Large-span retard-bonded prestressed beam
By using slow-bonded prestressed beams in long-span beam structures, combined with locators and reinforcing bars, the problems of prestressed tendon positioning and curvature were solved, construction risks were reduced, and construction quality and joint strength were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 中交四航局第六工程有限公司
- Filing Date
- 2025-05-23
- Publication Date
- 2026-05-15
AI Technical Summary
In long-span beam structures, it is difficult to guarantee the accurate positioning and curvature of prestressed tendons, resulting in high risks during aerial construction and the tendency for cracks to form at beam end joints, which affects construction quality.
The prestressed beam structure with slow bonding is adopted. By setting locators on the steel reinforcement cage, including locating bars, locating sleeves and connectors, combined with reinforcing bars, the accurate positioning and curvature of the prestressing tendons are ensured. Reinforcing bars are also set at beam-to-beam or beam-to-column joints to prevent cracks from forming.
It improved the positioning accuracy and curvature of prestressed tendons, reduced the risks of aerial construction, enhanced the construction quality of long-span beams, prevented cracks at beam end joints, and improved the overall construction effect.
Smart Images
Figure CN224244445U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of building engineering technology, and in particular to a large-span, loosely bonded prestressed beam. Background Technology
[0002] In construction engineering, to improve the crack resistance and load-bearing capacity of concrete members, compressive stress is usually applied to the tension zone of the concrete member before it bears external loads, thereby improving the service performance of the concrete structure. Prestressed concrete structures can be divided into pre-tensioned and post-tensioned methods according to construction type. Post-tensioned prestressed concrete construction is widely used in practical engineering, but in specific applications, the following problems exist:
[0003] Prestressed concrete construction sometimes involves work in the air, requiring the installation and positioning of prestressing tendons. This aerial work carries significant risks. Improper operation during prestressing tendon tensioning can easily cause mechanical injuries. In some venues (such as stadiums), roof construction often involves large-span beam structures (span not less than 25m). Accurately positioning and ensuring the curvature of the prestressing tendons during aerial placement presents challenges, making it difficult to guarantee the subsequent construction quality of the large-span beam structure. Furthermore, during the tensioning process of large-span beams, cracks are prone to form at beam-column or beam-beam joints, affecting the overall construction quality of the large-span beams. Utility Model Content
[0004] One of the objectives of this utility model is, at least, to address the problems existing in the prior art by providing a large-span, loosely bonded prestressed beam that can improve the accuracy of the positioning of the loosely bonded prestressing tendons, ensure its curvature, reduce the risk of aerial construction of large-span, loosely bonded prestressed beams, and improve construction quality.
[0005] To achieve the above objectives, the technical solution adopted by this utility model includes the following aspects.
[0006] A large-span, loosely bonded prestressed beam includes: a crossbeam spanning column one, column two, and column three; loosely bonded prestressing tendons are provided inside the crossbeam along its length; the first end of the loosely bonded prestressing tendon is located inside the crossbeam or extends out of the crossbeam; and the second end of the loosely bonded prestressing tendon extends out of the crossbeam.
[0007] The loosely bonded prestressing tendons are arranged in a curved shape. The loosely bonded prestressing tendons are positioned within the steel reinforcement cage in the crossbeam by a locator. The locator includes a locating tendon, a locating sleeve, and a connector. The locating tendon is connected to the steel reinforcement cage. The locating sleeve passes through the locating tendon. The connector is movably connected to the locating sleeve. The connector is used to connect with the loosely bonded prestressing tendons to position the loosely bonded prestressing tendons so that the curvature of the loosely bonded prestressing tendons meets the requirements.
[0008] Preferably, the connector includes a vertical part and a bent part. The vertical part is connected to the positioning sleeve, the bent part is used to support the loosely bonded prestressing tendon, and the bent part is also connected to a limiting member. The limiting member is used to cooperate with the bent part to limit the loosely bonded prestressing tendon within the bent part.
[0009] Preferably, the positioning sleeve is provided with connecting parts on both sides, the vertical part includes vertical part one and vertical part two that are parallel to each other, the bending part includes bending part one and bending part two, bending part one is connected to vertical part one, bending part two is connected to vertical part two, and bending part one and bending part two are connected by bending part three.
[0010] Preferably, one end of the limiting member is bent into a connecting ring, and the connecting ring is connected to the bent portion.
[0011] Preferably, the positioning sleeve is also connected to the reinforcing bar, the reinforcing bar is perpendicular to the positioning bar, the reinforcing bar is threaded along its length, and the reinforcing bar is connected to the reinforcing bar skeleton.
[0012] Preferably, the positioning sleeve has a groove in the height direction, the groove is connected to the through hole of the positioning sleeve, and the positioning sleeve is connected to the reinforcing rib by a nut.
[0013] Preferably, the positioning rib has a scale along its length, the vertical part one and the vertical part two have threads along their length, and the vertical part one and the vertical part two also have a scale along their length.
