Executive guide to BIM: part 2
The second installment of this two-part guide (Read part one here)goes into greater detail on Building Information Modelling (BIM) workflows, when a model progresses from concept to construction and facilities management. We cover the benefits and implications of adopting BIM, including changes to teams and workflows.
Having looked at levels of Building Information Modelling (BIM) and dimensions of information in the first part of this guide, the third factor to consider is the level of detail or level of development (LOD) contained within the model. Both terms mean the same thing and aim to clarify the expectation in terms of information granularity. These LODs are often linked to time and stage of work with a model progressing from concept through to construction and facilities management (FM).
There are two strains that have developed independently, either side of the Atlantic but have matured into near alignment. Table 1 (top page 23) compares and contrasts the two.
In table 2 the two standards diverge slightly as the purpose of the LOD is interpreted differently with the AEC terminology looking to differentiate between the geometric simplicity that is acceptable for general draughting purposes versus the complexity required to produce quality rendered images.
The majority of design work is carried out in the first three LODs where the terminology is interchangeable.
This terminology is important because it may have a major impact on the quoted price of a job and a detailed scope should go much deeper in specifying what scale and at what stage certain elements will be defined and in what dimension.
The following practical example may help to clarify: For the next delivery deadline, all pipes above ## will be modelled in 3D. Pipes between ## and ## will be shown schematically in 2D. Connections below ## will not be shown.
A succession of these types of statement will clarify, without ambiguity, the extent to which the model is expected to deliver on clash detection and to what extent the final fixtures are connected by the skilled fitter on site.
Only the first part of this scope is BIM with the second part being a CAD workflow and the third being blind luck.
This is not an uncommon scenario where BIM methodology is delivered to a defined point but no further. Where traditional, manual construction methods are ultimately to be used, the advantages gained from the BIM, versus the cost of creating the model do tail off as we approach higher levels of detail.
The counter argument is that this does lead us towards a process which is open to human error.
Implications of adopting BIM
The buildingSMART MacLeamy Curve (pictured page 22) promotes a workflow whereby the decision making process is moved further forward and hence lowers the cost of refining design.
BIM methodology can assist in this effort by improving collaborative communication and by drawing closer parallels between the virtual concept and the built reality, thereby highlighting clashes and construction issues.
This desire to improve can also lead into one of the most common BIM adoption pitfalls, potentially causing undue financial expense and leading to BIM software and protocols becoming unpopular among staff.
It is an incorrect assumption that in developing a design using BIM methods, all design decisions have to be made at a far earlier stage of the job than is preferable or would previously have occurred.
|AEC(UK)BIM Protocols||AIA BIM Standard (US)||Description|
|LOD 0||LOD 100||A conceptual massing study where shapes and forms are explored against the client brief and design intent. At this stage, floor areas and volumes can be extracted from the 3D model and departmental flow can be rationalised|
|LOD 1||LOD 200||The basic form is developed using categorised components such as walls, floors, columns and equipment. These elements are generic place-holders in terms of their associated meta-data but also appearance, often with all objects made from one common material, hence the application of the term ‘White Model’|
|LOD 2||LOD 300||As design decisions are made, the generic place-holders are replaced with precise, manufacturer-specific objects, rich in associated information but still simple in their 3D geometry|
|AEC(UK)BIM Protocols||AIA BIM Standard (US)||Description|
|LOD 3||N/A||Simplified geometric form is adequate for most BIM tasks but when aesthetic images and rendered scenes are required, it is necessary to replace elements with more accurate objects|
|LOD 4||LOD 400||Objects are either swapped or additional information is appended to include fabrication and assembly information. This does not always mean that the objects get more geometrically accurate, but that information is added which is relevant to the construction process|
|LOD 5||LOD 500||The model is updated to reflect the As-Built nature of the finished building|
While the buildingSMART MacLeamy Curve diagram shows us that this can be beneficial to the overall project, it is inappropriate during the tender stage for instance, when work is carried out speculatively and with minimal effort.
It is often a symptom of the self-taught user that undue consideration of the components is applied prematurely whereas BIM software is just as capable of being vague and conceptual as CAD or the pencil are.
Very closely linked to this topic is the problem of over-modelling, which is not uniquely a BIM problem but is just as prevalent among CAD users. Just because software allows us to draw or model a component with accurate anatomical geometry, does not mean that it is the right thing to do.
The worst protagonists of this have and remain to be product manufacturers who provide their electronic libraries, complete with seals, washers, grommets, bolt-threads and fan-blades.
The user often does not have the time to clean and rationalise these elements and the result is too much graphical information going into a drawing or model.
