Composite beam cable-stayed bridge construction method

Abstract

The invention relates to the technical field of bridges, and provides a composite beam cable-stayed bridge construction method, which comprises the following steps of: initially tensioning each stay cable to a corresponding cable force target value, enabling the line shape of a main beam positioned in a sagging moment area to be in an upward convex state, mounting a bridge deck in the sagging moment area, and overlapping a bridge deck wet joint, so that the bridge deck can be connected with the main beam under the self-weight action of the bridge deck and the bridge deck wet joint. The steel main beam moves downwards for the first time, the bridge deck generates pressure stress, the cable force of the stay cables in the area where the bridge deck wet joints are overlapped is released in sequence, so that the steel main beam moves downwards again, the bridge deck generates pressure stress increment, the bridge deck is installed in the hogging moment area, the bridge deck wet joints are overlapped, and the bridge deck prestressed steel beams in the hogging moment area are tensioned. And then bridge deck pavement and ancillary facilities are constructed. Pressure stress reserve of the bridge deck in incremental launching construction can be guaranteed, meanwhile, a large number of prestressed corrugated pipes and steel beams do not need to be arranged in the bridge deck in the sagging moment area, and the problem that steel box girders are difficult to apply to mountainous areas or unnavigable water areas can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridges, and in particular to a construction method for a composite beam cable-stayed bridge. Background Art

[0002] Composite-beam cable-stayed bridges have become one of the main bridge types designed in recent years because they fully utilize the compressive strength of the concrete bridge deck and the tensile strength of the steel structure. To facilitate the hoisting and installation of the steel main beam, conventional composite-beam cable-stayed bridges use I-beams or double-sided box beams that can be assembled on-site in bulk. Composite-beam cable-stayed bridges with steel box beams are relatively rare. Compared to I-beams and double-sided box beams, steel box beams offer more significant advantages in wind stability and torsional resistance. However, due to their relatively large weight and the fact that they are disassembled in the factory and then assembled on-site, conventional slewing cranes are unable to lift their weight in mountainous areas or non-navigable waters where heavy cranes cannot be used.

[0003] In order to solve the above-mentioned problem that it is impossible to use a crane to lift and install, when there is space for assembly at the bridge head, the main beam is constructed by the top-pushing method. The conventional process mainly includes two types: assembling steel main beams → pushing steel main beams into place → installing and tensioning inclined cables → installing bridge decks → overlapping wet joints → tensioning bridge deck prestressing (process one); assembling steel main beams → installing bridge decks → overlapping wet joints → tensioning bridge deck prestressing → pushing composite beams into place → installing and tensioning inclined cables (process two). The above two methods are different from the cantilever construction method: installing steel main beams → initially tensioning inclined cables → installing bridge decks → Compared with overlapping wet joints → two inclined cables (process three), process three will increase the compressive stress reserve of the bridge deck when the inclined cables are used. When processes one and two are used, the tensioning of the inclined cables cannot provide compressive stress reserve for the bridge deck. In fact, tensioning the inclined cables in process two will even cause tensile stress in the bridge deck. In order to ensure the compressive stress reserve of the bridge deck during the operation stage, the compressive stress reserve of the bridge deck needs to be provided by installing and tensioning more prestressed steel strands in the bridge deck. A large number of prestressed corrugated tubes will not only weaken the integrity of the cross-section, but also make the construction process of the prestressed tensioning condition complicated, the construction period is long, and the cost is high.

[0004] In view of this, it is necessary to propose a construction method for a composite beam cable-stayed bridge to solve or at least alleviate the above defects. Summary of the Invention

[0005] The main purpose of the present invention is to provide a construction method for a composite beam cable-stayed bridge, so as to solve the problem in the prior art that the composite beam cable-stayed bridge adopts jacking construction and requires the installation and tensioning of a large number of prestressed steel strands in the bridge deck, resulting in poor integrity of the bridge deck, long construction process period and high cost.

[0006] To achieve the above object, the present invention provides a construction method for a composite beam cable-stayed bridge, comprising the following steps: S1: Construction of cable towers, installation of transition piers, temporary assembly of brackets at the bridge head and temporary support piers at the bridge site; S2: Assemble steel main beams in batches according to the manufacturing line shape, install front guide beams, rear guide beams and jacking equipment; S3: Use jacking equipment to push the steel main beams into place in batches and then lower them. Remove the front guide beam, rear guide beam, temporary assembly brackets at the bridge head, and jacking equipment. S4: Initially tension each stay cable to the corresponding target cable force value, so that the main beam line shape in the positive bending moment area is in an upward convex state, and then remove the temporary support piers at the bridge site; S5, install the bridge deck in the positive bending moment area and overlap the bridge deck wet joints so that under the deadweight of the bridge deck and the bridge deck wet joints, the steel main beam moves downward for the first time and the bridge deck generates compressive stress. ; S6: Release the cable forces in the wet joints of the overlapped bridge deck in sequence, so that the steel main beam moves downward again, and the bridge deck generates an incremental compressive stress. ; S7, install the bridge deck in the negative bending moment area, overlap the bridge deck wet joints, tension the bridge deck prestressed steel tendons in the negative bending moment area, and then construct the bridge deck pavement and ancillary facilities.

