Prefabricated beam bridge upper portion widening construction method based on steel structure bent cap

Abstract

The invention discloses a prefabricated beam bridge upper portion widening construction method based on a steel structure bent cap, belongs to the technical field of bridge engineering construction, is suitable for reconstruction and extension of existing prefabricated T-beam or small box beam bridges, and is particularly suitable for road sections with limited transverse under-bridge space or difficult characterization and disassembly. The method comprises the following steps: preprocessing an existing structure; an extension supporting structure is constructed; erecting a newly-added upper structure; connecting new and old structures; constructing a bridge deck system; and constructing guardrails and accessory structures. The method does not need to add abutments, adopts prefabricated construction, can solve the problems of limited space or difficult characterization and disassembly, improves the construction efficiency and bridge integrity, and is suitable for highway reconstruction and extension.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge engineering construction, and specifically relates to a method for widening the upper part of an existing prefabricated T-beam or prefabricated small box beam bridge on an expressway based on a steel structure cap beam. The method is particularly suitable for bridge renovation and expansion projects in sections with limited transverse space under the bridge or where demolition and requisition are difficult. The method aims to achieve efficient renovation and expansion of the bridge without erecting piers under the bridge by widening the upper structure through assembled construction. Background Art

[0002] With the continuous growth of highway traffic, existing two-way four-lane highways urgently need to be upgraded to two-way six-lane highways through reconstruction and expansion to improve traffic capacity. Bridge widening is a key step in this reconstruction and expansion project. Currently, the superstructures of domestic highway bridges mostly use prefabricated T-beams or prefabricated small box beams. The conventional widening construction method requires the installation of pier foundations on the widening side. The pier construction is completed through processes such as foundation excavation, steel bar binding, and concrete pouring. The new superstructure is then erected. There are three specific methods: 1. Construction in which the superstructure and substructure are not connected; 2. Construction in which the superstructure is connected but the substructure is not; and 3. Construction in which both the superstructure and substructure are connected.

[0003] However, in actual construction, some bridge sections have limited transverse underpass space due to crossing rivers and roads. This makes it difficult to maintain the space required for excavation and formwork support for pier foundation construction, making conventional construction methods difficult to implement. Furthermore, land acquisition and demolition are difficult on some sections, and the land acquisition required for new pier foundations would significantly increase project costs and duration. Furthermore, existing widening construction methods for prefabricated T-beam or prefabricated small box girder bridges lack a systematic construction method that "widens the upper structure without erecting piers below." Conventional methods rely on on-site casting of new piers, resulting in low construction efficiency and significant impact on existing traffic. Furthermore, these methods struggle to adapt to the industry trend toward prefabricated construction, becoming a bottleneck restricting the renovation and expansion of sections with limited transverse underpass space or where land acquisition and demolition are difficult.

[0004] Therefore, there is an urgent need for a construction method for widening the upper part of prefabricated T-beams or prefabricated small box beam bridges. By optimizing the construction process, prefabricated construction without the need for new pier foundations can be achieved, so as to solve the implementation difficulties of conventional methods in sections with limited space or difficult demolition and relocation, and improve the efficiency and economy of bridge reconstruction and expansion. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to overcome the limitations of the existing prefabricated T-beam or prefabricated small box beam bridge widening construction method that relies on the addition of new pier foundations, and to provide a prefabricated beam bridge upper widening construction method based on a steel structure cap beam to solve the problem that the pier foundation construction is difficult to implement in sections where the horizontal space under the bridge is limited or where demolition and requisition are difficult; by adopting assembly construction, prefabricated steel components in the factory and quick connection on site, on-site pouring operations are reduced, construction efficiency is improved, construction period is shortened, and the impact on existing traffic and the surrounding environment is reduced; ensuring that the new and old structures are reliably connected through steel diaphragms and wet joints, improving the overall stress performance and stability of the bridge after widening, and meeting the traffic needs of expanding a two-way four-lane road to a two-way six-lane road; at the same time, through intensive construction (such as using a 1.5-meter hard shoulder and giving priority to setting up emergency parking lanes in the roadbed section), land occupation is reduced, project costs are reduced, and the requirements of green and efficient bridge renovation and expansion are met.

