A prestressed self-locking precast concrete small box beam inner formwork construction method

Abstract

The present invention discloses a method for constructing a prestressed self-locking precast concrete small box girder inner formwork, the method comprising: placing a plurality of beam body segments coaxially, and connecting two adjacent beam body segments on the sides close to each other by means of a tapered pin and a tapered pin sleeve; inserting prestressed tendons into four installation channels respectively, and connecting a plurality of beam body segments arranged in sequence in series by means of the prestressed tendons; providing a fixing piece at one end of the prestressed tendons, and fixing the end of the prestressed tendons to one end of the spliced ​​beam body segments by means of the fixing piece; coaxially connecting a threaded steel connecting rod to the other end of the prestressed tendons by means of a wire rod connector, and installing a nut on the threaded steel connecting rod; pulling the prestressed tendons in a diagonal tensioning manner until the tapered pins and tapered pin sleeves of the two adjacent beam body segments are locked together, and then tightening the nut. The construction method of the present invention is simple and easy to operate, and can achieve rapid installation and disassembly of the concrete small box girder inner formwork by stretching the prestressed tendons.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction formwork, in particular to a construction method of a prestressed self-locking precast concrete small box beam inner formwork. Background Art

[0002] With the rapid development of municipal highway and bridge construction in China, prefabricated small box girders are widely used due to their high load-bearing capacity, high rigidity, and economical practicality. Prefabricated small box girders are hollow inside and require internal formwork. Height and space limitations within the small box girder create challenges in the design, fabrication, and installation of internal formwork. Traditional internal formwork typically involves designing and fabricating several small panels based on the structural details, then assembling them into a mold.

[0003] Currently, most concrete box girder inner formwork is spliced, made up of several small steel formwork pieces. This is typically hoisted, assembled, and secured using both manual labor and machinery. Each formwork is bolted together and features numerous internal supports. To remove the formwork, construction workers must enter the box girder, remove all bolts and support rods, and disassemble the inner formwork before removing it piece by piece. This process increases labor intensity and production costs, creating significant inconvenience for construction workers and can easily cause formwork deformation, impacting the concrete's appearance.

[0004] In the prior art, there is no method for constructing inner formwork of precast concrete small box beams that is suitable for prestressed self-locking type. Summary of the Invention

[0005] The invention provides a prestressed self-locking precast concrete small box girder inner formwork construction method, which can realize the rapid installation and disassembly of the precast concrete small box girder inner formwork.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for constructing a prestressed self-locking precast concrete small box girder inner formwork. The precast concrete small box girder inner formwork includes a plurality of beam segments, each of which is provided with four installation channels, the four installation channels being respectively arranged in the four corners of the beam segment. One end of the beam segment is provided with a plurality of tapered pins in a circumferential direction, and the other end is provided with a plurality of tapered pin sleeves. The method comprises: coaxially arranging the plurality of beam segments, and connecting adjacent sides of two adjacent beam segments by means of tapered pins and tapered pin sleeves; the installation channels at corresponding positions of adjacent beam segments are connected to each other;

[0008] Prestressed tendons are respectively inserted into the four installation channels, and the plurality of beam segments arranged in sequence are connected in series through the prestressed tendons;

[0009] A fixing piece is provided at one end of the prestressed tendon, and the end of the prestressed tendon is fixed to one end of the spliced ​​beam segment through the fixing piece;

[0010] A threaded steel connecting rod is coaxially connected to the other end of the prestressed tendon through a wire rod connector, and a nut is installed on the threaded steel connecting rod;

[0011] The prestressed tendons are pulled in a diagonally tensioning manner until the tapered pins and tapered pin sleeves of two adjacent beam segments are locked together, and the nuts are tightened to obtain an assembled inner mold.

[0012] In a possible implementation, in the process of connecting a plurality of beam segments arranged sequentially in series through the prestressed tendons, the prestressed tendons are arranged in a straight line, a curve, or a broken line.

[0013] In a possible implementation, during the process of pulling the prestressed tendons in a diagonal tensioning manner, the tensioning force of pulling the prestressed tendons is less than or equal to 0.75Fpk of the prestressed tendons.