[0007] Preferably, the target value of the cable force in step S4 is obtained by the following steps: S41, without considering prestressing measures, calculate the tensile stress distribution data of the bridge deck during the completion stage and operation state, and compare it with the requirements of the specification to obtain the target compressive stress value required for the bridge deck in the entire bridge area to meet the stress requirements of the specification. ; S42, according to the compressive stress target value With the compressive stress The difference between the two is used to obtain the incremental compressive stress required to increase the tension of the cable. ; S43, calculate the effect matrix of the release of the stay cables on the increase in compressive stress in the bridge deck; S44, according to the compressive stress increment and the influence matrix, to obtain the cable force increment required in the initial tensioning stage; S45: Determine a target cable force value corresponding to each stay cable in the initial tensioning stage according to the cable force increment.

[0008] Preferably, step S5 specifically includes the following steps: Obtain the maximum positive bending moment position in the positive bending moment zone, hoist the bridge deck in sections and blocks from the maximum positive bending moment position to the transition pier, and overlap the bridge deck wet joints, then hoist the bridge deck in sections and blocks from the maximum positive bending moment position to the cable tower, and overlap the bridge deck wet joints, so that under the deadweight of the bridge deck and the bridge deck wet joints, the steel main beam moves downward for the first time, and the bridge deck generates compressive stress .

[0009] Preferably, the step S45 further includes the following steps: S451, when the middle span and side span are asymmetric and both are steel-concrete composite beams, obtain the The tower deflection and the change in the tower root compressive stress after the cable is initially stretched to the corresponding target cable force value; is a positive integer, The starting value of is 1; S452, determining whether the tower deviation value is less than a first preset threshold, and determining whether the tower root compressive stress variation is less than a second preset threshold; S453: When both the tower deviation value is less than the first preset threshold and the tower root compressive stress variation is less than the second preset threshold, it is determined that The stay cable is in a safe state after being initially stretched to the corresponding cable force target value; S454, will +1 assigned to , and repeat steps S451 to S453 until all the stay cables are verified.

[0010] Preferably, the step S45 further includes the following steps: S4501, when the middle span and side span are asymmetric, and the middle span is a steel-concrete composite beam and the side span is a concrete main beam, obtain the The tower deflection value of the cable tower after the cable is initially stretched to the corresponding cable force target value, the change in the tower root compressive stress, and the tensile stress of the side span concrete main beam; is a positive integer, The starting value of is 1; S4502, determining whether the tower deflection value is less than a first preset threshold, determining whether the tower root compressive stress variation is less than a second preset threshold, and determining whether the tensile stress of the side span concrete main beam is less than a third preset threshold; S4503: When the tower deflection value is less than the first preset threshold, the tower root compressive stress variation is less than the second preset threshold, and the side span concrete main beam tensile stress is less than the third preset threshold, the first step is determined. The stay cable is in a safe state after being initially stretched to the corresponding cable force target value; S4504, will +1 assigned to , and repeat steps S4501 to S4503 until all the stay cables are verified.

[0011] Preferably, the second preset threshold is obtained by the following steps: Obtain the compressive stress reserve at the base of the tower under the action of its own weight , and obtain the control threshold of the compressive stress at the tower root ; Determine the compressive stress reserve and the compressive stress specification control threshold and taking the compressive stress difference between them as the second preset threshold.

[0012] Preferably, the first preset threshold is obtained by the following steps: Obtain the compressive stress at the tower root, and make sure that the compressive stress at the tower root is equal to the compressive stress code control threshold. When the tower deflection value of the cable tower is determined , and the tower bias as the first preset threshold.

[0013] Preferably, the step S453 further includes the following steps: When at least one of the following conditions is not met: the tower deviation value is less than the first preset threshold value, and the tower root compressive stress variation is less than the second preset threshold value, it is determined that the first The cable is in an unsafe state after it is initially stretched to the corresponding target cable force value; The cable tension on the offset side of the tower is reduced, or a construction weight is applied on the other side of the tower offset, or the cable tension on the other side of the tower offset is increased, until both of the tower offset value being less than a first preset threshold and the tower root compressive stress change being less than a second preset threshold are satisfied, and then the process proceeds to step S454.

