Combined bridge construction method

Abstract

The invention discloses a combined bridge construction method, which relates to the technical field of cross-line bridge construction, and comprises the following steps: assembling a steel main beam; a flat bottom plate combined bridge deck slab steel bottom die is fixedly connected to the middle section of the assembled steel main beam, the span of the flat bottom plate combined bridge deck slab steel bottom die is not smaller than that of a traffic line below the bridge section to be constructed, and a combined structure anti-collision guardrail steel side die is fixedly connected to the flat bottom plate combined bridge deck slab steel bottom die; erecting the assembled steel main beam on a bridge section to be constructed; concrete bridge deck formworks are installed on the steel girders on the two sides of the flat bottom plate combined bridge deck steel bottom die, and a reinforcing mesh is arranged; first anti-collision guardrail reinforcing steel bars of side spans on the two sides of the flat bottom plate combined bridge deck slab steel bottom die and second anti-collision guardrail reinforcing steel bars of the combined structure anti-collision guardrail steel side die are arranged; anti-collision guardrail pouring formworks are arranged outside the first anti-collision guardrail steel bars; anti-collision guardrail concrete is poured; and constructing an asphalt pavement layer. The method is simple and convenient to operate, and has small influence on the traffic line below.

Description

Technical Field

[0002] This invention relates to the field of cross-line bridge construction technology, and in particular to a method for constructing combined bridges. Background Technology

[0003] The current steel-concrete composite bridge deck is mainly constructed by on-site casting with wooden formwork. This construction method has the following shortcomings: (1) After the steel beam is erected, the wooden formwork needs to be installed by hoisting the formwork or erecting a support system. After the bridge deck reaches the required strength, the wooden formwork and the corresponding support structure need to be removed. This process inevitably involves a lot of work under the bridge, resulting in complicated construction operations, high construction difficulty, and low construction efficiency. (2) Due to the gaps between the wooden formwork, foam glue is often used to seal them to prevent mortar from flowing out. Even so, the concrete mortar will still overflow from the gaps in the formwork due to its own weight. If the bridge crosses a traffic line, the overflowing mortar will drip down and affect the traffic on the lower side. If the traffic on the lower side is closed during construction, it will cause a large traffic economic loss. (3) The structural system or hoisting system used to temporarily support the wooden formwork is prone to unreliable connection. Once the support structure fails under the weight of the concrete, it is very easy for the wooden formwork to fall down, which will bring safety hazards to the traffic on the lower side. Therefore, a composite bridge construction method is urgently needed to solve the above-mentioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a combined bridge construction method to solve the problems existing in the prior art, which is simple to operate and has little impact on the traffic lines below.

[0005] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for constructing a combined bridge, comprising the following steps: S1: Assembled steel main beam; S2: Fix the flat bottom plate composite bridge deck steel bottom formwork to the middle section of the assembled steel main beam, and the span of the flat bottom plate composite bridge deck steel bottom formwork is not less than the span of the traffic line under the bridge section to be constructed. Fix the composite structure anti-collision guardrail steel side formwork to the flat bottom plate composite bridge deck steel bottom formwork. S3: The assembled steel main beam, together with the flat bottom plate composite bridge deck steel bottom formwork and the composite structure anti-collision guardrail steel side formwork, is installed on the bridge section to be constructed. S4: Install concrete bridge deck formwork on the main steel beams on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck; S5: The first steel mesh is laid in the concrete bridge deck formwork on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck, and the second steel mesh is laid in the steel bottom formwork of the flat bottom plate composite bridge deck. S6: Pour the positive bending moment area on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck, then pour the positive bending moment area at the steel bottom formwork of the flat bottom plate composite bridge deck, and finally pour the negative bending moment area at the steel bottom formwork of the flat bottom plate composite bridge deck. S7: Lay out the first anti-collision guardrail reinforcement on both sides of the side span of the flat bottom plate composite bridge deck steel bottom formwork and the second anti-collision guardrail reinforcement on the composite structure anti-collision guardrail side formwork; S8: Install the anti-collision guardrail casting formwork outside the first anti-collision guardrail reinforcement; S9: Pour concrete for the first and second crash barriers; S10: Construction asphalt pavement layer.

