A prefabricated box girder manufacturing method

Abstract

The present application relates to a kind of prefabricated box girder manufacturing method, including A, binding reinforcement;B, pouring;B, maintenance:Including B1, box girder top surface maintenance;B2 box girder side maintenance;B1 includes, B1-1, drawing;B1-2, film coating;B1-3, tensioning;B1-4, watering;B1-5, cover geotextile;B1-6, heat preservation;B1-7, remove covering layer;C, demoulding:box girder core mould is taken out from box girder;When the last box girder enters maintenance step, the next box girder is synchronized to carry out binding reinforcement step when box girder is continuously produced.The present application has the right end that no box girder curing can be maintained, plastic film tensioning degree is good, when multiple box girders are made, it can shorten overall manufacturing time, solve the problem that box girder maintenance needs to wait for box girder curing before being carried out, and the manufacturing cycle is long when multiple core moulds are made.

Description

Technical Field

[0001] This invention relates to the field of road and bridge construction technology, and in particular to a method for manufacturing precast box girders. Background Technology

[0002] During road construction, bridges are sometimes required. One method of bridge construction involves building piers and abutments, installing crossbeams on the piers, rapidly prefabricating box girders between the crossbeams, and then casting reinforced concrete bridge decks on the box girders. The box girder prefabrication process involves building a steel reinforcement cage inside the outer formwork of the box girder, placing the core mold of the box girder inside the steel reinforcement cage, pouring concrete, removing the side and end formwork of the outer formwork of the box girder after the concrete has solidified, curing it, and then removing the core mold. The existing precast box girder manufacturing process has the following shortcomings: all processes are completed at the same workstation, which means that the fabrication of multiple precast box girders can only be carried out sequentially, resulting in a long construction period; when welding the steel reinforcement cage, the welding machine is moved on the ground, and the power cord is easily damaged by dragging it on the ground; it is not possible to accurately and conveniently position the longitudinal steel bars of the steel reinforcement cage on the side of the corresponding box girder; the side formwork and end formwork can only be removed for geotextile curing after complete curing, and multiple curing processes are required to prevent moisture loss, which is not only time-consuming but also results in a long process time; it is laborious to extract the core mold of the box girder. Summary of the Invention

[0003] The first objective of this invention is to provide a precast box girder manufacturing method that allows for curing without the need for box girder curing, provides good plastic film tension, and shortens the overall manufacturing time when manufacturing multiple box girders. This solves the problems that box girder curing can only be carried out after the box girder has cured and that the manufacturing cycle is long when manufacturing multiple box girders.

[0004] The second objective of this invention is to provide a more labor-saving method for manufacturing precast box girders by removing the core mold, thus solving the problem of laborious removal of the core mold during box girder prefabrication.

[0005] The third objective of this invention is to provide a method for manufacturing precast box girders that enables convenient and accurate positioning of the longitudinal reinforcement bars in the side steel reinforcement cage, thus solving the problem that the longitudinal reinforcement bars on the side of the box girder cannot be conveniently positioned during the manufacturing process.

[0006] The fourth objective of this invention is to provide a method for manufacturing precast box girders with the welding wire suspended in the air during welding, which solves the problem that the welding wire is easily damaged when dragged during the precast welding of box girders.

[0007] The above technical problems are solved by the following technical solution: A method for manufacturing precast box girders, characterized by including: A) Reinforcing steel: fabricating the reinforcing steel skeleton of the box girder at the casting station; B) Casting: assembling the outer mold and core mold of the box girder at the casting station to form the box girder cavity, and injecting concrete into the box girder cavity. The outer mold of the box girder includes a bottom formwork plate, two side formwork plates detachably connected to the transverse ends of the bottom formwork, and two end formwork plates detachably connected to the longitudinal ends of the bottom formwork. After the concrete has initially set, the end formwork and side formwork are removed; B) Curing: carried out at the curing station, including B1) Curing the top surface of the box girder; B2) Curing the sides of the box girder: spraying water on the two exposed sides of the box girder; B1 includes: B1-1) Roughening: forming several longitudinally extending grooves on the surface of the box girder that has initially set but not yet cured, with the grooves parallel to each other; B1-2) Covering with film: covering the upper surface of the box girder with plastic film; B1-3) Tensioning... Tightening: Insert several cables into the trench through the plastic film, with the cables extending along the trench's direction. Tighten the plastic film during the insertion process. B1-4, Watering: Pour water onto the plastic film. B1-5, Covering with Geotextile: Cover the box girder with geotextile over the plastic film. B1-6, Insulation: Apply electricity to the cables to heat the water on the plastic film and maintain it at a set temperature. B1-7, Removing the Covering Layer: Collect the geotextile for reuse, allowing the water on the plastic film to evaporate. Apply electricity to the cables until the temperature generated exceeds the melting point of the plastic film, melting and burning it off. Water-retaining flanges are provided on both sides of the box girder's upper surface perpendicular to the trench's direction. The water from B1-4 submerges the portion of the box girder located between these flanges. C, Demolding: Remove the box girder core mold from the box girder. During continuous production of box girders, the next box girder undergoes the reinforcement binding process simultaneously when the previous box girder enters the curing stage.

[0008] Preferably, the curing station is equipped with a curing chamber and a box girder top surface curing device. A longitudinal track extending into the curing chamber is provided between the curing station and the pouring station. The pouring station is located at the rear end of the longitudinal track. The bottom formwork is supported on the longitudinal track by bottom formwork traveling wheels. The poured box girder is located on the bottom plate in a longitudinally extended state. The box girder top surface curing device includes a suspension base frame suspended above the track by a suspension frame. The suspension base frame is equipped with a crossbar, several rake teeth with their lower ends extending downward beyond the crossbar and connected to the crossbar, and a rake tooth lifting mechanism that drives the crossbar to lift and lower, causing the rake teeth to extend downward beyond the suspension base frame. The suspension base frame is also equipped with a covering mechanism, a watering mechanism, a line laying mechanism, and a geotextile covering mechanism located in front of the crossbar, and a mechanism that is connected by a swing arm. A rolling roller extending laterally in front of the suspension base is connected to the suspension base; an upper longitudinal shaft and a lower longitudinal shaft are rotatably connected to each of the two lateral side walls of the curing chamber, and a longitudinal water supply pipe is fixedly connected to them. The upper longitudinal shaft has an upper sealing plate extending longitudinally, and the lower longitudinal shaft has a lower sealing plate extending longitudinally. The longitudinal water supply pipe is located between the upper and lower longitudinal shafts and has spray nozzles distributed longitudinally for spraying water onto the side surface of the box girder located in the curing chamber; the box girder top surface curing device includes a suspension base suspended above the track by a suspension frame. The suspension base has a crossbar, several rake teeth extending laterally downwards beyond the crossbar and connected to the crossbar, and a drive crossbar. The lifting mechanism of the rake teeth causes them to extend downwards beyond the suspension base. The suspension base also includes a film covering mechanism, a watering mechanism, a geotextile laying mechanism, and a geotextile covering mechanism located in front of the crossbar, as well as a laterally extending compaction roller connected to the suspension base via a swing arm. During maintenance, the plastic film is supported on the film covering mechanism, the geotextile on the geotextile covering mechanism, and the same number of cable rolls as the rake teeth are supported on the geotextile laying mechanism. When the box girder passes under the suspension base, the rake tooth lifting mechanism drives the crossbar to descend until the rake teeth insert into the top surface of the box girder to a set depth, fixing one end of the plastic film supported on the film covering mechanism, one end of the geotextile supported on the geotextile covering mechanism, and one end of the cable rolls supported on the geotextile laying mechanism to one end of the box girder along its length. The cables are distributed laterally, positioned above the plastic film, and aligned one-to-one with the rake teeth. A roller presses onto the cables and is positioned below the geotextile. The rake teeth form grooves on the box girder. The plastic film is covered onto the box girder, and the cables are pressed into the grooves by the roller through the plastic film. Water is sprayed onto the plastic film by a watering mechanism, and the geotextile covers the plastic film and the cables, thus completing steps B1-1 to B1-5. After the box girder enters the curing chamber, the upper longitudinal shaft is rotated so that the upper sealing plate seals against the upper end of the side surface of the box girder. The lower longitudinal shaft is rotated so that the lower sealing plate seals against the side surface of the bottom template. Water is sprayed onto the side of the box girder through a spray nozzle, thus achieving step B2. Steps B1-6 and B1-7 are performed in the curing chamber. The cables are heating wires.After the bottom formwork is removed from the pouring station, the reinforcement cage work for the next box girder can be carried out, thus enabling some processes to be carried out in parallel during the continuous production of box girders, which can shorten the production time.

