Variable cross-section stack box rigid frame aqueduct, cantilever hanging basket and prestress tensioning method

Abstract

The invention discloses a variable-cross-section stacked box rigid frame aqueduct, a cantilever hanging basket and a prestress tensioning method in the field of prestressed concrete aqueducts, the transverse section of a water passing groove is a U-shaped section, and the U-shaped section of the water passing groove is far superior to a rectangular section in the aspects of water delivery flow conditions and flow passing capacity; a prestress continuous rigid frame structure form of a U-shaped water passing upper tank with a variable cross-section rectangular lower tank stacked upwards and a guide groove unified cross section and a two-system four-way prestress system are arranged, the concrete stress of the upstream face of the U-shaped water passing groove can be accurately and effectively controlled to be kept in a uniform compression state with a certain numerical value, and the anti-seepage and durability functions of the aqueduct are ensured. According to the tensioning method, the vertical steel beams and the U-shaped steel beams are partially tensioned firstly, so that the aqueduct web has certain vertical pressure stress, then longitudinal prestress is tensioned, the effect of the vertical steel beams and the U-shaped steel beams is prevented from being weakened by the longitudinal prestress, and pressure stress reserve of the upstream face of the U-shaped groove is guaranteed; the pouring hanging basket prevents the formwork from floating or shifting in the pouring process of the variable-thickness middle partition plate.

Description

Technical Field

[0001] The invention relates to the technical field of prestressed concrete continuous rigid frame aqueduct, in particular to a cross-section stacked box rigid frame aqueduct, a cantilever hanging basket and a prestressed tensioning method. Background Art

[0002] With the rapid development of China's water conservancy projects, demand for ultra-large-span water transfer aqueducts continues to increase. This is particularly true in long-distance overground water transfer aqueduct projects, where large-span aqueducts are preferred for crossing deep trenches, wide rivers, and critical transportation facilities. Prestressed concrete continuous rigid frame aqueducts are increasingly popular in water transfer projects due to their structural advantages, high water transfer strength, high spanning capacity, and safe and efficient construction.

[0003] The existing water channel cross-section can generally only be selected as a rectangular section, and cannot be directly connected with a U-shaped or circular water-passing section aqueduct with better water-passing stress performance. The existing continuous rigid frame aqueduct technology cannot be directly used in continuous aqueducts with large flow and large span, and a section transition section must be set for connection, which increases the construction difficulty and project investment.

[0004] Rectangular cross-sections, due to factors such as boundary effects, uneven streamlines, flow friction, and uneven pressure distribution, suffer from uneven flow distribution, reduced flow velocity, and relatively poor water-carrying capacity. Circular cross-sections, on the other hand, are better able to guide water flow, maintaining uniformity and efficiency. Therefore, rectangular cross-sections have lower water-carrying capacity than circular cross-sections. Furthermore, during earthquakes, the water in the aqueduct oscillates periodically with surface vibrations. The fluid-structure coupling effect between the water and the structure alters the aqueduct's dynamic characteristics, especially for long-span structures, where water inertia has a greater impact on the structure, posing a risk of structural damage. Furthermore, to overcome water inertia, rectangular cross-sections often require thicker box webs and greater structural rigidity, increasing construction costs and difficulty.

[0005] In actual engineering activities, in order to improve the water-passing capacity and seismic resistance of rectangular cross-sections, a circular chamfer is generally set between the middle diaphragm and the web. Since the existing technology uses vertical steel bundles in the web and transverse steel bundles in the middle diaphragm to achieve stress tensioning on the water channel, when the chamfer radius increases, the prestressed blind area at the chamfer becomes larger. When the water load and temperature are coupled, the tensile stress will increase sharply, which will cause concrete cracking, leakage, and corrosion of structural steel bars, threatening the durability and safety of the structure. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the technical problem to be solved by the present invention is: how to ensure the water-passing capacity and seismic resistance of the prestressed concrete continuous rigid frame aqueduct water-passing section while effectively controlling the stress of the water-passing trough concrete to always be in a compressive state without the risk of cracks in the concrete on the water-facing surface.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] The variable-section stacked box rigid frame aqueduct comprises a continuous rigid frame box girder, wherein the continuous rigid frame box girder comprises at least one aqueduct unit, wherein a water trough and a structural trough are provided in the aqueduct unit, wherein the water trough is located above the structural trough, and the transverse cross-sectional dimension of the structural trough gradually decreases from the middle to both sides; the aqueduct unit is further provided with a two-system four-way prestressed system, comprising a longitudinal section system and a transverse section system, wherein the longitudinal section system comprises a top plate longitudinal steel bundle, a web longitudinal steel bundle and a bottom plate longitudinal steel bundle; the transverse section system The system includes vertical steel bundles of the web, transverse steel bundles of the top plate, transverse steel bundles of the middle partition and transverse steel bundles of the bottom plate; the transverse section of the above-mentioned water trough is a U-shaped section, and the above-mentioned transverse section system also includes a U-shaped steel bundle arranged around the outside of the trough surface of the above-mentioned water trough, and the above-mentioned U-shaped steel bundle includes vertical sections on both sides and a semicircular arc section in the middle, and the above-mentioned vertical sections and the upper part of the above-mentioned vertical steel bundles of the web on the corresponding side are arranged in parallel, and the above-mentioned semicircular arc section is located above the corresponding transverse steel bundle of the above-mentioned middle partition; the above-mentioned anti-collapse component includes a plurality of anti-collapse ribs arranged at intervals on the outside of the above-mentioned semicircular arc section.

