Assembling method and system based on BIM assembly type box culvert

Abstract

The invention provides an assembly method and system based on a BIM assembly type box culvert, relates to the technical field of assembly type box culverts, and provides a multi-dimensional quality evaluation method for box culvert assembly based on the BIM technology, so that quantitative analysis of the quality and spatial distribution of box culvert submodules is realized, and an assembly gravity center evaluation index is generated. The gravity center stability and shape distortion in the box culvert assembling process are effectively reflected, meanwhile, through geometric correlation analysis of normal vectors of upper and lower contact planes of the box culvert, a box culvert flatness index is constructed, the flatness degree between box culvert assembling faces is comprehensively reflected, and finally the box culvert gravity center evaluation index and the flatness index are coupled to form an assembling evaluation index. According to the method, the assembly excellence is quantified, the assembly abnormity and risk on the basis of the box culvert appearance can be sensitively and accurately judged, the box culvert assembly detection efficiency and accuracy are remarkably improved, the scheme can be timely adjusted and optimized, and potential safety hazards of the box culvert structure are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of prefabricated box culverts, and in particular to an assembling method and system for prefabricated box culverts based on BIM. Background Art

[0002] Prefabricated box culverts are a type of culvert structure that uses prefabricated components produced in a factory and quickly assembled and installed on site. They are widely used in infrastructure construction such as roads, railways, municipal drainage, and underground pipeline corridors. Compared with traditional cast-in-place concrete box culverts, prefabricated box culverts have the advantages of a shorter construction period, easier to control construction quality, less environmental impact of on-site construction, and high resource utilization. Through standardized design and modular production, prefabricated box culvert components can achieve precise dimensional control and high-quality manufacturing, reducing the concrete pouring and curing processes at the construction site and significantly improving construction efficiency. At the same time, prefabricated box culverts also have good seismic resistance and durability, and can meet the engineering needs under complex geological and environmental conditions. BIM is used in the design and installation of box culverts. BIM, which stands for Building Information Modeling, is a digital design and construction method that integrates various types of information about construction projects through the use of three-dimensional models.

[0003] Existing quality assessment methods for the box culvert assembly process are relatively crude, relying primarily on manual inspection or single-dimensional geometric deviations. This makes it difficult to comprehensively and accurately reflect the overall quality of the box culvert assembly. In particular, the lack of unified quantitative indicators and systematic analysis methods for the comprehensive evaluation of key indicators such as box culvert center of gravity offset, shape distortion, and flatness makes it difficult to effectively monitor and evaluate assembly quality, which in turn affects the long-term structural performance and safety of the box culvert.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a BIM-based assembly method and system for prefabricated box culverts to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: The assembly method of BIM-based prefabricated box culvert includes the following specific steps: S1. Number N box culverts, divide each box culvert into multiple submodules, collect point cloud data of the submodules and import them into 3D modeling software to generate submodule models; S2. Placing the submodule model in a three-dimensional coordinate system, performing a correlation analysis on the submodule to generate the submodule quality, performing a correlation analysis on the submodule quality to generate the center of gravity coordinates of the box culvert model, and performing a correlation analysis on the center of gravity coordinates of the box culvert to generate the center of gravity offset XZP of the box culvert model, the box culvert deviation XPP, and the box culvert center of gravity height XZG. The box culvert deviation XPP is used to reflect the degree of deformity of the overall shape of the box culvert, the center of gravity offset XZP of the box culvert model is used to reflect the stability of the center of gravity of the box culvert, and the box culvert center of gravity height XZG is used to reflect the height of the overall center of gravity of the box culvert. Perform a correlation analysis on the center of gravity offset XZP of the box culvert model, the box culvert deviation XPP, and the box culvert center of gravity height XZG to generate an assembly center of gravity evaluation index PZP; S3. Obtain the plane coordinates of each box culvert, including the upper plane coordinates and the lower plane coordinates, perform correlation analysis on the plane coordinates to generate the box culvert plane equation, perform correlation analysis on the box culvert plane equation to generate the box culvert flatness index XPZ; S4. Perform correlation analysis on the box culvert flatness index XPZ and the center of gravity evaluation index PZP to generate an assembly evaluation index PP. The assembly evaluation index PP is used to reflect the assembly quality of the box culvert. The assembly evaluation index PP is compared with the threshold value to output the assembly evaluation level.

