CN116911033A - BIM platform-based steel structure virtual trial assembly method - Google Patents

Abstract

The invention provides a steel structure virtual trial assembly method based on a BIM platform, which is used in the field of steel structure creation. It specifically includes the following steps: pre-building a BIM model of the steel structure based on Revit; manufacturing actual steel components according to the BIM model; The actual coordinates of the actual steel component are compared with the theoretical coordinates in the BIM model in Dynamo to obtain an output result; the output result is judged to implement geometric inspection and assembly testing: if the judgment result meets the geometric tolerance and assembly tolerance , then the component meets the target requirements; if the determination result does not meet the geometric tolerance and the assembly tolerance, secondary processing will be performed until the component meets the target requirements. The present invention proposes an innovative framework to implement VTA of complex steel structures on a Building Information Modeling (BIM) platform.

Description

A virtual trial assembly method for steel structures based on BIM platform

Technical field

The invention belongs to the field of virtual testing of steel building materials, and in particular relates to a virtual trial assembly method of steel structures based on a BIM platform.

Background technique

Using virtual trial assembly (VTA) instead of physical trial assembly of complex steel structures significantly reduces manufacturing costs and time. Currently, due to the lack of dedicated VTA systems for steel structures, VTA is usually implemented through third-party quality inspection systems or manual procedures, which faces difficulties in the suitability and assembly information transmission of complex steel structures.

In order to solve the above problems and based on the application of BIM in the manufacturing stage, the present invention proposes an innovative framework to realize VTA of complex steel structures on the Building Information Modeling (BIM) platform.

Contents of the invention

In view of this, the purpose of the present invention is to provide a method to solve the problems of poor applicability and poor assembly information transmission effect of existing steel structures.

In order to achieve the above objects, the present invention provides the following technical solutions:

A virtual trial assembly method for steel structures based on BIM platform, including the following steps:

BIM model of pre-constructed steel structure based on Revit;

Fabricate actual steel components based on the BIM model;

Compare the actual coordinates of the actual steel component with the theoretical coordinates in the BIM model in Dynamo to obtain the output result;

The output results are judged to implement geometric inspection and assembly testing: if the judgment results meet the geometric tolerance and assembly tolerance, the component meets the target requirements; if the judgment result does not meet the geometric tolerance and the assembly tolerance, secondary processing is performed. , until the parts meet the target requirements.

Preferably, the actual coordinates of the actual steel component are compared with the theoretical coordinates in the BIM model in Dynamo to obtain the output result; the specific process includes:

Select assembly points based on the BIM model and obtain theoretical coordinates;

Conduct real component measurements on the actual steel components to obtain actual coordinates;

The theoretical coordinates and the actual coordinates are compared in Dynamo to obtain the output result.

Preferably, the assembly point is the center of the bolt hole that needs to be measured; the assembly point is selected from all bolt holes in the BIM model based on a preset principle.

Preferably, preparations for virtual trial assembly are also included, specifically including:

BI M model preprocessing, assembly process planning, assembly point coordinate measurement and measurement data processing.

Preferably, the assembly points are selected based on the BIM model, specifically including:

Select, mark and number test points in the BI M model;

Among them, a point with a unique number is selected as the assembly point; the theoretical coordinates of the assembly point are obtained through the BIM model.

Preferably, factors to be considered in the assembly process planning include:

S1. Keep the virtual assembly sequence consistent with the design drawings;

S2. Determine whether the potential deformation existing in the physical assembly process affects subsequent assembly; if the judgment result is yes, use multi-level assembly; if the judgment result is no, use one-step assembly;

S3. For a structure that is geometrically divided into multiple units, and the assembly of each unit is independent, each unit is assembled in a separate step, and all units are assembled as a whole.

Preferably, the geometric check is implemented through the EOPA algorithm.

Preferably, the assembly test is implemented through a GPA algorithm.

Compared with the prior art, the present invention has the following beneficial effects:

This invention starts from the BIM model and elaborates on the technical details of each step in the complete VTA process; in this invention, Revit is used as a research platform, and the built-in Dynamo visual programming plug-in is used to develop a VTA program prototype based on the ProcrustesAnalysis algorithm . The prototype fulfills two basic functions: geometry inspection and assembly testing. Finally, the effectiveness of this method was verified by taking the VTA of a steel Truss beam of a 1000m main-span suspension bridge as an example.

