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CL124915

Automated Design and Production for Linear Schemes Using AutoCAD Civil 3D, Revit, and Dynamo Jerome Chamfray Atkins BIM Manager Peter Houlston Atkins Geotechnical Engineer Ian Mcgregor Autodesk Ltd Snr Implementation Consultant - BIM

Description

A linear structure is related to and controlled by a 3D alignment. This class will cover case studies of some typical design elements (such as gabion walls and tunnel cross passages) that may need to be incorporated to deliver the scheme design. We discuss the problems that Atkins has had to overcome, and the various approaches chosen to achieve the goal of programming rule-based algorithmic geometry selection and placement, from guide lines for the linear structures, in response to iterative design alterations. Atkins has developed a solution for automated linear structure design and drafting. This futuristic digital engineering approach delivers significant design efficiency, and it reinforces Atkins’ leading status in the field of digital engineering. This class will share the processes adopted for the solution using AutoCAD Civil 3D software, Revit software, and Dynamo software. Come and be inspired by how Atkins works cheaper, faster, and smarter while further enhancing the quality of deliverables.

Speaker(s)

Jérôme Chamfray is BIM Manager at Atkins. He has 17 years’ experience of leading 3D design and engineering drawing preparation for major projects involving earthworks, tunnelling, infrastructure and building projects. His current focus is on the further development of BIM and Digital Engineering approaches for Atkins Ground Engineering and Tunnelling projects. He’s expertise is centred on BIM, data management, drawing production and ground modelling using AGS geotechnical data combined with 3D spatial information. He is an experienced user of Civil

Learning Objectives

• Discover the process of defining the business logic needed for Dynamo design rules

• Discover the benefits of using Dynamo in linear structure design

• Spot opportunities for the application of a rapid prototyping environment to solve a design problem

• Learn how to rapidly visualize the impact of design decisions and options

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3D, HoleBASE, AutoCAD and has GIS experience. Further to the application of his experience, he has developed a parametric modelling approach on Linear schemes resulting in large time and cost savings. His wide range of expertise and valuable knowledge have led him to be identified as a technical expert on large multidisciplinary projects in South Africa, Middle East and the UK. He is also Atkins’ Technical Authority on sub-surface digital engineering. Peter Houlston is a Geotechnical Engineer based in the Birmingham office of Atkins Ground Engineering team. Peter has a wide variety of experience, from numerical modelling of cutting heave in new build railways projects to specification and interpretation of advanced laboratory testing to characterise the response of driven piles in chalk. Recently, his focus has turned to application automated design processes to geotechnical engineering design. Ian McGregor is senior implementation consultant within the Building Information Modelling (BIM) service line at Autodesk, Inc. He is focused on assisting customers deliver BIM transformation within the infrastructure industry. He has extensive experience managing requirements for large and complex projects, and delivering across multiple engineering standards and languages. He also provides consultancy on BIM process definition and standardization for transportation, airports, and water industries.

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Contents Learning Objectives ................................................................................................................... 1

Description ................................................................................................................................. 1

Speaker(s) ................................................................................................................................. 1

Discovery of business challenge ................................................................................................ 4

Background ............................................................................................................................ 4

Discovery process .................................................................................................................. 4

Training .................................................................................................................................. 5

Challenge 1 – Gabion Wall design ............................................................................................. 5

Gabion wall design – Highways example ................................................................................ 5

Design Process ...................................................................................................................... 6

Business value ....................................................................................................................... 6

Challenge 2 – Tunnel Cross Passages ...................................................................................... 7

Design parameters ................................................................................................................. 8

Design process ....................................................................................................................... 9

Business value ....................................................................................................................... 9

Solution Approach .................................................................................................................10

Python and CivilPython .............................................................................................................11

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Discovery of business challenge

Background Atkins have a long history in ground engineering and many current linear infrastructure projects that incorporate linear structures such as tunnels, retaining walls, bridges and viaducts. Examples would be Crossrail and the High Speed 2 projects. Our senior leadership have given a mandate down to the design teams to embrace digital design methodologies. This means going beyond electronic drafting and CAD and is now being interpreted as needing a degree of automation and an algorithmic approach to design. Atkins’ analysis of current design practice showed that there were many areas of the design process that involved a lot of manual input of data typically involving inefficient exchanges of information. Often these exchanges required manual interpretation and transformation of information into a suitable format for the next step. We had heard about the linear structures class at AU in 2016 and decided to initiate a project with Autodesk to explore developing both processes and technology for the coordinated design of tunnels, viaducts and retaining walls across our ground engineering design disciplines involving highways, structures and tunnelling teams. This talk is showing you some of the results of that project and things we learned along the way.