[0014] Preferably, the slow-setting prestressing tendon includes a sheath, which is fitted onto the prestressing steel strand. The sheath is filled with a slow-setting adhesive. The sheath has main longitudinal ribs and secondary longitudinal ribs, which are arranged along the length of the sheath and along the circumference of the sheath. The main longitudinal ribs and secondary longitudinal ribs are staggered. The sheath also has multiple transverse ribs evenly distributed along its length. The transverse ribs protrude outward from the surface of the sheath, making the sheath have an uneven structure.
[0015] Preferably, the distance Ln1 between the first support column and the second support column is not less than 22m, and the distance Ln2 between the second support column and the third support column is not less than 3m.
[0016] Preferably, a reinforcing rib is provided at the connection node of the crossbeam near the end of the crossbeam. The reinforcing rib is inclined, with one end connected to the steel reinforcement skeleton of one crossbeam and the other end connected to the steel reinforcement skeleton of another crossbeam.
[0017] In summary, by adopting the above technical solution, this utility model has at least the following beneficial effects:
[0018] By setting a locator on the reinforcing steel cage, the locator includes a locating bar, a locating sleeve, and a connector. After the locating bar is connected to the reinforcing steel cage, the locating sleeve can move horizontally on the locating bar, and the connector can move vertically relative to the locating sleeve. When the positions of the locating bar, locating sleeve, and connector are determined according to the position of the curved positioning point of the loosely bonded prestressed tendon, the loosely bonded prestressed tendon is confined within the arc-shaped space of the connector after being connected by the connector. This ensures that the loosely bonded prestressed tendon is stable in the preset position. When pouring the beam concrete, the loosely bonded prestressed tendon will not move along the locating bar under the action of concrete or during vibration, thus improving the accuracy of the positioning of the loosely bonded prestressed tendon, ensuring the curvature of the loosely bonded prestressed tendon, and improving the construction quality of large-span loosely bonded prestressed beams.
[0019] By adding reinforcing bars at beam-beam joints or beam-column joints, cracks can be prevented at these joints during tensioning, further improving the construction quality of large-span, loosely bonded prestressed beams. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of a large-span, loosely bonded prestressed beam structure, which is an exemplary embodiment of this utility model.
[0021] Figure 2 This is a schematic diagram of the locator structure of an exemplary embodiment of the present invention.
[0022] Figure 3 This is a schematic diagram of the connection between the locator and the steel reinforcement cage in an exemplary embodiment of this utility model.
[0023] Figure 4 This is a schematic diagram of the fixed end structure of a slow-bonding prestressed tendon, an exemplary embodiment of this utility model.
[0024] Figure 5 This is a schematic diagram of the tensioning end structure of a slow-bonding prestressed tendon, an exemplary embodiment of this utility model.
[0025] Figure 6 This is a schematic diagram of the sheath structure of the slow-bonding prestressed tendon, an exemplary embodiment of this utility model.
[0026] Figure 7 This is a schematic cross-sectional view of a slow-bonding prestressed tendon, which is an exemplary embodiment of this utility model.
[0027] Figure 8 This is a schematic diagram of the reinforcing rib connection of an exemplary embodiment of the present invention.
[0028] Figure 9 This is a construction flowchart of a large-span, loosely bonded prestressed beam, which is an exemplary embodiment of this utility model.
[0029] In the diagram, the markings are: 1-beam, 2-column one, 3-column two, 4-column three, 5-slow-setting prestressing tendon, 51-shelter, 52-main longitudinal rib, 53-secondary longitudinal rib, 54-slow-setting adhesive, 55-prestressed steel strand, 56-transverse rib, 6-spiral hoop, 7-pressure bearing steel plate, 8-fixed anchor, 9-tensioning anchor, 10-polyethylene foam board, 11-reinforcing rib, 12-floor slab, 13-positioner, 131-positioning rib. 132-Positioning sleeve, 1320-Connecting part, 133-Connecting piece, 1330-Vertical part, 13301-Vertical part one, 13302-Vertical part two, 1331-Bending part, 13311-Bending part one, 13312-Bending part two, 13313-Bending part three, 134-Reinforcing bar, 135-Limiting piece, 1350-Connecting ring, A-Reverse bending point, 14-Reinforcing steel cage, 141-Longitudinal reinforcing bar. Detailed Implementation
[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, so that the purpose, technical solution and advantages of the present invention will be clearer. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0031] refer to Figures 1-3 The large-span, loosely bonded prestressed beam structure of the present invention includes a crossbeam 1, which spans support column 2, support column 3 and support column 4. Loosely bonded prestressed tendons 5 are provided inside the crossbeam 1 along the length of the crossbeam 1. The first end of the loosely bonded prestressed tendon 5 is located inside the crossbeam 1 or extends out of the crossbeam 1, and the second end of the loosely bonded prestressed tendon 5 extends out of the crossbeam 1 (the first end and the second end of the loosely bonded prestressed tendon are opposite each other). The steel reinforcement cage 14 of the crossbeam 1 is provided with a locator 13 for positioning the loosely bonded prestressed tendons 5 along its length. The locator 13 includes a locating rib 131, a locating sleeve 132, and a connector 133. The locating rib 131 is connected to the steel reinforcement cage 14. The locating sleeve 132 passes through the locating rib 131 and can move back and forth along the locating rib 131 to adjust its position on the locating rib 131. The connector 133 is movably connected to the locating sleeve 132 and is used to connect with the loosely bonded prestressed tendons 5 to position the loosely bonded prestressed tendons 5 so that the curvature of the loosely bonded prestressed tendons 5 meets the requirements. The connector 133 can move up and down along the locating rib 131 to adjust the height of the connector 133 so that the curvature of the loosely bonded prestressed tendons 5 meets the requirements.
