A construction method for composite beam cable-stayed bridges

Abstract

This invention relates to the field of bridge technology and provides a construction method for a composite beam cable-stayed bridge. The method involves initially tensioning each stay cable to its corresponding target tension value, causing the main beam in the positive bending moment zone to be in an upward convex state. Bridge deck panels are then installed in the positive bending moment zone, and the wet joints of the deck panels are overlapped. Under the self-weight of the deck panels and their wet joints, the main steel beam initially displaces downward, generating compressive stress in the deck panels. The stay cable forces in the areas with overlapped wet joints are then released sequentially, causing the main steel beam to displace downward again, generating an increase in compressive stress in the deck panels. Bridge deck panels are then installed in the negative bending moment zone, and the wet joints are overlapped. The prestressed steel strands in the bridge deck panels in the negative bending moment zone are then tensioned, followed by the construction of the bridge deck paving and ancillary facilities. This method ensures compressive stress reserves in the bridge deck panels during the jacking construction process. Furthermore, it eliminates the need for a large number of prestressed corrugated pipes and steel strands in the bridge deck panels in the positive bending moment zone, and also solves the problem that steel box girders are difficult to apply in mountainous areas or non-navigable waterways.

Description

Technical Field

[0001] This invention relates to the field of bridge technology, and in particular to a construction method for a composite beam cable-stayed bridge. Background Technology

[0002] Composite girder cable-stayed bridges have become one of the main bridge types designed in recent years due to their full utilization of the compressive strength of concrete bridge decks and the tensile strength of steel structures. To facilitate the hoisting and installation of the steel main girder, conventional composite girder cable-stayed bridges typically use I-beams or double-sided box girders that can be assembled on-site. Composite girder cable-stayed bridges with steel box girders are relatively less common. Compared to I-beams and double-sided box girders, steel box girders offer significant advantages in wind resistance and torsional performance. However, due to their relatively large weight and the need for on-site assembly after factory disassembly, they are difficult to lift in mountainous areas or non-navigable waterways where heavy-duty cranes cannot be used. Ordinary rotary cranes are often insufficient to lift their weight.

[0003] To address the issue of not being able to use a crane for installation, and given the availability of assembly space at the bridgehead, the main girder was constructed using a jacking method. The conventional procedures mainly include two steps: 1) Assembling the steel main girder → jacking the steel main girder into position → installing and tensioning the stay cables → installing the bridge deck → overlapping wet joints → tensioning the bridge deck prestressing (Step 1); 2) Assembling the steel main girder → installing the bridge deck → overlapping wet joints → tensioning the bridge deck prestressing → jacking the composite girder into position → installing and tensioning the stay cables (Step 2). These two methods, along with the cantilever construction method (installing the steel main girder → initial tensioning of the stay cables → installing the bridge deck), are similar to the two methods mentioned above. Compared to the two-stayed cable section (process three), process three increases the compressive stress reserve of the bridge deck when tensioning the stayed cables. However, when using processes one and two, the tensioning of the stayed cables cannot provide compressive stress reserve for the bridge deck. In fact, process two may even cause tensile stress in the bridge deck when tensioning the stayed cables. To ensure the compressive stress reserve of the bridge deck during the operation phase, a large number of prestressed steel strands need to be installed and tensioned in the bridge deck. A large number of prestressed corrugated pipes will not only weaken the integrity of the cross section, but also make the construction process of prestressed tensioning complex, time-consuming, and costly.

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

[0005] The main objective of this invention is to provide a construction method for composite beam cable-stayed bridges, which solves the problems of poor overall integrity of the bridge deck, long construction period, and high cost caused by the need to install and tension a large number of prestressed steel strands in the bridge deck when using incremental launching construction for composite beam cable-stayed bridges.

[0006] To achieve the above objectives, the present invention provides a construction method for a composite beam cable-stayed bridge, comprising the following steps:

[0007] S1, Construction of cable towers, installation of transition piers, temporary assembly supports at bridgeheads, and temporary support piers at bridge sites;

[0008] S2 involves assembling the steel main beams in batches according to the manufacturing line, installing the front guide beam, rear guide beam, and jacking equipment;

[0009] S3: The steel main beams were pushed into place and lowered in batches using jacking equipment, and the front guide beam, rear guide beam, temporary assembly support at the bridgehead, and jacking equipment were dismantled.

