A superimposed 3D-printed and post-cast concrete arch bridge main arch ring and its construction method

Abstract

A main arch ring of an arch bridge using composite 3D printing and post-cast concrete, and a construction method thereof. The arch ring comprises a 3D-printed concrete precast layer, a longitudinal steel mesh, transverse steel bars, and a post-cast concrete layer. The construction method is as follows: a. Vertically, the arch ring is divided into a precast layer and a post-cast layer, and transversely, the precast layer is divided into a plurality of arch ribs; b. Using the longitudinal section of the arch rib as the printing plane, the arch ribs are printed layer by layer using 3D printing concrete technology, with a longitudinal steel mesh placed horizontally every certain number of printed layers; c. The arch ribs are hoisted one by one; d. The transverse steel bars are tied together with the longitudinal steel mesh; e. Concrete is poured on the precast layer to the designed thickness of the arch ring. This composite arch ring construction method does not require formwork or scaffolding, reducing material and labor costs and the risk of working at height; the precast layer can be printed in a factory or near the side of the bridge, resulting in fast construction, minimal impact on the surrounding environment and navigation and traffic under the bridge, and minimal impact from weather.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforced concrete arch bridge construction, and in particular to a main arch ring of an arch bridge using superimposed 3D printing and post-cast concrete, and a construction method thereof. Background Art

[0002] 3D printing technology is considered one of the core technologies leading the new round of scientific and technological revolution and industrial transformation, and is driving the transformation of manufacturing production methods from mass production to personalized customization. As an important component of 3D printing technology, 3D printing concrete technology can achieve digital, automated, and personalized construction. Its outstanding feature is that it avoids the tedious formwork construction process, and the layered molding method has significant advantages in building concrete structures with complex geometries. However, at this stage, 3D printing concrete technology still has many shortcomings. Rebar is difficult to implant into the printed structure. This problem seriously limits the application of this technology in actual engineering projects and has become a bottleneck in realizing the transition of 3D printing concrete technology from the material level to the component level.

[0003] Arch bridges are a widely used type of bridge. Under vertical loads, the main arch section mainly bears axial pressure, and can make full use of materials with good compressive resistance to build them. At present, when building reinforced concrete arch bridges, the construction method of building a scaffold is often adopted, that is, building a wooden scaffold or a steel scaffold under the arch ring. This construction method has the following main disadvantages: (1) The prerequisites for building a scaffold are harsh, requiring the terrain to be relatively flat, the arch ring to be not high from the ground, and there to be no flowing water under the bridge; if there is a river under the bridge, it may be necessary to carry out diversion treatment to provide a stable construction environment for building the scaffold. (2) Due to the unique arch shape of the arch ring, it is difficult to build the scaffold and support the formwork. It not only consumes a large amount of materials, but also consumes a lot of labor and time, resulting in high costs. (3) Building the arch ring scaffold, supporting the formwork, tying steel bars and pouring concrete are all high-altitude operations, which are relatively risky. If the scaffold collapses, it will cause serious casualties and economic losses, as well as negative social impacts. (4) The construction process of erecting the support - supporting the formwork - tying the steel bars - pouring the concrete is complicated, and the construction period at the bridge site is long. It has a great impact on the environment around the bridge site and the traffic and navigation under the bridge. The construction process is greatly affected by bad weather.

[0004] Applying 3D concrete printing technology to the construction of reinforced concrete arch bridges can fully leverage the advantages of digital construction and improve construction efficiency. However, the limited size of the printer makes it difficult to meet the requirements of on-site integrated printing. If the approach is to print the arch ring in sections and then assemble them, reliable measures must be taken to ensure the integrity of the arch ring after assembly. Furthermore, how to embed rebar into the printed concrete is a key issue that must be addressed when applying 3D concrete printing technology to arch ring construction.

