Tensioning and anchoring system for large-diameter unbonded prestressed steel bars

Abstract

The utility model discloses a tensioning and anchoring system for a large-diameter unbonded prestressed steel bar, which comprises a prestressed steel bar, a spiral bar, an anchoring nut, an anchoring backing plate and a prestressed steel bar tensioning device, the prestressed steel bar tensioning device is arranged on the upper surface of the box girder and vertically tensions the prestressed steel bar, the anchor bearing plate and the prestressed steel bar are coaxially arranged, the anchoring nut is fastened to the lower end of the prestressed steel bar, the lower surface of the anchor bearing plate makes contact with the upper surface of the anchoring nut, and the two spiral bars and the prestressed steel bar are coaxial. The two spiral bars are arranged on the inner side of the prestressed steel bar tensioning device and the inner side of the anchor bearing plate respectively, and the prestressed steel bars are high-strength large-diameter unbonded heat treatment prestressed steel bars. The anchoring nut of the device adopts an unconventional spiral line structure, so that when the anchoring nut is tightly combined with concrete, the possibility of single-direction rotation and loosening caused by adopting a conventional thread structure is avoided.

Description

Technical Field

[0001] This utility model relates to the field of bridges, and in particular to a tensioning and anchoring system for large-diameter unbonded prestressed steel bars. Background Technology

[0002] Currently, bridges constitute a large proportion of newly constructed railways and highways, including numerous prestressed concrete continuous beams, continuous rigid frames, and continuous beam arches. To improve the shear resistance of large-span prestressed concrete structures, vertical prestressing is typically applied to the web and diaphragms of box girders during design. The vertical prestressing tendons for box girders are currently mainly composed of finely rolled threaded prestressed steel bars. However, due to the large and coarse thread spacing of these bars, the matching between the anchor nuts and the prestressing steel threads is poor, and they are incompatible with the tensioning equipment. This results in significant retraction of the anchor nuts after tensioning, making it difficult to accurately control the effective prestress. Furthermore, the pre-embedding of metal tubing during prestressing steel bar binding and the grouting of the ducts after tensioning also cause considerable inconvenience to on-site construction at the bridge site. Simultaneously, since the stress of finely rolled threaded prestressed steel bars is currently generally controlled at around 700 MPa, this also leads to material waste. Further structurally, because the embedded structures rely solely on spiral reinforcement in the tensioning direction, the vertical bonding between the embedded parts and the concrete in other tensioning directions is relatively low. This may lead to instability of the embedded parts, especially since the nut is the main load-bearing component.

[0003] A tensioning and anchoring system for large-diameter unbonded prestressed steel bars is needed to solve the above problems. Utility Model Content

[0004] This invention addresses the problems in existing technologies where the large and coarse thread spacing of finely rolled prestressed steel bars leads to poor matching between the anchor nuts and the prestressed steel bar threads, and incompatibility with tensioning equipment. This results in significant anchor nut retraction after tensioning, making accurate control of the effective prestress difficult. Furthermore, the pre-embedding of metal tubing during prestressing bar binding and the subsequent grouting of the tubing cause numerous inconveniences during bridge site construction. Additionally, the pre-embedded structure relies solely on helical reinforcement in the tensioning direction, resulting in low bonding between the vertical surfaces of other pre-embedded components and the concrete. This can lead to instability in the pre-embedded components, especially the nuts, which are the primary load-bearing components. This invention provides a tensioning and anchoring system for large-diameter unbonded prestressed steel bars, solving these problems.