[0014] In a possible implementation, the diagonally tensioning prestressed tendons are specifically:

[0015] It includes two 20-25 ton through-hole jacks, one of which is connected to the prestressed tendon at one end of the fixing member, and the other is connected to the threaded steel connecting rod;

[0016] The prestressed tendons are pulled in a diagonal tensioning manner by two jacks to provide prestress.

[0017] In a possible implementation, a lifting hole is provided on the top of each beam segment; after obtaining the assembled inner mold, the method further includes:

[0018] The assembled inner formwork is lifted and moved into a steel cage for precast concrete by connecting a hook of a crane to the lifting hole;

[0019] Disconnect the hook from the lifting hole, seal the lifting hole, and complete the inner mold insertion operation;

[0020] Concrete is poured into the steel cage to obtain a precast concrete small box beam.

[0021] In a possible implementation, the hoisting hole is a long box-shaped structure, and the hook is an anchor hook structure;

[0022] The hook of the crane is connected to the lifting hole, specifically: the hook is passed through the lifting hole, rotated 90 degrees, and then tightened.

[0023] In a possible implementation, during the process of lifting the assembled inner mold, the gap at the maximum opening of the annular seam between two adjacent beam segments is less than 2 mm.

[0024] In a possible implementation, each of the beam segments includes a left half mold and a right half mold; before coaxially placing the plurality of beam segments, the method further includes:

[0025] The left half mold and the right half mold are spliced ​​into a beam segment, and the beam segment is bundled with a plastic steel belt.

[0026] In a possible implementation, the left half mold and the right half mold each include an upper connecting block, a lower connecting block, a hinge shaft, and an opening and closing force transmission mechanism;

[0027] The axle seat is fixed on one side of the lower connecting block, and one end of the power shaft is rotatably connected to the axle seat, and the other end is rotatably connected to the power crank of the upper connecting block.

[0028] Before splicing the left half mold and the right half mold into a beam segment, the method further includes:

[0029] Pull the power crank to rotate the power crank and drive the longitudinal pull rod to move, drive the connecting rod to rotate until it is perpendicular to the longitudinal pull rod to support the left half mold or the right half mold, insert a safety pin on any one of the connecting rods to fix the position of the connecting rod.

[0030] In a possible implementation, after obtaining the precast concrete small box girder, the method further includes:

[0031] monitoring the strength of the precast concrete small box girder, after the strength is greater than or equal to a preset threshold;

[0032] Remove the fixing member, the prestressed tendons, the nuts, the threaded steel connecting rods and the wire rod connectors from the assembled inner mold;

[0033] Removing a safety pin of one of the beam segments in the outermost precast concrete small box beam, pulling the power crank, rotating the power crank to drive the longitudinal tie rod to move, and driving the connecting rod to rotate, so as to retract the left and right half molds, and pull the retracted left and right half molds out of the precast concrete small box beam;

[0034] Repeat the above steps until all the beam segments are pulled out.

[0035] The embodiment of the present invention provides a prestressed self-locking precast concrete small box girder inner formwork construction method. After multiple beam sections are coaxially placed, the installation channels corresponding to two adjacent beam sections are connected to each other, and prestressed tendons are respectively inserted into the four installation channels. The multiple beam sections arranged in sequence are connected in series through the prestressed tendons. Then, one end is fixed to one end of the spliced ​​beam sections through a fixing piece, and the other end is coaxially connected to the threaded steel connecting rod through a wire rod connector; then, the prestressed tendons at both ends are pulled by diagonal tensioning, so that the tapered pin shafts and tapered pin sleeves of the two adjacent beam sections are matched and locked, and then the nut sleeved on the threaded steel connecting rod is tightened, so that the concrete small box girder inner formwork can be quickly installed by stretching the prestressed tendons; the force applied to the prestressed tendons is released, the prestressed tendons are removed, and the precast concrete small box girder inner formwork can be disassembled from the outside in sequence. The construction method of the present invention is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the overall structure of a precast concrete small box girder inner mold for a method for constructing a prestressed self-locking precast concrete small box girder inner mold provided by an embodiment of the present invention, wherein (a) is a front view of the entire small box girder inner mold, (b) is a top view of the entire small box girder inner mold, and (c) is a partial cross-sectional view of the small box girder inner mold used to illustrate the prestressed installation components;