[0009] Furthermore, the vertical surface where the U-shaped steel bundle is located is perpendicular to the inner wall of the water trough.

[0010] Furthermore, the radius of the arc-shaped portion of the water trough is not less than 3m.

[0011] Furthermore, the top plate longitudinal steel bundle includes a plurality of first steel bundle units arranged in horizontal rows; the web plate longitudinal steel bundle includes a plurality of second steel bundle units arranged in vertical rows, the plurality of second steel bundle units gradually increase in length from bottom to top, and the two ends of the second steel bundle units are symmetrically bent downward and extended; the bottom plate longitudinal steel bundle includes a plurality of third steel bundle units arranged in horizontal rows, the third steel bundle units on both sides of the aqueduct unit are not connected, and one end of the third steel bundle unit close to the middle of the aqueduct unit is bent upward; the web plate vertical steel bundle includes a plurality of fourth steel bundle units arranged in vertical rows; the top plate transverse steel bundle includes a plurality of fifth steel bundle units arranged in horizontal rows, the middle partition transverse steel bundle includes a plurality of sixth steel bundle units arranged in horizontal rows, the bottom plate transverse steel bundle includes a plurality of seventh steel bundle units arranged in horizontal rows, and the seventh steel bundle unit terminates at the overlapping position of the middle partition and the bottom plate of the aqueduct unit; the vertical section is arranged in a row with the fourth steel bundle units at the corresponding position, and the semicircular arc section is located above the corresponding sixth steel bundle unit.

[0012] Furthermore, the upper bent end of the above-mentioned third steel bundle unit passes through the above-mentioned structural groove and is anchored. The lengths of the multiple above-mentioned third steel bundle units are different, and one end of the multiple above-mentioned third steel bundle units close to the middle of the above-mentioned aqueduct unit passes through the lower wall of the above-mentioned structural groove at intervals in the length direction of the above-mentioned aqueduct unit and is fixed by an anchor block.

[0013] The present invention also proposes a prestressing method, comprising:

[0014] In the a beam section, the vertical web steel bundles and U-shaped steel bundles are first tensioned synchronously, and the tensioning force does not reach 100% of the preset tensioning force. Then, the top plate longitudinal steel bundles, the web longitudinal steel bundles and the bottom plate longitudinal steel bundles are tensioned at the same time, and the tensioning force reaches the preset tensioning force. After the hanging basket is moved into the b beam section, the corresponding top plate transverse steel bundles, the middle partition transverse steel bundles and the bottom plate transverse steel bundles in the a beam section are tensioned, and the tensioning force reaches the preset tensioning force. Finally, the vertical web steel bundles and U-shaped steel bundles in the a casting stage are tensioned again at the same time to make the tensioning force reach the preset tensioning force. The above steps are a steel bundle tensioning cycle, and the prestressing is completed by repeating multiple cycles in sequence. The above-mentioned a beam section and the above-mentioned b beam section are two adjacent casting beam sections in the standard cantilever stacking casting process.

[0015] Furthermore, the tensioning force of the initial tensioning of the web vertical steel tendons and U-shaped steel tendons is 50% of the preset tensioning force.

[0016] Furthermore, the tensioning method of the web vertical steel bundle, U-shaped steel bundle, top plate longitudinal steel bundle, web longitudinal steel bundle and bottom plate longitudinal steel bundle is symmetrical tensioning at both ends, and the tensioning method of the top plate transverse steel bundle, middle partition transverse steel bundle and bottom plate transverse steel bundle is single-end tensioning.

[0017] The present invention also proposes a casting hanging basket for a variable-section stacked box rigid frame aqueduct, comprising an upper truss arranged at the upper end of the above-mentioned aqueduct unit, the upper truss being provided with a first boom extending downward, a support frame with adjustable height being provided in the above-mentioned structural groove, a support suspension being provided on the side of the support frame facing the casting direction of the above-mentioned stacked box beam body, the upper end of the above-mentioned support suspension being provided with a bracket flush with the top wall of the above-mentioned lower box, the end of the above-mentioned support suspension away from the above-mentioned stacked box beam body being detachably connected to the above-mentioned first boom, the above-mentioned support suspension being further detachably provided with a second boom extending downward, the lower end of the above-mentioned second boom being connected to a bottom formwork; and also comprising a water channel casting support structure, the above-mentioned water channel casting support structure comprising a U-shaped inner mold for casting the above-mentioned water channel, the lower end of the above-mentioned upper truss being provided with an abutment frame, and a plurality of abutment joints at the lower end of the above-mentioned abutment frame abutting against the inner wall of the above-mentioned U-shaped inner mold.

