Prestressed construction method for simply supported box girder

Abstract

The present invention discloses a construction method for prestressing a simply supported box girder, which is used for prestressing the box girder. In the prestressing construction, first, the steel strand coil is cut into multiple steel strands of a specified length; then, the multiple steel strands are respectively passed through the holes on the comb beam plate, and the corresponding steel strands are marked according to the color of the holes; then, the front ends of the multiple steel strands are welded to form a steel strand bundle; the steel strand bundle is towed to pass through the prestressed duct; the steel strand bundle is tensioned according to a preset tension value; after the tensioning is completed, grouting is carried out into the prestressed duct according to a preset pressure value; finally, the beam end sealing operation is carried out on the parts of the steel strand bundle exposed at both ends of the prestressed duct. The operator can confirm whether the steel strand bundle in the prestressed duct is wound through the marks on the steel strands, and can accurately control the tension value and the grouting pressure value at the same time, so as to ensure the construction quality and effectively improve the construction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of prefabrication of bridge box girders, and particularly to a construction method for prestressing simply supported box girders. Background Art

[0002] Prestressed concrete structures show good effects in aspects such as reducing the self-weight of structures, improving seismic resistance, giving full play to the strength of materials, reducing project costs, improving the mechanical properties of structural members, and expanding the scope of use of reinforced concrete.

[0003] The prior art discloses a post-tensioning prestressing construction method for bridge box girders. This construction method includes the installation of bottom formwork and side formwork; steel bar binding; forming of prestressed ducts; threading of steel strand bundles after concrete pouring; installation of anchor fittings and jacks; tensioning using a steel strand bundle wedge anchorage system; and grouting after preparing cement mortar. The advantages of this construction method are that it can manufacture large bridge box girders and the technological steps are relatively simple. However, in this construction method, after the steel bars are inserted into the prestressed ducts, it is impossible to confirm whether the steel bars are intertwined with each other. If the steel bars are intertwined, it will cause uneven stress on the steel bars during the tensioning operation, thereby affecting the construction quality and construction efficiency.

[0004] Therefore, it is necessary to provide a new construction method for prestressing simply supported box girders to solve the above technical problems. Summary of the Invention

[0005] The main object of the present invention is to provide a construction method for prestressing simply supported box girders, aiming to solve the problem that in the existing prestressing construction operations, the steel strands are intertwined, which affects the construction quality and construction efficiency.

[0006] To achieve the above object, the construction method for prestressing simply supported box girders proposed by the present invention is used for prestressing construction of box girders. There are multiple prestressed ducts on the box girders. The construction method for prestressing simply supported box girders includes:

[0007] Cutting a steel strand coil into multiple steel strands of a specified length;

[0008] Threading the multiple steel strands one by one through the respective holes on the combing plate, and marking the corresponding steel strands according to the color of the holes;

[0009] When the front ends of the multiple steel strands pass through the holes on the combing plate, welding the front ends of the multiple steel strands to form a steel strand bundle;

[0010] Traction the steel strand bundle to make the steel strand bundle pass through the prestressed duct;

[0011] Tension the steel strand bundle according to a preset tension value;

[0012] Grout into the prestressed duct according to a preset pressure value;

[0013] The beam end sealing operation is carried out at the parts where the steel strand bundles are exposed at both ends of the prestressed channel.

[0014] Optionally, after the step of passing the plurality of steel strands through the holes on the combing plate one by one and marking the corresponding steel strands according to the colors of the holes, the following steps are included:

[0015] Install a U-shaped pull ring at the front end of the steel strand bundle;

[0016] Connect the guide rope to the U-shaped pull ring and use the guide rope to pull the steel strand bundle through the hole on the combing plate;

[0017] The steel strands are bundled with wire every 1m to 1.5m.

[0018] Optionally, the two adjacent box girders are respectively a first box girder and a second box girder, and the step of pulling the steel strand bundle to pass through the prestressed channel includes:

[0019] Install the steel strand bundle into the inner box of the first box beam through the reserved hole of the top plate of the first box beam;

[0020] Pass the guide cable through the prestressed channel of the second box girder;

[0021] Bending the steel strand bundle, extending the front end of the steel strand bundle through the manhole of the first box girder into the prestressed channel of the second box girder;

[0022] Pull the guide rope to make the steel strand bundle pass through the prestressed channel of the second box girder.

