A method for 3D printing a large-span structure and its printed structure

Abstract

The present invention provides a method for 3D printing a large-span structure and the printed structure thereof, including a model creation step: establishing a digital model of a large-span concrete member and obtaining a spatial curved surface model; acquiring a force flow curve and converting it into a structural space grid model with thickness and height; setting a given roof printing thickness for the spatial curved surface model to obtain a roof skin model, and integrating it with the structural space grid model to form a composite integral structure model; a 3D printing step: extracting the structural space grid model and the roof skin model; performing 3D printing on the grid contour with concrete, and pouring UHPC into the grid contour to obtain a grid; performing 3D printing on the roof skin model with concrete to obtain a roof. The present invention solves the problem of the relatively weak printability of ultra-high performance concrete by 3D printing the main structural contour and then pouring ultra-high performance concrete into the structure. At the same time, it also reduces the material consumption and structural self-weight of large-span concrete structures.

Description

Technical Field

[0001] The present invention belongs to the technical field of building construction, and relates to a method for realizing 3D printing of large-span structural members by means of ultra-high performance concrete and its printed structure. Background Art

[0002] With the development of 3D printing concrete technology, more and more 3D printing methods have emerged in the industry, such as variable curved surface printing and interlayer printing methods. These new methods can improve the rationality of 3D printing structure in path generation and realize more complex geometric forms. However, due to the tensile property limitations of the commonly used printing materials in the field of 3D printing concrete, such as Portland cement, sulfoaluminate cement, and geopolymer cement, even though these materials can print complex forms, when completing large-span horizontal structures, due to material limitations, the size of the completed structure is still limited. For the current improvement means of 3D printing technology, ultra-high performance concrete (UHPC) is adopted, or usually, steel bars need to be added during the printing process to meet the force requirements of large-span horizontal structures.

[0003] The above methods often have the following problems:

[0004] I. Material limitation: These traditional concrete materials have good workability, that is, good fluidity in the fresh state and sufficient support capacity during the hardening process, so they are suitable for 3D printing technology. However, these materials only have good compressive properties and do not have sufficient tensile properties. When realizing large-span horizontal members (such as roof beams, roofs, and ceilings), using these materials cannot meet the structural requirements of the design.

[0005] II. Manpower input: Currently, there are mainly two construction methods for 3D printing horizontal structures. One is to print the structure shell by 3D printing, then insert a steel reinforcement cage into the structure and pour the internal cavity. The other is to adopt the post-tensioning method, divide the large-span structure into multiple segments for printing, and then connect and tighten them with through steel bars to convert the prestress of the steel bars into pressure to achieve structural strengthening. However, these methods all involve the complicated processes of tying and fixing steel bars and require a large amount of manpower to participate, which greatly limits the application of 3D printing technology in the construction field.

[0006] III. Printability issues of high-performance materials: Ultra-high-performance concrete (UHPC) is a material with mechanical properties and durability superior to those of traditional concrete, and has great application potential in the field of 3D printing. However, the limitations of this material are as follows: First, the fresh UHPC has strong fluidity, so it does not have sufficient adhesion and forming ability after being extruded from the print head. Second, the fiber content in UHPC is higher than that of the silicate cement commonly used in 3D printing, and all are steel fibers, so it is not convenient to transport in the pumping system and pipeline system. Third, the steel fibers have high hardness and toughness, so they cannot be evenly distributed after extrusion and are easily exposed on the surface, which not only affects the printing effect but also reduces the structural performance. Finally, the current research on the printability of UHPC mostly stays in the laboratory stage, and there is no effective method to apply it in actual projects.