[0006] In some implementations, step S2 includes S21: The bottom formwork of the flat bottom plate composite bridge deck is spot-welded to the middle section of the main steel beam, and the side formwork of the composite structure anti-collision guardrail is spot-welded to the bottom formwork of the flat bottom plate composite bridge deck.

[0007] In some implementations, steps S31 and S32 are included after step S3. S31: Check whether the deformation of the flat bottom plate composite bridge deck steel bottom formwork exceeds the preset value. If it does not exceed the preset value, then continuously weld the flat bottom plate composite bridge deck steel bottom formwork to the middle section of the steel main beam. If it exceeds the preset value, then after correction, continuously weld the flat bottom plate composite bridge deck steel bottom formwork to the middle section of the steel main beam. S32: Check whether the deformation of the steel side mold of the composite structure anti-collision guardrail exceeds the preset value. If it does not exceed the preset value, the steel side mold of the composite structure anti-collision guardrail is continuously welded to the steel bottom mold of the flat bottom plate composite bridge deck. If it exceeds the preset value, it needs to be corrected before the steel side mold of the composite structure anti-collision guardrail is continuously welded to the steel bottom mold of the flat bottom plate composite bridge deck.

[0008] In some embodiments, the concrete bridge deck formwork in step S4 includes a support and a wooden formwork. The support is supported on the lower flange of the steel main beam, and the wooden formwork is placed on the support. The upper surface of the wooden formwork is at the same horizontal line as the lower surface of the flat bottom plate combined bridge deck steel bottom formwork.

[0009] In some embodiments, in step S5, the first reinforcing mesh is a double-layer reinforcing mesh, and the second reinforcing mesh is a single-layer reinforcing mesh. The double-layer reinforcing mesh includes two layers of longitudinal and transverse reinforcing bars distributed vertically, and the single-layer reinforcing mesh includes one layer of longitudinal and transverse reinforcing bars. The longitudinal and transverse reinforcing bars on the upper layer of the first reinforcing mesh and the one layer of longitudinal and transverse reinforcing bars of the second reinforcing mesh are on the same horizontal plane, and the longitudinal reinforcing bars on the upper layer of the first reinforcing mesh and the longitudinal reinforcing bars of the second reinforcing mesh are the same reinforcing bars.

[0010] In some implementations, step S61 is included before step S6. S61: Check for water leakage between the steel bottom formwork of the flat bottom plate composite bridge deck and the upper flange of the steel main beam, and between the steel side formwork of the composite structure anti-collision guardrail and the steel bottom formwork of the flat bottom plate composite bridge deck. If there is water leakage, it needs to be sealed before pouring concrete; if there is no water leakage, pour concrete directly.

[0011] In some embodiments, in step S7, both the first and second crash barrier reinforcing bars include staggered transverse and longitudinal reinforcing bars, and the longitudinal reinforcing bars of the first and second crash barrier reinforcing bars are the same reinforcing bars.

[0012] In some embodiments, the anti-collision guardrail casting template in step S8 is a fixed steel template, and the inner surface of the anti-collision guardrail casting template is at the same level as the outer surface of the steel side mold of the combined structure anti-collision guardrail.

[0013] In some implementations, step S3 employs a construction method of integral jacking.

[0014] In some implementations, the steel bottom formwork of the flat bottom plate composite bridge deck is connected to the middle section of the steel main beam by stiffening ribs.