[0009] This technical solution allows for the completion of the following steps during curing: roughening, covering with a membrane, threading cables, water spraying, and covering with geotextile in one go, shortening the curing process and improving efficiency. It reduces surface unevenness or lack of membrane coverage in some areas caused by manual paving, thereby minimizing moisture loss from the box girder and reducing the risk of surface loosening and cracking due to strong winds. The cables can be easily pressed into the trench. Pressing the cables into the trench helps to tighten the plastic membrane, reducing moisture loss and saving water during curing. Covering with the membrane first allows the outer formwork to be removed and the geotextile covered after the concrete has initially set, saving time waiting for curing.

[0010] Preferably, the film covering mechanism includes a film roll rotatably connected to a suspension base and a film unloading motor that drives the film roll to rotate; the film roll is detachably connected to the suspension base. This provides a specific technical solution for the film covering mechanism.

[0011] Preferably, the suspension base has a first column and a second column arranged opposite to each other. The film roll is located between the first and second columns, and the film-dispensing motor is located outside the first column. The first column has a shaft mounting hole, and an outer flange is bolted to the outside of the shaft mounting hole. The housing of the film-dispensing motor is connected to the outer flange. The power output shaft of the film-dispensing motor passes through the shaft mounting hole and is fitted with a sleeve. The sleeve and the power output shaft of the film-dispensing motor rotate synchronously through a key and keyway. One end of the film roll is supported in an inner flange by a drive-side bearing. The inner flange is fixed to the first column by bolts. One end of the film roll and the sleeve rotate synchronously through a key and keyway. The other end of the film roll is supported in an opening slot of the second column by a connecting seat bearing. A clamping block for clamping the connecting seat bearing is detachably connected in the opening slot. This technical solution allows for convenient and quick replacement of the plastic film. The connection is reliable.

[0012] Preferably, the suspension base is provided with a first column and a second column arranged opposite to each other. The film covering mechanism includes a film roll rotatably connected at both ends to the first and second column. The geotextile covering mechanism includes a geotextile storage box and two traction rollers. The two ends of the two traction rollers are rotatably connected to the first and second column. A first guide roller is provided at the upper end of the geotextile storage box. A second guide roller is provided between the first guide roller and the traction roller. The height of the first guide roller is greater than the height of the second guide roller. The traction roller is located above the film roll and is connected to a traction motor. In use, the geotextile passes sequentially around the upper side of the first guide roller and the lower side of the second guide roller and then passes between the two traction rollers. Due to the large thickness of the geotextile, the winding method on the shaft results in a large roll volume and weight, placing high demands on the shaft and occupying a large amount of space. This preferred method uses a storage box, where the geotextile is folded and placed, ensuring convenient unwinding and easy loading. This technical solution can tighten the geotextile, which is beneficial for flattening and laying.

[0013] Preferably, the watering mechanism includes a horizontal water distribution pipe connected to the suspension base, a water storage tank, and a water pump that delivers water from the water storage tank to the horizontal water distribution pipe. The horizontal water distribution pipe is equipped with several forward-spraying nozzles. In use, water is sprayed by driving the water pump.

[0014] Preferably, the cable laying mechanism includes several cable reel support frames distributed laterally. Each support frame includes a connecting block connected to the suspension base at one end, a horizontal shaft head connected to the connecting block at the other end, a blocking pin passing through the other end of the horizontal shaft head, and a guide ring connected to the connecting block. In use, the cable reel, formed by winding the cable, is placed on the horizontal shaft head. The connecting block and the blocking pin block both ends of the cable reel. During use, the outer end of the cable wound from the reel passes through the guide ring and is connected to the box girder. This allows for independent cable laying in each trench.

[0015] Preferably, the suspension base has two horizontally distributed columns, each with a vertical groove on its inner side. The two ends of the crossbar are slidably connected to these vertical grooves. The upper sections of the two columns are connected together by a crossbeam. The rake tooth lifting mechanism includes a vertical guide rod whose lower end is connected to the crossbar, a vertical lead screw whose lower end is threaded to the crossbar and passes through it, and a lifting motor that drives the lead screw to rotate. The upper end of the vertical guide rod passes through the crossbeam, and the lifting motor is fixed to the crossbeam. This design is compact and prevents the rake teeth from interfering with other operations when roughening is not required.

[0016] Preferably, the cable is a heating wire. This allows for heating and insulation of the water between the plastic film and the geotextile, resulting in energy savings during heating.

[0017] Preferably, the melting point of the plastic film is higher than the set temperature but lower than 100°C. After curing, the plastic film is melted by heating, making it easy to remove.

[0018] Preferably, the curing chamber has an upper longitudinal shaft rotatably connected to each of its two transverse side walls, a lower longitudinal shaft rotatably connected to each of them, and a longitudinal water supply pipe fixedly connected to each of them. The upper longitudinal shaft is provided with an upper sealing plate extending longitudinally. Rotating the upper longitudinal shaft allows the upper sealing plate to seal against the upper end of the side surface of the box girder located in the curing chamber and to disengage from the side surface of the box girder located in the curing chamber. The lower longitudinal shaft is provided with a lower sealing plate extending longitudinally. Rotating the lower longitudinal shaft allows the lower sealing plate to seal against the side surface of the bottom formwork located in the curing chamber and to disengage from the side surface of the bottom formwork located in the curing chamber. The longitudinal water supply pipe is located between the upper and lower longitudinal shafts and is provided with spray heads distributed longitudinally for spraying water onto the side surface of the box girder located in the curing chamber. When in use, after the bottom formwork carries the box girder into the set position in the curing chamber, the upper and lower longitudinal rotating shafts rotate, causing the upper and lower sealing plates to seal the upper and lower sides of the box girder, thus sealing the sides of the box girder. Then, the longitudinal water supply pipe delivers water from the sprinkler head to spray onto the sides of the box girder for curing.

[0019] Preferably, the pouring station is equipped with two side formwork support frames located on both sides of the longitudinal track. The side formwork support frames are connected to the bottom formwork located at the pouring station via several detachable connection structures, and the side formwork fixing frame is equipped with support frame wheels. In use, the side formwork is fixed by the side panel support frame, which is convenient and reliable. When dismantling the formwork, the detachable connections are disassembled, the side formwork support frames are removed, and then the side formwork can be removed from the box girder.

[0020] Preferably, the detachable connection structure includes a connecting piece with bolt holes connected to the side template support frame, a transverse threaded head with one end connected to the bottom template, and a fixing nut for threaded connection to the threaded head; when the bottom template is located at the pouring position, the other end of the transverse threaded head passes through the bolt holes and is connected to the fixing nut to fix the side template support foot to the bottom template. The structure is compact and easy to disassemble.

[0021] Preferably, when the outer formwork of the box girder is assembled, the end template is fitted onto the core formwork of the box girder, the end template is sealed against the end face of the side template, and the end template is sealed against the upper surface of the bottom template. This facilitates fixing and positioning the end template.

[0022] Preferably, the box girder core mold is formed by a core mold base plate, a core mold top plate, a core mold left side plate, and a core mold right side plate. The core mold base plate includes a left section and a right section, the core mold top plate includes a left section and a right section, the core mold left side plate includes an upper left section and a lower left section, and the core mold right side plate includes an upper right section and a lower right section. The left and right sections of the base plate are connected together by several base plate hinges, and the right end face of the left section and the left end face of the right section abut together. The base plate hinges are located inside the box girder core mold, and the left and right sections of the top plate can be separated and joined together. The upper and lower sections of the left side plate are connected together by several left side plate hinges. The lower end face of the upper left side plate and the upper end face of the lower left side plate abut together. The left side plate hinges are located inside the box girder core mold. The upper and lower sections of the right side plate are connected together by several right side plate hinges. The lower end face of the upper right side plate and the upper end face of the lower right side plate abut together. The right side plate hinges are located inside the box girder core mold. The left section of the bottom plate is fixedly connected to the lower section of the left side plate. The upper section of the left side plate is fixedly connected to the left section of the top plate. The right section of the top plate is fixedly connected to the upper section of the right side plate. The lower section of the right side plate is fixedly connected to the right section of the bottom plate. Initially, the lower sections of the left and right sides of the box girder are connected by a lateral telescopic structure, which drives the lower sections of the left and right sides to rotate about the hinge of the bottom plate. The bottom plate and top plate of the core mold are connected by a vertical telescopic structure, which drives the right section of the top plate to rotate about the hinge of the right side of the right side of the right side of the right side of the right side of the left side of the top plate and the left section of the top plate to rotate about the hinge of the left side of the left side of the left side of the box girder. When the box girder core mold retracts inward, the movement trajectories of the right and left sections of the top plate, the upper and lower sections of the left and right sides of the left and right sides of the bottom plate are all located within the inner circumference of the box girder. Within the space; the specific process of step C is as follows: First, the vertical telescopic structure is contracted, driving the right section of the top plate and the upper section of the right side plate to rotate towards the box girder core mold around the right side plate hinge and detach from the inner surface of the box girder; then, the left section of the top plate and the upper section of the left side plate are driven to rotate towards the inside of the box girder around the left side plate hinge and detach from the inner surface of the box girder; then, while ensuring that the bottom plate of the box girder can rotate, the horizontal telescopic structure is contracted, causing the lower section of the left side plate and the left section of the bottom plate to rotate around the bottom plate hinge and detach from the inner surface of the box girder; the lower section of the right side plate and the right section of the bottom plate to rotate around the bottom plate hinge and detach from the inner surface of the box girder; finally, the box girder core mold is pulled out.

