A construction method for cable-stayed bridge towers with improved crack resistance of lower beams

Abstract

The present invention provides a construction method for a cable-stayed bridge tower that improves the crack resistance of the lower crossbeam. The method comprises pre-embedding multiple layers of transverse prestressed pipes in the pedestal and providing a vertical through-slit at the transverse center of the pedestal. A first temporary prestressed bundle is first tensioned and anchored, the lower crossbeam segment is constructed, and a first full-length prestressed bundle and a second full-length prestressed bundle are pre-embedded. The middle tower column and the middle crossbeam of the arch frame are then constructed using climbing formwork. Multiple horizontal cross braces are provided in the middle area of ​​the middle tower column. A second temporary prestressed bundle is then tensioned and anchored into the remaining transverse prestressed bundles in the pedestal to resist the horizontal component of the lower tower column. The full-length prestressed bundle is then tensioned. The temporary prestressing of the pedestal and the steel casing cofferdam are then removed, and construction of the remaining pedestal structure is continued. The present invention can effectively improve the crack resistance of the lower crossbeam, solving the problems of microcracks, large shrinkage deformation, and cracking risks caused by high temperature stress in the lower crossbeams of conventional pedestals, as well as the difficulty in ensuring the durability of the pedestal prestress.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering, and in particular relates to a construction method of a cable-stayed bridge tower for improving the crack resistance of a lower cross beam. Background Art

[0002] High-speed trains have relatively stringent requirements on the smoothness (deformation) control of the track. High-speed railway ballastless tracks are usually laid continuously on top of bridge structures, which requires the bridge structure to provide sufficient support stiffness for the track.

[0003] For long-span ballastless track cable-stayed bridges, a combined road-rail steel truss is often used to increase the vertical stiffness of the main beam. Large-cross-section concrete lower crossbeams are also used at the pylons to provide sufficient vertical support stiffness for the main beam. For both aesthetic and economic reasons, long-span cable-stayed bridges typically utilize elevated pile caps, with the top of the cap placed near the horizontal plane (ground level). The cap also serves as the foundation for the lower crossbeam supports. For economic reasons, in addition to ensuring necessary navigation clearance for river-crossing bridges, the bridge deck is kept as close to the horizontal plane as possible to reduce bridge height and investment. However, a low deck height reduces the height of the lower tower columns between the lower crossbeam and the cap.

[0004] Conventional large-span river-crossing ballastless track cable-stayed bridge towers have a high risk of cracking under the following reasons: (1) Micro cracks exist inside the concrete lower beam during construction, which makes it easy to crack under the huge dead load and live load transmitted by the support; (2) Considering the shrinkage of concrete, the age of the pedestal is longer than that of the lower beam. The shrinkage of the pedestal concrete has been basically completed before the construction of the lower beam is completed. After the structural system is formed, the lower beam with the shortest age will produce the most shrinkage effect. Under the strong constraints of the short lower tower column and the pedestal, the risk of shrinkage cracking of the lower beam is extremely high; (3) Since the pedestal is usually located in the horizontal direction, the pedestal is relatively stable. Below the surface, the temperature changes slightly, but the lower crossbeam is exposed to solar radiation and ambient temperature, and the temperature of the structure changes greatly. In the extremely rigid frame system composed of the pedestal, the lower tower columns on both sides, and the lower crossbeam, a large system temperature self-stress will be generated. In particular, when the ambient temperature drops, the temperature tensile stress borne by the lower tower columns may cause structural cracking; (4) Among the common cable tower forms, the A-shaped tower and the inverted Y-shaped tower have a large horizontal component at the bottom of the tower column, and prestressing needs to be set in the transverse direction of the pedestal to balance the horizontal component of the tower column. However, the pedestal is located in a dry-wet alternating zone, and the durability of the prestressed beam is difficult to guarantee.

[0005] In summary, the lower crossbeams of cable-stayed bridge towers, particularly those on long-span ballastless track cable-stayed bridges, are subject to microcracks, significant shrinkage deformation, and the risk of cracking due to high thermal stresses during construction. Furthermore, the durability of the prestressed tendons in the abutment is difficult to guarantee. Therefore, it is necessary to propose a construction method for cable-stayed bridge towers that improves the crack resistance of the lower crossbeams to address or at least alleviate these shortcomings. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a construction method for cable-stayed bridge towers that improves the crack resistance of the lower beam, so as to solve the technical problem that the lower beams of cable-stayed bridge towers in the existing technology, especially the lower beams of cable-stayed bridge towers with large span ballastless tracks, have a great risk of cracking.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A construction method for a cable-stayed bridge tower for improving the crack resistance of a lower crossbeam comprises the following steps:

[0009] S1: Construction of bridge pile foundation and cap steel box cofferdam;

[0010] S2: tying the cap steel mesh, pre-embedding multiple layers of transverse prestressed pipes spaced apart vertically in the cap steel mesh, each layer of the transverse prestressed pipes comprising multiple transverse prestressed pipes spaced apart longitudinally; fixing a plurality of fillers for forming vertical through-slots at the centerline of the cap wide side; pouring the cap concrete, and tensioning and anchoring the first temporary prestressed tendons to some of the transverse prestressed pipes;

[0011] S3: Tie the tower column steel mesh to the height of the bottom edge of the lower crossbeam and pour concrete; cast the lower crossbeam in sections to obtain several pre-cast sections. Each pre-cast section contains several long prestressed pipes. The long prestressed pipes of two adjacent pre-cast sections are connected in the transverse direction. These long prestressed pipes form the first full-length prestressed pipe.

[0012] S4: Continue constructing the tower column in sections, and pre-embed a second full-length prestressed pipe in the tower column steel mesh, which corresponds to and connects with the first full-length prestressed pipe; the outer end of the second full-length prestressed pipe extends outward to the outside of the middle tower column;

[0013] Continue to construct the tower columns, middle beams, and horizontal cross braces. When constructing the horizontal cross braces, tension and anchor the second temporary prestressed tendon into the remaining transverse prestressed pipes in the cap to resist the horizontal component of the lower tower column.