Discovery process We held a two-day workshop with Autodesk to explore our existing business processes. These workshops centred around two typical problems we had already identified as having opportunity for innovation and automation due to involving a lot of manual design processes. The problems were especially impacted by changes to the highway/railway alignment. The two design processes we explored were:

• Gabion wall design, and

• Tunnel cross passage design. Each of these design processes is detailed here in this handout. In the interactive workshops, we listed each of:

• Design criteria and parameters,

• Stakeholders in the process,

• Inputs to each step,

• Outputs from each step,

• Deliverables requirements, and

• Approval flow. We then mapped these into a flow diagram and identified the steps that were slow, difficult and repeated often.

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Training Autodesk presented the Dynamo CivilConnection package and whilst our engineers are generally experienced in programming or scripting tools (especially Python), they had no knowledge of either Dynamo or Revit within the ground engineering team. Before undertaking an attempt to solve our challenges some Dynamo and Revit basics were taught in a Dynamo upskilling workshop. The team also took themselves through basic Dynamo tutorials online such as http://www.dynamoprimer.com Given the team’s proficiency with Python, they adapted to the upskilling more quickly than anticipated and by the 3rd day they were ready to start trying to integrate Civil 3D with Dynamo and solving the real-world problems rather than the hypothetical training examples.

Challenge 1 – Gabion Wall design

Gabion wall design – Highways example Atkins have a good process for the first stage of preliminary design in place already. This approach in Civil 3D solves for a generic location problem of where gabion walls are needed by utilizing corridor modelling techniques with a custom subassembly. This process does not do the precise engineering logic of where to provide the gabion baskets, just provides an indicative location. The design of gabion walls at multiple locations becomes a tedious manual task with no chance for optimization or data to support the final engineering design. This gabion design is then susceptible to changes in the highway alignment potentially leading to re-design and starting over. Tasks like quantification and drawings production become disconnected, this has meant that much of the detail design has been delegated to the contractor.

Design parameters Below are the design steps discussed in the workshop for each of cut and fill scenarios that we would like to test with a Dynamo design. The gabion basket models will be created as parametric basket objects for various types defining the range of baskets available.

Figure 1 plan, section, elevations. SMP gabion wall design. Cut & fill situations

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key points to note • Red dots indicate Civil 3D feature lines

• ‘H’ is maximum height of gabion wall

• ‘width’ indicates max width to boundary line of site

• There is an embedded depth value of the gabion wall below bottom of bank

• There is a max height at top of bank the embankment slope can over top the top gabion

• Want to maximise the size of gabion basket used

• Minimum number of gabion baskets in a wall

• Min distance to boundary now at foot of wall in fill situation

• Slope definitions differ slightly in the fill situation

• There are minimum and maximum values that gabion baskets can deviate from plan boundary defined by C3D FL’s

• Earthworks slope definitions are provided by Civil 3D

• There is a cost efficiency preference to place larger baskets

• Would like to build a Civil 3D surface of the final array design by extracting an array of points into a C3D surface object. Allows for volume calculations in Civil 3D later.

Design Process 1) Civil 3D provides feature line inputs for top/bottom of slope and boundary line.