[0023] Preferably, the vertical telescopic structure includes a left vertical cylinder and a right vertical cylinder. The cylinder body of the right vertical cylinder is hinged to the inner surface of the right section of the bottom plate via a right longitudinal lower hinge shaft, and the piston rod of the right vertical cylinder is hinged to the inner surface of the right section of the top plate via a right longitudinal upper hinge shaft. The cylinder body of the left vertical cylinder is hinged to the inner surface of the left section of the bottom plate via a left longitudinal lower hinge shaft, and the piston rod of the left vertical cylinder is hinged to the inner surface of the left section of the top plate via a left longitudinal upper hinge shaft.

[0024] Preferably, the left end face of the right section of the roof slab and the right end face of the left section of the roof slab are fitted together. This allows for a more convenient and reliable sealing connection between the left and right ends of the roof slab, preventing grout leakage.

[0025] Preferably, the lateral telescopic structure includes a lateral cylinder, with its left end hinged to the inner surface of the lower section of the left side plate via a longitudinal left hinge shaft, and its right end hinged to the inner surface of the lower section of the right side plate via a longitudinal right hinge shaft. The structure is compact.

[0026] Preferably, a longitudinal groove is also included. Both the inner and outer surfaces of the longitudinal groove are arc surfaces. The centerline of the cylinder containing the inner surface of the longitudinal groove is the axis of the hinge of the base plate. The cylinder containing the inner surface of the longitudinal groove and the cylinder containing the outer surface of the longitudinal groove are coaxial. The left end of the longitudinal groove passes through the lower surface of the left section of the base plate, and the right end passes through the lower surface of the right section of the base plate. This technical solution ensures that the core mold base plate is directly positioned to allow it to rotate. That is, no lifting action is required; the lower left section of the left plate and the left section of the base plate can be driven to rotate around the hinge of the base plate to detach from the box girder, and the lower right section of the right plate and the right section of the base plate can be driven to rotate around the hinge of the base plate to detach from the box girder. This improves the convenience of demolding the box girder core mold.

[0027] Preferably, the left end face of the right section of the base plate and the right end face of the left section of the base plate are fitted together, with the left end face of the right section of the base plate pressing against the right end face of the left section of the base plate. At least one row of supporting balls is provided on the lower surface of the left section of the base plate, with the supporting balls in the same row distributed longitudinally and supported on the inner surface of the longitudinal groove. This design makes pulling out the box girder core mold easier. The longitudinal groove can be removed for reuse or retained on the box girder core mold. The method for removing the longitudinal groove is as follows: with both ends of the longitudinal groove extending beyond the box girder, after the box girder core mold is closed, lift both ends of the longitudinal groove to separate it from the adjacent core mold, then pull out the adjacent core mold, and then pull out the longitudinal groove. This method avoids breakage during the process of lifting the longitudinal groove to separate it from the box girder.

[0028] Preferably, when the outer formwork of the box girder is assembled, the end template is fitted onto the core formwork of the box girder, the end template is sealed against the end face of the side template, and the end template is sealed against the bottom template plate. The inner surface of the right section of the top plate is provided with a connecting ear for the right section of the top plate, the inner surface of the left section of the top plate is provided with a connecting ear for the left section of the top plate, the inner surface of the upper section of the left side plate is provided with a connecting ear for the upper section of the left side plate, the inner surface of the lower section of the left side plate is provided with a connecting ear for the lower section of the left side plate, the inner surface of the upper section of the right side plate is provided with a connecting ear for the upper section of the right side plate, and the inner surface of the lower section of the right side plate is provided with a connecting ear for the lower section of the right side plate. The end template is provided with a plurality of end template connecting ears, and a plurality of end template fixing bolts pass through the end template connecting ears one by one and are threaded onto the connecting ears for the right section of the top plate, the left section of the top plate, the upper section of the left side plate, the lower section of the left side plate, the upper section of the right side plate, and the lower section of the right side plate, so that the end template abuts against the end face of the side template. The fixed end formwork is convenient to use, and its structure can help fix the box girder core mold and prevent it from closing.

[0029] Preferably, the end template seal abuts against the upper surface of the end mold. This improves the manufacturing precision required for simultaneously sealing the end template with the side template and the bottom template.

[0030] Preferably, the reinforcing steel frame includes a top slab reinforcing steel mesh, a bottom slab reinforcing steel mesh, and two side slab reinforcing steel meshes connecting the two ends of the top slab reinforcing steel mesh to the two ends of the bottom slab reinforcing steel mesh. The side slab reinforcing steel mesh includes several rows of longitudinal reinforcing steel bars distributed in the vertical direction. The longitudinal reinforcing steel bars in the same row are distributed in the horizontal direction. The pouring station is also provided with a comb-shaped reinforcing steel positioning device located on both sides of the longitudinal rail. The comb-shaped reinforcing steel positioning device includes several reinforcing steel positioning support frames distributed in the vertical direction. The reinforcing steel positioning support frame includes a vertical pull rod and several horizontal support rods distributed in the vertical direction. One end of the horizontal support rod away from the longitudinal guide rail is connected to the vertical pull rod, and the other end is used to extend to the side of the side formwork support frame facing the longitudinal rail to support the longitudinal reinforcing steel bars. One horizontal support rod supports only one row of longitudinal reinforcing steel bars. One row of longitudinal reinforcing steel bars is supported on one horizontal support rod of all the reinforcing steel positioning support frames. At least one horizontal support rod is connected to the side formwork support frame through a sliding sleeve. In step A, the longitudinal reinforcing steel bars are supported by the horizontal support rods. After the reinforcing steel cage is fabricated, the horizontal support rods are removed, and the outer formwork of the box girder is assembled. The longitudinal reinforcement of the side reinforcing mesh is conveniently and reliably positioned. This achieves the third objective of the invention.

[0031] Preferably, the sliding sleeve is equipped with a linear bearing that supports the horizontal support rod. This makes positioning and supporting the telescopic reinforcing bar easier and smoother.

[0032] Preferably, the side formwork support frame is equipped with a positioning block; when the rebar positioning support frame moves towards the longitudinal track and the vertical pull rod abuts against the positioning block, the length of the horizontal support rod extending beyond the side formwork support frame away from the vertical pull rod is within a set range. This allows for easy detection of whether the rebar positioning support frame has extended to the correct position.

[0033] Preferably, there are two positioning blocks, which are aligned with the upper and lower ends of the vertical pull handle. This ensures good reliability during positioning.

[0034] Preferably, the positioning stop is made of rubber, which can reduce noise.

[0035] Preferably, the rebar positioning support frame further includes an anti-detachment rod, which is detachably inserted into the end of all the horizontal support rods on the same rebar positioning support frame away from the vertical handle rod. The anti-detachment rod is used to prevent the longitudinal rebar from falling laterally from the horizontal support rod, thus improving the reliability of positioning the longitudinal rebar. When the horizontal support rod is removed from the side formwork support frame, the anti-detachment rod is removed first. All horizontal support rods share a single anti-detachment rod, making it less likely to be lost when not in use.

[0036] Preferably, the upper end of the anti-detachment rod is provided with a handle. This makes it convenient to pull out the anti-detachment rod.

[0037] Preferably, the anti-detachment rod is provided with a suspension block, and the anti-detachment rod is suspended from the uppermost horizontal support rod by the suspension block.

[0038] Preferably, the horizontal support rod has a vertical through hole, and the anti-detachment rod passes through the vertical through hole. The upper end of the vertical through hole has a tapered section that is larger at the top and smaller at the bottom. This improves the ease of inserting the anti-detachment rod.

