Civil3D Techniques for Modelling Complex Urban...

Civil3D Techniques for Modelling Complex Urban

Realm Speaker Ian Philpott – URS

CV6635

Civil3D training teaches us how to model simple corridors but what happens on real life projects? Those

corridors are rarely simple. The aim of this class is to demonstrate some techniques to overcome issues

such as irregular curve widening, urban SUDS features such as mini swales and rain gardens and

footways/cycleways that vary multiple times throughout the length of the corridor. The class will also

demonstrate how large urban piazzas, where there are no corridors, can be modelled while maintaining

the surface layer construction. Finally we will look at the workflow for large projects where data must be

split up to minimise regions to speed up rebuild times and the use of Navisworks to aggregate the data so

that the complexities are visualised and validated and relation to surrounding buildings.

Learning Objectives

At the end of this class, you will be able to:

Set-up data model structures for large or complex projects

Use offset alignments and conditional subassemblies to model complex footways speeding up rebuild times

Use dynamic tin surfaces to model urban realm formations and utilities

How to split up data for speed and merge data for presentation

Civil3D Techniques for Modelling Complex Urban Realm

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About the Speaker

Ian Philpott graduated from Oxford Brookes University in 1996 with a Bachelor’s degree in Civil

Engineering. Since graduation, Ian has worked for both contractors and consultants on a wide

variety of infrastructure-related projects. He now specialises in 3D modelling of complex

infrastructure projects and championing the use of 3D modelling and Building Information

Modelling (BIM) processes throughout a team based in 5 U.K. office locations. Ian also chairs

URS Corporation’s U.K. and Ireland AutoCAD Civil 3D Steering Group, which is responsible for

developing the standards, templates, and workflows for the use of AutoCAD Civil 3D software.

Ian has just completed Phase 1 of a £1.1 billion mixed-use development in which he used

AutoCAD Civil 3D software and Navisworks project review software to coordinate the design of

the highways, infrastructure, drainage, utilities, and external building interfaces. He has now

moved on to a major urban-regeneration project, where he is responsible for project-wide BIM

processes and model coordination across various disciplines.

@Ian_Philpott

[email protected]

mailto:[email protected]


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Introduction Civil3D is an incredibly powerful piece of software, there is nearly always a multitude of different

modelling methods to achieve what you are trying to make the software do. Yes, there are

limitations and issues but no more than any other piece software out in the market place.

Generally the limitations result from the humanoid at the mouse and keyboard.

Cast your mind back to your Civil3D training and the examples used. Now think about the

projects you work on and the modelling complexities you came across in your first project and

every project ever since. Every project has aspects that don’t fit directly in to the standard

workflows and therefore need a little bit of ingenuity and sometimes cunning to get the software

to do what you want.

When working on these types of scenarios you will do it a particular way the first time round,

typically the second time round you will find a slightly easy, better or more effective way of

modelling that particular element. The aim of this class is the demonstrate some of those

iterative technique improvements that I have developed over the last few years.

Data Structure

Folders and Backups

A good folder structure is essential to manage your data. Below is a sample of my typical data

folder structure


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The main working files sit in the root of the Civil3D folder within the project. The subfolders are

used as follows:-

Date coded folders – These contain isolated elements of work that may reference C3D

object from the main files, but main also contain new of modified C3D entities for a

particular task that you don’t want to contaminate the master files with

Backup_Models – C3D can throw the odd spanner in the works and corrupt a file, in

early versions items such as incorrectly deleted grading and small pieces of feature line

could cause issues, not to forget good old human error. In practice, when I’m modifying

files I make a backup copy at the end of the day or before I start then again at mid way

through the day. That way at the worst I will lose ½ a day of work. This process has

saved my skin on many occasions.

Export – As part of a BIM process we share data with other disciplines, commonly

Civil3D data is shared with Revit users. These two pieces software don’t integrate as

smoothly as they could. It is therefore necessary to export data rather than read data

from the same file1. This folder is a container for these exports so as to keep track when

and from which version of the master file they were extracted.

Import – We accept data from a variety of sources, including Surveyors, Architects etc.

This folder is where I store any data from other disciplines or consultant that I have

referenced or used to build any part of the Civil3D model.

