A main arch and stiff skeleton-steel pipe concrete arch bridge

Abstract

The present application relates to a kind of main arch and stiff skeleton-concrete filled steel tube arch bridge.Main arch, including four main pipes, several arches in the cross-link and several abdominal links, wherein two main pipes are located in upper chord, and the other two main pipes are located in lower chord, four main pipes are connected to form skeleton by the arch in the cross-link and the abdominal link, and four main pipes are filled with concrete, and main arch longitudinally includes first main arch section located at its two ends and second main arch section located at its longitudinal middle part, the skeleton of the first main arch section is wrapped with reinforced concrete to form box structure, and the box structure includes top plate, bottom plate and two side webs.The skeleton of the first main arch section at the longitudinal ends of main arch is wrapped with reinforced concrete to form box structure, so that the load-carrying capacity of the first main arch section is strengthened, effectively solving the stress problem of large arch foot segment main arch axial force, achieving the purpose of reducing the size of main pipe, so that the weight of arch rib section is lighter, the installation system is more economical, and the installation process is safer.

Description

Technical Field

[0001] This invention relates to the field of arch bridge technology, and in particular to a main arch and stiffening frame – a steel-concrete composite arch bridge. Background Technology

[0002] As my country's highway construction extends into the western mountainous regions, an increasing number of long-span bridges are being used to cross mountain valleys. Among these, steel-concrete composite arch bridges, with their economic advantages, high load-bearing capacity, and strong spanning ability, are highly competitive. However, transportation conditions in mountainous areas of my country, especially in the southwest, are relatively underdeveloped. Constructing long-span steel-concrete composite arch bridges will face stringent construction, transportation, and installation conditions, limiting the transportation and installation of steel structures. Therefore, there is an urgent need to develop a new type of steel-concrete composite arch bridge structure suitable for mountainous conditions.

[0003] Existing steel-concrete composite arch bridges typically employ single-tube, dumbbell-shaped, or truss-type steel-concrete composite structures for their main arches. To meet the load-bearing requirements of arch bridges in mountainous areas, the main pipe dimensions of these types of main arches must be sufficiently large to ensure the structural integrity of the arch. For existing truss-type steel-concrete composite arch bridges, the appropriate dimensions of the main pipe must be determined based on the span requirements. When the span exceeds 300m, the main pipe diameter and the total width of the arch ribs exceed 1000mm and 4500mm respectively. The arch rib segment dimensions exceed the transportation capacity of mountainous areas, necessitating the use of time-consuming and labor-intensive single-tube transport of the main pipe. This reduces construction efficiency, increases the construction period, raises construction risks, and increases construction costs. Summary of the Invention

[0004] The purpose of this invention is to address the problems of existing truss-type steel-concrete composite arch bridges, where the main pipe diameter is large, resulting in a large total width of the arch ribs and the arch rib segment dimensions exceeding the transportation capacity of mountainous areas. This necessitates the use of time-consuming and labor-intensive single-pipe transportation, leading to reduced construction efficiency, increased construction period, higher construction risks, and increased construction costs. The invention provides a main arch and stiffening frame-steel-concrete composite arch bridge.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A main arch includes four main pipes, several inner arch cross braces, and several web braces. Two of the main pipes are located on the upper chord, and the other two are located on the lower chord. The four main pipes are connected by the inner arch cross braces and the web braces to form a skeleton. Each of the four main pipes is filled with concrete. The main arch longitudinally includes a first main arch section located at both ends and a second main arch section located in the middle of its longitudinal direction. The skeleton of the first main arch section is encased in reinforced concrete to form a box structure. The box structure includes a top plate, a bottom plate, and web plates on both sides.

[0007] In this design, all four main pipes are filled with concrete. The four main pipes, several transverse braces within the arch, and several web braces combine to form a skeleton structure. The cross-sectional shape of the skeleton structure can be selected according to requirements. The second main arch segment in the longitudinal middle of the main arch is a truss-type steel-concrete composite structure. The two ends of the main arch in the longitudinal direction are the first main arch segments. The skeleton of the first main arch segment is encased in reinforced concrete to form a box structure with a top plate, bottom plate, and webs on both sides. This strengthens the load-bearing capacity of the first main arch segment and effectively solves the problem of high axial force in the arch foot section, thereby optimizing the dimensions of the main arch pipes. For arch bridges with a span exceeding 300m, this design can reduce the main pipe dimensions by more than 20% while maintaining the structural safety of the main arch. The width of the arch rib segment, i.e., the maximum width of the skeleton, is reduced to 3000mm, which meets transportation requirements and solves the transportation and installation problems of the main arch segment under mountainous transportation conditions. This increases construction efficiency, shortens the construction period, reduces construction risks, and lowers construction costs. At the same time, this main arch retains the competitiveness of arch bridges in terms of good economy, high load-bearing capacity, and strong spanning ability.