[0007] Therefore, how to provide a method for combining traditional concrete with UHPC to build a large-span structure with complex shapes without a mold through 3D printing and its printed structure is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the present invention proposes a method for 3D printing a large-span structure and its printed structure to solve the technical problems in the prior art.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention discloses a method for 3D printing a large-span structure, including a model creation step and a 3D printing step:

[0011] Model creation step:

[0012] S11: Establish a digital model of a large-span concrete member and obtain a spatial curved surface model;

[0013] S12: Obtain the force flow curve of the spatial curved surface model;

[0014] S13: Perform an offset operation on the force flow curve to convert it into a structural space grid model with thickness and height;

[0015] S14: Set a given roofing printing thickness for the spatial curved surface model to obtain a roofing skin model, and perform a Boolean union operation with the structural space grid model to form a composite integral structure model;

[0016] S15: Export the composite integral structure model.

[0017] 3D printing step:

[0018] S21: Extract the structural space grid model and the roofing skin model from the composite integral structure model;

[0019] S22: Generate corresponding printing lines according to the structural space grid model, perform 3D printing on the grid outline using concrete, pour UHPC into the grid outline, and wait for the material to solidify to obtain the grid, then proceed to S24;

[0020] S23: Generate corresponding printing lines according to the roof skin model, perform 3D printing on the roof skin model using concrete, and wait for the material to solidify to obtain the roof, then proceed to S24;

[0021] S24: Assemble the 3D printed roof and the grid.

[0022] Preferably, S12 includes:

[0023] According to the structural force information of the space curved surface model, obtain the starting position of the force flow and the load of the component.

[0024] Preferably, the load includes the gravity load of the self-weight of the component;

[0025] Or, it includes the gravity load of the self-weight of the component and the concentrated load, and obtain the stress point of the concentrated load, which together with the starting position of the force flow and the load is used as the input for calculating the force flow curve.

[0026] Preferably, S13 includes:

[0027] S131: Extract the force flow curve at a fixed step length to obtain an effective curve for modeling;

[0028] S132: Offset the effective curve horizontally, and then extrude the offset curve vertically, so as to transform the force flow curve into a structural space grid model with thickness and height.

[0029] Preferably, before S15, it also includes: perform finite element analysis on the composite overall structure model to determine whether it meets the force requirements; if so, proceed to S15; if not, adjust the parameters of the structural space grid model and then repeat this step.

[0030] Preferably, the finite element analysis of the composite overall structure model in S15 includes: the input of the finite element analysis includes the starting position of the force flow of the component, the load, and the mechanical properties of UHPC; the finite element analysis calculates the stress on each grid surface, and determines whether the structure fails based on whether the stress exceeds the maximum stress that the structure can bear; where UHPC is used to pour the structural space grid, and the grid surface is the Mesh surface obtained by transforming the composite overall structure model.

[0031] Preferably, the parameters of the adjusted structural space grid model in S15 include: increasing the thickness and height of the structural space grid model, or increasing the density of the effective curve by reducing the fixed step size.

[0032] Preferably, before S22, it further includes: loading integrated components according to the required thickness of the structural space grid model and the form of the roof skin model to form corresponding combined joints, including one or more of drainage components, thermal insulation components, and wiring components;

[0033] Before pouring UHPC in the grid outline, embed the integrated components required for the structure in the grid outline.

[0034] Preferably, S23 includes the step of judging whether the roof skin model needs to be printed in blocks. If so, enter S232; if not, enter S231:

[0035] S231: Divide the roof skin model into blocks so that the size of each block is smaller than the relatively smaller value of the maximum printable size and the maximum transportable size of the 3D printing concrete equipment, and then enter S232.

[0036] S232: Use the method of surface layering to cut the roof skin model to generate corresponding printing lines and import them into the printing equipment.

[0037] The present invention also discloses a printing structure, which is obtained by constructing according to the method of 3D printing large-span structures described above.

[0038] It can be seen from the above technical solutions that, compared with the prior art, the present invention combines the printability of traditional concrete (portland cement, sulfoaluminate cement, geopolymer cement) with the structural characteristics of ultra-high performance concrete, and uses 3D printing to build large-span structural components with complex shapes without a mold. The beneficial effects of the present invention include:

[0039] (1) It reduces the use of formwork and steel bars during the building construction process and reduces the carbon emissions throughout the building life cycle.