Description of the drawings

Figure 1 is a flow chart of the proposed VTA method of the present invention.

Figure 2 is a schematic diagram of assembly point selection results according to the embodiment of the present invention.

3(a)-(b) are schematic diagrams of assembly point markings and numbers according to the embodiment of the present invention.

Figure 4(a)-(b) is a structural diagram of the VTA program prototype of the present invention and a flow chart for implementing VTA in Dynamo.

Figure 5(a) is a geometric dimension diagram of a verification embodiment of the present invention.

Figure 5(b) is a schematic diagram of the Retiv model of the verification embodiment of the present invention.

Detailed ways

The technical solutions provided by the present invention will be described in detail below with reference to the examples, but they should not be understood as limiting the protection scope of the present invention.

Example 1:

This embodiment discloses a steel structure virtual trial assembly method based on BIM platform, which includes the following steps:

BIM model of pre-constructed steel structure based on Revit;

Manufacturing of actual steel components based on BIM models;

Compare the actual coordinates of the actual steel members with the theoretical coordinates in the BIM model in Dynamo to obtain the output results;

The output results are judged to implement geometric inspection and assembly testing: if the judgment results meet the geometric tolerances and assembly tolerances, the parts meet the target requirements; if the judgment results do not meet the geometric tolerances and assembly tolerances, secondary processing is performed until the parts meet the target requirements. .

specifically:

In this embodiment, the method architecture includes: information exchange solution, VTA function implementation solution, and VTA general procedures.

Among them, information exchange solutions:

In order to ensure the consistency of steel structure model information from the design stage to the manufacturing stage, the most direct method is to create and extract information from the same BIM platform in both stages. As a widely used BIM application, Autodesk Revit provides rich and powerful application programming interfaces (APIs) that help extend the functionality of the software. Therefore, in this embodiment, the solution to the data exchange problem is to develop a VTA program in the built-in Dynamo environment of Revit. There are three advantages to developing prototypes in Dynamo BIM compared to other BIM tools. First and foremost, Dynamo is a visual programming tool that provides users with the ability to visualize script behavior, define custom logic fragments, and write scripts in a variety of textual programming languages. Secondly, as a plug-in for software such as Revit, FormIt or Maya, Dynamo supports data exchange with these design tools. Furthermore, Dynamo is an open source application that allows users to extend Dynamo according to their needs and helps designers with parametric concept design and automation tasks. Engineers easily solve complex engineering problems by programming using Dynamo's built-in node library.

Among them, the solution for VTA function implementation:

The results of the model-based and point-based VTA methods are presented in the form of position deviations. In fact, among an infinite number of model points, only those coordinates that affect assembly need to be accurately measured. The real 3D coordinates of the bolt holes are easily obtained by high-precision 3D measuring instruments such as total stations or optical 3D photogrammetry systems, while the theoretical coordinates are extracted from the BIM model. Given two sets of coordinates, the two basic functions of VTA, namely geometry inspection and assembly testing, are implemented by the EOPA and GPA algorithms respectively.

Among them, for the general procedures of VTA:

First, a detailed BIM model of the steel structure is created in Rev it, and then the steel elements are manufactured in the factory based on this model. Next, select assembly points based on the BIM model, including:

Select, mark and number test points in the BI M model;

Among them, points with unique numbers are selected as assembly points; the theoretical coordinates of the assembly points are obtained through the BIM model. Once the steel elements are manufactured, the true three-dimensional coordinates corresponding to the previously marked points in the model are measured in the factory. The theoretical and actual coordinates were then compared using the VTA program developed in Revit Dynamo. Finally, the geometric and assembly deviations of the part are output. If the deviation is within the allowable tolerance, the part is considered qualified and allowed to leave the factory and be assembled on site. Otherwise, the unqualified bolt holes are processed, measured and compared again until the deviation meets the factory requirements.

In addition, this embodiment also includes VTA preparation work, specifically: BIM model preprocessing, assembly process planning, assembly point coordinate measurement, and measurement data processing. Among them, the preparation work of VTA is to collect all data related to VYA;

where, for assembly points:

The assembly point is the center of the bolt hole that needs to be measured; the assembly point is selected from all bolt holes in the BIM model based on preset principles.