[0005] This utility model provides a tensioning and anchoring system for large-diameter unbonded prestressed steel bars, including prestressed steel bars, a pair of spiral bars, anchor nuts, anchor plates, and a prestressing steel bar tensioning device. The prestressed steel bars are vertically arranged inside the web of a concrete box girder, with the lower end of the prestressed steel bars located inside the bottom surface of the box girder and the upper end of the prestressed steel bars extending beyond the upper surface of the box girder. The prestressing steel bar tensioning device is embedded in the upper surface of the box girder and vertically tensions the prestressed steel bars at a position on the upper surface of the box girder. The anchor plate is located inside the lower end of the prestressed steel bars in the web of the box girder and is coaxial with the prestressed steel bars. The lower end of the prestressed steel bars is threaded, and the anchor nuts are tightened to the lower end of the prestressed steel bars through internal threads. The lower surface of the anchor plate contacts the upper surface of the anchor nuts, and the outer diameter of the anchor plate is larger than the outer diameter of the anchor nuts. The two spiral bars are coaxial with the prestressed steel bars and are respectively located inside the prestressing steel bar tensioning device and inside the anchor plate. The prestressed steel bars are high-strength, large-diameter, unbonded, heat-treated prestressed steel bars.

[0006] The anchor nut has a symmetrical internal thread column structure with several adjacent angles equal through the axis. The outer side of the anchor nut is provided with a spiral texture, which is a broken line texture. The spiral textures on the sides of adjacent nuts are not at the same height and have opposite slopes. The spiral texture is an external thread or a groove structure.

[0007] The tensioning and anchoring system for large-diameter unbonded prestressed steel bars described in this utility model, as a preferred embodiment, has a prestressed steel bar diameter of less than or equal to 25 mm and a standard strength of 1420 MPa, 1570 MPa, 1770 MPa or 1860 MPa, and a service stress of 1100 MPa.

[0008] The tensioning and anchoring system for large-diameter unbonded prestressed steel bars described in this utility model, as a preferred embodiment, includes a prestressed steel bar tensioning device comprising a cylinder, a piston, a tensioning screw, a pressure nut, a support plate, a support sleeve, a rotating sleeve, a rotating inner ring, a rotating outer ring, a rotating handle, an outlet port, a return port, and a hydraulic mechanism. The cylinder has a columnar structure, with through holes on its top and bottom surfaces. The tensioning screw passes through the through holes on the top surface and is fastened to the top surface of the cylinder by the pressure nut. An oil cavity is provided between the through holes and the outer wall of the cylinder, with the bottom surface of the oil cavity penetrating the lower surface of the cavity. The working end of the piston is movably disposed within the oil cavity of the cylinder and radially closes the oil cavity. The connecting end of the piston extends downward along the working end of the piston, penetrating the lower part of the cavity of the cylinder. The through section is connected in sequence to the support sleeve and the support plate. Both the support sleeve and the support plate are annular structures and coaxial. The inner diameter of the support plate is smaller than the inner diameter of the support sleeve, and the outer diameter of the support plate is larger than the outer diameter of the support sleeve. The lower end of the tensioning screw is nested in the axial position of the support plate. A rotating sleeve that matches the inner cavity shape of the support sleeve and the outer diameter shape of the tensioning screw is provided between the support plate and the lower end of the tensioning screw. A rotating inner ring is provided between the upper side wall of the rotating sleeve and the support sleeve. A connection port for connecting prestressed steel bars is provided at the lower end of the rotating sleeve. A rotating outer sleeve is provided on the outer periphery of the support sleeve. A rotating handle is radially connected to the rotating outer sleeve. The cylinder outlet port and the cylinder return port are respectively connected to the upper end and the lower end of the cylinder cavity. The hydraulic mechanism is connected to the cylinder cavity through the cylinder outlet port and the cylinder return port.

[0009] In a preferred embodiment of the tensioning and anchoring system for large-diameter unbonded prestressed steel bars described in this utility model, the hydraulic mechanism includes a pair of pressure gauges, a pair of shut-off valves, a pair of check valves, a pair of throttle valves, a pair of overflow valves, a pair of oil pumps, an electric motor, an oil filter, a load oil tank, and a pair of unloading oil tanks. The load oil tank is connected in series with the oil filter, and the oil filter is connected in series with the two oil pumps. The output end of the electric motor is connected to the oil pumps. The two oil pumps are connected to the outlet oil port and the return oil port, respectively. Check valves are installed between the oil pumps and the outlet oil port, and between the oil pumps and the return oil port. Two pressure gauges are installed between the oil pumps and the outlet oil port, and between the oil pumps and the return oil port, respectively. An unloading oil tank is connected between the oil outlet of the check valve and the outlet oil port, and between the check valve and the return oil port, respectively. A shut-off valve is installed between the unloading oil tank and the oil outlet of the check valve. A throttle valve and an overflow valve are connected in parallel between the oil inlet of the check valve and the unloading oil tanks.