[0023] Optionally, after the step of installing the guide cable pulling steel strand bundle as a whole into the prestressed channel of the second box girder, the method further comprises:

[0024] The marks on each steel strand are used to determine whether each steel strand is twisted.

[0025] If any of the steel strands are twisted, pull out the steel strand bundle, straighten the twisted steel strands, and then insert the steel strand bundle into the prestressed channel;

[0026] If all the steel strands are free of twist, the step of tensioning the steel strand bundle according to the preset tensioning value is performed.

[0027] Optionally, the step of tensioning the steel strand bundle according to a preset tension value includes:

[0028] Anchor connectors are installed at both ends of the prestressed channel, and the anchor connectors are sleeved on the steel strand bundle;

[0029] Insert clips into the holes of the anchor connector to secure the strands;

[0030] Install limit plates on the outside of the anchor connector respectively;

[0031] Jack is installed on the outside of the limit plate respectively;

[0032] The tool anchor is installed on the outside of the jack;

[0033] Start the jack to tension the steel strand bundle;

[0034] Remove the tool anchor, jack and limit plate in sequence.

[0035] Optionally, after the step of starting the jack to tension the steel strand bundle, it includes:

[0036] Loosen the steel strands with slipped wires or broken wires one by one;

[0037] Replace the steel strands with slipped wires or broken wires with new steel strands;

[0038] Perform tension operation on the new steel strands;

[0039] Cut the steel strands outside the anchor connector so that the end of the steel strand bundle is 30 mm to 40 mm away from the anchor connector;

[0040] Seal the anchor connector with cement mortar.

[0041] Optionally, both ends of the prestressed duct are the grout outlet end and the grout inlet end respectively. The step of grouting into the prestressed duct according to the preset pressure value includes:

[0042] Clean the prestressed duct;

[0043] Install a transparent pipe at the grout outlet end of the prestressed duct. One end of the transparent pipe is communicated with the grout outlet end, and the other end of the transparent pipe is communicated with the intake pipe of the vacuum pump;

[0044] Connect the grout inlet end of the prestressed duct with the grout outlet of the grouting pump;

[0045] Check the sealing performance of the prestressed duct;

[0046] Keep the vacuum pump in the startup state and start the grouting pump to start grouting;

[0047] When the consistency of the cement mortar flowing out of the grout outlet is the same and the flow is smooth, hold the pressure for 3 minutes;

[0048] Close the valves of the grouting machine and the grouting end.

[0049] Optionally, the step of cleaning the prestressed duct includes:

[0050] Flush the prestressed duct with high-pressure water;

[0051] Blow out the moisture in the prestressed duct.

[0052] Optionally, the step of inspecting the tightness of the prestressed duct includes:

[0053] Open the valve at the grouting inlet end and close the valve at the grouting outlet end;

[0054] Turn on the vacuum pump;

[0055] When the vacuum degree is maintained at -0.06 to -0.08 Mpa, stop the pump for 1 minute and observe the pressure value.

[0056] Optionally, the step of performing the beam end sealing operation on the parts of the steel strand bundle exposed at both ends of the prestressed duct includes:

[0057] Remove the valves at the grouting end and the grouting outlet end;

[0058] Install the end formwork of the prestressed duct;

[0059] Pour concrete into the end formwork;

[0060] Remove the end formwork.

[0061] The simply supported box girder prestressing construction method proposed by the present invention is used for prestressing the box girder. In the prestressing construction, the operator first cuts the steel strand coil into multiple steel strands of a specified length; then passes the multiple steel strands through the respective holes on the combing plate one by one, and marks the corresponding steel strands according to the color of the holes, so as to judge whether the steel strands are twisted before the tensioning operation; then weld the front ends of the multiple steel strands to form a steel strand bundle, so as to ensure that the steel strand bundle will not shift or fall during the handling and threading process; tow the steel strand bundle to make the steel strand bundle pass through the prestressed duct, effectively solving the problem that the steel strand bundle cannot smoothly pass through the prestressed duct due to the excessive length and bending of the prestressed duct; tension the steel strand bundle according to the preset tensioning value; after the tensioning is completed, grout into the prestressed duct according to the preset pressure value; finally, perform the beam end sealing operation on the parts of the steel strand bundle exposed at both ends of the prestressed duct. By using the simply supported box girder prestressing construction method proposed by the present invention, the prestressing construction of all prestressed ducts on the box girder is completed, thereby completing the prestressing construction operation of the box girder. During the construction process, the operator can confirm whether the steel strand bundle in the prestressed duct is wound through the marks on the steel strands, and can accurately control the tensioning value and the grouting pressure value, thereby ensuring the construction quality and effectively improving the construction efficiency. Description of the Drawings