Preset principles: 1) In order to reduce the workload of coordinate measurement, the number of collection points should be appropriate, which means that the number or density of selected collection points should not be too large. The corner points of the bolt hole group should be selected. During the manufacturing of steel components, each set of bolt holes is machined by the same machine using the same drilling tool. Considering high-precision machine tool processing, the deviation between holes in a hole group is ignored; therefore, the position information of the entire hole group is represented by measuring the corner points. In order to ensure assembly accuracy, when there are many bolts in the hole group, the number of measuring points should be appropriately increased (Figure 2).

2) The selection of assembly points should also consider the impact of the measurement station layout on the visibility of the measurement target. If the measurement process is interfered with by factors such as the shape of the part and the installation location of the instrument, and it is impossible to collect a certain point, other holes can be selected nearby. Generally, adjacent bolt holes in the same row or column are best used for adjustment. If the position of the assembly point is adjusted at the measurement site, the information of the assembly point should also be updated accordingly in the Revit model to ensure the consistency of theoretical data and measured data.

3) Since the steel plate has a certain thickness, the three-dimensional coordinates of the measurement point should be selected on the outer surface of the component to facilitate measurement and observation. If the assembly of multiple components is coplanar, you should select coplanar points first to reduce the amount of assembly point data.

And for assembly point markers:

The main purpose of point marking is to ensure that the theoretical coordinates of each assembly point are effectively obtained and to enable surveyors to quickly locate the measurement point based on its marking, because the center of the mark is the same as the center of the bolt hole. In this study, a metric universal model-based face family with distinguishable colors was created to mark assembly points. To make the numbering of each assembly point unique, model text parameters with different assignments are added to the family (Figure 3).

Also, for assembly point numbers:

Assembly point numbering is an important step in the implementation of the proposed framework, since the coordinates of these points are queried and matched by numbering during the calculation process. By connecting a series of functional nodes, the automatic bolt hole numbering program is implemented in Dynamo. Through the interaction between Dynamo and Revit models, selected bolt holes are automatically numbered.

In addition, factors that need to be considered for assembly process planning in this embodiment include:

S1. Keep the virtual assembly sequence consistent with the design drawings;

S2. Determine whether the potential deformation existing in the physical assembly process affects subsequent assembly; if the judgment result is yes, use multi-level assembly; if the judgment result is no, use one-step assembly;

S3. For a structure that is geometrically divided into multiple units, and the assembly of each unit is independent, each unit is assembled in a separate step, and all units are assembled as a whole.

It should be noted that the VTA process of steel structures is divided into one-step assembly and multi-step assembly. One-step assembly involves measuring all assembly points at once and comparing them to theoretical coordinates to generate assembly results. A one-step assembly in a virtual environment cannot be synchronized considering an error in the physical assembly process. Therefore, there is a certain deviation between the simulated assembly results and the physical assembly results. Therefore, one-step assembly is suitable for structures with few assembly parts and simple assembly relationships, where assembly errors will not have a predicted impact on the assembly results. Multi-step assembly involves dividing the steel structure into multiple assembly steps in a computer simulation based on the actual assembly process. Its characteristic is that each step of VTA only requires data related to that step, so the data processing is simple. The data collection of VTA in multi-step assembly is synchronized with the physical assembly. That is, after physical assembly in a step, the data required for the next step is collected based on the components assembled in the step. This ensures that VTA data is always up to date, which makes computer simulation results more reliable. The disadvantage of multi-step assembly is that measurement data must be collected step by step and the assembly process is cumbersome. Therefore, VTA process planning should consider many of the above factors, such as design requirements, processing technology, quality acceptance criteria, and geometric structural characteristics of the structure.

Going one step further for bolt hole measurement and measurement data processing:

High-precision total station is suitable for spatial coordinate measurement of bolt holes. Collect the true coordinates of the points by installing an auxiliary tool target. The main factor considered in bolt hole measurements is temperature. Coordinate collection should be carried out in the early morning or evening when the temperature changes range is small. Let the rod length be L and the temperature difference be ΔT. Use the following formula to calculate the elongation ΔL:

ΔL＝ΔT*C*L (1);

In the formula, C is the thermal expansion coefficient of steel,

Assume that the rod lengthens or shortens uniformly axially based on the midpoint of the rod axis. The coordinate compensation value of the measuring points at both ends of the axis is 0.5ΔL. After temperature compensation, the measurement data is saved as an Excel file in a specific format.