[0018] The beneficial effects of the present invention are:

[0019] (1) The U-shaped water-passing section and the continuous rigid frame structure form are combined to form a U-shaped water-passing upper box rigid frame aqueduct with a variable cross-section rectangular lower box and a uniform cross-section of the guide channel. The U-shaped water-passing upper box rigid frame aqueduct is superior to the rectangular water-passing section rigid frame aqueduct in terms of water conservancy conditions and flow capacity. It eliminates the many inconveniences caused by the transition section of the water-passing section. Moreover, under the same flow rate and the same gradient, the water weight load borne by the structure is smaller than that of the former, which reduces the impact of the water body swaying inertia force on the structure caused by earthquakes, can meet the requirements of lightweight design and reduce construction costs and difficulties. By setting up a two-system four-way prestressing system, the overall stress reserve and strength of the longitudinal system are guaranteed, and the local compressive stress reserve of the transverse system is guaranteed, effectively preventing concrete cracking. In particular, the U-shaped steel bundles that match the U-shaped water-passing section, in conjunction with other second-system steel bundles, can accurately and effectively control the concrete stress of the U-shaped water-passing channel water-facing surface to maintain a uniform pressure state at a certain value, ensuring the anti-seepage and durability functions of the aqueduct. By setting up anti-collapse reinforcement, the U-shaped water trough surface can be effectively prevented from cracking under the tensioning action of the U-shaped steel bundle, which is beneficial to improving the stability of the stress state of the concrete on the water-facing surface of the U-shaped water trough.

[0020] (2) The prestressing system tensioning method proposed in this application proposes to pre-tension the vertical and U-shaped steel strands, which can provide a certain compressive stress reserve in the aqueduct web, thereby avoiding the problem of stress concentration and local cracking caused by the tensioning of the longitudinal steel strands. After tensioning the longitudinal steel strands of the first system, the vertical and U-shaped steel strands of the web are tensioned again to eliminate the loss of transverse prestress in the second system caused by the tensioning of the first system steel strands.

[0021] (3) The casting hanging basket proposed in this application adopts a support frame supported in the cast structure groove to extend the support suspension to cooperate with the first boom to achieve a more stable support effect. In addition, by setting a U-shaped inner mold and setting an abutment frame against the inner wall of the inner mold, it can avoid the template of the variable thickness middle partition from floating or shifting during the casting process, thereby ensuring the casting quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the transverse cross-sectional structure of the aqueduct of the present invention;

[0023] Figure 2 This is a schematic diagram of the anti-collapse reinforcement installation structure of the present invention;

[0024] Figure 3 Schematic diagram of the positional relationship among the longitudinal steel bundles of the top plate, the longitudinal steel bundles of the web plate, and the longitudinal steel bundles of the bottom plate of the present invention;

[0025] Figure 4 It is a longitudinal cross-sectional schematic diagram of the present invention;

[0026] Figure 5 Schematic diagram of the web vertical steel bundle, top plate transverse steel bundle, diaphragm transverse steel bundle and bottom plate transverse steel bundle of the present invention;

[0027] Figure 6 Schematic diagram of the longitudinal steel bundle distribution of the web of the present invention;

[0028] Figure 7 Schematic diagram of the distribution relationship of the longitudinal steel bundles of the top plate, the longitudinal steel bundles of the web plate, and the longitudinal steel bundles of the bottom plate of the present invention;

[0029] Figure 8 It is a longitudinal cross-sectional schematic diagram of the pouring hanging basket of the present invention;

[0030] Figure 9 It is a schematic cross-sectional view of the pouring hanging basket of the present invention;