[0037] Figure 3 (a) is Figure 1 The cross-section along the AA direction, Figure 3 (b) is Figure 1 Schematic diagram of the connection structure of the CC position, Figure 3 (c) is Figure 1 Schematic diagram of the connection structure at the middle BB position;

[0038] Figure 2 A flowchart of the steps of the inner formwork construction method of a prestressed self-locking precast concrete small box beam provided by an embodiment of the present invention;

[0039] Figure 4A schematic structural diagram of a beam segment in a method for inner formwork construction of a prestressed self-locking precast concrete small box beam provided by an embodiment of the present invention, wherein (a) is a bottom view of the beam segment, (b) is a front view of the beam segment, (c) is a top view of the beam segment, (d) is a side view of the beam segment in direction A, and (e) is a side view of the beam segment in direction B;

[0040] Figure 5 A schematic diagram of the internal structure of a beam segment in a method for constructing an inner formwork for a prestressed, self-locking precast concrete small box beam provided by an embodiment of the present invention, wherein (a) is a schematic diagram of the internal structure of the beam segment when the tensioning and closing force transmission mechanism is supported, and (b) is a schematic diagram of the internal structure of the beam segment when the tensioning and closing force transmission mechanism is released;

[0041] Figure 6 A three-dimensional view of the left half of a beam segment in a method for constructing an inner formwork of a prestressed self-locking precast concrete small box beam provided by an embodiment of the present invention;

[0042] Figure 7 A three-dimensional diagram of the splicing of the left and right half molds of a beam segment in a method for constructing an inner mold of a prestressed self-locking precast concrete small box beam provided by an embodiment of the present invention;

[0043] Figure 8 A three-dimensional diagram of the upper connecting block of the left half mold of a prestressed self-locking precast concrete small box beam inner mold construction method provided by an embodiment of the present invention.

[0044] Reference numerals and descriptions:

[0045] 1. Support section; 2. Transition section; 3. Beam section; 4. Prestressed installation assembly; 4-1. Prestressed tendons; 4-2. Fixing parts; 4-3. Threaded steel connecting rod; 4-4. Nuts; 4-5. Wire rod connector; 4-6. Pad; 5. Upper connecting block of the left half mold; 6. Lower connecting block of the left half mold; 7. Upper connecting block of the right half mold; 8. Lower connecting block of the right half mold; 9. Hinge shaft; 10. Opening and closing force transmission mechanism; 10-1. Longitudinal pull rod; 10-2. Power crank; 10-3. Power shaft; 10-4. Shaft seat; 10-5. Connecting rod shaft; 10-6. Connecting rod; 10-7. Safety pin; 11. Ring lock pin buckle; 12. Tapered pin shaft; 13. Tapered pin sleeve; 14. Plastic steel belt; 15. Lifting hole; 16. Hook. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "multiple" means two or more. In addition, the use of "based on" or "according to" means openness and inclusiveness, because the process, steps, calculations or other actions "based on" or "according to" one or more of the conditions or values ​​may be based on additional conditions or values ​​beyond the stated in practice.

[0048] The existing precast concrete small box girder inner formwork construction is complicated. When assembling and disassembling the inner formwork, construction workers need to enter the narrow cavity of the inner formwork to tighten or remove the connecting bolts of the longitudinal seam and the circumferential seam, resulting in slow removal or installation of bolts, long construction time and low efficiency.

[0049] like Figure 1-Figure 3 As shown, the inner formwork of the precast concrete small box beam includes multiple beam segments. Each beam segment is provided with four mounting channels, one at each of the four corners of the beam segment. A plurality of tapered pins 12 are circumferentially disposed at one end of the beam segment, and a plurality of tapered pin bushings 13 are disposed at the other end.

[0050] The beam segments include support segments 1, transition segments 2, and beam segments 3. When multiple beam segments are spliced ​​together, the beam segment 3 needs to be set between two support segments 1, and the transition segment 2 needs to be set between the support segment 1 and the beam segment 3.