[0006] In order to achieve the above object, the present invention provides a method for widening the upper portion of a prefabricated beam bridge based on a steel structure cap beam, comprising the following steps:

[0007] (1) Pretreatment of existing structures

[0008] Chisel away the outer guardrails and part of the cantilever of the existing bridge, clean the chiseled area, roughen the outer connection surface of the existing cap beam, and tidy up the exposed steel bars at the edge of the existing bridge deck;

[0009] (2) Construction of external support structure

[0010] Hoist the prefabricated steel structure cap beam to the preset position outside the existing cap beam, lay rubber pads at the connection, and fix the steel structure cap beam to the existing cap beam through connectors to form a support platform;

[0011] (3) New superstructure erection

[0012] Hoist the prefabricated steel-concrete composite beams onto the supporting platform, ensuring that their spans are consistent with those of the existing bridge;

[0013] (4) Construction of connection between new and old structures

[0014] Connect the new superstructure to the existing main beams using steel diaphragms and wet joints;

[0015] (5) Bridge deck system construction

[0016] A bridge deck system is provided at the connection area between the new superstructure and the existing bridge deck and on the top of the new superstructure;

[0017] (6) Construction of guardrails and auxiliary structures

[0018] A guardrail structure is set up on the outside of the newly added superstructure, and emergency parking lanes are set up at intervals along the longitudinal direction of the bridge. The emergency parking lanes are preferably set up in the roadbed section.

[0019] Furthermore, in step (2), the connecting member is an anchor bolt, which is spaced apart longitudinally along the existing cap beam, with one end implanted inside the existing cap beam and the other end fixedly connected to the steel structure cap beam.

[0020] Furthermore, in step (3), the steel-concrete composite beam includes a steel main beam and a prefabricated bridge deck, and the prefabricated bridge deck is covered on the top of the steel main beam and fixedly connected when prefabricated in the factory.

[0021] Furthermore, in step (4), the steel diaphragms are arranged at intervals along the longitudinal direction of the bridge, and their number and positions correspond one-to-one to the diaphragms between the existing bridge beams, and the two ends of the steel diaphragms are fixedly connected to the newly added superstructure and the existing main beam respectively.

[0022] Furthermore, in step (4), connecting steel bars are provided in the wet joint, and the two ends of the connecting steel bars are respectively connected to the exposed steel bars of the existing bridge deck and the exposed steel bars of the bridge deck of the newly added superstructure, and the wet joint is cast with concrete.

[0023] Furthermore, in step (6), the guardrail structure is a steel guardrail, and its anti-collision level is consistent with the outer guardrail of the existing bridge, and the steel guardrail is fixedly connected to the newly added superstructure through embedded parts.

[0024] Furthermore, in step (2), the rubber pads are arranged at intervals along the longitudinal direction of the connection between the steel structure cap beam and the existing cap beam; in step (5), the bridge deck system includes a leveling layer, a waterproof layer and an asphalt pavement layer, the leveling layer covers the wet joint and the top of the newly added superstructure, the waterproof layer is arranged above the leveling layer, and the asphalt pavement layer is arranged above the waterproof layer.

[0025] The present invention adopts the above technical solution, which has at least the following beneficial effects:

[0026] 1. The present invention adopts the construction scheme of "widening the upper part and not erecting piers under the bridge". It uses a steel structure cap beam to extend the existing cap beam to form a support platform, eliminating the need for adding pier foundations on the widening side. This effectively solves the problem of widening bridges in areas with limited space under the bridge (such as crossing rivers or roads) or in sections where land acquisition and demolition are difficult. It breaks through the limitation of conventional methods that rely on pier construction, allowing the reconstruction and expansion of such sections to proceed smoothly.

[0027] 2. Use factory-prefabricated steel structure cap beams, steel-concrete composite beams (including steel main beams and prefabricated bridge panels), steel cross diaphragms and other components, and quickly install them on site through hoisting, anchor bolt fixing, welding and other methods to achieve assembly construction, greatly reduce the amount of on-site pouring work, shorten the construction period, reduce interference with existing traffic and the impact on the surrounding environment, and avoid temporary land occupation of the new beam yard, in line with green construction requirements.

[0028] 3. The new and old structures are connected by steel diaphragms (the number and position of which correspond to the diaphragms between existing beams) and wet joints. The steel diaphragms ensure the coordinated transmission of lateral forces, and the wet joints form a rigid whole by connecting steel bars, which significantly improves the overall load-bearing performance and structural stability of the bridge after widening, ensuring driving safety.

