Method for applying Grasshopper parametric modeling in deepening of steel pipe arch

Abstract

The invention provides a method for applying Grasshopper parametric modeling in deepening of a steel pipe arch, and belongs to the technical field of steel pipe arch design, and the method comprises the following steps: arch rib line shape and positioning control, chord pipe modeling, comparison optimization of chord pipe control lines by adopting a genetic algorithm, batch staggered joint adjustment of shell rings, and lofting and unfolding of intersecting lines and pipe tangent lines. And accessory structure parametric modeling, part batch processing and drawing generation. According to the method, a Grasshopper parametric modeling deepening method is adopted, the drawing deepening work of the whole steel pipe arch is completed from the aspects of arch rib line shape rechecking and drawing, factory machining segmentation design, pipe fitting arrangement and reasonable weld joint optimization, pipe fitting joint treatment, curved surface unfolding, batch drawing and labeling and the like, the drawing deepening time is saved, the part precision is improved, and the production efficiency is improved. The problems of large drawing difficulty, long occupied time, difficulty in drawing modification, difficulty in precision guarantee and the like of steel pipe arch drawing deepening design are effectively solved, and a new development direction is provided for deepening design of similar projects in the future.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe arch design, and particularly to a method for applying Grasshopper parametric modeling in the deepening of steel pipe arches. Background Art

[0002] As an important part of super-large bridges, the deepening design of steel pipe arch structures is highly professional. The deepening design of steel pipe arches involves problems such as catenary lofting, superimposition of cambers, offset of hanger positions, positioning of web pipes, intersection line cutting, staggered joints of cylinder sections, and surface development of pipe sections. Usually, steel pipe arch bridges are mostly special-shaped structures, with large drawing difficulty, high precision requirements, and large deepening workload. Traditional steel pipe arch deepening technologies mostly adopt a combination of two-dimensional drawing software and formula calculation. During the operation process, there are problems such as a huge amount of calculation data, difficult error control, and cumbersome modification process. Therefore, it is necessary to design a method for applying Grasshopper parametric modeling in the deepening of steel pipe arches. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for applying Grasshopper parametric modeling in the deepening of steel pipe arches, and solve the technical problems that existing steel pipe arch deepening technologies mostly adopt a combination of two-dimensional drawing software and formula calculation, and there are problems such as a huge amount of calculation data, difficult error control, and cumbersome modification process during the operation process.

[0004] Therefore, in-depth research on steel pipe arch parametric modeling technology has important value and significance. Combining with the actual deepening design process of the Yellow River Extra-large Bridge of the Gaoqing-Shanghe Highway Project, this paper introduces the key technologies of steel pipe arch parametric deepening design, providing a new development direction for steel pipe arch bridge deepening technology.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for applying Grasshopper parametric modeling in the deepening of steel pipe arches, the method comprising the following steps:

[0007] Step 1: Control the alignment and positioning of the arch rib;

[0008] Step 2: Model the chord pipe and optimize the comparison of the chord pipe control line by using the genetic algorithm;

[0009] Step 3: Adjust the staggered joints of cylinder sections in batches;

[0010] Step 4: Loft and develop the intersection line and pipe tangent line;

[0011] Step 5: Parametric modeling of the accessory structure;

[0012] Step 6: Batch processing of parts and drawing generation.

[0013] Furthermore, in Step 1, the catenary curve is adopted for the shape of the steel pipe arch. During drawing, the camber and the offset of the suspender need to be superimposed to correct the shape of the arch rib and control the positioning nodes. During the parametric deepening process of the arch rib, the catenary curve of the steel arch rib is first reviewed. After confirmation, the manufacturing shape is corrected by the superposition method, the curvature continuity of the manufacturing shape is optimized, and a smooth interpolation curve is generated according to the positioning nodes. The subsequent processes are all expanded and optimized based on the control line. The plug-in script reads and filters the external table data as needed, and a processing program is written in Python and C# languages. Combining with the built-in script of Grasshopper, the processing of segmented information, list information, data calculation, conditional judgment, and graphic drawing operations are completed. The program flow of visual control and operation avoids human errors in the drawing process of the arch rib shape, greatly reduces the computer memory occupancy, and makes the processing logic of a large number of curve data more rigorous, preparing for the batch processing of subsequent tree-shaped data.