[0010] S4, initially tension each stay cable to the corresponding target cable force value, so that the main beam alignment in the positive bending moment zone is in an upward convex state, and then remove the temporary support piers at the bridge site;

[0011] S5, the bridge deck is installed in the positive bending moment zone, and the wet joints of the bridge deck are overlapped. Under the self-weight of the bridge deck and the wet joints, the main steel beam undergoes its first downward displacement, and the bridge deck generates compressive stress. ;

[0012] S6, sequentially release the cable forces in the wet joint area of ​​the superimposed bridge deck, causing the main steel beam to shift downwards again, resulting in an increase in compressive stress in the bridge deck. ;

[0013] S7 involves installing the bridge deck in the negative bending moment zone, overlapping the wet joints of the bridge deck, tensioning the prestressed steel strands of the bridge deck in the negative bending moment zone, and then constructing the bridge deck paving and ancillary facilities.

[0014] Preferably, the target cable force value in step S4 is obtained through the following steps:

[0015] S41. Without considering prestressing measures, calculate the tensile stress distribution data of the bridge deck during the completed bridge stage and operation state, and compare it with the specifications to obtain the target value of compressive stress required to meet the stress requirements of the specifications for the entire bridge area. ;

[0016] S42, based on the target compressive stress value With the compressive stress The difference yields the increase in compressive stress that needs to be achieved through the release of the stay cables. ;

[0017] S43, calculate the influence matrix of releasing the stay cables on the increase of compressive stress in the bridge deck;

[0018] S44, according to the compressive stress increment Based on the influence matrix, the required cable force increment for the initial tensioning stage is obtained;

[0019] S45, determine the target cable force value for each cable during the initial tensioning stage based on the cable force increment.

[0020] Preferably, step S5 specifically includes the following steps:

[0021] The location of the maximum positive bending moment in the positive bending moment zone is determined. From this location, the bridge deck panels and composite bridge deck wet joints are hoisted in segments towards the transition pier. Then, from the same location, the bridge deck panels and composite bridge deck wet joints are hoisted again in segments towards the tower. Under the self-weight of the bridge deck panels and their wet joints, the main steel beam undergoes its first downward displacement, generating compressive stress in the bridge deck panels. .

[0022] Preferably, the step S45 is followed by the following step:

[0023] S451, when the middle span and side spans are asymmetrical, and both the middle span and side spans are steel-concrete composite beams, obtain the first... The tower deflection and the change in compressive stress at the tower base of the cable after the first cable is initially tensioned to the corresponding target cable force value; among which, It is a positive integer. The initial value is 1;

[0024] S452, determine whether the tower deflection value is less than a first preset threshold, and determine whether the change in tower root compressive stress is less than a second preset threshold;

[0025] S453, when both of the following conditions are met simultaneously: the tower deviation value is less than the first preset threshold and the tower root compressive stress change is less than the second preset threshold, determine the first... The cable is in a safe state after being initially tensioned to the corresponding target cable force value;

[0026] S454, +1 is assigned to Repeat steps S451 to S453 until all stay cables have been verified.

[0027] Preferably, the step S45 is followed by the following step:

[0028] S4501, when the middle span and side spans are asymmetrical, and the middle span is a steel-concrete composite beam and the side spans are concrete main beams, obtain the first... The tower deflection of the cable-stayed tower after initial tensioning to the corresponding target cable force value, the change in compressive stress at the tower base, and the tensile stress in the concrete main beam of the side span; among which, It is a positive integer. The initial value is 1;

[0029] S4502, determine whether the tower deflection value is less than a first preset threshold, determine whether the change in tower root compressive stress is less than a second preset threshold, and determine whether the tensile stress of the side span concrete main beam is less than a third preset threshold.

[0030] S4503, when three conditions are met simultaneously: the tower deflection value is less than the first preset threshold, the change in 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 first condition is determined. The cable is in a safe state after being initially tensioned to the corresponding target cable force value;

[0031] S4504, +1 is assigned to Repeat steps S4501 to S4503 until all stay cables have been verified.

[0032] Preferably, the second preset threshold is obtained through the following steps:

[0033] Obtain the compressive stress reserve at the base of the cable tower under its own weight only. And obtain the compressive stress control threshold at the root of the tower. ;

[0034] Determine the compressive stress reserve and the compressive stress specification control threshold The difference in compressive stress between them is used as the second preset threshold.

[0035] Preferably, the first preset threshold is obtained through the following steps:

[0036] Obtain the compressive stress at the base of the tower, and ensure that the compressive stress at the base of the tower is equal to the specified compressive stress control threshold. At that time, the tower offset value of the tower is determined. and the tower offset value As the first preset threshold.

[0037] Preferably, the step S453 is followed by the following step:

[0038] If at least one of the following conditions is not met: the tower deviation value is less than a first preset threshold, or the tower root compressive stress change is less than a second preset threshold, then the determination is made that... The cable-stayed cable is in an unsafe state after being initially tensioned to the corresponding target cable force value;

[0039] Reduce the cable tension of the stay cable on the side of the tower's deviation, or add ballast on the other side of the tower's deviation, or increase the cable tension of the stay cable on the other side of the tower's deviation, until both of the following conditions are met simultaneously: the tower deviation value is less than the first preset threshold and the change in tower root compressive stress is less than the second preset threshold, then proceed to step S454.