[0039] Preferably, the pouring station is also equipped with a welding torch power supply structure. This structure includes a longitudinal slide rail, a longitudinal suspension cable, a welding machine, a bracket slidably suspended on the longitudinal slide rail, and a welding machine input wire connected at one end to the welding machine. The welding machine is fixed to the bracket and has a positive output wire and a negative output wire. A conductive block is connected to the end of the negative output wire, and the positive output wire is connected to the welding torch. Suspension rings distributed along the extension direction of the welding machine input wire are fixed to the input wire and are fitted onto the longitudinal suspension cable. In use, the other end of the welding machine input wire is connected to a power source to supply power to the welding machine. The welding machine has a current adjustment knob and a dial surrounding the current adjustment knob. The current adjustment knob has a welding machine pointer. The scale value on the dial of the welding machine, aligned with the pointer of the welding machine part, is the output current value of the welding machine. The lower end of the bracket has a bracket knob and a dial surrounding the bracket knob. The bracket knob has a bracket pointer, and the scale value on the dial aligned with the pointer is the same as the scale value on the dial of the welding machine part. The bracket knob is connected to the current adjustment knob via a transmission mechanism. When the bracket knob rotates, it drives the current adjustment knob to rotate through the transmission mechanism. The angular velocity of the bracket knob during rotation is equal to the angular velocity of the current adjustment knob driven by the bracket knob. The welder can rotate to the bracket knob without using tools when performing welding operations at the pouring station. In step A, the welding torch power supply structure is used to weld the reinforcing steel frame. This avoids the underground dragging of power lines, achieving the fourth objective of the invention. During welding, the conductive block is placed on the conductive part of the object being welded that is connected to the welding area, and the welding torch performs the welding. The current of the welding machine, which is located at a high position, can be easily adjusted.

[0040] Preferably, the longitudinal slide rail has a polygonal cross-section. A single longitudinal slide rail is sufficient for sliding the hanger and prevents the hanger from rotating.

[0041] Preferably, the lower end of the bracket is provided with a storage frame, in which the welding torch and conductive block can be stored. This allows the welder to access the welding torch and conductive block without using tools while performing welding operations at the pouring station. When not welding, this prevents the welding torch and conductive block from drooping and interfering with other operations.

[0042] Preferably, a fork connected to the bracket is also included, which rests on the suspension ring closest to the welding machine. This prevents damage caused by excessive pulling on the connection between the welding machine input cable and the welding machine when the input cable is retracted or separated.

[0043] Preferably, the transmission mechanism includes a synchronous belt, a synchronous pulley for the welding machine section connected to the current adjustment knob, and a synchronous pulley for the hanger section connected to the hanger section knob. The synchronous pulley for the welding machine section and the synchronous pulley for the hanger section are connected together by the synchronous belt.

[0044] The beneficial effects of this invention are: when casting multiple box girders, some processes can be carried out in parallel, thereby saving production time; the concrete can be covered with geotextile for curing without curing, which can shorten the curing time; the plastic film has good tension; it can reduce the water used during curing; it saves energy during curing and heat preservation; removing the plastic film is convenient; it can complete the surface roughening and moisturizing curing of the box girder in one go, shortening the curing process and improving curing efficiency; the connection between the box girder and the cast-in-place bridge deck is reliable; it saves effort when pulling out adjacent core molds; it is convenient and accurate when positioning the reinforcing bars; and the input wire of the welding machine will not be dragged on the ground and damaged. Attached Figure Description

[0045] Figure 1 This is a side view schematic diagram of the box girder manufacturing device of the present invention;

[0046] Figure 2 This is a side view schematic diagram of the box girder top surface curing device;

[0047] Figure 3 This is a front view schematic diagram of the box girder top surface curing device;

[0048] Figure 4 for Figure 3 A magnified view of a portion of point B;

[0049] Figure 5 A schematic diagram of the relevant structures for roughening the top surface of a box girder using a curing device.

[0050] Figure 6 for Figure 5 A magnified view of a portion at point C;

[0051] Figure 7 This is a schematic diagram showing the connection between the film roll and the suspension base;

[0052] Figure 8 This is a schematic diagram illustrating the principle of geotextile unwinding in this invention;

[0053] Figure 9 This is a rear view diagram of the curing room;

[0054] Figure 10 for Figure 9 A magnified view of a portion at point D;

[0055] Figure 11 This is a magnified side view of the pouring station.

[0056] Figure 12 for Figure 11 A magnified view of a portion of point A;

[0057] Figure 13 for Figure 11 A magnified view of a portion of point E;

[0058] Figure 14 This is a rear view diagram of the box girder just after it has been poured at the pouring station.

[0059] Figure 15 for Figure 14 A magnified view of a portion of point F;

[0060] Figure 16 for Figure 14 A magnified view of a portion of point G;

[0061] Figure 17 Rear view of the power supply structure for the welding torch;

[0062] Figure 18 A rear view diagram of the steel reinforcement cage being tied at the pouring station;

[0063] Figure 19 This is a side view of the comb-shaped rebar positioning device and the side formwork support frame on one side of the longitudinal track.

[0064] Figure 20 for Figure 18 A magnified view of a portion of point H.

[0065] In the diagram: 1. Bottom formwork plate; 2. Side formwork; 3. End formwork; 4. Curing chamber; 5. Longitudinal track; 6. Bottom formwork traveling wheel; 7. Box girder top surface curing device; 8. Suspension frame; 9. Suspension base frame; 10. Crossbar; 11. Rake teeth; 12. Point; 13. Cutting edge; 14. Column; 15. Vertical chute; 16. Horizontal beam; 17. Vertical guide rod; 18. Vertical lead screw; 19. Lifting motor; 20. Swing arm; 21. Roller roller; 22. Film roll; 23. First column head; 24. Second column head; 25. Outer flange; 26. Sleeve; 27. Active side bearing; 28. Inner flange; 29. ​​Connecting seat bearing; 20. Pressing block; 30. Film roller; 31. Geotextile storage box; 32. Traction roller; 33. First guide roller; 44. Second guide roller. 33. Driven gear; 34. Driven gear; 35. Transverse water distribution pipe; 36. Water tank; 37. Water pump; 38. Water outlet; 39. Wire reel support frame; 40. Horizontal suspension rod; 41. Connecting block; 42. Horizontal shaft head; 43. Barrier pin; 44. Guide ring; 45. Wire reel; 46. Traction motor; 47. Film roll; 119. Upper longitudinal rotating shaft; 49. Lower longitudinal rotating shaft; 50. Longitudinal water supply pipe; 51. Upper sealing plate; 52. Lower sealing plate; 53. Spray head; 54. Side template support frame; 55. Support frame traveling wheel; 56. Connecting piece; 57. Transverse threaded head; 58. Fixing nut; 59. Left section of bottom plate; 60. Right section of bottom plate; 61. Left section of top plate; 62. Right section of top plate; 63. Upper section of left side plate; 64. Lower section of left side plate; 65. Right... Side plate upper section 66, right side plate lower section 67, bottom plate hinge 68, left side plate hinge 69, right side plate hinge 70, left vertical cylinder 71, right vertical cylinder 72, longitudinal slide groove 73, supporting ball 74, top plate right section connecting ear 75, top plate left section connecting ear 76, left side plate upper section connecting ear 77, left side plate lower section connecting ear 78, right side plate upper section connecting ear 79, right side plate lower section connecting ear 80, end template connecting ear 81, end template fixing bolt 82, longitudinal reinforcement 83, reinforcement positioning support bracket 84, vertical pull rod 85, horizontal support rod 86, sliding sleeve 87, positioning stop block 88, anti-detachment rod 89, handle 90, suspension block 91, vertical through hole 92. 93. Conical section, 94. Longitudinal slide rail, 95. Longitudinal suspension cable, 96. Welding machine, 97. Hanger, 98. Welding machine input wire, 99. Positive output wire, 100. Negative output wire, 101. Conductive block, 102. Welding gun, 118. Storage frame, 103. Suspension ring, 104. Shift fork, 105. Current adjustment knob, 106. Welding machine dial, 107. Welding machine pointer, 108. Hanger knob, 109. Hanger dial, 110. Hanger pointer, 111. Synchronous belt, 112. Trench, 113. Plastic film, 114. Cable, 115. Water, 116. Geotextile, 117. Water-blocking flange, 119. Film roll, 120. Box girder, 122. Box girder core mold, 123. Welding gun power supply structure. Detailed Implementation