[0014] Furthermore, in Step 1, when there are changes in the shape or segmented data, directly change the input parameters of the external list, or adjust the pre-data of the parametric process, and the subsequent parametric model will also automatically change, effectively avoiding the work of repeated drawing modification.

[0015] Furthermore, in Step 2, for the chord tube modeling, first, a single-track sweep of a third-order curve is adopted. When avoiding the belly tube and segmented positions, the genetic algorithm is used to compare the control lines of the chord tubes, and the barrel segmenting method that most closely approximates the curve modeling is automatically found to meet the specification requirements that the minimum jointing length of the steel pipe arch chord tube is not less than 1000 mm and not less than the steel pipe diameter, and the processing requirement of the maximum length of in-plant rolled tubes of 2500 mm, reducing the adverse impact of jointing on the structural strength. Then, several re-surface chord tubes are redrawn according to the optimized broken line. The broken line barrel segments optimized by the genetic algorithm can more accurately fit the original curve chord tube, increasing the accuracy of the bridge model and meeting the processing requirements of the factory. At the same time, the segmented method adjusted by the program also reduces the generation of human errors and improves the efficiency of barrel segment splitting.

[0016] Furthermore, in Step 3, the requirements for the longitudinal weld stagger between adjacent chord tubes are that the upper longitudinal weld stagger is greater than 200 mm and the stagger with the intersecting line weld is greater than 80 mm. Affected by the number of segments and the shape, the types of chord tube barrels are more than the set value. It is difficult to adjust the position of the longitudinal joint line of each barrel one by one, and the rotation angle of the joint cannot be accurately changed, resulting in low efficiency and high error rate. In the parametric modeling process, the longitudinal joints of a large number of chord tube barrels are staggered according to the preset stagger angle, the starting point of the normal circular section is adjusted, and the position of the longitudinal weld of the barrel is changed, which can accurately and efficiently complete the barrel stagger, providing a high-precision plate edge reference line for the subsequent surface development.

[0017] Furthermore, in Step 4, when pipes intersect, there will be the problem of intersection curves. The intersection curves of several pipes are often more complex and usually have no regular pattern. There are intersection curves between chord pipes and web pipes, between chord pipes in the horizontal bracing, and between K-braced web pipes. Before the cylinder section of the chord pipe is developed, it is also necessary to cut the pipe joint tangent line so that the straight cylinder section pipes meet the arc requirement of the extended pipe after connection. The 3D models of pipe fittings with pipe tangent lines and intersection curves are mostly generated by solid cutting in 3D software. It is impossible to process solid models in large quantities. The Boolean operation speed of the computer to process solid models is slow, and the generated intersection curves are also difficult to meet the high-precision production requirements. The intersection curve pipe fittings are solved by unfolding the irregular surface through the finite element method.

[0018] Furthermore, in Step 4, first, the intersection curve and pipe tangent line are lofted. The pipe fittings of web pipes, horizontal bracings, and K-braces are classified and listed by circular pipes in the parametric process, and the Boolean operation of the parametric model is carried out in batches. The generated model is changed in real time. Compared with the solid model operation speed, it is several times faster. At the same time, the accuracy of the generated surface model is also higher than that of the mesh model. After the chord pipe cylinder section is segmented, the large station number side of the straight cylinder section is extended, and then it is cut according to the end section of the small station number side of the next cylinder section. The small station number side of the cut chord pipe cylinder section is a flat tangent line, and the large station number side is an inclined tangent line.

