Bracket small box girder and roof windowing type prefabricating method thereof

Abstract

The invention relates to the technical field of bridge construction, in particular to a bracket small box girder and a top plate windowing type prefabricating method thereof. A corbel small box girder comprises a bottom plate, a web plate, a top plate and a lifting wing, the position, close to the end of the girder, of the bottom plate is concaved upwards to form a corbel type cavity structure, and a support embedded part matched with a lower supporting structure is arranged at the bottom of a corbel. A solid structure is arranged above the position where the bracket is located, the thickness of the solid structure at the position of the bracket is larger than the thickness of the top plate and the thickness of the cantilever wing, an inner cavity of the small bracket box girder is divided into a large-diameter section and a small-diameter section, and the end of the small bracket box girder is of a closed reinforced concrete structure. The upper portion of the position where the bracket is located is arranged to be of a solid structure, the solid structure is thickened, so that the strength of the position is improved conveniently, and the bracket can bear large torque conveniently when matched with the bracket. The problem that in the prior art, the size arrangement of the box girder is limited due to the same section of the inner mold, and the installation difficulty of the box girder is increased is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and in particular to a bracket small box girder and a prefabrication method for its roof window opening type. Background Art

[0002] During the construction of bridges or rail transit, various components are required. A bridge is divided into an upper structure and a lower structure. The lower structure includes piers, abutments, and pile foundations and other structures that play a supporting role, and the upper structure includes box girders, bridge decks, and diaphragms and other structures. A box girder includes a roof, a bottom plate, webs, and cantilever wings. Among them, the roof, the bottom plate, and the webs enclose an inner cavity, and the cantilever wings can expand the width of the bridge deck to facilitate the construction of roads such as sidewalks. The box girder structure is widely used because of its good bending and shear resistance performance, the characteristic of uniform load transfer, and the ability to reduce its own weight and increase the span during the construction process.

[0003] In the prior art, during the construction of a box girder, an external mold and an internal mold are required to define the shape of the box girder. A steel reinforcement cage is tied between the internal mold and the external mold, and then concrete is poured into the inner cavity between the internal mold and the external mold. After forming, the mold is removed. For example, a Chinese invention patent application with an application publication date of March 26, 2021 and an application publication number of CN112554032A discloses an equal internal cross-section reinforced concrete box girder structure and a prefabrication method. The box girder structure has an inner cavity with an equal internal cross-section. When the mold needs to be removed during concrete forming, a winch steel wire rope is connected to the internal mold joint, and the internal mold is horizontally dragged out of the inner cavity of the box girder as a whole to complete the removal of the internal mold.

[0004] In order to facilitate removal, the internal mold needs to be made into a shape with the same cross-section, and the same cross-section of the inner cavity also limits the dimensions of the cantilever wings or other installation structures, thereby increasing the installation difficulty of the box girder. Summary of the Invention

[0005] In view of this, the present invention provides a bracket small box girder to solve the problem in the prior art that the same cross-section of the internal mold limits the dimension layout of the box girder, thereby increasing the installation difficulty of the box girder; the present invention also provides a prefabrication method for the roof window opening type of the bracket small box girder to solve the problem that the internal mold of the bracket small box girder has different cross-sections, so that the internal mold cannot be withdrawn from the end.

[0006] A bracket small box girder includes a bottom plate, webs, a roof, and cantilever wings. The bottom plate is recessed upward near the beam end to form a bracket-type concave cavity structure. A support embedment matching the lower support structure is provided at the bottom of the bracket. The position above the bracket is a solid structure, and the thickness of the solid structure at the bracket is greater than the thickness of the roof and the cantilever wings. The inner cavity of the bracket small box girder is divided into a large-diameter section and a small-diameter section, and the end of the bracket small box girder is a closed reinforced concrete structure.

[0007] Furthermore, ventilation holes are provided on the web plate.

[0008] Furthermore, the ventilation holes are arranged at intervals, and multiple ventilation holes are located at the same horizontal height. The distance between two adjacent ventilation holes is 3 meters to 6 meters.