[0005] In response to the above problems, the present invention proposes a design concept and construction method for the main arch ring of an arch bridge using superimposed 3D printing and post-cast concrete. The arch ribs are prefabricated using the "3D printing concrete + flattened steel mesh" method, and then assembled using mortise and tenon joints and mortaring. Transverse steel bars are then laid and the upper layer of concrete is poured. This not only eliminates the need for formwork and support for the arch ring, but also forms a three-dimensional steel cage by first laying the steel mesh and then tying the transverse steel bars, solving the problem of embedding steel bars in 3D printed concrete. At the same time, the integrity of the arch ring is ensured through mortise and tenon joints, mortaring connections, superimposed post-cast concrete, and other methods, thereby achieving good stress-bearing performance of the arch ring, simplifying the construction process, shortening the construction period, and reducing construction risks and costs. Summary of the Invention

[0006] The purpose of the present invention is to propose a superimposed 3D-printed and post-cast concrete arch bridge main arch ring and its construction method, aiming to overcome the problems of difficult formwork and scaffolding for reinforced concrete main arch rings, high construction risks, long construction periods, and high costs. At the same time, it broadens the application scenarios of 3D-printed concrete technology, solves the technical bottleneck of difficult steel bar embedding in 3D-printed concrete, and provides a solution for the intelligent, digital, and green construction of arch bridges. The superimposed arch ring construction method provided by the present invention does not require formwork and scaffolding, reducing material and labor costs as well as the risks of high-altitude operations. The prefabricated layer can be printed in a factory or near the side of the bridge, with fast construction speed. The construction process has little impact on the surrounding environment and navigation and traffic under the bridge, and is also less affected by weather.

[0007] To achieve the above objectives, the present invention proposes the following technical solutions:

[0008] A main arch ring of an arch bridge is constructed of laminated 3D-printed and post-cast concrete. The main arch ring comprises, vertically from bottom to top, a precast concrete layer and a post-cast concrete layer. The precast concrete layer comprises one or more 3D-printed concrete longitudinal arch ribs along the transverse direction of the bridge. Longitudinal steel mesh and transverse steel bars are embedded in the precast concrete layer. The longitudinal steel mesh and transverse steel bars form a three-dimensional steel cage within the laminated arch ring, which improves the arch ring's bearing capacity and enhances its integrity.

[0009] Preferably, the composite arch ring concrete is divided into two layers, the upper layer concrete of the composite arch ring is post-cast conventional concrete, and the lower layer concrete of the composite arch ring is 3D printed concrete.

[0010] Preferably, the prefabricated layer of the superimposed arch ring is formed by connecting a plurality of 3D printed concrete longitudinal arch ribs in the transverse direction of the bridge through mortise and tenon joints and mortar joints.

[0011] Preferably, the 3D printed concrete longitudinal arch ribs include two end arch ribs and several identical middle arch ribs, one side of the end arch ribs has a concrete longitudinal protruding strip that is higher than the prefabricated layer of the arch ring, and the other side is a mortise and tenon joint with concave and convex joints; both sides of the middle arch ribs have concave and convex joints respectively; the height of the longitudinal strip protruding from the prefabricated layer is the thickness of the post-cast concrete.

[0012] Preferably, the longitudinal steel mesh includes upper longitudinal steel bars, lower longitudinal steel bars and several oblique and vertical web steel bars, and the web steel bars are welded to the upper and lower longitudinal steel bars; the curvature of the upper and lower longitudinal steel bars is the same as the curvature of the main arch ring, and the length is the arc length of the corresponding position of the main arch ring minus twice the thickness of the concrete protective layer.

[0013] Preferably, the lower longitudinal steel bars and the lower part of the web of the longitudinal steel mesh are buried in the 3D printed concrete prefabricated layer, and the upper longitudinal steel bars and the upper part of the web are buried in the post-cast concrete layer.

[0014] Preferably, the transverse steel bars are divided into upper transverse steel bars and lower transverse steel bars. The upper transverse steel bars are tied together with the upper longitudinal steel bars of the longitudinal steel mesh, and the lower transverse steel bars are placed on the upper surface of the prefabricated layer and tied together with the webs of the longitudinal steel mesh.

[0015] Preferably, the post-cast concrete layer is cast using conventional concrete, with the 3D printed concrete prefabricated layer serving as the bottom formwork and the longitudinal protruding concrete strips printed on the end arch ribs serving as the side formwork.