2) Parametric Gabion baskets controlled by Dynamo (likely 10 types)

3) Civil 3D provides the cut/fill case

4) Decision to use gabion wall or some other construction method e.g. sheet pile

5) Place array of baskets in available space based on

a) Available width

b) Maximum height

c) Embedment in base

d) Maximum surcharge and batter slope values

e) Maximum height of surface above the top cage

f) Maximum height of basket above surface 6) Export setting out data in appropriate format for on-site placement of cages (poss. Civil 3D feature lines) 7) Obtain surface area of gabion wall 8) Enable drawings production (place 3D solids of gabions) in Civil 3D 9) Enable QTO a. Basket schedule

a) b. Volume of stone

b) c. Volumes of infill/cut

c) d. Area of geotextile blanket across the back of the gabion wall baskets

Business value Why we wanted to explore automation of the design of gabion retaining walls

• Automates decision on when to place gabion vs other retaining wall solutions

• Optimise the gabion wall geometry and placement

• Provision of a precise gabion schedule would be a new service Atkins could provide in the design delivery

• Minimise cost

• Creation of Civil 3D surface for more precise volume calculations

• Speed of response to design change

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Figure 2 wireframe of gabion wall array placed in AutoCAD by Dynamo

Challenge 2 – Tunnel Cross Passages

Cross passages provide points of access between two parallel running tunnels. They are utilized for purposes of maintenance, emergency and ventilation. In general, the challenge is to set out the geometry of the cross tunnel between two related main running tunnels.

The spacing of cross passages is defined by business rules and will be project specific. The geometry of the cross passage has some specific parameters and is governed by its relationship to each of the running tunnels. Usually it will be defined by an alignment (2D horizontal plane) and profile (2D vertical plane.)

Each cross passage will be unique due to its relationships to the running tunnels and other cross passages as well as geology at that location. Planned construction method will also have an impact on geometry.

Design model geometry is non-trivial to solve by current methods and prevents significant optimization of design due to time constraints.

Reinforcing rock bolts around the entrance to the cross passage from the main tunnels are especially complex to design and install due to possibilities of them clashing. There would be added value in being able to design these and produce schedules of hole location and drill angle.

Steel reinforcing design is also similarly complex and would benefit from some automation.

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Figure 3 sectional views of tunnel cross passage design

Design parameters Cross passage design should accommodate:

• minimize length of tunnel,

• maintain a slope for water egress back to running tunnel,

• be related to walkways in main running tunnels,

• maintain space requirements defined by cross section,

• Contractors need a schedule of drill locations,

• Drilling is imprecise so a tolerance cone is needed, and

• Clash avoidance is better than clash detection. Solution should avoid or advise of clashes and allow for redesign.

Figure 4 rock bolt design related to cross passage

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Design process 1) Alignments and profiles from C3D 2) Track, train and tunnel design data inputs 3) Pedestrian walkway geometry located 4) Locate cross passage by chainage 5) Minimise length of cross passage 6) Main running tunnel low point is a consideration (sumps and pumping) 7) Consider geology in location 8) Automate profile geometry? With minimum / maximum profile grade (e.g. min 2.5%) 9) Apply a C3D subassembly for cross passage size (clash checking)

Business value Why we wanted to explore automation of the design of tunnel cross passages

• Optimizing the placement and number of cross passages is of high value. They are expensive to design and construct.

• Automated production of sectional drawings related to cross tunnels would be a win for this project. That is a non-trivial present day manual task.

• Ability to test tunnel geometry with short response times should support engineering decision making and optioneering due to increased data availability. Some high level decisions today are made based on engineering judgement because modelling takes too long or is seen as impractical due to high manual effort or skill level.

• Better space planning for utilities in cross passages

Figure 5 Tunnel cross passage geometry in Dynamo, with rock bolt design

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Solution Approach A perception exists that Dynamo is part of Revit but due to low understanding of the value that Revit could bring to the modelling challenges it was worth explaining the modelling environment architecture. Dynamo is just an environment that is initiated from Revit in order to access the Revit API. In reality, what the system provides is a dynamic modelling environment of its own that can read/write from many sources, Civil 3D and Revit are just two special cases.

Figure 6 comparison of Civil 3D : Dynamo : Revit software architecture and in use modelling architectures

The Autodesk CivilConnection Dynamo package is a custom package that loads into Dynamo and provides a live connection to Civil 3D via the Civil 3D COM API. Dynamo provides a visual, interactive, programming environment in which to prototype design. It is not constrained to working just with Revit data.