[0029] 4. Adopt intensive construction design (such as 1.5-meter outer hard shoulder and emergency parking lanes preferentially located in the roadbed section), and use steel guardrails to replace traditional concrete guardrails to reduce deadweight. On the premise of meeting regulatory requirements, it can reduce land occupation and demolition costs, lower project costs, and at the same time reduce building material consumption and carbon emissions, adapting to the green and efficient needs of highway reconstruction and expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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 these drawings without paying any creative work.

[0031] Figure 1 This is a flow chart of the widening construction method for the upper portion of a prefabricated beam bridge according to the present invention;

[0032] Figure 2 It is a schematic diagram of the cross section of an existing T-beam bridge;

[0033] Figure 3 This is a schematic diagram of the expanded cross section of a T-beam bridge according to the present invention;

[0034] Figure 4 This is one of the large pattern drawings of the upper structure of the present invention;

[0035] Figure 5 This is the second large pattern drawing of the upper structure of the present invention;

[0036] Figure 6 It is a schematic diagram of the arrangement of the steel diaphragm of the present invention;

[0037] Figure 7 The steel cap beam structure of the present invention Figure 1 ;

[0038] Figure 8 The steel cap beam structure of the present invention Figure 2 ;

[0039] Figure 9 It is a schematic diagram of the expanded cross section of the small box girder bridge of the present invention.

[0040] In the figure: 1. Existing cap beam; 2. Steel structure cap beam; 3. Existing main beam; 4. Existing bridge deck; 5. Steel-concrete composite beam; 6. Steel main beam; 7. Precast bridge deck; 8. Steel diaphragm; 9. Wet joint; 10. Rubber pad; 11. Guardrail structure. DETAILED DESCRIPTION

[0041] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present invention, as detailed in the appended claims.

[0042] Example 1

[0043] like Figure 1 As shown, the present invention provides a method for widening the upper part of a prefabricated beam bridge based on a steel structure cap beam, comprising the following steps:

[0044] (1) Pretreatment of existing structures

[0045] Chisel away the outer guardrails and part of the cantilever of the existing bridge, clean the chiseled area, roughen the outer connection surface of the existing cap beam, and tidy up the exposed steel bars at the edge of the existing bridge deck;

[0046] (2) Construction of external support structure

[0047] Hoist the prefabricated steel structure cap beam to the preset position outside the existing cap beam, lay rubber pads at the connection, and fix the steel structure cap beam to the existing cap beam through connectors to form a support platform;

[0048] (3) New superstructure erection

[0049] Hoist the prefabricated steel-concrete composite beams onto the supporting platform, ensuring that their spans are consistent with those of the existing bridge;

[0050] (4) Construction of connection between new and old structures

[0051] Connect the new superstructure to the existing main beams using steel diaphragms and wet joints;

[0052] (5) Bridge deck system construction

[0053] A bridge deck system is provided at the connection area between the new superstructure and the existing bridge deck and on the top of the new superstructure;

[0054] (6) Construction of guardrails and auxiliary structures

[0055] A guardrail structure is set up on the outside of the newly added superstructure, and emergency parking lanes are set up at intervals along the longitudinal direction of the bridge. The emergency parking lanes are preferably set up in the roadbed section.

[0056] As an implementation method, in step (2) of this embodiment, the connecting member is an anchor bolt, which is distributed at intervals along the longitudinal direction of the existing cap beam, with one end implanted inside the existing cap beam and the other end fixedly connected to the steel structure cap beam.

[0057] As an implementation mode, in step (3) of this embodiment, the steel-concrete composite beam includes a steel main beam and a prefabricated bridge deck, and the prefabricated bridge deck is covered on the top of the steel main beam and fixedly connected when prefabricated in the factory.

[0058] As an implementation method, in step (4) of this embodiment, the steel diaphragms are arranged at intervals along the longitudinal direction of the bridge, and their number and position correspond one-to-one to the diaphragms between the existing bridge beams, and the two ends of the steel diaphragms are fixedly connected to the newly added superstructure and the existing main beam respectively.

[0059] As an implementation method, in step (4) of this embodiment, connecting steel bars are provided in the wet joint, and the two ends of the connecting steel bars are respectively connected to the exposed steel bars of the existing bridge deck and the exposed steel bars of the bridge deck of the newly added superstructure, and the wet joint is cast with concrete.

[0060] As an implementation method, in step (6) of this embodiment, the guardrail structure is a steel guardrail, and its anti-collision level is consistent with the outer guardrail of the existing bridge, and the steel guardrail is fixedly connected to the newly added superstructure through embedded parts.