[0066] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0067] See Figures 1 to 20A method for manufacturing precast box girders is disclosed, which is implemented using a box girder manufacturing device. The box girder manufacturing device includes an outer box girder mold and a core box girder mold 122. The outer box girder mold includes a bottom template 1, two side templates 2 detachably connected to the transverse ends of the bottom template, and two end templates 3 detachably connected to the longitudinal ends of the bottom template. The bottom template, the two side templates, and the two end templates form a box girder cavity. The core box girder mold is used to form the inner cavity of the box girder. The method also includes a curing chamber 121, a longitudinal track 4 extending from the front end into the curing chamber, and a casting station located at the rear end of the longitudinal track. The bottom template is supported on the longitudinal track by bottom template wheels 5. The cast box girder is positioned longitudinally on the bottom plate. A box girder top surface curing device 6 is provided between the curing chamber and the casting station. The box girder top surface curing device includes a suspension base frame 8 suspended above the track by a suspension frame 7. The suspension base is equipped with a crossbar 9, several rake teeth 10 connected to the crossbar and distributed laterally, with their lower ends extending downwards beyond the crossbar, and a rake tooth lifting mechanism that drives the crossbar to rise and fall, causing the rake teeth to extend downwards beyond the suspension base. The lower end of the rake teeth is provided with a pointed tip 11, and the front side is provided with a vertically extending cutting edge 48. The suspension base is equipped with two horizontally distributed columns 12, and the inner side of the columns is provided with a vertical sliding groove 13. The two ends of the crossbar are slidably connected in the sliding groove. The upper sections of the two columns are connected together by a crossbeam 14. The rake tooth lifting mechanism includes a vertical guide rod 15 whose lower end is connected to the crossbeam, a vertical lead screw 16 whose lower end is threaded to the crossbeam and passes through the crossbeam, and a lifting motor 17 that drives the lead screw to rotate. The upper end of the vertical guide rod passes through the crossbeam, the upper end of the vertical lead screw is rotatably connected to the crossbeam, and the lifting motor is fixed to the crossbeam. The suspension base also includes a film covering mechanism, a watering mechanism, a line laying mechanism, a geotextile covering mechanism located behind the crossbar, and a compaction roller 19 located in front of the suspension base and connected to it via a swing arm 18. The compaction roller extends laterally. The film covering mechanism includes a film roll 20 rotatably connected to the suspension base and a film unloading motor 21 that drives the film roll to rotate. The film roll and the suspension base are detachably configured. Specifically, the suspension base is provided with a first column 22 and a second column 23 arranged opposite to each other. The film roll is mounted between the first column and the second column. The film feeding motor is located outside the first column. The first column has a shaft mounting hole. An outer flange 24 is bolted to the outside of the shaft mounting hole. The housing of the film feeding motor is connected to the outer flange. The power output shaft of the film feeding motor passes through the shaft mounting hole and is fitted with a sleeve 25. The sleeve and the power output shaft of the film feeding motor rotate synchronously through a key and keyway. One end of the film roll is supported by an inner flange 27 through an active side bearing 26. The inner flange is also fixed to the first column by bolts. One end of the film roll and the sleeve also rotate synchronously through a key and keyway. The other end of the film roll is supported in the opening slot of the second column through a connecting seat bearing 28. A clamping block 29 for clamping the connecting seat bearing is detachably connected in the opening slot.Before assembling the film roll, the inner flange is integrally assembled with one end of the film roll, and the other end of the film roll is assembled with the connecting bearing. During film roll assembly, one end of the film roll is inserted into the sleeve, then the inner flange is bolted to the first mounting beam. Simultaneously, the connecting bearing on the other end of the film roll is inserted into the opening slot, and the bolted removable clamping block is attached to the second mounting beam to press the connecting bearing. When the film roll needs to be removed for replacement, first remove the removable clamping block and the inner flange, then axially move the film roll to separate it from the sleeve, and then remove the film roll. Before installation, a film roll 50 is wound on the film roll shaft. The geotextile covering mechanism includes a geotextile storage box 30 and two traction rollers 31. During use, the geotextile is pulled by the two traction rollers. Two traction rollers are rotatably connected to the first and second column heads. A first guide roller 32 is located at the top of the geotextile storage box, and a second guide roller 33 is located between the first guide roller and the traction rollers. The height of the first guide roller is greater than the height of the second guide roller. The geotextile passes sequentially around the upper side of the first guide roller and the lower side of the second guide roller before passing between the two traction rollers. The traction rollers are located above the film roll. One end of one traction roller is connected to the traction motor 47, and the other end is equipped with a drive gear 34. The drive gear meshes with a driven gear 35 connected to the other traction roller. The geotextile storage box has a rectangular structure, with the geotextile folded and aligned inside. The watering mechanism includes a transverse water distribution pipe 36 connected to the suspension base, a water storage tank 37, and a water pump 38 that transports water from the water storage tank to the transverse water distribution pipe. The transverse water distribution pipe is equipped with several forward-spraying nozzles 39. The cable laying mechanism includes several cable reel support frames 40, which are distributed laterally. Each cable reel support frame includes a connecting block 42 connected at one end to a horizontal suspension rod 41 on a suspension base, a horizontal shaft head 43 connected at one end to the connecting block, a blocking pin 44 passing through the other end of the horizontal shaft head, and a guide ring 45 connected to the connecting block. In use, a cable reel 46 with a cable wound on it is fitted onto the horizontal shaft head. The connecting block and the blocking pin block both ends of the cable reel, and the end of the cable on the cable reel passes through the guide ring.

[0068] When using the box girder top surface curing device, the film roll 119 is installed on the film roll shaft, the water tank is filled with water, the geotextile is placed in the geotextile storage box, and the geotextile passes around the upper side of the first guide roller, the lower side of the second guide roller and between the two traction rollers in sequence. The cable roll with the same number of rake teeth is carried on the cable laying mechanism.

[0069] As the box girder passes beneath the suspended base frame, the rake tooth lifting mechanism drives the crossbar to descend until the rake teeth insert into the top surface of the box girder to a set depth. This fixes one end of the plastic film supported by the covering mechanism, one end of the geotextile supported by the geotextile covering mechanism, and one end of the cable roll supported by the cable laying mechanism at the front end along the length of the box girder. The cable is positioned above the plastic film, and the cable is aligned one-to-one with the rake teeth. The rolling roller presses on the cable and is positioned below the geotextile. The rake teeth form grooves on the box girder, and the plastic film is covered onto the box girder. The cable, through the plastic film, is pressed into the groove by the rolling roller. Water is sprayed onto the plastic film by the watering mechanism, and the geotextile covers the plastic film and the cable. The cable is an electric heating wire. During curing in the curing chamber, the cable is energized to heat the water on the plastic film to maintain a set temperature. After curing, the geotextile is removed, and the cable is energized to heat up to a set temperature until the plastic film melts.

[0070] The curing chamber has an upper longitudinal shaft 49 rotatably connected to each of its two transverse side walls, a lower longitudinal shaft 50 rotatably connected to each of them, and a longitudinal water supply pipe 51 fixedly connected to each. The upper longitudinal shaft has an upper sealing plate 52 extending longitudinally. Rotating the upper longitudinal shaft allows the upper sealing plate to seal against the upper end of the side surface of the box girder located inside the curing chamber and disengage from the side surface of the box girder located inside the curing chamber. The lower longitudinal shaft has a lower sealing plate 53 extending longitudinally. Rotating the lower longitudinal shaft allows the lower sealing plate to seal against the side surface of the bottom formwork located inside the curing chamber and disengage from the side surface of the bottom formwork located inside the curing chamber. In use, when the box girder reaches its receiving position inside the curing chamber, the upper and lower sealing plates abut against adjacent side surfaces. The longitudinal water supply pipe is located between the upper and lower longitudinal shafts and has spray heads 54 distributed longitudinally for spraying water onto the side surface of the box girder located inside the curing chamber.