[0051] The support section 1 and the beam section 3 have uniform thickness along their lengths. The thickness of the transition section 2 along its lengths can be uniform or gradually change, and is used to form a transition between the support section 1 and the beam section 3. The thickness of the transition section 2 near one end of the support section 1 is the same as that of the support section 1, and the thickness of the transition section 2 near one end of the beam section 3 is the same as that of the beam section 3.

[0052] The present invention provides a prestressed self-locking precast concrete small box beam inner formwork construction method comprising:

[0053] S11. Place multiple beam segments coaxially, and connect the adjacent sides of two adjacent beam segments by using the tapered pin shaft 12 and the tapered pin sleeve 13; the installation channels at corresponding positions of adjacent beam segments are connected to each other.

[0054] Specifically, construction workers select the type and quantity of inner molds for splicing precast concrete small box beams according to needs, hoist the selected beam segments to the splicing area in sequence, and arrange multiple beam segments coaxially so that the installation channels at corresponding positions of two adjacent beam segments are connected to each other.

[0055] Figure 1 In (a), X indicates the state where two adjacent beam segments are not spliced ​​together, that is, the annular gap between the two adjacent beam segments is not closed.

[0056] S12. Insert prestressed tendons 4-1 into the four installation channels respectively, and connect the multiple beam segments arranged in sequence in series through the prestressed tendons 4-1.

[0057] The prestressed tendons 4 - 1 may be prestressed steel strands, or other prestressed tendon materials such as precision-rolled threaded steel bars.

[0058] S13. A fixing member 4-2 is provided at one end of the prestressed tendon 4-1, and the end of the prestressed tendon 4-1 is fixed to one end of the spliced ​​beam segments through the fixing member 4-2.

[0059] The fixing member 4 - 2 includes a fixing anchor seat and a clip, and the prestressed tendon 4 - 1 is detachably connected to the support segment 1 through the fixing anchor seat and the clip.

[0060] S14. Coaxially connect a threaded steel connecting rod 4-3 to the other end of the prestressed tendon 4-1 through a wire rod connector 4-5, and install a nut 4-4 on the threaded steel connecting rod 4-3.

[0061] Among them, the wire rod connector 4-5 is used to coaxially connect the prestressed tendon 4-1 and the threaded steel connecting rod 4-3, and the nut 4-4 is threadedly connected to the threaded steel connecting rod 4-3. Tightening the nut 4-4 can connect multiple beam segments connected in series into an integral inner mold.

[0062] S15. Pull the prestressed tendon 4-1 in a diagonal tensioning manner until the tapered pins and tapered pin sleeves of two adjacent beam segments are locked together, tighten the nuts, and obtain an assembled inner mold.

[0063] A pad 4-6 is provided between the end of the beam segment and the nut 4-4 to ensure the tightness of the connection between the nut 4-4 and the end of the beam segment.

[0064] The prestressed tendons 4 - 1 , the threaded steel connecting rods 4 - 3 , the wire rod connectors 4 - 5 , the fixings 4 - 2 , the pads 4 - 6 and the nuts 4 - 4 constitute the prestressed installation assembly 4 .

[0065] Among them, one end of the fixing part 4-2 is set as the passive tensioning end in the prestressed tensioning process, and one end of the threaded steel connecting rod 4-3 is set as the active tensioning end in the prestressed tensioning process. Since the other end of the prestressed tendon 4-1 is fixedly connected to one end of multiple beam segments connected in series, after prestressing is applied to one end of the threaded steel connecting rod 4-3, as the tensioning force increases, displacement begins to appear between the beam segments, and the initial spacing between the beam segments gradually decreases. Multiple beam segments are tightly connected under the action of the tapered pin shaft 12 and the tapered pin sleeve 13, that is, the annular seam between two adjacent beam segments is closed, and then the tensioning force is adjusted and the nut 4-4 is tightened to fix the tightly connected beam segments.

[0066] During the tensioning process, it is also necessary to take protective measures at both ends of the prestressed tendon 4-1 to prevent the prestressed tendon 4-1 from slipping or being strung.

[0067] Figure 1 In (a), Y represents the state after two adjacent beam segments are spliced ​​together, that is, the state after the annular gap between the two adjacent beam segments is closed.