[0040] Preferably, the step S4502 is followed by the following step:

[0041] If at least one of the following conditions is not met: the tower deflection value is less than the first preset threshold, the change in 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 force of the stay cable on the deflected side of the tower is reduced, or ballast is installed on the other side of the tower deflection, or the cable force of the stay cable on the other side of the tower deflection is increased, until all three conditions are met simultaneously: the tower deflection value is less than the first preset threshold, the change in 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, then proceed to step S4503.

[0042] Preferably, shear studs are provided on the top surface of the steel main beam of the wet joint of the bridge deck.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This application ensures the compressive stress reserve of the bridge deck during the operational phase when using incremental launching construction for composite beam cable-stayed bridges. Furthermore, it eliminates the need for extensive prestressed corrugated pipes and steel strands in the bridge deck within the positive bending moment zone, resulting in good overall bridge deck integrity. It also addresses the challenge of applying steel box girders to mountainous or non-navigable waterways, as detailed below:

[0045] (1) In the positive bending moment zone of this application, a large number of prestressed corrugated pipes and steel strands are not required in the bridge deck. This can save time for prestressed steel strand threading, tensioning and grouting curing, as well as the equipment and material costs related to prestressed steel strand tensioning. At the same time, the absence of prestressed corrugated pipes in the bridge deck results in better overall integrity of the bridge deck, thereby achieving the goals of improving construction efficiency, reducing construction costs and ensuring construction quality.

[0046] (2) This application makes full use of the deformation characteristics of cable-stayed bridges and the stress characteristics of steel main beams, cables and concrete bridge decks. During the construction process, due to the relatively small dead load of cable-stayed bridges, the stress amplitude of cables and steel main beams is small when the bridge deck is not paved and the second-stage dead load is not applied. The initial tension of the cables is appropriately increased. After the subsequent installation of the bridge deck and the overlapping of wet joints, the over-tensioned cable force is released. The stress of the steel main beam and cables can also be within the specification range. The stress performance of steel and concrete materials is fully utilized, and the material utilization efficiency during the construction process is improved. By adjusting the process, the bridge deck is subjected to compressive stress. The construction method has clear process and is easy to operate.

[0047] (3) This application can realize the application scenarios such as steel box composite beams, which greatly reduces the transportation requirements in mountainous or navigable areas. This application can also be applied to composite beam cable-stayed bridges with various cross sections. This application solves the problem of bridge deck compressive stress reserve during the jacking construction of composite beam cable-stayed bridges, which helps to apply the jacking construction method in the construction of composite beam cable-stayed bridges. Attached Figure Description

[0048] 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.

[0049] Figure 1 This is a schematic flowchart of a construction method according to an embodiment of the present invention;

[0050] Figure 2 This is a structural diagram after construction step S1 in one embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram of the structure after construction step S2 in one embodiment of the present invention;

[0052] Figure 4 This is a schematic diagram of the structure after construction step S3 in one embodiment of the present invention;

[0053] Figure 5 This is a schematic diagram of the structure after construction step S4 in one embodiment of the present invention;

[0054] Figure 6 This is a structural diagram after construction step S5 in one embodiment of the present invention;

[0055] Figure 7 This is a structural diagram after construction step S6 in one embodiment of the present invention;

[0056] Figure 8 This is a structural diagram after construction step S7 in one embodiment of the present invention.

[0057] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0058] Explanation of icon numbers:

[0059] 11. Tower; 12. Transition pier; 13. Temporary assembly support at the bridgehead; 14. Temporary support pier at the bridge site; 15. Steel main girder; 16. Front guide beam; 17. Rear guide beam; 18. Cable stays; 19. Bridge deck. Detailed Implementation

[0060] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0062] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0063] Please see the appendix Figures 1 to 8 The present invention provides a construction method for a composite beam cable-stayed bridge in one embodiment, comprising the following steps:

[0064] S1. Construct the cable tower 11, install the transition pier 12, the temporary bridge abutment assembly support 13, and the temporary support pier 14 at the bridge site. Specifically, the foundation of the temporary bridge abutment assembly support 13 can be reinforced to ensure that the foundation settlement meets the specifications under the load of the steel main beam 15. The temporary bridge abutment assembly support 13 can be made of steel pipe support. The top elevation of the temporary bridge abutment assembly 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.