[0071] The pouring station is equipped with two side formwork support frames 55 located on both sides of the longitudinal track. These side formwork support frames are connected to the bottom formwork located at the pouring station via several detachable connection structures. The side formwork fixing frame is equipped with support frame wheels 56. The detachable connection structures include connecting pieces 57 with bolt holes connected to the side formwork support frames, a transverse threaded head 58 connected at one end to the bottom formwork, and a fixing nut 59 for threaded connection to the threaded head. When the bottom formwork is located at the pouring station, the other end of the transverse threaded head passes through the bolt hole and is connected to the fixing nut, thus fixing the side formwork support feet to the bottom formwork. When the box girder outer formwork is assembled, the end formwork is fitted onto the box girder core formwork, the end formwork seals against the end face of the side formwork, and the end formwork seals against the upper surface of the bottom formwork. The side formwork is inclined, and a support step is provided on the inner side of the lower end of the side formwork. The corner of the upper surface of the bottom formwork in the width direction (i.e., transverse) supports the side formwork on the support step, providing support and limiting. The side formwork is fixed to the bottom formwork by being supported by the side formwork support frames. The box girder core mold is a tubular structure formed by a core mold base plate, a core mold top plate, a core mold left side plate, and a core mold right side plate. The core mold base plate includes a left section 60 and a right section 61; the core mold top plate includes a left section 62 and a right section 63; the core mold left side plate includes an upper left section 64 and a lower left section 65; and the core mold right side plate includes an upper right section 66 and a lower right section 67. The left and right sections of the base plate are connected by several base plate hinges 68. The left end face of the right section and the right end face of the left section of the base plate abut against each other, with the left end face of the right section pressing against the right end face of the left section of the base plate. The base plate hinges are located inside the box girder core mold. The left and right sections of the top plate can be joined together separately. The right end face of the left section and the left end face of the right section are inclined, with the right end face of the left section above the left end face of the right section. The upper and lower sections of the left side plate are connected by several left side plate hinges 69. The lower end face of the upper section of the left side plate and the upper end face of the lower section of the left side plate abut together. The left side plate hinges are located inside the box girder core mold. The upper and lower sections of the right side plate are connected by several right side plate hinges 70. The lower end face of the upper section of the right side plate and the upper end face of the lower section of the right side plate abut together. The right side plate hinges are located inside the box girder core mold. The left section of the bottom plate is fixedly connected to the lower section of the left side plate. The upper section of the left side plate is fixedly connected to the left section of the top plate. The right section of the top plate and the upper section of the right side plate are fixedly connected. The lower section of the right side plate is fixedly connected to the right section of the bottom plate. The lower sections of the left and right sides are connected by a lateral telescopic structure, which drives the lower sections of the left and right sides to rotate around the base plate hinge.The bottom plate and top plate are connected by a vertical telescopic structure. This structure drives the right section of the top plate to rotate around the right side plate hinge and the left section of the top plate to rotate around the left side plate hinge. When the box girder core mold retracts inward, the movement trajectories of the right and left sections of the top plate, the upper and lower sections of the left and right sides of the left and right sides of the bottom plate, as well as the left and right sections of the bottom plate, are all within the space enclosed by the inner circumference of the box girder. The vertical telescopic structure includes a left vertical cylinder 71 and a right vertical cylinder 72. The cylinder body of the right vertical cylinder is hinged to the inner surface of the right section of the bottom plate via a right longitudinal downward hinge shaft, and the piston rod of the right vertical cylinder is hinged to the inner surface of the right section of the top plate via a right longitudinal upward hinge shaft. Similarly, the cylinder body of the left vertical cylinder is hinged to the inner surface of the left section of the bottom plate via a left longitudinal downward hinge shaft, and the piston rod of the left vertical cylinder is hinged to the inner surface of the left section of the top plate via a left longitudinal upward hinge shaft. When closing the box girder core mold, the right vertical cylinder contracts first, followed by the left vertical cylinder. The lateral telescopic structure is a lateral cylinder, with its left end hinged to the inner surface of the lower section of the left side plate via a longitudinal left hinge shaft, and its right end hinged to the inner surface of the lower section of the right side plate via a longitudinal right hinge shaft. The box girder core mold also includes a longitudinal slide groove 73, the inner and outer surfaces of which are both arc surfaces. The centerline of the cylinder containing the inner surface of the longitudinal slide groove is the axis of the hinge of the bottom plate. The cylinder containing the inner surface of the longitudinal slide groove and the cylinder containing the outer surface of the longitudinal slide groove are coaxial. The left end of the longitudinal slide groove passes through the lower surface of the left section of the bottom plate, and the right end passes through the lower surface of the right section of the bottom plate. At least one row of support balls is provided on the lower surface of the left section of the bottom plate. The support balls 74 in the same row are distributed longitudinally and supported on the inner surface of the longitudinal slide groove. The inner surface of the right section of the top plate is provided with a connecting ear 75 for the right section of the top plate, the inner surface of the left section of the top plate is provided with a connecting ear 76 for the left section of the top plate, the inner surface of the upper section of the left side plate is provided with a connecting ear 77 for the upper section of the left side plate, the inner surface of the lower section of the left side plate is provided with a connecting ear 78 for the lower section of the left side plate, the inner surface of the upper section of the right side plate is provided with a connecting ear 79 for the upper section of the right side plate, and the inner surface of the lower section of the right side plate is provided with a connecting ear 80 for the lower section of the right side plate. The end template is provided with a number of end template connecting ears 81. A number of end template fixing bolts 82 pass through the end template connecting ears one by one and are threaded onto the connecting ears of the right section of the top plate, the connecting ears of the left section of the top plate, the connecting ears of the upper section of the left side plate, the connecting ears of the lower section of the left side plate, the connecting ears of the upper section of the right side plate, and the connecting ears of the lower section of the right side plate, so that the end faces of the end template and the side template abut together.

[0072] The method for removing the box girder core mold after the end template is removed is as follows: The right vertical cylinder retracts, driving the right end of the top plate to rotate inwards about the right side plate hinge, thus detaching the right section of the top plate and the upper section of the right side plate from the box girder; the left vertical cylinder retracts, driving the left end of the top plate to rotate inwards about the left side plate hinge, thus detaching the left section of the top plate and the upper section of the left side plate from the box girder; the transverse cylinder retracts, driving the lower sections of the left and right sides plate to rotate inwards about the bottom plate hinge. This process causes the lower sections of the left side plate, the left section of the bottom plate, the lower section of the right side plate, and the right section of the bottom plate to detach from the box girder; the transverse cylinder extends and resets, lifting the longitudinal slide rail to detach it from the box girder (this method avoids deformation and breakage of the longitudinal slide rail during lifting, preventing it from detaching and being reused, as the longitudinal slide rail is still pressed down by the box girder core mold at three points along the transverse direction); the transverse cylinder retracts to a set length; the box girder core mold is pulled longitudinally to remove the adjacent core mold from the box girder; and the longitudinal slide rail is removed.

[0073] The box girder includes a steel reinforcement cage and concrete poured onto the steel reinforcement cage. The steel reinforcement cage includes a top slab steel reinforcement mesh, a bottom slab steel reinforcement mesh, and two side slab steel reinforcement meshes connecting the two ends of the top slab steel reinforcement mesh to the two ends of the bottom slab steel reinforcement mesh. The side slab steel reinforcement mesh includes several rows of longitudinal steel bars distributed vertically. The longitudinal steel bars 83 in the same row are distributed horizontally. The pouring station is also equipped with comb-shaped steel bar positioning devices located on both sides of the longitudinal rail horizontally and two side formwork support frames located on both sides of the longitudinal rail horizontally. The comb-shaped steel bar positioning devices include... The system includes several longitudinally distributed rebar positioning and support frames 84. Each rebar positioning and support frame includes a vertical pull rod 85 and several horizontal support rods 86 distributed vertically. One end of each horizontal support rod, away from the longitudinal guide rail, is connected to the vertical pull rod; the other end extends to the side of the side formwork support frame facing the longitudinal rail to support the longitudinal rebar. Each horizontal support rod supports only one row of longitudinal rebars, and each row of longitudinal rebars is supported by one horizontal support rod of all the rebar positioning and support frames. The upper left and lower left horizontal support rods are connected to the side formwork support frame via sliding sleeves 87. Linear bearings supporting the horizontal support rods are installed inside the sliding sleeves. The side formwork support frame is equipped with positioning blocks 88. When the rebar positioning and support frame moves towards the longitudinal rail and the vertical pull rod abuts against the positioning block, the length of the horizontal support rod extending beyond the side formwork support frame from the end away from the vertical pull rod is within a set range. There are two positioning blocks, aligned with the upper and lower ends of the vertical pull rod. The positioning blocks are made of rubber. The rebar positioning and supporting frame also includes an anti-detachment rod 89, which is detachably inserted into the end of all the horizontal supporting rods on the same rebar positioning and supporting frame away from the vertical handle rod. The anti-detachment rod is used to prevent the longitudinal rebar from falling laterally from the horizontal supporting rod. The upper end of the anti-detachment rod is provided with a handle 90. The anti-detachment rod is provided with a suspension block 91, and the anti-detachment rod is suspended from the uppermost horizontal supporting rod by the suspension block. The horizontal supporting rod is provided with a vertical through hole 92, and the anti-detachment rod passes through the vertical through hole. The upper end of the vertical through hole is provided with a tapered section 93 that is larger at the top and smaller at the bottom.