[0019] The surface unfolding of pipe fittings. The surface is unfolded through the finite element method, and any spatial surface is discretized into a set of spatial triangular element folded surfaces. Considering mechanical factors, using the differential principle, any workpiece is regarded as a combination of the smallest mechanical units. The stress and deformation of the workpiece are the sum of the stress and deformation on the smallest units. Since the mechanical properties of the smallest units are simple, the finite element method only focuses on the algorithm of the smallest units and relies on the high-speed computing power of the computer to solve the stress of any workpiece. The incremental finite element method and the Grasshopper script file are used to complete the batch unfolding of the surfaces of cylinder sections and web pipes, achieving a high-precision and high-efficiency surface unfolding effect.

[0020] Furthermore, in Step 5, the steel pipe arch inspection walkways are arranged on the chord pipes and wind bracings at fixed intervals. The inspection walkways between the upper and lower chord pipes are connected by adding inspection walkways on the web pipes. The inspection walkways of each arch rib section are different. The transition inspection walkway on the web pipe needs to leave a distance greater than the set value from the upper chord pipe and connect the upper end to the inspection walkway on the wind bracing. Through parametric modeling, the batch drawing of the arch rib inspection walkways is achieved, and the connection position of the inspection walkway on the web pipe can be adjusted and changed. The number and position of the inspection walkway support plates are automatically judged, and enough space for personnel operation is left above the inspection walkway on the web pipe.

[0021] Furthermore, in Step 6, more than 3,100 detailed drawings were generated. The types of parts counted in the drawings exceeded 3,000, and the number of parts exceeded 71,500. Parametric modeling can flexibly obtain cross-sectional graphics of each part or flip each graphic to the required plane, and batch generate two-dimensional or three-dimensional drawings. By means of parameterization, batch marking and numbering operations are carried out on part drawings, unit drawings, jig drawings, etc., further improving the efficiency of the detailed drawing of the steel pipe arch. Compared with similar projects deepened in the past, with the same human input, the Grasshopper parametric modeling deepening design applied to the steel pipe arch has an efficiency increase of about 31% compared with the traditional CAD drawing technology.

[0022] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

[0023] The present invention adopts the Grasshopper parametric modeling deepening method to complete the entire deepening work of the steel pipe arch drawings from aspects such as the review and drawing of the arch rib alignment, the factory processing sectional design, the reasonable optimization of the pipe fitting layout and welds, the treatment of pipe fittings joints, the surface development, the batch drawing and marking, etc. It saves the time for deepening the drawings, improves the part accuracy, effectively solves the problems such as the large drawing difficulty, long time occupation, difficult drawing modification, and difficult accuracy guarantee in the deepening design of the steel pipe arch drawings, and also provides a new development direction for the deepening design of future similar projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the rendering of the Gaoshang Yellow River Extra-large Bridge of the present invention;

[0025] Figure 2 is the parametric flow chart of the arch rib alignment drawing of the present invention;

[0026] Figure 3 is the first-span drawing of the arch rib curve and positioning points of the present invention;

[0027] Figure 4 is the unoptimized curve segmentation (simulation) drawing of the present invention;

[0028] Figure 5 is the optimized curve segmentation (simulation) drawing of the present invention;

[0029] Figure 6 is the optimized chord pipe segmentation drawing of the present invention;

[0030] Figure 7 is the cross-sectional drawing of the staggered joint position of the chord pipe cylinder section of the present invention;

[0031] Figure 8 is the staggered joint treatment drawing of the chord pipe cylinder section of the present invention;

[0032] Figure 9 is the rendering of the intersecting line cutting model of the web pipes, horizontal bracings, etc. of the present invention;

[0033] Figure 10 It is a diagram of the tangent cutting method of the chord tube of the present invention;

[0034] Figure 11 It is the surface diagram of the batch unfolded cylinder section of the present invention;

[0035] Figure 12 This is a diagram showing the unfolding effect of the pipe fitting of the present invention;