[0031] Marked in the figure are, 1-top plate, 2-web plate, 3-middle partition plate, 4-bottom plate, 5-water trough, 6-structural trough, 7-U-shaped steel bundle, 8-bottom plate longitudinal steel bundle, 9-top plate longitudinal steel bundle, 10-web plate longitudinal steel bundle, 11-web plate vertical steel bundle, 12-top plate transverse steel bundle, 13-middle partition plate transverse steel bundle, 14-bottom plate transverse steel bundle, 15-anti-collapse reinforcement, 16-structural reinforcement, 17-upper truss, 18-first boom, 19-second boom, 20-bottom formwork, 21-support frame, 22-support suspension, 23-bracket, 24-U-shaped inner formwork, 25-abutment frame, 26-abutment joint. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] according to Figure 1-Figure 7 As shown, the embodiment of the present application proposes a variable-section stacked box rigid frame aqueduct, including a continuous rigid frame box beam, the continuous rigid frame box beam including at least one aqueduct unit, a water trough 5 and a structural trough 6 are provided in the aqueduct unit, the water trough 5 is located above the structural trough 6, and the transverse cross-sectional size of the structural trough 6 gradually decreases from the middle to both sides; the aqueduct unit is also provided with a two-system four-way prestressed system, including a longitudinal section system and a transverse section system, the longitudinal section system including a top plate longitudinal steel bundle 9, a web longitudinal steel bundle 10 and a bottom plate longitudinal steel bundle 8; the transverse section The system includes vertical steel bundles 11 for the web, transverse steel bundles 12 for the top plate, transverse steel bundles 13 for the middle diaphragm, and transverse steel bundles 14 for the bottom plate. The transverse cross-section of the water trough 5 is a U-shaped cross-section. The transverse cross-section system also includes a U-shaped steel bundle 7 arranged around the outside of the trough surface of the water trough 5. The U-shaped steel bundle 7 includes vertical sections on both sides and a semicircular arc section in the middle. The vertical sections and the upper part of the vertical steel bundles 11 for the web on the corresponding side are arranged in parallel. The semicircular arc section is located above the corresponding transverse steel bundles 13 for the middle diaphragm. The anti-collapse assembly includes a plurality of anti-collapse bars 15 arranged at intervals on the outside of the semicircular arc section. Specifically, the continuous rigid frame box girder generally includes a plurality of aqueduct units to form a long-span continuous stacked box rigid frame aqueduct system that can be used to provide a water passage and bear loads. A composite prestressed concrete structure is used to ensure the overall structural rigidity and support performance. In this embodiment, any of the aqueduct units is taken for description.

[0034] It should be noted that the rigid frame aqueduct formed by combining the U-shaped water-passing section and the continuous rigid frame box girder is superior to the rectangular water-passing section rigid frame aqueduct in terms of water conservancy conditions and flow capacity. Moreover, under the same flow rate and the same gradient, the water weight load borne by the structure is smaller than that of the former, which reduces the impact of the inertia force of the water body shaking caused by earthquakes on the structure, can meet the needs of lightweight design, and reduce construction costs and difficulty; the U-shaped steel bundle 7 arranged to match the U-shaped water-passing section, in conjunction with the original steel bundle system, can accurately and effectively control the uniform stress state of the concrete on the water-facing surface of the U-shaped water-passing trough 5, ensuring the anti-seepage and durability functions of the aqueduct; the setting of the anti-collapse reinforcement 15 can effectively avoid the collapse of the trough surface of the U-shaped water-passing trough 5 under the tensioning action of the U-shaped steel bundle 7, which is beneficial to improving the stability of the stress state of the concrete on the water-facing surface of the U-shaped water-passing trough 5.

[0035] The above-mentioned top plate longitudinal steel bundle 9, web plate longitudinal steel bundle 10, bottom plate longitudinal steel bundle 8, web plate vertical steel bundle 11, top plate transverse steel bundle 12, middle partition plate transverse steel bundle 13, bottom plate transverse steel bundle 14 and U-shaped steel bundle 7 form a two-system four-way prestressed system. The two-system four-way prestressed system can adapt to the stiffness and stability requirements of the continuous variable-section rigid frame aqueduct with a U-shaped water-passing section, effectively control the uniform stress state of the concrete on the water-facing surface of the U-shaped water-passing channel 5, and ensure the anti-seepage and durability functions of the aqueduct.

[0036] The above-mentioned anti-collapse reinforcement 15 is provided in plurality, and the plurality of anti-collapse reinforcements 15 are evenly spaced and arranged on the outside of the above-mentioned U-shaped steel bundle 7 and extend in the direction away from the above-mentioned U-shaped steel bundle 7. A limiting hook is provided at one end of the above-mentioned anti-collapse reinforcement 15 away from the above-mentioned U-shaped steel bundle 7, and the above-mentioned limiting hook is used to hook the structural steel bars 16 in the concrete structure. At this time, the anti-collapse reinforcement 15 is in a tensioned state, applying an outward force to the U-shaped steel bundle 7 to prevent the U-shaped water trough 5 from cracking due to the tension of the U-shaped steel bundle 7.

[0037] The size design of the U-shaped water channel 5 needs to be determined based on comprehensive consideration of factors such as hydraulic design, the relationship between the maximum span and the reasonable minimum beam height, and the relationship between the minimum beam height and the flow depth. Combined with the existing prestressed steel strand technology and the crack resistance requirements of the aqueduct structure, the minimum radius of the semicircular arc part of the U-shaped water channel 5 is not less than 3m, which can effectively ensure better water conveyance capacity and structural performance.