[0008] Preferably, there is a stiffness-gradient main arch section between the first main arch section and the second main arch section. From the first main arch section to the second main arch section, the stiffness of the stiffness-gradient main arch section gradually decreases, so as to avoid the impact of sudden changes in the stiffness of the main arch on the excessive local stress of the main arch component.

[0009] Preferably, the skeleton of the first main arch section connected to the stiffness-gradient main arch section is encased in reinforced concrete to form a box structure. The end of the second main arch section connected to the stiffness-gradient main arch section includes only a top plate, a bottom plate, and a web connecting the top plate and the bottom plate. From the first main arch section to the second main arch section, the height of the web formed by the reinforced concrete encasing the web of the stiffness-gradient main arch section gradually decreases.

[0010] The construction method adopted a structural measure in which the height of the web outer cladding gradually changes linearly from full height to no web cladding, making the stiffness change of the main arch section with gradual stiffness change more gradual, which is conducive to structural safety.

[0011] Preferably, from the first main arch segment to the second main arch segment, the web of the main arch segment with gradually changing stiffness gradually loses its outer reinforced concrete covering from the middle to both ends.

[0012] When the height of the web plate gradually changes linearly from full height to no web plate, the reinforced concrete is removed starting from the radial center. This balances the stiffness of the upper and lower chords of the main arch, making the stiffness change of the main arch section with gradually changing stiffness smoother, which is beneficial to structural safety.

[0013] Preferably, the web connection of the first main arch section is a first web connection, which is a triangular structure. Two corners of the triangular structure are respectively connected to two vertically adjacent main pipes, and the remaining corners of the triangular structure are connected to the adjacent first web connection. The remaining corners of the triangular structure are located between the two vertically adjacent main pipes and are directed towards the arch foot along the axis of the main arch.

[0014] The first connecting section, employing a triangular structure oriented towards the arch foot, is more conducive to distributing the axial force of the main arch, reducing the axial force on the main pipe, and ensuring greater safety for the main pipe. Furthermore, given a fixed stress on the first main arch section and a fixed thickness of the outer reinforced concrete, the pipe dimensions of the first connecting section can be smaller than those of the second connecting section. Considering the reduction in calculated length of the members, minimizing the length as much as possible, the triangular arrangement minimizes the length reduction of the members, resulting in optimal stress distribution.

[0015] Preferably, the web connection of the second main arch segment is the second web connection, which is an N-shaped structure. Compared with the triangular structure, the N-shaped structure is simpler, easier to construct, and can meet the stress requirements of the longitudinal center of the main arch.

[0016] Preferably, the first and second connecting pipes each include a plurality of pipe fittings, and the pipe fittings of the first connecting pipe are smaller than those of the second connecting pipe, which saves costs and avoids excessive load-bearing capacity.

[0017] Preferably, the cross-section of the frame is rectangular, the diameter of the main pipe is greater than 300mm and less than or equal to 900mm, the width of the frame is less than 3000mm, and the length of the first main arch section is 20m-40m. This allows the diameter of the main pipe to be reduced to a range of greater than 300mm and less than or equal to 900mm, thereby enabling the width of the frame to be less than 3000mm, thus meeting the transportation capacity requirements in mountainous areas.

[0018] A rigid frame-concrete composite arch bridge includes two main arches located on both sides of the arch bridge and connected by inter-arch cross bracing.

[0019] The rigid frame-concrete composite arch bridge described in this scheme features a first main arch section with a rectangular frame encased in reinforced concrete, forming a box-like structure with a top plate, bottom plate, and webs on both sides. This strengthens the load-bearing capacity of the first main arch section, effectively solving the problem of high axial force at the arch foot section. This allows for optimization of the main arch pipe dimensions, thereby reducing the width of the arch rib segments and meeting the transportation requirements of the arch rib segments. It also solves the transportation and installation problems of the main arch segments under mountainous transportation conditions, resulting in increased construction efficiency, shorter construction period, lower construction risks, and reduced construction costs. At the same time, this arch bridge retains the competitiveness of arch bridges in terms of good economy, high load-bearing capacity, and strong spanning ability.

[0020] Preferably, the inter-arch cross bracing includes an upper chord cross bracing and a lower chord cross bracing;

[0021] The upper chord cross brace includes several cross brace chord tubes and several cross brace diagonal tubes. Each cross brace diagonal tube connects two adjacent cross brace chord tubes, and two adjacent cross brace diagonal tubes and their corresponding cross brace chord tubes form an isosceles triangle.