Model Reviews – This folder is used to create dummy files that reference in data from

the masterfiles and are used for design verficiation. For example, using a different

technique to check volumes produced by earthworks models or checking buildability of

complex junctions where the pavement overlay is required.

Superseded_Models – Repository of master model files prior to modifications. Your

Project Execution Plan (PEP) should outline what constitutes a change that requires

models to be superseded or at what stage of the project a model should stored as

superseded before progressing.

Temp – As the name suggests it’s for temporary models, maybe you need to try a

modelling technique or a particular modification without risking the master file. Nothing

contained in this folder should form any part of a deliverable or be referenced in to any

other file

1 Refer to CV6086 - What Do You Get If You Cross 1 Engineering Consultant and 9 Architecture Practices for more

information on the transfer of data between Civil3D and Revit in practice


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Data from Other People

When building infrastructure models we are reliant on data from other people. Everything from

topographical survey data, utilities information through to the new buildings. Managing this data

is an essential skill, particularly as the process of incorporating much of the data is a manual

process. Therefore, maintaining control and ensuring that we know what revision or version of

the data is being used in the Civil3D model at any time.

Splitting Large Projects in to Manageable Pieces

Large projects need to be split in to multiple model files for a number of reasons:-

Resourcing – We never have the luxury of enough time to allow one person to do all the

modelling on a project. Split models allow more people to work on part of the model

simultaneously.

System Performance – As model size increases system performance decreases.

Civil3D has a lot of background processes rebuilding surfaces and points when files are

opened or when particular actions are performed.

Model Reliability – What happens if the worst happens and your file becomes corrupt?

Breaking up the data and a reliable backup procedure as outlined above will reduce the

likelihood and limit the impact in the worst case scenario.

How do you decide how to split the models? Well that’s project dependent and a number of

factors have to be considered including but not limited to programme, size, scope and

complexity. On a typical development project I would split the models as follows:-

Existing ground model and geotechnical strata

Road alignments and corridors split in to multiple files if needed, selecting convenient

points where corridors can be broken at points perpendicular to the alignment.

Proposed building platforms and earthworks

Utilities and drainage split by utility type on larger projects


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Object Naming

Object naming is critical for many reasons. It’s very easy to skip over this task and allow the default naming from the template e.g. feature line 1 but what happens when you don’t work on the model for a few week, months or even year or someone else takes over the modelling tasks. It does happen. In addition to basic professionalism why should we care about object naming?

Model clarity – Models are now not only used internally they are now shared with other

parties, for example a contractor. Give them half a chance of understanding of how the

model is constructed and which objects are relevant to them.

Data extraction – As the use of BIM processes increases reuse of data is more

important. Data extraction for purposes such as quantity takeoff will increase, without a

consistent and logical object naming strategy this data will be useless.

Navisworks search sets – Federating models is key to coordinating multidisciplinary

projects. Search sets within this software is a fundamental element of the clash

detection process, therefore consistent object naming not only ensures that all the

correct elements are located by the search set but also allows the search sets to be

saved and reused on other projects.

Below is an extract of our standard for naming pipe network objects within Civil3D. This convention is typical throughout our naming protocol, it comprises and type which varies depending on the object, an identifier and a descriptor if required.


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Urban Realm with Corridors

We can all model simple corridors with regular width roads and standard footways. Urban

realm, particularly in the UK is rarely simple. Spatial constraints, urban design and Manual for

Streets 2 (UK urban design code) can all result in varying road widths, sinuous geometry and

urban realm geared more towards pedestrians and cyclists than vehicles.

The examples I’m going to show are based on a recent project where the client was looking for

a high class urban realm. They may look simple at first appearance but there are technical

difficulties in terms of how these are modelled in Civil3D.

Curvy Laybys

The curvy layby (shown below) requirement was primarily a driven by the highway authority who

didn’t want any “dead spots” where the mechanical street cleaner can’t access. The primary

modelling challenges that needed to be resolved where as follows:-

Resolution of the level differential resulting from the kerb height and footway fall adjacent

to the layby relative to the layby front kerb height, crossfall and back kerb height.

Transition between standard kerb (125mm upstand) prior to the layby and around the

back of the layby where it interfaces with the layby front kerb (25mm upstand).