[0040] (2) By the method of 3D printing ordinary concrete and then pouring UHPC in the present invention, the large-span complex curved surface not only has printability but also has better durability due to the addition of the high-tensile performance material UHPC.

[0041] (3) The present invention solves the application limitation problem of ultra-high strength concrete in the field of 3D printing. Since UHPC itself does not have ideal printability, the present invention proposes to pour UHPC as a structural strengthening material into the 3D printing structure, which not only meets the most efficient use of materials in the additive manufacturing method but also ensures the construction accuracy and quality of the large-span curved roof.

[0042] (4) The construction method proposed by the present invention can meet the requirements of both integrated printing and prefabrication and post-assembly. Users can adjust the construction method of the roof according to the requirements of the carrying capacity and hoisting capacity in the actual project. Therefore, the invention has strong flexibility.

[0043] (5) The present invention only uses ultra-high performance concrete at the core stress positions, while ordinary concrete that is lighter in weight and cheaper in price is used to wrap the outer periphery of the structure. This approach can minimize the structural self-weight and obtain better cost performance at the same time. Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings;

[0045] Figure 1 It is a flowchart of a method for 3D printing a large-span structure provided by an embodiment of the present invention;

[0046] Figure 2 It is a schematic diagram of the 3D printing and construction process provided by an embodiment of the present invention;

[0047] Figure 3 It is a schematic diagram of the assembly of a 3D-printed sentry box provided by an embodiment of the present invention;

[0048] Figure 4 It is a schematic diagram of the assembly of a 3D-printed roof module unit provided by an embodiment of the present invention. Detailed Embodiments

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0050] As Figure 1 shown, the first aspect of the present invention discloses a method for 3D printing a large-span structure, which is specifically divided into two major parts. The first part is model generation and verification, and the second part is 3D printing and construction.

[0051] The steps of model structure generation and verification are as follows:

[0052] S11: Establish a digital model of large-span concrete components and obtain a spatial curved surface model;

[0053] S12: Obtain the force flow curve of the spatial curved surface model;

[0054] S13: Perform an offset operation on the force flow curve to transform it into a structural space grid model with thickness and height;

[0055] S14: Set a given roofing printing thickness for the spatial curved surface model to obtain a roofing skin model, perform a Boolean union operation with the structural space grid model to form a composite integral structure model;

[0056] S15: Export the composite integral structure model.

[0057] The steps of 3D printing and construction are as follows:

[0058] S21: Extract the structural space grid model and the roofing skin model from the composite integral structure model;

[0059] S22: Generate corresponding printing lines according to the structural space grid model, perform 3D printing of the grid outline with concrete, pour UHPC in the grid outline, and wait for the material to cure to obtain the grid, and enter S24;

[0060] S23: Generate corresponding printing lines according to the roofing skin model, perform 3D printing of the roofing skin model with concrete, and wait for the material to cure to obtain the roof, and enter S24;

[0061] S24: Assemble the 3D printed roof and grid.

[0062] In one embodiment, S12 includes:

[0063] According to the structural force information of the spatial curved surface model, obtain the force flow starting point position and load of the component.

[0064] In one embodiment, the load includes the gravity load of the self-weight of the component;

[0065] Or, it includes the gravity load of the self-weight of the component and the concentrated load, and obtain the concentrated load acting point, which together with the force flow starting point position and load is used as the input for calculating the force flow curve. The concentrated load can be set according to specifications and building functions, such as determining the concentrated load acting point according to the specific position of the equipment placed on the roof. In addition, uniform loads such as wind, snow, and people on the roof generally need to be considered.

[0066] In one embodiment, S13 includes:

[0067] S131: Extract the force flow curve at a fixed step size to obtain an effective curve for modeling;

[0068] S132: Horizontally offset the effective curve, and then extrude the offset curve vertically, thereby transforming the force flow curve into a structural space grid model with thickness and height.