[0016] The present invention also provides a method for constructing a main arch ring of an arch bridge by combining 3D printing and post-cast concrete, comprising the following steps:

[0017] a. Vertically, the concrete arch ring is divided into a precast layer and a post-cast layer. Transversely, the precast layer is divided into two end arch ribs and several middle arch ribs.

[0018] b. Using 3D printing concrete technology to prefabricate the end arch ribs and the middle arch ribs, a longitudinal steel mesh is placed every certain number of layers during the printing process;

[0019] c. Lift the arch ribs into place piece by piece, and splice them together using concave and convex joints and mortar to form a complete prefabricated layer;

[0020] d. Tie the transverse reinforcement to the longitudinal reinforcement mesh;

[0021] e. Pour concrete on the precast layer until the overlapping arch ring reaches the designed thickness.

[0022] Preferably, the prefabrication of the single arch rib in step b comprises the following steps:

[0023] (1) Use 3D design software to model the arch ribs, further slice the 3D model to obtain the 2D contour shape of each layer, and import the sliced ​​results into the 3D printer operating system. During the modeling and slicing process, determine the appropriate printing strip thickness and width based on the thickness of the arch ring prefabricated layer and the width of the single arch rib, and plan the optimal printing path based on the geometric shape of the arch ring;

[0024] (2) The longitudinal section of the arch rib is used as the concrete printing plane, and the transverse direction is the direction in which the concrete is stacked layer by layer. The matching printing parameters are input into the printer operating system based on the printability of the concrete material.

[0025] (3) Print the inverted concrete arch ribs. After the arch ribs are printed to the set height (number of layers), pause printing and place a piece of longitudinal steel mesh on the concrete parallel to the printing plane. Gently press the steel mesh so that the depth of the steel mesh embedded in the concrete is equal to the radius of the steel bar.

[0026] (4) Repeat step (3) until the number of steel mesh placed in the concrete meets the design requirements;

[0027] ⑸ Continue printing until the arch rib reaches the designed height (i.e. the transverse width of a single arch rib), thus completing the printing of one arch rib.

[0028] Preferably, in step (3), when placing the longitudinal steel mesh, the lower longitudinal steel bars and the lower part of the web of the steel mesh are placed in the concrete, while the upper longitudinal steel bars and the upper part of the web are exposed outside the concrete, and the distance between the lower longitudinal steel bars and the lower edge of the concrete is the thickness of the concrete protective layer of the steel bars.

[0029] Compared with the prior art, the present invention has achieved the following technical effects:

[0030] A composite arch ring construction method that integrates cast-in-place and 3D-printed concrete technologies has been proposed. The core concept of this method lies in reverse decomposition and forward construction. In the reverse decomposition process, a monolithic arch ring is divided into precast and post-cast layers, which are then further divided into multiple arch ribs. In the forward construction process, the separated components are placed into their proper positions to form a monolithic arch ring. This establishes a composite arch ring construction model of integration-decomposition-assembly-reintegration, providing a new approach to arch ring construction.

[0031] Arched concrete structures require complex formwork fabrication, installation, and scaffolding, requiring significant material and labor costs and requiring high-altitude work, posing significant construction risks. Using 3D concrete printing technology to create the precast layers of the main arch ring eliminated these steps, reducing construction costs, safety risks, and time.

[0032] By combining cast-in-place and 3D-printed concrete technology, the resulting main arch ring exhibits significant advantages in terms of bearing capacity and seismic resistance. 3D-printed concrete is typically extruded in strips, resulting in printed grooves on the surface. This enhances the bond between the printed concrete and the subsequent poured concrete, creating a cohesive structure with high bearing capacity and excellent seismic resistance.

[0033] During the arch rib printing process, the longitudinal reinforcement is embedded in the form of a flat steel mesh. Once all the arch ribs are hoisted into place, the transverse and longitudinal reinforcement are tied together to form a stable three-dimensional reinforcement cage, solving the problem of rebar placement. Compared with the currently common method of first reserving holes, then inserting rebar, and then grouting, the construction difficulty is greatly reduced.