[0010] In the tensioning and anchoring system for large-diameter unbonded prestressed steel bars described in this utility model, as a preferred embodiment, the mating surfaces of the rotating sleeve and the rotating inner ring are mutually cooperating unidirectional ratchet structures.

[0011] In a preferred embodiment of the tensioning and anchoring system for large-diameter unbonded prestressed steel bars described in this utility model, a sealing structure is provided at the opening of the cylinder.

[0012] The beneficial effects of this utility model are as follows:

[0013] This tensioning and anchoring system saves on the amount of prestressed steel used in bridges; the tensioning and anchoring operations can be completed in one installation using the matching tensioning equipment, avoiding the problem of secondary tensioning of fine-rolled threaded prestressed steel bars; it eliminates the need for pre-embedding of metal sheet pipes and grouting of pipes, simplifying the construction steps and improving construction efficiency; the nuts in this tensioning and anchoring system adopt an unconventional spiral pattern structure, which, while ensuring a tight bond with the concrete, avoids the possibility of unidirectional rotational loosening caused by using conventional thread structures. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a tensioning and anchoring system for large-diameter unbonded prestressed steel bars.

[0015] Figure 2 This is a lateral schematic diagram of the anchor nut in a tensioning and anchoring system for large-diameter unbonded prestressed steel bars.

[0016] Figure 3 A schematic axial section of a prestressed steel bar tensioning device for a tensioning and anchoring system of large-diameter unbonded prestressed steel bars;

[0017] Figure 4 A schematic diagram of the hydraulic mechanism for a tensioning and anchoring system of large-diameter unbonded prestressed steel bars;

[0018] Figure 5 This is a sectional view of a prestressed steel bar tensioning device for a tensioning and anchoring system of large-diameter unbonded prestressed steel bars.

[0019] Figure label:

[0020] 1. Prestressed steel bars; 2. Spiral reinforcement; 3. Anchor nuts; 4. Anchor plates; 5. Prestressed steel bar tensioning equipment; 51. Cylinder body; 52. Piston; 53. Tensioning screw; 54. Bearing nut; 55. Support plate; 56. Support sleeve; 57. Rotating sleeve; 58. Rotating inner ring; 59. Rotating outer ring; 510. Rotating handle; 511. Cylinder outlet port; 512. Cylinder return port; 513. Hydraulic mechanism; 5131. Pressure gauge; 5132. Shut-off valve; 5133. Check valve; 5134. Throttle valve; 5135. Overflow valve; 5136. Oil pump; 5137. Electric motor; 5138. Oil filter; 5139. Load oil tank; 51310. Unloading oil tank. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0022] Example 1

[0023] like Figure 1 As shown, a tensioning and anchoring system for large-diameter unbonded prestressed steel bars includes prestressed steel bars 1, a pair of spiral bars 2, anchor nuts 3, anchor plates 4, and a prestressing steel bar tensioning device 5. The prestressed steel bars 1 are vertically installed inside the web of a concrete box girder, with their lower ends positioned inside the bottom surface of the box girder and their upper ends extending beyond the upper surface of the box girder. The prestressing steel bar tensioning device 5 is embedded within the upper surface of the box girder. The prestressing steel bar tensioning device 5 vertically tensions the prestressed steel bars 1 at a position on the upper surface of the box girder. The anchor plates 4 are positioned on... Inside the lower end of the prestressed steel bar 1 in the web of the box girder, the anchor plate 4 is coaxially arranged with the prestressed steel bar 1. The lower end of the prestressed steel bar 1 is threaded, and the anchor nut 3 is fastened to the lower end of the prestressed steel bar 1 through the internal thread. The lower surface of the anchor plate 4 contacts the upper surface of the anchor nut 3. The outer diameter of the anchor plate 4 is larger than the outer diameter of the anchor nut 3. The two spiral bars 2 are coaxial with the prestressed steel bar 1. The two spiral bars 2 are respectively arranged inside the prestressed steel bar tensioning device 5 and inside the anchor plate 4. The prestressed steel bar 1 is a high-strength, large-diameter, unbonded, heat-treated prestressed steel bar.