[0022] The lower chord cross brace includes half the number of cross brace tubes of the upper chord cross brace. The cross brace tubes are connected to the main tubes corresponding to the two main arches. The cross brace tubes of the lower chord cross brace are connected to the cross brace tubes of the corresponding upper chord cross brace through cross brace web tubes. Two adjacent cross brace web tubes and the corresponding cross brace tubes form a right triangle.

[0023] The two main arches are connected by the aforementioned inter-arch cross bracing. The cross bracing tubes of the upper chord cross bracing connect to the main tubes of the upper chord of the two main arches, and the cross bracing tubes of the lower chord cross bracing connect to the main tubes of the lower chord of the two main arches. The cross bracing tubes of the lower chord cross bracing and the corresponding cross bracing tubes of the upper chord cross bracing are connected by cross bracing web tubes to form a right-angled triangle, ensuring a stable connection between the upper and lower chord cross bracings and forming an integral structure. Furthermore, two adjacent cross bracing tubes of the upper chord cross bracing are connected by several diagonal cross bracing tubes to form an isosceles triangle, making the overall integrity of the upper chord cross bracing better than that of the lower chord cross bracing, better meeting the stress requirements, and saving costs.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] 1. The main arch of this invention has four main pipes filled with concrete. The four main pipes, several transverse braces, and several web braces combine to form a skeleton structure. The second main arch section in the longitudinal middle of the main arch is a truss-type steel-concrete composite structure. The two ends of the main arch in the longitudinal direction are the first main arch sections. The skeleton of the first main arch section is encased in reinforced concrete to form a box structure with a top plate, a bottom plate, and webs on both sides. This strengthens the load-bearing capacity of the first main arch section and effectively solves the problem of high axial force in the main arch at the arch foot section, thereby optimizing the dimensions of the main pipes of the main arch. For arch bridges with a span exceeding 300m, the main arch of this design can reduce the dimensions of the main pipes by more than 20% while maintaining the structural safety of the main arch. The width of the arch rib segments is reduced to 3000mm, which meets transportation requirements and solves the problem of transporting and installing main arch segments under mountainous transportation conditions. This increases construction efficiency, shortens the construction period, reduces construction risks, and lowers construction costs. At the same time, this main arch retains the competitiveness of arch bridges in terms of good economy, high load-bearing capacity, and strong spanning ability.

[0026] 2. The main arch of this invention has a gradually changing stiffness section between the first and second main arch sections, avoiding excessive local stress on the main arch components caused by abrupt changes in stiffness. Furthermore, it employs a structural measure where the web is not encased in reinforced concrete from the radial center, with the encasing height gradually changing linearly from full height to no encasing at all. This makes the stiffness change of the gradually changing main arch section smoother, which is beneficial to structural safety.

[0027] 3. In the main arch described in this invention, the first web connection of the first main arch section adopts a triangular structure facing the arch foot, which is more conducive to distributing the axial force of the main arch, reducing the axial force of the main pipe, and making the main pipe safer under stress. Moreover, given a fixed stress on the first main arch section, and a fixed thickness of the outer reinforced concrete, the pipe size of the first web connection can be smaller than that of the pipe size of the second web connection. Considering the reduction in the calculated length of the members, the length is minimized as much as possible. The triangular arrangement of the pipes minimizes the length reduction of the members and optimizes the stress distribution.

[0028] 4. The rigid frame-steel-concrete composite arch bridge of the present invention has a first main arch section that is a box structure with a top plate, bottom plate and two side webs formed by the outer shell of the frame and reinforced concrete. The load-bearing capacity of the first main arch section is strengthened, which can effectively solve the problem of large axial force of the main arch at the arch foot section, thereby achieving the purpose of optimizing the main arch pipe size, and thus reducing the width of the arch rib segment. This can meet the transportation conditions of the arch rib segment, solve the problem of transportation and installation of the main arch segment under the transportation conditions in mountainous areas, and increase construction efficiency, shorten the construction period, reduce construction risks and reduce construction costs. At the same time, the arch bridge retains the competitiveness of arch bridges with good economy, high load-bearing capacity and strong spanning capacity.

[0029] 5. The rigid frame-steel-concrete composite arch bridge of this invention uses inter-arch cross bracing to connect the two main arches. The cross bracing tubes of the upper chord cross bracing connect to the main tubes of the upper chord of the two main arches, and the cross bracing tubes of the lower chord cross bracing connect to the main tubes of the lower chord of the two main arches. The cross bracing tubes of the lower chord cross bracing and the corresponding cross bracing tubes of the upper chord cross bracing are connected by cross bracing web tubes to form a right-angled triangle, so that the upper and lower chord cross bracings are stably connected to form an integral structure. Furthermore, two adjacent cross bracing tubes of the upper chord cross bracing are connected by several cross bracing diagonal tubes to form an isosceles triangle, making the overall integrity of the upper chord cross bracing better than that of the lower chord cross bracing, better meeting the stress requirements, and saving costs. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the side of the main arch in Example 1 (half of the longitudinal direction of the bridge);

[0031] Figure 2 This is a structural schematic diagram of the first main arch segment, the main arch segment with gradually changing stiffness, and the second main arch segment in Example 1.