[0061] As an implementation method, in step (2) of this embodiment, the rubber pads are arranged at intervals along the longitudinal direction of the connection between the steel structure cap beam and the existing cap beam; in step (5), the bridge deck system includes a leveling layer, a waterproof layer and an asphalt pavement layer, the leveling layer covers the wet joints and the top of the newly added superstructure, the waterproof layer is arranged above the leveling layer, and the asphalt pavement layer is arranged above the waterproof layer.

[0062] Through the above steps, this embodiment realizes the upper widening construction of the prefabricated beam bridge. The entire process adopts the assembly operation of factory prefabricated components, without the need for new piers. It is suitable for sections with limited lateral space or difficult land acquisition and demolition, and takes into account both structural integrity and construction economy.

[0063] Example 1

[0064] See also Figures 2 to 9 As shown, this embodiment provides a bridge upper widening structure based on a steel structure cap beam, including an existing bridge structure, an extended support structure, a new upper structure, a connection component, a bridge deck system and a guardrail structure 11;

[0065] The existing bridge structure includes an existing cap beam 1, an existing main beam 3 and an existing bridge deck 4, wherein the existing main beam 3 is a prefabricated T beam or a prefabricated small box beam;

[0066] The extended support structure is a steel structure cap beam 2 extending along the outside of the existing cap beam 1, which is fixedly connected to the existing cap beam 1 through a connecting piece to form an outward-extending support platform;

[0067] The newly added superstructure is arranged on the support platform of the extended support structure, and its span is consistent with the span of the existing bridge structure. The newly added superstructure is connected to the existing main beam 3 through a connecting assembly;

[0068] The outer guardrail and part of the cantilever of the existing bridge structure are chiseled out, and the guardrail structure 11 is provided at the outer edge of the newly added superstructure;

[0069] The bridge deck system covers the connection area between the newly added superstructure and the existing bridge deck 4 and the top of the newly added superstructure.

[0070] The connecting member in this embodiment is an anchor bolt, which is distributed at intervals along the longitudinal direction of the existing cap beam 1, with one end implanted inside the existing cap beam 1 and the other end fixedly connected to the steel structure cap beam 2.

[0071] As an implementation method, the newly added superstructure in this embodiment is a steel-concrete composite beam 5, including a steel main beam 6 and a prefabricated bridge deck 7, and the prefabricated bridge deck 7 covers the top of the steel main beam 6 and is fixedly connected.

[0072] The connection components described in this embodiment include steel diaphragms 8 and wet joints 9; the steel diaphragms 8 are arranged at intervals along the longitudinal direction of the bridge, and their number and position correspond one-to-one to the diaphragms between the beams in the existing bridge structure. The two ends of the steel diaphragms 8 are respectively fixedly connected to the newly added superstructure and the existing main beam 3; the wet joints 9 are provided between the bridge deck of the newly added superstructure and the existing bridge deck 4, connecting the two into a whole.

[0073] In this embodiment, connecting steel bars are provided in the wet joint 9 , and the two ends of the connecting steel bars are respectively connected to the exposed steel bars of the existing bridge deck 4 and the exposed steel bars of the bridge deck of the newly added superstructure. The wet joint 9 is cast with concrete.

[0074] The guardrail structure 11 in this embodiment is a steel guardrail, and its anti-collision level is consistent with the outer guardrail of the existing bridge structure. The steel guardrail is fixedly connected to the newly added superstructure through embedded parts.

[0075] The bridge deck system in this embodiment includes a leveling layer, a waterproof layer and an asphalt pavement layer. The leveling layer covers the wet joint 9 and the top of the newly added superstructure, the waterproof layer is arranged above the leveling layer, and the asphalt pavement layer is arranged above the waterproof layer.

[0076] In this embodiment, rubber pads 10 are provided at the connection between the steel structure cap beam 2 and the existing cap beam 1 , and the rubber pads 10 are arranged at intervals along the longitudinal direction of the connection.

[0077] In this embodiment, emergency parking strips are provided at predetermined intervals along the longitudinal direction of the bridge, and the emergency parking strips are preferably provided on the roadbed section.