[0068] The embodiment of the present invention provides a method for constructing the inner formwork of a precast concrete small box beam of prestressed self-locking type. After a plurality of beam segments are coaxially arranged, the installation channels corresponding to two adjacent beam segments are connected to each other, and prestressed tendons 4-1 are respectively inserted into the four installation channels. The plurality of beam segments arranged in sequence are connected in series through the prestressed tendons 4-1, and then one end is fixed to one end of the spliced ​​beam segments through a fixing piece 4-2, and the other end is coaxially connected to the threaded steel connecting rod 4-3 through a wire rod connector 4-5; and then Then, the prestressed tendons 4-1 at both ends are pulled by diagonal tensioning, so that the tapered pin shafts 12 and tapered pin sleeves 13 of the two adjacent beam segments are locked together, and then the nuts 4-4 sleeved on the threaded steel connecting rods 4-5 are tightened, and the inner mold of the small concrete box beam can be quickly installed by stretching the prestressed tendons 4-1; the force applied to the prestressed tendons 4-1 is released, and the prestressed tendons 4-1 are removed, and the inner mold of the precast concrete box beam can be disassembled from the outside in turn. The construction method of the present invention is simple and easy to operate.

[0069] Furthermore, in the process of connecting the plurality of beam segments arranged in sequence in series through the prestressed tendons 4 - 1 , the prestressed tendons 4 - 1 are arranged in a straight line, a curve or a broken line.

[0070] That is to say, the prestressing force in the inner cavity of a plurality of beam segments connected in series may be arranged in a straight line, a curved line or a broken line.

[0071] Furthermore, in the process of pulling the prestressed tendon 4 - 1 in a diagonal tensioning manner, the tensioning force of pulling the prestressed tendon 4 - 1 is less than or equal to 0.75Fpk of the prestressed tendon 4 - 1 .

[0072] Specifically, the magnitude of the tensioning force needs to be calculated based on factors such as the length, size, and weight of the inner mold obtained after assembly. In order to ensure that the prestressed tendon 4-1 does not break during the tensioning process, the tensioning force should be less than or equal to 0.75Fpk of the prestressed tendon 4-1.

[0073] Furthermore, the prestressed tendons 4-1 are pulled in a diagonal tensioning manner, specifically:

[0074] It includes two 20-25 ton through-hole jacks, one jack is connected to the prestressed tendon 4-1 at one end of the fixing piece, and the other jack is connected to the threaded steel connecting rod;

[0075] The prestressing tendons 4-1 are pulled diagonally by two jacks to provide prestress.

[0076] The prestressed tendons 4 - 1 may also be prestressed by other force-applying devices.

[0077] Furthermore, a lifting hole 15 is provided at the top of each beam segment. After obtaining the assembled inner mold, the method further includes:

[0078] The assembled inner formwork is lifted and moved into the steel cage for precast concrete by connecting the crane hook 16 with the lifting hole 15;

[0079] Disconnect the hook 16 from the lifting hole 15 and seal the lifting hole 15 to complete the inner mold insertion operation;

[0080] Concrete is poured into the steel cage to obtain a precast concrete small box beam.

[0081] Specifically, in order to facilitate construction workers to hoist the beam segments or the assembled inner mold, a hoisting hole 15 is opened on the top wall of each beam segment.

[0082] like Figure 1 and Figure 8 As shown, further, the lifting hole 15 is a long box-shaped structure, and the hook 16 is an anchor hook structure;

[0083] The hook 16 of the crane is connected to the lifting hole 15 , specifically: the hook 16 is passed through the lifting hole 15 , rotated 90 degrees, and then tightened.

[0084] When the construction workers need to separate the hook 16 from the hanging hole 15, they rotate the hook 16 90 degrees and then pull it out.

[0085] Furthermore, during the process of lifting the assembled inner formwork, the gap at the maximum opening of the annular seam between two adjacent beam segments is less than 2 mm.

[0086] Specifically, after the assembled inner mold is tensioned, the annular seams are completely closed. After the overall inner mold is lifted, there will be a certain gap between the two adjacent beam segments, but the size of the gap will not exceed 2mm. When the lifting point of the overall inner mold is relaxed and flat, the gaps will close by themselves.

