civil3d techniques for modelling complex urban...
TRANSCRIPT
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
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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
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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.