[0038] In addition, a U-shaped steel bundle 7 is set along the inner edge of the U-shaped water channel 5 using a single-layer flat anchor. The center of the steel bundle is 15 cm away from the outer edge of the concrete, and the U-shaped steel bundle is symmetrically tensioned at both ends. That is to say, the longitudinal cross-sectional profiles of the U-shaped steel bundle 7 and the water channel 5 are similar, and the spacing between corresponding positions is the same everywhere, both 15 cm, forming a stable tensioning effect on the water-facing surface of the water channel 5, and preferably, the above-mentioned U-shaped steel bundle 7 is vertically arranged as a whole and perpendicular to the inner wall of the above-mentioned water channel 5 to ensure the integrity of the steel bundle system.

[0039] In the actual construction process, the center of the aqueduct unit is generally block O, and the aqueduct unit is generally symmetrically extended to both sides with block O as the reference to form a complete aqueduct unit. Generally speaking, the aqueduct unit includes two oppositely arranged webs 2, and a top plate 1, a middle partition 3 and a bottom plate 4 that are sequentially connected between the two webs 2 from top to bottom. The above-mentioned webs 2, the above-mentioned top plate 1 and the above-mentioned middle partition 3 form a water trough 5; the above-mentioned water trough 5, the above-mentioned bottom plate 4 and the above-mentioned middle partition 3 are all arranged with horizontal equal cross-sections; the two sides of block 0 of the above-mentioned bottom plate 4 extend upward and the inclined surface is an arc surface, and the end of the above-mentioned bottom plate 4 coincides with the above-mentioned middle partition 3 at a certain point on the corresponding side of the middle partition 3, the above-mentioned webs 2, the above-mentioned middle partition 3 and the above-mentioned bottom plate 4 form a structural groove 6, and the cross-sectional size of the above-mentioned structural groove 6 gradually decreases from block 0 to both sides. The upper end of the middle partition 3 is a circular arc concave design, and the lower end is a horizontal design, forming a U-shaped water trough 5.

[0040] For the above-mentioned two-system four-way prestressed system, the first system, namely the longitudinal section system prestressing, is composed of the top plate longitudinal steel bundle 9, the web longitudinal steel bundle 10, and the bottom plate longitudinal steel bundle 8. The second system, namely the transverse section system prestressing, is composed of the web vertical steel bundle 11, the top plate transverse steel bundle 12, the middle partition transverse steel bundle and 13, the bottom plate transverse steel bundle 14 and the U-shaped steel bundle 7 along the U-shaped water-passing section; the above-mentioned top plate longitudinal steel bundle 9 includes a plurality of first steel bundle units arranged in a horizontal row, and the first steel bundle units realize the longitudinal tensioning effect on the top plate 1; the above-mentioned web longitudinal steel bundle 10 includes a plurality of second steel bundle units arranged in a vertical row, and the plurality of the above-mentioned second steel bundles The length of the beam unit increases gradually from bottom to top, and the two ends of the above-mentioned second steel beam unit are symmetrically bent downward and extended, and the second steel beam unit realizes the longitudinal tensioning of the web 2, and in the segmented casting process, the second steel beam units of the web 2 are respectively arranged and anchored in the corresponding casting sections; the above-mentioned bottom plate longitudinal steel beam 8 includes a plurality of third steel beam units arranged in a horizontal row, and the above-mentioned third steel beam units on both sides of the above-mentioned aqueduct unit are not connected. The end of the above-mentioned third steel beam unit close to the middle of the above-mentioned aqueduct unit is bent upward, and the bottom plate longitudinal steel beam 8 realizes the longitudinal tensioning of the bottom plate 4, and the upper bent end of the above-mentioned third steel beam unit passes through the above-mentioned structural groove 6 for anchoring, and the multiple above-mentioned third steel beam units The lengths are different, and one end of the plurality of the third steel bundle units close to the middle of the aqueduct unit is spaced apart in the length direction of the aqueduct unit to pass through the lower wall of the structural groove 6 and is fixed by an anchoring structure; the web vertical steel bundle 11 includes a plurality of fourth steel bundle units arranged in vertical rows, and the fourth steel bundle units realize vertical tensioning of the web 2; the top plate transverse steel bundle 12 includes a plurality of fifth steel bundle units arranged in horizontal rows, the middle partition transverse steel bundle 13 includes a plurality of sixth steel bundle units arranged in horizontal rows, and the bottom plate transverse steel bundle 14 includes a plurality of seventh steel bundle units arranged in horizontal rows, and the seventh steel bundle units are in the middle of the aqueduct unit. The partition 3 and the bottom plate 4 are terminated at the overlapping point; the above-mentioned vertical section is arranged in a row with the above-mentioned fourth steel beam unit at the corresponding position, and the above-mentioned semicircular arc section is located above the corresponding above-mentioned sixth steel beam unit, wherein the vertical section and the fourth steel beam unit can jointly play the role of vertically tensioning the web 2, and the above-mentioned semicircular arc section and the sixth steel beam unit where the middle partition 3 is located jointly form a transverse tensioning effect on the middle partition 3, and at the same time, the shape of the U-shaped steel beam 7 matches the longitudinal section of the water channel 5, which can achieve the stress control effect on the water-facing surface of the water channel 5, and the prestressed stress control effect of the continuous rigid frame aqueduct with the U-shaped water channel 5 is better achieved through the above-mentioned overall multi-directional steel beam structure.