[0065] S2, assemble the steel main beams 15 in batches according to the manufacturing alignment, install the front guide beam 16, the rear guide beam 17, and the jacking equipment; as a preferred embodiment, assemble the first batch of jacking steel main beams 15 on the temporary assembly support 13 at the bridgehead according to the manufacturing alignment of the steel main beams 15, and monitor and adjust the alignment; wherein, the manufacturing alignment is the stress-free manufacturing alignment of the steel main beams 15 obtained by finite element calculation according to the construction procedure, and the stress-free manufacturing alignment = design elevation + construction pre-camber + completed bridge pre-camber. During the assembly of the steel main beams 15, the connection between the steel main beams 15 can be made by welding or bolts. Install the front guide beam 16, the rear guide beam 17, and the jacking equipment (not shown in the figure) required for jacking. Install the operating platform, tank wheels, or PTFE sliding plates, etc., required for jacking on the top of the transition pier 12 and the temporary support pier 14 at the bridge site. This part is the conventional technical content of jacking construction and will not be described in detail here.

[0066] S3. The main steel beams 15 are jacked into position and lowered in batches using a jacking device. The front guide beam 16, rear guide beam 17, temporary bridge abutment assembly support 13, and the jacking device are then removed. As a preferred implementation, after each batch of main steel beams 15 is jacked, the assembly elevation of each subsequent batch must be adjusted based on the elevation of the previous batch. During the jacking process, the displacement and stress at the cantilever front end of the main steel beam 15 should be monitored to ensure that the axial deviation of the main steel beam 15 does not exceed ±20mm. If it does, it should be corrected by adjusting the jacking force on the left and right sides of the main steel beam 15. Simultaneously, the stress of the main steel beam 15 must not exceed the specification limits. Once the main steel beam 15 is jacked into position, the permanent supports for the cable tower 11 and transition pier 12 are installed. The main steel beam 15 is then lowered using jacks. The front guide beam 16, rear guide beam 17, temporary bridge abutment assembly support 13, and the jacking device are then removed. The front guide beam 16 and the rear guide beam 17 are used to shorten the cantilever length of the main steel beam 15 and reduce the stress on the main steel beam 15 during the jacking process.

[0067] S4, initially tension each stay cable 18 to the corresponding target cable force value, so that the main beam alignment in the positive bending moment zone is in an upward convex state, and then remove the temporary support pier 14 at the bridge site.

[0068] S5, bridge deck 19 is installed in the positive bending moment zone, and the wet joint of the bridge deck is overlapped. Under the self-weight of bridge deck 19 and the wet joint of the bridge deck, the steel main beam 15 displaces downward for the first time, and the bridge deck 19 generates compressive stress. Under the self-weight of the bridge deck 19 and the wet joint of the bridge deck, the steel main beam 15, which is in an upward convex state, begins to displace downward and tends to the design line, compressing the concrete bridge deck 19 at its top, causing compressive stress in the bridge deck 19 in the positive bending moment zone. .

[0069] S6, sequentially release the cable force of the stay cables 18 in the area of ​​the wet joint of the superimposed bridge deck, so that the steel main girder 15 will move downward again, and the bridge deck 19 will generate an increase in compressive stress. The release of cable tension reduces the upward pulling force of the stay cables 18 on the main steel girder 15, causing the main steel girder 15 to displace further downward. This second downward displacement further compresses the concrete bridge deck 19 in the positive bending moment zone, thus increasing its compressive stress. On the basis of increasing the compressive stress increment .

[0070] S7. In the negative bending moment zone, install bridge deck 19, overlap the wet joints of the bridge deck, tension the prestressed steel strands of bridge deck 19 in the negative bending moment zone, and then construct the bridge deck pavement and ancillary facilities. After the bridge deck 19 in the positive bending moment zone is overlapped and the cable tension of the stay cables 18 is released, the main steel beam 15 returns to the design alignment control range, such as... Figure 8As shown, the bridge deck 19 in the negative bending moment zone is installed, and the wet joints of the bridge deck are overlapped. Since the negative bending moment zone is overlapped last, the negative bending moment zone will not generate a negative bending moment due to the construction of the bridge deck 19 in the positive bending moment zone and the release of cable force from the stay cables 18. The prestressed steel strands of the bridge deck 19 in the negative bending moment zone are tensioned, and then the bridge deck pavement and ancillary facilities are constructed. After acceptance, the bridge is opened to traffic.

[0071] The advantages of adopting the proposed solution are as follows:

[0072] (1) The bridge deck 19 in the positive bending moment zone does not need to be equipped with a large number of prestressed corrugated pipes and steel strands, which can save time for prestressed steel strand threading, tensioning and grouting curing, as well as save equipment and material costs related to prestressed steel strand tensioning. At the same time, the bridge deck 19 has no prestressed corrugated pipes, and the integrity of the bridge deck 19 is better, thus achieving the purpose of improving construction efficiency, reducing construction costs and ensuring construction quality.