[0007] Furthermore, the N box culverts are numbered in order from bottom to top. Each box culvert model is divided into M submodules. The point cloud data of all submodules are obtained by lidar and imported into the modeling software to generate submodule models. The volume of the jth submodule of the i-th box culvert is .

[0008] Furthermore, the submodules are subjected to correlation analysis to generate the submodule quality , based on the formula: ; Among them, the submodule quality Used to reflect the quality of the jth submodule of the i-th box culvert, the quality of the i-th box culvert for , is the density of the jth submodule of the i-th box culvert; Perform correlation analysis on the submodule quality and generate the coordinates of the center of gravity of the i-th box culvert model , based on the formula: ; in, is the centroid coordinate of the jth submodule of the i-th box culvert model; Center of gravity coordinates of box culvert model Correlation analysis is performed to generate the box culvert model gravity center offset XZP, box culvert deviation XPP and box culvert gravity center height XZG, based on the following formula: ; Among them, the box culvert deviation degree XPP is used to reflect the degree of deviation between other box culverts and the lowest box culvert, and is used to reflect the degree of deformity of the overall shape of the box culvert. The box culvert model center of gravity offset degree XZP is used to reflect the degree of deviation between the comprehensive center of gravity of other box culverts and the center of gravity of the lowest box culvert, and is used to reflect the stability of the center of gravity of the box culvert. The box culvert center of gravity height XZG is used to reflect the height evaluation value of the center of gravity of the box culvert.

[0009] Furthermore, a correlation analysis is performed on the box culvert model center of gravity offset XZP, the box culvert deviation XPP, and the box culvert center of gravity height XZG to generate the assembly center of gravity evaluation index PZP. The formula is as follows: ; Among them, H is the height of the assembled box culvert, L is the length of the box culvert, and the assembly center of gravity evaluation index PZP is used to reflect the evaluation degree of the box culvert assembly through the center of gravity.

[0010] Furthermore, the upper plane equation of the i-th box culvert is set as: , the lower plane equation of the i-th box culvert is: , the constraints are: ; Construct the covariance matrix of the plane coordinate points on the box culvert, obtain the eigenvalues and corresponding eigenvectors of the covariance matrix, where the eigenvector corresponding to the minimum eigenvalue is the plane normal vector, and the upper plane normal vector of the i-th box culvert is , the lower plane normal vector of the i+1th box culvert .

[0011] Furthermore, the upper plane normal vector of the i-th box culvert is and the lower plane normal vector of the i+1th box culvert Correlation analysis is performed to generate the box culvert flatness index XPZ, based on the following formula: ; Among them, the box culvert flatness index XPZ is used to reflect the flatness between the contact planes of the box culvert.

[0012] Furthermore, the correlation analysis of the box culvert flatness index XPZ and the center of gravity evaluation index PZP is performed to generate the assembly evaluation index PP, based on the following formula: ; The assembly evaluation index PP is used to reflect the assembly quality of the box culvert analyzed from the shape aspect.

[0013] Furthermore, the assembly evaluation index PP and the threshold To compare, when When the output box culvert assembly level is level 2, the box culvert assembly risk is high and needs to be redesigned and adjusted. When , the assembly level of the output box culvert is level one and no readjustment is required.