A key feature of the installed nodes is to allow the loading of Civil 3D corridor model information into Dynamo in such a way as to establish a useable linear coordinate system in the Dynamo and Revit environments. This means that location can be expressed in terms of an Alignment, Station (Chainage), Feature Line reference, offset and elevation in addition to the rectangular Cartesian and polar systems.

For example, the location of any gabion basket can now be expressed in terms of a location relative to the main road alignment, or associated feature line, and if that alignment changes then the basket location can be reset but maintaining the already established relationship.

This location based relationship is fundamental to solving the design challenge. Civil 3D provides the bounding space in which gabion baskets are required. The Dynamo toolkit provides the ability to explore, prototype and optimize the three-dimensional array of baskets.

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Python and CivilPython

For the use cases we were exploring we actually did not need much of the core functionality of Revit. Our deliverables on the projects were all AutoCAD and Civil 3D based. We needed to take the Dynamo created geometry and put the results back into AutoCAD.

Some of the processes we were trying required the creation of Civil 3D objects , such as surfaces and Property Set definitions, that are not available via the Civil 3D COM API1. In order to gain access to these features another approach was needed.

Python, https://www.python.org/, is a widely used programming language whose popularity has a lot to do with its style of syntax. It's highly readable, which makes it easier to learn than many other languages. Python supports modules and packages, and can be embedded into existing applications. Dynamo includes a Python scripting node and our team are familiar with Python. Python was a natural direction for Autodesk to explore to solve our issue.

By writing a small DLL called CivilPython, based on the same IronPython 2.7 that is present in Dynamo for Revit, that could be invoked from the AutoCAD Command Line we can put AutoCAD into a wait state. In this state, AutoCAD is waiting for execution of a named Python script. This script will be in process with AutoCAD which means that Python has access to the full Civil 3D .NET API feature set and can therefore carry out the actions we needed. Once the script finishes, the AutoCAD command ends and control is passed back to the Dynamo script.

Figure 7 sending python command to Civil 3D

The scripts can access the .NET API in Civil 3D and take advantage of the automation framework.

Python scripts consist of text files with a “.py” extension and can be developed with any text editor. Changes to the code can be made on the fly, simplifying the prototyping process. In case of failures and during debugging, a message prompts the user to show the line in the code that requires attention.

1 [Background technical note: Microsoft COM (Component Object Model) was the technology that Civil 3D first implemented to provide an API. COM has been replaced at least to some extent by the Microsoft .NET framework, However COM allows for out of process communication between applications, whereas .NET does not. Since Dynamo is out of process with Civil 3D the CivilConnection package is constrained to the older COM API further info at https://en.wikipedia.org/wiki/Component_Object_Model]

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Calling “Python” at the Civil 3D command line will activate the user interface of the command to guide the user in selecting the script to execute.

Calling a “-Python” at the command line, with a dash in front, prompts the user for the path to the script to execute in the command line. It is possible to call any Python script directly from Dynamo via the CivilConnection node CivilDocument.SendCommand, providing the document in Civil 3D and the file path to the Python script to execute.

Data can be processed in Dynamo and then passed as an argument for the Python script via command line in Civil 3D, for example as a JSON string that is deserialized in the script, or dumped to a CSV file and read in the script using the default Python libraries. It is up to the script owner to decide how to consume which data, with which structure, and in which format.

Example: Manage Property Sets via CivilPython We were very interested to explore management of asset information tagged on model elements using the Civil 3D Property Sets feature.

With CivilPython it is possible to write a script that accesses the objects in the Civil 3D model and gets or sets their Property Set values.

We explored writing Python scripts to store Property Set values in CSV files by searching selected model elements for the Property Sets names and extracting their definition data. This was used to build a schema in Excel, select the Civil 3D objects via their handles, insert data on the selected objects, and update their Property Sets values.

This meant the end-user does not have to have Python or API skills but can still benefit from these scripts as they only have to select the scripts using a standard dialog manage the data in the CSV files and let CivilPython take care of the rest.