[0034] The welding of longitudinal steel mesh and the printing of precast concrete for the arch ring can all be completed by machines in the factory, with a high degree of automated production and easy quality control. A large amount of work is transferred to the factory, reducing the amount of wet work on site. This not only reduces construction costs, ensures project quality, improves construction efficiency, and reduces the impact of external factors such as bad weather, but also reduces the impact on the environment and surrounding traffic. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the splitting of the superimposed arch ring;

[0036] Figure 2 Schematic diagram of the precast layer being divided into multiple arch ribs;

[0037] Figure 3 Schematic diagram of the end arch ribs, middle arch ribs and their cross-sectional concrete profiles;

[0038] Figure 4 A schematic diagram of a precast layer formed by assembling multiple precast arch ribs and its cross-sectional concrete profile;

[0039] Figure 5 This is a schematic diagram of the transverse reinforcement arrangement;

[0040] Figure 6 This is a schematic diagram of the superimposed arch ring after pouring the post-cast concrete layer;

[0041] Figure 7 Schematic diagram of the concrete reaching the set height H1 during the printing process of a single arch rib;

[0042] Figure 8 Schematic diagram of arranging the first steel mesh on the concrete surface at height H1;

[0043] Figure 9 Schematic diagram of the concrete reaching the designed total height H during the printing process of a single arch rib;

[0044] Figure 10 Schematic diagram of longitudinal steel mesh.

[0045] Among them, 1 is the precast concrete layer, 2 is the post-cast concrete layer, 3 is the longitudinal steel mesh, 4 is the transverse steel bar, 5 is the left arch rib, 6 is the middle arch rib, 7 is the right arch rib, 8 is the composite arch ring concrete, the X direction is the longitudinal direction of the bridge, the Y direction is the transverse direction of the bridge, and the Z direction is the vertical direction. H1 and H are the height of the first steel mesh from the printing plane and the total printing height of the arch rib, respectively. DETAILED DESCRIPTION

[0046] In order to more clearly demonstrate the technical route, technical features and technical advantages of the present invention, the present invention will be intuitively demonstrated below in conjunction with specific example drawings. It should be understood that the representative examples provided below are only used to further explain the present invention and are not used to limit the present invention. Other examples based on the expansion and extension of the present invention and without original results are within the scope of protection of the present invention.

[0047] Example 1

[0048] like Figure 1 As shown, the present invention provides a main arch ring of an arch bridge using superimposed 3D printing and post-cast concrete, comprising a precast concrete layer 1, a post-cast concrete layer 2, a longitudinal steel mesh 3 and a transverse steel bar 4.

[0049] The technical route adopted for constructing the composite arch ring is as follows: an arch ring is divided into a precast layer and a post-cast layer, the precast layer is divided into two end arch ribs and several identical middle arch ribs, the arch ribs are precast using 3D printing concrete technology, and the arch ribs are hoisted and spliced ​​piece by piece to form a precast layer. Then, transverse steel bars are tied and concrete is poured on the precast layer, forming a composite arch ring construction concept of whole-split-assembly-whole.

[0050] Example 2

[0051] The specific steps for constructing the main arch ring of the arch bridge in Example 1 are as follows:

[0052] a. The concrete arch ring is divided into a precast layer and a post-cast layer in the vertical direction, and the precast layer of the arch ring is divided into two end arch ribs and several middle arch ribs in the horizontal direction, such as Figure 2 As shown; one side of the end arch rib has a concrete longitudinal protruding strip higher than the precast layer of the arch ring, and the other side is a mortise and tenon joint with concave and convex joints. Both sides of the middle arch rib have concave and convex joints, as shown Figure 3 As shown;

[0053] b. Using 3D printing concrete technology to prefabricate the end arch ribs and the middle arch ribs, a longitudinal steel mesh is placed every certain number of layers during the printing process;

[0054] c. Lift the arch ribs into place piece by piece, and splice them together through concave and convex joints and mortar to form a complete prefabricated layer, such as Figure 4 As shown;

[0055] d. Tie the transverse reinforcement to the longitudinal reinforcement mesh to strengthen the connection between the independent arch ribs and make the composite arch ring more integrated, such as Figure 5 As shown;

[0056] e. Pour concrete on the precast layer until the overlapping arch ring reaches the designed thickness, such as Figure 6 shown.

