Construction method of prestressed wet joint of beam
By pre-adding and welding U-shaped reinforcing bars at the wet joint and using hydraulic jacks to create prestress, the problem of easy cracking at the interface between new and old concrete was solved, achieving efficient, standardized construction and improved safety of wet joints.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI UNIVERSITY OF ARCHITECTURE
- Filing Date
- 2024-01-24
- Publication Date
- 2026-06-30
AI Technical Summary
In the current construction of wet joints for precast box girders, the interface between new and old concrete is prone to cracking, leading to safety hazards. Existing reinforcement methods may damage the physical properties of the beam or are inefficient.
Hydraulic jacks are used to pre-stress U-shaped bars, which are then pulled and welded using specialized construction equipment to ensure that the concrete at the wet joint solidifies under pressure and prevents cracking.
It enables efficient and standardized construction of wet joints, avoids cracking at the interface between new and old concrete, and improves construction speed and safety.
Smart Images
Figure CN117802905B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of construction technology for preventing cracking of concrete wet joints in beam splicing. Background Technology
[0002] In the construction process of precast box girders, the treatment method for wet joints involves welding or binding short reinforcing bars to connect the lapped bars on both sides of the beam. This transitional connection of short reinforcing bars creates a reinforcing mesh between adjacent beams. Formwork is then erected in this area, creating a cast-in-place zone between the adjacent box girders, which is then filled with concrete to form the wet joint connection. In this process, C50 concrete is typically used for the wet joint, and the reinforcing bars in the mesh are in a natural, non-tensioned state.
[0003] The wet joint post-casting construction process has the advantage of simple construction, but it also has the quality problem of cracks easily appearing after formwork removal. When cracks appear, rainwater and other substances can seep into the cracks and further corrode the internal steel bars. Coupled with other defects such as freezing, the wet joint poses a safety hazard. Therefore, it is necessary to address the cracking hazard at this wet joint.
[0004] The reasons for the appearance of cracks in wet joints during later operation are analyzed as follows:
[0005] 1. Shrinkage and creep of concrete at wet joints: Since wet joints are a secondary pouring process, a certain amount of shrinkage will occur. The existing treatment process is to add micro-expansion agents or micro-expansion additives to the cast-in-place concrete. Even so, the cracking problem cannot be solved.
[0006] 2. Cracking at the interface between the old and new concrete: Due to the inherently poor bonding strength at the roughened surface and the fact that the beam itself is in a suspended state, under the combined effects of settlement, wind load, vehicle load, and self-weight, the interface between the old and new concrete at the wet joint and the beam becomes the weakest link in the cracking process, which is caused by torque and overturning force.
[0007] 3. After the old concrete has hardened, the cement paste layer at the interface between the old and new concrete acts as a bond. If this cement paste layer has dried before the new concrete is poured, the bond strength will decrease. This could be due to excessively long construction intervals, a dry environment, or inadequate protective measures. Temperature changes after the new concrete is poured may also affect the bond strength at the interface. Significant temperature changes may cause stress concentration at the interface, leading to cracking or detachment. The bond between the old and new concrete may not be strong enough, resulting in cracks.
[0008] One solution to the problem of cracks in wet joints is to use ultra-high strength concrete (UHPC) as cast-in-place concrete to improve the crack resistance of the wet joint itself. For example, the solution disclosed in CN117371232A describes that the wet joint specimen consists of ordinary concrete (NSC) precast sections at both ends and an ultra-high strength concrete (UHPC) wet joint in the middle.
[0009] Secondly, the use of prestressed steel strands for auxiliary pull-out between the old and new bridges constitutes a secondary reinforcement project. For example, CN117051728A uses prestressed steel strands on both the old and new T-beams, along with diaphragms and prestressed steel bars, increasing the interlocking force of the bridge concrete and enhancing its load-bearing capacity; the applied prestress generates compressive stress on the lower part of the flange plate. However, this process requires drilling holes in the flange plates of both the old and new beams, which is a destructive operation that reduces the physical properties of the beams themselves, requiring re-evaluation. Furthermore, in this structure, to increase crack resistance and pull-out strength, the prestressed steel bars create lateral tensile stress on the flange plates, further damaging the beam structure itself.