[0069] In one embodiment, before S15, it further includes: performing finite element analysis on the composite integral structure model to determine whether the force-bearing requirements are met; if so, proceed to S15; if not, adjust the parameters of the structural space grid model and then repeat this step.

[0070] In one embodiment, the finite element analysis of the composite integral structure model in S15 includes: the inputs of the finite element analysis include the force flow starting position of the component, the load, and the mechanical properties of UHPC; the finite element analysis calculates the stress on each grid surface, and determines whether the structure fails based on whether the stress exceeds the maximum stress that the structure can bear; wherein, UHPC is used to pour the structural space grid, and the grid surface is the Mesh surface obtained by transforming the composite integral structure model.

[0071] In one embodiment, adjusting the parameters of the structural space grid model in S15 includes: increasing the thickness and height of the structural space grid model, or increasing the density of the effective curve by reducing the fixed step size.

[0072] The detailed implementation steps of the model generation and verification part with the aid of computer-aided design software and the force flow analysis method are as follows:

[0073] S11: Use computer-aided design software to establish a digital model of a long-span concrete component for 3D printing, and obtain a spatial curved surface mesh model;

[0074] S12: According to the structural stress situation of the mesh model, input the model of the component, the force flow starting position, and the load situation in the Karamba plug-in of Grasshopper.

[0075] The point where the axis of the support structure of the component intersects with the component is the starting point of the force flow;

[0076] The load situation should be input according to the actual stress situation of the component, including the gravity load of the self-weight of the component and other loads.

[0077] The spatial curved surface mesh model surface is the surface on which the gravity load is applied.

[0078] Gravity load value = volume of the mesh surface * density of the expected UHPC material used * gravitational acceleration g. If the designed component is also subject to a concentrated load, the concentrated load application point and the load value are input simultaneously.

[0079] After inputting the component model, the force flow starting point, and the load situation into the Karamba plug-in, according to the force flow method, the force flow curve is obtained in the geometric configuration of the curved surface.

[0080] In this embodiment, the force flow can be implemented based on the Karamba plug-in in the visual programming language Grasshopper. The force flow method is a structural design method for describing and analyzing the behavior of force transmission in components. It regards the transmission of force as the flow of water. Since the path that the force passes through in a mechanical system is the path with greater stiffness and shortest length, the space grid generated by the force flow is the most effective in terms of structural performance and material use.

[0081] The force flow calculation method is as follows: perform finite element analysis according to the input component model and load conditions, analyze the force conditions of each finite element, extract the main force direction of the finite element as the normal direction of the force flow curve, and then connect these curves.

[0082] S131: Extract the force flow curves generated in the previous step according to a fixed step size a, that is, extract 1 effective curve for modeling every a + 1 force flow curves. If there are b force flow curves in total, then a total of b / (a + 1) curves are extracted.

[0083] S132: In the computer-aided design software Rhino, offset the extracted force flow curves in the horizontal direction by a distance of d / 2 (d is the actual required grid thickness), and then extrude the offset curves in the vertical direction by a distance of h (h is the actual required grid height), so as to convert the force flow lines into a structural space grid model with thickness and height.

[0084] S14: Extrude the space surface mesh model in S11 by the set roof printing thickness to obtain the roof skin model, and perform a Boolean union operation with the structural space grid model obtained in S132 in the rhino software to form a composite overall structure model; and use the mesh command in rhino to convert this model into a Mesh surface (i.e., grid surface) that can be used for the next structural analysis.

[0085] It should be noted that: the roof skin model can be formed according to the thickness of the foundation roof, and according to the arrangement position of the required integrated components on the roof, the specified skin position can be set to different skin shapes, including: when adding pre-buried pipelines and drainage pipelines designed later, the shape of the skin needs to be changed, such as making a drainage slope on the roof top surface and reserving space for pipeline passage on the inner side.

