Further to my post about Universal Shared Parameters, we were questioned about why we needed such very structured data in our authoring environment. Why couldn’t we use the limited IFC properties available for our parameter names, or make do with IFC parameters that have TEXT or LABEL datatypes, or indeed use the Shared Parameters provided by National BIM Library. The answer is that if you want to unlock the true power of the data in BIM, the data has to be much better structured than those schemas accommodate.
Example 1 – IFC4 properties
Here is an example of how IFC4 handles Reaction to Fire (Surface Spread of Flame):
This entire definition consists of a property name, a data type, and a description (in several languages). The crudeness of referring to a nebulous ‘national building code’ is a good example of a bad starting point.
Do we use BS or EN values?
EN values are in 3 parts: class, smoke, droplets. How are they handled?
Is this a limiting value, if so a max or a min?
Is this a manufacturer’s value? How does it relate to the limiting value?
Is this value certified, if so by which body?
It’s clear that if you really want to document Reaction to Fire of an element, you’re going to need a bunch of parameters, OR maybe fewer parameters from a schema that declares these criteria. Neither IFC nor NBL parameters are fit for this purpose.
This post began not so much as a blog piece, but more a means of contributing to a discussion that isn’t limited to 140 character chunks…. (fix it Twitter!). I’m happy to be corrected / contradicted using the comments section, or back over on Twitter @pumphousebim
There is currently a healthy discussion on Twitter about the best way to resolve the ‘Shared Parameter Problem’. Although this is Revit terminology (and I will largely use Revit terminology throughout this post), this is part of a broader BIM discussion.
The problem is this – there is no universal list of Shared Parameters for the construction industry, either in the UK or worldwide. People may try and tell you otherwise, usually people who aren’t day-to-day Revit users – believing that COBie or IFC or National BIM Library (NBL – a UK body) offer a solution to this. They don’t.
This matters because – without Universal Shared Parameters, BIM in Revit doesn’t work very well. Conflicting lists of Shared Parameters, used by conflicting object publishers, cause massive problems for users and BIM Managers, problems which are passed on to Contractors, Subcontractors and Clients
We recently completed the Innovation Centre at Infinity Park in Derby, with Main Contractor GF Tomlinson. Built for Derby City Counciland been christened the ‘iHub’, the building will open this summer. It was a Level 2 BIM project with the main ‘Tier 2’ subcontractors required to model their packages for federation with the ‘Tier 1’ models. This case study looks at how Varla (UK) modelled the complex cladding and roofing package.
The building is curved on plan as well as on elevation, which meant this was going to be a challenge even for an experienced modelling team. Varla turned to Jon Sheridan of e-DNAwho they’d worked with previously on Zaha Hadid’s Glasgow Transport Museum.
Jon had a lot of experience modelling for cladding fabrication using Rhino with Grasshopper, but modelling as part of the BIM process was new. The first question the design team had to answer was what format could we all work with – the obvious answer was IFC. The great thing about IFC is that it can be federated not just in review software (e.g. Navisworks or BIMsight), but can also be loaded into authoring packages such as Revit, which the design team were using.
The Varla subcontract package had a number of elements that all needed to be modelled:
Insulated carrier panels (used instead of an SFS system)
Rainscreen support system (Lingrid)
Aluminium Rainscreen cladding
Stainless steel shingle cladding
Topdeck roofing system
Jon modelled each of these elements separately in Rhino and provided separate IFCs to the design team. The model was further split between areas of the building. This meant the large model size could be broken up into discrete chunks which could be loaded, and more crucially unloaded, separately.
To generate the geometry in Rhino, Jon used the Grasshopper visual scripting package. This allows you to great scripted definitions of the desired geometry which are then generated in Rhino. Parameters such as cladding module, depth, profile and 3 dimensional paths can all be defined within the script, and can be iterated as required. Dynamo for Revit works in a similar way, but Jon believes the nurbs features of Rhino are superior for this type of work.
To then turn Rhino models into IFC for the design team, Jon used plug-ins available from Geometry Gym, a blog/company run by John Mirtschin. ‘GG’ can turn the Rhino geometry into a series of lightweight extrusions in IFC format, and also supports data added to the geometry.
Once the design team received the IFC cladding models, our preferred federation approach was to link the IFC files directly into Revit. Our process is more one of coordination than clash detection, and the automated clash tools of applications like Navisworks can be more of a hindrance than a help. Using the hundreds of saved views, sections, and section boxes already set up in Revit, we were able to check for alignment, clashes, errors and comment on module arrangement options very easily.
The size of the subcontract models means they couldn’t all be loaded at the same time, with current computing power, but this was a valuable exercise in getting subcontract design models into the BIM workflow processes.
You can find more example of Jon’s work in BIM, industrial design, automotive design and even yacht design, over at his website e-DNA.co.uk
Rob Jackson over at Bond Bryan’s BIM Blog published a useful post earlier, about how to produce your TIDP inside ArchiCAD. I’ve shamelessly repurposed Rob’s hard work and done the same inside Revit.
What’s a TIDP?
Ah, that’s another one of those BIM acronyms for something we’ve been doing for years anyway – it’s a kind of Information Release Schedule: a list of all your drawings (and other documents) and the dates you’ll release them. You’ll find the requirements in your BIM Execution Plan (BEP) if you’re following PAS1192-2.
Revit Sheet Lists
Revit’s Sheet Lists are like the drawing registers of old, they’re a list of all your ‘drawings’. Whenever you add a new Sheet in a Revit file, it gets added to the Sheet List. These are great, but note that Revit doesn’t produce Issue Sheets or Transmittals (without a lot of hacking). You can turn a Sheet List into a TIDP though, just by adding a few Shared Parameters.
Adding Shared Parameters
If you’re following BS1192 document naming, you’ve probably already worked out that you need to add a Shared Parameter (SP) for each of the 7 fields which make up the file identifier. You need an SP, added to the Sheets category, for Volume and Level for instance. You’ll also need an SP added to the Project Information category for Originator and Project Acronym. All of these SPs and their data can be added to your Sheet List, and to your Title Block as below. (Ours is slightly customised to allow us to use our internal project numbers, which is fine as long as you write it into your BEP).
To make a TIDP, you’ll need several more Shared Parameters. Add one for Exchange Format, and add one for each date column you want in the TIDP, called Delivery Date Milestone 1, Delivery Date Milestone 2 etc. Put those SPs on your Sheet List and you can enter your release dates right on the TIDP. The milestones are typically the new RIBA workstages (0-6, you won’t need 7).
You can make Placeholder Sheets in Revit, which is something you’ll want to make use of. You prepare your TIDP at the start of a job, when the Sheets don’t actually exist. Just go to your Sheet List or TIDP, and Insert Data Row to make a Placeholder Sheet. When you come to need the Sheet further down the line, just choose the Placeholder Sheet from the list in the New Sheet dialog.
Each year after Autodesk University the company start on a tour of all their developer communities around the world. In recent years Autodesk have encouraged users, not just developers, to attend and also this year organised an evening Meetup event on Tuesday 9 December, the day before the main developer event in Farnborough.
Organised via the website meetup.com events are defined as, “…getting together to learn something, do something, share something…” and this reflects Autodesk’s idea of an open event with, a limited pre-planned agenda, at which to share technology that spans the Maker hobbyist community to professional design and simulation software.