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0063] Figure 1 It is a schematic flow chart of the prestressed construction method for simply supported box girders in the embodiments of the present invention.

[0064] The realization of the object of the present invention, its functional features and advantages will be further described in conjunction with the embodiments and with reference to the drawings. Specific embodiments

[0065] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0066] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If this specific posture changes, the directional indications will also change accordingly.

[0067] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0068] In the present invention, unless otherwise clearly defined and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the premise that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or is impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0070] The present invention provides a construction method for prestressing simply supported box girders, aiming to solve the problem that the connection of the existing wall insulation system is not firm enough.

[0071] As Figure 1 shown, a construction method for prestressing simply supported box girders is used for prestressing the box girder. There are multiple prestressed ducts on the box girder. The characteristics of the construction method for prestressing simply supported box girders include:

[0072] Step S10: Cut the steel strand coil into multiple steel strands of a specified length;

[0073] Specifically, before cutting the material, the surface quality, diameter and mechanical properties of the steel strands should be carefully inspected. At the same time, the surface of the steel strands shall not be contaminated with substances such as oil stains and lubricants that affect the bonding force between the steel strands and concrete, and the steel strands shall not be corroded into visible pits. Slight floating rust is allowed. The steel strands should be cut in a straightened state. The cutting length of the steel strands is: the length of the prestressed duct + the length of the jacks at both ends + the thickness of the tool anchor plate + the safety length. Before cutting the steel strands, tie the cut ends at both ends with iron wire to prevent the steel strands from shifting and affecting the cutting length. When cutting, the steel strand coil should be kept vertical in the cutting rack, and the surrounding should be stuffed tightly with wooden boards. Pull out from the inner end of the steel strand coil, and then use a cutting saw blade for cutting, thus effectively avoiding the safety accident caused by the steel strands popping out. At the same time, it not only reduces the waste of steel strands but also ensures the quality of the steel strands.

[0074] Step S20: Pass the multiple steel strands through the holes on the combing plate one by one, and mark the corresponding steel strands according to the color of the holes;

[0075] Among them, the holes on the combing plate are correspondingly arranged with the holes on the anchor used during the tensioning operation, and the diameter of the holes on the combing plate is larger than the diameter of the holes on the anchor. Each horizontal row on the combing plate corresponds to a main color paint, and each hole in the horizontal row corresponds to a secondary color paint. Pass the front ends of the multiple steel strands through the holes on the combing plate one by one, and then mark the front ends of the steel strands passing through the holes according to the color of the holes respectively.

[0076] Step S30: When the front ends of the multiple steel strands pass through the holes on the combing plate, weld the front ends of the multiple steel strands to form a steel strand bundle;

[0077] Weld the front ends of multiple steel strands together to ensure that the steel strands will not shift or fall during the handling and threading processes, which is beneficial to reducing the difficulty of construction operations and improving work efficiency.

[0078] Step S40: Pull the steel strand bundle to make the steel strand bundle pass through the prestressed duct;

[0079] Step S50: Tension the steel strand bundle according to a preset tension value;

[0080] Step S60: Grout into the prestressed duct according to a preset pressure value;

[0081] Step S70: Perform capping operations on the beam body at the parts where the steel strand bundle is exposed at both ends of the prestressed duct.