[0036] Figure 13 It is a parametric layout diagram of the maintenance road of the present invention;

[0037] Figure 14 It is a batch drawing of cross sections of the present invention;

[0038] Figure 15 It is a flip diagram of the K-bracing model of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0040] Examples:

[0041] The main bridge of the Yellow River Bridge of the Gaoqing to Shanghe Highway Project adopts a span arrangement of 190+260+260+190 meters of steel tube concrete tied arch, the full width of the bridge deck is 43.2 meters, the main beam adopts a double-sided main beam, the steel arch adopts a four-chord steel tube arch structure, and the steel arch is consolidated with the arch seat pier and the arch beam is separated. The arch rib main pipe adopts a four-tube lattice system, the arch axis adopts a catenary, the radial height of the arch rib section is divided into 5.0 meters and 6.0 meters, the rib width is 2.8 meters, and the chord diameter is 1 meter. The calculated span of the 190-meter span is 184 meters, the calculated height loss is 40.89 meters, the calculated span of the 260-meter span is 254 meters, the calculated height loss is 56.44 meters, the calculated rise-span ratio is 1 / 1.45, and the arch axis coefficient is 1.4. The steel tube arch is affected by the longitudinal slope of the bridge deck and is an asymmetric structure. The arch ribs on one side are divided into 92 segments, and the two sides have a total of 184 segments. The maximum weight is 74 tons, and the maximum segment is 22.4 meters long. There are 24 transverse wind braces and 8 temporary braces, which are 36 meters long. Except for the segments bolted together by flanges, all other connections are welded. Figure 1 shown.

[0042] With the rapid development of the steel structure manufacturing industry in China, the drawing refinement design technology of steel pipe arch bridges has gradually matured. The Yellow River Extra-large Bridge of the Gaoqing-Shanghe Highway Project is a concrete-filled steel tube tied-arch bridge. To achieve the goal of rapid, batch, accurate drawing disassembly and modification, the Grasshopper parametric modeling method was adopted for the first time, and a parametric drawing process and plug-in applicable to steel pipe arch bridges were compiled, verifying the feasibility of this new technology with high precision, high efficiency, and high flexibility in the refinement design of steel pipe arch bridges, providing new ideas for the refinement work of similar projects and the secondary development of related software in the future.

[0043] Specific process: The refinement design of the steel arch rib structure of this bridge mainly adopts the following process: linear data calculation and review → segmented data processing → adding longitudinal manufacturing offsets for suspenders → linear lofting → tube surface model lofting → barrel joint subdivision and staggered joints → avoiding abdominal tube interference → barrel joint surface unfolding → generating abdominal tube intersecting solid models → modeling tube spacers and stiffeners → positioning and modeling wind braces → modeling accessory structures → batch labeling of parts → generating and labeling model cross-sections → drawing refinement → batch modification of drawings; among them, except for the drawing refinement step that requires adjusting drawing details and output format in 2D drawing software, the rest of the steps are written into the parametric process.

[0044] Step 1: Control of arch rib alignment and positioning

[0045] The alignment of the steel pipe arch adopts a catenary curve. When drawing, the camber and suspender offset need to be superimposed to correct the arch rib alignment and control the positioning nodes. If the traditional drawing method is used, the amount of data that needs to be calculated in this process is very large, the calculation process is complex, and it is difficult to guarantee the calculation accuracy. During the parametric refinement of the arch rib, first, the catenary curve alignment of the steel arch rib is reviewed. After confirmation, the manufacturing alignment is corrected by the superposition method, the curvature continuity of the manufacturing alignment is optimized, and a smooth interpolation curve is generated according to the positioning nodes. The subsequent processes are all expanded and optimized based on the control line. The plug-in script reads and filters external table data as needed, writes processing programs using Python and C# languages, and combines with the built-in scripts of Grasshopper to complete a series of operations such as processing of segmented information, list information, data calculation, conditional judgment, and graphic drawing, simplifying the calculation and alignment drawing process, and the calculation accuracy is controllable. The program process that can be visually controlled and can quickly calculate avoids human errors during the drawing of the arch rib alignment, greatly reduces the computer memory occupancy, and also makes the batch processing logic of a large amount of curve data more rigorous, preparing for the batch processing of subsequent tree-shaped data. When there are situations such as alignment changes or segmented data changes, the input parameters of the external list can be directly changed, or the pre-data of the parametric process can be adjusted, and the subsequent parametric model will also change automatically, effectively avoiding the work of repeated drawing modification, as Figures 2-3 shown.