[0041] Moreover, this embodiment also proposes a prestressing tensioning method that matches the two-system four-way prestressing system of the variable-section stacked box rigid frame aqueduct, including: in the construction of the a-beam section of the standard cantilever symmetrical casting, first, the web vertical steel bundle 11 and the U-shaped steel bundle 7 are synchronously tensioned, and the tensioning force does not reach 100% of the preset tensioning force. Preferably, the actual tensioning force is 50% of the preset tensioning force; then, the longitudinal steel bundles, including the top plate longitudinal steel bundle 9, the web longitudinal steel bundle 10 and the bottom plate longitudinal steel bundle 8, are symmetrically tensioned, and the tensioning force reaches the preset tensioning force; the hanging basket is moved to enter the b-beam section for construction and then the corresponding transverse steel bundles in the a-beam section are tensioned. The system includes the top plate transverse steel bundle 12, the middle partition plate transverse steel bundle 13, and the bottom plate transverse steel bundle 14, and the tensioning force reaches the preset tensioning force. Finally, the web vertical steel bundle 11 and the U-shaped steel bundle 7 in the casting stage a are tensioned again to make the tensioning force reach the preset value. The above steps are a steel bundle tensioning cycle, and the construction of the prestressed system is completed by repeating multiple cycles in sequence. The a beam section and the above-mentioned b beam section are two adjacent casting beam sections in the standard cantilever symmetrical casting process. Among them, the tensioning force is proportional to the tensioning elongation. It is necessary to measure the tensioning elongation to determine whether the tensioning force of different steel bundles reaches the preset value. First tensioning the web vertical steel bundle 11 and the U-shaped steel bundle 7 can make the web 2 have a certain compressive stress reserve, which can eliminate the problem of stress concentration at the anchor position causing local cracking when the top plate longitudinal steel bundle 9, the web longitudinal steel bundle 10, and the bottom plate longitudinal steel bundle 8 are tensioned simultaneously, ensuring the stability of the overall construction process.

[0042] The tensioning force of the web vertical steel bundle 11 and the U-shaped steel bundle 7 is 50% for the first tensioning, so as to ensure that the web 2 reserves sufficient compressive stress before tensioning the top plate longitudinal steel bundle 9, the web longitudinal steel bundle 10 and the bottom plate longitudinal steel bundle 8. The web vertical steel bundle 11 and the U-shaped steel bundle 7 are partially tensioned in advance, so that the aqueduct web 2 has a certain compressive stress reserve, thereby avoiding the problem of local cracking caused by stress concentration caused by the tensioning of the longitudinal steel bundles. Moreover, after the longitudinal prestressing is in place, the remaining stress of the web vertical steel bundle 11 and the U-shaped steel bundle 7 is supplemented, thereby avoiding the weakening effect of the longitudinal prestressing on the web vertical steel bundle 11 and the U-shaped steel bundle, thereby ensuring that the concrete web 2 does not crack and the compressive stress reserve of the water-facing surface of the U-trough in the later stage.

[0043] Moreover, the tensioning method of the web vertical steel bundle 11, U-shaped steel bundle 7, top plate longitudinal steel bundle 9, web longitudinal steel bundle 10 and bottom plate longitudinal steel bundle 8 is symmetrical tensioning at both ends. Symmetrical tensioning reduces the tensioning stress loss of steel bundles with longer spans, which is convenient for accurately controlling the prestressed state; the tensioning method of the above-mentioned steel bundle top plate transverse steel bundle 12, middle partition transverse steel bundle 13 and bottom plate transverse steel bundle 14 is single-end tensioning, specifically single-end skipping beam tensioning. This transverse steel bundle has a smaller span and can achieve skipping beam tensioning after single-side anchoring, which is more efficient.

[0044] In addition, according to Figure 8 、 Figure 9As shown, the embodiment of the present application also proposes a casting hanging basket for a variable-section stacked box rigid frame aqueduct, comprising an upper truss 17 arranged at the upper end of the aqueduct unit, the upper truss 17 being provided with a first boom 18 extending downward, a height-adjustable support frame 21 being provided in the structural groove 6, a support suspension 22 being provided on the side of the support frame 21 facing the casting direction of the stacked box beam body, a bracket 23 being provided on the upper end of the support suspension 22 being flush with the top wall of the lower box, and the end of the support suspension 22 away from the stacked box beam body being detachable Connected to the above-mentioned first boom 18, the above-mentioned supporting suspension 22 can also be detachably provided with a second boom 19 extending downward, and the lower end of the above-mentioned second boom 19 is connected to the bottom template 20, and the above-mentioned first boom 18 and the above-mentioned second boom 19 are connected by a through-pin structure; it also includes a water trough 5 casting support structure, and the above-mentioned water trough 5 casting support structure includes a U-shaped inner mold 24 for casting the above-mentioned water trough 5, and the lower end of the above-mentioned upper truss 17 is provided with an abutment frame 25, and the multiple abutment joints 26 at the lower end of the above-mentioned abutment frame 25 abut against the inner wall of the above-mentioned U-shaped inner mold 24.