[0014] Preferably, the step S4502 further includes the following steps: When at least one of the following conditions is not satisfied: the tower deflection is less than a first preset threshold, the change in the tower root compressive stress is less than a second preset threshold, and the tensile stress of the side span concrete main beam is less than a third preset threshold, the cable tension on the deflected side of the tower is reduced, or construction weight is applied on the other side of the tower deflection, or the cable tension on the other side of the tower deflection is increased, until all three conditions are satisfied: the tower deflection is less than the first preset threshold, the change in the tower root compressive stress is less than the second preset threshold, and the tensile stress of the side span concrete main beam is less than the third preset threshold, and then step S4503 is entered.

[0015] Preferably, shear nails are provided on the top surface of the steel main beam of the bridge deck wet joint.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This application can ensure the compressive stress reserve of the bridge deck during the operation phase when the composite beam cable-stayed bridge adopts the jacking construction. At the same time, it is not necessary to install a large number of prestressed corrugated tubes and steel strands in the bridge deck in the positive bending moment area. The bridge deck has good integrity and can also solve the problem that steel box girders are difficult to use in mountainous areas or non-navigable waters. The details are as follows: (1) The bridge deck in the positive bending moment zone of the present application does not need to be provided with a large number of prestressed corrugated tubes and steel bundles, which can save the time for threading, tensioning and grouting of prestressed steel bundles, and save the cost of equipment and materials related to tensioning of prestressed steel bundles. At the same time, there are no prestressed corrugated tubes in the bridge deck, and the integrity of the bridge deck is better, thereby achieving the purpose of improving construction efficiency, reducing construction costs and ensuring construction quality; (2) This application makes full use of the deformation characteristics of the cable-stayed bridge and the stress characteristics of the steel main beam, inclined cable and concrete bridge deck. During the construction process, due to the relatively small constant load of the cable-stayed bridge, the stress amplitude of the inclined cable and the steel main beam is relatively small when the bridge deck is not paved and the second phase constant load is applied. The initial tension is appropriately increased. After the subsequent installation of the bridge deck and the superposition of the wet joints, the over-tensioned cable force is released. The stress of the steel main beam and inclined cable can also be within the specification range. The stress performance of steel and concrete materials is fully utilized, and the efficiency of material use during the construction process is improved. By adjusting the process, compressive stress is generated in the bridge deck. The construction method has clear process and simple operation. (3) This application can realize the use of scenarios such as steel box composite beams, which greatly reduces the transportation requirements in mountainous areas or navigable areas. This application can also be applied to composite beam cable-stayed bridges of various cross-sections. This application solves the problem of compressive stress reserve of the bridge deck during the jacking construction of composite beam cable-stayed bridges, which is conducive to the application of the jacking construction method in the construction of composite beam cable-stayed bridges. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of a construction method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure after construction step S1 in one embodiment of the present invention; Figure 3This is a schematic diagram of the structure after construction step S2 in one embodiment of the present invention; Figure 4 This is a schematic diagram of the structure after construction step S3 in one embodiment of the present invention; Figure 5 This is a schematic diagram of the structure after construction step S4 in one embodiment of the present invention; Figure 6 This is a schematic diagram of the structure after construction step S5 in one embodiment of the present invention; Figure 7 This is a schematic diagram of the structure after construction step S6 in one embodiment of the present invention; Figure 8 Schematic diagram of the structure after construction step S7 in one embodiment of the present invention.

[0019] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments.

[0020] Description of Figure Numbers: 11. Cable tower; 12. Transition pier; 13. Temporary assembly bracket at the bridge head; 14. Temporary support pier at the bridge site; 15. Steel main beam; 16. Front guide beam; 17. Rear guide beam; 18. Stay cable; 19. Bridge deck. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] In the present invention, the descriptions of "first," "second," etc. are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions of the various embodiments may be combined with each other, but this must be based on the fact that they can be implemented by a person of ordinary skill in the art. If the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0024] Please see the attached Figures 1 to 8 In one embodiment of the present invention, a construction method for a composite beam cable-stayed bridge includes the following steps: S1: Construct the cable towers 11, install the transition piers 12, the temporary bridgehead support 13, and the temporary support piers 14. Specifically, the foundation of the temporary bridgehead support 13 can be reinforced to ensure that the foundation settlement meets the regulatory requirements under the load of the steel main beam 15. The temporary bridgehead support 13 can be made of steel pipe supports, and the top elevation of the temporary bridgehead support 13 can be positioned according to the assembly line of the steel main beam 15 to reduce the amount of elevation adjustment during the assembly of the steel main beam 15.