[0046] Step 2: Stringer Tube Modeling and Genetic Algorithm

[0047] In traditional modeling of steel tube arch pipe fittings, the "replacing curve with fold line" modeling method is mostly adopted. The straight tube model often causes the deviation of the middle node position, directly affecting the manufacturing accuracy of the bridge. However, the "manufacturing curve as curve" manufacturing mode is a major technical difficulty in factory processing. In order to meet the processing requirements of the factory while ensuring the accuracy of the bridge as much as possible, the stringer tube modeling of this bridge first adopts third-order curve single-track sweeping. When avoiding the position of the web tube and the segmented position, the genetic algorithm is used to compare the control lines of the stringer tubes, and the segmenting method of the cylinder section that is closest to the curve modeling is automatically found to meet the specification requirements that the minimum jointing length of the steel tube arch stringer tube is not less than 1000 mm and not less than the steel tube diameter, and the maximum length of the in-plant rolled tube is 2500 mm, so as to minimize the adverse impact of jointing on the structural strength. Then, the multi-surface stringer tube is redrawn according to the optimized broken line. The broken line cylinder section optimized by the genetic algorithm can be closer to the original curve stringer tube more accurately, increasing the accuracy of the bridge model, meeting the processing requirements of the factory. At the same time, the segmenting method adjusted by the program also reduces the generation of human errors and improves the splitting efficiency of the cylinder section, as Figures 4-6 shown.

[0048] Step 3: Batch Staggered Joint Adjustment of Cylinder Sections

[0049] The adjacent stringer tubes need to meet the requirements that the longitudinal weld stagger is greater than 200 mm and the stagger with the intersecting line weld is greater than 80 mm. Affected by the number of segments and the alignment of this bridge, there are many types of stringer tube cylinder sections. It is difficult to adjust the position of the longitudinal joint line of the cylinder section one by one in the traditional way, and the rotation angle of the joint cannot be accurately changed, resulting in low efficiency and high error rate. In the parametric modeling process, the longitudinal weld position of a large number of stringer tube cylinder sections can be staggered according to the preset stagger angle, and the starting point of the normal circular section is adjusted. The parametric staggered joint treatment method solves the staggered joint problems of multiple types and multiple angles, can accurately and efficiently complete the staggered joint of the cylinder section, and provides a high-precision plate edge reference line for the subsequent surface development, as Figures 7-8 shown.

[0050] Step 4: Lofting and Development of Intersecting Lines and Pipe Tangents

[0051] When pipes intersect, there will be problems with the intersection curve. The intersection curves of multi-headed pipes are often more complex and usually have no regular pattern. Between the chord pipes and web pipes of this bridge, between the chord pipes' horizontal bracings, and between the K-braced web pipes, there are all intersection curves. Before the cylinder section of the chord pipe is unfolded, it is also necessary to cut the pipe joint tangent line so that the straight cylinder sections meet the arc requirements of the extended pipe after connection. Most of the three-dimensional models of pipe fittings with pipe tangent lines and intersection curves are generated by solid cutting in three-dimensional software. This method usually cannot process solid models in large quantities. The Boolean operation speed of the computer to process solid models is slow, and the generated intersection curves are also difficult to meet the high-precision production requirements. Currently, in China, for the research on the unfolding of the intersection curves of steel tube arch bridges, methods such as equation calculation, CAD's lisp plug-in program, or intersection curve fitting method are mostly used. These calculation methods are difficult to calculate, it is difficult to find the positions of the control points after unfolding, and there are also certain conditional restrictions on the unfolding objects. Unfolding irregular surfaces by the finite element method is currently the most ideal way to solve the unfolding of intersection curve pipe fittings.