[0073] (2) This application makes full use of the deformation characteristics of cable-stayed bridges and the stress characteristics of steel main beam 15, cable stays 18 and concrete bridge deck 19. During the construction process, due to the relatively small dead load of cable-stayed bridges, the stress amplitude of cable stays 18 and steel main beam 15 is small when the bridge deck is not paved and the second-stage dead load is not applied. The initial tension of the cable is appropriately increased. After the bridge deck 19 is installed and stacked, the over-tensioned cable force is released. The stress of steel main beam 15 and cable stays 18 can also be within the specification range. The stress performance of steel and concrete materials is fully utilized, and the material utilization efficiency during the construction process is improved. By adjusting the process, the bridge deck 19 generates compressive stress. The construction method has clear process and is simple to operate.

[0074] (3) By adopting the scheme of this application, the application scenarios of steel box composite beam sections can be improved, the transportation requirements in mountainous or navigable areas can be greatly reduced, and the method can also be applied to composite beam cable-stayed bridges with various sections. This application solves the problem of bridge deck 19 compressive stress reserve during the jacking construction of composite beam cable-stayed bridges, which helps to apply the jacking construction method in the construction of composite beam cable-stayed bridges.

[0075] In a preferred embodiment, the target cable force value in step S4 is obtained through the following steps:

[0076] S41. Without considering prestressing measures, calculate the tensile stress distribution data of bridge deck 19 during the completed bridge stage and operation state, and compare it with the specification requirements to obtain the target value of compressive stress required to be applied to bridge deck 19 in the entire bridge area to meet the specification stress requirements. Specifically, without considering prestressing measures, following the construction sequence S1 to S5, the tensile stress distribution data of bridge deck 19 in the completed bridge stage and operational state are calculated, and compared with the specifications, the target compressive stress value required to be applied to bridge deck 19 in the entire bridge area to meet the specified stress requirements is obtained. Target value of compressive stress This represents the compressive stress corresponding to the bridge deck 19 across the entire bridge area. The additional compressive stress required to ensure that the tensile stress in the bridge deck 19 does not exceed the allowable value specified in the code under the most unfavorable working conditions is determined by this calculation. The target compressive stress value needs to be reserved in advance to offset the tensile stress generated during future operation.

[0077] S42, based on the target compressive stress value With the compressive stress The difference is used to determine the increase in compressive stress that needs to be achieved by releasing the tension of cable 18. Increment of compressive stress The compressive stress generated solely by the self-weight deflection in step S5 That's not enough. In the subsequent step S6, during the release of the cable tension in the stay cable 18, it's also necessary to generate an additional compressive stress increment in the bridge deck 19 through the secondary deflection of the main steel beam 15. The target value needs to be achieved by actively adjusting the tension of the cable.

[0078] S43, calculate the effect matrix of releasing the stay cable 18 on the increase of compressive stress in the bridge deck 19.

[0079] S44, according to the compressive stress increment Based on the aforementioned influence matrix, the required increase in cable force of the stay cables 18 during the initial tensioning stage can be obtained. Specifically, the influence matrix can be obtained based on the construction procedures and the impact of the release of cable force of each stay cable 18 on the change of compressive stress in the bridge deck 19. Mature technical methods already exist for this part, so they will not be elaborated here.

[0080] S45, determine the target cable force value for each stay cable 18 during the initial tensioning stage based on the cable force increment of the stay cables 18. As a preferred embodiment, without considering the overlap of the bridge deck 19 and the increase in compressive stress on the bridge deck 19 due to the release of cable force from the stay cables 18, the target compressive stress value is obtained by increasing the compressive stress on the bridge deck 19 to the target value through tensioning the prestressed steel strands in the positive bending moment zone. The initial tension force of each of the 18 stay cables was calculated based on the required process of tensioning the prestressed steel strands. Then, by adding the cable force increment of the cable 18 calculated above, the target cable force value of each cable 18 in the initial tensioning stage of this scheme can be obtained.

[0081] Through mechanical analysis and reverse derivation in this embodiment, the target value of cable force is calculated, which accurately ensures the crack resistance and long-term durability of the bridge deck 19 after the bridge is completed.

[0082] In a preferred embodiment, step S5 specifically includes the following steps:

[0083] After determining the location of the maximum positive bending moment in the positive bending moment zone, the bridge deck 19 and the composite bridge deck wet joint are hoisted in segments from the location of the maximum positive bending moment towards the transition pier 12. Then, the bridge deck 19 and the composite bridge deck wet joint are hoisted in segments from the location of the maximum positive bending moment towards the tower 11. Under the self-weight of the bridge deck 19 and the bridge deck wet joint, the steel main beam 15 displaces downward for the first time, and the bridge deck 19 generates compressive stress. .