[0024] like Figure 2 As shown, the anchor nut 3 has a symmetrical internal thread column structure with several adjacent angles equal through the axis. The outer side of the anchor nut is provided with a spiral texture, which is a broken line texture. The spiral textures on the sides of adjacent nuts are not at the same height and have opposite slopes. The spiral textures are external threads or groove structures.

[0025] In this embodiment, the prestressed steel bar 1 has a diameter of less than or equal to 25 mm and a standard strength of 1420 MPa, 1570 MPa, 1770 MPa or 1860 MPa, and a service stress of 1100 MPa.

[0026] Specifically, in this embodiment, the high-strength, large-diameter, unbonded, heat-treated prestressed steel bar 1 has a maximum diameter of 25mm and can be further subdivided into specifications such as 16, 18, 20, 22, and 25mm. The standard strength is 1570MPa, and the service stress is approximately 1100MPa, which is about 57% higher than the 700MPa service stress of the precision-rolled threaded prestressed steel bar. The increase in service stress leads to a reduction in the cross-sectional area of ​​the vertical prestressed tendon. Among them, the φ20 and φ25mm prestressed steel bars can replace the currently used φ25 and φ32mm precision-rolled threaded prestressed steel bars, respectively, which can save more than 30% of the prestressed steel material usage.

[0027] The unbonded heat-treated prestressed steel bars and the matching anchor nuts are produced in the factory. The unbonded process uses a complete set of equipment to continuously extrude, plasticize, and coat with oil online. The prestressed steel bars can be cut to the required length according to the engineering requirements. Threads are formed at both ends by extruding with precision rolling wheels, and tensioning is carried out with the tensioning equipment matching the prestressed steel bars. The retraction amount of the anchor nut during prestress relaxation can be controlled within 1 mm, achieving the purpose of accurately controlling the prestress application.

[0028] The vertical prestress system of the box girder uses unbonded heat-treated prestressed steel bars instead of precision rolled threaded prestressed steel bars, which can eliminate the process of embedding metal iron pipes when tying the prestressed steel bar cage and the post-tensioning duct grouting, simplify the construction steps, shorten the construction period, and reduce the project cost.

[0029] The high-strength large-diameter unbonded heat-treated prestressed steel bars and the tensioning and anchoring system can be not only applied to newly built railway and highway bridges, but also widely used in the prestress projects such as the reinforcement of old bridges, the reinforcement of buildings, large-span factories, high-rise buildings, the anchoring support of mine shafts, and rock anchors.

[0030] Specifically, when this embodiment is used, it is installed according to the following method:

[0031] When tying the prestressed steel bar cage for the cast-in-place concrete continuous beam on-site, the unbonded prestressed steel bars are tied and positioned at the designed positions of the box girder webs or diaphragms, and the matching spiral stirrups, anchor plates, and anchor nuts at both ends are installed and fixed. Among them, the spiral stirrups under the anchor are made of Q235 prestressed steel bars with a diameter of φ10 mm, the anchor plates are made of Q235qD steel plates with a thickness of 20 - 25 mm, the unbonded prestressed steel bars and the matching anchor nuts are factory-made finished products, and the retraction amount of the prestressed steel bars in the anchoring system can be controlled within 1 mm.

[0032] When pouring the concrete of the beam body, a tensioning working anchor hole with a depth of 120 - 140 mm needs to be reserved at the预埋 position of the anchor plate on the top surface of the box girder, and the planar dimension is the same as that of the anchor plate.