[0014] The present invention also provides a BIM-based assembled box culvert assembly system for executing a BIM-based assembled box culvert assembly method, comprising: The model building module is used to number the box culverts, collect the box culvert point cloud data and import it into the modeling software to generate the box culvert model. Each box culvert is divided into several submodules; The center of gravity analysis module is used to place the box culvert model in a three-dimensional coordinate system, perform correlation analysis on the submodules, generate the submodule mass, perform correlation analysis on the submodule mass, generate the box culvert model center of gravity coordinates, perform correlation analysis on the box culvert center of gravity coordinates, generate the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG, perform correlation analysis on the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG, and generate the assembly center of gravity evaluation index PZP; The flatness analysis module is used to obtain the plane coordinates of each box culvert, including the upper plane coordinates and the lower plane coordinates, perform correlation analysis on the plane coordinates, generate the box culvert plane equation, and perform correlation analysis on the box culvert plane equation to generate the box culvert flatness index XPZ; The output module is used to perform correlation analysis on the box culvert flatness index XPZ and the center of gravity evaluation index PZP, generate the assembly evaluation index PP, compare the assembly evaluation index PP with the threshold, and output the assembly evaluation grade.

[0015] Compared with the prior art, the present invention has the following beneficial effects: Based on BIM technology, the present invention proposes a multi-dimensional quality evaluation method for box culvert assembly. Combined with point cloud data modeling, it realizes quantitative analysis of the quality of box culvert sub-modules and their spatial distribution, generates an assembly center of gravity evaluation index, and effectively reflects the center of gravity stability and shape distortion during the box culvert assembly process. At the same time, through the geometric correlation analysis of the normal vectors of the upper and lower contact planes of the box culvert, a box culvert flatness index is constructed to comprehensively reflect the flatness between the assembled surfaces of the box culvert. Finally, the box culvert center of gravity evaluation index and the flatness index are coupled to form an assembly evaluation index, which quantifies the assembly quality. It can sensitively and accurately judge assembly anomalies and risks based on the box culvert appearance, significantly improve the efficiency and accuracy of box culvert assembly detection, facilitate timely adjustment and optimization of plans, and reduce potential safety hazards of box culvert structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the overall method flow of the present invention; Figure 2 This is a schematic diagram of the overall system module of the present invention; Figure 3 It is the fitting curve diagram of XZG-PZP of the present invention; Figure 4 It is the fitting curve diagram of XZP-PZP of the present invention; Figure 5 is the fitting curve diagram of XPP-PZP of the present invention; Figure 6 is the fitting curve diagram of XPZ-PP of the present invention; Figure 7 It is the fitting curve diagram of PZP-PP of the present invention. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used in the present invention should have the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0019] Example: See also Figure 1 , the present invention provides a technical solution: The BIM-based assembly method for prefabricated box culverts is used to evaluate the vertical assembly stability of the box culvert. The specific steps include: Step 1: Number N box culverts, divide each box culvert into multiple submodules, collect point cloud data of the submodules and import them into 3D modeling software to generate submodule models; N box culverts are numbered in order from bottom to top. Each box culvert model is divided into M submodules. The point cloud data of all submodules are obtained by lidar and imported into the modeling software to generate submodule models. The volume of the jth submodule of the i-th box culvert is .