[0082] The simply supported box girder prestressed construction method proposed by the present invention can confirm whether the steel strand bundle in the prestressed duct is wound or crossed by observing the marked positions on the steel strands, thereby preventing uneven stress on the steel strands during the tensioning operation caused by improper threading of the steel strands. At the same time, the tension value and grouting pressure value can be accurately controlled during the construction process, thereby ensuring the construction quality and effectively improving the construction efficiency. The bridge includes multiple box girders. Each box girder is provided with multiple prestressed ducts. The prestressed construction of the multiple prestressed ducts is carried out in two batches. After the first batch of steel strands are tensioned and the beam is lowered, the second batch of steel strands are tensioned. After the first batch of steel strands are tensioned, the beam body of the box girder can bear its own weight. After the box girder is placed on the pier, the first batch of steel strands are lifted upward under the action of the beam body weight and their own stress, and then the second batch of steel strands are tensioned. The second batch of steel strands and the first batch of steel strands jointly bear the beam body weight, thereby reducing the pressure borne by the first batch of steel strands and making the steel strand bundle in the prestressed duct stress evenly, thereby ensuring the stability of the prestressed structure of the box girder.

[0083] In one embodiment, after the above step S20, the following steps are included:

[0084] Step S31: Install a U-shaped pull ring at the front end of the steel strand bundle;

[0085] Step S32: Connect the guide cable to the U-shaped pull ring and pull the steel strand bundle through the holes on the combing plate through the guide cable;

[0086] Step S32: Tie each steel strand with iron wire every 1 m to 1.5 m.

[0087] In this embodiment, the operator installs a U-shaped pull ring at the front end of the steel strand bundle to facilitate the connection of the guiding cable. The guiding cable pulls the steel strand bundle through the combing plate, so as to smoothly comb the steel strands that are intertwined and crossed in the steel strand bundle according to the hole positions on the combing plate. When the rear end of the steel strand bundle is about 2 m away from the combing plate, stop the traction, and mark the rear end of the steel strand corresponding to the color mark of the hole on the combing plate, so as to observe whether the steel strands are crossed and twisted after the steel strand bundle is inserted into the prestressed duct. After the steel strand bundle passes through the combing plate as a whole, tie each steel strand with iron wire every 1 m to 5 m to prevent the steel strands from shifting and slipping during transportation and threading operations.

[0088] Further, two adjacent box girders are respectively the first box girder and the second box girder. In the embodiment of the present invention, the steps of step S40 include:

[0089] Step S41: Load the steel strand bundle into the inner box of the first box girder through the reserved hole in the top plate of the first box girder;

[0090] Step S42: Pass the guiding cable through the prestressed duct of the second box girder;

[0091] Step S43: Bend the steel strand bundle, and extend the front end of the steel strand bundle into the prestressed duct of the second box girder through the manhole of the first box girder;

[0092] Step S44: Pull the guiding cable to make the steel strand bundle pass through the prestressed duct of the second box girder.

[0093] Inside the box girder, there is an inner box with openings at both ends, which are manholes for operators to pass through. On both sides of the top of the box girder, there are flanges. The top plate of the box girder is provided with reserved holes for the steel strand bundle to pass through, and both the side wall and the bottom plate of the box girder are provided with a plurality of prestressed ducts. In the prestressed construction of the box girder, two adjacent box girders are respectively the first box girder and the second box girder. After loading the steel strand bundle into the inner box of the first box girder through the reserved hole of the first box girder, one end of the guide cable is passed through the prestressed duct of the second box girder, and the other end of the guide cable is connected to the front end of the steel strand bundle. Then, the steel strand bundle is bent so that the front end of the steel strand bundle in the inner box of the first box girder extends into the prestressed duct of the second box girder. Then, the guide cable is pulled from the end of the prestressed duct of the second box girder far away from the first box girder, and the guide cable drives the steel strand bundle to pass through the prestressed duct of the second box girder, so that the front end of the steel strand bundle is exposed 1m - 2m from the prestressed duct. Thus, a steel strand bundle is inserted into one prestressed duct, and all the prestressed ducts on the box girder are inserted with steel strand bundles according to the above method. The present invention utilizes the inner box of adjacent box girders as an operation platform, which is beneficial to bending the front end of the steel strand bundle to align with the prestressed ducts on the side wall and the bottom plate of the box girder, reducing the difficulty of construction operations. By adopting the method of guiding the cable to pull the steel strand bundle into the prestressed duct, it can prevent damage to the inner wall of the prestressed duct when the steel strand bundle passes through the prestressed duct, and save the time spent on inserting the steel strand bundle into the prestressed duct, improving the operation efficiency.