[0015] The present invention achieves the following technical effects compared to the prior art: The composite bridge construction method provided by this invention directly fixes the flat-bottomed composite bridge deck steel bottom formwork to the main steel beam. The span of the flat-bottomed composite bridge deck steel bottom formwork is not less than the span of the traffic lane beneath the bridge section to be constructed. When pouring concrete in this area, no additional pouring formwork is required; the flat-bottomed composite bridge deck steel bottom formwork directly serves as part of the pouring formwork, eliminating the complex formwork installation process. This simplifies operation, avoids long-term road occupancy, and prevents leakage of concrete, thus not affecting traffic beneath the bridge section. Furthermore, the flat-bottomed composite bridge deck steel bottom formwork is directly fixed to the top of the main steel beam, ensuring a secure connection and minimizing the impact on traffic beneath the bridge section. Moreover, the side spans (the portions on both sides of the flat-bottomed composite bridge deck steel bottom formwork) are constructed using traditional formwork casting methods outside the traffic lanes, avoiding the use of the flat-bottomed composite bridge deck steel bottom formwork for the entire section, achieving a balance between economy and applicability. During bridge construction, the side spans and middle spans are prone to downward positive bending moments due to their own weight, while the central support is prone to upward negative bending moments due to load transfer from both ends. Pouring concrete in this sequence allows it to solidify in the corresponding stress areas, resulting in strength sufficient to directly resist the bending moments in those areas and preventing early cracking caused by a mismatch between load and pouring sequence. Pouring the positive bending moment zone of the side spans first allows the weight of the side span concrete to balance some of the stress during the construction of the middle span, reducing deflection deformation during middle span pouring and indirectly reducing stress concentration in the negative bending moment zone of the central support, creating a stable stress environment for subsequent pouring of the negative bending moment zone. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a construction flowchart of the combined bridge construction method in some embodiments of the present invention; Figure 2 This is a schematic diagram of the assembly of the S1 steel main beam in some embodiments of the present invention; Figure 3 This is a schematic diagram of the overall jacking of the S3 steel main beam in some embodiments of the present invention; Figure 4 This is a schematic diagram of the structure of the checks in S31 and S32 in some embodiments of the present invention; Figure 5 This is a schematic diagram of the structure of the side span concrete bridge deck template in S4 in some embodiments of the present invention; Figure 6 This is a schematic diagram of the layout of the first steel mesh in some embodiments of the present invention; Figure 7 This is a schematic diagram of the layout of the second steel mesh in some embodiments of the present invention; Figure 8 This is a schematic diagram of the side span casting on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck in some embodiments of the present invention; Figure 9 This is a schematic diagram of the casting process at the bottom formwork of the flat-bottomed composite bridge deck in some embodiments of the present invention; Figure 10 This is a schematic diagram showing the layout of the reinforcing bars of the first anti-collision guardrail in some embodiments of the present invention; Figure 11 This is a schematic diagram showing the layout of the second anti-collision guardrail reinforcement in some embodiments of the present invention; Figure 12 This is a schematic diagram of the concrete pouring for the first crash barrier in some embodiments of the present invention; Figure 13 This is a schematic diagram of the concrete pouring for the second crash barrier in some embodiments of the present invention; Figure 14 This is a schematic diagram of the construction asphalt pavement layer on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck in some embodiments of the present invention; Figure 15 This is a schematic diagram of the construction asphalt pavement layer at the steel bottom formwork of the flat bottom plate composite bridge deck in some embodiments of the present invention; Figure 16This is a schematic diagram of the overall structure of a three-span continuous composite beam in some embodiments of the present invention.

[0018] In the diagram: 1-Steel main beam; 2-Steel bottom formwork for flat bottom plate composite bridge deck; 3-Steel side formwork for composite structure anti-collision guardrail; 4-Welding studs; 5-Assembly platform; 6-Guide beam; 7-Wooden formwork; 8-First steel mesh; 9-Second steel mesh; 10-Stirrups; 11-Asphalt pavement layer. Detailed Implementation