[0057] Example 3

[0058] In step b of Example 2, prefabrication of a single arch rib comprises the following steps:

[0059] (1) Use 3D design software to model the arch ribs, further slice the 3D model, and import the slice results into the 3D printer operating system;

[0060] (2) Use the XZ plane, i.e. the longitudinal section of the main arch ring, as the concrete printing plane, and the transverse direction of the bridge as the direction of concrete accumulation layer by layer. Enter the matching printing parameters in the printer operating system based on the printability of the concrete material. During the printing process, the printability of the material will change over time, and the printing parameters can be adjusted in real time according to the status of the printed strip.

[0061] ⑶ After printing starts, the printer nozzle moves along the set path and extrude the concrete strips, such as Figure 7 As shown, after the arch rib is printed along the Y direction to the first steel mesh set height H1, the printing is paused and the first steel mesh (such as Figure 10 As shown in the figure, place the steel mesh on the concrete in a direction parallel to the printing plane, and gently press the steel mesh so that the depth of the mesh embedded in the concrete is equal to the radius of the steel bar. Figure 8 It should be noted that to prevent the newly printed concrete material from being unable to withstand the pressure exerted by the steel mesh, causing the steel mesh to sink to a certain extent under its own weight, a concrete pad of a specified thickness must be placed under the steel mesh.

[0062] (4) Continue printing. When the arch rib is printed along the Y direction to the set height H2 of the second steel mesh, pause printing and place the second steel mesh on the concrete in the same way.

[0063] (5) Continue printing. When the arch rib is printed along the Y direction to the third steel mesh at the set height H3, pause printing and place the third steel mesh on the concrete in the same way.

[0064] (6) Continue printing. When the arch rib is printed along the Y direction to the fourth steel mesh at the set height H4, pause printing and place the fourth steel mesh on the concrete in the same way.

[0065] ⑺Continue printing until the arch rib reaches the designed height, and the printing of one arch rib is completed. Figure 9 shown.

[0066] In steps ⑶ to ⑹, when placing the longitudinal steel mesh, the lower longitudinal steel bars and the lower part of the web are placed in the concrete, while the upper longitudinal steel bars and the upper part of the web are exposed outside the concrete. The distance between the lower longitudinal steel bars and the lower edge of the concrete is the thickness of the concrete cover of the steel bars.

[0067] The above content presents the purpose, technical solutions and implementation methods of the present invention based on specific examples, but the scope of protection of the present invention is not limited to this. The contents that are expanded and extended based on the core concept of the present invention without fundamental changes are included in the scope of protection of the present invention.