[0086] S140: Perform finite element analysis on the mesh model of the composite integral structure obtained in S14 in a finite element analysis software (such as Abaqus, Ansys, MSC, Karamba, etc.). The data required for the analysis includes the force flow starting point (support point) and load position described in S12, and also includes the mechanical properties of the UHPC selected for the structure (including the ultimate compressive strength and ultimate tensile strength).

[0087] In finite element analysis, the stress on each mesh surface will be calculated, and it will be determined whether the structure fails based on whether the stress exceeds the maximum stress that the structure can bear. If the structure fails, it is necessary to enter S141; if the structure is effective, enter S15.

[0088] S141: Appropriately increase the thickness d and height h of the grid structure, or increase the grid density by reducing the step size a, and then return the structure to S140.

[0089] S15: Export the structure model.

[0090] In one embodiment, before S22, it further includes: loading integrated components according to the required thickness of the grid structure model in the structural space and the form of the roof skin model to form corresponding combined nodes, including one or more of drainage components, thermal insulation components, and wiring components;

[0091] Before pouring UHPC in the grid outline, embed the integrated components required for the structure in the grid outline.

[0092] In one embodiment, S23 includes the step of judging whether the roof skin model needs to be printed in blocks. If so, enter S232; if not, enter S231:

[0093] S231: Divide the roof skin model into blocks so that the size of each block is smaller than the relatively smaller value of the maximum printable size and the maximum transportable size of the 3D printing concrete equipment, and then enter S232.

[0094] S232: Use the method of surface layering to divide the roof skin model, generate corresponding printing lines, and import them into the printing equipment.

[0095] The detailed implementation steps of the 3D printing and construction steps are as follows:

[0096] S200: Input the structure model in the computer-aided design software Rhino.

[0097] S201: Perform integrated design according to the required grid thickness and roof form to meet the drainage, thermal insulation, or wiring requirements of the structure.

[0098] If the component is a roof, an organized drainage design is carried out on the upper surface of the roof. According to the specification requirements and local rainfall conditions and other data, the drainage slope is calculated, and the organized drainage surface is designed in combination with the position of the drain pipe to ensure that rainwater can be drained to the drain pipe in an organized manner while minimizing the impact on the facade.

[0099] When the component is a roof or a floor slab, a space is provided below for pipelines such as water supply, electricity, and air conditioning to pass through, and at the same time, it is combined with the indoor ceiling shape to enhance the aesthetic degree of the building.

[0100] If the component needs to be combined with other building components, corresponding combination nodes should be designed at the component.

[0101] S21: Extract the space grid model and the roof model respectively. The space grid model is used for S221 - S225, and the roof model is used for S231.

[0102] S221: Extract the side profile of the grid model and offset the side profile inward by (m / 2) into the grid, where m is the printing line width.

[0103] S222: According to the set printing height, horizontally divide the offset side profile. The division interval is n, where n is the printing line height. Starting from the lowest point of the z-axis of the offset side profile model, a plane is generated every height n until the highest point of the z-axis of the side profile model, and a total of x planes are generated; calculate the intersection lines of these planes and the offset profile model to obtain x curves, and thus generate the printing lines for printing the grid model. Then, translate the printing lines into G-code recognizable by the printing device in Grasshopper and import them into the printing device.

[0104] S223: Use traditional concrete (portland cement, sulfoaluminate cement, or geopolymer cement) for 3D printing of the grid profile.

[0105] S224: Embed the pipelines (such as electric wires, lamp tubes, water pipes, etc.) and connection nodes required for the structure in the printed grid profile.

[0106] S225: Pour UHPC into the grid profile and wait for the material to solidify for use in step 18.

[0107] S230: Judge whether the roof needs to be printed in sections according to the construction requirements. If the roof can be transported to the construction site as a whole and meets the requirements of overall hoisting, it can directly enter S232; if not, it needs to enter S231.