[0025] S2: Assemble the steel main beams 15 in batches according to the manufacturing alignment, install the leading guide beams 16, trailing guide beams 17, and jacking equipment. In a preferred embodiment, the first batch of jacking steel main beams 15 are assembled on the temporary assembly brackets 13 at the bridge head according to the manufacturing alignment of the steel main beams 15, and the alignment is monitored and adjusted. The manufacturing alignment is the stress-free manufacturing alignment of the steel main beams 15, calculated through finite element analysis according to the construction process. The stress-free manufacturing alignment equals the design elevation + the pre-camber of the construction + the pre-camber of the completed bridge. During assembly, the steel main beams 15 can be connected by welding or bolts. The leading guide beams 16, trailing guide beams 17, and jacking equipment (not shown) required for jacking are installed. The operating platform, tank wheels, or Teflon slides required for jacking are installed on top of the transition piers 12 and the temporary support piers 14 at the bridge site. This is conventional technical content of jacking construction and will not be detailed here.

[0026] S3: Use jacking equipment to jack the steel main beams 15 into place and lower them in batches, and remove the front guide beam 16, rear guide beam 17, temporary assembly bracket 13 at the bridge head, and jacking equipment. As a preferred embodiment, after jacking each batch of steel main beams 15, the assembly elevation of each batch of steel main beams 15 in the subsequent stage needs to be adjusted based on the elevation of the previous batch of steel main beams 15. During the jacking process, the displacement and stress of the cantilever front end of the steel main beam 15 should be monitored to ensure that the axis deviation of the steel main beam 15 does not exceed ±20mm during the jacking process. If it exceeds, the deviation should be corrected by adjusting the jacking force on the left and right sides of the steel main beam 15. At the same time, the stress of the steel main beam 15 should be ensured not to exceed the specification limit. After the steel main beam 15 is jacked into place, permanent supports are installed at the cable tower 11 and transition pier 12. The steel main beam 15 is lowered using a jack, and the front guide beam 16, rear guide beam 17, temporary assembly bracket 13 at the bridge head, and jacking equipment are removed. The front guide beam 16 and the rear guide beam 17 are used to shorten the cantilever length of the steel main beam 15 and reduce the stress of the steel main beam 15 during the jacking process.

[0027] S4, initially tensioning each stay cable 18 to the corresponding target cable force value, so that the main beam line shape in the positive bending moment area is in an upward convex state, and then dismantling the temporary support pier 14 at the bridge position.

[0028] S5, install the bridge deck 19 in the positive bending moment area, overlap the bridge deck wet joint, so that under the dead weight of the bridge deck 19 and the bridge deck wet joint, the steel main beam 15 moves downward for the first time, and the bridge deck 19 generates compressive stress Under the deadweight of the bridge deck 19 and the bridge deck wet joint, the steel main beam 15 in the convex state begins to move downward toward the design line, compressing the concrete bridge deck 19 on top, causing the bridge deck 19 to generate compressive stress in the positive bending moment area. .

[0029] S6, sequentially release the cable forces 18 in the wet joints of the overlapped bridge deck, so that the steel main beam 15 moves downward again, and the bridge deck 19 generates an incremental compressive stress. The release of cable force reduces the upward pulling force of the cable 18 on the steel main beam 15, causing the steel main beam 15 to move further downward. The second downward displacement will further compress the concrete bridge deck 19 in the positive bending moment area, causing it to be under compressive stress. Add the compressive stress increment on the basis .

[0030] S7, install the bridge deck 19 in the negative bending moment area, overlap the bridge deck wet joints, tension the prestressed steel tendons of the bridge deck 19 in the negative bending moment area, and then construct the bridge deck pavement and ancillary facilities. After the bridge deck 19 in the positive bending moment area is overlapped and the cable 18 tension is released, the steel main beam 15 returns to the design linear control range, such as Figure 8 As shown, the bridge deck 19 in the negative bending moment area is installed, and the wet joints of the bridge deck are overlapped. Since the negative bending moment area is overlapped last, the negative bending moment area does not generate negative bending moment due to the construction of the bridge deck 19 in the positive bending moment area and the release of the cable force of the inclined cable 18. The prestressed steel strands of the bridge deck 19 in the negative bending moment area are tensioned, and then the bridge deck pavement and ancillary facilities are constructed. The bridge is opened to traffic after passing the acceptance inspection.