[0094] Furthermore, in the present invention, after step S44, it further includes:

[0095] Step S45: Judging whether each steel strand is twisted by the marks on each steel strand;

[0096] Step S46: If any steel strand is twisted, pull out the steel strand bundle, straighten the twisted steel strand and then insert the steel strand bundle into the prestressed duct;

[0097] Step S46: If all steel strands are not twisted, execute step S50.

[0098] Specifically, after the steel strand bundle passes through the prestressed duct, observe the color marks at both ends of the steel strand bundle. If the positions of the color marks at both ends of the steel strand bundle are the same, the steel strand is not twisted, and then execute step S50; if the positions of the color marks at both ends of the steel strand bundle are different, the steel strand is twisted. At this time, the steel strand bundle should be pulled out, the twisted steel strand should be straightened and then the steel strand bundle should be inserted into the prestressed duct again. By observing the color marks at both ends of the steel strand bundle, it can be accurately judged whether the steel strand bundle in the prestressed duct is twisted, thus preventing the situation that the steel strands are unevenly stressed during the tensioning construction due to the steel strands being wound around each other, which is beneficial to improving the construction quality of the prestressed structure.

[0099] Step S50 in the present invention includes:

[0100] Step S51: Install anchor connectors at both ends of the prestressed duct, and the anchor connectors are sleeved on the steel strand bundle;

[0101] Step S52: Insert wedge-shaped keys into the holes of the anchor connectors to fix the steel strands;

[0102] Step S53: Install limit plates on the outside of the anchor connectors respectively;

[0103] Step S54: Install jacks on the outside of the limit plates respectively;

[0104] Step S55: Install tool anchors on the outside of the jacks;

[0105] Step S56: Start the jack to tension the steel strand bundle;

[0106] Step S57: Remove the tool anchor, jack and limit plate in sequence.

[0107] In the tensioning operation of the steel strand bundle, first install anchor connectors at both ends of the prestressed duct. The anchor connectors are provided with holes for the steel strand bundle to pass through, and the anchor connectors are sleeved on the steel strand bundle. Then insert wedge-shaped keys into the holes of the anchor connectors respectively. The steel strands in the holes of the anchor connectors are clamped in the wedge-shaped keys. Then install the limit plate, jack and tool anchor in sequence on the outside of the anchor connectors. Before tensioning, it is necessary to calibrate the jack and the oil pressure gauge. Use the regression equation set by the computer to calculate the tensile force of each tensioning stage of the steel strand, and then visually and effectively reflect it on the corresponding oil pressure gauge value to form tensioning data. Relevant personnel can download and collect it, and at the same time compare whether the theoretical elongation calculated by the computer is consistent with the data provided by the design drawing. During the tensioning process, double control is carried out with the tensile force and elongation value as indicators, with the tensile force as the main control index and the elongation as the check. This not only realizes the precise automatic control of prestress, but also improves the accuracy and authenticity of the tensioning value. After tensioning, remove the tool anchor, jack and limit plate in sequence.

[0108] Before the first batch of steel strands of the box girder are tensioned, the box girder is in a suspended state. The first batch of steel strands are tensioned in sequence according to the above tensioning operation method, and the box girder arches upward, so that the bearing capacity is enhanced, and part of the self-weight of the box girder is borne by the beam body. After the first batch of steel strands are tensioned, the box girder is placed on the pier and then the second batch of steel strands are tensioned.

[0109] Further, after the steps of step S50 include:

[0110] Step S58: Loosen the tension of the steel strands with slippage or breakage one by one;

[0111] Step S58: Replace the steel strands with slippage or breakage with new steel strands;

[0112] Step S58: Perform tensioning operation on the new steel strand;

[0113] Step S58: Cut the steel strand outside the anchor connector so that the end of the steel strand is 30 mm to 40 mm away from the anchor connector;

[0114] Seal the anchor connector with cement mortar.