[0010] Thirdly, special concrete with shrinkage compensation function is used in the construction of wet joints. For example, CN219430563U discloses a scheme in which shrinkage-compensating concrete is poured between the tongue and groove of the original cast-in-place bridge deck and the tongue and groove of the widened cast-in-place bridge deck. This scheme enhances the crack resistance of the wet joint itself, but cracking still exists at the interface between the old and new concrete.
[0011] Based on the above, the present invention is based on the wet joint itself, without relying on other auxiliary secondary reinforcement projects, and can effectively solve the problem of cracking at the interface between new and old concrete and the wet joint itself. Summary of the Invention
[0012] The purpose of this invention is to provide a construction method for prestressed wet joints in beams, which solves the problem of cracking at the interface between new and old concrete and at the wet joint itself.
[0013] The technical solution adopted by this invention to solve its technical problem is as follows:
[0014] A method for constructing prestressed wet joints in beams, characterized by the following steps in sequence:
[0015] S1: Construction preparation: Clean and roughen the sides of the beam at the wet joint to ensure there is no debris, dust, or / and oil. Determine and mark the location and width of the wet joint according to the design requirements. Cut the edge of the wet joint according to the markings to ensure the straightness and verticality of the wet joint. Based on the width and depth of the wet joint, support the bottom and end faces of the wet joint with formwork. There is a pouring cavity between the formwork and the beam. During the formwork support process, reserve space for hydraulic jack support at both ends of the wet joint. This hydraulic jack support space is located outside the pouring space. Finally, weld one or more pairs of U-shaped bars near the end formwork. This welding keeps the width of the wet joint between the beams fixed.
[0016] S2: Use hydraulic jacks to open up the support space outside the pouring space. By applying hydraulic load to the hydraulic jacks, the welded U-shaped bars are pulled out. In this state, the welded U-shaped bars at both ends of the wet joint have a tensile stress value of N.
[0017] S3: Place the specialized construction device at the starting end of the wet joint construction, spanning the beams on both sides of the wet joint. Insert the pin of the hydraulic puller in the specialized construction device into the socket formed by two U-shaped bars. The hydraulic puller pulls out the U-shaped bars. During this process, the U-shaped bars are stretched in the microscopic direction, forming tensile stress. Maintain the tensile stress and use a welding machine to perform welding operations. After welding is completed, the hydraulic puller is released and the pin is pulled out from the socket, completing the welding of a pair of U-shaped bars. Then move the specialized construction device along the length of the beam, moving it one standard distance unit. This standard distance unit refers to the distance between adjacent U-shaped bars. Perform cold pulling and welding on the next pair of U-shaped bars. Continue in this manner to complete the cold pulling and welding of the remaining U-shaped bars. During this process, according to calculations, for every n pairs of U-shaped bars welded, gradually increase the hydraulic loading force of the hydraulic jack to keep the tensile stress between each pair of U-shaped bars at the value N, until all U-shaped bars are stretched and welded.
[0018] S4: Pour concrete into the pouring space and vibrate it. After completion, observe the concrete strength during the solidification process. When the solidification strength reaches the design strength, remove the hydraulic jacks and continue curing until it is qualified. Then remove the formwork to complete the construction of a standard section of beam wet joint.
[0019] Furthermore, the cold drawing and welding process is calculated as follows: Based on the bridge data, the required force F for cold drawing, the drawing length L1, the welding starting position and distance L2, the distance L5 between two adjacent pairs of U-shaped ribs, and the initial vertical distance L3 and horizontal distance L4 of the hydraulic puller from the U-shaped ribs are determined. These data are then input into the central control module. Based on the input data and the robotic arm's own moving speed V1, the central control module calculates the following: the time from the start of the hydraulic puller's operation to entering the U-shaped rib is T1 = (L3 + L4) / V1; the hydraulic puller's cold drawing process runs at a speed of V2, taking T2 = L1 / V2; then, the welding robotic arm, after calculation, moves downwards at a speed of V1 until it is parallel to the upper side of the U-shaped rib, and then moves to the welding point, a total distance of L6, taking a total time of T3 = L6 / V1; then, it welds at a speed of V3, taking T4 = L2 / V3; after welding, the hydraulic puller closes tightly, taking T5; then the instrument returns to its initial position; the time for processing a set of U-shaped ribs in the wet joint is T = 2T1 + T2 + 2T3 + T4 + T5; after a pair of U-shaped ribs is processed, the movable gantry machine tool moves at a speed of V4, so the time to move to the next pair of U-shaped ribs after one set of construction is T6 = L5 / V4.