[0019] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The purpose of this invention is to provide a combined bridge construction method to solve the problems existing in the prior art, which is simple to operate and has little impact on the traffic lines below.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figures 1-16As shown, the present invention provides a method for constructing a composite bridge, including the following steps S1: assembling the steel main beam 1; specifically, transporting the factory-made steel main beam, the flat bottom plate composite bridge deck steel bottom mold 2, and the composite structure anti-collision guardrail steel side mold 3 to the bridge site, and setting up a temporary construction platform at the bridgehead for assembling the steel main beam 1. S2: Fix the flat-bottomed composite bridge deck steel bottom formwork 2 to the middle section of the assembled steel main beam 1, ensuring that the span of the flat-bottomed composite bridge deck steel bottom formwork 2 is not less than the span of the traffic line below the bridge section to be constructed. Fix the composite structure anti-collision guardrail steel side formwork 3 to the flat-bottomed composite bridge deck steel bottom formwork 2. S3: Install the assembled steel main beam 1, together with the flat-bottomed composite bridge deck steel bottom formwork 2 and the composite structure anti-collision guardrail steel side formwork 3, onto the bridge section to be constructed. S4: Install concrete bridge deck formwork on the steel main beams 1 on both sides of the flat-bottomed composite bridge deck steel bottom formwork 2. S5: Lay the first steel mesh 8 inside the concrete bridge deck formwork on both sides of the flat-bottomed composite bridge deck steel bottom formwork 2. S6: Lay the second steel mesh 9 on the steel bottom formwork 2 of the flat bottom plate composite bridge deck; S7: Pour concrete in the positive bending moment area of ​​the side spans on both sides of the steel bottom formwork 2 of the flat bottom plate composite bridge deck, then pour concrete in the positive bending moment area of ​​the steel bottom formwork 2 of the flat bottom plate composite bridge deck, and finally pour concrete in the negative bending moment area of ​​the steel bottom formwork 2 of the flat bottom plate composite bridge deck; S8: Lay the first anti-collision guardrail reinforcement on both sides of the side spans of the steel bottom formwork 2 of the flat bottom plate composite bridge deck and the second anti-collision guardrail reinforcement on the steel side formwork 3 of the composite structure anti-collision guardrail; S9: Lay the anti-collision guardrail pouring formwork outside the first anti-collision guardrail reinforcement; S10: Pour the first anti-collision guardrail concrete and the second anti-collision guardrail concrete; S11: Construct the asphalt pavement layer 11.

[0023] The flat-bottomed composite bridge deck steel bottom formwork 2 is a composite steel formwork that generally includes standard components such as flat formwork, internal corner formwork, and external corner formwork. The flat-bottomed composite bridge deck steel bottom formwork 2 is directly fixed to the steel main beam 1, and the span of the flat-bottomed composite bridge deck steel bottom formwork 2 is not less than the span of the traffic line under the bridge section to be constructed, preferably equal to the span of the traffic line under the bridge section to be constructed. When pouring concrete in this area, there is no need to set up additional pouring formwork. The flat-bottomed composite bridge deck steel bottom formwork 2 can be used directly as part of the pouring formwork, which saves the complicated formwork setting process, is easy to operate, does not occupy the road for a long time, and the flat-bottomed composite bridge deck steel bottom formwork 2 will not leak, the concrete will not leak out, and it will not affect the traffic under the bridge section to be constructed. Furthermore, the flat-bottomed composite bridge deck steel bottom formwork 2 is directly fixed to the top of the steel main beam 1, the connection is not easy to fail, and it will not fall off, so the impact on the traffic under the bridge section to be constructed is minimal.

[0024] Furthermore, since the side spans (the portions on both sides of the flat-bottomed composite bridge deck steel formwork 2) are constructed outside the traffic lines using traditional formwork casting methods, the use of the flat-bottomed composite bridge deck steel formwork 2 for the entire section is avoided, achieving a balance between economy and applicability. During the bridge construction phase, the side spans and middle spans are prone to downward positive bending moments due to their own weight, while the middle support is prone to upward negative bending moments due to the load transfer at both ends. Pouring in this order allows the concrete to solidify in the corresponding stress areas, and the resulting strength can directly resist the bending moment in those areas, avoiding early cracks caused by a mismatch between load and pouring sequence. Pouring the positive bending moment area of ​​the side spans first can utilize the weight of the side span concrete to balance some of the stress during the construction of the middle span, reducing deflection deformation during the pouring of the middle span, and indirectly reducing stress concentration in the negative bending moment area of ​​the middle support, creating a stable stress environment for the subsequent pouring of the negative bending moment area. The side span concrete is poured and solidified first, providing stable support points for the main steel girder 1. This effectively limits the overall settlement of the main steel girder 1 during the subsequent pouring of the middle span concrete, preventing deviations in the bridge deck elevation due to excessive deformation of the middle span. Finally, the negative moment zone at the mid-span is poured. After the side and middle span concretes have reached a certain strength, the solidification shrinkage of the concrete in the negative moment zone allows for fine-tuning of the overall structural alignment, ensuring that the final bridge dimensions meet design requirements and reducing the workload of later alignment corrections.