[0032] Figure 3 This is a side view of the box structure of the first main arch section in Embodiment 1;

[0033] Figure 4 This is a cross-sectional schematic diagram of the box structure of the first main arch section in Example 1;

[0034] Figure 5 This is a schematic cross-sectional view of the connection between the stiffness-gradient main arch segment and the second main arch segment in Example 1.

[0035] Figure 6 This is a schematic diagram showing the arrangement of the third set of reinforcing bars around the main structure;

[0036] Figure 7 This is a schematic cross-sectional view of the second main arch section in Example 1;

[0037] Figure 8 This is a schematic diagram of the inter-arch cross bracing of the first main arch segment of the main arch of the rigid frame-concrete composite arch bridge in Example 2.

[0038] Figure 9 This is a schematic diagram of the cross bracing between the main arch sections of the rigid frame-concrete composite arch bridge in Example 2, showing the gradual change in stiffness of the main arch section and the connection between the main arch section and the second main arch section.

[0039] Figure 10 This is a schematic diagram of the inter-arch cross bracing of the second main arch segment of the main arch of the rigid frame-concrete composite arch bridge in Example 2;

[0040] Figure 11 This is a plan view of the upper chord cross brace of the main arch of the rigid frame-concrete composite arch bridge in Example 2.

[0041] Figure 12 This is a plan view of the lower chord cross brace of the main arch of the rigid frame-concrete composite arch bridge in Example 2.

[0042] Icons: 1-First main arch segment; 2-Main arch segment with gradually changing stiffness; 3-Second main arch segment; 4-Main pipe; 5-Second main arch web joint; 51-Second main arch horizontal web member; 52-Second main arch diagonal web member; 53-Second diagonal connecting rod; 6-Box structure; 61-Top plate; 62-Bottom plate; 63-Web plate; 7-First main arch web joint; 71-First main arch horizontal web member; 72-First main arch diagonal web member; 73-Diagonal member; 74-Horizontal support rod; 75-First diagonal connecting rod; 8-Horizontal connecting pipe; 81-Horizontal diaphragm; 82-Hanging rod sleeve; 9-Horizontal bracing chord; 10-Horizontal bracing diagonal pipe; 11-Horizontal bracing web member; 12-Arch rib centerline; 18-Longitudinal reinforcement; 191-Horizontal reinforcement; 192-Vertical reinforcement; 193-Arc-shaped reinforcement; 20-Stirrup; 21-Main arch centerline. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings.

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Example 1

[0046] This embodiment provides a main arch, such as Figures 1-8 As shown, it includes four main pipes 4, several inner arch cross braces, and several web braces. Two of the main pipes 4 are located on the upper chord, and the other two are located on the lower chord. The four main pipes 4 are connected by the inner arch cross braces and the web braces to form a skeleton. The cross-sectional shape of the skeleton structure can be selected according to requirements. All four main pipes 4 are filled with concrete. The main arch longitudinally includes a first main arch section 1 located at both ends and a second main arch section 3 located in the middle of its longitudinal direction. The skeleton of the first main arch section 1 is encased in reinforced concrete to form a box structure 6. The box structure 6 includes a top plate 61, a bottom plate 62, and web plates 63 on both sides.

[0047] like Figures 4-7 As shown, the main arch includes four main pipes 4, several inner arch cross braces and several web braces in the transverse direction. The two upper main pipes 4 are located on the upper chord, and the two lower main pipes 4 are located on the lower chord. The four main pipes 4 are distributed in a rectangular shape. The four main pipes 4 are connected by the inner arch cross braces and web braces to form a rectangular skeleton. The four main pipes 4 are filled with concrete to form a truss steel pipe concrete structure.

[0048] like Figure 1 As shown, the main arch longitudinally includes a first main arch segment 1 located at both ends and a second main arch segment 3 located in the middle of its longitudinal direction. The second main arch segment 3 in the middle of the main arch longitudinal direction is a truss steel-concrete composite structure. The rectangular skeleton of the first main arch segment 1 is encased in reinforced concrete to form a box structure 6. The box structure 6 includes a top plate 61, a bottom plate 62, and web plates 63 on both sides. The skeleton encasing refers to encasing the upper and lower sides of the main pipe 4 of the upper chord and the transverse bracing formed by the inner arch to form the top plate 61, encasing the upper and lower sides of the main pipe 4 of the lower chord and the transverse bracing formed by the inner arch to form the bottom plate 62, and encasing the transverse bridges of the web bracing on both sides to form the web plates 63.