[0020] Furthermore, for every n pairs of U-shaped ribs cold-drawn and welded, the hydraulic jack increases the hydraulic loading force by 0.05 tons.
[0021] Furthermore, the paired U-shaped ribs are welded together using short ribs.
[0022] Furthermore, the specialized construction device includes a gantry frame, two robotic arms, and a hydraulic puller and a welding torch mounted on the robotic arms. The gantry frame is formed by welding horizontal and vertical steel pipes and is arranged to span the wet joint. At the two lower ends of the gantry frame are traveling mechanisms. A hydraulic station and an electrical control box are installed on the small platform of the traveling mechanism. The two robotic arms are suspended and mounted on the crossbeam of the gantry frame. A hydraulic puller is installed at the lower end of one robotic arm. The hydraulic puller acts on the pulling point of the U-shaped rib from one side. This action is based on a visual tracking function. A welding torch is installed at the lower end of the other robotic arm. The welding torch performs welding operations on the overlapping section of the two U-shaped ribs from the other side. The mechanical action of visual recognition and synchronous pulling and welding is realized through a visual tracking system.
[0023] Furthermore, the visual recognition and welding point location determination are as follows: Before construction begins, the vertical distance between the robotic arm and the overlapping area of the U-shaped ribs is measured using a plumb line, and the horizontal distance is measured using a distance measuring instrument. Since the downward and translational speeds of the robotic arm are fixed, the robotic arm can precisely construct at the overlapping position of the U-shaped ribs by first moving vertically and then horizontally. Both robotic arms operate on the same principle. Knowing the moving speed of the robotic arm, the required horizontal and vertical distances of movement are measured before construction begins. This data is input into the device, which can then calculate the time required for each step from the start of construction to the completion of a set of U-shaped ribs.
[0024] Furthermore, the hydraulic puller consists of a hydraulic clamp body, clamp jaws, and a pin installed in the clamp jaws, wherein the pin is fixed at the outermost end of the opening of the clamp jaws, and the pin engages with the U-shaped rib.
[0025] Furthermore, the robotic arm is an articulated robotic arm with six-axis motion and equipped with autonomous learning, active grasping, picking functions, force sensors, and visual tracking functions. It can intelligently identify, locate, and weld welding points, as well as intelligently identify, locate, and stretch pulling points.
[0026] Furthermore, the cross-section of the pin is a horseshoe-shaped cross-section, a semi-circular cross-section, or a circular cross-section.
[0027] Furthermore, the hydraulic jack is connected to a crossbeam via a connector, and the two ends of the crossbeam are supported on the beams on both sides.
[0028] The beneficial effects of the present invention are: 1. The present invention can achieve mechanized construction by using a puller and a welding robotic arm in combination, making the construction of wet joints more standardized.
[0029] 2. The present invention enables continuous construction. After welding a section of wet joint, the construction device can move to the next unprocessed wet joint section.
[0030] 3. The drawing and welding robotic arms are equipped with visual recognition functions. After the basic expansion distance and welding length of the welding robotic arm are set in the program, the expansion and welding can start intelligently.
[0031] 4. If problems such as failure to expand or failure to weld occur during the construction process, the present invention can provide feedback to the information processing device for real-time adjustment of the construction process.
[0032] It has a wide range of applications, and can be used in both new bridge construction projects and reconstruction and expansion projects. Attached Figure Description
[0033] Figure 1 This is a schematic diagram before the box girder is spliced.
[0034] Figure 2 This is a schematic diagram of the box girder after it has been lapped.
[0035] Figure 3 This is a schematic diagram of the expansion of a hydraulic puller.