[0052] (1) Lofting of intersection curve and pipe tangent line

[0053] In the parametric process, the web pipes, horizontal bracings, K-braces and other pipe fittings of this bridge are classified and listed according to circular pipes, and the Boolean operation of the parametric model is carried out in batches. The generated model can be changed in real time. Compared with the solid model operation speed, it has increased several times. At the same time, the accuracy of the generated surface model is also higher than that of the mesh model. After the chord pipe cylinder section is segmented, after extending the large-stake-number side of the straight cylinder section, it is cut according to the end section of the small-stake-number side of the next cylinder section. The small-stake-number side of the cut chord pipe cylinder section is a flat tangent line, and the large-stake-number side is an inclined tangent line, as Figures 9-10 shown.

[0054] (2) Unfolding of pipe fitting surfaces

[0055] The surface is unfolded by the finite element method, and any spatial surface is discretized into a set of spatial triangular element folded surfaces. Considering mechanical factors, using the differential principle, any workpiece is regarded as a combination of the smallest mechanical units. The stress and deformation of the workpiece are the set of the stress and deformation on these smallest units. Since the mechanical characteristics of the smallest units are simple, the finite element method can use algorithms only for the smallest units and rely on the high-speed computing power of the computer to solve the problems of stress, motion and deformation of any workpiece. This bridge uses the incremental finite element method and combines Grasshopper script files to complete the batch unfolding of the surfaces of cylinder sections and web pipes, achieving a high-precision and high-efficiency surface unfolding effect, as Figures 11-12 shown.

[0056] Step 5: Parametric modeling of accessory structures

[0057] The inspection walkways of the steel pipe arch are arranged on the chord pipes and wind braces at fixed intervals. The inspection walkways between the upper and lower chord pipes are connected through the additional inspection walkways on the web pipes. The inspection walkways of each arch rib segment are different, resulting in a large amount of drawing work. The transition inspection walkways on the web pipes need to leave enough distance from the upper chord pipes and connect the upper ends to the inspection walkways on the wind braces. Through parametric modeling of this bridge, batch drawing of the arch rib inspection walkways is achieved, and the connection position of the inspection walkways on the web pipes can be adjusted and changed. The number and position of the layout of the inspection walkway support plates can be automatically judged, and enough space for personnel operation is left above the inspection walkways on the web pipes, such as Figure 13 as shown

[0058] Step 6: Batch processing of parts and drawing generation

[0059] This bridge has generated more than 3,100 detailed drawings. The types of parts counted in the drawings exceed 3,000, and the number of parts exceeds 71,500. If the traditional detailed design method is adopted, it will occupy a large amount of human resources and time, or may delay the construction period plan. Parametric modeling can flexibly obtain various cross-sectional graphics, or flip each graphic to the required plane to batch generate two-dimensional or three-dimensional drawings. With the help of the parametric method, operations such as batch annotation and numbering of part drawings, unit drawings, jig drawings, etc. are carried out, further improving the efficiency of the detailed design of the steel pipe arch drawings. Compared with similar projects with traditional detailed design in the past, under the same human input, the Grasshopper parametric modeling detailed design applied to the steel pipe arch has an efficiency increase of about 31% compared with the traditional CAD drawing technology, as shown in Table 1

[0060] Table 1 Comparison of efficiency between parametric modeling drawing method and traditional drawing method

[0061]