[0009] The beneficial effects of the bracket small box girder in the present invention are as follows: The present invention forms the basic structure of the bracket small box girder through the bottom plate, web plate, top plate and cantilever. The bottom plate is recessed upward near the beam end to form a bracket-type concave cavity structure. A bearing embedment matching the lower support structure is provided at the bottom of the bracket, which is convenient for connecting with the lower support structure during construction to form a bridge; by setting the position above the bracket as a solid structure and thickening it, it is convenient to increase the strength here, and it is convenient to bear a large torque when cooperating with the bridge pier; due to the existence of the concave cavity structure, the inner cavity space is invaded inward, so that the inner cavity is divided into a large-diameter section and a small-diameter section. Furthermore, its functionality can be increased on the premise of keeping the large-diameter section unchanged; by closing the end of the bracket small box girder, its mechanical properties are further improved; thus, the problem that the same inner mold cross-section in the prior art limits the size arrangement of the box girder, resulting in an increase in the installation difficulty of the box girder is solved.

[0010] A prefabrication method for opening windows on the top plate of a bracket small box girder. First, splice the bottom mold and side mold of the box girder, and bind the bottom plate steel bars, side plate steel bars, top plate steel bars and cantilever steel bars into a formed shape. During the binding process of the top steel bars, reserve a skylight and a manhole at the top plate position. The size of the skylight is larger than that of the manhole. Furthermore, divide the top plate steel bars into an open section and a closed section; during the binding process of the top steel bars, install the corresponding inner mold in the closed section in place, and use open molds to fill the skylight and the manhole respectively; then carry out the first pouring. After setting, take out the inner molds corresponding to the open section and the closed section from the skylight of the box girder; then build a mold at the skylight for the second pouring to seal the skylight. After the structure at the skylight sets, take out the mold at the skylight from the manhole, and finally seal the manhole.

[0011] Furthermore, during the binding process of the top plate steel bars, reserve steel bar joints at the skylight and the manhole.

[0012] Furthermore, before pouring at the skylight, use a sleeve to connect the reserved steel bar joints and bind the steel bar cage at the skylight completely.

[0013] Furthermore, when removing the inner mold of the closed section, first use a winch to pull the inner mold of the closed section to the skylight, disassemble it into molds not larger than the size of the skylight, and then lift it out from the skylight.

[0014] Furthermore, the skylight is closed with a large wooden formwork and then formed by pouring concrete. The manhole is closed with a degradable board mold by pouring concrete.

[0015] Further, when splicing the bottom formwork and the side formwork of the box girder, place the bearing embedment at the corbel in place.

[0016] Further, the opening mold includes a skylight mold and a manhole mold. The skylight mold includes a baffle or a comb plate located inside the skylight, and the manhole mold is a steel box mold.

[0017] The beneficial effects of the prefabrication method for the corbel small box girder roof with openings in the present invention are as follows: In the present invention, first splice the bottom formwork and the side formwork, and bind the bottom plate steel bars, side plate steel bars, roof steel bars, and cantilever steel bars into a shape to facilitate the formation of the basic structure of the corbel small box girder; during the binding of the top steel bars, reserve skylights and manholes, and then divide the roof steel bars into an open end and a closed section; use the opening mold to block at the skylights and manholes, so that after the first pouring is completed, unclosed skylights and manholes can be formed on the roof; after the first pouring is completed, the main structure of the corbel small box girder has been completed. At this time, it is necessary to disassemble the mold. The outer mold is naturally easy to disassemble. For the inner mold, due to the setting of the skylights and manholes, the inner cavity is not completely closed, and the inner mold in the inner cavity can be taken out through the skylights; then, secondary pouring is required for the skylights. For the pouring of the skylights, a mold is naturally also required before pouring. After the secondary pouring, the mold required for the secondary pouring can be further taken out from the manhole through the manhole; finally, the manhole is poured and formed. Since the size of the skylight is larger than that of the manhole, it is convenient to take out a large number of inner molds during the first pouring through the skylight. For the skylights, the amount of mold required is naturally less than the amount of inner mold for the first pouring. Through the setting of the manhole, the mold remaining in the inner cavity of the corbel small box girder is reduced as much as possible, and the problem in the prior art that the inner mold cannot be withdrawn from the end due to different cross-sections of the inner mold of the corbel small box girder is solved by the method of batch construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a cross-sectional view schematic diagram of the corbel small box girder in the present invention;

[0020] Figure 2 It is a partial schematic diagram of the corbel small box girder in the present invention;

[0021] Figure 3 It is a partial schematic diagram of the corbel small box girder in the present invention (before removing the inner mold);

[0022] Figure 4 This is a schematic structural view of the internal formwork during the casting of the bracket small box girder in the present invention;

[0023] Figure 5 This is a schematic structural view of the comb plate used during the casting of the bracket small box girder in the present invention;

[0024] Figure 6 This is a side view of the comb plate used during the casting of the bracket small box girder in the present invention.