How the footway behind the layby can be modelled when the alignment of the layby

curves in such a way that the assemblies insertions would overlap causing “bow ties”

and thus issues with the corridor and surface.


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A number of iterations of the model were needed before we were able to get the model to

accurately represent the required layby and footways. Outlined below is the process we used to

achieve the final result.

Step 1 – Create an offset alignment and profile for both edge of carriageway and the layby. The

edge of carriageway can be created either using the offset alignment tool on the alignments

contextual ribbon, if simple, or designed if more complicated. The layby alignment will need to

be designed. Profiles will also need to be created for both, again these can be designed or by

creating dummy assemblies and temporary corridors that extend beyond the alignments and the

applying a surface profile to alignment. I found this the most effective method.


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Step 2 – Create the four assemblies you need, layby, footpath (including kerb), kerb only and

layby fillet. I will explain more about the last one later on in the process.

Step 3 – Create a corridor for the footway area, adding regions either side of the layby.

Footpath Layby

Layby Fillet Kerb Only


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Step 4 – Add a baseline to your footway corridor using the layby alignment then add a region

along the centre section of the layby.


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Step 5 – Infill the start and end curved sections of the layby with regions using the kerb only

assembly and a close frequency (0.1m). This leaves gaps in the back of footway feature line

which is unavoidable but the surface contours do carry over.


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Step 6 – Add the edge of carriageway alignment as a baseline for the road corridor and then

add a region using the layby sub-assembly. Don’t forget to set the targets and frequency. At

first you will see the contours go a bit mad because of the little wedge at the end where the kerb

along the front of the layby is wider than the gap. This is where the layby fillet assembly come

in. Split your layby region where the back of the kerb cross the layby alignment, then replace

the assembly with the layby fillet one and reset your targets and frequency.


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Mini Swale and Rain Gardens

Sustainable Urban Drainage Systems (SUDS) are an essential part of urban realm design. In

the UK, where space is more limited than in North America, SUDS features have to be smaller

and adjusted to fit in spaces between all of the other streetscape items. Linear features such as

swales that run down long lengths of road are easily accommodated in corridor models. Mini

swales and rain gardens that frequently stop and start along the corridor adds complexity to

modelling urban realm.

Due to the stop / start nature of these features it is not possible for them to be modelled using

just regions and assembly switching, some form of manual intervention is required. The most

effective process I have found is mostly manual, the disadvantage being if anything changes

then more manual adjustments are required but the advantages being that the levels in the

surrounding can be optimised and the swale effectively pasted in place later in the workflow.


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Step 1 – Create the road and footway in the normal way, using a conditional subassembly to

switch from a standard footway to an assembly containing a verge


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Step 2 – Create feature lines that represent the top and bottom of the ditch and use the

“elevations from surface” to set levels on both the top and bottom of ditch from the proposed

footway levels.


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Step 3 – Select the ditch base and then from the ribbon select the feature line elevation editor to

move the ditch base levels down by the required amount.

Step 4 – In Prospector open your surface, go to definitions and add the two feature lines to your

surface. Bingo, one swale added to the corridor surface.


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This method is fine for the finished surface but how do you translate this surface in to the

formation model. Well, that depends on the shape of the formation relative to the surface but

essentially there are three options

Create another set of feature lines for the formation. Disadvantage being they are not

linked to the top surface so all updates would be manual

Create a formation surface for just the swale by pasting the finished surface in to a new

surface, adding a boundary to trim it to the swale extents then select the surface and

from the ribbon select edit surface and raise / lower surface. The will only work if the

formation follows the finished surface at a constant offset.

If your formation is more complex but you want to retain a dynamic link between it and

the finished surface then there is a way, called a dynamic differential TIN. This is a

technique I learned at a class back in my first year at AU in 2012. Look up CI3906 - The

Magic of a Dynamic Differential TIN Surface.

Utilities

Underground utility infrastructure is the biggest co-ordination challenge faced by the Civil

Engineer. Connections to buildings, depths of cover changing depend on whether they are in a

trafficked area or non-trafficked area and the limited space of the UK all add to the complexity.

How can we use Civil3D in conjunction with Navisworks in a dynamic way to build utility models

quickly and eradicate the inevitable clashes that will result? Here’s how.

