A method for dismantling cast-in-place box girders

Abstract

This invention discloses a method for dismantling a cast-in-place box girder, comprising the following steps: dividing the box girder into upper and lower parts by a virtual plane passing through the web of the box girder, and arranging several steel support structures supporting the lower end of the box girder along the longitudinal direction of the box girder; cutting a first vertical section from the top of the box girder downwards to the virtual plane using a wire saw; after the box girder stabilizes under load, continuing to cut a longitudinal section along the longitudinal direction of the box girder using a wire saw; after the box girder stabilizes under load, continuing to cut downwards to the second vertical section penetrating the box girder using a wire saw; cutting and separating segments from the box girder using the cutting method of step two, and lifting the segments away from the box girder; then repeating the aforementioned steps until the box girder is cut and lifted away segment by segment along the longitudinal direction of the box girder; the cast-in-place box girder dismantling method of this invention utilizes the lower half of the web as a temporary load-bearing base when dismantling the upper half of the structure, which can significantly reduce the amount of temporary steel support structures used, reduce project costs and shorten the construction period, and improve dismantling efficiency.

Description

Technical Field

[0001] This invention relates to the field of box girder demolition construction, and more specifically, to a method for demolishing cast-in-place box girders. Background Technology

[0002] Currently, the industry commonly employs a segmented dismantling process along the cross-section of the bridge span for the demolition of cast-in-place box girders. The core logic of this conventional process is to cut the entire box girder into several independent dismantling segments along the transverse cross-section of the bridge. Each independent segment is then fully supported by a full-span steel pipe scaffold or a high-density temporary steel pipe support system. After the support system passes inspection, the segments are hoisted, removed, and dismantled, thus ensuring the structural stability of the girder during construction. However, this cutting and dismantling process has the following drawbacks: First, cutting the beam in one go with the entire cross section will cause the load to be released instantly and the stress system to change abruptly. The temporary support system needs to bear all the concentrated load instantly, which is very easy to cause problems such as uneven local support stress, overload instability, settlement and deformation. At the same time, large-section cutting is prone to causing stress concentration in concrete and slight swaying of the beam. It is easy to cause tensile and cracking damage to adjacent beams that have not been demolished and retained, destroying the integrity of the original structure and posing a great safety hazard.

[0003] Second, using the cross-sectional integral cutting method will cause the cut box girder segments to be completely separated from the original main structure, with the entire load suspended in the air and without the support of the original structure. In order to prevent the risk of the beam overturning and falling, it is necessary to erect a full-coverage scaffold or dense steel pipe temporary support under each segment to be removed. However, for large-span, heavy cast-in-place box girders, the amount of support erection work is huge, and the costs of steel rental, manual erection and subsequent dismantling and cleanup are extremely high, which greatly increases the investment in project construction. Therefore, it will lead to problems such as large investment in temporary support system, high project cost, complicated construction procedures, long construction period and high site adaptability requirements, which makes this construction technology extremely limited. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings mentioned in the background art and provide a method for dismantling cast-in-place box girders.

[0005] The objective of this invention is achieved through the following technical solutions: A method for dismantling cast-in-place box girders includes the following steps: Step 1: Divide the box girder into upper and lower parts by a virtual plane passing through the web of the box girder, and arrange several steel support structures supporting the lower end of the box girder along the longitudinal direction of the box girder; Step 2: Use a wire saw to cut a first vertical section from the top of the box girder down to the virtual plane; after the box girder is under stable load, use the wire saw to continue cutting a longitudinal section along the box girder; after the box girder is under stable load, use the wire saw to continue cutting down to a second vertical section that penetrates the box girder. Step 3: Cut and separate the segments from the box girder using the cutting method described in Step 2, and then lift the segments away from the box girder; Step 4: Repeat steps 3 to 4 until the box girder is cut off and lifted off segment by segment along its longitudinal direction.

[0006] The method for dismantling cast-in-place box girders of the present invention has at least the following beneficial effects: By setting a virtual plane on the web of the box girder, the web and the box girder as a whole are vertically divided into upper and lower layers. During the cutting of the upper half, the uncut lower half of the web and box girder are used as a temporary load-bearing base for dismantling the upper half of the structure, so as to realize the self-support of the box girder structure. This can significantly reduce the amount of temporary steel support structure, eliminate the layout of full-span scaffolding from the root, and avoid problems such as large investment in temporary support system, high project cost, complicated construction procedures, long construction period and high site adaptability requirements.