[0032] The connector 133 includes a vertical portion 1330 and a bent portion 1331. The vertical portion 1330 is connected to the positioning sleeve 132. The bent portion 1331 supports the loosely bonded prestressing tendon 5. After the loosely bonded prestressing tendon 5 is placed inside the bent portion 1331, it can prevent the loosely bonded prestressing tendon 5 from shifting horizontally and ensure its curvature. The bent portion 1331 is also connected to the limiting member 135. After the loosely bonded prestressing tendon 5 is placed inside the bent portion 1331, the limiting member 135 cooperates with the bent portion 1331 to limit the loosely bonded prestressing tendon 5 inside the bent portion 1331, further ensuring the stability of the loosely bonded prestressing tendon 5. The positioning sleeve 132 is provided with a connecting portion 1320, which has a connecting hole. The vertical portion 1330 has an external thread in the height direction. The vertical portion 1330 passes through the connecting hole and is connected to the connecting portion 1320 by bolts.
[0033] Furthermore, the positioning sleeve 132 is provided with connecting parts 1320 on both sides. The two connecting parts 1320 are located on both sides of the positioning rib 131. The vertical part 1330 of the connector 133 includes a first vertical part 13301 and a second vertical part 13302 that are parallel to each other. The bending part 1331 includes a first bending part 13311 and a second bending part 13312. The first bending part 13311 is connected to the first vertical part 13301, and the second bending part 13312 is connected to the second vertical part 13302. The first bending part 13311 and the second bending part 13312 are connected by a third bending part 13313. The first bending part 13311 and the first vertical part 13301 can form an arc-shaped structure, the second bending part 13312 and the second vertical part 13302 can form an arc-shaped structure to limit and loosely bond the prestressed tendons 5, and the third bending part 13313 is an arc-shaped structure. The first vertical part 13301, the second vertical part 13302, the first bending part 13311, the second bending part 13312 and the third bending part 13313 can be integrally bent from steel bars to strengthen the structural strength of the connector 133; the first vertical part 13301 and the first bending part 13311, the second vertical part 13302 and the second bending part 13312 can also be welded.
[0034] In the aforementioned structure, the stability of the positioning sleeve 132 and the structural strength of the connector 133 can be improved by the parallel vertical parts 13301 and 13302, preventing the connector 133 from deforming. Furthermore, the limiting member 135 is made of steel bars, one end of the limiting member 135 is bent into a connecting ring 1350, and the other end is welded with a transverse rib perpendicular to it. The connecting ring 1350 is connected to the bending part 13313 so that the limiting member 135 can rotate relative to the connector 133. The limiting member 135 can be connected and fixed to the vertical part 1330. Furthermore, vertical parts 13301 and 13302 are threaded along their length. Each vertical part 13301 and 13302 is connected to its corresponding connecting part 1320 via a single nut or double nut. This not only allows for height adjustment of the vertical parts 1330 but also ensures the stability of the connection. The vertical parts 13301 and 13302 may also have graduations along their length to improve the accuracy of height adjustment for the connector 133. Similarly, the positioning rib 131 has graduations along its length (and may also have threads along its length) to improve the accuracy of position adjustment for the connector 133 relative to the positioning rib 131. The positioning sleeve 132 is also connected to the reinforcing rib 134. The reinforcing rib 134 is perpendicular to the positioning rib 131. The position of the reinforcing rib 134 is offset from the position of the connecting part 1320 in the horizontal direction. The reinforcing rib 134 is threaded in the length direction. The positioning sleeve 132 and the reinforcing rib 134 are fixed by a nut. The reinforcing rib can further improve the stability of the connection between the locator 13 and the steel skeleton 14, prevent the structure of the locator 13 from deforming, and also facilitate the movement of the positioning sleeve 132 along the positioning rib 131 to prevent the positioning sleeve 132 from being misaligned.
[0035] The positioning sleeve 132 and the positioning rib 131 can be fixed by nuts, that is, the nuts are respectively set at both ends of the positioning sleeve 132 in the length direction; the positioning sleeve 132 can also be fixed to the reinforcing rib 134 by nuts. When this connection method is adopted, the positioning sleeve 132 is provided with a groove in the height direction. The groove connects to the through hole of the positioning sleeve 132. After the nuts are set at both ends of the positioning sleeve 132 in the width direction, the groove width of the positioning sleeve 132 can be reduced by adjusting the nuts, thereby fixing the positioning sleeve 132 and the positioning rib 131.