[0078] Working principle description:

[0079] Figure 2 This is a schematic diagram of the cross section of an existing T-beam bridge. Figure 3 This is a schematic diagram of the cross-section of a T-beam bridge expansion according to the present invention. The working principle of the bridge upper widening structure based on the steel structure cap beam revolves around the core design of "upper widening without piers under the bridge". Through the coordinated action of various components, it can achieve efficient widening of existing bridges (prefabricated T-beams or small box beams). The details are as follows:

[0080] 1. Force transfer within the support system: The extended support structure (steel cap beam) is secured to the existing cap beam via connectors (anchor bolts), forming an outward-extending support platform. Rubber pads are installed at the connection between the extended support structure and the existing cap beam to buffer local stresses caused by material differences or deformation. The load (including deadweight and vehicle loads) of the newly added superstructure (steel-concrete composite beam) is transferred to the existing cap beam via the steel cap beam, and then from the existing cap beam to the original lower pier foundation. This eliminates the need for new piers, solving the problem of limited transverse underbridge space or the inability to install new piers in sections where demolition and requisition are difficult.

[0081] 2. Ensure the integrity of the new and old structures: The newly added superstructure and the existing main beams form an integral force-bearing system through connection components: Steel diaphragms are arranged at intervals along the longitudinal direction and their positions correspond one-to-one with the diaphragms between the existing bridge beams, which can synchronously transmit lateral forces and avoid relative displacement of the new and old structures due to uncoordinated forces; the connecting steel bars in the wet joints connect the steel bars of the existing bridge deck and the new bridge deck into a whole, forming a rigid connection after concrete pouring, ensuring that the bridge deck load is evenly transferred between the new and old structures, and improving the overall stiffness and deformation resistance of the bridge after widening.

[0082] 3. Functional Adaptation and Safety Assurance: The existing bridge's outer guardrails and a portion of the cantilever were removed to create space for the connection between the new and old structures. A new guardrail structure (steel guardrail) was fixed to the outside of the new superstructure, meeting crashworthiness requirements while reducing deadweight and the load on the supporting platform. The bridge deck system covers the connection area and the top of the new superstructure. A leveling layer, waterproofing layer, and asphalt pavement layer were sequentially installed to ensure a smooth, waterproof bridge deck and smooth driving. Combined with a pre-defined emergency stop strip along the longitudinal direction (preferably located on the roadbed), the bridge is adapted to the functional requirements of a six-lane, two-way traffic system.

[0083] Through the synergistic effect of the above-mentioned components, the structure achieves the widening of the upper part of the bridge without adding new piers, taking into account structural safety, construction feasibility and functional adaptability. It is suitable for sections with limited lateral space under the bridge or difficult expropriation and demolition.

[0084] Example 2

[0085] like Figures 1 to 8 As shown, for the bridge widening scenario where the existing main beam is a prefabricated T-beam (30m span), based on the working principle of Example 1 and combined with the structural characteristics of the 30m span T-beam, its adaptability working principle is as follows:

[0086] 1. Support and load transfer adaptation: The 30m span T-beam has a large deadweight, and the steel structure cap beam extension part is based on Figure 7 and Figure 8 The "Steel Cap Beam Structure Diagram (Applicable to 30m T-Beam)" design connects to the existing cap beam through M24 anchor bolts (the anchor bolt implantation depth and spacing match the T-beam load distribution). Rubber pads (200×200×20mm) are arranged at intervals along the connection to buffer the vibration load when the T-beam is under stress, ensuring that the load is stably transferred to the existing cap beam.

[0087] 2. Transverse force transmission adaptation: The T-beam web is thick and the transverse force is concentrated. The steel diaphragm is connected to the T-beam web by high-strength bolts and welded to the steel main beam of the newly added steel-concrete composite beam. It can efficiently transmit the transverse shear force generated by vehicle loads. The number of diaphragms corresponds one-to-one with the transverse diaphragms between the existing T-beam beams ( Figure 6 (as shown) to avoid cracks at the joints of new and old structures due to concentrated force.

[0088] 3. Bridge deck connection adaptation: After the outer cantilever of the T beam is chiseled out ( Figure 4 and Figure 5 ), the wet joint width is adapted to the remaining cantilever size, and the internal connecting steel bars are welded to the exposed steel bars of the T-beam flange plate. After being poured with C50 concrete, a rigid transition is formed to ensure that the vehicle load is smoothly transferred from the new bridge deck to the existing T-beam bridge deck, which is adapted to the stress characteristics of the T-beam flange plate.