[0074] The pouring station is also equipped with a welding torch power supply structure 123, which includes a longitudinal slide rail 94, a longitudinal suspension cable 95, a welding machine 96, a bracket 97 that can slide and be suspended on the longitudinal slide rail, and a welding machine input wire 98 connected to the welding machine at one end. The welding machine is fixed on the bracket. The longitudinal slide rail has a polygonal cross-section. The welding machine has a positive output line 99 and a negative output line 100. The end of the negative output line is connected to a conductive block 101, and the positive output line is connected to the welding torch 102. The lower end of the bracket is equipped with a storage frame 118, in which the welding torch and the conductive block are stored. When the welder performs welding operations at the pouring station, he can retrieve the welding torch and the conductive block without using tools. A suspension ring 103, distributed along the extension direction of the welding machine input wire, is fixed to the welding machine input wire. The suspension ring is sleeved on the longitudinal suspension cable and is a circular ring. During use, the other end of the welding machine's input wire is connected to a power source to supply power to the welding machine. It also includes a fork 104 connected to the mounting bracket, which rests on the suspension ring closest to the welding machine. The welding machine has a current adjustment knob 105 and a welding machine scale 106 surrounding the current adjustment knob. The current adjustment knob has a welding machine pointer 107, and the scale value on the welding machine scale aligned with the welding machine pointer is the output current value of the welding machine. The lower end of the mounting bracket has a mounting bracket knob 108 and a mounting bracket scale 109 surrounding the mounting bracket knob. The mounting bracket knob has a mounting bracket pointer 110, and the scale value on the mounting bracket scale aligned with the mounting bracket pointer is the same as the scale value on the welding machine scale aligned with the welding machine pointer. The mounting bracket knob is connected to the current adjustment knob via a transmission mechanism. When the mounting bracket knob rotates, it drives the current adjustment knob to rotate through the transmission mechanism. The angular velocity of the mounting bracket knob during rotation is equal to the angular velocity of the current adjustment knob driven by the mounting bracket knob. The transmission mechanism includes a synchronous belt 111, a welding machine synchronous pulley connected to the current adjustment knob, and a mounting bracket synchronous pulley connected to the mounting bracket knob. The welding machine synchronous pulley and the mounting bracket synchronous pulley are connected together by the synchronous belt. When the welder performs welding operations at the pouring station, he can rotate the mounting bracket knob without using any tools.

[0075] The process of fabricating precast box girders using this invention is as follows: First, construct a steel reinforcement frame at the pouring station: Position the longitudinal steel bars using a comb-type steel bar positioning device, tie the longitudinal and transverse steel bars forming the steel reinforcement frame together, and weld them together using a welding torch-powered structure; Second, pour concrete: Push out the longitudinal support rods, assemble the outer formwork and core formwork of the box girder, and pour concrete; Third, remove the outer formwork: After the concrete has initially set, remove the end formwork and side formwork; Fourth, cure: Move the bottom formwork supporting the box girder to the curing room for curing; Fifth, remove the core formwork: Remove the core formwork from the box girder, remove the box girder 120 from the bottom formwork, and move the bottom formwork and core formwork back to the pouring station; Repeat the above steps to fabricate the next precast box girder. After the second step of one precast box girder is completed, the first step of the next precast box girder is carried out simultaneously.

[0076] The box girder maintenance process includes top surface maintenance; side surface maintenance; top surface maintenance includes: roughening: forming several longitudinally extending grooves 112 on the partially set but not yet cured box girder surface, with the grooves parallel to each other; covering with film: covering the top surface of the box girder with plastic film 113; tensioning: inserting several cables 114 through the plastic film into the grooves, with the cables extending along the direction of the grooves, and tensioning the plastic film during the insertion of the cables into the grooves; watering: water 115 being poured onto the plastic film; covering with geotextile: covering the box girder with geotextile 116 on the plastic film. Water-retaining flanges 117 are provided on both sides of the upper surface of the box girder perpendicular to the extension direction of the trench. The water submerges the part of the box girder located between the water-retaining flanges. Insulation: The cable is energized to heat the water on the plastic film and keep it constant at the set temperature. Removal of the covering layer: The geotextile is collected again for reuse, the water on the plastic film is evaporated, and the cable is energized until the temperature generated by the cable is higher than the melting point of the plastic film, thereby melting and burning the plastic film.

Claims

1. A method for manufacturing precast box girders, characterized in that, The process includes: A) Reinforcing steel reinforcement: fabricating the reinforcing steel skeleton of the box girder at the pouring station; B) Pouring: assembling the outer and core molds of the box girder at the pouring station to form the box girder cavity, and pouring concrete into the cavity. The outer mold includes a bottom formwork, two side formworks detachably connected to the transverse ends of the bottom formwork, and two end formworks detachably connected to the longitudinal ends of the bottom formwork. After the concrete has initially set, the end and side formworks are removed; B) Curing: carried out at the curing station, including B1, top surface curing of the box girder; B2, side surface curing of the box girder: spraying water on the two exposed sides of the box girder; B1 includes: B1-1, Roughening: forming several longitudinally extending grooves on the surface of the box girder that has initially set but not yet cured, with the grooves parallel to each other; B1-2, Covering with film: covering the upper surface of the box girder with plastic film; B1-3, Tensioning: inserting several cables through the plastic film into the grooves. Extending along the trench direction, the plastic film is stretched as the cable is inserted into the trench; B1-4, Watering: Water is poured onto the plastic film; B1-5, Covering with geotextile: Geotextile is placed over the plastic film to cover the box girder; B1-6, Insulation: The cable is energized to heat the water on the plastic film and maintain it at a set temperature; B1-7, Removing the covering layer: The geotextile is collected again for reuse, the water on the plastic film evaporates, and the cable is energized until the temperature generated by the cable is higher than the melting point of the plastic film, thus melting and burning the plastic film; Water-retaining flanges are provided on both sides of the upper surface of the box girder perpendicular to the trench direction, and the water in B1-4 submerges the part of the box girder located between the water-retaining flanges; C, Demolding: The core mold of the box girder is removed from the box girder; When the box girder is produced continuously, the next box girder is simultaneously subjected to the steel reinforcement step when the previous box girder enters the curing step.

2. The method for manufacturing a precast box girder according to claim 1, characterized in that, The curing station is equipped with a curing chamber and a box girder top surface curing device. A longitudinal track extending into the curing chamber is provided between the curing station and the pouring station. The pouring station is located at the rear end of the longitudinal track. The bottom formwork is supported on the longitudinal track by bottom formwork traveling wheels. The poured box girder is located on the bottom plate in a longitudinally extended state. The box girder top surface curing device includes a suspension base frame suspended above the track by a suspension frame. The suspension base frame is equipped with a crossbar, several rake teeth with their lower ends extending downward beyond the crossbar and connected to the crossbar, and a rake tooth lifting mechanism that drives the crossbar to lift and lower, causing the rake teeth to extend downward beyond the suspension base frame. The suspension base frame is also equipped with a covering mechanism, a watering mechanism, a line laying mechanism, and a geotextile covering mechanism located in front of the crossbar, and is connected to the suspension base frame by a swing arm. A rolling roller extending laterally in front of the suspension base is connected to the curing chamber; an upper longitudinal shaft and a lower longitudinal shaft are rotatably connected to each of the two lateral side walls of the curing chamber, and a longitudinal water supply pipe is fixedly connected to each other. The upper longitudinal shaft has an upper sealing plate extending longitudinally, and the lower longitudinal shaft has a lower sealing plate extending longitudinally. The longitudinal water supply pipe is located between the upper and lower longitudinal shafts and has spray nozzles distributed longitudinally for spraying water onto the side surface of the box girder located in the curing chamber; the box girder top surface curing device includes a suspension base suspended above the track by a suspension frame. The suspension base has a crossbar, several rake teeth extending laterally downwards beyond the crossbar and connected to the crossbar, and a drive mechanism for raising the crossbar. The lowering mechanism causes the rake teeth to extend downwards beyond the suspension base. The suspension base also includes a film covering mechanism, a watering mechanism, a geotextile laying mechanism, and a geotextile covering mechanism located in front of the crossbar, as well as a laterally extending compaction roller connected to the suspension base via a swing arm. During curing, the plastic film is supported on the film covering mechanism, the geotextile on the geotextile covering mechanism, and the same number of cable rolls as the rake teeth are supported on the geotextile laying mechanism. When the box girder passes under the suspension base, the rake tooth lifting mechanism drives the crossbar to descend until the rake teeth insert into the top surface of the box girder to a set depth. This fixes one end of the plastic film supported on the film covering mechanism, one end of the geotextile supported on the geotextile covering mechanism, and one end of the cable rolls supported on the geotextile laying mechanism to one end of the box girder along its length. Along the transverse distribution, the cable is located above the plastic film, and the cable is aligned one-to-one with the rake teeth. The rolling roller presses on the cable and is located below the geotextile. The rake teeth form grooves on the box girder. The plastic film is covered on the box girder. The cable is pressed into the groove by the rolling roller through the plastic film. Water is sprayed onto the plastic film by the watering mechanism. The geotextile covers the plastic film and covers the cable, thus completing steps B1-1 to B1-5. After the box girder enters the curing chamber, the upper longitudinal shaft is rotated so that the upper sealing plate seals against the upper end of the side surface of the box girder. The lower longitudinal shaft is rotated so that the lower sealing plate seals against the side surface of the bottom template. Water is sprayed onto the side of the box girder through the spray head, thus achieving B2. B1-6 and B1-7 are carried out in the curing chamber. The cable is an electric heating wire.