[0087] like Figure 4 、 Figure 5 As shown, further, each beam segment includes a left half mold and a right half mold.

[0088] Among them, the top wall of the left half mold and the top wall of the right half mold are spliced ​​into the top wall of the beam segment; the bottom wall of the left half mold and the bottom wall of the right half mold are spliced ​​into the bottom wall of the beam segment; the side wall of the left half mold and the side wall of the right half mold are respectively the two side walls of the beam segment.

[0089] In order to facilitate the production, storage and transportation of beam segments, the beam segments are made into split templates and then assembled when used.

[0090] Furthermore, the joints of the top wall and the bottom wall of the beam segment are staggered at acute angles to the central axis of the beam segment. The joints of the top wall and the bottom wall of the beam segment are represented by M in the figure.

[0091] That is to say, the angles between the joints of the top wall of the beam segment and the joints of the bottom wall of the beam segment and the central axis of the beam segment are acute, that is, the top wall of the beam segment is wedge-shapedly divided by the joints of the top wall of the beam segment, and the bottom wall of the beam segment is wedge-shapedly divided by the joints of the bottom wall of the beam segment.

[0092] like Figure 1 As shown in (b), further, the joints of the top walls of two adjacent beam segments are staggered;

[0093] The joints of the bottom walls of two adjacent beam segments are staggered.

[0094] In actual application, staggering the positions of the top wall joints of multiple beam segments and the bottom wall joints of multiple beam segments can further increase the firmness of the inner membrane.

[0095] Before coaxially placing the plurality of beam segments, the method further includes:

[0096] The left half mold and the right half mold are spliced ​​into a beam segment, and the beam segment is bundled with a plastic steel belt 14.

[0097] Before splicing a plurality of beam segments, the left half-mold and the right half-mold need to be spliced ​​together into an integral beam segment by means of a plastic-steel belt 14 .

[0098] like Figure 5-Figure 7 As shown, further, the left half mold and the right half mold both include an upper connecting block, a lower connecting block, a hinge shaft 9 and an opening and closing force transmission mechanism 10.

[0099] The upper connecting block 5 of the left half mold includes the upper area of ​​the side wall of the left half mold and the top wall of the left half mold, and the upper connecting block 5 of the left half mold includes the lower area of ​​the side wall of the left half mold and the bottom wall of the left half mold. The upper connecting block 5 of the left half mold is connected to the lower connecting block 6 of the left half mold by a hinge shaft 9.

[0100] The opening and closing force transmission mechanism 10 is connected to the upper connecting block 5 of the left half mold and the lower connecting block 6 of the left half mold, and is used to control the support or release of the upper connecting block 5 of the left half mold and the lower connecting block 6 of the left half mold.

[0101] The right half mold includes an upper connecting block 7 of the right half mold, a lower connecting block 8 of the right half mold, a hinge shaft 9 and an opening and closing force transmission mechanism 10;

[0102] The upper connecting block 7 of the right half mold includes the upper area of ​​the side wall of the right half mold and the top wall of the right half mold. The upper connecting block 7 of the right half mold includes the lower area of ​​the side wall of the right half mold and the bottom wall of the right half mold. The upper connecting block 7 of the right half mold is connected to the lower connecting block 8 of the right half mold via a hinge shaft 9.

[0103] The opening and closing force transmission mechanism 10 is connected to the upper connecting block 7 of the right half mold and the lower connecting block 8 of the right half mold, and is used to control the support or release of the upper connecting block 7 of the right half mold and the lower connecting block 8 of the right half mold.

[0104] The opening and closing force transmission mechanism 10 includes a longitudinal pull rod 10-1, a power crank 10-2, a power shaft 10-3, a shaft seat 10-4, a connecting rod shaft 10-5, a connecting rod 10-6, and a safety pin 10-7.

[0105] The longitudinal tie rod 10 - 1 is arranged between the upper connecting block and the lower connecting block and is arranged along the long side direction of the upper connecting block.