Step 1 – Building your pipe networks in Civil3D and set the utility depths based on your local

standards (NJUG for the UK)

Step 2 – Instead of using the NWCOUT command in Civil3D to create a Navisworks file, open

Navisworks and append the Civil3D model file directly. It will look a bit messy as all the

alignments and labels will be shown but these can be easily hidden using the selection tree.

Why this method? NWC files can’t be saved over while Navisworks is open where as

appending the .dwg allows you to change the Civi3D model and refresh the content in

Navisworks without closing any files.

Step 3 – Create search sets for each of the utilities, this is where clear object naming in the

Civil3D model becomes so important. These object names can be used to create your search

sets or even import a standard search set based on your standard naming. You can then use

appearance profiler to colour the utilities to aid identification of clashes

Refresh Data Sources


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Step 4 – It is now time to go and hunt out those clashes. There are two methods. Method 1

being a simple visual inspection this works fine for simple schemes. Method 2 uses the

Navisworks clash detection tool. Here comes your search sets again use them again to define

your clash detection tests. Now you see why object naming is so important.

Step 5 – Now back to Civil3D, modify your pipe networks then go back to Step 2, hit refresh and

repeat Steps 3, 4 & 5 until your clashes are resolved.

**This was a quick tour through this functionality. Don’t worry there is more to come in the class

presentation**

Urban Realm without Corridors Much of the urban realm is made up of building forecourts, squares, piazzas, ramps and steps.

These urban features don’t lend themselves to being modelled as corridors so other methods

have to be used. However, not using corridors means that the formation model isn’t available

like it is in a corridor based model. As earthworks volumetrics are a significant part of the Civil

Engineer’s works these formation models are as important as the surface model. How do we

overcome these issues?

Design Piazzas to Control Overland Flow

Piazzas are a common feature of the urban environment. There are a number of challenges to

consider when modelling them, particularly the followings:-

Overland flows – The design must consider the passage of water in extreme rainfall

event, channelling it away from building thresholds

Falls – Must be steep enough for effective drainage and create areas that are low

enough below the surrounding levels to contain and channel overland flows but shallow

enough to be compliant with requirements of disability access standards.

Features – These areas are full of features, underground bins, tree pits, SUDS, utilities

and street furniture. They all need to be considered in the modelling process.

Surface Changes – Changes in surface finish are common. These often have different

construction thicknesses and are often in irregular shapes. Accurately picking up this

information in the formation model is key.

**This topic is going to form the backbone of the presentation at AU. The background above will

give you a flavour of the key issues. A copy of the presentation plus the dataset will be made

available after the presentation**


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Bring it Back Together Once the design work has been completed in the manageable sections as outlined above, its

necessary to bring the data back together for such tasks as earthworks calculations. These

models can also be federated with information from other disciplines using tools like Navisworks

for the clash detection and visualisation.

Navisworks

Navisworks is a key tool in the Civil Engineer’s armoury. If you haven’t used it before take a

look. Basic usage of the software is quick and simple to pick up, once you have mastered the

basics the power of the even the simple visualisation is a huge advantage. Master the clash

detection, appearance profiler and sectioning tools and you have a strong toolkit that can be

applied to many projects and scenarios.

Based on the utilities example you will start to see why some of the earlier topics are so

important, particularly splitting the project in to manageable sections and object naming. These

are key to how the appearance of objects is controlled within Navisworks as well as the search

sets which drive the clash detection tool and appearance profiler.

In my experience Navisworks has proven to be a valuable communication tool, particularly with

non-technical clients who find the array of lines, contours and tables on a typical civil

engineering drawing hard to follow.

In the class presentation I will show you some of the tips and tricks of using Navisworks for civil

infrastructure projects and why it just as valuable for civil engineering as it is for buildings and

MEP.

Summary This was a whirlwind tour of some of the key aspects of urban realm modelling. These techniques can be applied to most projects. What are the key points to take away and apply to other projects:-

Plan your data management process, structure and requirements before you start creating data.

Look at the project scope, layout and complexity and decide where and how your models need to be split up.

Be clear on your object naming protocol as you will need it later on in the process.

Practice and building on the techniques used to model the complex area so they can be applied to your projects.

Make use of the power of Navisworks in conjunction with Civil3D from early in the design process, not just at the end for review.

Civil3D Techniques for Modelling Complex Urban...

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