3. A method for manufacturing precast box girders according to claim 1 or 2, characterized in that, The pouring station is equipped with two side formwork support frames located on both sides of the longitudinal track. The side formwork support frames are connected to the bottom formwork located at the pouring station through several detachable connection structures. The side formwork fixing frame is equipped with support frame traveling wheels. The detachable connection structure includes a connecting piece with bolt holes connected to the side formwork support frame, a transverse threaded head with one end connected to the bottom formwork, and a fixing nut for threaded connection to the threaded head. When the bottom formwork is located at the pouring station, the other end of the transverse threaded head passes through the bolt holes and is connected to the fixing nut to fix the side formwork support feet to the bottom formwork.

4. The method for manufacturing precast box girders according to claim 1 or 2, characterized in that, The box girder core mold is formed by a core mold base plate, a core mold top plate, a core mold left side plate, and a core mold right side plate. The core mold base plate includes a left section and a right section; the core mold top plate includes a left section and a right section; the core mold left side plate includes an upper left section and a lower left section; and the core mold right side plate includes an upper right section and a lower right section. The left and right sections of the base plate are connected by several base plate hinges, and the right end face of the left section and the left end face of the right section abut against each other. The base plate hinges are located inside the box girder core mold. The left and right sections of the top plate can be separated and joined together. The left side plate... The upper section and the lower section of the left side plate are connected together by several left side plate hinges. The lower end face of the upper section of the left side plate abuts against the upper end face of the lower section of the left side plate. The left side plate hinges are located inside the box girder core mold. The upper section and the lower section of the right side plate are connected together by several right side plate hinges. The lower end face of the upper section of the right side plate abuts against the upper end face of the lower section of the right side plate. The right side plate hinges are located inside the box girder core mold. The left section of the bottom plate is fixedly connected to the lower section of the left side plate. The upper section of the left side plate is fixedly connected to the left section of the top plate. The right section of the top plate is fixedly connected to the upper section of the right side plate. The lower section of the right side plate is fixedly connected to the right section of the bottom plate. The lower sections of the left and right sides of the mandrel are connected by a lateral telescopic structure, which drives both sections to rotate about the hinge of the bottom plate. The bottom and top plates of the mandrel are connected by a vertical telescopic structure, which drives the right section of the top plate to rotate about the hinge of the right side of the right side of the right side of the right side of the right side of the left side of the top plate and the left section of the top plate to rotate about the hinge of the left side of the left side of the top plate. When the mandrel of the box girder retracts inward, the movement trajectories of the right and left sections of the top plate, the upper and lower sections of the left and right sides of the left and right sides of the bottom plate are all within the area enclosed by the inner circumference of the box girder. Within the space; the specific process of step C is as follows: First, the vertical telescopic structure is contracted, driving the right section of the top plate and the upper section of the right side plate to rotate towards the box girder core mold around the right side plate hinge, thus separating from the inner surface of the box girder; then, the left section of the top plate and the upper section of the left side plate are driven to rotate towards the inside of the box girder around the left side plate hinge, thus separating from the inner surface of the box girder; next, while ensuring that the bottom plate of the box girder can rotate, the horizontal telescopic structure is contracted, causing the lower section of the left side plate and the left section of the bottom plate to rotate around the bottom plate hinge, thus separating from the inner surface of the box girder; the lower section of the right side plate and the right section of the bottom plate to rotate around the bottom plate hinge, thus separating from the inner surface of the box girder; finally, the box girder core mold is pulled out.

5. A method for manufacturing precast box girders according to claim 4, characterized in that, It also includes a longitudinal groove, the inner and outer surfaces of which are both arc surfaces. The center line of the cylinder containing the inner surface of the longitudinal groove is the axis of the hinge of the base plate. The cylinder containing the inner surface of the longitudinal groove and the cylinder containing the outer surface of the longitudinal groove are coaxial. The left end of the longitudinal groove passes through the lower surface of the left section of the base plate and the right end passes through the lower surface of the right section of the base plate. The left end face of the right section of the base plate and the right end face of the left section of the base plate are engaged and abutted together. The left end face of the right section of the base plate presses on the right end face of the left section of the base plate. At least one row of support balls is provided on the lower surface of the left section of the base plate. The support balls in the same row of support balls are distributed longitudinally. The support balls are supported on the inner surface of the longitudinal groove.

6. A method for manufacturing precast box girders according to claim 4, characterized in that, When the outer formwork of the box girder is assembled, the end template is fitted onto the core formwork of the box girder. The end template is sealed against the end face of the side template and the bottom template. The inner surface of the right section of the top plate is provided with a connecting ear for the right section of the top plate, the inner surface of the left section of the top plate is provided with a connecting ear for the left section of the top plate, the inner surface of the upper section of the left side plate is provided with a connecting ear for the upper section of the left side plate, the inner surface of the lower section of the left side plate is provided with a connecting ear for the lower section of the left side plate, the inner surface of the upper section of the right side plate is provided with a connecting ear for the upper section of the right side plate, and the inner surface of the lower section of the right side plate is provided with a connecting ear for the lower section of the right side plate. The end template is provided with several connecting ears for the end template. Several end template fixing bolts pass through the connecting ears for the end template and are threaded onto the connecting ears for the right section of the top plate, the left section of the top plate, the upper section of the left side plate, the lower section of the left side plate, the upper section of the right side plate, and the lower section of the right side plate, so that the end template abuts against the end face of the side template.

7. A method for manufacturing precast box girders according to claim 1 or 2, characterized in that, The reinforcing steel frame includes a top slab reinforcing steel mesh, a bottom slab reinforcing steel mesh, and two side slab reinforcing steel meshes connecting the two ends of the top slab reinforcing steel mesh to the two ends of the bottom slab reinforcing steel mesh. The side slab reinforcing steel mesh includes several rows of longitudinal reinforcing steel bars distributed in the vertical direction. The longitudinal reinforcing steel bars in the same row are distributed in the horizontal direction. The pouring station is also equipped with a comb-shaped reinforcing steel positioning device located on both sides of the longitudinal rail. The comb-shaped reinforcing steel positioning device includes several reinforcing steel positioning support frames distributed in the vertical direction. The reinforcing steel positioning support frame includes a vertical pull rod and several horizontal support rods distributed in the vertical direction. One end of the horizontal support rod away from the longitudinal guide rail is connected to the vertical pull rod, and the other end is used to extend to the side of the side formwork support frame facing the longitudinal rail to support the longitudinal reinforcing steel bars. One horizontal support rod supports only one row of longitudinal reinforcing steel bars. One row of longitudinal reinforcing steel bars is supported on one horizontal support rod of all the reinforcing steel positioning support frames. At least one horizontal support rod is connected to the side formwork support frame through a sliding sleeve. In step A, the longitudinal reinforcing steel bars are supported by the horizontal support rods.

8. A method for manufacturing precast box girders according to claim 1 or 2, characterized in that, The pouring station is also equipped with a welding torch power supply structure, which includes a longitudinal slide rail, a longitudinal suspension cable, an electric welding machine, a bracket that can slide and be suspended on the longitudinal slide rail, and an electric welding machine input wire connected to the welding machine at one end. The electric welding machine is fixed on the bracket and has a positive output wire and a negative output wire. The end of the negative output wire is connected to a conductive block, and the positive output wire is connected to the welding torch. A suspension ring is fixed to the electric welding machine input wire, distributed along the extension direction of the electric welding machine input wire. The suspension ring is sleeved on the longitudinal suspension cable. In use, the other end of the electric welding machine input wire is connected to a power source to supply power to the electric welding machine. The electric welding machine has a current adjustment knob and a dial surrounding the current adjustment knob. The current adjustment knob has a pointer. The scale value on the dial of the welding machine, aligned with the pointer of the welding machine, is the output current value of the welding machine. The lower end of the bracket has a bracket knob and a dial surrounding the bracket knob. The bracket knob has a pointer, and the scale value on the dial aligned with the pointer is the same as the scale value on the dial of the welding machine. The bracket knob is connected to the current adjustment knob via a transmission mechanism. When the bracket knob rotates, it drives the current adjustment knob to rotate through the transmission mechanism. The angular velocity of the bracket knob during rotation is equal to the angular velocity of the current adjustment knob driven by the bracket knob. The welder can rotate to the bracket knob without using tools when performing welding operations at the pouring station. In step A, the steel reinforcement skeleton is welded using the welding torch power supply structure.

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