[0106] There are multiple connecting rod shafts 10-5, and they are arranged at intervals on the side where the upper connecting block and the lower connecting block are close to each other.

[0107] The connecting rod 10-6 corresponds to the connecting rod shaft 10-5 one by one, and one end of the connecting rod 10-6 is rotatably connected to the connecting rod shaft 10-5, and the other end of the connecting rod 10-6 is rotatably connected to the longitudinal link 10-1.

[0108] In this embodiment, there are six connecting rods 10-6, three of which are used to connect the longitudinal rod 10-1 and the top wall of the right half mold or the left half mold, and the other three are used to connect the longitudinal rod 10-1 and the bottom wall of the right half mold or the left half mold.

[0109] A connecting plate is provided on one side of the lower connecting block close to the upper connecting block. An arc-shaped chute is provided on the connecting plate, and the arc center angle of the arc-shaped chute faces the lower connecting block.

[0110] The shaft seat 10-4 is fixed on one side of the lower connecting block close to the upper connecting block. One end of the power shaft 10-3 is rotationally connected to the shaft seat 10-4, and the other end is rotationally connected to the power crank 10-2. The other end of the power crank 10-2 is slidingly connected to the arc-shaped slide groove.

[0111] Before splicing the left and right half molds into a beam segment, the method further includes:

[0112] Pull the power crank 10-2 to rotate the power crank 10-2 and drive the longitudinal pull rod 10-1 to move, and drive the connecting rod 10-6 to rotate to be perpendicular to the longitudinal pull rod 10-1 to support the left half mold or the right half mold, and insert the safety pin 10-7 into any one of the connecting rods 10-6 to fix the position of the connecting rod 10-6.

[0113] Specifically, in order to facilitate the user to insert and remove the safety pin 10-7, the safety pin 10-7 is set on a connecting rod 10-6 close to the end of the beam segment.

[0114] Furthermore, after obtaining the precast concrete small box girder, the method further includes:

[0115] S21. Monitor the strength of the precast concrete small box girder until the strength is greater than or equal to a preset threshold;

[0116] S22. Remove the fixing piece 4-2, the prestressed tendon 4-1, the nut 4-4, the threaded steel connecting rod 4-3, and the wire rod connector 4-5 from the assembled inner mold;

[0117] S23. Remove the safety pin 10-7 of a beam segment located in the outermost precast concrete small box girder, pull the power crank 10-2, rotate the power crank 10-2, drive the longitudinal tie rod 10-1 to move, and drive the connecting rod 10-6 to rotate, so as to retract the left and right half molds, and pull the retracted left and right half molds out of the precast concrete small box girder;

[0118] Repeat the above steps until all beam segments are pulled out.

[0119] The left and right half molds of the prestressed self-locking precast concrete small box beam inner mold are connected by a tensioning and closing force transmission mechanism 10. It only needs to apply a force F to the power crank 10-2, and the power crank 10-2 can drive multiple connecting rods 10-6 to support it through the longitudinal pull rod 10-1, thereby realizing the assembly and fixation of the left half mold or the right half mold. Not only is the structure simple and easy to operate, but the longitudinal pull rod 10-1 mechanism can also reasonably distribute F as the displacement of the inner mold changes.

[0120] When assembling and disassembling the prestressed self-locking precast concrete small box beam inner mold of the present invention, construction workers do not need to enter the narrow mold cavity of the inner mold to work, thereby improving the connection quality of the inner mold, improving the working environment, reducing work safety risks, and improving construction efficiency.

[0121] The prestressed self-locking precast concrete small box girder inner mold of the present invention can meet the needs of industrialized production of precast concrete small box girder and has good economic benefits, scientific and technological benefits and social benefits.