[0020] Step 2: Place the box culvert model in a three-dimensional coordinate system, perform a correlation analysis on the submodules, generate the submodule quality, perform a correlation analysis on the submodule quality, generate the box culvert model center of gravity coordinates, and perform a correlation analysis on the box culvert center of gravity coordinates to generate the box culvert model center of gravity offset XZP, the box culvert deviation XPP and the box culvert center of gravity height XZG. The box culvert deviation XPP is used to reflect the degree of deformity of the overall shape of the box culvert, the box culvert model center of gravity offset XZP is used to reflect the stability of the box culvert center of gravity, and the box culvert center of gravity height XZG is used to reflect the height of the overall center of gravity of the box culvert. Perform a correlation analysis on the box culvert model center of gravity offset XZP, the box culvert deviation XPP and the box culvert center of gravity height XZG to generate an assembly center of gravity evaluation index PZP. Perform correlation analysis on submodules and generate submodule quality , based on the formula: ; Among them, the submodule quality Used to reflect the quality of the jth submodule of the i-th box culvert, the quality of the i-th box culvert for , is the density of the jth submodule of the i-th box culvert; Perform correlation analysis on the submodule quality and generate the coordinates of the center of gravity of the i-th box culvert model , based on the formula: ; in, is the centroid coordinate of the jth submodule of the i-th box culvert model. The centroid coordinate can be directly obtained by 3D software. Segmenting and dividing the box culvert into blocks for centroid analysis can improve the accuracy of the analysis. Center of gravity coordinates of box culvert model Correlation analysis is performed to generate the box culvert model gravity center offset XZP, box culvert deviation XPP and box culvert gravity center height XZG, based on the following formula: ; Among them, H is the height of the assembled box culvert. The box culvert deviation XPP is used to reflect the degree of deviation between other box culverts and the lowest box culvert, and is used to reflect the degree of deformity of the overall shape of the box culvert. The larger the value of the box culvert deviation XPP, the higher the degree of deformity of the overall box culvert and the worse its stability. The box culvert model center of gravity offset XZP is used to reflect the degree of deviation between the comprehensive center of gravity of other box culverts and the center of gravity of the lowest box culvert, and is used to reflect the stability of the center of gravity of the box culvert. The larger the value of the box culvert model center of gravity offset XZP, the higher the degree of deformity of the overall box culvert and the worse its stability. The larger the value of the box culvert center of gravity height XZG is, the higher the overall center of gravity of the box culvert is, which leads to the worse overall stability of the box culvert. The lower the overall center of gravity of the box culvert is, the less likely it is to be disturbed by external forces and the better the stability is.

[0021] The correlation analysis of the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG is performed to generate the assembly center of gravity evaluation index PZP. The formula is as follows: ; Among them, H is the height of the assembled box culvert, L is the length of the box culvert, is the average value, and the assembly center of gravity evaluation index PZP is used to reflect the evaluation degree of the box culvert assembly through the center of gravity.

[0022] The overall center of gravity height XZG of the box culvert is standardized as a ratio relative to the total height H of the box culvert, and its relative height is calculated. The design of adding 1 ensures that this item is always greater than or equal to 1, avoiding the product of this item being too small, which leads to a decrease in the evaluation index, and reflects the basic contribution of the center of gravity height to the assembly stability. In the part, the sigmoid function provides a smooth threshold response, comparing the center of gravity offset XZP with the box culvert length L as a reference value, thereby reflecting the nonlinear effect of the center of gravity offset on the assembly quality. When the offset exceeds the box culvert length, the risk increases significantly. In the case of box culverts, shape deformity significantly impacts assembly quality, and its contribution is enhanced using a squared form. The greater the deviation, the quadratic increase in the evaluation index, reflecting an increase in the convexity of the risk. Increasing the values of the box culvert model's center of gravity offset (XZP), the box culvert deviation (XPP), and the box culvert's center of gravity height (XZG) increases the assembly center of gravity evaluation index (PZP), and reduces the box culvert's assembly stability.

[0023] Step 3: Obtain the plane coordinates of each box culvert, including the upper plane coordinates and the lower plane coordinates, perform correlation analysis on the plane coordinates, generate the box culvert plane equation, perform correlation analysis on the box culvert plane equation, and generate the box culvert flatness index XPZ; Set the upper plane equation of the i-th box culvert to: , the lower plane equation of the i-th box culvert is: , the constraints are: ; Construct the covariance matrix of the plane coordinate points on the box culvert, obtain the eigenvalues and corresponding eigenvectors of the covariance matrix, where the eigenvector corresponding to the minimum eigenvalue is the plane normal vector, and the upper plane normal vector of the i-th box culvert is , the lower plane normal vector of the i+1th box culvert , is the set constant term of the upper plane equation of the i-th box culvert, is the set constant term of the lower plane equation of the i-th box culvert. The subscripts i and i+1 are used to index the box culvert.