[0036] refer to Figure 7 The slow-setting prestressing tendon 5 includes a sheath 51, which is fitted onto the prestressed steel strand 55. The sheath 51 is filled with a slow-setting adhesive 54. During the application of prestress to the beam 1, the slow-setting adhesive 54 is in a fluid state. After prestressing is applied to the beam 1, the slow-setting adhesive 54 solidifies and bonds tightly to the prestressed steel strand 55, which helps to improve the load-bearing capacity of the beam 1. (Reference) Figure 6 , Figure 7The sheath 51 is provided with main longitudinal ribs 52 and secondary longitudinal ribs 53. Both main longitudinal ribs 52 and secondary longitudinal ribs 53 are arranged along the length of the sheath 51 and along the circumference of the sheath 51. The main longitudinal ribs 52 and secondary longitudinal ribs 53 are arranged alternately. Multiple transverse ribs 56 are also evenly provided along the length of the sheath 51. The transverse ribs 56 protrude outward from the surface of the sheath 51, making the sheath 51 form an uneven structure. The main longitudinal ribs 52, secondary longitudinal ribs 53 and transverse ribs 56 can enhance the bonding force between the sheath 51 and the beam concrete, so that the slow-bonded prestressed tendons 5 and the beam concrete are stably bonded.
[0037] Along the length of the sheath 51, the main longitudinal ribs 52 are continuously provided, that is, the recessed parts between adjacent transverse ribs are provided with the main longitudinal ribs 52; the secondary longitudinal ribs 53 are intermittently provided, that is, the secondary longitudinal ribs 53 are only provided on the surface of the transverse ribs 56, and the recessed parts between adjacent transverse ribs 56 are not provided with the secondary longitudinal ribs 53.
[0038] refer to Figure 4 When the first end of the loosely bonded prestressing tendon 5 is located inside the crossbeam 1, the first end of the loosely bonded prestressing tendon 5 is a fixed end. The first end of the loosely bonded prestressing tendon 5 is connected to a bearing steel plate 7. The spiral hoop 6 passes through the loosely bonded prestressing tendon 5 and connects to the bearing steel plate 7. The bearing steel plate 7 is also connected to a fixed anchor 8. After the first end of the loosely bonded prestressing tendon 5 passes through the bearing steel plate 7, it is anchored inside the crossbeam 1 by the fixed anchor 8. (Reference) Figure 5 After the second end of the loosely bonded prestressing tendon 5 passes through the crossbeam 1, it is tensioned by the tensioning anchor 9 at the second end of the crossbeam 1. Similarly, another spiral hoop 6 passes through the second end of the loosely bonded prestressing tendon 5 and is connected to another bearing steel plate 7. The other bearing steel plate 7 is connected to the tensioning anchor 9, which is fixed to the second end of the crossbeam 1. A polyethylene foam board 10 is also provided around the tensioning anchor 9 (see reference). Figure 5 The polyethylene foam board 10 is fixed on the steel frame to form a working space for prestressing tensioning.
[0039] refer to Figure 8Near the end of beam 1, a reinforcing rib 11 is provided at the connection node between beams 1 and beam 1. The reinforcing rib 11 is inclined, with one end connected to the steel reinforcement cage of one beam 1 and the other end connected to the steel reinforcement cage of another beam 1. The reinforcing rib 11 and beam 1 are arranged in a triangle. The reinforcing rib 11 is used to improve the structural strength at the connection node of beam 1 and prevent cracks from occurring at the connection node of beam 1 during prestressing tensioning, which would affect the construction quality of beam 1. During construction, the reinforcing rib 11 can be set on one side of beam 1 or on both sides of beam 1 at the connection node. Multiple parallel reinforcing ribs 11 can be set to further improve the structural strength at the connection node of beam 1. The spacing between adjacent reinforcing ribs 11 is 100~150mm. Along the height direction of beam 1, the reinforcing ribs 11 are set near the top and bottom of beam 1 respectively. After the floor slab 12 is formed by pouring concrete, the reinforcing ribs 11 and floor slab 12 form an integral structure.
[0040] Continue to refer to Figure 1 The distance Ln1 between column 1 (2) and column 2 (3) is not less than 22m, and the distance Ln2 between column 2 (3) and column 3 (4) is not less than 3m. Within the crossbeam 1, the loosely bonded prestressing tendons 5 are arranged in a curved pattern. Along the length of the crossbeam 1, in the section crossing column 1 (2), the distance h1 between the loosely bonded prestressing tendons 5 and the top surface of the crossbeam 1 is 200~600mm. Between column 1 (2) and column 2 (3), the distance h2 between the apex of the loosely bonded prestressing tendon 5 and the bottom surface of the crossbeam 1 is 150mm. The distance Ln3 between the inflection point A near column 1 (2) and column 1 (2) is 0.15Ln1, and 970mm from the bottom surface of the crossbeam 1. The distance Ln3 between the inflection point A near column 2 (3) and column 2 (3) is... 0.15Ln1, 970mm from the bottom surface of beam 1; In the section spanning support 2 3, on the left side of the axis of support 2 3, the distance h3 between the loosely bonded prestressing tendon 5 and the top surface of beam 1 is 200~600mm, and on the right side of the axis of support 2 3, the distance between the loosely bonded prestressing tendon 5 and the top surface of beam 1 is h1; Between support 2 3 and support 3 4, the distance Ln4 from the control point to support 2 3 is 0.5Ln2, and the distance between the control point and the top surface of beam 1 is (h1+h2) / 2; At the second end of beam 1, the distance between the loosely bonded prestressing tendon 5 and the top surface of beam 1 is h2.