[0014] S5: sequentially pouring concrete at the joints between the first-cast segments of the lower crossbeam, and tensioning the full-length prestressed tendons. The full-length prestressed tendons pass through the first full-length prestressed pipe and the second full-length prestressed pipe. Both ends of the full-length prestressed tendons are anchored to the outside of the middle tower column. After all the full-length prestressed tendons are tensioned, grouting is promptly performed to seal the first full-length prestressed pipe, the second full-length prestressed pipe, and the corresponding anchor heads.

[0015] While the full-length prestressed tendons are being tensioned, the first and second temporary prestressed tendons are being released in equal proportion and removed, and the transverse prestressed pipes are being sealed by grouting.

[0016] S6: Remove the steel casing cofferdam of the foundation and continue to construct the remaining cable tower structure to complete the cable tower construction.

[0017] Furthermore, the specific steps of constructing the first cast section of the lower beam in step S3 include:

[0018] S31: erecting a lower crossbeam support on the top of the platform, and performing overload preloading on the lower crossbeam support;

[0019] S32: Erecting the inner and outer formwork of the lower cross beam in sections along the transverse direction of the bridge, tying the steel mesh of the lower cross beam of each section, and pre-embedding the long and short prestressed pipes of each section, and then pouring concrete to obtain a plurality of lower cross beam precast sections arranged at intervals along the transverse direction of the bridge;

[0020] According to the overall stress state of the lower cross beam, the first cast section of the lower cross beam is divided into the first cast section of the lower cross beam in the positive bending moment area and the first cast section of the lower cross beam in the negative bending moment area; the long prestressed pipe is configured according to the overall stress state of the lower cross beam; the short prestressed pipe of the first cast section of the lower cross beam in the positive bending moment area is arranged in the bottom plate, and the lower segment prestressed tendons are tensioned therein when the first cast section of the lower cross beam is prefabricated; the short prestressed pipe of the first cast section of the lower cross beam in the negative bending moment area is arranged in the top plate, and the upper segment prestressed tendons are tensioned therein when the first cast section of the lower cross beam is prefabricated.

[0021] Furthermore, the number of the first cast sections of the lower crossbeam is an odd number, and a medium-length prestressed pipe is pre-buried in the first cast sections of the lower crossbeam; in step S5, when pouring the joint concrete between the first cast sections of the lower crossbeam, the following steps are also included:

[0022] S51: First, cast the joint concrete between the three precast segments of the lower cross beam located in the mid-span area of ​​the lower cross beam to form a first segment combination; after the joint concrete of the first segment combination reaches a certain strength, tension and anchor the first permanent prestressed tendon in the mid-length prestressed pipe of the first segment combination; the first permanent prestressed tendon runs through the entire first segment combination;

[0023] S52: Continue pouring the joint concrete between the first segment combination and the adjacent lower beam precast segment to form a second segment combination; adjust the second segment combination to the corresponding first segment combination; tension and anchor a first permanent prestressed tendon in the mid-length prestressed conduit of the first segment combination; the first permanent prestressed tendon runs through the entire first segment combination;

[0024] S53: Repeat step S52 until the joint concrete between all the lower beam precast segments is poured, tension and anchor the second permanent prestressed tendons that pass through all the lower beam precast segments to obtain the maximum segment combination.

[0025] Furthermore, the first permanent prestressed tendon and the second permanent prestressed tendon are arranged at the upper edge, the lower edge, or both the upper and lower edges of the lower beam segment combination; the first segment combination can be less equipped with or not equipped with the first permanent prestressed tendon at the upper edge, and the largest segment combination can be less equipped with or not equipped with the second permanent prestressed tendon at the lower edge.

[0026] Furthermore, the step S53 further includes the following steps:

[0027] The beam-column joint between the lower cross beam and the tower column is cast; ultra-high performance concrete or fiber concrete is used to cast the upper edge of the beam-column joint within a thickness range of 10 to 20 cm.

[0028] Furthermore, in step S5, the steps of proportionally extending the first temporary prestressed tendons and the second temporary prestressed tendons are as follows:

[0029] The full-length prestressed tendons are tensioned in batches, and the first temporary prestressed tendons and / or the second temporary prestressed tendons are tensioned in equal proportions at the same time; wherein, when tensioning the full-length prestressed tendons of the i-th batch, the first temporary prestressed tendons and / or the second temporary prestressed tendons of the i-th batch are tensioned, and the full-length prestressed tendons tensioned in the i-th batch account for 15% to 35% of all the full-length prestressed tendons; the proportion of the first temporary prestressed tendons and / or the second temporary prestressed tendons tensioned in the i-th batch to all the temporary prestressed tendons is denoted as the first proportion, and the proportion of the full-length prestressed tendons tensioned in the i-th batch to all the full-length prestressed tendons is denoted as the second proportion, and the difference between the first proportion and the second proportion is no more than 10%; i is a positive integer, 3≤i≤6.

[0030] Furthermore, the number of transverse prestressed pipe layers in the pedestal is 2 to 5 layers, the uppermost layer of the transverse prestressed pipe layer is not less than 50 cm from the top surface of the pedestal, and the lowermost layer of the transverse prestressed pipe layer is not less than 100 cm from the bottom surface of the pedestal.

[0031] Furthermore, the first temporary prestressed tendons and the second temporary prestressed tendons are evenly spaced vertically. In step S2, the tensioned first temporary prestressed tendons account for 20% to 40% of the total number of temporary prestressed tendons.

[0032] Furthermore, in step S4, the horizontal component of the lower tower column is calculated according to the horizontal cross brace, and the second temporary prestressed beam is tensioned in batches or all at once according to the horizontal component of the lower tower column; when tensioning in batches, the first batch of second temporary prestressed beams is tensioned when the horizontal component of the tower column reaches more than 80% of the design value of the first temporary prestressed beam; when the horizontal component of the tower column reaches 80% of the tensioned temporary prestressed beam again, a new batch of second temporary prestressed beams is tensioned, and this process is repeated.

[0033] Furthermore, the vertical through-slit is disconnected along the longitudinal bridge direction of the pedestal, the width of the vertical through-slit is 1 to 5 cm, and the filling body is made of elastic material.