[0025] In some embodiments, step S2 includes S21: spot welding the bottom formwork 2 of the flat-bottomed composite bridge deck to the middle section of the main steel beam 1, and spot welding the side formwork 3 of the composite structure guardrail to the bottom formwork 2 of the flat-bottomed composite bridge deck. Spot welding eliminates the need for complex welding preparation and full welding operations, enabling rapid initial fixing between components and significantly reducing on-site welding time. The bottom formwork and the side formwork of the guardrail can be quickly assembled into a whole through spot welding, saving preparation time for the subsequent overall hoisting of the main steel beam 1 (step S3) and promoting efficient connection of the construction process.

[0026] In some embodiments, steps S31 and S32 are included after step S3. S31: Check whether the deformation of the flat bottom plate composite bridge deck steel bottom mold 2 exceeds the preset value. If it does not exceed the preset value, continuously weld the flat bottom plate composite bridge deck steel bottom mold 2 to the middle section of the steel main beam 1. If it exceeds the preset value, it needs to be corrected and then continuously welded to the middle section of the steel main beam 1. Specifically, it is necessary to continuously weld the flat bottom plate composite bridge deck steel bottom mold 2 to the upper flange of the steel main beam 1 in the form of a single-sided fillet weld along the length of the steel main beam 1 to ensure that there is no missing weld between the flat bottom plate composite bridge deck steel bottom mold 2 and the upper flange of the steel main beam 1. S32: Check whether the deformation of the steel side mold 3 of the composite structure anti-collision guardrail exceeds the preset value. If it does not exceed the preset value, the steel side mold 3 of the composite structure anti-collision guardrail is continuously welded to the steel bottom mold 2 of the flat bottom plate composite bridge deck. If it exceeds the preset value, it needs to be corrected before the steel side mold 3 of the composite structure anti-collision guardrail is continuously welded to the steel bottom mold 2 of the flat bottom plate composite bridge deck.

[0027] Spot welding provides moderate connection strength, maintaining the relative positions of components while facilitating correction (e.g., mechanical or flame adjustment) when deformation is detected in steps S31 and S32. Direct continuous welding, on the other hand, makes correction extremely difficult once deformation is detected, potentially requiring cutting and re-welding, significantly increasing costs. Furthermore, correcting the deformation before continuous welding ensures connection quality and promotes long-term use.

[0028] In some embodiments, the concrete bridge deck formwork in step S4 includes a support frame and a wooden formwork 7. The support frame is supported on the lower flange of the steel main beam 1, and the wooden formwork 7 is placed on the support frame, with the upper surface of the wooden formwork 7 and the lower surface of the flat-bottom plate combined bridge deck steel bottom formwork 2 at the same horizontal level. The support frame is directly supported on the lower flange of the steel main beam 1. Relying on the high strength characteristics of the steel main beam 1 itself, it avoids the dependence of traditional ground-supported structures on the ground or traffic lines below, making it particularly suitable for scenarios such as crossing traffic or rivers where ground-supported structures cannot be erected, fundamentally eliminating the risk of support frame collapse or settlement. The lower flange of the steel main beam 1 is a standardized load-bearing structure, and the connection between the support frame and the flange can be fixed by bolts or clips. The upper surface of the wooden formwork 7 is flush with the lower surface of the flat-bottom plate combined bridge deck steel bottom formwork 2, which can form a continuous and flat concrete pouring reference surface, ensuring the overall thickness of the bridge deck is uniform and avoiding problems such as concrete surface misalignment and excessive flatness caused by differences in formwork height.