[0031] This application scheme has the following advantages: (1) There is no need to install a large number of prestressed corrugated pipes and steel bundles in the bridge deck 19 in the positive bending moment area, which can save the time for prestressed steel bundle threading, tensioning and grouting maintenance, and save the equipment and material costs related to prestressed steel bundle tensioning. At the same time, there are no prestressed corrugated pipes in the bridge deck 19, and the integrity of the bridge deck 19 is better, achieving the purpose of improving construction efficiency, reducing construction costs and ensuring construction quality; (2) This application makes full use of the deformation characteristics of the cable-stayed bridge and the stress characteristics of the steel main beam 15, the inclined cable 18 and the concrete bridge deck 19. During the construction process, since the cable-stayed bridge has a relatively small constant load, in the absence of paving the bridge deck and the second-phase constant load, the stress amplitude of the inclined cable 18 and the steel main beam 15 is relatively small. The initial tension is appropriately increased. After the subsequent installation and superposition of the bridge deck 19, the over-tensioned cable force is released. The stress of the steel main beam 15 and the inclined cable 18 can also be within the specification range, giving full play to the stress performance of steel and concrete materials, improving the efficiency of material use during the construction process, and generating compressive stress in the bridge deck 19 through adjustment of the process. The construction method has clear process and simple operation. (3) The application scheme of this application can improve the use scenarios of steel box composite beam sections, greatly reduce the transportation requirements in mountainous areas or navigable areas, and the method can also be applied to composite beam cable-stayed bridges of various sections. This application solves the problem of compressive stress reserve of the bridge deck 19 during the jacking construction of the composite beam cable-stayed bridge, which is conducive to the application of the jacking construction method in the construction of the composite beam cable-stayed bridge.

[0032] As a preferred embodiment, the cable force target value in step S4 is obtained by the following steps: S41, without considering prestressing measures, calculate the tensile stress distribution data of the bridge deck 19 in the bridge construction stage and in the operational state, and compare it with the specification requirements to obtain the target compressive stress value of the bridge deck 19 in the entire bridge area to meet the specification stress requirements. Specifically, without considering prestressing measures, the tensile stress distribution data of the bridge deck 19 in the completed stage and in the operational state are calculated according to the construction procedures S1 to S5, and compared with the specification requirements, the target compressive stress value required for the bridge deck 19 in the entire bridge area to meet the specification requirements is obtained. , compressive stress target value The compressive stress corresponding to the deck 19 of the entire bridge area is obtained. The compressive stress required to be applied to the entire deck 19 area (especially the positive bending moment area) is to ensure that the tensile stress of the deck 19 does not exceed the allowable value in the specification under the most unfavorable working conditions. The compressive stress target value is The target compressive stress value that needs to be reserved in advance to offset the tensile stress generated in future operations.

[0033] S42, according to the compressive stress target value With the compressive stress The difference between the two is used to obtain the incremental compressive stress required to be increased by tensioning the cable 18. ; Compressive stress increment The compressive stress generated by the self-weight deflection in step S5 It is not enough. In the subsequent step S6, during the release of the cable force of the stay cable 18, the additional compressive stress increment generated in the bridge deck 19 by the secondary deflection of the steel main beam 15 is required. The target value that needs to be achieved through active cable tension adjustment.

[0034] S43, calculating the influence matrix of the release of the stay cable 18 on the increase in the compressive stress of the bridge deck 19.

[0035] S44, according to the compressive stress increment The influence matrix can be used to obtain the cable force increment of the inclined cable 18 required in the initial tensioning stage. Specifically, the influence matrix can be obtained according to the construction process and the influence of the cable force release of each inclined cable 18 on the compressive stress change of the bridge deck 19. There are mature technical means for this part, which will not be described in detail here.

[0036] S45, determining the target cable force value corresponding to each cable 18 in the initial tensioning stage according to the cable force increment of the cable 18. As a preferred embodiment, without considering the overlap of the bridge deck 19 and the increase in the compressive stress of the bridge deck 19 by releasing the cable force of the cable 18, the target cable force value of the bridge deck 19 is obtained by tensioning the prestressed steel strands in the positive bending moment zone. , according to the process of tensioning the prestressed steel strands, the initial tensioning force of each inclined cable 18 is calculated. , and then according to the cable force increment of the inclined cable 18 obtained by the above calculation, the two are added together to obtain the cable force target value corresponding to each inclined cable 18 in the initial tensioning stage of this scheme.

[0037] The present embodiment uses mechanical analysis and reverse deduction to calculate the target cable force value, accurately ensuring the crack resistance and long-term durability of the bridge deck 19 after the bridge is completed.

[0038] As a preferred embodiment, step S5 specifically includes the following steps: Obtain the maximum positive bending moment position in the positive bending moment zone, hoist the bridge deck 19 from the maximum positive bending moment position to the transition pier 12 in sections and blocks, and overlap the bridge deck wet joints. Then, hoist the bridge deck 19 from the maximum positive bending moment position to the cable tower 11 in sections and blocks, and overlap the bridge deck wet joints. Under the deadweight of the bridge deck 19 and the bridge deck wet joints, the steel main beam 15 moves downward for the first time, and the bridge deck 19 generates compressive stress. .

[0039] As a better example, by hoisting the bridge deck 19 in sections and blocks and overlapping the bridge deck wet joints, it can be determined according to the span size of the bridge. It is recommended to overlap the bridge deck 19 of 2-4 sections of steel main beams 15.