[0045] Specifically, a hanging basket is used to support the concrete to be poured, and beam sections are gradually and symmetrically poured on both sides of block No. 0. After the concrete is poured and cured, prestressing is implemented until the joint is closed. The initial stacked box beam body is block No. 0. After a subsequent pouring section is completed, the newly completed pouring section is used as the stacked box beam body. As the pouring progresses, the stacked box beam body gradually extends to both sides. The first boom 18 extends vertically downward. The first boom 18 is connected to the support suspension and the second boom 19. The end of the second boom 19 is connected to the bottom formwork 20 to form an integrated lifting structure; and the support suspension specifically uses the internal forming space of the lower box as a fulcrum to further support the bracket 23. This integrated comprehensive support and lifting structure can ensure stability and sufficient rigidity during the stacked box pouring process.

[0046] During the actual pouring construction process, as construction moves toward both sides, the internal size of the lower box gradually decreases, and the height of the support frame 21 needs to be continuously adjusted to ensure that the support frame 21 can be stably connected to the internal space of the lower box that has been completed in the previous pouring section to form a stable support system. When the pouring process reaches the transition section between stacked boxes and single boxes, the internal volume of the lower box of the previous pouring section approaches zero. At this time, the first boom 18 and the support suspension are disassembled, the second boom 19 and the bottom formwork 20 are disassembled, the first boom 18 and the bottom formwork 20 are installed, and the support frame 21, the support suspension and the bracket 23 are removed as a whole. At this time, the weight of the single box structure is reduced, and the bottom formwork 20 can stably support the pouring system, ensuring a stable transition from stacked boxes to single box pouring processes.

[0047] The above-mentioned upper box casting formwork structure includes a U-shaped inner mold 24 and an abutment frame 25. The upper end of the above-mentioned abutment frame 25 is connected to the above-mentioned upper truss 17 and the lower end abuts against the inner wall of the above-mentioned U-shaped inner mold 24, which is adapted to the U-shaped cross-section of the internal section of the upper box. The abutment member specifically includes a frame body. The upper end of the above-mentioned frame body is detachably connected to the above-mentioned upper truss 17, and the lower end is threadedly provided with a retractable abutment joint 26 for abutting the inner wall of the U-shaped inner mold 24. There are multiple abutment joints 26, which can abut the inner wall of the U-shaped inner mold 24 at intervals, ensuring that the range of the abutment effect is large and the uniformity is good; and the abutment joint 26 can adjust the rotation angle and is provided with an elastic abutment layer, which can ensure that it can completely fit against the inner wall of the U-shaped inner mold 24 during abutment, ensuring the best abutment effect.

Claims

1. A variable-section stacked box rigid frame aqueduct, comprising a box girder in a continuous rigid frame structure, wherein the box girder in the continuous rigid frame structure comprises at least one aqueduct unit, wherein a water trough (5) and a structural trough (6) are provided in the aqueduct unit, wherein the water trough (5) is located above the structural trough (6), and the transverse cross-sectional dimension of the structural trough (6) gradually decreases from the middle to both sides; The aqueduct unit is also provided with a two-system four-way prestressed system, including a longitudinal section system and a transverse section system, wherein the longitudinal section system includes a top plate longitudinal steel bundle (9), a web plate longitudinal steel bundle (10) and a bottom plate longitudinal steel bundle (8); the transverse section system includes a web plate vertical steel bundle (11), a top plate transverse steel bundle (12), a middle diaphragm transverse steel bundle (13) and a bottom plate transverse steel bundle (14); characterized in that, The transverse section of the water trough (5) is a U-shaped section, and the transverse section system also includes a U-shaped steel bundle (7) arranged around the outer side of the trough surface of the water trough (5), and the U-shaped steel bundle (7) includes vertical sections on both sides and a semicircular arc section in the middle, and the vertical section and the upper part of the web vertical steel bundle (11) on the corresponding side are arranged in parallel, and the semicircular arc section is located above the corresponding middle partition transverse steel bundle (13); the anti-collapse component includes a plurality of anti-collapse ribs (15) arranged at intervals on the outer side of the semicircular arc section.

2. The variable cross-section stacked box rigid frame aqueduct according to claim 1, characterized in that: The vertical surface where the U-shaped steel bundle (7) is located is perpendicular to the inner wall of the water channel (5).

3. The variable cross-section stacked box rigid frame aqueduct according to claim 1, characterized in that: The radius of the arc-shaped portion of the water channel (5) is not less than 3 m.