[0029] In some embodiments, in step S5, the first reinforcing mesh 8 is a double-layer reinforcing mesh, and the second reinforcing mesh 9 is a single-layer reinforcing mesh. The double-layer reinforcing mesh includes two layers of longitudinal and transverse reinforcing bars distributed vertically, and the single-layer reinforcing mesh includes one layer of longitudinal and transverse reinforcing bars. The upper layer of longitudinal and transverse reinforcing bars of the first reinforcing mesh 8 and the first layer of longitudinal and transverse reinforcing bars of the second reinforcing mesh 9 are on the same horizontal plane, and the upper layer of longitudinal reinforcing bars of the first reinforcing mesh 8 and the longitudinal reinforcing bars of the second reinforcing mesh 9 are the same steel bar. The double-layer design of the first reinforcing mesh 8 (side span area) can effectively resist the tensile force under the positive bending moment of the side span and avoid concrete cracking. Although the second reinforcing mesh 9 (middle section area) is a single layer, it is coplanar with the upper layer of reinforcing bars of the first reinforcing mesh 8, forming a continuous horizontal reinforcing bar layer, making the entire bridge deck reinforcement system more uniformly stressed and reducing stress concentration. The upper layer of longitudinal reinforcing bars of the first reinforcing mesh 8 and the longitudinal reinforcing bars of the second reinforcing mesh 9 are the same steel bar, which directly eliminates the splicing gap between the side span and the middle section reinforcement, making the longitudinal force transmission more direct and greatly improving the flexural and shear resistance of the bridge deck, especially suitable for bearing the repeated action of vehicle live loads.

[0030] In some embodiments, step S61 is included before step S6: checking for water leakage between the steel bottom formwork 2 of the flat bottom plate composite bridge deck and the upper flange of the steel main beam 1, and between the steel side formwork 3 of the composite structure anti-collision guardrail and the steel bottom formwork 2 of the flat bottom plate composite bridge deck. If leakage is found, it needs to be sealed before pouring concrete; if there is no leakage, concrete can be poured directly. If there are gaps at the joints between the steel bottom formwork and the upper flange of the steel main beam 1, and between the steel side formwork of the guardrail and the steel bottom formwork, concrete grout is prone to seepage during pouring, leading to honeycomb, pitting, or even voids in the local concrete, reducing the structural density. Pre-inspection and sealing can ensure that the concrete is formed in a closed space, ensuring that the strength, impermeability, and other properties meet the design requirements. This construction method is often used for bridge sections that cross traffic lines. If the joints leak, concrete grout may drip onto the road below, affecting the visibility of vehicles and even causing the road surface to become slippery and leading to traffic accidents. Pre-sealing can achieve zero grout leakage construction and avoid interference with traffic below.

[0031] In some embodiments, in step S7, both the first and second crash barrier reinforcement bars include staggered transverse and longitudinal reinforcement bars. Multiple longitudinal reinforcement bars are provided and secured by stirrups 10. Furthermore, the longitudinal reinforcement bars of the first and second crash barrier reinforcement bars are the same single bar. This single longitudinal reinforcement eliminates the gaps found in traditional segmented reinforcement splicing, creating a continuous whole from the side span to the middle section of the barrier. This makes it less prone to disintegration under lateral impact and enhances its resistance to deformation. The shared longitudinal reinforcement eliminates the need for lapping or welding at the junction of the first and second crash barrier reinforcement bars, reducing labor costs associated with bar cutting and splicing, and avoiding structural hazards caused by insufficient lap length or poor welding quality.

[0032] In some embodiments, the anti-collision guardrail casting template in step S8 is a standardized steel template, and the inner surface of the anti-collision guardrail casting template is at the same level as the outer surface of the composite structure anti-collision guardrail steel side mold 3. The inner surface of the template is flush with the outer surface of the composite structure anti-collision guardrail steel side mold 3, forming a continuous and flat casting reference surface. This allows for precise control of the guardrail cross-sectional dimensions (such as height and thickness) to meet design requirements, avoiding uneven stress on the guardrail caused by differences in template height, and ensuring the structural load-bearing performance.