[0049] The rectangular frame of the first main arch segment 1 is encased in reinforced concrete to form a box-type structure 6 with a top plate 61, a bottom plate 62, and webs 63 on both sides. This reinforced concrete main arch section with a stiffened frame enhances the load-bearing capacity of the first main arch segment 1, effectively solving the problem of high axial force in the arch foot section and thus optimizing the main arch pipe dimensions. For arch bridges with spans exceeding 300m, this main arch design allows for a reduction of the main pipe dimensions by more than 20% while maintaining the structural safety of the main arch. The width of the arch rib segments can be reduced to 3000mm, meeting the transportation requirements of the arch rib segments. This eliminates the need to transport the main pipe of the truss-type steel-concrete composite structure separately, solving the transportation and installation problems of the arch rib segments in mountainous terrain. This increases construction efficiency, shortens the construction period, reduces construction risks, and lowers construction costs. Simultaneously, this main arch retains the competitiveness of arch bridges in terms of economy, high load-bearing capacity, and strong spanning ability. In this embodiment, the arch rib segment refers to a longitudinal segment of the frame, and the width of the arch rib segment is as follows: Figure 7 The width is shown in the left and right directions.

[0050] In this embodiment, the diameter of the main pipe 4 is preferably greater than 300mm and less than or equal to 900mm, and the width of the rectangular frame is less than 3000mm. The length of the first main arch section 1 is set to 20m-40m, which can satisfy the requirement that the diameter of the main pipe 4 be reduced to a range of greater than 300mm and less than or equal to 900mm, thereby enabling the width of the rectangular frame to be less than 3000mm, thus meeting the transportation capacity requirements in mountainous areas.

[0051] In this embodiment, as Figure 4-5 As shown, the box-type structure 6 has internal reinforcing bars, including longitudinal reinforcing bars 18, stirrups, and hoop bars 20. The stirrups are divided into horizontal stirrups 191, vertical stirrups 192, and curved stirrups 193. The top plate 61, bottom plate 62, and webs 63 on both sides of the box-type structure 6 all have horizontal stirrups 191 and vertical stirrups 192. The curved stirrups 193 are only provided in the top plate 61 and bottom plate 62 and are used for anchoring around the main pipe 4. Figure 6 As shown, each main pipe 4 is wrapped around the main pipe 4 from four directions by four arc-shaped reinforcing bars 193, which makes the bonding effect between the concrete and the main pipe 4 better.

[0052] like Figure 1 and Figure 2 As shown, in this embodiment, there is a stiffness-gradient main arch section 2 between the first main arch section 1 and the second main arch section 3. From the first main arch section 1 to the second main arch section 3, the stiffness of the stiffness-gradient main arch section 2 gradually decreases, avoiding excessive local stress on the main arch components caused by abrupt changes in the stiffness of the main arch. Figure 4As shown, the rectangular frame of the main arch section 2, which connects to one end of the first main arch section 1, is encased in reinforced concrete to form a box structure 6; as Figure 5 As shown, the end of the stiffness-gradient main arch section 2 connecting to the second main arch section 3 only includes the top plate 61, the bottom plate 62, and the web connecting the top plate 61 and the bottom plate 62. The web of the stiffness-gradient main arch section 2 is the same as that of the first main arch section, which is the web of the first main arch 7, i.e. Figure 5 The first main arch web 7 at the section of the main arch segment 2 with gradually changing stiffness shown is not encased in reinforced concrete; in this embodiment, as... Figure 2 and Figure 3 As shown, from the first main arch segment 1 to the second main arch segment 3, the height of the web 63 formed by the outer reinforced concrete of the main arch segment 2 with gradually changing stiffness gradually decreases. This means that a structural measure is adopted where the height of the outer web gradually changes linearly from full height to no outer layer at the web, making the stiffness change of the main arch segment 2 with gradually changing stiffness more gradual, which is beneficial to structural safety. Furthermore, when the height of the outer web gradually changes linearly from full height to no outer layer at the web, the outer reinforced concrete is preferentially removed starting from the radial center, balancing the stiffness of the upper and lower chords of the main arch, making the stiffness change of the main arch segment 2 with gradually changing stiffness more gradual, which is beneficial to structural safety. That is, as... Figure 2 As shown, from the first main arch section 1 to the second main arch section 3, the web of the main arch section 2 with gradually changing stiffness gradually loses its outer reinforced concrete covering from the middle to both ends.

[0053] like Figure 2 As shown, in this embodiment, the web connection of the first main arch section 1 and the web connection of the main arch section 2 with gradually changing stiffness are the first web connection. The first web connection is a triangular structure. Two corners of the triangular structure are respectively connected to two vertically adjacent main pipes 4. The remaining corners of the triangular structure are connected to the adjacent first web connection. The remaining corners of the triangular structure are located between two vertically adjacent main pipes 4 and are directed towards the arch foot along the axis of the main arch.