[0007] Meanwhile, the three-section cutting method of first vertical section, longitudinal section and second vertical section is adopted to avoid instantaneous release of body load and sudden change of force system. At the same time, the three-section cutting can avoid the formation of large section and cause stress concentration in concrete, avoid beam swaying, and avoid the cut part causing tensile and cracking damage to adjacent unremoved beams, thus avoiding damage to the original structural integrity.

[0008] Further, in step one, the box girder is divided into several supporting segments and several suspended segments arranged alternately along the longitudinal direction of the box girder, wherein each group of supporting segments is supported by a group of steel support structures or bridge piers. In steps two through four, in any two adjacent separations, the two sets of segments separated are... One group consists of the supporting sections and the other group consists of the suspended sections.

[0009] With the above setup, only one set of the aforementioned steel support structure can be installed between every two sets of piers / abutments of the box girder, which can significantly reduce the arrangement of temporary steel support systems.

[0010] Furthermore, in steps two to three, the segment that is first cut and separated is the suspended segment.

[0011] Furthermore, in steps two and three, the segment that is first cut and separated is the suspended segment located in the middle of the box girder; In step four, the box girder is cut off section by section from the middle to both ends and lifted away.

[0012] With the above setup, when cutting the suspended section in the middle of the box girder for the first time, construction can proceed simultaneously from the middle of the box girder to both ends in subsequent processes, greatly improving the efficiency of box girder demolition.

[0013] Furthermore, in each cut and separation, the first vertical cross-section at both ends of the suspended segment protrudes beyond the second vertical cross-section at the same end.

[0014] With the above setup, both ends of the suspended section can be supported and held by the support section during the initial cutting and separation of the suspended section, further improving the safety of the demolition construction.

[0015] Furthermore, before step two, the wire saw's path is marked on the box girder to facilitate accurate cutting based on the markings.

[0016] Furthermore, in step two, the cutting length of the longitudinal section is 1.2m to 1.5m, which can be adaptively adjusted according to the lifting capacity of the lifting equipment.

[0017] Furthermore, the virtual plane is parallel to the top surface of the box girder.

[0018] Furthermore, in step one, several of the steel support structures and several of the bridge piers are arranged alternately along the longitudinal direction of the box girder.

[0019] Furthermore, the steel support structure includes a concrete base poured into the ground and several steel pipe columns installed on the upper end of the concrete base, which ensures the support capacity of the temporary support system while facilitating installation and disassembly. Attached Figure Description

[0020] Figure 1 The working principle of the cast-in-place box girder demolition method provided in the embodiments of the present invention Figure 1 ; Figure 2 The working principle of the cast-in-place box girder demolition method provided in the embodiments of the present invention Figure 2 ; Figure 3 This is a schematic diagram of the cantilevered section of the box girder provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the box girder support section structure provided in an embodiment of the present invention; The attached diagram lists the components represented by each number as follows: 1. Box girder; 10. Suspended section; 100. First vertical section; 101. Longitudinal section; 102. Second vertical section; 11. Support section; 2. Steel support structure; 20. Steel pipe column; 21. Concrete base; 3. Bridge pier; a. Virtual plane. Detailed Implementation

[0021] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0022] Reference Figures 1 to 4 This invention provides a method for dismantling a cast-in-place box girder 1, comprising the following steps: Step 1: First, the box girder 1 is divided into upper and lower parts by a virtual plane a through the web of the box girder 1, and several steel support structures 2 supporting the lower end of the box girder 1 are arranged along the longitudinal direction of the box girder 1. Step 2: Use a wire saw to cut the first vertical section 100 from the top of the box girder 1 down to the virtual plane; after the box girder 1 is stable under load, use the wire saw to continue cutting the longitudinal section 101 along the box girder 1; after the box girder 1 is stable under load, use the wire saw to continue cutting down to the second vertical section 102 that penetrates the box girder 1. Step 3: Cut and separate the segments from box girder 1 using the cutting method described in Step 2, and lift the segments away from box girder 1; Step 4: Repeat steps 3 to 4 until box girder 1 is cut off segment by segment along its longitudinal direction and lifted away.