[0033] In some embodiments, step S3 employs an integral jacking construction method. Specifically, the steel main beam 1 is assembled on an assembly platform 5, which is located on one side of the bridge section to be constructed. The end of the steel main beam 1 is connected to a guide beam 6. The steel main beam 1 is pushed from the assembly platform 5 until it is stably supported on the pier. Integral jacking eliminates the need for ground-mounted scaffolding under the bridge section to be constructed, making it particularly suitable for bridge sections crossing busy traffic routes, rivers, or existing buildings. This fundamentally avoids problems such as traffic disruptions and navigation obstruction caused by scaffolding occupying the space below. The jacking process relies on the reaction force provided by the abutments or temporary piers on both sides, eliminating the need for leveling or reinforcing the site below. This significantly reduces the need for modifications to the surrounding environment, making it particularly suitable for construction scenarios with narrow sites or poor geological conditions (such as soft soil foundations). The core operations of integral jacking (component assembly and jacking) are mainly carried out on one side of the bridge site. The impact on the traffic below is limited to temporary monitoring during the jacking process (no need for long-term road closures). Typically, a single jacking operation can be completed within a few days, significantly reducing the time spent on road occupancy compared to the scaffolding method.

[0034] In some embodiments, the steel bottom formwork 2 of the flat-bottomed composite bridge deck is connected to the middle section of the steel main beam 1 by stiffening ribs (PBL stiffening ribs). Weld studs 4 are vertically welded to the upper flange of the steel main beam 1, directly resisting the relative slippage between the steel main beam and the concrete bridge deck, efficiently transferring the vertical load and horizontal shear force of the bridge deck concrete to the steel main beam 1, avoiding localized voids or structural deformation due to connection failure. The stiffening ribs increase the stiffness of the connection node between the steel bottom formwork and the steel main beam 1, dispersing the concentrated stress borne by the weld studs 4, making shear force transmission more uniform, especially under repeated vehicle live loads, reducing the risk of fatigue failure of the weld studs 4. The stiffening ribs, through welding or bolting, form a three-dimensional support system with the steel main beam 1 and the steel bottom formwork, significantly improving the bending stiffness of the steel bottom formwork and reducing its deflection deformation during concrete pouring and subsequent operation. Welding studs 4 and stiffening ribs serve as auxiliary means for welding connections, providing multiple safeguards: if the welded joint has minor defects due to construction errors, welding studs 4 can temporarily bear part of the shear force, while stiffening ribs can limit the stress diffusion in the defective area. The three work together to ensure a more reliable and robust connection.

[0035] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for constructing a combined bridge, characterized in that: Includes the following steps S1: Assembled steel main beam; S2: Fix the flat bottom plate composite bridge deck steel bottom formwork to the middle section of the assembled steel main beam, and the span of the flat bottom plate composite bridge deck steel bottom formwork is not less than the span of the traffic line under the bridge section to be constructed. Fix the composite structure anti-collision guardrail steel side formwork to the flat bottom plate composite bridge deck steel bottom formwork. S3: The assembled steel main beam, together with the flat bottom plate composite bridge deck steel bottom formwork and the composite structure anti-collision guardrail steel side formwork, is installed on the bridge section to be constructed. S4: Install concrete bridge deck formwork on the main steel beams on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck; S5: The first steel mesh is laid in the concrete bridge deck formwork on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck, and the second steel mesh is laid in the steel bottom formwork of the flat bottom plate composite bridge deck. S6: Pour the positive bending moment area on both sides of the steel bottom formwork of the flat bottom plate composite bridge deck, then pour the positive bending moment area at the steel bottom formwork of the flat bottom plate composite bridge deck, and finally pour the negative bending moment area at the steel bottom formwork of the flat bottom plate composite bridge deck. S7: Lay out the first anti-collision guardrail reinforcement on both sides of the side span of the flat bottom plate composite bridge deck steel bottom formwork and the second anti-collision guardrail reinforcement on the composite structure anti-collision guardrail side formwork; S8: Install the anti-collision guardrail casting formwork outside the first anti-collision guardrail reinforcement; S9: Pour concrete for the first and second crash barriers; S10: Construction asphalt pavement layer.