The geometric check is implemented through the EOPA algorithm; specifically: the EOPA algorithm describes the matching relationship between measured samples and theoretical samples. In the proposed VTA framework, this is used to check the least square position deviation between the measured and theoretical coordinates of bolt holes or other feature points.

There is an actual coordinate matrix Ap×q and a theoretical coordinate matrix Bp×q, containing p points. q represents the coordinate dimension, where q=2 means the simulation is in 2D space, and q=3 means the simulation is in 3D space. In order to compare coordinates, A must be able to be translated and rotated into alignment with B.

Assume B=A ^T +jt ^T +E(2);

Among them, jt ^T = (1,1,...,1), t _q×1 is the translation vector, t _q×q is the rotation matrix, and E is the error matrix. The goal is to determine the transformation parameters T and t that minimize the square of the 2-norm of E, i.e.

||E|| ² =min{||AT+jt ^T -B||} ² (3);

This problem is solved using the Lagrange multiplier method. Through the properties of orthogonal matrices, the singular value decomposition of matrices is introduced. The singular value decomposition is as follows:

VDW ^T =A ^T (I-jj ^T /p)B (4);

where V, D and W are matrices obtained by singular value decomposition of the right matrix. Use the following formula to obtain the transformation parameters:

T=VW ^T (5);

t=(B-AT) ^T j/p (6).

Assembly testing is implemented through the GPA algorithm; specifically: GPA allows simultaneous and independent estimation of similarity transformation parameters to maximize the correspondence between two or more coordinate matrices toward their centroid matrices. That is to say, by aligning the components through GPA, the corresponding actual hole positions of different components are as close as possible. Correspondingly, the difference between assembly coordinates and theoretical coordinates is larger than that of EOPA.

A1,...,Am(m≥2) represent m data matrices of size p×3, each matrix containing the coordinates of p identical points defined in different reference systems. Among the infinite {t, t} i j (i = 1...m; i < j) similarity transformations linking pairs of i, j matrices for each energy, select a specific transformation that satisfies the following conditions:

The solution to the problem is seen as searching for the unknown "optimal" matrix Z associated with each Ai via an appropriate unknown similarity transformation. written as:

where E i is the random error matrix.

Based on equation (7), the GPA problem is succinctly rewritten as:

One solution to this problem is based on the definition of a centroid matrix C, where C is the centroid of a sequence of transformation matrices:

This method does not directly find ti and ti that minimize equation (9); instead, it uses the properties of the geometric center to bring the result close to the center of mass and obtain the best approximation that satisfies the above conditions. This is the centroid iterative solution. Different computational stages require: 1) iterative solution of the independent similarity transformation of each matrix with respect to the centroid C by using the EOPA algorithm; 2) iterative update of the centroid C by a simple arithmetic mean after the sequential update of the matrix Aip; 3 ) process iterates until convergence, that is, until the value of the center of mass C is stable (the change in the position of the center of mass is less than a certain value). Calculate the final conversion parameters ti and ti based on the initial Ai and final Aip

Furthermore, for the VTA Dynamo prototype mentioned in this embodiment, specifically:

The VTA Dynamo prototype consists of two modules: geometry inspection and assembly testing. The functions of the former are as follows: 1) position deviation check, that is, through the EOPA algorithm, the least square deviation between the measured coordinates and the theoretical coordinates of each bolt hole is calculated to check the machining accuracy of the bolt hole position; 2) geometric size check, That is, the dimensional deviation of steel members is checked by calculating the distance between measurement points and comparing it with the corresponding theoretical distance. The function of the latter is to use the GPA algorithm to check the assembly of multiple components. As shown in Figure 4, the VTA program prototype consists of five parts, each part is described in the following subsections.

a).Input terminal

The function of the input terminal is to obtain data entered by the user. First, you need to prepare a Microsoft Excel file of the Revit model and measured coordinates. The user must then choose which calculation to perform: geometry check or assembly test. Boolean nodes are used for implementation. True means that geometry inspection will be carried out and the component number is required; False means that multiple components will be assembled and tested, and the assembly component number, assembly hole number and allowable tolerance need to be entered.

b).Input data processing

Input data processing involves importing measured and theoretical data from Excel and Revit models respectively to form datasets and storing them as lists in Dynamo. Based on user input, the corresponding data is extracted from the data set to prepare for the next VTA calculation.