[0041] refer to Figure 9 The construction method of the large-span, loosely bonded prestressed beam of this utility model includes the following steps:
[0042] Step S1: Construction preparation.
[0043] Technical preparation: Conduct safety technical briefings, and determine the structural dimensions of the beams, the processing length of the loosely bonded prestressed tendons, construction methods and requirements, and the distribution of vertical transportation equipment such as tower cranes based on the beam structure construction drawings. The main technical parameters for the construction of large-span loosely bonded prestressed beams are shown in Table 1.
[0044] Table 1. Main Technical Parameters for Construction of Large-Span Slow-Bond Prestressed Beams
[0045]
[0046] On-site preparation: Inspect and accept the specifications, appearance, etc. of the delayed-bonding prestressing tendons. Determine the storage area for the delayed-bonding prestressing tendons, remove any standing water from the storage area, and set up a storage rack in the storage area. Use nylon slings to suspend the delayed-bonding prestressing tendons on the storage rack and cover them to prevent sun exposure and mechanical damage. After the delayed-bonding prestressing tendons arrive on site, check their diameter, sheath thickness, sheath cross rib dimensions, and whether the sheath has any air holes or damage. Observe the surface of the prestressed steel strands for rust, impurities, cracks, burrs, and other damage. If any of the above conditions are found, clean or replace the prestressed steel strands. The prestressed steel strands should be naturally straight after unwinding. The height of the cross ribs of the sheath should not be less than 1.8mm, and the rib groove depth should not be less than 1.6mm. Ensure that the retarding adhesive in the cross ribs is fully filled. If there is no retarding adhesive in the cross ribs or the retarding adhesive is not fully filled, it is prohibited to use them. After the delayed-bonding prestressing tendons arrive on site, the consistency reduction rate of the delayed-setting adhesive is tested. For each batch of delayed-bonding prestressing tendons, a sample of the delayed-setting adhesive should be taken of no less than 120g. During the test, the delayed-setting adhesive is placed in a sealed container and cured at 85℃ for 7 days. Its consistency reduction rate must be ≤40%. If it does not meet the aforementioned reduction rate, it is prohibited from use. Samples cured under the same conditions are taken, each sample should be no less than 100mm in length, and no less than 3 samples should be taken from each batch to check the curing condition of the delayed-setting adhesive.
[0047] Material and Equipment Preparation: In this utility model, C40 concrete is used for the beam concrete. The total chloride ion content in the beam concrete does not exceed 0.06% of the cement content to prevent corrosion of the reinforcing steel skeleton 14 and ensure the structural strength of the large-span, slowly bonded prestressed beam. Slow-bonded prestressed tendons are prepared according to the technical parameters shown in Table 1. Steel strands are cut in a flat and wide location. The length of each steel strand = straight length + curve increment + operating length. The straight length is the straight-line distance from the outer edge of the tensioning end on one side of the steel strand to the outer edge of the fixed end on the other side, as shown in the design drawing. The curve increment within the beam is calculated by doubling the beam height for each span (beam cross-section dimensions are 500mm × 1500mm). The operating length is: 1.2 meters for duct lengths within 20 meters, and 2.0 meters for duct lengths exceeding 20 meters. When the beam span is greater than 25m, tensioning is performed at both ends. For example, the calculation table for the length of the slowly bonded prestressed tendons is shown in Table 2.
[0048] Table 2 Calculation Table for the Length of Slow-bonding Prestressed Tendons
[0049]
[0050] Both fixed anchorage 8 and tensioning anchorage 9 are Class I anchorages. The static load anchorage performance of both fixed anchorage 8 and tensioning anchorage 9 meets the following requirements: the measured ultimate tensile strength of the assembly is not less than 95% of the measured ultimate tensile strength of the parent material, and the total elongation of the assembly is not less than 2%. After the anchorages arrive on site, their dimensions are checked to ensure they meet design requirements. The anchorage surfaces are free of cracks and deep scratches. After verifying the product quality certification documents, they are sent for retesting. The tensioning equipment is inspected in conjunction with the anchorages. The pressure gauge accuracy is not less than 1.5 grade, and the accuracy of the testing machine or force gauge used to calibrate the tensioning equipment is not less than ±2%. During calibration, the direction of the jack piston's movement is consistent with the actual tensioning working state.
[0051] Step S2: Erect the formwork, set up the bottom formwork for the crossbeam, and erect working platforms on both sides of the crossbeam; the working platforms are erected along the length of the crossbeam, and the formwork can provide support for the construction of the crossbeam, floor slab, working platform, etc.