[0025] The meanings of the reference numerals in the figure are as follows: 1, cantilever wing; 2, bottom plate; 21, drain hole; 22, bearing embedment; 3, web; 31, ventilation hole; 4, top plate; 41, skylight; 42, manhole; 5, inner cavity; 6, internal formwork; 7, comb plate; 8, end plate. Detailed implementation manners

[0026] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be described below through specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0027] The terms used in this disclosure are only for the purpose of describing specific embodiments and are not intended to limit this disclosure. The singular forms "a", "the" and "said" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0028] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, these information should not be limited to these terms and cannot be understood as indicating or implying relative importance. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0029] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0030] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] In the subsequent description, the suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of explaining the present invention, and they have no specific meaning in themselves. Therefore, "module" and "component" can be used interchangeably.

[0032] For a better understanding of the technical solution of the present invention, the present invention will be described in detail below with reference to the drawings.

[0033] In the embodiment of the bracket small box girder in the present invention:

[0034] As Figures 1-6 shown, in this embodiment, the bracket small box girder includes a bottom plate 2, a web 3, a top plate 4, and a cantilever wing 1. The bottom plate 2, the web 3, and the top plate 4 enclose an inner cavity 5. In addition, an end plate 8 is provided at the end of the inner cavity 5, so that the inner cavity 5 becomes a closed space. The bottom plate 2, the web 3, the top plate 4, the cantilever wing 1, and the end plate 8 are all made of reinforced concrete structures. The thickness of the bottom plate 2 is not uniformly set, but is thick at both ends and thin in the middle. The thickness of the bottom plate 2 transitions from 300 mm at both ends to 180 mm in the middle. A drain hole 21 is also provided at the central position of the bottom plate 2. Once there is accumulated water in the inner cavity 5, it can flow to the central area and be discharged through the drain hole 21. The bottom plate 2 is recessed upward near the beam end to form a bracket-type concave cavity structure, which is convenient for mating installation with the lower support structure. Vent holes 31 are also provided on the web 3. The diameter of the vent holes 31 is 80 - 100 mm, and they are arranged at intervals of 3 - 6 meters and are at the same horizontal height. The concave cavity structure encroaches on the space of the inner cavity 5, dividing the inner cavity 5 into a large-diameter section and a small-diameter section. Due to the different cross-sectional diameters and the setting of the end plate 8, it is impossible to pull out the inner mold 6 as a whole from one side, so new inner mold disassembly means are required.

[0035] Specifically, the span of the bracket small box girder is between 25 and 35 meters. The concave cavity structure is located at its end. The upper part of the position where the bracket is located is a solid structure, and the thickness of the solid structure where the bracket is located is greater than the thicknesses of the top plate 4 and the cantilever 1, so that it can bear a large gravity. To facilitate docking with the pier, a bearing embedment 22 for installation is also provided at the bottom of the bracket. The bearing embedment is a connecting structure precast in the bracket, which is convenient for direct docking with the lower support structure. In this embodiment, the solid structure where the bearing embedment 22 is located is a square with a side length of 2 meters, and the bearing embedment 22 is installed therein, which is convenient for matching connection with other lower support structures such as piers.

[0036] In the embodiment of the prefabrication method of the bracket small box girder top plate with window opening in the present invention:

[0037] In this embodiment, the prefabrication method of the bracket small box girder top plate with window opening is introduced by taking the structure in the above-mentioned embodiment of the bracket small box girder as an example. During the prefabrication of the bracket small box girder, a mold and a steel reinforcement cage are required. The mold is divided into an outer mold and an inner mold 6. The outer mold includes a bottom mold, side molds, a bracket bottom mold and an end mold. Since the inner cavity 5 in the present invention is closed and the cross-sectional sizes are inconsistent, the inner mold 6 cannot adopt the method of pulling out from one end in the prior art. In the present invention, a skylight 41 and a manhole 42 are reserved on the top plate 4. After the casting is completed, first, the inner mold 6 is taken out from the skylight 41, and then the skylight 41 also needs to be closed. During the closing process of the skylight 41, the mold at the skylight 41 is taken out from the manhole 42, and finally the manhole 42 is blocked to complete the prefabrication of the overall box girder.