[0040] As a preferred embodiment, the step S45 further includes the following steps: S451, when the middle span and side span are asymmetric and both are steel-concrete composite beams, obtain the The tower deflection of the tower 11 and the change in the tower root compressive stress of the tower 11 after the inclined cable 18 is initially stretched to the corresponding cable force target value; wherein, is a positive integer, The starting value of is 1; S452, determining whether the tower deviation value is less than a first preset threshold, and determining whether the tower root compressive stress variation is less than a second preset threshold; S453: When both the tower deviation value is less than the first preset threshold and the tower root compressive stress variation is less than the second preset threshold, it is determined that The stay cables 18 are in a safe state after being initially stretched to the corresponding cable force target value; S454, will +1 assigned to , and repeat steps S451 to S453 until all the stay cables 18 are verified.

[0041] It is worth noting that if the bridge has an asymmetric mid-span and side spans, and both the mid-span and side spans are steel-concrete composite beams, after the cable force of the inclined cable 18 increases in the initial tensioning stage, the stress of the steel main beam 15 should be ensured to be within the requirements of the specification. For asymmetric cable-stayed bridges, the tensioning of the initial cable force and the release of the inclined cable 18 should ensure that the stress of the concrete section at the root of the tower 11 is within the requirements of the specification when there is a certain tower deviation.

[0042] By +1 assigned to , tension and check the next stay cable 18, return to step S451, and One of the +1 stay cables 18 is tensioned to its target cable tension. The tower deflection and the change in compressive stress at the tower base are then measured and used to determine whether the tower is in a safe state. By controlling the incremental tower deflection caused by the tensioning of a single cable to not exceed a first preset threshold, excessive horizontal displacement of tower 11 due to asymmetric loading or excessive cable tension during construction is prevented, thereby avoiding the risk of tower instability, tilting, or even collapse. Furthermore, by controlling the incremental compressive stress at the tower base caused by the tensioning of a single cable to not exceed a second preset threshold, the concrete at the base of tower 11 is ensured to remain safely compressed, retaining sufficient strength reserves.

[0043] As another preferred embodiment, the step S45 further includes the following steps: S4501, when the middle span and side span are asymmetric, and the middle span is a steel-concrete composite beam and the side span is a concrete main beam, obtain the The tower deflection of the tower 11 after the inclined cable 18 is initially stretched to the corresponding cable force target value, the change in the tower root compressive stress of the tower 11, and the tensile stress of the side span concrete main beam; is a positive integer, The starting value of is 1; S4502, determining whether the tower deflection value is less than a first preset threshold, determining whether the tower root compressive stress variation is less than a second preset threshold, and determining whether the tensile stress of the side span concrete main beam is less than a third preset threshold; S4503: When the tower deflection value is less than the first preset threshold, the tower root compressive stress variation is less than the second preset threshold, and the side span concrete main beam tensile stress is less than the third preset threshold, the first step is determined. The stay cables 18 are in a safe state after being initially stretched to the corresponding cable force target value; S4504, will +1 assigned to , and repeat steps S4501 to S4503 until all the inclined cables 18 are verified.

[0044] It is worth noting that if the bridge is asymmetrical in the middle span and side span, and the middle span is a steel-concrete composite beam and the side span is a concrete main beam, after the cable force of the inclined cable 18 increases in the initial tensioning stage, the stress of the steel main beam 15 should be ensured to be within the range required by the specification. +1 assigned to , tension and check the next stay cable 18, return to step S4501, +1 inclined cable 18 is tensioned to its target cable force, and then the tower deflection, tower root compressive stress change, and concrete main beam tensile stress after tensioning are obtained to make a triple indicator judgment and determine whether it is in a safe state to ensure sufficient safety reserve.

[0045] Preferably, the second preset threshold is obtained by the following steps: Obtain the compressive stress reserve at the root of Tower 11 under the action of its own weight , and obtain the code control threshold of the compressive stress at the root of tower 11 ; Determine the compressive stress reserve and the compressive stress specification control threshold and taking the compressive stress difference between them as the second preset threshold.

[0046] Preferably, the first preset threshold is obtained by the following steps: Obtain the compressive stress at the root of tower 11, and make the compressive stress at the root of tower 11 equal to the compressive stress standard control threshold When the tower eccentricity of the tower 11 is determined , and the tower bias as the first preset threshold.

[0047] Furthermore, after step S453, the following steps are further included: When at least one of the following conditions is not met: the tower deviation value is less than the first preset threshold value, and the tower root compressive stress variation is less than the second preset threshold value, it is determined that the first The stay cable 18 is in an unsafe state after being initially stretched to the corresponding cable force target value; The cable tension of the inclined cable 18 on the offset side of the tower 11 is reduced, or a construction weight is applied on the other side of the offset of the tower 11, or the cable tension of the inclined cable 18 on the other side of the offset of the tower 11 is increased, until both of the tower offset value is less than a first preset threshold value and the tower root compressive stress change is less than a second preset threshold value are met, and then the process proceeds to step S454.