[0084] As a better example, the bridge deck 19 can be installed in sections and blocks, and the wet joints of the bridge deck can be overlapped. The size of the bridge deck 19 needs to be determined according to the span of the bridge. It is recommended to overlap the bridge deck 19 with 2-4 sections of steel main beam 15.

[0085] In a preferred embodiment, the following steps are included after step S45:

[0086] S451, when the middle span and side spans are asymmetrical, and both the middle span and side spans are steel-concrete composite beams, obtain the first... The tower deflection of the tower 11 and the change in compressive stress at the base of the tower 11 after the initial tension of the stay cable 18 to the corresponding target cable force value; among which, It is a positive integer. The initial value is 1;

[0087] S452, determine whether the tower deflection value is less than a first preset threshold, and determine whether the change in tower root compressive stress is less than a second preset threshold;

[0088] S453, when both of the following conditions are met simultaneously: the tower deviation value is less than the first preset threshold and the tower root compressive stress change is less than the second preset threshold, determine the first... After the first cable-stayed cable 18 is initially tensioned to the corresponding target cable force value, it is in a safe state.

[0089] S454, +1 is assigned to Repeat steps S451 to S453 until all stay cables 18 have been verified.

[0090] It is worth noting that if the bridge is asymmetrical in terms of the middle span and the side spans, and both the middle span and the side spans are steel-concrete composite beams, after the cable force of the stay cable 18 increases during the initial tensioning stage, the stress of the main steel beam 15 should be ensured to be within the range required by the specification. For asymmetrical cable-stayed bridges, the tensioning of the initial tensioning cable and the release of the stay cable 18 should ensure that the stress of the concrete at the root section of the tower 11 is within the range required by the specification, even with a certain tower deflection.

[0091] By +1 is assigned to Tensioning and verification are performed on the next stay cable 18. Returning to step S451, the process is repeated for the first cable. +1 stay cable 18 is tensioned to its target cable force, and then the tower deflection and tower root compressive stress change after tensioning are obtained for dual-indicator judgment to determine whether it is in a safe state. By controlling the tower deflection increment caused by tensioning a single cable to not exceed the first preset threshold, excessive horizontal displacement of tower 11 due to asymmetrical loading or excessive cable force during construction is prevented, thereby avoiding the risk of tower instability, tilting, or even collapse. And by controlling the tower root compressive stress increment caused by tensioning a single cable to not exceed the second preset threshold, it is ensured that the concrete at the base of tower 11 is always in a safe compressive state with sufficient strength reserve.

[0092] In another preferred embodiment, the step S45 is followed by the following steps:

[0093] S4501, when the middle span and side spans are asymmetrical, and the middle span is a steel-concrete composite beam and the side spans are concrete main beams, obtain the first... The tower deflection of the tower 11 after the initial tension of the stay cable 18 to the corresponding target cable force value, the change in compressive stress at the base of the tower 11, and the tensile stress of the concrete main beam in the side span; among which, It is a positive integer. The initial value is 1;

[0094] S4502, determine whether the tower deflection value is less than a first preset threshold, determine whether the change in tower root compressive stress is less than a second preset threshold, and determine whether the tensile stress of the side span concrete main beam is less than a third preset threshold.

[0095] S4503, when three conditions are met simultaneously: the tower deflection value is less than the first preset threshold, the change in 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 first condition is determined. After the first cable-stayed cable 18 is initially tensioned to the corresponding target cable force value, it is in a safe state.

[0096] S4504, +1 is assigned to Repeat steps S4501 to S4503 until all stay cables 18 have been verified.

[0097] It is worth noting that if the bridge has an asymmetrical mid-span and side-span configuration, and the mid-span is a steel-concrete composite beam while the side-spans are concrete main beams, after the cable force of the stay cable 18 increases during the initial tensioning stage, the stress of the steel main beam 15 should be ensured to remain within the specified range. +1 is assigned to Tensioning and verification are performed on the next stay cable 18, then return to step S4501 to perform the following steps: +1 stay cable 18 is tensioned to its target cable force, and then the tower deflection value, tower root compressive stress change and concrete main beam tensile stress after tensioning are obtained. The three indicators are judged to determine whether it is in a safe state and to ensure sufficient safety reserve.

[0098] Preferably, the second preset threshold is obtained through the following steps:

[0099] Obtain the compressive stress reserve at the root of the cable tower 11 under its own weight only. And obtain the compressive stress control threshold at the root of Tower 11. ;

[0100] Determine the compressive stress reserve and the compressive stress specification control threshold The difference in compressive stress between them is used as the second preset threshold.