[0034] The beneficial effects of the present invention are:

[0035] (1) The pedestal of the present invention can effectively reduce the foundation stiffness by setting vertical through-slits, avoiding the risk of cracking caused by the high temperature self-stress and secondary stress effect of the high-rigidity frame formed by the lower crossbeam, lower tower column and pedestal, overcoming the problem that when the lower tower column is too short, only a corbel structure with poor local stress can be used, and the lower crossbeam of the cable tower can be widened to a cable tower structure with an ultra-short lower tower column;

[0036] (2) The present invention reduces the horizontal stiffness requirement of the pile group foundation by arranging the first temporary prestressed beam and the second temporary prestressed beam on the cap, which is beneficial to saving the construction cost; the cap steel box cofferdam is removed after the first temporary prestressed beam and the second temporary prestressed beam are removed, which ensures a dry working environment for the first temporary prestressed beam and the second temporary prestressed beam, and ensures the durability of the prestressed beam;

[0037] (3) The present invention adopts the method of segmented casting of the lower crossbeam, which can effectively reduce the volume of single concrete casting, solve the risk of casting interruption caused by insufficient water concrete transportation capacity, and reduce the risk of initial micro cracks in the lower crossbeam caused by bracket deformation; at the same time, it is convenient to configure the segmented prestressed beams and the first and second permanent prestressed beams, and eliminates the construction of prestressed anchor teeth, which is convenient for formwork processing, and has convenient construction, reliable force and good durability; the first cast segment of the lower crossbeam has a certain beam storage period before forming the system, and the concrete shrinkage is basically completed, reducing the risk of structural cracking after the bridge is completed;

[0038] In short, the present invention can effectively improve the crack resistance of the lower crossbeam, solve the problems of microcracks in the lower crossbeam of conventional cable towers, large shrinkage deformation, cracking risks caused by high temperature stress, and difficulty in ensuring the durability of the prestressed foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them:

[0040] Figure 1 This is a schematic structural diagram corresponding to step S1 in an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the structure corresponding to step S2 in an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of the structure corresponding to step S31 in an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the structure corresponding to step S32 in an embodiment of the present invention;

[0044] Figure 5 This is a schematic structural diagram corresponding to step S4 in an embodiment of the present invention;

[0045] Figure 6 Schematic diagram of the structure corresponding to step S51 in an embodiment of the present invention;

[0046] Figure 7 Schematic diagram of the structure of the tower column in the continuous climbing formwork construction in step S4 in an embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram of the structure of the middle crossbeam after the middle crossbeam is constructed in step S4 of the embodiment of the invention;

[0048] Figure 9 This is a schematic structural diagram corresponding to step S5 in an embodiment of the present invention;

[0049] Figure 10 This is a schematic structural diagram corresponding to step S6 in an embodiment of the present invention;

[0050] Figure 11 Schematic diagram of the overall structure after forming in an embodiment of the present invention;

[0051] Figure 12 is a schematic elevation view of a lower crossbeam in an embodiment of the present invention;

[0052] Figure 13 is a schematic plan view of a lower crossbeam in an embodiment of the present invention;

[0053] Figure 14 is one of the cross-sectional schematic diagrams of the lower crossbeam in an embodiment of the present invention;

[0054] Figure 15 FIG2 is a second cross-sectional schematic diagram of the lower cross beam in an embodiment of the present invention;

[0055] Figure 16 This is the third cross-sectional schematic diagram of the lower cross beam in the embodiment of the present invention.

[0056] Figure 17 is a force analysis diagram of the lower crossbeam in an embodiment of the present invention;

[0057] Figure 18 Schematic diagram of the position of the permanent prestressed tendons of the maximum segment combination with 3 segments in an embodiment of the present invention.

[0058] Figure 19Schematic diagram of the position of permanent prestressed tendons in a maximum segment combination of five segments in an embodiment of the present invention.

[0059] Figure 20 Schematic diagram of the position of permanent prestressed tendons in a maximum segment combination of 7 segments in an embodiment of the present invention.

[0060] Figure 21 Schematic diagram of the position of permanent prestressed tendons in a maximum segment combination of 9 segments in an embodiment of the present invention.

[0061] Figure: 10, bridge pile foundation; 20, cap steel box cofferdam; 30, cap; 310, transverse prestressed pipe layer; 311, transverse prestressed pipe; 312, water-stop sleeve; 320, vertical through-hole; 330, first temporary prestressed beam; 340, second temporary prestressed beam; 40, lower tower column; 50, lower crossbeam; 510, full-length prestressed beam; 520, lower crossbeam support; 530, long prestressed pipe; 540, lower crossbeam precast segment ; 541. Prestressed tendons of the upper segment; 542. Prestressed tendons of the lower segment; 550. First segment combination; 551. First permanent prestressed tendons; 552. Second permanent prestressed tendons; 60. Middle tower column; 610. Horizontal cross brace; 620. Beam-column joint; 630. Ultra-high performance concrete; 710. Transverse full-height diaphragm; 730. Transverse half-height diaphragm; 740. Support and pad stone; 810. Middle cross beam; 820. Upper tower column; 830. Tower crown. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present invention.

[0063] In the description of the present invention, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0064] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0065] like Figures 1 to 16 As shown, a construction method for a cable-stayed bridge tower for improving the crack resistance of the lower cross beam comprises the following steps:

[0066] S1: Construction of bridge pile foundation 10 and cap steel box cofferdam 20;

[0067] S2: Tie the reinforcement mesh of the cap 30, embedding multiple layers of transverse prestressed pipes 310 spaced apart vertically in the reinforcement mesh of the cap 30, each layer of transverse prestressed pipes 310 comprising multiple transverse prestressed pipes 311 spaced apart longitudinally; fix a plurality of fillers (not shown) at the centerline of the wide side of the cap 30 to form vertical through-slits 320; pour concrete for the cap 30, and tension and anchor the first temporary prestressed tendons 330 to some of the transverse prestressed pipes 311 after the concrete reaches 75% of the design strength; 75% of the design strength is a preferred value, and those skilled in the art may also set other values ​​based on actual needs;

[0068] S3: Tie the steel mesh of the lower tower column 40 in sections and pour concrete to obtain the lower tower column 40 , and construct the lower tower column 40 to the height of the bottom edge of the lower cross beam 50 ;

[0069] The steel mesh of the lower cross beam 50 is tied in sections, and a plurality of first full-length prestressed pipes arranged at intervals along the vertical direction are pre-embedded in the steel mesh of the lower cross beam 50. The lower cross beam 50 is then cast in sections to obtain lower cross beam pre-cast sections 540. A plurality of long prestressed pipes 530 are installed in each lower cross beam pre-cast section 540. The long prestressed pipes 530 of two adjacent lower cross beam pre-cast sections 540 are connected in the transverse direction. These long prestressed pipes 530 form a first full-length prestressed pipe. The first full-length prestressed pipe extends in the transverse direction as a whole, for the corresponding full-length prestressed bundle 510 to pass through.