[0024] The covariance matrix reflects the distribution characteristics and discreteness of the plane coordinate points in all directions. First, each coordinate point is centered, the centralized coordinates form a matrix, and the covariance matrix is obtained. ,in The coordinates of each point after centralization, k is used to index the coordinates on the plane, a total of K coordinate points, the covariance matrix is decomposed by eigenvalue, the eigenvector corresponding to the minimum eigenvalue is selected as the plane normal vector, and it is substituted into the plane equation to obtain and The value of .

[0025] Normal vector of the upper plane of the i-th box culvert and the lower plane normal vector of the i+1th box culvert Correlation analysis is performed to generate the box culvert flatness index XPZ, based on the following formula: ; Among them, the box culvert flatness index XPZ is used to reflect the flatness between the contact planes of the box culvert. The value reflects the angle between the upper plane of the i-th box culvert and the lower plane of the i+1-th box culvert. The larger the angle, the more obvious the inclination or misalignment between the planes, indicating that the assembly flatness is worse.

[0026] Step 4: Perform correlation analysis on the box culvert flatness index XPZ and the center of gravity evaluation index PZP to generate the assembly evaluation index PP. The assembly evaluation index PP is used to reflect the assembly quality of the box culvert. The assembly evaluation index PP is compared with the threshold to output the assembly evaluation level.

[0027] The correlation analysis of the box culvert flatness index XPZ and the center of gravity evaluation index PZP is performed to generate the assembly evaluation index PP. The formula is as follows: ; The assembly evaluation index PP is used to reflect the assembly quality of the box culvert analyzed from the shape aspect. The larger the value of the box culvert flatness index XPZ, the worse the flatness between the box culverts, and the larger the assembly evaluation index PP value. The larger the value of the center of gravity evaluation index PZP, the worse the center of gravity stability between the box culverts, and the larger the assembly evaluation index PP value. The flatness index is exponentially amplified to emphasize the impact of flatness on assembly quality. Taking the natural logarithm of the centroid evaluation index makes the value smoother and avoids extreme results caused by abnormally large centroid index. At the same time, the input value range is guaranteed to be valid. The logarithm of the product of the two parts is taken again to suppress extreme values and keep the result within a reasonable range, which is conducive to subsequent threshold judgment.

[0028] Collect XPZ, PZP data and corresponding construction quality grades of a large number of historical assembly projects. Calculate the corresponding PP index and determine the reasonable threshold through statistical analysis. To compare, when When the output box culvert assembly level is level 2, the box culvert assembly risk is high and needs to be redesigned and adjusted. When , the assembly level of the output box culvert is level one and no readjustment is required.

[0029] Reference Figure 3-7 ,in Figure 3-5 It is the fitting curve of the assembly center of gravity evaluation index PZP formula, Figure 6 and Figure 7 In order to assemble the fitting curve of the evaluation index PP formula, the statistical data are collected and organized into Table 1: Table 1: Statistics of assembly center of gravity evaluation index PZP and assembly evaluation index PP

[0030] in, Figure 3-Figure 5 The fitting curves of XZG, XZP, and XPP and the assembly center of gravity evaluation index PZP respectively show that when the values of the box culvert model center of gravity offset XZP, the box culvert deviation XPP, and the box culvert center of gravity height XZG increase, the assembly center of gravity evaluation index PZP increases and the box culvert assembly stability decreases. Figure 6-Figure 7 It reflects the growth relationship between PZP, XPZ and assembly evaluation index PP, and is fitted into a curve, which shows that the larger the value of the box culvert flatness index XPZ, the worse the flatness between the box culverts, and the larger the assembly evaluation index PP value; the larger the value of the center of gravity evaluation index PZP, the worse the center of gravity stability between the box culverts, and the larger the assembly evaluation index PP value. The growth relationship between the assembly center of gravity evaluation index PZP and the assembly evaluation index PP is obtained through fitting.