[0036] Figure 4 This is a schematic diagram of the working state of the present invention.
[0037] Figure 5 for Figure 4 Enlarged view of a portion of the image.
[0038] Figure 6 for Figure 5 Cross-sectional view of the working face.
[0039] Figure 7 This is a schematic diagram of the expansion process.
[0040] Figure 8 This is a structural diagram of a hydraulic puller.
[0041] Figure 9 This is a structural diagram of a welding robotic arm.
[0042] Figure 10 for Figure 7 Another state (reverse).
[0043] In the picture:
[0044] 00 Beam body, 01 Bottom formwork, 02 End formwork, 03 Cast-in-place cavity, 04 Hydraulic jack, 05 U-shaped reinforcement.
[0045] 100 Specialized construction equipment, 110 Gantry crane, 120 Robotic arm, 130 Hydraulic puller, 131 Hydraulic clamp body, 132 Jaw, 133 Pin, 140 Welding torch, 150 Traveling mechanism, 160 Hydraulic station and electrical control box. Detailed Implementation
[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0047] The construction method, which differs most significantly from traditional methods, is based on... Figures 1 to 3In the construction process, especially in the wet joint of two adjacent box girders, hydraulic jacks are pre-installed. Prestress is then applied to the connecting bars (U-shaped bars) on both sides of the two box girders. During the process of applying reverse tensile stress to the connecting bars on both sides, the hydraulic jacks act as a reaction frame, keeping the width of the wet joint stable. Another advantage of using hydraulic jacks here is their rapid assembly and disassembly; specifically, they can be disassembled after depressurization, improving construction speed. It should be noted that the hydraulic jacks are positioned on the outside of the formwork. The reinforcement details of the wet joint specimen are as follows: Figure 6 As shown, the U-shaped bars (main bars) are made of HRB400 grade steel bars with a diameter of 12mm; the radius of the U-shape is 10cm. The two U-shaped bars partially overlap to form a closed U-shaped track outline. This overlapping part is also the operation point for applying the pulling force. Therefore, the force application point in the hydraulic puller that needs to apply tensile stress is a horseshoe-shaped cross-section, a semi-circular cross-section, or a circular cross-section. The prestressing is applied using a dedicated hydraulic puller. Simultaneously, welding is performed at the lap joints of the connecting bars after the prestressing is applied, placing the connecting bars (U-shaped bars) between the two box girders in a stretched state with tensile stress. This tensile stress is maintained through welding. During this process, cast-in-place concrete is poured rapidly. After pouring, as the concrete solidifies, when the solidification strength reaches the design strength (hardness reaches 85%-90% of the design hardness), the hydraulic jack assembly (if necessary) is removed to release the prestress. This release process applies lateral compressive stress (extrusion) to the concrete at the wet joint. Because the concrete in the wet joint is under pressure, cracks in the wet joint concrete are prevented later. Furthermore, the connecting bars retain some tensile stress during this process, giving the wet joint prestress and improving crack prevention.
[0048] The longitudinally positioned wet joint area to be constructed is divided into sections for construction or poured as a whole. During either section or whole-section construction, formwork support is required. Space must be reserved for the installation of hydraulic jacks during the support process. (Refer to...) Figure 5 .
[0049] A specialized construction device 100 is provided, which is an overall gantry structure including a gantry 110, two robotic arms 120, and hydraulic pullers 130 and welding torches 140 mounted on the robotic arms. The gantry 110 is formed by welding horizontal and vertical steel pipes, arranged across wet joints, providing sufficient safety. At the two lower ends of the gantry 110 are traveling mechanisms 150, which are wheeled and can be moved using electric wheels or manual pushing. A small platform is formed on the traveling mechanism, and a hydraulic station and an electrical control box 160 are installed on this platform. By fixing the hydraulic and electrical control units to the small platform, a mobile electromechanical specialized device is formed.
[0050] refer to Figure 8 An optional structure is provided in which the hydraulic puller 130 consists of a hydraulic clamp body 131, a jaw 132 and a pin 133 mounted on the jaw. The pin is fixed at the outermost end of the jaw opening and is used to cooperate with the U-shaped rib. An anti-slip structure, such as an anti-slip groove, is provided on the pin 133 to prevent lateral slippage during the pulling process.