[0023] The cast-in-place box girder demolition method of the present invention utilizes the uncut lower half of the web and box girder as a temporary load-bearing base for demolishing the upper half of the structure during the cutting process of the upper half, realizing the self-supporting of the box girder structure and significantly reducing the amount of temporary steel support structure. At the same time, the three-segment cutting method of the first vertical section 100, the longitudinal section 101 and the second vertical section 102 is adopted to avoid the instantaneous release of the body load and the sudden change of the force system and stress concentration, thereby improving construction efficiency and operational safety.

[0024] Specifically, in step one, the virtual plane a is determined and several steel support structures 2 are installed. The specific contents of step one are as follows: First, a comprehensive survey was conducted on the beam height, web thickness, structural dimensions, demolition boundary, and retained area of ​​the cast-in-place box girder 1 to be demolished. Through on-site survey and precise layout, vertical upper and lower layer cutting lines and longitudinal segment cutting lines were accurately marked on the surface of the box girder web, in conjunction with the construction drawings. Among them, the upper and lower layer cutting lines of the two sides of the web are located in the virtual plane a. The so-called longitudinal segment cutting line is the specific line direction of the wire saw cutting the box girder 1 segment by segment. The first vertical section 100, the longitudinal section 101, and the second vertical section 102 were obtained through the wire saw cutting.

[0025] The virtual plane a can be at a certain angle to or parallel to the top surface of the box girder 1. For example, when the top surface of the box girder 1 is parallel to the horizontal plane or has a large angle of inclination, the virtual plane a can be parallel to the top surface of the box girder 1 so that the weight on both sides of each segment can be balanced during the subsequent cutting process. Alternatively, when the top surface of the box girder 1 has a small angle of inclination to the horizontal plane, the virtual plane a can also be parallel to the horizontal plane.

[0026] The length of the longitudinal segment cutting line (i.e., the cutting depth of the longitudinal section 101) is calculated and determined based on the actual lifting capacity of the on-site hoisting equipment and lifting tools, and is usually 1.2m to 1.5m.

[0027] Then, based on the aforementioned on-site survey and precise layout, specific design drawings are obtained, the plan positions of several steel support structures 2 are measured, concrete bases 21 and steel pipe columns 20 installed on the concrete bases 21 are constructed to complete the installation of several steel support structures 2 and form a temporary support system.

[0028] Then, based on the equipment and safety arrangements at the construction site, a simple high-altitude operating platform was erected, and holes were made in the top plate of box girder 1 to serve as a construction operation passage; at the same time, the wire saw and its matching guide clamps and safety protection devices were fixedly installed; and the pre-construction safety inspection and hoisting equipment debugging were completed.

[0029] In addition, in step one, the wire saw's trajectory can be marked on the outer wall of the box girder 1, that is, the positions of the first vertical section 100, the longitudinal section 101 and the second vertical section 102 are predetermined, so that the wire saw can make accurate cuts according to the markings.

[0030] Reference Figure 2 In this embodiment, after the temporary support system is completed, several steel support structures 2 and several bridge piers 3 (including piers and / or abutments) at the lower end of the box girder 1 are arranged alternately along the longitudinal direction of the box girder 1. Therefore, along the longitudinal direction of the box girder 1, the box girder 1 can be divided into several support sections 11 and several suspended sections 10 arranged alternately. The so-called support section 11 means that the lower end of the support section 11 must be supported by a set of steel support structures 2 or bridge piers 3, and the so-called suspended section 10 means that the lower end of the suspended section 10 has no support structure.

[0031] Reference Figure 2 Therefore, in any two adjacent sets of segments along the longitudinal direction of box girder 1, one set is a support segment 11 and the other set is a suspended segment 10, which can greatly reduce the arrangement of temporary steel support system.

[0032] Among them, the preferred wire saw is a diamond bead wire saw.

[0033] The above methods are used to complete the preparatory work before cutting and dismantling box girder 1.