[0031] The present invention also provides a BIM-based assembled box culvert assembly system for executing a BIM-based assembled box culvert assembly method, comprising: Model building module: number N box culverts, divide each box culvert into multiple sub-modules, collect point cloud data of the sub-modules and import them into 3D modeling software to generate sub-module models; The center of gravity analysis module is used to place the box culvert model in a three-dimensional coordinate system, perform correlation analysis on the submodules, generate the submodule mass, perform correlation analysis on the submodule mass, generate the box culvert model center of gravity coordinates, perform correlation analysis on the box culvert center of gravity coordinates, generate the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG, perform correlation analysis on the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG, and generate the assembly center of gravity evaluation index PZP; The flatness analysis module is used to obtain the plane coordinates of each box culvert, including the upper plane coordinates and the lower plane coordinates, perform correlation analysis on the plane coordinates, generate the box culvert plane equation, and perform correlation analysis on the box culvert plane equation to generate the box culvert flatness index XPZ; The output module is used to perform correlation analysis on the box culvert flatness index XPZ and the center of gravity evaluation index PZP, generate the assembly evaluation index PP, compare the assembly evaluation index PP with the threshold, and output the assembly evaluation grade.

[0032] The above formulas are all dimensionless and numerical calculations. The formulas are obtained by collecting a large amount of data and performing software simulation to obtain the most recent real situation. The preset parameters in the formulas are set by technicians in this field according to actual conditions.

[0033] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software depends on the specific application and design constraints of the technical solution.

[0034] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, and may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment as needed.

[0035] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

Claims

1. The assembly method of BIM-based prefabricated box culvert is characterized by: The specific steps include: S1. Uniquely identify and encode the target box culvert, split the box culvert into multiple submodules, collect 3D point cloud data of each subunit, and store the data in a structured database. Using a computer-aided design platform, convert the point cloud data into a digital geometric model to generate a submodule model. S2. Construct a unified three-dimensional spatial coordinate system to spatially locate and associate each submodule model. Based on the model's internal quality parameter calculation mechanism, analyze the spatial relationship and correlation between the submodules to generate the center of gravity coordinates of the box culvert model. Through multidimensional data correlation analysis, calculate the center of gravity offset, box culvert deviation, and box culvert center of gravity height of the box culvert model, and generate an assembly center of gravity evaluation index. S3. Collect spatial coordinate data of the box culvert surface, use a data association algorithm to perform plane fitting on the coordinate point set, generate a corresponding plane mathematical model, and calculate the box culvert flatness index based on the fitting results as a quantitative evaluation of the box culvert surface flatness; S4. Use the multivariate data fusion model to comprehensively analyze the box culvert flatness index and the assembly center of gravity evaluation index to generate an assembly evaluation index to determine whether the assembly requirements are met.

2. The assembly method of a BIM-based prefabricated box culvert according to claim 1 is characterized in that: N box culverts are numbered in order from bottom to top. Each box culvert model is divided into M submodules. The point cloud data of all submodules are obtained by lidar and imported into the modeling software to generate submodule models. The volume of the jth submodule of the i-th box culvert is .

3. The assembly method of a BIM-based prefabricated box culvert according to claim 2 is characterized in that: Perform correlation analysis on submodules and generate submodule quality , based on the formula: ; Among them, the submodule quality Used to reflect the quality of the jth submodule of the i-th box culvert, the quality of the i-th box culvert for , is the density of the jth submodule of the i-th box culvert; Perform correlation analysis on the submodule quality and generate the coordinates of the center of gravity of the i-th box culvert model , based on the formula: ； in, is the centroid coordinate of the jth submodule of the i-th box culvert model; Center of gravity coordinates of box culvert model Correlation analysis is performed to generate the box culvert model gravity center offset XZP, box culvert deviation XPP and box culvert gravity center height XZG, based on the following formula: ； Among them, H is the height of the assembled box culvert, the box culvert deviation XPP is used to reflect the degree of deviation between other box culverts and the lowest box culvert, and is used to reflect the degree of deformity of the overall shape of the box culvert, the box culvert model center of gravity offset XZP is used to reflect the degree of deviation between the comprehensive center of gravity of other box culverts and the center of gravity of the lowest box culvert, and is used to reflect the stability of the box culvert's center of gravity, and the box culvert center of gravity height XZG is used to reflect the height evaluation value of the box culvert's center of gravity.