[0062] For the steel pipe arch of the Yellow River Extra-large Bridge on the Gaoqing-Shanghe Highway Project, the Grasshopper parametric modeling detailed design method is adopted for the first time. The entire detailed design of the steel pipe arch drawings is completed from aspects such as the review and drawing of the arch rib alignment, the factory processing sectional design, the pipe fitting layout and reasonable optimization of welds, the treatment of pipe fittings joints, the surface development, batch drawing and annotation, etc. It saves the time for detailed design of the drawings, improves the accuracy of parts, and effectively solves the problems such as large drawing difficulty, long time occupation, difficult drawing modification, and difficult accuracy guarantee in the detailed design of the steel pipe arch drawings, and also provides a new development direction for the detailed design of similar projects in the future

[0063] Matters not covered in this invention are well-known technologies

[0064] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention

Claims

1. The method of applying Grasshopper parametric modeling in the deepening of steel pipe arches is characterized in that: The method includes the following steps: Step 1: Conduct the alignment and positioning control of the arch rib; Step 2: Model the chord pipes and compare and optimize the chord pipe control lines using the genetic algorithm; Step 3: Batch adjustment of the staggered joints of the cylinder sections; Step 4: Lofting and development of the intersection line and pipe tangent line; Step 5: Parametric modeling of the accessory structures; Step 6: Batch processing of parts and drawing generation.

2. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 1, the catenary curve is adopted for the shape of the steel pipe arch. During drawing, the camber and hanger offset need to be superimposed to correct the alignment of the arch rib and control the positioning nodes. During the parametric deepening process of the arch rib, first, the catenary curve of the steel arch rib is reviewed. After confirmation, the manufacturing alignment is corrected using the superposition method, the curvature continuity of the manufacturing alignment is optimized, and a smooth interpolation curve is generated according to the positioning nodes. The subsequent processes are all expanded and optimized based on the control lines. The plug-in script reads and filters the external table data as needed, and a processing program is written in Python and C# languages. Combining with the built-in script of Grasshopper, the operations of processing the segment information, list information, data calculation, condition judgment, and graphic drawing are completed. The visualized control and operation program flow avoid human errors during the drawing process of the arch rib alignment, greatly reduce the computer memory occupancy, and make the processing logic of a large number of curve data more rigorous, preparing for the batch processing of the subsequent tree-shaped data.

3. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 1, when there is a change in the alignment or segment data, directly change the input parameters of the external list or adjust the pre-data of the parametric process, and the subsequent parametric model will also change automatically, effectively avoiding the work of repeated drawing modification.

4. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 2, for the chord pipe modeling, first, the single-rail sweep of the third-order curve is adopted. When avoiding the belly pipes and segment positions, the genetic algorithm is used to compare the chord pipe control lines, and the segmenting method of the cylinder section that is closest to the curve modeling is automatically found to meet the specification requirements that the minimum receiving length of the chord pipe of the steel pipe arch is not less than 1000 mm and not less than the steel pipe diameter, and the processing requirement of the maximum length of the in-plant rolled pipe of 2500 mm, reducing the adverse impact of the receiving on the structural strength. Then, several re-surface chord pipes are redrawn according to the optimized broken line. The broken-line cylinder section after genetic algorithm optimization can more accurately fit the original curve chord pipe, increasing the accuracy of the bridge model and meeting the processing requirements of the factory. At the same time, the segmenting method adjusted by the program also reduces the generation of human errors and improves the splitting efficiency of the cylinder section.

5. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 3, the requirement that the longitudinal weld stagger between adjacent chord pipes is greater than 200 mm and the stagger with the intersection line weld is greater than 80 mm needs to be met. Affected by the number of segments and the alignment, the types of chord pipe cylinder sections are more than the set value. It is difficult to adjust the position of the longitudinal joint line of each cylinder section one by one, and the rotation angle of the joint cannot be accurately changed, resulting in low efficiency and high error rate. In the parametric modeling process, the staggered joints of a large number of chord pipe cylinder sections are processed according to the preset stagger angle, the starting point of the normal circular section is adjusted, and the position of the longitudinal weld of the cylinder section is changed, which can accurately and efficiently complete the staggered joints of the cylinder sections, providing a high-precision plate edge reference line for the subsequent surface development.

6. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 4, there will be the problem of intersection lines when pipes intersect. The intersection lines of several pipe ends are often more complex and usually have no regular pattern. Intersection lines exist between chord pipes and web pipes, between chord pipes and horizontal bracings, and between K-braced web pipes. Before the cylindrical section of the chord pipe is developed, it is also necessary to cut the pipe tangent of the pipe joint so that the straight cylindrical section pipes meet the arc requirements of the extended pipe after connection. Most of the three-dimensional models of pipe fittings with pipe tangents and intersection lines are generated by solid cutting in 3D software. It is impossible to process solid models in large quantities. The Boolean operation of computer processing of solid models is slow, and the generated intersection lines are also difficult to meet the high-precision production requirements. The intersection line pipe fittings are solved by using the finite element method to develop irregular curved surfaces.

7. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 6, characterized in that: In Step 4, first, the intersection line and pipe tangent are lofted. The pipe fittings of web pipes, horizontal bracings, and K-braces are classified and listed as circular pipes in the parametric process, and the Boolean operation of the parametric model is carried out in batches. The generated model is changed in real time. Compared with the solid model operation speed, it is several times faster. At the same time, the accuracy of the generated surface model is also higher than that of the mesh model. After the chord pipe cylindrical section is segmented, the large-stake-number side of the straight cylindrical section is extended, and then it is cut according to the end cross-section of the small-stake-number side of the next cylindrical section. The small-stake-number side of the chord pipe cylindrical section after cutting is a flat tangent, and the large-stake-number side is an inclined tangent; The surface development of pipe fittings. The surface is developed by the finite element method. An arbitrary space surface is discretized into a set of spatial triangular element folded surfaces. Considering mechanical factors, using the differential principle, any workpiece is regarded as a combination of the smallest mechanical units. The force deformation of the workpiece is the set of force deformations on the smallest units. Since the mechanical properties of the smallest units are simple, the finite element method only aims at the algorithm of the smallest units and relies on the high-speed computing power of the computer to solve the force of any workpiece. The incremental finite element method and the Grasshopper script file are used to complete the batch development of the curved surfaces such as the cylindrical section and web pipes, achieving a high-precision and high-efficiency surface development effect.

8. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 5, the steel pipe arch inspection walkways are arranged on the chord pipes and wind bracings at fixed intervals. The inspection walkways between the upper and lower chord pipes are connected by adding inspection walkways on the web pipes. The inspection walkways of each arch rib segment are different. The transition inspection walkway on the web pipe needs to leave a distance greater than the set value from the upper chord pipe and connect the upper end to the inspection walkway on the wind bracing. Through parametric modeling, the batch drawing of the arch rib inspection walkways is achieved, and the connection position of the inspection walkway on the web pipe can be adjusted and changed. The number and position of the inspection walkway support plates are automatically judged, and enough space for personnel operation is left above the inspection walkway on the web pipe.

9. The method for applying Grasshopper parametric modeling in the deepening of steel pipe arches according to claim 1, characterized in that: In Step 6, more than 3100 detailed drawings are generated. The types of parts counted in the drawings exceed 3000, and the number of parts exceeds 71500. Parametric modeling can flexibly obtain each cross-sectional drawing or flip each drawing to the required plane, and batch generate two-dimensional or three-dimensional drawings. With the help of the parametric method, batch marking and numbering operations are carried out on part drawings, unit drawings, jig drawings, etc., further improving the efficiency of the detailed design of the steel pipe arch drawings. Compared with similar projects deepened in the past, under the same human input, the Grasshopper parametric modeling deepening design applied to the steel pipe arch has an efficiency improvement of about 31% compared with the traditional CAD drawing technology.

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