[0048] Specifically, when at least one of the tower deviation value is less than the first preset threshold value and the tower root compressive stress variation is less than the second preset threshold value is not true, it is determined that the first After the first stay cable 18 is stretched to the corresponding target cable force value, it is in an unsafe state. Immediate measures need to be taken and the next cable cannot be stretched directly. This embodiment provides three optional adjustment methods. The goal is to apply a force or moment opposite to the current adverse effect to balance it. Only when both the tower deviation and the tower root stress meet the safety threshold requirements, the first cable is determined to be unsafe. The unsafe state caused by the tensioning of 18 inclined cables has been adjusted to a safe state.

[0049] Furthermore, after step S4502, the following steps are further included: When at least one of the following conditions is not satisfied: the tower deflection is less than the first preset threshold, the change in the tower root compressive stress is less than the second preset threshold, and the tensile stress of the side span concrete main beam is less than the third preset threshold, the cable tension of the inclined cable 18 on the offset side of the tower 11 is reduced, or construction weight is applied on the other side of the deflection of the tower 11, or the cable tension of the inclined cable 18 on the other side of the deflection of the tower 11 is increased, until all three conditions are satisfied: the tower deflection is less than the first preset threshold, the change in the tower root compressive stress is less than the second preset threshold, and the tensile stress of the side span concrete main beam is less than the third preset threshold, and then step S4503 is entered.

[0050] Specifically, when at least one of the following conditions is not satisfied: the tower deflection value is less than a first preset threshold value, the tower root compressive stress variation is less than a second preset threshold value, and the side span concrete main beam tensile stress is less than a third preset threshold value, the first After the first stay cable 18 is stretched to the corresponding target cable force value, it is in an unsafe state. Immediate measures need to be taken and the next cable cannot be stretched directly. This embodiment provides three optional adjustment methods. The goal is to apply a force or moment opposite to the current adverse effect to balance it. Only when the three indicators of tower deviation, tower root stress, and side span concrete main beam tensile stress all meet the safety threshold requirements, the first cable is determined to be unsafe. The unsafe state caused by the tensioning of 18 inclined cables has been adjusted to a safe state.

[0051] Preferably, shear studs are provided on the top surface of the steel main beam 15 at the wet joint of the bridge deck. Furthermore, after the bridge deck 19 and the steel main beam 15 are connected to each other through the steel bars of the bridge deck 19, they are connected by cast-in-situ concrete at the wet joint, and shear studs are provided on the top surface of the steel main beam 15 at the wet joint.

[0052] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A construction method for a composite beam cable-stayed bridge, characterized in that: The following steps are involved: S1: Construction of cable towers, installation of transition piers, temporary assembly of brackets at the bridge head and temporary support piers at the bridge site; S2: Assemble steel main beams in batches according to the manufacturing line shape, install front guide beams, rear guide beams and jacking equipment; S3: Use jacking equipment to push the steel main beams into place in batches and then lower them. Remove the front guide beam, rear guide beam, temporary assembly brackets at the bridge head, and jacking equipment. S4: Initially tension each stay cable to the corresponding target cable force value, so that the main beam line shape in the positive bending moment area is in an upward convex state, and then remove the temporary support piers at the bridge site; S5, install the bridge deck in the positive bending moment area and overlap the bridge deck wet joints so that under the deadweight of the bridge deck and the bridge deck wet joints, the steel main beam moves downward for the first time and the bridge deck generates compressive stress. ; S6: Release the cable forces in the wet joints of the overlapped bridge deck in sequence, so that the steel main beam moves downward again, and the bridge deck generates an incremental compressive stress. ; S7, install the bridge deck in the negative bending moment area, overlap the bridge deck wet joints, tension the bridge deck prestressed steel tendons in the negative bending moment area, and then construct the bridge deck pavement and ancillary facilities.

2. The construction method of a composite beam cable-stayed bridge according to claim 1, characterized in that: The target value of the cable force in step S4 is obtained specifically by the following steps: S41, without considering prestressing measures, calculate the tensile stress distribution data of the bridge deck during the completion stage and operation state, and compare it with the requirements of the specification to obtain the target compressive stress value required for the bridge deck in the entire bridge area to meet the stress requirements of the specification. ; S42, according to the compressive stress target value With the compressive stress The difference between the two is used to obtain the incremental compressive stress required to increase the tension of the cable. ; S43, calculate the effect matrix of the release of the stay cables on the increase in compressive stress in the bridge deck; S44, according to the compressive stress increment and the influence matrix, to obtain the cable force increment required in the initial tensioning stage; S45: Determine a target cable force value corresponding to each stay cable in the initial tensioning stage according to the cable force increment.