[0054] The second main arch segment 2 has a web connection called the second web connection. The second web connection is an N-shaped structure. Compared with the triangular structure, the N-shaped structure is simpler, easier to construct, and can meet the stress requirements of the longitudinal center of the main arch.

[0055] In this design, the first and second interlocking sections and the inner arch transverse section can all be connected by rods. In this embodiment, the first and second interlocking sections and the inner arch transverse section are each composed of pipes, which reduces their weight and provides corresponding connection reinforcement.

[0056] like Figure 4 , Figure 5 and Figure 7As shown, the two adjacent main pipes 4 of the upper chord of the main arch are connected by a horizontal connecting pipe 8, and the two adjacent main pipes 4 of the lower chord of the main arch are connected by a horizontal connecting pipe 8. And as... Figure 7 As shown, a transverse diaphragm 81 is also provided between the corresponding pipes of the transverse connecting pipe 8 and the second main arch web connecting pipe, which can strengthen the integrity between the main pipe of the second main arch section 3, the second main arch web connecting pipe, and the transverse connecting pipe 8, and improve the overall load-bearing capacity. It can also be seen that, as a mid-span arch bridge, a vertical hanger sleeve 82 is also provided for threading and connecting hangers to provide vertical tension for the main beam of the arch bridge.

[0057] like Figure 2 As shown, the first inter-bracing consists of a first main arch horizontal web member 71 and two first main arch diagonal web members 72. The first main arch horizontal web member 71 is radially connected to the main pipes 4 of the adjacent upper and lower chords. The two first main arch diagonal web members 72 are symmetrically arranged about the axis of the main arch, that is, the two corners formed by the two first main arch diagonal web members 72 and the first main arch horizontal web member 71 are respectively connected to two vertically adjacent main pipes 4. The corners formed by the two first main arch diagonal web members 72 are connected to the middle of the adjacent first main arch horizontal web member 71 and are oriented towards the arch foot along the axis of the main arch. The first inter-bracing adopts the above-mentioned triangular structure oriented towards the arch foot, which is more conducive to distributing the axial force of the main arch, reducing the axial force of the main pipe, and making the main pipe safer under stress. Moreover, given that the stress on the first main arch section 1 is determined, and the thickness of the outer reinforced concrete is determined, the pipe size of the first inter-bracing can be smaller than that of the second inter-bracing. Considering the reduction in the calculated length of the members, the length is minimized as much as possible. The triangular arrangement of the pipes minimizes the length reduction of the members and optimizes the stress distribution. Furthermore, the size of the pipe fitting for the first connection is smaller than that for the second connection, which can save costs and avoid excessive load-bearing capacity.

[0058] In this embodiment, the first interlocking section mentioned above, which is a triangular structure, refers to the continuous loop section in the middle. When it involves the construction and transportation of the main arch in segments, such as... Figure 2 As shown, two adjacent first main arch transverse web members 71 may be connected by a first diagonal connecting member 75. And as... Figure 2 As shown, this is the main arch of a through-arch bridge. Diagonal braces 73 are installed between the horizontal web members 71 of two adjacent first main arches. Horizontal support rods 74 are mounted on the diagonal braces 73, facilitating the erection of the main beams. Of course, depending on the type of arch bridge, such as a through-arch or a lower-arch bridge, the height of the horizontal support rods 74 will vary, and may not necessarily result in a discontinuous triangular structure in the first web member.

[0059] like Figure 2The second main arch web is composed of a second main arch horizontal web member 51 and a second main arch diagonal web member 52. The second main arch horizontal web member 51 is arranged radially along the main arch. Both the second main arch horizontal web member 51 and the second main arch diagonal web member 52 are connected at both ends to the main pipe 4 of the upper chord and lower chord, respectively. The two ends of the second main arch horizontal web member 51 are connected to different ends of two adjacent second main arch diagonal web members 52, and the two ends of the second main arch diagonal web member 52 are connected to different ends of two adjacent second main arch horizontal web members 51. The second main arch web includes two second main arch horizontal web members 51 and one second main arch diagonal web member 52, forming a near-N-shaped structure; or the second main arch web includes one second main arch horizontal web member 51 and two second main arch diagonal web members 52, forming a near-N-shaped structure; or the second main arch web includes one second main arch horizontal web member 51 and one second main arch diagonal web member 52, forming a V-shaped structure. The aforementioned N-shaped or V-shaped secondary main arch spanning section refers to the continuous loop section in the middle. When considering the construction and transportation of the main arch in segments, such as... Figure 2 As shown, two adjacent second main arch diagonal web members 52 may be connected by a second diagonal connecting member 53.