[0033] After the concrete pouring of the beam body is completed and reaches the designed tensioning strength, prestress tensioning construction is carried out with the tensioning equipment matching the prestressed steel bars. When tensioning to the designed tensioning force, the anchor nut is tightened and then released by the nut locking device自带 at the front end of the tensioning equipment to achieve the anchoring effect. After the anchoring is completed, the tensioning equipment is removed, and the tensioning working anchor hole is sealed and leveled with prestressed steel bar meshes and concrete.

[0034] Such as Figure 3The prestressed steel bar tensioning device 5 includes a cylinder 51, a piston 52, a tensioning screw 53, a pressure nut 54, a support plate 55, a support sleeve 56, a rotating sleeve 57, a rotating inner ring 58, a rotating outer ring 59, a rotating handle 510, an outlet oil port 511, a return oil port 512, and a hydraulic mechanism 513. The cylinder 51 has a columnar structure, with through holes on its top and bottom surfaces. The tensioning screw 53 passes through the through holes on the top surface and is fastened to the top surface of the cylinder 51 by the pressure nut 54. An oil cavity is provided between the through holes of the cylinder 51 and the outer wall of the cylinder 51, with the bottom surface of the oil cavity penetrating the lower surface of the cavity. The working end of the piston 52 is movably disposed in the oil cavity of the cylinder 51 and radially closes the oil cavity. The connecting end of the piston 52 extends downward along the working end of the piston 52, passing through the lower part of the cavity of the cylinder 51, and is sequentially connected to the support sleeve 56 and the support plate 55. Both sleeve 56 and support plate 55 are annular structures and coaxial. The inner diameter of support plate 55 is smaller than the inner diameter of support sleeve 56, and the outer diameter of support plate 55 is larger than the outer diameter of support sleeve 56. The lower end of tensioning screw 53 is nested in the axial position of support plate 55. A rotating sleeve 57 is provided between support plate 55 and the lower end of tensioning screw 53, which matches the inner cavity shape of support sleeve 56 and the outer diameter shape of tensioning screw 53. A rotating inner ring 58 is provided between the upper side wall of rotating sleeve 57 and support sleeve 56. A connection port for connecting prestressed steel bar 1 is provided at the lower end of rotating sleeve 57. A rotating outer sleeve 59 is provided on the outer periphery of support sleeve. Rotating handle 510 is radially connected to rotating outer sleeve 59. Cylinder outlet oil port 511 and cylinder return oil port 512 are respectively connected to the upper end and lower end of the cavity of cylinder body 51. Hydraulic mechanism 513 is connected to the cavity of cylinder body 51 through cylinder outlet oil port 511 and cylinder return oil port 512.

[0035] like Figure 4 As shown, the hydraulic mechanism 513 includes a pair of pressure gauges 5131, a pair of shut-off valves 5132, a pair of check valves 5133, a pair of throttle valves 5134, a pair of relief valves 5135, a pair of oil pumps 5136, an electric motor 5137, an oil filter 5138, a load oil tank 5139, and a pair of unloading oil tanks 51310. The load oil tank 5139 is connected in series with the oil filter 5138, and the oil filter 5138 is connected in series with the two oil pumps 5136. The output end of the electric motor 5137 is connected to the oil pumps 5136. The two oil pumps 5136 are connected to the cylinder outlet port 511 and the cylinder return port 512, respectively. The oil pumps 5136 and the cylinder outlet port 51310 are connected to each other. 1. A one-way valve 5133 is installed between the oil pump 5136 and the return cylinder oil port 512. Two pressure gauges 5131 are respectively installed between the oil pump 5136 and the cylinder outlet oil port 511 and between the oil pump 5136 and the return cylinder oil port 512. An unloading oil tank 51310 is connected between the oil outlet end of the one-way valve 5133 and the cylinder outlet oil port 511, and between the one-way valve 5133 and the return cylinder oil port 512. A shut-off valve 5132 is installed between the unloading oil tank 51310 and the oil outlet end of the one-way valve 5133. A throttle valve 5134 and an overflow valve 5135 are connected in parallel between the oil inlet end of the one-way valve 5133 and the unloading oil tank 51310.