[0115] When wire slippage and wire breakage occur during the tensioning operation, the slippage or broken wire of the steel strand should be replaced. First, use a jack to tension a single steel strand to a state where the working wedge can be loosened, then withdraw the working wedge, and finally unload the jack to make the steel strand in a relaxed state; after the entire bundle of steel strands is gradually released one by one, the entire bundle of steel strands is pulled out; use a new steel strand to replace the slippage or broken wire of the steel strand, and then perform tensioning operation on the new steel strand. In addition, when wire slippage occurs, it is also necessary to check the wear condition of the wedge. Severely damaged wedges cannot be used continuously. After replacing the slippage or broken wire of the steel strand, seal the anchor connector with cement mortar to ensure the sealing of the prestressed duct and prevent the steel strand from rusting or corroding; cut off the steel strand outside the anchor connector, and the end of the steel strand is 30 mm to 40 mm away from the anchor connector for subsequent end sealing operation.

[0116] For the convenience of construction and improvement of construction progress,

[0117] Based on the above embodiments, both ends of the prestressed duct are the grout outlet end and the grout inlet end respectively. Step S60 in the present invention includes:

[0118] Step S61: Clean the prestressed duct;

[0119] Step S62: Install a transparent tube at the grout outlet end of the prestressed duct. One end of the transparent tube is communicated with the grout outlet end, and the other end of the transparent tube is communicated with the intake pipe of the vacuum pump;

[0120] Step S63: Communicate the grout inlet end of the prestressed duct with the grout outlet of the grouting pump;

[0121] Step S64: Check the sealing of the prestressed duct;

[0122] Step S65: Keep the vacuum pump in the startup state and start grouting by opening the grouting pump;

[0123] Step S66: When the consistency of the cement slurry flowing out of the grout outlet is the same and the flow is smooth, hold the pressure for 3 minutes;

[0124] Step S67: Close the grouting machine and the valve at the grouting end.

[0125] After tensioning, it is advisable to carry out the pipeline grouting operation within 48 hours. Specifically, valves are provided at both the slurry inlet end and the slurry outlet end of the prestressed duct. First, clean the prestressed duct thoroughly; then install a transparent tube at the slurry outlet end of the prestressed duct. One end of the transparent tube is connected to the slurry outlet end, and the other end is connected to the intake pipe of the vacuum pump; connect the slurry inlet end of the prestressed duct to the slurry outlet of the grouting pump; after checking the tightness of the prestressed duct, keep the vacuum pump running, start the grouting pump. When the consistency of the cement slurry flowing out of the slurry outlet is the same and the flow is smooth, maintain the pressure at 0.6 Mpa, hold the pressure for 3 minutes, then close the grouting machine and the valve at the grouting end to complete the grouting. It should be noted that when the ambient temperature or the temperature of the beam body concrete is lower than 5°C, grouting shall not be carried out, and the time from mixing the materials to injecting them into the duct should not exceed 40 minutes to ensure that the cement slurry remains in a flowing state during the grouting process. Intelligent grouting equipment is used in the grouting operation, which is convenient to operate, accurate in measurement, reduces the working intensity of the operators, has a high degree of automation, and can record the information and data during the grouting process in real time, thus realizing controllable quality data and providing guarantee for the quality of the prestressed construction operation of the box girder.

[0126] Among them, in the embodiment of the present invention, step S61 includes:

[0127] Step S611: Flush the prestressed duct with high-pressure water;

[0128] Step S612: Blow out the moisture in the prestressed duct.

[0129] In a preferred embodiment, before the grouting operation, it is necessary to flush the duct with high-pressure water to wash away the sundries and moisten the inner wall of the duct, preventing the dry duct wall from absorbing the moisture in the cement slurry and reducing the fluidity of the slurry, which affects the grouting quality and efficiency. After cleaning, the accumulated water in the duct can be blown out with high-pressure air, so that not only can the inner wall of the prestressed duct be kept moist, but also the influence of the accumulated water in the prestressed duct on the grouting quality can be avoided, effectively improving the construction quality and construction efficiency of the prestressed structure.

[0130] Step S64 includes:

[0131] Step S641: Open the vacuum pump and the valve at the slurry inlet end, and close the valve at the slurry outlet end;

[0132] Step S642: Stop the pump for 1 minute when the vacuum degree is maintained at -0.06 to -0.08 Mpa and observe the pressure value.