[0089] Example 3

[0090] See Figures 1 to 8 , combined with Figure 9 For the bridge widening scenario where the existing main beam is a prefabricated small box beam (30m span), based on the working principle of Example 1 and combined with the structural characteristics of the 30m span small box beam, its adaptability working principle is as follows:

[0091] 1. Support and load transfer adaptation: The small box beam is evenly distributed in the horizontal direction, and the steel structure cap beam extension part is based on the attached Figure 7 and Figure 8The "(applicable to 30m small box girders)" design has an anchor bolt spacing that adapts to the load distribution characteristics of small box girders. The rubber pads (200×200×20mm) can cushion the overall deformation of the small box girder when it is loaded, ensuring that the load of the newly added superstructure is evenly transferred to the existing cap beam.

[0092] 2. Transverse force transmission adaptation: The top plate of the small box beam is relatively wide, and the steel diaphragm is connected to the outer web of the small box beam through embedded bolts ( Figure 6 ), welded with the steel main beam of the newly added steel-concrete composite beam, can adapt to the characteristics of the small box beam with dispersed lateral force, ensuring that the new and old structures can coordinately bear the lateral load.

[0093] 3. Bridge deck connection adaptation: After the outer cantilever of the small box beam is removed ( Figure 3 and Figure 4 ), the wet joint width is adapted to the cantilever size of the top plate, the connecting steel bars are mechanically connected to the exposed distributed steel bars of the small box girder top plate, and a smooth transition is formed after concrete pouring, which is adapted to the width of the small box girder top plate and the uniform load distribution, ensuring smooth driving on the bridge deck.

[0094] T beam diagram ( Figures 3 to 8 ) and the diagram of the small box girder ( Figure 9 ) is that the beam types are different, one is a T-beam and the other is a small box beam, but the width scheme is the same.

[0095] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for widening the upper portion of a prefabricated beam bridge based on a steel cap beam, characterized by: The following steps are involved: (1) Pretreatment of existing structures Chisel away the outer guardrails and part of the cantilever of the existing bridge, clean the chiseled area, roughen the outer connection surface of the existing cap beam, and tidy up the exposed steel bars at the edge of the existing bridge deck; (2) Construction of external support structure Hoist the prefabricated steel structure cap beam to the preset position outside the existing cap beam, lay rubber pads at the connection, and fix the steel structure cap beam to the existing cap beam through connectors to form a support platform; (3) New superstructure erection Hoist the prefabricated steel-concrete composite beams onto the supporting platform, ensuring that their spans are consistent with those of the existing bridge; (4) Construction of connection between new and old structures Connect the new superstructure to the existing main beams using steel diaphragms and wet joints; (5) Bridge deck system construction A bridge deck system is provided at the connection area between the new superstructure and the existing bridge deck and on the top of the new superstructure; (6) Construction of guardrails and auxiliary structures A guardrail structure is set up on the outside of the newly added superstructure, and emergency parking lanes are set up at intervals along the longitudinal direction of the bridge. The emergency parking lanes are preferably set up in the roadbed section.

2. The method according to claim 1, wherein: In step (2), the connecting member is an anchor bolt, which is distributed at intervals along the longitudinal direction of the existing cap beam, one end of which is implanted inside the existing cap beam, and the other end of which is fixedly connected to the steel structure cap beam.

3. The method according to claim 1, wherein: In step (3), the steel-concrete composite beam includes a steel main beam and a prefabricated bridge deck, and the prefabricated bridge deck is covered on the top of the steel main beam and fixedly connected when prefabricated in the factory.

4. The method according to claim 1, wherein: In step (4), the steel diaphragms are arranged at intervals along the longitudinal direction of the bridge, and their number and position correspond one-to-one to the diaphragms between the existing bridge beams. The two ends of the steel diaphragms are fixedly connected to the newly added superstructure and the existing main beam respectively.

5. The method according to claim 1, wherein: In step (4), connecting steel bars are provided in the wet joint, and the two ends of the connecting steel bars are respectively connected to the exposed steel bars of the existing bridge deck and the exposed steel bars of the bridge deck of the newly added superstructure, and the wet joint is cast with concrete.

6. The method according to claim 1, wherein: In step (6), the guardrail structure is a steel guardrail, and its anti-collision level is consistent with the outer guardrail of the existing bridge. The steel guardrail is fixedly connected to the newly added superstructure through embedded parts.

7. The method according to claim 1, wherein: In step (2), the rubber pads are arranged at intervals along the longitudinal direction of the connection between the steel structure cap beam and the existing cap beam; in step (5), the bridge deck system includes a leveling layer, a waterproof layer and an asphalt pavement layer, the leveling layer covers the wet joint and the top of the newly added superstructure, the waterproof layer is arranged above the leveling layer, and the asphalt pavement layer is arranged above the waterproof layer.

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