[0060] The main arch, from its base to a suitable position, adopts a steel-concrete composite rigid frame encased in reinforced concrete. The main pipes of the rigid frame are filled with concrete, while the web pipes and main pipes are arranged in a triangular pattern. The rigid frame is encased in C50 reinforced concrete. A stiffness transition section is set at the junction with the truss-type steel-concrete composite main arch section, employing a structural measure where the web encasing height gradually changes linearly from full height to no encasing at all, avoiding abrupt changes in the main arch's stiffness that could lead to excessive local stress on the main arch components. From the end of the stiffness transition section to the arch crown, the main arch uses a truss-type steel-concrete composite structure. The diameter of the main pipe in this section is consistent with that of the main pipe of the rigid frame, while the wall thickness can be varied according to stress requirements. The web pipes and main pipes are arranged in an N-shape.

[0061] Both dead load and live load are vertical, but after being transferred to the main arch, they are decomposed along the main arch's linear direction. For arch bridges, the general characteristic of the main arch's stress is that the axial force of the main pipe is smallest at the arch crown. As the arch progresses towards the arch foot, the main arch section bears more and more loads from the self-weight of the main arch above and the loads transmitted from the suspenders. Therefore, the main arch at the arch foot section experiences the greatest stress and axial force. Using a stiffened reinforced concrete main arch section can achieve a stronger section bearing capacity than a steel-concrete composite main arch section, and it does not require a larger steel pipe than a steel-concrete composite main arch section, thus reducing the size of the main pipe. Under the combined action of dead and live loads, the axial force of the main arch gradually increases from the arch crown to the arch foot. By adopting a reinforced concrete main arch section with a stiffened skeleton at the arch foot, the stress problem of high axial force in the main arch at the arch foot can be effectively solved, thereby optimizing the main arch pipe dimensions. For arch bridges with spans exceeding 300m, the structure designed in this patent can reduce the main pipe dimensions by more than 20% while maintaining the structural safety of the main arch. The 3000mm width of the arch rib segments meets transportation requirements, solving the transportation and installation problems of main arch segments under mountainous transportation conditions. At the same time, this structure retains the competitiveness of arch bridges in terms of good economy, high load-bearing capacity, and strong spanning ability. For example, for an arch bridge with a span of 300m, if a steel-concrete composite main arch is used, the main pipe diameter must be at least 950mm, while with the main arch described in this solution, the main pipe diameter only needs to be 800mm.

[0062] Example 2

[0063] This embodiment provides a rigid frame-steel-concrete composite arch bridge, see [link / reference]. Figures 8-12 It includes two main arches, which are located on both sides of the arch bridge and are connected by inter-arch cross bracing. Figures 9-10 The centerline of the arch rib is shown, but only half of the horizontal direction is shown.

[0064] The rigid frame-concrete composite arch bridge described in this scheme has a first main arch segment 1, which is a box structure 6 with a top plate 61, a bottom plate 62, and two side webs 63 formed by a rectangular frame encased in reinforced concrete. The load-bearing capacity of the first main arch segment 1 is enhanced, which can effectively solve the problem of large axial force in the main arch foot section, thereby optimizing the main arch pipe size and reducing the width of the arch rib segments. This meets the transportation requirements of the arch rib segments, solves the transportation and installation problems of the main arch segments under mountainous transportation conditions, increases construction efficiency, shortens the construction period, reduces construction risks, and lowers construction costs. At the same time, this arch bridge retains the competitiveness of arch bridges with good economy, high load-bearing capacity, and strong spanning ability.

[0065] like Figure 11 and Figure 12 , Figure 11 The transverse centerline 21 of the main arch is shown, and the inter-arch cross bracing includes upper chord cross bracing and lower chord cross bracing.

[0066] The upper chord cross brace includes several cross brace tubes 9 and several cross brace diagonal tubes 10. Each cross brace diagonal tube 10 connects two adjacent cross brace tubes 9, and two adjacent cross brace diagonal tubes 10 and their corresponding cross brace tubes 9 form an isosceles triangle. Figure 11 As shown;

[0067] The lower chord cross brace includes half the number of cross brace tubes 9 of the upper chord cross brace, such as... Figure 12 As shown, the cross bracing tubes 9 of the lower chord cross bracing are spaced at intervals corresponding to the cross bracing tubes 9 of the upper chord cross bracing;

[0068] The horizontal bracing chord 9 connects to the main tubes 4 corresponding to the two main arches. The horizontal bracing chord 9 of the lower chord horizontal brace is connected to the horizontal bracing chord 9 of the corresponding upper chord horizontal brace through a horizontal bracing web tube 11. Two adjacent horizontal bracing web tubes 11 and the corresponding horizontal bracing chord 9 form a right-angled triangle, such as... Figure 8-10 As shown.