[0051] refer to Figures 4 to 9 Two suspended robotic arms 120 are installed on the crossbeam of the gantry 110. These two robotic arms are articulated, and can be custom-made or purchased from multiplied robotic arm modules. For example, the SDL-2000iC / 165F robotic arm can be purchased, which has six-axis motion and can be freely and flexibly adjusted in three-dimensional space. Through programming and configuration with intelligent functions such as autonomous learning, active grasping, picking, force sensors, and visual tracking, it can achieve intelligent identification, positioning, and welding of welding points, as well as intelligent identification, positioning, and stretching of pull-out points, making it a highly automated product.
[0052] Two robotic arms are positioned opposite each other and suspended from the gantry beam, forming an inverted structure with the upper end serving as the suspension point and the lower end as the mounting point. A hydraulic puller is installed at the lower end of one robotic arm, which applies force from one side to the pull point of the U-shaped ribs. This action is achieved using a vision tracking function. A welding torch is fixedly installed at the end of the other robotic arm, which performs welding operations on the lap section of the two U-shaped ribs from the other side, with visual recognition achieved through a vision tracking system. This realizes the mechanical action of simultaneous pull and welding. The above-mentioned pull and welding actions can be assisted by construction personnel or by configuring a corresponding vision recognition module.
[0053] When configuring a vision recognition module, this module should possess the functions of spatial position recognition of U-shaped ribs and determination of weld points. Specifically, the spatial recognition and weld point position determination process is as follows: Before construction begins, the vertical distance between the robotic arm and the overlapping area of the U-shaped ribs is measured using a plumb line, and the horizontal distance between the robotic arm and the overlapping area of the U-shaped ribs is measured using a distance measuring instrument. The downward and translational speeds of the robotic arm are fixed, so by performing vertical movement followed by horizontal movement, the robotic arm can accurately construct at the overlapping position of the U-shaped ribs. The two robotic arms operate on the same principle. Knowing the movement speed of the robotic arms, the horizontal and vertical distances that the robotic arms need to move are measured before construction begins. This data is input into the device, which can calculate the time required for each step from the start of construction to the completion of each set of U-shaped ribs.
[0054] This embodiment takes the wet joint of a standard section of box girder as an example, and the steps are as follows:
[0055] S1: Construction Preparation. First, according to construction requirements, formwork support is installed at the initial construction section. This formwork includes bottom and end formwork. First, clean the old concrete surface of the beam 00 near the joint, ensuring it is free of debris, dust, oil, etc. This can be done using tools such as brushes, high-pressure water guns, or air compressors. Then, determine and mark the location and width of the joint according to design requirements. Use a cutting machine or saw blade to cut, ensuring the joint is straight and vertical. Next, select appropriate support materials, such as formwork, tape, joint filler, or adhesive. Ensure the support materials meet specifications. Then, based on the width and depth of the joint, support the bottom and end faces of the wet joint with formwork 01 and end formwork 02, forming a concrete pouring cavity 03, and use tape to prevent leaks. Ensure there are no gaps or looseness. Check the installation quality of the support materials, ensuring their firmness and flatness. If necessary, make corrections and adjustments to ensure the quality of the support materials meets requirements. During the formwork support process, a certain length of hydraulic jack support space needs to be reserved at both ends of the wet joint. This space is used to support the hydraulic jack 04.
[0056] Finally, one or two pairs of U-shaped ribs near the end template 02 are welded. This welding initially fixes both ends of the box girder and maintains the stability of the space to be connected. This welding keeps the gap of the box girder fixed and cooperates with the hydraulic jack 04 in step S2 so that the hydraulic jack in the next process can have the opening action.