[0133] When checking the tightness of the prestressed duct, first turn on the vacuum pump, open the valve at the grout inlet end, and close the valve at the grout outlet end; observe the reading of the pressure gauge of the vacuum pump. When the vacuum degree is maintained at about -0.06 to -0.08 Mpa, stop the pump for about 1 minute, and then observe the reading of the pressure gauge again. If the reading of the pressure gauge remains unchanged, it indicates that the tightness of the prestressed duct is good. If the reading of the pressure gauge changes, there is a leak point in the prestressed duct. After eliminating the leak point, check the tightness of the prestressed duct in sequence again. After passing the inspection, the grouting operation can be started. This process can effectively ensure the tightness of the prestressed duct, prevent problems such as unstable pressure in the prestressed duct and leakage of cement slurry due to the unsealed prestressed duct during the grouting operation, and is beneficial to ensuring a good construction environment for the grouting operation.

[0134] Step S70 includes:

[0135] Step S71: Remove the valves at the grouting end and the grout outlet end;

[0136] Step S72: Install the end formwork of the prestressed duct;

[0137] Step S73: Pour concrete into the end formwork;

[0138] Step S74: Remove the end formwork.

[0139] After the prestressed duct grouting is completed, after checking that there is no situation of incomplete filling of the cement slurry in the prestressed duct, the valves at the grouting end and the grout outlet end can be removed. After cleaning the valves at the grouting end and the grout outlet end, apply an appropriate amount of butter and they can be reused, which is beneficial to saving construction costs; clean the surface of the cement mortar layer of the anchor connector, and chisel the surface of the original beam body concrete on the side of the anchor hole to expose the solid stone surface; one end of the short steel bar is provided with a hook, and the other end is provided with a thread. The threaded end of the short steel bar is inserted into the bolt hole on the anchor connector and is threadedly connected to the anchor connector; use the short steel bar to tie the steel bar skeleton at the anchor connector; install the end formwork on the outside of the steel bar skeleton. The end formwork uses bamboo plywood and square timbers, and double-sided tape is pasted around to avoid grout leakage; then pour concrete into the end formwork. The concrete should be vibrated strongly, and it is required that the concrete is dense and has no honeycombs or pockmarks. The concrete in the end formwork should be flush with the beam end face, and the offset of the concrete surface after sealing and the beam body concrete should not exceed 2 mm; remove the end formwork after the concrete strength reaches the standard and carry out curing of the end concrete; finally, apply a 1.5-mm-thick polyurethane waterproof coating on the surface of the bottom plate and web of the concrete beam end to enhance the waterproof performance. The beam end sealing operation can not only further seal the prestressed duct, avoid corrosion and rust of the steel strand due to the external environment, but also has a certain aesthetic appearance, and at the same time can enhance the waterproof performance of the beam end.

[0140] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A prestressed construction method for simply supported box girders, which is used for prestressed construction of box girders. There are multiple prestressed ducts provided on the box girders, and it is characterized in that, The prestressed construction method of the simply supported box beam comprises: Cut the steel strand drum into multiple steel strands of specified length; Pass multiple steel strands through the holes on the combing plate one by one, and mark the front ends of the steel strands passing through the holes according to the colors of the holes; When the front ends of the plurality of steel strands pass through the holes on the bundle combing plate, the front ends of the plurality of steel strands are welded to form a steel strand bundle; When the rear end of the steel strand bundle is 2m away from the combing plate, stop pulling and mark the rear end of the steel strand according to the color of the hole on the combing plate; Pulling the steel strand bundle to make it pass through the prestressing hole; tensioning the steel strand bundle according to a preset tension value; Grouting into the prestressed duct according to the preset pressure value; Carry out beam end sealing operation at the parts where the steel strands are exposed at both ends of the prestressed channel; Each horizontal row on the combing plate corresponds to a primary color paint, and each channel in the horizontal row corresponds to a secondary color paint.