[0108] S231: According to the 3D printing concrete equipment used and the transportation requirements, the maximum size of the component a*b*c is obtained, where a, b, and c are relatively small values ​​that simultaneously meet the maximum length, width, and height that can be printed by the 3D printing concrete equipment and the maximum length, width, and height that can be transported. The three-dimensional model of the roof is divided into blocks so that the size of each block is smaller than a*b*c, and then enters S232.

[0109] S232: Use the surface layering method to divide the roof and generate corresponding printing lines. Then translate the printing lines into G codes in Grasshopper and import them into the printing device.

[0110] S24: Use traditional concrete to 3D print the roof or roof components. The structural joints can be embedded during the printing process, and then wait for the material to solidify.

[0111] S25: Transport the grid and the roof to the construction site and assemble them. Insulation materials can be filled into the grid according to actual use requirements.

[0112] The method described in the above embodiment of the present invention solves the problem of optimal structural calculation of large-span building components and simulation of material mechanical properties with the help of computer-aided design software and force flow analysis, and is summarized into a set of workflows that are scalable.

[0113] The method described in the above embodiment of the present invention solves the problem of poor printability of ultra-high performance concrete by 3D printing the main structure outline and then pouring ultra-high performance concrete in the structure. At the same time, it also reduces the material consumption and structural deadweight of the large-span concrete structure.

[0114] The method described in the above embodiment of the present invention proposes a prototype that integrates drainage, insulation, and pipeline design in a 3D printed floor, which can be applied to a variety of different building scenarios.

[0115] The method described in the above embodiment of the present invention introduces a full 3D printing workflow for large-span structural components to minimize human involvement in all aspects from design to construction.

[0116] In summary, the embodiments of the present invention realize 3D printing of large-span building components and make the printed structure durable.

[0117] like Figure 2 As shown, the first aspect of the present invention discloses a printing structure, which is constructed according to a method for 3D printing a large-span structure.

[0118] Two specific embodiments of the printing structure are shown below:

[0119] Example 1: Schematic diagram of the combination of the pipeline system and the grid roof

[0120] As Figure 3 shown, 10 is a 3D printed traditional concrete roof for self - organizing drainage, 20 is a drain outlet, 30 is a grid outline printed with traditional concrete by 3D printing, 40 is a space grid cast with UHPC, 50 is a pre - embedded lamp tube, and 60 is a glass window.

[0121] This embodiment is a 3D printed sentry box. The roof is a complex spatial curved surface capable of self - organizing drainage. Using the traditional formwork casting method requires special customization of formwork and consumes a large amount of manpower for assembly. At the same time, the structural performance of traditional concrete cannot meet the large span of this sentry box. Therefore, this sentry box is printed and constructed using the 3D printing method of the present invention combined with UHPC casting. At the same time, the pipelines required for lighting inside the sentry box can be pre - embedded during the printing process (S224), and the glass window can be integrally assembled in S25.

[0122] Embodiment Two: Schematic Diagram of the Combination of Thermal Insulation Material and Grid Roof

[0123] As Figure 4 shown, 11 is a 3D printed traditional concrete roof, 21 is a thermal insulation material, 31 is a space grid cast with UHPC, 41 is a grid outline printed with traditional concrete by 3D printing, and 51 is a 3D printed traditional concrete ceiling.

[0124] This embodiment is a 3D printed roof module unit. If traditional concrete is used for 3D printing, it cannot meet the required span of the structure. Therefore, it is printed and constructed using the 3D printing method of the present invention combined with UHPC casting. At the same time, the inside of the grid can be filled with thermal insulation material and sealed by two 3D printed roof panels from above and below. If the thickness of the grid is greater than the actual required thickness of the thermal insulation layer, the lower roof panel can bulge upwards along the grid structure to form a porous texture. This ensures the minimum use of thermal insulation material and at the same time produces a more diverse ceiling effect.