[0070] S4: Tie the steel mesh of the middle tower column 60 in sections and pre-embed the second full-length prestressed pipe in the steel mesh of the middle tower column 60, which is arranged one-to-one with the first full-length prestressed pipe. Continue to construct the middle tower column 60 and the cross beam 810 in the arch frame, and set a plurality of horizontal cross braces 610 arranged at intervals along the vertical direction in the middle area of ​​the middle tower column 60. When constructing the horizontal cross braces, tension and anchor the second temporary prestressed beam 340 into the remaining transverse prestressed pipe 311 in the pedestal 30 to resist the horizontal component of the lower tower column 40. The water flow of the structure The horizontal force increases with the number of horizontal cross braces. Ideally, a certain number of second temporary prestressed tendons 340 are tensioned each time a horizontal cross brace is constructed. Given the complexity of construction, it may be considered to tension the second temporary prestressed tendons 340 all at once before constructing the first horizontal cross brace. The second full-length prestressed conduit includes a first end (not shown) and a second end (not shown) that are relatively disposed. The first end extends inwardly and connects to the first full-length prestressed conduit, and the second end extends outwardly to the outside of the middle tower column 60.

[0071] S5: sequentially pouring concrete in the joints between the first pouring segments 540 of the lower crossbeam, and tensioning the full-length prestressed tendons 510. The full-length prestressed tendons 510 pass through the first full-length prestressed pipe and the second full-length prestressed pipe. The ends of the full-length prestressed tendons 510 are respectively anchored to the outside of the middle tower column 60. After all the full-length prestressed tendons 510 are tensioned, grouting is promptly performed to seal the first full-length prestressed pipe, the second full-length prestressed pipe, and the corresponding anchor heads. Steps S4 and S5 can be performed simultaneously.

[0072] While the full-length prestressed tendons 510 are being tensioned, the first temporary prestressed tendons 330 and the second temporary prestressed tendons 340 are proportionally released and removed, and the transverse prestressed pipes 311 are sealed by grouting.

[0073] S6: Remove the foundation steel box cofferdam 20 and continue to construct the remaining cable tower structure to complete the cable tower construction; the remaining cable tower structure includes conventional components such as the upper tower column 820, the tower crown 830, the support and the pad stone 740, which will not be described in detail here.

[0074] The present application reduces the horizontal stiffness requirement of the pile group foundation by setting the first temporary prestressed beam 330 and the second temporary prestressed beam 340 on the pedestal 30, which is beneficial to saving the project cost; the pedestal steel casing cofferdam 20 is removed after the first temporary prestressed beam 330 and the second temporary prestressed beam 340 are removed, thereby ensuring a dry working environment for the first temporary prestressed beam 330 and the second temporary prestressed beam 340 and ensuring the durability of the prestressed beams.

[0075] like Figures 2 to 11As shown, by fixing a filler for forming a vertical through-slit 320 at the transverse center of the pedestal 30, that is, the filler is filled in the vertical through-slit 320, a vertical through-slit 320 can be formed at the transverse center of the pedestal 30 after pouring the concrete of the pedestal 30; the pedestal 30 of the present application adopts the vertical through-slit 320 treatment, which can effectively reduce the foundation stiffness, avoid the high temperature self-stress and secondary stress effect of the high-rigidity frame formed by the lower crossbeam 50, the lower tower column 40 and the pedestal 30, and overcome the problem that only a corbel structure with poor local stress can be used when the lower tower column is too short (a cable tower with a too short lower tower column cannot be provided with a lower crossbeam, otherwise the temperature stress will be too large and cracking will occur, and a corbel is usually used instead, but the use of a corbel will lead to poor local stress), and the lower crossbeam 50 of the cable tower can be widened to a cable tower structure with an ultra-short lower tower column 40.

[0076] In addition, the vertical through-slits 320 are provided in the pedestal 30 to make the stress pattern of the structure clearer and eliminate the influence of the secondary internal force of the structural temperature. The temporary prestressed beam can be used to balance the horizontal force of the tower column. After the construction of the lower crossbeam 50 is completed, the horizontal force of the tower column is transferred to the lower crossbeam 50. After the first temporary prestressed beam 330 and the second temporary prestressed beam 340 are removed, the pedestal steel casing cofferdam 20 is removed to avoid the difficulty of underwater prestressed beam maintenance. There is no need to set permanent prestressed beams in the pedestal 30. Therefore, there will be no problem that the durability of the prestressed beams of the conventional pedestal 30 is difficult to ensure. Compared with the conventional cable tower structure, it has significant advantages from the perspective of stress, economy and structural durability.

[0077] As a good example, Figures 2 to 11 As shown, the vertical through-slit 320 is disconnected along the longitudinal bridge direction of the pedestal 30. The width of the vertical through-slit 320 is 1 to 5 cm. The filling body is made of elastic material, which can be one or more of asphalt hemp, asphalt oil felt, and rubber sheet.

[0078] As a preferred example, Figure 2 As shown, after pre-embedding multiple layers of transverse prestressed pipe layers 310 arranged at intervals along the vertical direction in the steel mesh of the base 30 in step S2, the step also includes: arranging a water-stop sleeve 312 near the vertical through-slit 320 of each transverse prestressed pipe 311; wherein, the water-stop sleeve 312 is sealingly sleeved on the peripheral wall of the transverse prestressed pipe 311; by arranging the water-stop sleeve 312, water seepage from the vertical through-slit 320 can be effectively prevented from entering the transverse prestressed pipe 311 and affecting the durability of the temporary prestressed bundle.

