site. During the demolition process, the demolished concrete is directly lifted by a tower crane onto a flatbed truck, and then the flatbed truck transports it out of the construction site. This transportation method requires less space at the construction site, is easy to operate and has high transportation efficiency, improving the transportation convenience. Description of the Drawings

[0037] Figure 1 It is a flow chart of a construction method for demolishing a cast-in-place beam segment using a hanging basket as described in Example 1;

[0038] Figure 2 It is a longitudinal bridge direction schematic diagram of the beam segment to be demolished during preliminary preparation in Example 1;

[0039] Figure 3 It is a longitudinal bridge direction schematic diagram of the beam segment to be demolished divided by blocks in Example 1;

[0040] Figure 4 It is a longitudinal bridge direction layout schematic diagram of the beam segment to be demolished before demolition in Example 1;

[0041] Figure 5 For Figure 4 The enlarged view at location A in

[0042] Figure 6 It is a transverse bridge direction schematic diagram of the hanging basket longitudinal beam hanging in Example 1;

[0043] Figure 7 It is a longitudinal bridge direction schematic diagram of demolishing the beam segment to be demolished in Example 1.

[0044] Markings in the figure: 101 - First track pressing beam member, 102 - Second track pressing beam member, 2 - Connecting member, 3 - Track steel bars, 4 - Wire saw machine, 5 - Hoist, 6 - Cushion block, 7 - Tower crane sling, 8 - Ladder, 16 - Hanging basket bottom formwork, 17 - Support, 20 - Hanging basket longitudinal beam, 21 - Diamond wire, 22 - Rear anchor of bottom formwork. Detailed implementation manners

[0045] The present invention will be further described in detail below in combination with test examples and specific implementation manners. However, it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0046] Embodiment 1

[0047] As Figure 1 shown, a construction method for demolishing a cast-in-place beam segment using a hanging basket includes the following steps:

[0048] S1. Preliminary preparation, as Figure 2 shown:

[0049] S101. Cut the end steel bars: Cut the longitudinal extension steel bars reserved at the end of the beam segment to be demolished for the next segment, to provide a larger working surface for subsequent construction, and set up ladders 8 for entry and exit at the front and back of the beam segment to be demolished;

[0050] S102. Demolish the inner formwork of the beam segment to be demolished and hoist it to the ground for storage. The outer formwork of the box girder is separated from the concrete surface, and the separation distance is sufficient for workers to enter and exit. The outer formwork of the box girder does not need to be hoisted to the ground for storage;

[0051] S103. Mark and lay out in the inner and outer sides of the web of the beam segment to be demolished, use a chalk line to mark the longitudinal and transverse dividing lines for cutting, and use a marker pen to draw the cutting direction and sequence of the diamond wire 21 of the wire saw machine 4 along the longitudinal and transverse dividing lines for cutting, and divide the beam segment to be demolished by section and by block. As Figure 3 shown, draw the exact position of the prestressed steel bundle on the adjacent existing beam segment, and avoid the end anchor position of the prestressed steel bundle when demolishing the beam segment to be demolished. If there is no concrete block with a lifting hole available on site, a lifting hole needs to be drilled. The diameter of the lifting hole is adapted to the diameter of the diamond wire 21. In this embodiment, the diameter is 10 cm and a water mill drill is used;

[0052] S104. Count relevant materials and check electrical facilities;

[0053] S2. Conversion of load-bearing members:

[0054] S201, connect the first rail pressure beam 101 to the rail reinforcement 3 embedded in the top surface of the beam section to be removed, and set the second rail pressure beam 102 on the top of the basket longitudinal beam 20 corresponding to the first rail pressure beam 101. In this embodiment, the first rail pressure beam 101 and the second rail pressure beam 102 are directly opposite to each other, and the first rail pressure beam 101 and the second rail pressure beam 102 are fixed by the connecting member 2, so that the basket longitudinal beam 20 is lifted and hung on the beam section to be removed. In this embodiment, the connecting member 2 is two fine-rolled threaded steel bars, and one fine-rolled threaded steel bar is provided on each side of the basket longitudinal beam. Figure 5 As shown;

[0055] S202, loosen the bottom formwork 16 of the hanging basket to separate it from the lower surface of the beam section to be removed. During the loosening process, first loosen the front suspension rod of the main truss of the hanging basket and observe and confirm that there is no problem before loosening the rear anchor rod 22 of the bottom formwork of the hanging basket. In step 203, after the rear anchor rod 22 of the bottom formwork is loosened, the first drop amount of the bottom formwork 16 of the hanging basket shall not be greater than the preset value. In this embodiment, the preset value is 1 cm. During the subsequent falling process, the drop amount is regularly monitored at a frequency of once an hour. Figure 6 As shown;

[0056] S203, a cushion block 6 is fixedly set on the hanging basket bottom formwork 16, and the hanging basket bottom formwork 16 is tightened upward until the cushion block 6 abuts against the lower surface of the beam section to be removed. The cushion block 6 used in this embodiment is an I18 I-beam, and the cushion block 6 needs to be disconnected at the place where the hoisting hole is set in the concrete block. In this embodiment, the I-beam is disconnected at a predetermined position by 30 cm, and then φ12 steel bars are used to connect the I-beam along the lower flange plate direction of the I-beam to form a whole. The I-beam and the hanging basket bottom formwork 16 are connected by spot welding, such as Figure 4 As shown;

[0057] S204, releasing the connection between the second rail pressure beam 102 and the connecting member 2;