[0052] Step S3: Tie the steel reinforcement cage 14 of the crossbeam and set the locator 13 on the steel reinforcement cage 14.
[0053] During the binding of the reinforcing steel cage 14, the bearing steel plates 7 of the fixed end and tensioning end of the loosely bonded prestressing tendon 5 are pre-embedded in the reinforcing steel cage 14 to ensure the correct installation and positioning between the loosely bonded prestressing tendon and the bearing steel plate, and to ensure the tensioning effect of the prestressing tendon and the stress performance of the structure. The construction of the locator 13 and the reinforcing steel cage 14 can be carried out simultaneously, or the locator 13 can be constructed after the construction of the reinforcing steel cage 14 of the crossbeam is completed.
[0054] After the steel reinforcement cage 14 of the crossbeam is constructed, the process of constructing the locator 13 includes:
[0055] The position of the locator 13 in the length direction of the steel cage 14 is determined and marked according to the positioning point of the curve of the slow-bonded prestressed tendon 5. The marking can be made on the longitudinal steel bar 141 at the top of the steel cage 14, or on the longitudinal steel bar or stirrup on the side of the steel cage 14.
[0056] After the positioning rib 131 passes through the positioning sleeve 132, the positioning rib 131 is fixed at the marked position on the top or side of the reinforcing steel cage 14. In this embodiment, it is preferable to fix the positioning rib 131 on the longitudinal reinforcing steel bar 141 at the top of the reinforcing steel cage 14, and the positioning rib 131 is welded to the longitudinal reinforcing steel bar 141. After the positioning rib 131 passes through the positioning sleeve 132, the reinforcing rib 134 can also pass through the positioning sleeve 132, and the reinforcing rib 134 is perpendicular to the positioning rib 131.
[0057] The positioning sleeve 132 on the positioning rib 131 is adjusted according to the distance relationship between the loosely bonded prestressed tendon and the side edge member of the crossbeam. After the positioning sleeve 132 is adjusted to the preset position, the positioning sleeve 132 and the positioning rib 131 are fixed to ensure the accuracy of the position of the loosely bonded prestressed tendon relative to the crossbeam. When fixing the positioning sleeve 132 and the positioning rib 131, the screw is passed through the positioning sleeve 132 and then connected to the nut. Since the top of the positioning sleeve 132 has a notch, the position of the nut on the screw can be adjusted to make the positioning sleeve 132 stably fixed on the positioning rib 131. The positioning sleeve 132 can also be fixed to the positioning rib 131 by nuts. When fixing, nuts are set on both sides of the positioning sleeve 132. The screw can be extended to obtain the reinforcing rib 134. After the position of the positioning sleeve 132 relative to the positioning rib 131 is determined, the reinforcing rib 134 can be welded to the stirrups on the steel reinforcement cage 14 to further improve the stability of the positioning sleeve 132.
[0058] Insert the limiting member 135 into the connector 133, and insert the nut into the vertical part 1330 (including vertical part one and vertical part two) of the connector 133. After the vertical part 1330 of the connector 133 passes through the connecting part 1320 on the positioning sleeve 132 from bottom to top, the connector 133 and the connecting part 1320 are connected by double nuts (nuts are set at the top and bottom of the connecting part 1320 respectively).
[0059] Adjust the vertical part 1330 of the connector 133 according to the distance relationship between the positioning point of the slow-bonded prestressed tendon 5 curve and the top of the steel cage 14. When the distance between the bent part 1331 of the connector 133 and the top of the steel cage 14 meets the preset requirements, fix the vertical part 1330 and the connecting part 1320.
[0060] In the aforementioned process, when two steel strands are to be threaded, two positioning sleeves 132 can be set on the positioning rib 131. Each positioning sleeve 132 is equipped with a connector 133. Adjusting the distance between the two positioning sleeves 132 can ensure that the distance between adjacent loosely bonded prestressed tendons meets the design requirements.
[0061] Step S4: Install the slow-bonding prestressing tendons 5 on the steel reinforcement cage 14, and connect the slow-bonding prestressing tendons 5 to the locator 13.
[0062] Before laying the loosely bonded prestressing tendon 5, the bearing steel plate and spiral hoop at the fixed end are inserted to prevent rework. The fixed anchor, bearing steel plate and spiral hoop are tightly fitted together. When connecting the loosely bonded prestressing tendon 5, the loosely bonded prestressing tendon 5 is passed through the connector 133 of each locator 13 from one end of the steel cage 14, so that the loosely bonded prestressing tendon 5 is located in the arc-shaped space formed by the vertical part 1330 and the bent part 1331 of the connector 133. After the loosely bonded prestressing tendon 5 passes through the steel cage 14, it is pulled back and forth to make it smooth and prevent the steel strand from getting tangled. Then, the limiting member 135 on the bent part 1331 of the connector 133 is rotated. After the limiting member 135 and the bent part 1331 or the vertical part 1330 are fixedly connected (welded, tied or connected by other means), the loosely bonded prestressing tendon 5 is limited in the connector 133. When multiple loosely bonded prestressing tendons 5 need to be installed in the beam, the loosely bonded prestressing tendons 5 are inserted into the reinforcing cage one by one. After the loosely bonded prestressing tendons 5 are inserted, the vertical part 1330 (and / or the bent part 1331) of the connector 133 can be connected to the stirrups of the reinforcing cage 14 by connecting steel bars (welding or binding), which further improves the deformation resistance of the connector 133 and the supporting effect on the loosely bonded prestressing tendons 5.