[0101] Preferably, the first preset threshold is obtained through the following steps:

[0102] The compressive stress at the root of cable tower 11 is obtained, and the compressive stress at the root of cable tower 11 is equal to the compressive stress specification control threshold. At that time, the tower offset value of the tower 11 is determined. and the tower offset value As the first preset threshold.

[0103] Furthermore, the following steps are included after step S453:

[0104] If at least one of the following conditions is not met: the tower deviation value is less than a first preset threshold, or the tower root compressive stress change is less than a second preset threshold, then the determination is made that... The cable 18 was in an unsafe state after being initially tensioned to the corresponding target cable force value;

[0105] Reduce the cable force of the stay cable 18 on the offset side of the tower 11, or construct additional weight on the other side of the tower 11 offset, or increase the cable force of the stay cable 18 on the other side of the tower 11 offset, until both of the following conditions are met simultaneously: the tower offset value is less than the first preset threshold and the change in tower root compressive stress is less than the second preset threshold, then proceed to step S454.

[0106] Specifically, if at least one of the following conditions is not met: the tower deviation value is less than a first preset threshold, or the change in tower root compressive stress is less than a second preset threshold, then the determination is made that... After the first cable (18) is initially tensioned to its target tension value, it is in an unsafe state and requires immediate action. Tensioning the next cable cannot proceed directly. This embodiment provides three optional adjustment methods, all aiming to apply a force or torque opposite to the current adverse effect to achieve balance. Only when both tower deflection and tower root stress meet the safety threshold requirements is the first cable deemed unsafe. The unsafe condition caused by the tensioning of the 18 stay cables has been adjusted to a safe state.

[0107] Furthermore, the step S4502 is followed by the following steps:

[0108] If at least one of the following conditions is not met: the tower offset value is less than the first preset threshold, the change in 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 force of the stay cable 18 on the offset side of the tower 11 is reduced, or the ballast is installed on the other side of the tower 11 offset, or the cable force of the stay cable 18 on the other side of the tower 11 offset is increased, until all three conditions are met simultaneously: the tower offset value is less than the first preset threshold, the change in 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, then proceed to step S4503.

[0109] Specifically, if at least one of the following conditions is not met: the tower deflection value is less than a first preset threshold, the change in tower root compressive stress is less than a second preset threshold, and the tensile stress in the side span concrete main beam is less than a third preset threshold, then the first threshold is determined to be... After the first cable (18) is initially tensioned to its target tension value, it is in an unsafe state and requires immediate action. Tensioning the next cable cannot proceed directly. This embodiment provides three optional adjustment methods, all aiming to apply a force or moment opposite to the current adverse effect to achieve balance. Tensioning is only considered safe when the tower deflection, tower root stress, and tensile stress in the side span concrete main beam all meet the safety threshold requirements. The unsafe condition caused by the tensioning of the 18 stay cables has been adjusted to a safe state.

[0110] Preferably, shear studs are provided on the top surface of the steel main beam 15 at the wet joint of the bridge deck. Further, after the bridge deck 19 and the steel main beam 15 are connected by reinforcing bars of the bridge deck 19, concrete is poured in place at the wet joint for connection, and shear studs are provided on the top surface of the steel main beam 15 at the wet joint.

[0111] The above are merely preferred embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention’s specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A construction method for a composite beam cable-stayed bridge, characterized in that, Includes the following steps: S1, Construction of cable towers, installation of transition piers, temporary assembly supports at bridgeheads, and temporary support piers at bridge sites; S2 involves assembling the steel main beams in batches according to the manufacturing line, installing the front guide beam, rear guide beam, and jacking equipment; S3: The steel main beams were pushed into place and lowered in batches using jacking equipment, and the front guide beam, rear guide beam, temporary assembly support at the bridgehead, and jacking equipment were dismantled. S4, initially tension each stay cable to the corresponding target cable force value, so that the main beam alignment in the positive bending moment zone is in an upward convex state, and then remove the temporary support piers at the bridge site; S5, the bridge deck is installed in the positive bending moment zone, and the wet joints of the bridge deck are overlapped. Under the self-weight of the bridge deck and the wet joints, the main steel beam undergoes its first downward displacement, and the bridge deck generates compressive stress. ; S6, sequentially release the cable forces in the wet joint area of ​​the superimposed bridge deck, causing the main steel beam to shift downwards again, resulting in an increase in compressive stress in the bridge deck. ; S7 involves installing the bridge deck in the negative bending moment zone, overlapping the wet joints of the bridge deck, tensioning the prestressed steel strands of the bridge deck in the negative bending moment zone, and then constructing the bridge deck paving and ancillary facilities.