[0079] like Figure 4As shown, the number of transverse prestressed pipe layers 310 in the cap 30 is 2 to 5. The topmost layer of the transverse prestressed pipe layer 310 is at least 50 cm from the top surface of the cap 30, and the bottommost layer of the transverse prestressed pipe layer 310 is at least 100 cm from the bottom surface of the cap 30. It is understood that 2 to 5 layers of transverse prestressed pipe layers 310 is the preferred number. Multiple layers of transverse prestressed pipe layers 310 can be evenly spaced vertically. In other embodiments, those skilled in the art can further configure a specific number of layers or other numbers of layers based on actual needs.

[0080] As a preferred example, the specific steps of constructing the lower beam precast segment 540 in step S3 include:

[0081] S31: If Figure 3 As shown, a lower crossbeam support 520 is set up on the top of the platform 30, and the lower crossbeam support 520 is overloaded and pre-loaded;

[0082] S32: Erecting the inner and outer formwork of the lower cross beam 50 in sections along the transverse direction of the bridge, tying the steel mesh of the lower cross beam 50 of each section, and pre-embedding the long prestressed pipe 530 of each section, and then pouring concrete to obtain a plurality of lower cross beam precast sections 540 arranged at intervals along the transverse direction of the bridge;

[0083] like Figure 17 As shown, according to the overall stress state of the lower beam 50, the lower beam pre-cast segment 540 is divided into a lower beam pre-cast segment in the positive bending moment area and a lower beam pre-cast segment in the negative bending moment area; the prestressed pipe is configured according to the overall stress state of the lower beam 50;

[0084] The short prestressed pipe of the lower cross beam first cast segment in the positive bending moment area is set in the bottom plate, and the lower segment prestressed beam 542 is tensioned inside the lower cross beam first cast segment when the lower cross beam first cast segment is prefabricated; the short prestressed pipe of the lower cross beam first cast segment in the negative bending moment area is set in the top plate, and the upper segment prestressed beam 541 is tensioned inside the lower cross beam first cast segment when the lower cross beam first cast segment is prefabricated.

[0085] like Figure 17 As shown, Figure 17It includes a force diagram of the lower crossbeam 50; specifically, the prestressing force of the lower crossbeam 50 should take into account the effects of the horizontal component of the tower column and the reaction force of the support of the lower crossbeam 50, that is, there is still a certain surplus after balancing the horizontal component of the tower column to withstand the bending moment caused by the reaction force of the top support of the lower crossbeam 50, to ensure that the upper and lower edges of the concrete of the lower crossbeam 50 are not subject to tension under the limit state of normal use; therefore, in this embodiment, a corresponding short prestressed pipe is pre-buried at the bottom of the segment located in the mid-span area of ​​the lower crossbeam (positive bending moment area) for the lower segment prestressed beam 542 to pass through; and a corresponding short prestressed pipe is pre-buried at the top of the segment in the root area of ​​the lower crossbeam (negative bending moment area) for the upper segment prestressed beam 541, ultimately ensuring that the upper and lower edges of the concrete of the lower crossbeam 50 are not subject to tension under the limit state of normal use.

[0086] As a preferred embodiment, Figures 12 to 16 As shown, each lower cross beam precast segment 540 is a box-section concrete structure; Figure 12 、 Figure 13 The joint concrete has not yet been poured. Figure 13 The embedded channel in the middle is schematically marked, and the embedded channels at the front and rear sides are not drawn; Figure 14 This is a cross-sectional view of the first cast segment 540 of the lower beam corresponding to the transverse full-height partition 710. Figure 15 This is a cross-sectional view of the precast segment 540 of the lower beam corresponding to the transverse half-height partition 730. Figure 16 The cross-sectional view of the precast segment 540 of the lower beam without the partition is shown.

[0087] There are three types of pre-buried channels in the first cast segment of the lower cross beam 540, namely, a long prestressed pipe for the full-length prestressed bundle 510 to pass through, a short prestressed pipe for the upper segment prestressed bundle 541 or the lower segment prestressed bundle 542 to pass through, and a medium-length prestressed pipe for the first permanent prestressed bundle 551 or the second permanent prestressed bundle 552 to pass through. These pre-buried channels are arranged in the top plate, bottom plate and web plate of the box-shaped first cast segment cross beam 540 according to needs; the full-length prestressed bundle 510 passes through the lower cross beam, and its end is anchored on the outside of the middle tower column. The quasi-through-length prestressed beam 510 is a conventional practice in this field; the first permanent prestressed beam 551 runs through several lower beam precast segments 540; the second permanent prestressed beam 552 runs through all lower beam precast segments 540; the upper segment prestressed beam 541 and the lower segment prestressed beam 542 are arranged on a single lower beam precast segment 540; in the present invention, the arrangement of the upper segment prestressed beam 541, the lower segment prestressed beam 542, the first permanent prestressed beam 551, and the second permanent prestressed beam 552 can effectively resist the positive bending moment in the mid-span area of ​​the lower beam (the bending moment diagram of the lower beam is shown in Figure 17In the present invention, by arranging the above-mentioned prestressed tendons that match the internal forces (bending moments) of the completed bridge at an early stage, the number of full-length prestressed tendons 510 can be effectively reduced, the total amount of prestressed steel tendons used can be reduced, and thus the project cost can be lowered. In addition, the upper segment prestressed tendons 541, the lower segment prestressed tendons 542, the first permanent prestressed tendons 551, and the second permanent prestressed tendons 552 do not require anchoring teeth, and thus have a simple structure, convenient construction, reliable force bearing, and good durability.

[0088] In this embodiment, the lower cross beam 50 adopts a box-shaped concrete section with a top plate and longitudinal and transverse partitions, which can effectively distribute the vertical force to the various webs and partitions of the lower cross beam 50, and can prevent the local stress deformation of the top plate from being too large and causing cracking; in addition, the transverse full-height partition 710 and the transverse half-height partition 730 can both meet the requirements of force transmission (can transmit shear force to the web to make the web bear uniform force), and at the same time, the transverse half-height partition 730 has a simple structure and saves materials. By setting the transverse full-height partition 710 and the transverse half-height partition 730, the partition steel bars do not need to be anchored in the bottom plate of the lower cross beam pre-cast section 540 where steel bars and prestressed tendons are densely distributed. In particular, the transverse half-height partition 730 reduces the cross-embedded steel bars, making it easier to ensure construction quality, and the vertical force transmission effect is equivalent to that of the transverse full-height partition 710; in a preferred example, torsional force usually only requires one transverse full-height partition 710. The possibility of later cracking of the transverse full-height partition 710 due to uneven stress on the connected panels is avoided.