[0063] Step S5: Erect the side formwork of the crossbeam and pour the crossbeam concrete. Before erecting the formwork, fix the bearing steel plate 7 (cast iron trumpet tube) and spiral hoops at the tensioning end of the loosely bonded prestressing tendon 5, keeping the surface of the bearing steel plate 7 perpendicular to the tensioning line. Then, set polyethylene foam boards 10 around the bearing steel plate 7 to form a prestressing tensioning space. C40 concrete is used for the crossbeam. Before pouring, check the loosely bonded prestressing tendon bundles to ensure their curve shape is intact. If the curve shape deviates, adjust the curve of the loosely bonded prestressing tendon. During concrete pouring, avoid stepping on or colliding with the loosely bonded prestressing tendon 5, the locator 13, and the end embedded parts to ensure that the concrete at the fixed end and the tensioning end is poured densely.
[0064] Step S6: After the beam concrete reaches the tensile strength, tension the slow-bonding prestressing tendons 5.
[0065] Before tensioning, the jacks are calibrated with a calibration coefficient not exceeding 1.05. The hydraulic pressure gauge is calibrated using a shockproof type with an accuracy of not less than 0.4. The tensioning equipment (jacks and hydraulic pressure gauges used together) is then calibrated. The side formwork of the crossbeam is removed, but the supporting formwork at the bottom of the beam is retained to facilitate tensioning and ensure stable support for the crossbeam during the tensioning process. Before tensioning, the mortar on the bearing steel plate at the tensioning end is cleaned to ensure the tensioning anchor is tightly attached to the bearing steel plate. The tensioning service life of the loosely bonded prestressing tendons, the end embedded parts, and the concrete are checked and inspected to determine the actual strength of the part to be tensioned, the inspection results of the prestressed steel strands and anchors, the tensioning control stress, the theoretical elongation, the actual elongation, and the deviation rate.
[0066] Before tensioning, install the corresponding tensioning anchors and wedges according to the number of prestressed steel strands. The tensioning anchors should be centered and embedded in the stop of the anchor plate. The wedges should be tightened and exposed evenly to ensure that the tension line is perpendicular to the surface of the anchor plate. After the tensioning equipment is connected, start the oil pump and run the jack back and forth several times to remove the air remaining in the jack cylinder. During tensioning, the tension force line should coincide with the center line of the end of the loosely bonded prestressed tendon. During pre-tensioning, do not install the anchors and wedges first. Tension the prestressed tendon to about 30% of the control force and then release it. Then install the anchors and wedges and then perform formal tensioning.
[0067] When tensioning prestressed steel strands, attention should be paid to controlling stress, strain, and stress holding time, with stress control being the primary focus. Specifically, the tensioning control stress σ of the prestressed steel strands should be controlled. con The tensile strength should not exceed 0.75fptk (standard value of tensile strength for prestressed steel strands). Prestressed steel strands are tensioned using a sustained over-tensioning method, with the tensioning process starting from zero stress and increasing to 0.2σ. con Relax then re-tension to 0.2σ con → Tension to 0.4σ con →Tendredge to 1.05σ con Hold the load for a certain time → anchor, ensuring the oil gauge pressure and tensioning tonnage are maintained during anchoring → remove the jacks and compile the tensioning records; if the actual elongation of the prestressed steel strand exceeds the theoretical elongation by -6% to +6%, stop tensioning and continue tensioning after identifying the cause. The holding time is related to the ambient temperature and is calculated using interpolation. For example, stop tensioning when the ambient temperature is below 5℃; hold the load for 4 minutes when the ambient temperature is 5℃; hold the load for 2 minutes when the ambient temperature is 10℃; hold the load for 1 minute when the ambient temperature is 15℃; and hold the load for 0.5 minutes when the ambient temperature is 20℃.
[0068] During tensioning, prevent the prestressed steel strands from breaking or slipping. If breakage or slippage occurs, immediately stop tensioning, remove the jacks and limit plates, install an anchor release processor between the jacks and the anchor plate, and slowly re-tension. The anchor release tensioning stress should be greater than the original tensioning tonnage, but not greater than 0.8fptk. Use the tensioned steel strand bundle to pull out the wedges, then use a small steel needle to remove the wedges from the opening of the anchor release processor. Remove the anchor release processor, inspect the anchor plate, reinstall new wedges, and re-tension. If the steel strands and anchors have obvious scratches due to slippage, replace the wedges and steel strands.
[0069] Step S7: Cut off the loosely bonded prestressing tendon 5. After cutting, the length of the loosely bonded prestressing tendon 5 exposed above the anchor wedge should not be less than 30mm. After applying anti-corrosion grease to the cap, use micro-expansion fine stone concrete or sealing mortar with a grade one higher than that of the beam concrete to seal the anchorage and protect the anchorage area.