[0038] Specifically, first, the bottom mold and side molds of the box girder are spliced together, and the bottom plate steel bars, side plate steel bars, top plate steel bars and cantilever steel bars are bound into a shape. The bottom mold also includes a bracket bottom mold, and during the assembly of the molds, the bracket bottom mold and the side molds also need to be assembled. Of course, since the bearing embedment 22 needs to be prefabricated, during the assembly process, the bearing embedment 22 is pre-embedded at the corresponding position of the bracket bottom mold. Correspondingly, the end mold also needs to be installed in place during the assembly of the molds. During the process of binding the bottom plate steel bars, side plate steel bars, top plate steel bars and cantilever steel bars into a shape, it is generally carried out on a special steel bar binding rack. During the steel bar binding process, the prestressed ducts need to be reserved in the steel reinforcement cage in advance.

[0039] Since a skylight 41 needs to be opened on the top plate 4, during the pouring process, the top plate steel bars cannot be tied in place at one time, and the space for the skylight 41 needs to be reserved. In this embodiment, the skylight 41 is reserved at the large-diameter section of the inner cavity 5. Correspondingly, the inner mold 6 also needs to be adjusted to avoid the space on the inner mold 6. The inner mold 6 is divided into an open end corresponding to the skylight 41 and a closed section at other positions. During the tying of the top steel bars, attention needs to be paid to installing the inner mold 6 of the closed section in place at the same time. Of course, the inner mold 6 of the open end can be installed in place during the tying of the steel bars, or it can also be installed after the tying of the steel bars is completed. Of course, in other embodiments, the skylight can also be reserved at a position straddling the large-diameter section and the small-diameter section.

[0040] During the pouring of the top plate 4, a certain thickness needs to be maintained, so the skylight 41 and the manhole 42 need to be blocked to prevent concrete leakage. Specifically, an open mold is used to block the skylight 41 and the manhole 42. The open mold includes a skylight mold for blocking the skylight 41 and a manhole mold for blocking the manhole 42. The skylight mold includes a baffle or a comb plate 7 located in the skylight 41. The manhole mold is a steel box mold. The skylight 41 and the manhole 42 also need to be filled finally, so steel bar joints are reserved at the skylight 41 and the manhole 42. The steel bar joints pass through the open mold, and the steel bar joints are formed along with the tying of the top plate steel bars.

[0041] After the assembly of each part and the tying of the steel cage are completed, primary pouring is required. The concrete is poured into the already formed mold. After the concrete of the primary pouring has set, the overall structure of the box girder has been formed. At this time, only secondary pouring is required at the skylight 41 and the manhole 42. The outer mold of this box girder can be easily removed, and the key lies in the removal of the inner mold 6. First, the skylight mold and the manhole mold at the skylight 41 and the manhole 42 need to be taken out, and the inner mold 6 of the open end is removed and hoisted out from the skylight 41. Then, a winch is used to pull the inner mold 6 of the closed section to the skylight 41, and after being disassembled into molds not larger than the skylight size, it is hoisted out from the skylight 41.

[0042] After that, a sleeve is used to connect the reserved steel bar joints at the skylight 41, and the steel cage at the skylight 41 is tied completely. The construction personnel enter the inner cavity 5 of the box girder through the manhole 42, and a large wooden mold for supporting the bottom of the skylight 41 is erected at the bottom of the skylight 41. After the mold is erected, the skylight 41 is poured. After the pouring is completed and the skylight 41 has set, the wooden mold at the skylight 41 needs to be removed, and after the wooden mold is removed, it is taken out from the manhole 42.