[0058] S3, dismantling the beam section to be dismantled: the beam section to be dismantled is dismantled in blocks, the front section is cut by rope saw, and the rear section is broken manually. In this embodiment, the 2.2m section away from the existing beam section is cut by rope saw, and the 0.8m section close to the existing beam section is broken manually. During the dismantling process, the height of the disc-shaped bracket 17 inside the beam section to be dismantled changes with the remaining height of the beam section to be dismantled, such as Figure 7 As shown, the demolished concrete blocks are hoisted by a tower crane to a flatbed truck on the ground. The flatbed truck is used to transport the demolished concrete blocks. The steps are as follows:

[0059] S301. Demolish in the order from top to bottom, from outside to inside and with left-right balance. When demolishing the top slab of the beam segment to be demolished, place the wire saw 4 on the existing beam segment. When demolishing the web and bottom slab of the beam segment to be demolished, place the wire saw 4 on the bracket 17. Under the condition that the tower crane sling 7 hoists and the hoist 5 pulls the concrete block to be cut, cut the concrete block to be cut in a certain order. For the top slab and web, cut longitudinally along the bridge direction first and then transversely along the bridge direction. For the bottom slab concrete, cut transversely along the bridge direction first and then longitudinally along the bridge direction. The cut concrete blocks are transported to the flatbed truck by the tower crane. When hoisting, set 20-mm nylon steady ropes at both left and right ends as required. The steady ropes are strictly prohibited from being hung on the lifting chain;

[0060] S302. When cutting the remaining 0.8 m of the top slab and web, first use a grinding wheel to cut a false joint with a depth of 2 - 3 cm circumferentially in the inner and outer rings of the box chamber, and then use a combination of manual labor and pneumatic pick to break the concrete at the top slab and web from top to bottom at one time. When breaking, avoid the position of the prestressed steel bundle of the existing beam segment, and keep the length of the extended steel bar not less than 80 cm;

[0061] S303. Demolish the remaining 0.8 m of the bottom slab: Use the static crushing method to split the concrete of the bottom slab. Drill horizontal holes along the bridge direction 24 h in advance and pour static blasting agent. The axis of the hole is perpendicular to the axis of this section, and the longitudinal and transverse spacing between the holes is not greater than 25 cm. When demolishing, keep the length of the extended steel bar not less than 80 cm.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, 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 construction method for demolishing cast-in-place beam segments using a hanging basket, characterized in that, The steps include: S1. Conversion of load-bearing components: S101. Connecting a first rail pressure beam member (101) to a rail reinforcement (3) pre-embedded on the top surface of the beam section to be removed, and arranging a second rail pressure beam member (102) on the top of the hanging basket longitudinal beam (20) corresponding to the first rail pressure beam member (101), and fixing the first rail pressure beam member (101) and the second rail pressure beam member (102) via a connecting member (2), so that the hanging basket longitudinal beam (20) can lift and hang the beam section to be removed; S102. Loosen the bottom mold (16) of the hanging basket to separate it from the lower surface of the beam segment to be removed; S103. A cushion block (6) is fixedly arranged on the bottom mold (16) of the hanging basket, and the bottom mold (16) of the hanging basket is tightened upward until the cushion block (6) abuts against the lower surface of the beam section to be removed; S104. Release the connection between the second rail pressure beam member (102) and the connecting member (2), so that the bottom mold (16) of the hanging basket bears the load of the beam section to be removed; S2. Removal of the beam segment to be removed: the beam segment to be removed is removed in sections and blocks, and the removed concrete blocks are hoisted to the corresponding positions; Wherein, when removing the beam section to be removed in step S2, a bracket (17) is arranged in the box thereof, the height of the bracket (17) varies with the remaining height of the beam section to be removed, and the bracket (17) is used to place equipment for removing the beam section to be removed.

2. The construction method for demolishing a cast-in-place beam segment using a hanging basket according to claim 1, characterized in that, When cutting the beam body of the beam section to be removed in step S2, removal is performed by combining wire saw cutting and manual breaking.

3. A construction method for demolishing a cast-in-place beam section using a hanging basket according to claim 2, characterized in that, When manually breaking the top plate and the web of the beam section to be removed in step S2, a false seam is first cut circumferentially inside and outside the box chamber of the beam section to be removed, and then the top plate and the web are broken from top to bottom respectively.

4. The construction method for demolishing the cast-in-place beam section using a hanging basket according to claim 2, wherein, In step S2, a static crushing method is used when removing the bottom plate by manual drilling.

5. A construction method for demolishing a cast-in-place beam segment using a hanging basket according to claim 1, characterized in that, The process before step S1 includes removing the end steel bars of the beam section to be removed, wherein the end steel bars are used to connect the next beam section.

6. A construction method for demolishing a cast-in-place beam segment using a hanging basket according to claim 1, characterized in that, The process before step S1 includes segmental design and block design of the beam section to be removed. When there are no available lifting holes in the concrete blocks divided by the design, the concrete blocks are drilled.

7. A construction method for demolishing a cast-in-place beam segment using a hanging basket according to claim 1, characterized in that, The cushion block (6) in step S103 is an I-beam.

8. A construction method for demolishing the cast-in-place beam segments using a hanging basket according to any one of claims 1-7, characterized in that, In step S102, the front suspension rod of the main truss of the hanging basket is loosened first, and then the rear anchor rod of the bottom mold of the hanging basket is loosened. The falling amount of the hanging basket is regularly detected during the falling process.

9. A construction method for demolishing a cast-in-place beam segment using a hanging basket according to any one of claims 1-7, characterized in that The removed concrete blocks in step S2 are hoisted by a tower crane onto a flatbed truck on the ground, and the flatbed truck is used to transport the removed concrete blocks.

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