[0089] As a preferred embodiment, the number of the pre-cast segments 540 of the lower crossbeam is an odd number (3, 5, 7, 9, ...) not less than 3, and a certain width of post-cast joints is provided between the segments, which can be set according to actual needs. In step S5, when pouring the joint concrete between the pre-cast segments 540 of the lower crossbeam, the following steps are also included:

[0090] S51: If Figure 6 As shown, the joint concrete between the three lower beam precast segments 540 located in the mid-span area of ​​the lower beam is first poured to form a first segment assembly 550. After the joint concrete of the first segment assembly 550 reaches 75% of the design strength, a first permanent prestressed beam 551 is tensioned and anchored in the prestressed mid-track of the first segment assembly 550. The first permanent prestressed beam 551 runs through the entire first segment assembly.

[0091] S52: Continue pouring the joint concrete between the first segment assembly 550 and the adjacent lower beam precast segment 540 to form a second segment assembly; adjust the second segment assembly to the corresponding first segment assembly; tension and anchor another first permanent prestressed tendon in the mid-length prestressed conduit of the first segment assembly; the first permanent prestressed tendon runs through the entire first segment assembly;

[0092] S53: Repeat step S52 until the joint concrete between all the first-cast segments of the lower crossbeam is poured, and tension and anchor the second permanent prestressed tendons that pass through all the first-cast segments of the lower crossbeam to obtain the maximum segment combination;

[0093] According to the stress conditions of the lower crossbeam 50, the first permanent prestressed tendon is only tensioned in the first cast segment of the lower crossbeam in the positive bending moment area, and the first permanent prestressed tendon is arranged in the bottom plate of the largest segment combination; the second permanent prestressed tendon is arranged in the top plate of the largest segment combination; the first permanent prestressed tendon 551 and the second permanent prestressed tendon 552 are calculated according to the length of the lower crossbeam, and the first permanent prestressed tendon 551 and the second permanent prestressed tendon 552 are arranged near the edge of the concrete. If the space position permits, they can be staggered left and right, and can be divided into one layer or more layers; the first permanent prestressed tendon 551 and the second permanent prestressed tendon 552 are arranged at the upper edge, lower edge, or both the upper and lower edges of the lower crossbeam segment combination; the first segment combination can be less equipped with or not equipped with the first permanent prestressed tendon 551 at the upper edge; the largest segment combination can be less equipped with or not equipped with the second permanent prestressed tendon 552 at the lower edge; the prestressed tendons in the corresponding area should be tensioned in time after pouring any joint, otherwise there will be a risk of cracking at the joint. It is worth noting that the use of segmented casting of the lower crossbeam 50 in this embodiment can effectively reduce the volume of single concrete pouring, solve the risk of pouring interruption caused by insufficient water concrete transportation capacity, and reduce the risk of initial microcracks in the lower crossbeam 50 due to bracket deformation; at the same time, it is convenient to configure prestressed stress in sections, and eliminates the construction of prestressed anchor tooth blocks, which is convenient for formwork processing; the lower crossbeam segment 540 cast first has a certain beam storage period before forming the system, and basically completes the concrete shrinkage, reducing the risk of structural cracking after the bridge is completed.

[0094] In one embodiment, the lower cross beam 50 has three sections, such as Figure 18 As shown, the mid-span area of ​​the lower beam (positive bending moment area) has one lower beam pre-cast segment 540, and the root area of ​​the lower beam (negative bending moment area) has two lower beam pre-cast segments 540; when pouring the joint concrete, since only one pouring is required, the first segment combination 550 is the largest segment combination, and the first permanent prestressed beam 551 of the first segment combination 550 is also the second permanent prestressed beam 552 of the largest segment combination.

[0095] In a preferred example, the lower cross beam 50 has five sections, such as Figure 17 、 Figure 19As described, the lower cross beam mid-span area (positive bending moment area) has three lower cross beam pre-cast segments 540, and the lower cross beam root area (negative bending moment area) has two lower cross beam pre-cast segments 540; when pouring joint concrete, first pour the two joints of the three lower cross beam pre-cast segments 540 in the mid-span area, and at the same time tension and anchor the first permanent prestressed beam 551 to the middle-length prestressed pipe of the first segment combination 550; then pour the joints of the lower cross beam pre-cast segments 540 between the mid-span area and the root area, tension and anchor the second permanent prestressed beam 552 that passes through the five lower cross beam pre-cast segments 540, and obtain the maximum segment combination. Figure 19 In the embodiment, each time the first permanent prestressed tendon 551 and the second permanent prestressed tendon 552 are tensioned, tension is applied to both the upper and lower edges of the segment assembly.

[0096] In another example, Figure 20 As shown, the lower cross beam 50 has 7 segments; when pouring the joint concrete, first pour the two joints of the three lower cross beam precast segments 540 in the mid-span area, and at the same time tension and anchor the first permanent prestressed tendon 551 to the mid-length prestressed pipe of the first segment combination 550; then pour the joints between adjacent lower cross beam precast segments 540, tensioning the first permanent prestressed tendon 551; finally pour the lower cross beam precast segment 540 at the root of the lower cross beam, and tension the second permanent prestressed tendon 552. In another example, as Figure 21 As shown, the lower cross beam 50 has 9 segments. Assuming that the mid-span area of ​​the lower cross beam (positive bending moment area) has five lower cross beam pre-cast segments 540, and the root area of ​​the lower cross beam (negative bending moment area) has four lower cross beam pre-cast segments 540; when pouring the joint concrete, first pour the two joints of the three lower cross beam pre-cast segments 540 in the mid-span area, and then pour the joints between adjacent lower cross beam pre-cast segments 540 section by section. In this process, the first segment combination is 3 segments, 5 segments, and 7 segments respectively, and the first permanent prestressed tendon 551 is tensioned 3 times in total; finally, the joint concrete between all the lower cross beam pre-cast segments is poured, and the second permanent prestressed tendons 552 are tensioned at the upper and lower edges to obtain the maximum segment combination.