[0043] Finally, it is necessary to carry out the pouring at the manhole 42. A degradable plate mold is built at the bottom of the manhole 42. After the steel bars at the manhole 42 are tied up, the pouring at the manhole 42 is carried out. At this time, since the inner cavity 5 has been closed, the degradable plate mold at the manhole 42 will remain in the inner cavity 5 and gradually degrade over time. It should be noted that the size of the manhole 42 is smaller than that of the skylight 41. In this embodiment, the size of the manhole 42 is 800*550 mm.

[0044] In the present invention, since the cross-section of the inner cavity 5 is uneven and the inner cavity 5 is closed, a new method needs to be designed for the removal of the inner mold 6. The large-area inner mold 6 needs to use steel molds. The steel molds are large in size and need to be reused without being damaged. A skylight 41 with a slightly larger reserved size is convenient for taking out the large number of large-sized steel molds from the skylight 41. Since the skylight 41 needs secondary pouring and the pouring area of the skylight 41 is small, wooden molds can be used, and the molds at the skylight 41 can be disassembled and taken out from the manhole 42. The area of the manhole 42 is further reduced relative to the size of the skylight 41, minimizing the components enclosed in the inner cavity 5 as much as possible.

[0045] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

Claims

1. A bracket small box girder, comprising a bottom plate, a web, a top plate and a cantilever wing, characterized in that: The bottom plate is recessed upward near the beam end to form a bracket - type cavity structure. A support embedment matching the lower support structure is arranged at the bottom of the bracket. The structure above the position where the bracket is located is solid, and the thickness of the solid structure at the bracket is greater than the thickness of the top plate and the cantilever. The inner cavity of the bracket small box girder is divided into a large - diameter section and a small - diameter section. The end of the bracket small box girder is a closed reinforced concrete structure.

2. The bracket small box girder according to claim 1, characterized in that: Vent holes are arranged on the web.

3. The bracket small box girder according to claim 2, wherein: The vent holes are arranged at intervals. A plurality of vent holes are at the same horizontal height, and the distance between adjacent two vent holes is from 3 meters to 6 meters.

4. A prefabrication method for the top plate of a bracket small box girder with a window opening. First, splice the bottom formwork and side formwork of the box girder, and bind the bottom plate steel bars, side plate steel bars, top plate steel bars and cantilever steel bars into a formed shape, characterized in that: During the process of binding the top reinforcement, a skylight and a manhole are reserved at the top - plate position. The size of the skylight is larger than that of the manhole, and thus the top - plate reinforcement is divided into an open section and a closed section. During the process of binding the top reinforcement, the corresponding inner formwork in the closed section is installed in place, and open - type molds are respectively filled at the skylight and the manhole. Then, primary pouring is carried out. After setting, the inner formwork corresponding to the open section and the closed section is taken out from the skylight of the box girder. Then, a mold is built at the skylight for secondary pouring to seal the skylight. After the structure at the skylight sets, the mold at the skylight is taken out from the manhole, and finally the manhole is sealed.

5. The prefabrication method of the corbel small box girder top plate with window openings according to claim 4, characterized in that: During the process of binding the top - plate reinforcement, reinforcement joints are reserved at the skylight and the manhole.

6. The prefabrication method for the top plate windowed corbel small box girder according to claim 5, characterized in that: Before pouring at the skylight, the reserved reinforcement joints are connected using sleeves, and the steel - cage at the skylight is bound completely.

7. The prefabrication method of the corbel small box girder top plate with window openings according to any one of claims 4-6, characterized in that: When removing the inner formwork of the closed section, first use a winch to pull the inner formwork of the closed section to the skylight, disassemble it into molds not larger than the size of the skylight, and then lift it out from the skylight.

8. The prefabrication method of the corbel small box girder top plate with window openings according to any one of claims 4-6, characterized in that: The skylight is closed with a large - scale wooden formwork and then formed by concrete pouring. The manhole is closed with a biodegradable - sheet mold and poured with concrete.

9. The prefabrication method of the corbel small box girder top plate with window openings according to any one of claims 4-6, characterized in that: When splicing the bottom formwork and the side formwork of the box girder, the support embedment at the bracket is placed in place.

10. The prefabrication method of the corbel small box girder top plate with window openings according to any one of claims 4-6, characterized in that: The open - type mold includes a skylight mold and a manhole mold. The skylight mold includes a baffle or a comb - tooth plate located inside the skylight. The manhole mold is a steel - box mold.

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