2. The prestressed construction method of the simply supported box girder according to claim 1, characterized in that The step of passing the plurality of steel strands through the holes on the combing plate one by one and marking the corresponding steel strands according to the colors of the holes comprises: Install a U-shaped pull ring at the front end of the steel strand bundle; Connect the guide rope to the U-shaped pull ring and use the guide rope to pull the steel strand bundle through the hole on the combing plate; Each steel strand is bundled with wire every 1m~1.5m.

3. The simply supported box girder prestressing construction method according to claim 2, characterized in that, The two adjacent box beams are respectively a first box beam and a second box beam, and the step of pulling the steel strand bundle so that the steel strand bundle passes through the prestressed channel includes: Install the steel strand bundle into the inner box of the first box beam through the reserved hole of the top plate of the first box beam; Pass the guide cable through the prestressed channel of the second box girder; Bending the steel strand bundle, extending the front end of the steel strand bundle through the manhole of the first box girder into the prestressed channel of the second box girder; Pull the guide rope to make the steel strand bundle pass through the prestressed channel of the second box girder.

4. The prestressed construction method of the simply supported box girder according to claim 3, characterized in that, After the step of pulling the guide rope to make the steel strand bundle pass through the prestressed channel of the second box girder, the method further includes: Determine whether each steel strand is twisted by the marks on each steel strand; If any of the steel strands are twisted, pull out the steel strand bundle, straighten the twisted steel strands, and then insert the steel strand bundle into the prestressed channel; If all the steel strands are free of twist, the step of tensioning the steel strand bundle according to the preset tensioning value is performed.

5. The prestressed construction method of the simply supported box girder according to claim 4, characterized in that, The step of tensioning the steel strand bundle according to a preset tension value comprises: Anchor connectors are installed at both ends of the prestressed channel, and the anchor connectors are sleeved on the steel strand bundle; Insert clips into the holes of the anchor connector to secure the strands; Install limit plates on the outside of the anchor connector respectively; Install jacks on the outside of the limit plates respectively; Install tool anchors on the outside of the jack; Open the jack and tension the steel strand bundle; Remove the tool anchor, jack and limit plate in sequence.

6. The prestressed construction method for simply supported box girders according to claim 5, characterized in that, The step of opening the jack and tensioning the steel strand bundle includes: Unwind the steel strands that have slipped or broken wires one by one; Use new steel strands to replace stripped or broken strands; Carry out tensioning operation on new steel strands; Cut the steel strands outside the anchor connector so that the end of the steel strand bundle is 30mm to 40mm away from the anchor connector; The anchor connector is sealed with cement mortar.

7. The prestressed construction method of the simply supported box girder according to any one of claims 1 to 6, characterized in that, The two ends of the prestressed duct are respectively a slurry outlet end and a slurry inlet end, and the step of grouting the prestressed duct according to a preset pressure value includes: Clean the prestressed duct; Install a transparent tube at the grout outlet end of the prestressed duct. One end of the transparent tube is communicated with the grout outlet end, and the other end of the transparent tube is communicated with the intake pipe of the vacuum pump; Connect the grout inlet end of the prestressed duct to the grout outlet of the grouting pump; Check the tightness of the prestressed duct; Keep the vacuum pump running and start grouting by turning on the grouting pump; When the consistency of the cement grout flowing out of the grout outlet is uniform and the flow is smooth, maintain the pressure for 3 minutes; Close the valves of the grouting machine and the grout outlet end.

8. The prestressed construction method of the simply supported box girder according to claim 7, characterized in that, The steps for cleaning the prestressed duct include: Flush the prestressed duct with high-pressure water; Blow out the moisture in the prestressed duct.

9. The simply supported box girder prestressed construction method according to claim 7, characterized in that, The steps for checking the tightness of the prestressed duct include: Open the valve at the grout inlet end and close the valve at the grout outlet end; Turn on the vacuum pump; When the vacuum degree is maintained at -0.06 to -0.08 Mpa, stop the pump for 1 minute and observe the pressure value.

10. The simply supported box girder prestressed construction method according to claim 7, characterized in that, The steps for performing the beam end sealing operation on the parts of the steel strand bundle exposed at both ends of the prestressed duct include: Remove the valves at the grout outlet end and the grout inlet end; Install the end formwork of the prestressed duct; Pour concrete into the end formwork; Remove the end formwork.

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