[0125] The method for 3D printing large - span structures and its printed structures provided by the present invention are introduced in detail above. In this embodiment, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

[0126] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for 3D printing a large-span structure, characterized in that It includes a model creation step and a 3D printing step: Model creation step: S11: Establish a digital model of a long-span concrete component and obtain a spatial curved surface model; S12: Obtain the force flow curve of the spatial curved surface model; S13: Perform an offset operation on the force flow curve to transform it into a structural space grid model with thickness and height; S14: Set a given roofing printing thickness for the spatial curved surface model to obtain a roofing skin model, and perform a Boolean union operation with the structural space grid model to form a composite integral structure model; S15: Export the composite integral structure model; 3D printing step: S21: Extract the structural space grid model and the roofing skin model from the composite integral structure model; S22: Generate corresponding printing lines according to the structural space grid model, perform 3D printing of the grid outline with concrete, pour UHPC in the grid outline, and wait for the material to solidify to obtain the grid, and enter S24; S23: Generate corresponding printing lines according to the roofing skin model, perform 3D printing of the roofing skin model with concrete, and wait for the material to solidify to obtain the roof, and enter S24; S24: Assemble the 3D printed roof and the grid.

2. The method for 3D printing a large-span structure according to claim 1, wherein The S12 includes: According to the structural force information of the spatial curved surface model, obtain the force flow starting point position and load of the component.

3. The method for 3D printing a large-span structure according to claim 2, wherein The load includes the gravity load of the self-weight of the component; Or, it includes the gravity load of the self-weight of the component and the concentrated load, and obtain the concentrated load acting point, which together with the force flow starting point position and load is used as the input for calculating the force flow curve.

4. The method for 3D printing a large-span structure according to claim 1, wherein The S13 includes: S131: Extract the force flow curve at a fixed step size to obtain an effective curve for modeling; S132: Offset the effective curve in the horizontal direction, and then extrude the offset curve in the vertical direction, so as to transform the force flow curve into a structural space grid model with thickness and height.

5. The method for 3D printing a large-span structure according to claim 1, characterized in that, Before the S15, it also includes: perform a finite element analysis on the composite integral structure model to judge whether it meets the force requirements; if so, enter S15; if not, adjust the parameters of the structural space grid model and then repeat this step.

6. The method for 3D printing a large-span structure according to claim 5, wherein, The finite element analysis of the composite integral structure model in the S15 includes: the input of the finite element analysis includes the force flow starting point position, load of the component, and the mechanical properties of UHPC; the finite element analysis calculates the stress on each grid surface, and judges whether the structure fails based on whether the stress exceeds the maximum stress that the structure can bear; among them, UHPC is used to pour the structural space grid, and the grid surface is the Mesh surface obtained by transforming the composite integral structure model.

7. The method for 3D printing a large-span structure according to claim 4, wherein Adjusting the parameters of the structural space grid model in the S15 includes: increasing the thickness and height of the structural space grid model, or increasing the density of the effective curve by reducing the fixed step size.

8. The method for 3D printing a large-span structure according to claim 1, characterized in that, Before the S22, it also includes: load integrated components according to the required thickness of the structural space grid model and the form of the roofing skin model to form corresponding combined nodes, including one or more of drainage components, thermal insulation components, and wiring components; Before pouring UHPC in the grid outline, embed the integrated components required by the structure in the grid outline.

9. The method for 3D printing a large-span structure according to claim 1, characterized in that, The S23 includes a step of determining whether the roof skin model needs to be printed in blocks. If so, it proceeds to S232; if not, it proceeds to S231: S231: Divide the roof skin model into blocks such that the size of each block is smaller than the relatively smaller value of the maximum printable size and the maximum transportable size of the 3D printing concrete equipment, and then proceed to S232; S232: Use the method of surface layering to divide the roof skin model, generate corresponding printing lines, and import them into the printing equipment.

10. A printing structure, characterized in that, The printing structure is obtained by constructing according to the method of 3D printing large-span structures described in any one of claims 1-9.

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