[0069] The two main arches are connected by the aforementioned inter-arch cross bracing. The cross bracing tube 9 of the upper chord cross bracing connects to the main tube 4 of the upper chord of the two main arches, and the cross bracing tube 9 of the lower chord cross bracing connects to the main tube 4 of the lower chord of the two main arches. The cross bracing tube 9 of the lower chord cross bracing and the corresponding cross bracing tube 9 of the upper chord cross bracing are connected by cross bracing web tubes 11 to form a right-angled triangle, ensuring a stable connection between the upper and lower chord cross bracings and forming an integral structure. Furthermore, two adjacent cross bracing tubes 9 of the upper chord cross bracing are connected by several cross bracing diagonal tubes 10 to form an isosceles triangle, making the overall integrity of the upper chord cross bracing better than that of the lower chord cross bracing, better meeting the stress requirements, and saving costs.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A main arch comprising four main pipes (4), a plurality of in-arch cross ties and a plurality of web ties, wherein two of the main pipes (4) are located in an upper chord and the other two of the main pipes (4) are located in a lower chord, the four main pipes (4) are connected to form a framework by the in-arch cross ties and the web ties, and the four main pipes (4) are filled with concrete, characterized in that, The main arch longitudinally comprises a first main arch section (1) at both ends thereof and a second main arch section (3) at the middle of the longitudinal direction thereof, the second main arch section (3) being a truss type steel pipe concrete structure, the skeleton of the first main arch section (1) being wrapped with reinforced concrete to form a box type structure (6), the box type structure (6) comprising a top plate (61), a bottom plate (62) and a web plate (63) at both sides, there being a stiffness gradient main arch section (2) between the first main arch section (1) and the second main arch section (3), the stiffness of the stiffness gradient main arch section (2) gradually decreasing from the first main arch section (1) to the second main arch section (3), the skeleton of the end of the stiffness gradient main arch section (2) connected with the first main arch section (1) being wrapped with reinforced concrete to form a box type structure (6), the stiffness gradient main arch section (2) connected with the second main arch section (3) at one end thereof only comprising a top plate (61), a bottom plate (62) and the web connection between the top plate (61) and the bottom plate (62), the height of the web plate (63) formed by the wrapped reinforced concrete of the web connection of the stiffness gradient main arch section (2) gradually decreasing from the first main arch section (1) to the second main arch section (3), the web connection of the stiffness gradient main arch section (2) gradually being free of the wrapped reinforced concrete from the middle thereof to both ends thereof from the first main arch section (1) to the second main arch section (3), so that the stiffness of the top chord and the bottom chord of the main arch is balanced.

2. The main arch of claim 1, wherein, The web connection of the first main arch section (1) is a first web connection, the first web connection being a triangular structure, two corners of the triangular structure being connected with two vertically adjacent main pipes (4) respectively, the remaining corner of the triangular structure being connected with the adjacent first web connection, and the remaining corner of the triangular structure being located between the two vertically adjacent main pipes (4) and being directed towards the arch foot along the axis of the main arch.

3. The main arch of claim 2, wherein, The web connection of the second main arch section is a second web connection, the second web connection being a N-like structure.

4. The main arch of claim 3, wherein, The first web connection and the second web connection respectively comprise a plurality of pipe members, the pipe members of the first web connection being smaller in size than the pipe members of the second web connection.

5. The main arch according to any one of claims 1-4, wherein, The cross section of the skeleton is rectangular, the pipe diameter of the main pipe (4) being greater than 300 mm and less than or equal to 900 mm, the width of the skeleton being less than 3000 mm, the length of the first main arch section (1) being 20-40 m.

6. A stiffening skeleton-concrete filled steel tube arch bridge, characterized in that, Two main arches as claimed in any one of claims 1-5 are comprised, the two main arches being located at both sides of the arch bridge and being connected by inter-arch transverse braces.

7. The bridge according to claim 6, wherein The inter-arch transverse braces comprise top chord transverse braces and bottom chord transverse braces. The upper chord cross brace comprises a plurality of cross brace chord tubes (9) and a plurality of cross brace diagonal tubes (10), the cross brace diagonal tubes (10) are connected to two adjacent cross brace chord tubes (9), two adjacent cross brace diagonal tubes (10) and the corresponding cross brace chord tube (9) form an isosceles triangle, the lower chord cross brace comprises half the number of cross brace chord tubes (9) of the upper chord cross brace, the cross brace chord tubes (9) are connected to the corresponding main tubes (4) of two main arches, the cross brace chord tubes (9) of the lower chord cross brace and the corresponding cross brace chord tubes (9) of the upper chord cross brace are connected through cross brace web tubes (11), two adjacent cross brace web tubes (11) and the corresponding cross brace chord tube (9) form a right triangle.

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