[0036] When the jack is used in conjunction with a high-pressure oil pump, the oil pump 5136 is driven by the motor 5137 to supply oil to the out-cylinder oil chamber of the jack through the right oil circuit. The cut-off (unloading) valves 5132 and throttle (speed-regulating) valves 5134 of the left and right oil circuits are all opened to achieve no-load starting of the oil pump. Slowly close the cut-off (unloading) valve 5132 of the left oil circuit and adjust the throttle (speed-regulating) valve 5134, and the pressurized oil enters the out-cylinder oil chamber. When the tensile force reaches 10% of the designed stress value, hold the load and measure and record. Then continue to supply oil to the left oil circuit (out-cylinder oil chamber), and at the same time rotate the rotating handle 510 to make the rotating ratchet mechanism drive the anchoring nut to move forward. When the tensile force reaches the designed stress, hold the load, rotate the handle 510 to make the anchoring nut abut against the bearing pad, and then return the oil to complete all the tensioning actions. After the prestressed steel bar is tensioned, it is locked by the anchoring nut, so that the retraction amount of the prestressed steel bar is reduced to within 1 mm.

[0037] When the concrete strength reaches the designed tensioning strength, install and fix the prestressed steel bar tensioning equipment on the hexagonal anchoring nut on the top plate of the box girder, and install the oil jack through-hole tensioning screw rod and the bearing nut at the tail of the oil jack. After all the installations are completed, start the oil pump supporting the tensioning equipment. When the oil pump pressure indication value reaches the designed tensile force, hold the load. At this time, rotate the rotating handle at the front end of the tensioning jack to drive the rotating sleeve to tighten the anchoring nut, and then slowly release the oil pump pressure. After the oil pressure returns to zero, return the oil to retract the oil cylinder of the jack, remove the bearing nut and the tensioning screw rod at the tail of the oil jack, and move away the tensioning equipment to prepare for the tensioning of the next prestressed steel bar.

[0038] As Figure 5 shown, the mating surface of the rotating sleeve 57 and the rotating inner ring 58 is a one-way ratchet structure that mates with each other.

[0039] A sealing structure is provided at the opening of the cylinder block 51.

[0040] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A tensioning anchoring system for large diameter un-bonded prestressed reinforcement, characterized in that: The prestressed steel bar (1) is vertically arranged in the concrete box girder web, the lower end of the prestressed steel bar (1) is arranged in the box girder lower bottom surface, the upper end of the prestressed steel bar (1) extends out of the box girder upper surface, the prestressed steel bar tensioning equipment (5) is in an embedded structure with the box girder upper surface, the prestressed steel bar tensioning equipment (5) vertically tension the prestressed steel bar (1) on the box girder upper surface, the anchor pad (4) is arranged on the inner side of the lower end of the prestressed steel bar (1) in the box girder web, the anchor pad (4) is coaxially arranged with the prestressed steel bar (1), the lower end of the prestressed steel bar (1) is provided with a thread, the anchor nut (3) is fastened with the lower end of the prestressed steel bar (1) through the internal thread, the lower surface of the anchor pad (4) contacts the upper surface of the anchor nut (3), the outer diameter of the anchor pad (4) is greater than the outer diameter of the anchor nut (3), the two spiral bars (2) are coaxial with the prestressed steel bar (1), the two spiral bars (2) are arranged on the inner side of the prestressed steel bar tensioning equipment (5) and the inner side of the anchor pad (4) respectively, and the prestressed steel bar (1) is a high-strength large-diameter unbonded heat-treated prestressed steel bar. The anchor nut (3) is a over-axis inner thread column structure with a plurality of adjacent equal vertical surfaces as symmetric surfaces, the outer side of the anchor nut is provided with a spiral texture, the spiral texture is a broken line type texture, the two ends of the spiral texture of the adjacent nut side surfaces are not equal in height and have opposite slopes, and the spiral texture is an external thread or a groove structure.

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