[0057] S2: Hydraulic jacks 04 are used to pry open the gaps on both sides of the first section, i.e., at least one hydraulic jack is installed at each end. A preferred configuration of the hydraulic jacks is as follows: Model: HJ2-2, Load capacity: 2 tons, Maximum lifting height: 200mm, Cylinder diameter: 50mm, Cylinder stroke: 100mm, Weight: 5kg. For ease of construction, the hydraulic jack 04 is modified as follows: It includes a crossbeam, which is a steel section. A pair of figure-eight connectors are used to connect the hydraulic jacks and the crossbeam, and the length of the crossbeam is much greater than the width of the wet joint. In use, the crossbeam is placed across the upper beam surface of the box girder on both sides of the wet joint, and the hydraulic jacks are welded to the underside of the steel section to achieve rapid positioning. The hydraulic jacks can be manually loaded, with the ends of the hydraulic jacks abutting against the sides of the wet joint of the box girder. For example, if the hydraulic gauge of a hydraulic jack indicates 0.5 tons, under the action of the aforementioned hydraulic jack, the U-shaped ribs at both ends are pulled out, that is, in a tensile state, and in this state, the U-shaped ribs have prestress.
[0058] S3: Place the special construction device 100 at the starting end of the wet joint construction. Specifically, it spans across the beams on both sides of the wet joint. This device has mobility and can move along the joint direction. Specifically, for each pair of U-shaped bars stretched and welded, it moves one standard distance unit. The standard distance unit refers to the spacing length between adjacent U-shaped bars. The jaw pin 133 of the special hydraulic puller in this device is inserted into the socket formed by the two U-shaped bars 05. Through the opening action of the special hydraulic puller, the U-shaped bars are stretched in opposite directions. During this process, the U-shaped bars are stretched to form tensile stress in the microscopic direction. A welding robot is used to assist in the welding operation. After welding is completed, the hydraulic puller is released and the pin 133 is pulled out from the socket. In this process, all U-shaped bars in the first section are stretched and welded one by one. During this process, the hydraulic lifting force of the hydraulic jack is gradually increased according to calculation. For example, for every five pairs of U-shaped bars stretched and welded, the hydraulic pressure of the hydraulic jack is increased by 0.05 tons.
[0059] S4: Pour concrete into the pouring space and compact it with a vibrator. After completion, observe the concrete strength during the solidification process. When the solidification strength reaches the design strength, remove the hydraulic jack 04 and continue curing until it is qualified. Then remove the formwork to complete the construction of the wet joint.
[0060] The above describes the construction process for one standard section. Then, the construction of the next standard section begins. This continues until all wet joints in the longitudinal direction are completed.
[0061] The calculations for the cold drawing and welding process of the above-mentioned device are as follows: During the construction preparation stage, the bridge data is calculated to obtain the required force F for cold drawing, the drawing length L1, the welding starting position and distance L2, the distance L5 between two adjacent pairs of U-shaped ribs, and the initial vertical distance L3 and horizontal distance L4 between the hydraulic puller and the U-shaped rib. These data are input into the central control module of this device. The central control module calculates the following based on the input data and the movement speed V1 of the robotic arm: the time taken for the hydraulic puller to start operating and enter the U-shaped rib is T1 = (L3 + L4) / V1; the cold drawing process of the hydraulic puller runs at a speed V2, taking T2 = L1 / V2; then, the welding robotic arm, after calculation, moves downward at a speed of V1 until it reaches a position parallel to the upper side of the U-shaped rib, and then moves to the welding point, with a total distance of L6 and a total time of T3 = L1 / L2. 6 / V1, then weld at a rate of V3, taking time T4=L2 / V3. After welding, the hydraulic puller is closed in time T5, and then all instruments return to the initial position. The time for processing a pair of U-shaped ribs in the wet joint is T=2T1+T2+2T3+T4+T5. After a pair of U-shaped ribs is processed, the moving speed of the movable gantry machine is V4. Therefore, the time to move to the next set after a pair of ribs is completed is T6=L5 / V4. Thus, the working cycle of a pair of ribs in this device is T+T6.
[0062] During construction, hydraulic jacks were used to pry open the gaps on both sides; that is, at least one hydraulic jack was installed at each end. The hydraulic jack's pressure parameters were: model: HJ2-2, load capacity: 2 tons, maximum lifting height: 200mm, cylinder diameter: 50mm, cylinder stroke: 100mm, weight: 5kg. For ease of construction, the hydraulic jack was modified as follows: it includes a crossbeam made of steel, and the hydraulic jack is welded to the bottom of the steel section. The hydraulic jack can be manually loaded.