2. The construction method for combined bridges according to claim 1, characterized in that: Step S2 includes S21: The steel bottom formwork of the flat bottom plate composite bridge deck is spot-welded to the middle section of the steel main beam, and the steel side formwork of the composite structure anti-collision guardrail is spot-welded to the steel bottom formwork of the flat bottom plate composite bridge deck.

3. The construction method for combined bridges according to claim 2, characterized in that: Steps S31 and S32 are included after step S3. S31: Check whether the deformation of the flat bottom plate composite bridge deck steel bottom formwork exceeds the preset value. If it does not exceed the preset value, then continuously weld the flat bottom plate composite bridge deck steel bottom formwork to the middle section of the steel main beam. If it exceeds the preset value, then after correction, continuously weld the flat bottom plate composite bridge deck steel bottom formwork to the middle section of the steel main beam. S32: Check whether the deformation of the steel side mold of the composite structure anti-collision guardrail exceeds the preset value. If it does not exceed the preset value, the steel side mold of the composite structure anti-collision guardrail is continuously welded to the steel bottom mold of the flat bottom plate composite bridge deck. If it exceeds the preset value, it needs to be corrected before the steel side mold of the composite structure anti-collision guardrail is continuously welded to the steel bottom mold of the flat bottom plate composite bridge deck.

4. The construction method for combined bridges according to claim 1, characterized in that: In step S4, the concrete bridge deck formwork includes a support and a wooden formwork. The support is supported on the lower flange of the steel main beam, and the wooden formwork is placed on the support. The upper surface of the wooden formwork is on the same horizontal line as the lower surface of the flat bottom plate combined bridge deck steel bottom formwork.

5. The construction method for combined bridges according to claim 1, characterized in that: In step S5, the first steel mesh is a double-layer steel mesh, and the second steel mesh is a single-layer steel mesh. The double-layer steel mesh includes two layers of longitudinal and transverse steel bars distributed vertically, and the single-layer steel mesh includes one layer of longitudinal and transverse steel bars. The longitudinal and transverse steel bars on the upper layer of the first steel mesh and the first layer of longitudinal and transverse steel bars of the second steel mesh are on the same horizontal plane, and the longitudinal steel bars on the upper layer of the first steel mesh and the longitudinal steel bars of the second steel mesh are the same steel bars.

6. The construction method for combined bridges according to claim 1, characterized in that: Step S61 is included before step S6. S61: Check for water leakage between the steel bottom formwork of the flat bottom plate composite bridge deck and the upper flange of the steel main beam, and between the steel side formwork of the composite structure anti-collision guardrail and the steel bottom formwork of the flat bottom plate composite bridge deck. If there is water leakage, it needs to be sealed before pouring concrete; if there is no water leakage, pour concrete directly.

7. The construction method for combined bridges according to claim 1, characterized in that: In step S7, both the first and second crash barrier reinforcing bars include staggered transverse and longitudinal reinforcing bars, and the longitudinal reinforcing bars of the first and second crash barrier reinforcing bars are the same reinforcing bars.

8. The construction method for combined bridges according to claim 1, characterized in that: In step S8, the anti-collision guardrail casting template is a fixed steel template, and the inner surface of the anti-collision guardrail casting template is at the same level as the outer surface of the steel side mold of the combined structure anti-collision guardrail.

9. The construction method for combined bridges according to claim 1, characterized in that: Step S3 adopts the construction method of integral jacking.

10. The construction method for a combined bridge according to claim 3, characterized in that: The steel bottom formwork of the flat bottom plate composite bridge deck is also connected to the middle section of the steel main beam by stiffening ribs.

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