4. The assembly method of a BIM-based prefabricated box culvert according to claim 3 is characterized by: The correlation analysis of the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG is performed to generate the assembly center of gravity evaluation index PZP. The formula is as follows: ； Among them, H is the height of the assembled box culvert, L is the length of the box culvert, and the assembly center of gravity evaluation index PZP is used to reflect the evaluation degree of the box culvert assembly through the center of gravity.

5. The assembly method of a BIM-based prefabricated box culvert according to claim 4 is characterized in that: Set the upper plane equation of the i-th box culvert to: , the lower plane equation of the i-th box culvert is: , the constraints are: ； Construct the covariance matrix of the plane coordinate points on the box culvert, obtain the eigenvalues and corresponding eigenvectors of the covariance matrix, where the eigenvector corresponding to the minimum eigenvalue is the plane normal vector, and the upper plane normal vector of the i-th box culvert is , the lower plane normal vector of the i+1th box culvert .

6. The assembly method of a BIM-based prefabricated box culvert according to claim 5 is characterized in that: Normal vector of the upper plane of the i-th box culvert and the lower plane normal vector of the i+1th box culvert Correlation analysis is performed to generate the box culvert flatness index XPZ, based on the following formula: ； Among them, the box culvert flatness index XPZ is used to reflect the flatness between the contact planes of the box culvert.

7. The assembly method of a BIM-based prefabricated box culvert according to claim 6 is characterized in that: The correlation analysis of the box culvert flatness index XPZ and the center of gravity evaluation index PZP is performed to generate the assembly evaluation index PP. The formula is as follows: ； The assembly evaluation index PP is used to reflect the assembly quality of the box culvert analyzed from the shape aspect.

8. The assembly method of a BIM-based prefabricated box culvert according to claim 7 is characterized in that: The assembly evaluation index PP and the threshold To compare, when When the output box culvert assembly level is level 2, the box culvert assembly risk is high and does not meet the assembly requirements, and needs to be redesigned and adjusted. When , the assembly level of the output box culvert is level one, which meets the assembly requirements and does not require readjustment.

9. A BIM-based assembled box culvert assembly system, used to execute the BIM-based assembled box culvert assembly method according to claim 1, characterized in that: include: The model building module is used to number N box culverts, divide each box culvert into multiple sub-modules, collect the point cloud data of the sub-modules and import them into the 3D modeling software to generate the sub-module models; The center of gravity analysis module is used to place the box culvert model in a three-dimensional coordinate system, perform correlation analysis on the submodules, generate the submodule mass, perform correlation analysis on the submodule mass, generate the box culvert model center of gravity coordinates, perform correlation analysis on the box culvert center of gravity coordinates, generate the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG, perform correlation analysis on the box culvert model center of gravity offset XZP, box culvert deviation XPP and box culvert center of gravity height XZG, and generate the assembly center of gravity evaluation index PZP; The flatness analysis module is used to obtain the plane coordinates of each box culvert, including the upper plane coordinates and the lower plane coordinates, perform correlation analysis on the plane coordinates, generate the box culvert plane equation, and perform correlation analysis on the box culvert plane equation to generate the box culvert flatness index XPZ; The output module is used to perform correlation analysis on the box culvert flatness index XPZ and the center of gravity evaluation index PZP, generate the assembly evaluation index PP, compare the assembly evaluation index PP with the threshold, and output the assembly evaluation grade.

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