[0063] Erect the movable gantry frame on both sides of the wet joint, positioning the hydraulic puller jaws in their initial positions. Operate the puller and welding robot arm. Under the control of the information processing device, the welding robot arm performs welding upon completion of the cold drawing process. After welding, the hydraulic puller is removed. The movable gantry frame then moves at the set speed. Because it is a precast box girder, the position and spacing of the U-shaped reinforcement at each wet joint are the same (therefore, the time required to complete the above steps is T+T6). Repeat the above steps.
[0064] When the first section of construction is nearing completion, install hydraulic jacks at the far end of the next standard section and remove the hydraulic jacks in the first section. Then, support the formwork at that standard section and move the aforementioned devices along the gap direction. During this process, pull out and weld all U-shaped ribs in that standard section one by one, observing the pressure of the hydraulic jacks throughout the process.
[0065] The puller and welding robot arm are equipped with force feedback devices. If the expander does not receive force feedback during the T2 time interval, the machine will stop operating. Similarly, if the welding robot arm does not receive welding force feedback during the T4 time interval, the machine will stop operating. The equipment will resume operation after manual intervention.
[0066] Figure 10 This illustrates a case of a U-shaped bar without overlapping segments, where short reinforcing bars are needed for auxiliary welding connections, and the jaws of the hydraulic puller move in the same direction as... Figure 7 The directions shown in the diagram are opposite. The hydraulic puller pulls the U-shaped ribs on both sides towards the middle, and short steel bars are used for auxiliary welding. After welding, they are integrated into one piece.
[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements to the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for constructing prestressed wet joints in beams, characterized in that, Follow these steps in sequence: S1: Construction preparation: Clean and roughen the sides of the beam at the wet joint to ensure there is no debris, dust, or / and oil. Determine and mark the location and width of the wet joint according to the design requirements. Cut the edge of the wet joint according to the markings to ensure the straightness and verticality of the wet joint. Based on the width and depth of the wet joint, support the bottom and end faces of the wet joint with formwork. There is a pouring cavity between the formwork and the beam. During the formwork support process, reserve space for hydraulic jack support at both ends of the wet joint. This hydraulic jack support space is located outside the pouring space. Finally, weld one or more pairs of U-shaped bars near the end formwork. This welding keeps the width of the wet joint between the beams fixed. S2: Use hydraulic jacks to open up the support space outside the pouring space. By applying hydraulic load to the hydraulic jacks, the welded U-shaped bars are pulled out. In this state, the welded U-shaped bars at both ends of the wet joint have a tensile stress value of N. S3: Place the specialized construction device at the starting end of the wet joint construction, spanning the beams on both sides of the wet joint. Insert the pin of the hydraulic puller in the specialized construction device into the socket formed by two U-shaped ribs. The hydraulic puller pulls the U-shaped ribs, causing them to be stretched and tensile stress in the microscopic direction. Maintain this tensile stress and use a welding machine for welding. After welding, release the hydraulic puller and remove the pin from the socket, completing the welding of one pair of U-shaped ribs. Then move the specialized construction device along the length of the beam, moving it one standard distance unit (the distance between adjacent U-shaped ribs) for the cold pulling and welding of the next pair of U-shaped ribs. Continue this process, completing the cold pulling and welding of the remaining U-shaped ribs. During this process, according to calculations, for every n pairs of U-shaped ribs welded, gradually increase the hydraulic loading force of the hydraulic jack. The tensile stress between each pair of U-shaped ribs is maintained at a value of N until all U-shaped ribs are stretched and welded. The special construction device includes a gantry frame, two robotic arms, and a hydraulic puller and welding gun mounted on the robotic arms. The gantry frame is formed by welding horizontal and vertical steel pipes and is arranged in a way that spans the wet joint. There are two walking mechanisms at the two lower ends of the gantry frame. A hydraulic station and an electrical control box are installed on the small platform of the walking mechanism. The two robotic arms are suspended and installed on the crossbeam of the gantry frame. A hydraulic puller is installed at the lower end of one robotic arm. The hydraulic puller acts on the pulling point of the U-shaped rib from one side. This action is based on the vision tracking function. A welding gun is installed at the lower end of the other robotic arm. The welding gun performs welding operation on the lap section of the two U-shaped ribs from the other side. The mechanical action of visual recognition and synchronous pulling and welding is realized through the vision tracking system. S4: Pour concrete into the pouring space and vibrate it. After completion, observe the concrete strength during the solidification process. When the solidification strength reaches the design strength, remove the hydraulic jacks and continue curing until it is qualified. Then remove the formwork to complete the construction of a standard section of beam wet joint.