[0097] As a preferred embodiment, the step S53 further includes the following steps:

[0098] Cast the beam-column joint 620 between the lower crossbeam 50 and the tower column; ultra-high performance concrete 630 (UHPC) or fiber reinforced concrete is cast within a thickness range of 10 to 20 cm at the upper edge of the beam-column joint 620. In this embodiment, a casting material with excellent crack resistance is used in the beam-column joint 620 between the lower crossbeam 50 and the tower column, that is, in a certain range of the top plate corresponding to the negative bending moment area at both ends of the lower crossbeam 50. UHPC or fiber reinforced concrete with excellent crack resistance is used instead of shrinkage-compensating concrete to resist tensile stress that may occur during operation, thereby enhancing the crack resistance of the lower crossbeam 50, and waiting for strong post-tensioning of the full-length prestressed tendons 510. Figure 12 Ultra-high performance concrete 630 is schematically depicted in FIG.

[0099] As a preferred embodiment, the beam-column joint 620 adopts a tongue-and-groove joint or a serrated joint, which increases the bite force and bonding force between the precast concrete and the post-poured joint, improves the reliability of the joint connection of the lower crossbeam 50, and further enhances the crack resistance of the lower crossbeam 50.

[0100] As a preferred embodiment, in step S5, the steps of proportionally extending the first temporary prestressed bundle 330 and the second temporary prestressed bundle 340 are as follows:

[0101] The full-length prestressed tendons 510 are tensioned in batches, and the first temporary prestressed tendons 330 and / or the second temporary prestressed tendons 340 are tensioned in equal proportions at the same time; wherein, when the full-length prestressed tendons 510 of the i-th batch are tensioned, the first temporary prestressed tendons 330 and / or the second temporary prestressed tendons 340 corresponding to the i-th batch are tensioned, and the full-length prestressed tendons 510 tensioned in the i-th batch account for 15% to 35% of all the full-length prestressed tendons 510; the proportion of the first temporary prestressed tendons 330 and / or the second temporary prestressed tendons 340 tensioned in the i-th batch to all the temporary prestressed tendons is denoted as a first proportion, and the proportion of the full-length prestressed tendons 510 tensioned in the i-th batch to all the full-length prestressed tendons 510 is denoted as a second proportion, and the difference between the first proportion and the second proportion does not exceed 10%; i is a positive integer, 3≤i≤6;

[0102] It should be known to those skilled in the art that, during the upward construction of the tower column, as the weight of the tower column increases, the horizontal component force also gradually increases. Preferably, the second temporary prestressed tendons 340 are tensioned in batches as the tower column is constructed upward. For ease of construction, the tensioning can be carried out in 1 to 3 batches.

[0103] Before the joints between the precast segments 540 of the lower crossbeam are cast, the horizontal force component of the tower column is borne entirely by the temporary prestress (the first and second temporary prestressing tendons 330 and 340) within the cap 30. By tensioning the full-length prestressing tendons 510 in batches and then releasing the first and second temporary prestressing tendons 330 and 340 within the cap 30, the horizontal force component of the tower column can be gradually transferred from the cap 30 to the lower crossbeam 50. If the full-length prestressing tendons 510 are tensioned in one step before all the temporary prestressing tendons within the cap 30 are released, the structural system will experience a sudden change in stress. When the temporary prestressing tendons within the cap 30 are released, the axial prestressing force on the lower crossbeam 50 will be significantly reduced. To ensure permanent prestressing force, the full-length prestressing tendons 510 must be over-tensioned, which will risk excessive compressive failure of the concrete in the lower crossbeam 50. Over-tensioning may also require the deployment of additional steel tendons, which is not conducive to prestressing tendon conservation.

[0104] As a preferred embodiment, the first temporary prestressed bundles 330 and the second temporary prestressed bundles 340 are evenly spaced vertically; in step S2, the tensioned first temporary prestressed bundles 330 account for 20% to 40% of the total number of temporary prestressed bundles.

[0105] As a preferred embodiment, in step S4, the horizontal component of the lower tower column 40 is calculated according to the horizontal cross brace 610, and the second temporary prestressed beam 340 is tensioned in batches or all at once according to the horizontal component of the lower tower column 40; usually, the function of the horizontal cross brace 610 is to resist the bending moment of the tilted tower column to overturn inward, so that the tower column load is transmitted as much as possible along the axial direction of the tower column, that is, it is approximately assumed that the bottom of the tower column only bears the axial force along the direction of the tower column, and the horizontal component of the tower column can be calculated by the geometric relationship; that is, when the axial force of the tower column is P, when the tower column is tilted inward at an angle α, the horizontal component is P*sinα, and when the horizontal component reaches more than 80% of the design value of the first temporary prestressed beam 330, consider tensioning the first batch of second temporary prestressed beams 340, and when the P value continues to increase and reaches 80% of the stretched temporary prestressed beam again, tension a new batch of second temporary prestressed beams 340, and so on;

[0106] By adopting this embodiment, the tensioning timing and tensioning batches can be quickly determined, thereby improving construction efficiency and reducing the secondary internal forces of the structure (such as pile foundation shear force, etc.) caused by temporary prestressing while ensuring the safety and reliability of the structure.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A construction method for a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam, characterized in that: Including steps: S1: Construction of bridge pile foundation and cap steel box cofferdam; S2: tying the cap steel mesh, pre-embedding multiple layers of transverse prestressed pipes spaced apart vertically in the cap steel mesh, each layer of the transverse prestressed pipes comprising multiple transverse prestressed pipes spaced apart longitudinally; fixing a plurality of fillers for forming vertical through-slots at the centerline of the cap wide side; pouring the cap concrete, and tensioning and anchoring the first temporary prestressed tendons to some of the transverse prestressed pipes; S3: Tie the tower column steel mesh to the height of the bottom edge of the lower crossbeam and pour concrete; cast the lower crossbeam in sections to obtain several pre-cast sections. Each pre-cast section contains several long prestressed pipes. The long prestressed pipes of two adjacent pre-cast sections are connected in the transverse direction. These long prestressed pipes form the first full-length prestressed pipe. S4: Continue constructing the tower column in sections, and pre-embed a second full-length prestressed pipe in the tower column steel mesh, which corresponds to and connects with the first full-length prestressed pipe; the outer end of the second full-length prestressed pipe extends outward to the outside of the middle tower column; Continue to construct the tower columns, middle beams, and horizontal cross braces. When constructing the horizontal cross braces, tension and anchor the second temporary prestressed tendon into the remaining transverse prestressed pipes in the cap to resist the horizontal component of the lower tower column. S5: sequentially pouring concrete at the joints between the first-cast segments of the lower crossbeam, and tensioning the full-length prestressed tendons. The full-length prestressed tendons pass through the first full-length prestressed pipe and the second full-length prestressed pipe. Both ends of the full-length prestressed tendons are anchored to the outside of the middle tower column. After all the full-length prestressed tendons are tensioned, grouting is promptly performed to seal the first full-length prestressed pipe, the second full-length prestressed pipe, and the corresponding anchor heads. While the full-length prestressed tendons are being tensioned, the first and second temporary prestressed tendons are being released in equal proportion and removed, and the transverse prestressed pipes are being sealed by grouting. S6: Remove the steel casing cofferdam of the foundation and continue to construct the remaining cable tower structure to complete the cable tower construction.

2. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 1, characterized in that: The specific steps of constructing the first cast section of the lower beam in step S3 include: S31: erecting a lower crossbeam support on the top of the platform, and performing overload preloading on the lower crossbeam support; S32: Erecting the inner and outer formwork of the lower cross beam in sections along the transverse direction of the bridge, tying the steel mesh of the lower cross beam of each section, and pre-embedding the long and short prestressed pipes of each section, and then pouring concrete to obtain a plurality of lower cross beam precast sections arranged at intervals along the transverse direction of the bridge; According to the overall stress state of the lower cross beam, the first cast section of the lower cross beam is divided into the first cast section of the lower cross beam in the positive bending moment area and the first cast section of the lower cross beam in the negative bending moment area; the long prestressed pipe is configured according to the overall stress state of the lower cross beam; the short prestressed pipe of the first cast section of the lower cross beam in the positive bending moment area is arranged in the bottom plate, and the lower segment prestressed tendons are tensioned therein when the first cast section of the lower cross beam is prefabricated; the short prestressed pipe of the first cast section of the lower cross beam in the negative bending moment area is arranged in the top plate, and the upper segment prestressed tendons are tensioned therein when the first cast section of the lower cross beam is prefabricated.

3. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 2, characterized in that: The number of the first cast sections of the lower crossbeam is an odd number, and a medium-length prestressed pipe is pre-buried in the first cast sections of the lower crossbeam. In step S5, when pouring the joint concrete between the first cast sections of the lower crossbeam, the following steps are also included: S51: First, cast the joint concrete between the three precast segments of the lower cross beam located in the mid-span area of ​​the lower cross beam to form a first segment combination; after the joint concrete of the first segment combination reaches a certain strength, tension and anchor the first permanent prestressed tendon in the mid-length prestressed pipe of the first segment combination; the first permanent prestressed tendon runs through the entire first segment combination; S52: Continue pouring the joint concrete between the first segment combination and the adjacent lower beam precast segment to form a second segment combination; adjust the second segment combination to the corresponding first segment combination; tension and anchor a first permanent prestressed tendon in the mid-length prestressed conduit of the first segment combination; the first permanent prestressed tendon runs through the entire first segment combination; S53: Repeat step S52 until the joint concrete between all the lower beam precast segments is poured, tension and anchor the second permanent prestressed tendons that pass through all the lower beam precast segments to obtain the maximum segment combination.

4. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 3 is characterized in that: The first permanent prestressed tendon and the second permanent prestressed tendon are arranged at the upper edge, lower edge or both upper and lower edges of the lower beam segment combination; the first segment combination can be less or not equipped with the first permanent prestressed tendon at the upper edge, and the largest segment combination can be less or not equipped with the second permanent prestressed tendon at the lower edge.

5. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 3, characterized in that: The step S53 further includes the following steps: The beam-column joint between the lower cross beam and the tower column is cast; the upper edge of the beam-column joint is cast in a thickness range of 10 to 20 cm using ultra-high performance concrete or fiber concrete.

6. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 1, characterized in that: In step S5, the steps of proportionally extending the first temporary prestressed tendons and the second temporary prestressed tendons are as follows: The full-length prestressed beams are tensioned in batches, and the first temporary prestressed beams and / or the second temporary prestressed beams are tensioned in equal proportions at the same time; wherein, when tensioning the full-length prestressed beams of the i-th batch, the first temporary prestressed beams and / or the second temporary prestressed beams of the i-th batch are tensioned, and the full-length prestressed beams tensioned in the i-th batch account for 15% to 35% of all the full-length prestressed beams; the proportion of the first temporary prestressed beams and / or the second temporary prestressed beams tensioned in the i-th batch to all the temporary prestressed beams is denoted as the first proportion, and the proportion of the full-length prestressed beams tensioned in the i-th batch to all the full-length prestressed beams is denoted as the second proportion, then the difference between the first proportion and the second proportion does not exceed 10%; i is a positive integer, 3≤i≤6.

7. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 1, characterized in that: The number of transverse prestressed pipe layers in the pedestal is 2 to 5, the uppermost layer of the transverse prestressed pipe layer is not less than 50 cm from the top surface of the pedestal, and the lowermost layer of the transverse prestressed pipe layer is not less than 100 cm from the bottom surface of the pedestal.

8. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 1, characterized in that: The first temporary prestressed tendons and the second temporary prestressed tendons are evenly spaced vertically. In step S2, the tensioned first temporary prestressed tendons account for 20% to 40% of the total number of temporary prestressed tendons.

9. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 1, characterized in that: In step S4, the horizontal component of the lower tower column is calculated according to the horizontal cross brace, and the second temporary prestressed beam is tensioned in batches or all at once according to the horizontal component of the lower tower column; when tensioning in batches, the first batch of second temporary prestressed beams is tensioned when the horizontal component of the tower column reaches more than 80% of the design value of the first temporary prestressed beam; when the horizontal component of the tower column reaches 80% of the tensioned temporary prestressed beam again, a new batch of second temporary prestressed beams is tensioned, and this cycle is repeated.

10. The construction method of a cable-stayed bridge tower for improving the crack resistance of the lower crossbeam according to claim 1, characterized in that: The vertical through seam is disconnected along the longitudinal bridge direction of the pedestal. The width of the vertical through seam is 1 to 5 cm. The filling body is made of elastic material.

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