3. The construction method of a composite beam cable-stayed bridge according to claim 2, characterized in that: The step S5 specifically includes the following steps: Obtain the maximum positive bending moment position in the positive bending moment zone, hoist the bridge deck in sections and blocks from the maximum positive bending moment position to the transition pier, and overlap the bridge deck wet joints, then hoist the bridge deck in sections and blocks from the maximum positive bending moment position to the cable tower, and overlap the bridge deck wet joints, so that under the deadweight of the bridge deck and the bridge deck wet joints, the steel main beam moves downward for the first time, and the bridge deck generates compressive stress .

4. The construction method of a composite beam cable-stayed bridge according to claim 2, characterized in that: After step S45, the following steps are also included: S451, when the middle span and side span are asymmetric and both are steel-concrete composite beams, obtain the The tower deflection and the change in the tower root compressive stress after the cable is initially stretched to the corresponding target cable force value; is a positive integer, The starting value of is 1; S452, determining whether the tower deviation value is less than a first preset threshold, and determining whether the tower root compressive stress variation is less than a second preset threshold; S453: When both the tower deviation value is less than the first preset threshold value and the tower root compressive stress variation is less than the second preset threshold value, it is determined that The stay cable is in a safe state after being initially stretched to the corresponding cable force target value; S454, will +1 assigned to , and repeat steps S451 to S453 until all the stay cables are verified.

5. The construction method of a composite beam cable-stayed bridge according to claim 2, characterized in that: After step S45, the following steps are also included: S4501, when the middle span and side span are asymmetric, and the middle span is a steel-concrete composite beam and the side span is a concrete main beam, obtain the The tower deflection value of the cable tower after the cable is initially stretched to the corresponding cable force target value, the change in the tower root compressive stress, and the tensile stress of the side span concrete main beam; is a positive integer, The starting value of is 1; S4502, determining whether the tower deflection value is less than a first preset threshold, determining whether the tower root compressive stress variation is less than a second preset threshold, and determining whether the tensile stress of the side span concrete main beam is less than a third preset threshold; S4503: When the tower deflection value is less than the first preset threshold, the tower root compressive stress variation is less than the second preset threshold, and the side span concrete main beam tensile stress is less than the third preset threshold, the first step is determined. The stay cable is in a safe state after being initially stretched to the corresponding cable force target value; S4504, will +1 assigned to , and repeat steps S4501 to S4503 until all the stay cables are verified.

6. The construction method of a composite beam cable-stayed bridge according to claim 4, characterized in that: The second preset threshold is obtained by the following steps: Obtain the compressive stress reserve at the base of the tower under the action of its own weight , and obtain the control threshold of the compressive stress at the tower root ; Determine the compressive stress reserve and the compressive stress specification control threshold and taking the compressive stress difference between them as the second preset threshold.

7. The construction method of a composite beam cable-stayed bridge according to claim 6, characterized in that: The first preset threshold is obtained by the following steps: Obtain the compressive stress at the tower root, and make sure that the compressive stress at the tower root is equal to the compressive stress code control threshold. When the tower deflection value of the cable tower is determined , and the tower bias as the first preset threshold.

8. The construction method of a composite beam cable-stayed bridge according to claim 4, characterized in that: After step S453, the following steps are also included: When at least one of the following conditions is not met: the tower deviation value is less than the first preset threshold value, and the tower root compressive stress variation is less than the second preset threshold value, it is determined that the first The cable is in an unsafe state after it is initially stretched to the corresponding target cable force value; The cable tension on the offset side of the tower is reduced, or a construction weight is applied on the other side of the tower offset, or the cable tension on the other side of the tower offset is increased, until both of the tower offset value being less than a first preset threshold and the tower root compressive stress change being less than a second preset threshold are satisfied, and then the process proceeds to step S454.

9. The construction method of a composite beam cable-stayed bridge according to claim 5, characterized in that: The step S4502 further includes the following steps: When at least one of the following conditions is not satisfied: the tower deflection is less than a first preset threshold, the change in the tower root compressive stress is less than a second preset threshold, and the tensile stress of the side span concrete main beam is less than a third preset threshold, the cable tension on the deflected side of the tower is reduced, or construction weight is applied on the other side of the tower deflection, or the cable tension on the other side of the tower deflection is increased, until all three conditions are satisfied: the tower deflection is less than the first preset threshold, the change in the tower root compressive stress is less than the second preset threshold, and the tensile stress of the side span concrete main beam is less than the third preset threshold, and then step S4503 is entered.

10. The construction method of a composite beam cable-stayed bridge according to claim 1, characterized in that: Shear nails are provided on the top surfaces of the steel main beams of the bridge deck wet joints.

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