2. The construction method for a composite beam cable-stayed bridge according to claim 1, characterized in that, The target cable force value in step S4 is obtained through the following steps: S41. Without considering prestressing measures, calculate the tensile stress distribution data of the bridge deck during the completed bridge stage and operation state, and compare it with the specifications to obtain the target value of compressive stress required to meet the stress requirements of the specifications for the entire bridge area. ; S42, based on the target compressive stress value With the compressive stress The difference yields the increase in compressive stress that needs to be achieved through the release of the stay cables. ; S43, calculate the influence matrix of releasing the stay cables on the increase of compressive stress in the bridge deck; S44, according to the compressive stress increment Based on the influence matrix, the required cable force increment for the initial tensioning stage is obtained; S45, determine the target cable force value for each cable during the initial tensioning stage based on the cable force increment.

3. The construction method for a composite beam cable-stayed bridge according to claim 2, characterized in that, Step S5 specifically includes the following steps: The location of the maximum positive bending moment in the positive bending moment zone is determined. From this location, the bridge deck panels and composite bridge deck wet joints are hoisted in segments towards the transition pier. Then, from the same location, the bridge deck panels and composite bridge deck wet joints are hoisted again in segments towards the tower. Under the self-weight of the bridge deck panels and their wet joints, the main steel beam undergoes its first downward displacement, generating compressive stress in the bridge deck panels. .

4. The construction method for a composite beam cable-stayed bridge according to claim 2, characterized in that, Following step S45, the following steps are also included: S451, when the middle span and side spans are asymmetrical, and both the middle span and side spans are steel-concrete composite beams, obtain the first... The tower deflection and the change in compressive stress at the tower base of the cable after the first cable is initially tensioned to the corresponding target cable force value; among which, It is a positive integer. The initial value is 1; S452, determine whether the tower deflection value is less than a first preset threshold, and determine whether the change in tower root compressive stress is less than a second preset threshold; S453, when both of the following conditions are met simultaneously: the tower deviation value is less than the first preset threshold and the tower root compressive stress change is less than the second preset threshold, determine the first... The cable is in a safe state after being initially tensioned to the corresponding target cable force value; S454, +1 is assigned to Repeat steps S451 to S453 until all stay cables have been verified.

5. The construction method for a composite beam cable-stayed bridge according to claim 2, characterized in that, Following step S45, the following steps are also included: S4501, when the middle span and side spans are asymmetrical, and the middle span is a steel-concrete composite beam and the side spans are concrete main beams, obtain the first... The tower deflection of the cable-stayed tower after initial tensioning to the corresponding target cable force value, the change in compressive stress at the tower base, and the tensile stress in the concrete main beam of the side span; among which, It is a positive integer. The initial value is 1; S4502, determine whether the tower deflection value is less than a first preset threshold, determine whether the change in tower root compressive stress is less than a second preset threshold, and determine whether the tensile stress of the side span concrete main beam is less than a third preset threshold. S4503, when three conditions are met simultaneously: the tower deflection value is less than the first preset threshold, the change in 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 first condition is determined. The cable is in a safe state after being initially tensioned to the corresponding target cable force value; S4504, +1 is assigned to Repeat steps S4501 to S4503 until all stay cables have been verified.

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

7. The construction method for a composite beam cable-stayed bridge according to claim 6, characterized in that, The first preset threshold is obtained through the following steps: Obtain the compressive stress at the base of the tower, and ensure that the compressive stress at the base of the tower is equal to the specified compressive stress control threshold. At that time, the tower offset value of the tower is determined. and the tower offset value As the first preset threshold.

8. The construction method for a composite beam cable-stayed bridge according to claim 4, characterized in that, Following step S453, the following steps are also included: If at least one of the following conditions is not met: the tower deviation value is less than a first preset threshold, or the tower root compressive stress change is less than a second preset threshold, then the determination is made that... The cable-stayed cable is in an unsafe state after being initially tensioned to the corresponding target cable force value; Reduce the cable tension of the stay cable on the side of the tower's deviation, or add ballast on the other side of the tower's deviation, or increase the cable tension of the stay cable on the other side of the tower's deviation, until both of the following conditions are met simultaneously: the tower deviation value is less than the first preset threshold and the change in tower root compressive stress is less than the second preset threshold, then proceed to step S454.

9. The construction method for a composite beam cable-stayed bridge according to claim 5, characterized in that, Following step S4502, the following steps are also included: If at least one of the following conditions is not met: the tower deflection value is less than the first preset threshold, the change in 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 force of the stay cable on the deflected side of the tower is reduced, or ballast is installed on the other side of the tower deflection, or the cable force of the stay cable on the other side of the tower deflection is increased, until all three conditions are met simultaneously: the tower deflection value is less than the first preset threshold, the change in 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, then proceed to step S4503.

10. The construction method for a composite beam cable-stayed bridge according to claim 1, characterized in that, Shear studs are installed on the top surface of the steel main beam at the wet joint of the bridge deck.

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