The data format, dimensions, and length of the measured coordinates and theoretical coordinates stored in the Dynamo list must be consistent.

c).Main program

The VTA algorithm is implemented by writing Python code in Dynamo's Python script node. Because the EOPA and GPA algorithms involve matrix operations and matrix decomposition, the matrix operation package must be imported first. In this study, the dynamic link library (.dll) file containing matrix operations was imported and referenced at the beginning of the VTA Python script.

The EOPA output is as follows. 1) Best matching coordinates. Through the rotation and translation of the measured coordinates in the theoretical coordinate system, new coordinates that satisfy the least square deviation are obtained. The output is a p×3 matrix, where p is the actual number of bolt holes of the assembled component, and 3 represents the three coordinate components of the theoretical coordinate system. 2) The deviation between the measured coordinates and the theoretical coordinates of the same bolt hole. 3) The geometric distance between two measurement points. GPA outputs the deviation between the final assembly position and the theoretical position after multiple iterations. When multi-step assembly is used, the actual coordinates of the assembled components are used as the theoretical coordinates of the components to be assembled. If the deviation is within the given tolerance, the components are assembled; otherwise, they fail to do so.

d).Output format

After the main program is executed, the results need to be output in a way that is easy for users to understand. The methods used include adding explanatory text to the calculation results and outputting them in a specific format.

f).Output terminal

The purpose of setting the output terminal is to display the VTA calculation results in the output area specified by the Dynamo player.

In addition, this embodiment further includes program verification:

Use a simple example to verify the VTA prototype, as follows. As shown in Figure 5, two square steel plates of the same size are connected through holes No. 2 and 4, while holes No. 1, 3, 5 and 6 are connected to the bracket. The built-in Dynamo player plug-in for Revit is used to run VTA program prototypes.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be made. regarded as the protection scope of the present invention.

Claims (8)

1. A steel structure virtual trial assembly method based on BIM platform, which is characterized by including the following steps: BIM model of pre-constructed steel structure based on Revit; Fabricate actual steel components based on the BIM model; Compare the actual coordinates of the actual steel component with the theoretical coordinates in the BIM model in Dynamo to obtain the output result; The output results are judged to implement geometric inspection and assembly testing: if the judgment results meet the geometric tolerance and assembly tolerance, the component meets the target requirements; if the judgment result does not meet the geometric tolerance and the assembly tolerance, secondary processing is performed. , until the parts meet the target requirements. 2. A virtual trial assembly method of steel structures based on the BIM platform according to claim 1, characterized in that the actual coordinates of the actual steel components are compared with the theoretical coordinates in the BIM model in Dynamo, Obtain the output results; the specific process includes: Select assembly points based on the BIM model and obtain theoretical coordinates; Conduct real component measurements on the actual steel components to obtain actual coordinates; The theoretical coordinates and the actual coordinates are compared in Dynamo to obtain the output result. 3. A steel structure virtual trial assembly method based on the BIM platform according to claim 2, characterized in that the assembly point is the center of the bolt hole that needs to be measured; the assembly point is based on a preset principle, starting from the Select assembly points from all bolt holes in the BIM model. 4. A BIM platform-based virtual trial assembly method for steel structures according to claim 2, characterized in that it also includes virtual trial assembly preparation work, specifically including: BIM model preprocessing, assembly process planning, assembly point coordinate measurement and measurement data processing. 5. A BIM platform-based steel structure virtual trial assembly method according to claim 2, characterized in that the assembly points are selected based on the BIM model, specifically including: Select, mark and number test points in the BIM model; Among them, a point with a unique number is selected as the assembly point; the theoretical coordinates of the assembly point are obtained through the BIM model. 6. A BIM platform-based virtual trial assembly method for steel structures according to claim 4, characterized in that factors that need to be considered in the assembly process planning include: S1. Keep the virtual assembly sequence consistent with the design drawings; S2. Determine whether the potential deformation existing in the physical assembly process affects subsequent assembly; if the judgment result is yes, use multi-level assembly; if the judgment result is no, use one-step assembly; S3. For a structure that is geometrically divided into multiple units, and the assembly of each unit is independent, each unit is assembled in a separate step, and all units are assembled as a whole. 7. A virtual trial assembly method of steel structures based on the BIM platform according to claim 1, characterized in that the geometric inspection is implemented through the EOPA algorithm. 8. A BIM platform-based virtual trial assembly method for steel structures according to claim 1, characterized in that the assembly test is implemented through a GPA algorithm.