[0034] In step two, the wire saw cuts the cross-section of each group of segments in a three-segment manner, that is, first cut out... The first vertical section 100 is cut out, then the longitudinal section 101 is cut out, and finally the second vertical section 102 is cut out, thus completing the complete separation of one end of the segment from the main body of the box girder 1.

[0035] In step two, the so-called load-bearing stability means that, through monitoring over a period of time, it is determined that the main body of box girder 1 and the segments after the cutting operation can maintain their geometric shape, stress state, and spatial position unchanged, without instability, excessive deformation, settlement, or damage.

[0036] In steps two to three, the first segment to be cut and separated from several segments of box girder 1 is the suspended segment 10.

[0037] For example, the first segment to be cut and separated is the suspended segment 10 located in the middle of the box girder 1. Then, the box girder 1 can be cut off and lifted away segment by segment from the middle to both ends. In the subsequent cutting process, construction can be carried out simultaneously from the middle to both ends of the box girder 1, which greatly improves the efficiency of the box girder 1 demolition construction.

[0038] Reference Figure 3 Each time the suspended section 10 is cut and separated, the first vertical section 100 at both ends of the suspended section 10 protrudes from the second vertical section 102 at the same end. By adopting the above method, both ends of the suspended section 10 can be supported and held by the support section 11 when the suspended section 10 is cut and separated for the first time, which further improves the safety of the demolition construction.

[0039] In some embodiments, in steps two to three, the box girder 1 can be cut, separated and hoisted segment by segment from one longitudinal end to the other, which is not limited here.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for dismantling cast-in-place box girders, characterized in that, Includes the following steps: Step 1: Divide the box girder into upper and lower parts by a virtual plane passing through the web of the box girder, and arrange several steel support structures supporting the lower end of the box girder along the longitudinal direction of the box girder; Step 2: Use a wire saw to cut a first vertical section from the top of the box girder down to the virtual plane; after the box girder is under stable load, use the wire saw to continue cutting a longitudinal section along the box girder; after the box girder is under stable load, use the wire saw to continue cutting down to a second vertical section that penetrates the box girder. Step 3: Cut and separate the segments from the box girder using the cutting method described in Step 2, and then lift the segments away from the box girder; Step 4: Repeat steps 3 to 4 until the box girder is cut off and lifted off segment by segment along its longitudinal direction.

2. The method for dismantling cast-in-place box girders according to claim 1, characterized in that... : In step one, the box girder is divided into several supporting segments and several suspended segments arranged alternately along the longitudinal direction of the box girder, wherein each group of supporting segments is supported by a group of steel support structures or bridge piers. In steps two through four, in any two adjacent separations, the two sets of segments separated are... One group consists of the supporting sections and the other group consists of the suspended sections.

3. The method for dismantling cast-in-place box girders according to claim 2, characterized in that... : In steps two and three, the segment that is first cut and separated is the suspended segment.

4. The method for dismantling cast-in-place box girders according to claim 3, characterized in that... : In steps two and three, the segment that is first cut and separated is the suspended segment located in the middle of the box girder; In step four, the box girder is cut off section by section from the middle to both ends and lifted away.

5. The method for dismantling cast-in-place box girders according to claim 3 or 4, characterized in that... : Each time the suspended segment is cut and separated, the first vertical cross-section at both ends of the longitudinal direction protrudes beyond the second vertical cross-section at the same end.

6. The method for dismantling cast-in-place box girders according to claim 1, characterized in that... : Before step two, the wire saw's trajectory is marked on the box girder.

7. The method for dismantling cast-in-place box girders according to claim 1, characterized in that... : In step two, the cutting length of the longitudinal section is 1.2m to 1.5m.

8. The method for dismantling cast-in-place box girders according to claim 1, characterized in that... The virtual plane is parallel to the top surface of the box girder.

9. The method for dismantling cast-in-place box girders according to claim 2, characterized in that... : In step one, several of the steel support structures and several of the bridge piers are arranged alternately along the longitudinal direction of the box girder.

10. The method for dismantling cast-in-place box girders according to claim 9, characterized in that... : The steel support structure includes a concrete base cast into the ground and several steel pipe columns installed on the upper part of the concrete base.

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