[0070] The above description is merely a detailed illustration of specific embodiments of this utility model, and not a limitation thereof. Various substitutions, modifications, and improvements made by those skilled in the art without departing from the principles and scope of this utility model should be included within the protection scope of this utility model.
Claims
1. A large-span, loosely bonded prestressed beam, characterized in that, include: A crossbeam (1) spans a support column (2), a support column (3) and a support column (4). A slow-bonding prestressing tendon (5) is provided inside the crossbeam (1) along the length of the crossbeam (1). The first end of the slow-bonding prestressing tendon (5) is located inside the crossbeam (1) or extends out of the crossbeam (1). The second end of the slow-bonding prestressing tendon (5) extends out of the crossbeam (1). The slow-bonded prestressing tendon (5) is arranged in a curved shape. The slow-bonded prestressing tendon (5) is positioned in the steel reinforcement skeleton (14) in the crossbeam (1) by a locator (13). The locator (13) includes a locating tendon (131), a locating sleeve (132) and a connector (133). The locating tendon (131) is connected to the steel reinforcement skeleton (14). The locating sleeve (132) is inserted on the locating tendon (131). The connector (133) is movably connected to the locating sleeve (132). The connector (133) is used to connect with the slow-bonded prestressing tendon (5) to position the slow-bonded prestressing tendon (5) so that the curvature of the slow-bonded prestressing tendon (5) meets the requirements.
2. The large-span, loosely bonded prestressed beam according to claim 1, characterized in that, The connector (133) includes a vertical part (1330) and a bent part (1331). The vertical part (1330) is connected to the positioning sleeve (132). The bent part (1331) is used to support the loosely bonded prestressed tendon (5). The bent part (1331) is also connected to a limiting member (135). The limiting member (135) is used to cooperate with the bent part (1331) to limit the loosely bonded prestressed tendon (5) within the bent part (1331).
3. The large-span, loosely bonded prestressed beam according to claim 2, characterized in that, The positioning sleeve (132) has connecting parts (1320) on both sides. The vertical part (1330) includes a vertical part one (13301) and a vertical part two (13302) that are parallel to each other. The bending part (1331) includes a bending part one (13311) and a bending part two (13312). The bending part one (13311) is connected to the vertical part one (13301), and the bending part two (13312) is connected to the vertical part two (13302). The bending part one (13311) and the bending part two (13312) are connected by a bending part three (13313).
4. The large-span, loosely bonded prestressed beam according to claim 3, characterized in that, One end of the limiting member (135) is bent into a connecting ring (1350), and the connecting ring (1350) is connected to the bending part three (13313).
5. The large-span, loosely bonded prestressed beam according to claim 1, characterized in that, The positioning sleeve (132) is also connected to the reinforcing bar (134), which is perpendicular to the positioning bar (131). The reinforcing bar (134) has threads along its length and is connected to the steel reinforcement cage (14).
6. The large-span, loosely bonded prestressed beam according to claim 5, characterized in that, The positioning sleeve (132) has a groove in the height direction, the groove is connected to the through hole of the positioning sleeve (132), and the positioning sleeve (132) is connected to the reinforcing rib (134) by a nut.
7. The large-span, loosely bonded prestressed beam according to claim 3, characterized in that, The positioning rib (131) has a scale in the length direction, the vertical part one (13301) and the vertical part two (13302) have threads in the length direction, and the vertical part one (13301) and the vertical part two (13302) also have a scale in the length direction.
8. The large-span, loosely bonded prestressed beam according to claim 1, characterized in that, The slow-setting prestressed tendon (5) includes a sheath (51), which is fitted onto the prestressed steel strand (55). The sheath (51) is filled with a slow-setting adhesive (54). The sheath (51) is provided with a main longitudinal rib (52) and a secondary longitudinal rib (53). The main longitudinal rib (52) and the secondary longitudinal rib (53) are both arranged along the length of the sheath (51). The main longitudinal rib (52) and the secondary longitudinal rib (53) are both arranged along the circumference of the sheath (51). The main longitudinal rib (52) and the secondary longitudinal rib (53) are arranged alternately. The sheath (51) is also uniformly provided with multiple transverse ribs (56) along its length. The transverse ribs (56) protrude outward from the surface of the sheath (51), making the sheath (51) form an uneven structure.
9. The large-span, loosely bonded prestressed beam according to claim 1, characterized in that, The distance Ln1 between the first (2) and the second (3) is not less than 22m, and the distance Ln2 between the second (3) and the third (4) is not less than 3m.
10. The large-span, loosely bonded prestressed beam according to any one of claims 1 to 9, characterized in that, Near the end of the crossbeam (1), a reinforcing rib (11) is provided at the connection node of the crossbeam (1). The reinforcing rib (11) is inclined and one end of the reinforcing rib (11) is connected to the steel reinforcement skeleton of one crossbeam (1), and the other end is connected to the steel reinforcement skeleton of another crossbeam (1).