4. The variable cross-section stacked box rigid frame aqueduct according to claim 1, characterized in that: The top plate longitudinal steel bundle (9) includes a plurality of first steel bundle units arranged in horizontal rows; the web plate longitudinal steel bundle (10) includes a plurality of second steel bundle units arranged in vertical rows, the plurality of second steel bundle units gradually increase in length from bottom to top, and the two ends of the second steel bundle units are symmetrically bent downward and extended; the bottom plate longitudinal steel bundle (8) includes a plurality of third steel bundle units arranged in horizontal rows, the third steel bundle units on both sides of the aqueduct unit are not connected, and one end of the third steel bundle unit close to the middle of the aqueduct unit is bent upward; the web plate vertical steel bundle (11) It comprises a plurality of fourth steel bundle units arranged in vertical rows; the top plate transverse steel bundle (12) comprises a plurality of fifth steel bundle units arranged in horizontal rows; the middle partition plate transverse steel bundle (13) comprises a plurality of sixth steel bundle units arranged in horizontal rows; the bottom plate transverse steel bundle (14) comprises a plurality of seventh steel bundle units arranged in horizontal rows, and the seventh steel bundle units terminate at the overlapped position of the middle partition plate (3) and the bottom plate (4) of the aqueduct unit; the vertical section is arranged in a row with the fourth steel bundle units at corresponding positions, and the semicircular arc section is located above the corresponding sixth steel bundle unit.

5. The variable cross-section stacked box rigid frame aqueduct according to claim 4, characterized in that: The upper bent end of the third steel bundle unit passes through the structural groove (6) and is anchored, and the lengths of the plurality of third steel bundle units are different, and one end of the plurality of third steel bundle units close to the middle of the aqueduct unit passes through the lower wall of the structural groove (6) at intervals in the length direction of the aqueduct unit and is fixed by an anchor block.

6. Prestressing method, characterized in that: The method is used to perform prestressing on the variable-section stacked box rigid frame aqueduct as described in any one of claims 1 to 5, comprising: In the a beam section, first, the web vertical steel bundle (11) and the U-shaped steel bundle (7) are tensioned synchronously and the tensioning force does not reach 100% of the preset tensioning force. Then, the top plate longitudinal steel bundle (9), the web longitudinal steel bundle (10) and the bottom plate longitudinal steel bundle (8) are tensioned simultaneously and the tensioning force reaches the preset tensioning force. After the hanging basket is moved into the b beam section, the corresponding top plate transverse steel bundle (12), the middle partition transverse steel bundle (13) and the bottom plate transverse steel bundle (14) in the a beam section are tensioned and the tensioning force reaches the preset tensioning force. Finally, the web vertical steel bundle (11) and the U-shaped steel bundle (7) in the a casting stage are tensioned again simultaneously to make the tensioning force reach the preset tensioning force. The above steps constitute a steel bundle tensioning cycle, and the prestressing is completed by repeating multiple cycles in sequence. The a beam section and the b beam section are two adjacent casting beam sections in the standard cantilever symmetrical casting process.

7. The construction method of the prestressed system of the variable cross-section stacked box rigid frame aqueduct according to claim 6 is characterized in that: The tensioning force of the first tensioning web vertical steel strand (11) and the U-shaped steel strand (7) is 50%.

8. The construction method of the prestressed system of the variable cross-section stacked box rigid frame aqueduct according to claim 7 is characterized in that: The tensioning method of the web vertical steel bundle (11), the U-shaped steel bundle (7), the top plate longitudinal steel bundle (9), the web longitudinal steel bundle (10) and the bottom plate longitudinal steel bundle (8) is symmetrical tensioning at both ends, and the tensioning method of the top plate transverse steel bundle (12), the middle partition transverse steel bundle (13) and the bottom plate transverse steel bundle (14) is single-end tensioning.

9. A casting hanging basket for a variable-section stacked box rigid frame aqueduct, characterized in that: The casting hanging basket is used for casting and molding the variable-section stacked box rigid frame aqueduct as described in any one of claims 1 to 5, comprising an upper truss (17) arranged at the upper end of the aqueduct unit, the upper truss (17) being provided with a first hanging arm (18) extending downward, a support frame (21) with adjustable height being provided in the structural groove (6), a support suspension (22) being provided on one side of the support frame (21) facing the casting direction of the stacked box beam body, a bracket (23) being provided at the upper end of the support suspension (22) being flush with the top wall of the lower box, and the support suspension (22) being away from the upper end of the lower box. One end of the stacked box beam body is detachably connected to the first boom (18), and the supporting suspension (22) is also detachably provided with a second boom (19) extending downward, and the lower end of the second boom (19) is connected to a bottom formwork (20); it also includes a water trough (5) casting support structure, and the water trough (5) casting support structure includes a U-shaped inner formwork (24) for casting the water trough (5), and the lower end of the upper truss (17) is provided with an abutment frame (25), and a plurality of abutment joints (26) at the lower end of the abutment frame (25) abut against the inner wall of the U-shaped inner formwork (24).

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