2. The construction method for prestressed wet joints of beams according to claim 1, characterized in that, The calculations for the cold drawing and welding process are as follows: Based on the bridge data, the required force F for cold drawing, the drawing length L1, the starting position and distance L2 for welding, the distance L5 between two adjacent pairs of U-shaped ribs, and the initial vertical and horizontal distances L3 and L4 of the hydraulic puller from the U-shaped ribs are determined. These data are then input into the central control module. Based on the input data and the robotic arm's own moving speed V1, the central control module calculates the following: the time from the start of the hydraulic puller's operation to entering the U-shaped rib is T1 = (L3 + L4) / V1; the hydraulic puller's cold drawing process runs at a speed of V2, taking T2 = L1 / V2; then, the welding robotic arm, after calculation, moves downwards at a speed of V1 until it is parallel to the upper side of the U-shaped rib, and then moves to the welding point, a total distance of L6, taking a total time of T3 = L6 / V1; then, it welds at a speed of V3, taking T4 = L2 / V3; after welding, the hydraulic puller closes tightly, taking T5; then the instrument returns to its initial position; the time for processing a set of U-shaped ribs in the wet joint is T = 2T1 + T2 + 2T3 + T4 + T5; after a pair of U-shaped ribs is processed, the movable gantry machine tool moves at a speed of V4, so the time to move to the next pair of U-shaped ribs after one set of construction is T6 = L5 / V4.
3. The construction method for prestressed wet joints of beams according to claim 1, characterized in that, For every n pairs of U-shaped ribs cold-drawn and welded, the hydraulic jack increases the hydraulic loading force by 0.05 tons.
4. The construction method for prestressed wet joints of beams according to claim 1, characterized in that, The U-shaped ribs arranged in pairs are welded together using short ribs.
5. The construction method for prestressed wet joints of beams according to claim 1, characterized in that, Visual recognition and weld point location determination are as follows: Before construction begins, the vertical distance between the robotic arm and the overlapping area of the U-shaped ribs is measured using a plumb line, and the horizontal distance between the robotic arm and the overlapping area of the U-shaped ribs is measured using a distance measuring instrument. The downward and translational speeds of the robotic arm are fixed, so the robotic arm can accurately construct at the overlapping position of the U-shaped ribs by first moving vertically and then horizontally. The two robotic arms work on the same principle. Knowing the moving speed of the robotic arm, the horizontal and vertical distances that the robotic arm needs to move are measured before construction begins. The data is input into the device, which can calculate the time required for each step from the start of construction to the completion of a set of U-shaped ribs.
6. The construction method for prestressed wet joints of beams according to claim 5, characterized in that, The hydraulic puller consists of a hydraulic clamp body, clamp jaws, and a pin installed in the clamp jaws. The pin is fixed at the outermost end of the opening of the clamp jaws and engages with the U-shaped rib.
7. The construction method for prestressed wet joints of beams according to claim 6, characterized in that, The robotic arm is an articulated robotic arm with six-axis motion and is equipped with autonomous learning, active grasping and picking functions, force sensors, and visual tracking functions. It can intelligently identify, locate, and weld welding points, as well as intelligently identify, locate, and stretch pulling points.
8. The construction method for prestressed wet joints of beams according to claim 7, characterized in that, The cross-section of the pin is a horseshoe-shaped cross-section, a semi-circular cross-section, or a circular cross-section.
9. The construction method for prestressed wet joints of beams according to claim 1, characterized in that, The hydraulic jack is connected to the crossbeam via a connector, and the two ends of the crossbeam are supported on the beams on both sides.