[0122] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention shall be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for constructing an inner formwork of a precast concrete small box beam of prestressed self-locking type, characterized in that: The inner mold of a precast concrete small box beam includes a plurality of beam segments, each of which is provided with four installation channels, which are respectively arranged in the four corners of the beam segment. One end of the beam segment is provided with a plurality of tapered pins in a circumferential direction, and the other end is provided with a plurality of tapered pin sleeves. The method includes: The plurality of beam segments are coaxially arranged, and the sides of two adjacent beam segments close to each other are connected by means of a tapered pin shaft and a tapered pin sleeve; the installation channels at corresponding positions of adjacent beam segments are connected to each other; Prestressed tendons are respectively inserted into the four installation channels, and the plurality of beam segments arranged in sequence are connected in series through the prestressed tendons; A fixing piece is provided at one end of the prestressed tendon, and the end of the prestressed tendon is fixed to one end of the spliced ​​beam segment through the fixing piece; A threaded steel connecting rod is coaxially connected to the other end of the prestressed tendon through a wire rod connector, and a nut is installed on the threaded steel connecting rod; The prestressed tendons are pulled in a diagonally tensioning manner until the tapered pins and tapered pin sleeves of two adjacent beam segments are locked together, and the nuts are tightened to obtain an assembled inner mold.

2. The construction method according to claim 1, characterized in that: In the process of connecting a plurality of beam segments arranged in sequence in series through the prestressed tendons, the prestressed tendons are arranged in a straight line, a curve or a broken line.

3. The construction method according to claim 1, characterized in that: In the process of pulling the prestressed tendons in a diagonal tensioning manner, the tensioning force of pulling the prestressed tendons is less than or equal to 0.75Fpk of the prestressed tendons.

4. The construction method according to claim 1, characterized in that: The diagonal tensioning method for pulling the prestressed tendons is as follows: It includes two 20-25 ton through-hole jacks, one of which is connected to the prestressed tendon at one end of the fixing member, and the other is connected to the threaded steel connecting rod; The prestressed tendons are pulled in a diagonal tensioning manner by two jacks to provide prestress.

5. The construction method according to claim 1, characterized in that: A hoisting hole is provided on the top of each beam segment; after obtaining the assembled inner mold, the method further comprises: The assembled inner formwork is lifted and moved into a steel cage for precast concrete by connecting a hook of a crane to the lifting hole; Disconnect the hook from the lifting hole, seal the lifting hole, and complete the inner mold insertion operation; Concrete is poured into the steel cage to obtain a precast concrete small box beam.

6. The construction method according to claim 5, characterized in that: The hoisting hole is a long box-shaped structure, and the hook is an anchor hook structure; The hook of the crane is connected to the lifting hole, specifically: the hook is passed through the lifting hole, rotated 90 degrees, and then tightened.

7. The construction method according to claim 5, characterized in that: During the process of lifting the assembled inner mold, the gap at the maximum opening of the annular seam between two adjacent beam segments is less than 2 mm.

8. The construction method according to claim 1, characterized in that: Each of the beam segments includes a left half mold and a right half mold; before coaxially placing the plurality of beam segments, the method further includes: The left half mold and the right half mold are spliced ​​into a beam segment, and the beam segment is bundled with a plastic steel belt.

9. The construction method according to claim 8, characterized in that: The left half mold and the right half mold each include an upper connecting block, a lower connecting block, a hinge shaft, and an opening and closing force transmission mechanism; The axle seat is fixed on one side of the lower connecting block, and one end of the power shaft is rotatably connected to the axle seat, and the other end is rotatably connected to the power crank of the upper connecting block. Before splicing the left half mold and the right half mold into a beam segment, the method further includes: Pull the power crank to rotate the power crank and drive the longitudinal pull rod to move, drive the connecting rod to rotate until it is perpendicular to the longitudinal pull rod to support the left half mold or the right half mold, insert a safety pin on any one of the connecting rods to fix the position of the connecting rod.

10. The construction method according to claim 9, characterized in that: After obtaining the precast concrete small box girder, the method further comprises: monitoring the strength of the precast concrete small box girder, after the strength is greater than or equal to a preset threshold; Remove the fixing member, the prestressed tendons, the nuts, the threaded steel connecting rods and the wire rod connectors from the assembled inner mold; Removing a safety pin of one of the beam segments in the outermost precast concrete small box beam, pulling the power crank, rotating the power crank to drive the longitudinal tie rod to move, and driving the connecting rod to rotate, so as to retract the left and right half molds, and pull the retracted left and right half molds out of the precast concrete small box beam; Repeat the above steps until all the beam segments are pulled out.

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