Claims

1. A main arch ring of an arch bridge made of superimposed 3D printing and post-cast concrete, characterized in that: The main arch ring of the arch bridge comprises a precast concrete layer (1) and a post-cast concrete layer (2) from bottom to top in the vertical direction; the precast concrete layer (1) is composed of one or more 3D printed concrete longitudinal arch ribs along the transverse direction of the bridge, and longitudinal steel mesh (3) and transverse steel bars (4) are embedded in the precast concrete layer (1); The composite arch ring concrete (8) is divided into two layers, the upper layer concrete of the composite arch ring is conventional concrete poured later, and the lower layer concrete of the composite arch ring is prefabricated 3D printed concrete; The concrete prefabricated layer (1) is formed by connecting a plurality of 3D printed concrete longitudinal arch ribs in the transverse direction of the bridge through mortise and tenon joints and mortar joints; The 3D-printed concrete longitudinal arch ribs include two end arch ribs and one or more identical middle arch ribs. One side of the end arch ribs has a concrete longitudinal protruding strip that is higher than the precast layer of the arch ring, and the other side has a concave and convex mortise and tenon joint groove; both sides of the middle arch ribs have concave and convex joint grooves respectively; the height of the longitudinal strip protruding from the precast layer is the thickness of the post-cast concrete; The longitudinal steel mesh (3) comprises an upper longitudinal steel bar, a lower longitudinal steel bar and a plurality of oblique and vertical web steel bars; wherein the web steel bars are welded to the upper longitudinal steel bar and the lower longitudinal steel bar; the curvature of the upper and lower longitudinal steel bars is the same as that of the main arch ring, and the length is the arc length of the corresponding position of the main arch ring minus twice the thickness of the concrete cover; The lower longitudinal reinforcement and the lower part of the web of the longitudinal reinforcement mesh (3) are buried in the 3D printed concrete prefabricated layer, and the upper longitudinal reinforcement and the upper part of the web are buried in the post-cast concrete layer; The transverse reinforcement (4) is divided into an upper transverse reinforcement and a lower transverse reinforcement. The upper transverse reinforcement is tied together with the upper longitudinal reinforcement of the longitudinal reinforcement mesh. The lower transverse reinforcement is placed on the upper surface of the precast concrete layer (1) and tied together with the web of the longitudinal reinforcement mesh.

2. The main arch ring of the arch bridge with superimposed 3D printing and post-cast concrete according to claim 1 is characterized in that: The concrete post-casting layer (2) is cast using conventional concrete, with the 3D printed concrete precast layer as the bottom formwork and the concrete longitudinal protruding strips printed on the end arch ribs as the side formwork.

3. A method for constructing the main arch ring of an arch bridge by combining 3D printing and post-cast concrete according to claim 1 or 2, characterized in that: The following steps are involved: a. The concrete arch ring is divided into a precast concrete layer (1) and a post-cast concrete layer (2) in the vertical direction, and the precast arch ring layer is divided into two end arch ribs and several middle arch ribs along the transverse direction of the bridge; b. Prefabricate the end arch ribs and the middle arch ribs using 3D printing concrete technology, and place a longitudinal steel mesh (3) every certain number of printing layers during the printing process; c. Lift the arch ribs into place piece by piece, and splice them together using concave and convex joints and mortar to form a complete prefabricated layer; d. Tie the transverse reinforcement to the longitudinal reinforcement mesh; e. Pour concrete on the precast layer until the overlapping arch ring reaches the designed thickness.

4. The method for constructing the main arch ring of an arch bridge by combining 3D printing and post-cast concrete according to claim 3, characterized in that: The prefabrication of the single arch rib in step b includes the following steps: (1) Modeling the arch rib using 3D design software, further slicing the 3D model to obtain the 2D contour shape of each cross-section, and importing the slicing results into the 3D printer operating system. During the modeling and slicing process, the thickness and width of the printing strip are determined based on the thickness of the prefabricated layer of the arch ring and the width of the single arch rib, and the optimal printing path is planned based on the geometric shape of the arch ring; (2) Use the longitudinal section of the arch rib as the concrete printing plane, and the transverse direction as the direction in which the concrete is stacked layer by layer. Enter the matching printing parameters in the printer operating system based on the printability of the concrete material. (3) Print the inverted concrete arch rib. When the arch rib reaches the set height, pause printing and place a longitudinal steel mesh on the concrete parallel to the printing plane. Gently press the steel mesh so that it is embedded in the concrete to a depth equal to the radius of the steel bar. (4) Repeat step (3) until the number of steel mesh placed in the concrete meets the design requirements; ⑸ Continue printing until the arch rib reaches the designed height, thus completing the printing of one arch rib.

5. The method for constructing the main arch ring of an arch bridge by combining 3D printing and post-cast concrete according to claim 4, characterized in that: In step (3), when placing the longitudinal steel mesh, the lower longitudinal steel bars and the lower part of the web of the steel mesh are placed in the concrete, while the upper longitudinal steel bars and the upper part of the web are exposed outside the concrete, and the distance between the lower longitudinal steel bars and the lower edge of the concrete is the thickness of the concrete protective layer of the steel bars.

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