BIM should be the technology that removes this problem but it is also the technology that accentuates it. It has the potential to eliminate it because associated metadata can provide specifics on a chosen element without the need for graphical recognition — rather than model the hinges of a door, the properties of a simple generic component can advise that Furniture set A is applied as per specification, for example.
Unfortunately, bad practice and over-enthusiastic users tend to get carried away, enjoying the ability to recreate a component as a virtual work-of-art. This is repeatedly evident by reviewing the copious online repositories for BIM content where proud modellers are willing to share their creations in return for plaudits and followers.
The problem is that such extremes are not scalable, nor do they necessarily add to the delivery or the value of the finished product.
Standards and protocols
Various international standards will be bandied around and may be referred to on different projects. A brief explanation is provided on the most relevant of those (box out, left).
All of the standards mentioned, left, are industry-wide protocols with many more coming up for consideration in each of the different disciplines, such as transfer protocols specific to environmental assessment of buildings and structural analysis of structures.
There are too many to list in this exploratory article but further information is available in this series of training modules.
Team and workflow changes
There are many areas of working practice that are touched by the BIM ethos if properly embraced.
That is not to say that complete turmoil will ensue on the first day of use, and BIM methodology can be eased into a practice and allowed to prove its merits before spreading its wings, but in order to take full advantage, old processes and workflows may need to be re-assessed.
A few such examples are highlighted here.
In the traditional drawing office, a pyramidal structure would see a lead designer at the pinnacle and a tier of tracers at the base with various grades in between. Often the lead designers would have a hands-off approach to drawing production work.
BIM encourages, and in many cases insists that operators understand what is being modelled because the elements are not arbitrary lines to which meaning is assigned by a skilled overseer; they are intelligent objects with properties and inherent characteristics specific to the category of component.
As such the more building-savvy the user — the more efficient they are at modelling and manipulating information in a BIM environment.
Particular skills will naturally emerge and talents for specific tasks will surface among the users. Some will take to content creation while others will gravitate towards schedules, detailing or model management.
Over time the team will settle into a new, more horizontal structure as these skills develop.
Another area that can lead to frustration in the office is the timeline for producing deliverables. Again looking at a traditional environment, a twelve week programme with a requirement for 200 drawings should see somewhere in the region of 150 drawings at or near completion by the nine week stage. Management and the client can see the progress and gauge whether deadlines will be met.
In a BIM scenario however an inexperienced team may not have a single drawing prepared by the same milestone, but they have a fantastic model filled with metadata and resplendent with fabulous views which are compiled at the eleventh hour to deliver the job. This can only lead to stress that can easily be avoided.
Most BIM tools allow the drawing sheets to be created, named and views allocated, even if those views are largely empty or under development.
As the model progresses, so do the drawing sheets, so the boss can see what is going on.
AEC(UK) BIM standard
A working set of protocols and best practice for SMEs. Free of charge and targeted at users of specific software applications in order to use recognised terminology rather than generic vocabulary. A Revit version and Bentley version are available, with other versions in production alongside generic documents such as BIM Execution Plan Pro Forma.
A UK standard that establishes the methodology for managing production, distribution and quality of construction information, including CAD data, using a disciplined process for collaboration and a specified naming policy. Some of the techniques and protocols are dated and a review is underway.
Construction Operations Building Information Exchange is a subset of IFC (see below), designed as an exchange format for the handover of a construction project upon completion and is a large spreadsheet. It does not need a 3D model to create it but tools can automatically transfer BIM data into the COBie format.
The favoured system for many architects, this element classification schema is no longer maintained and is superseded by Uniclass.
Developed by the Construction Industry Project Information Committee (CPIC) representing RIBA, RICS, CIBSE and others, this system replaces the CI/SfB classification and is due for a new release.
Industry Foundation Class (IFC)
A means of passing information from one BIM software platform to another. The difficulty is in the way that compliance is applied: imagine a list of one hundred bullet points and in order to comply, you must hit forty of those points. It is possible for two applications to be IFC compliant and yet completely miss each other. Future releases should tighten up the gaps.
A classification system for the US construction industry with a growing number of global users. The tables are made up of various other naming and numbering systems and the table for designed elements comes from UniFormat.
The dominant system in North America and those parts of the world where the US has influence, such as the Middle East.
AIA BIM Protocols E202
Focuses on the processes surrounding BIM use and collaboration between the various stakeholders rather than the internal standardisation of BIM software use. It is very similar to the BIM Execution Plan mentioned in the AEC (UK) documentation set and the Penn State version as well.
Fees and deliverables
It is imperative that the implications of BIM are considered when preparing fee proposals and agreeing terms with clients and contractors. By this we do not imply that it is more expensive to deliver a project when BIM methodology is utilised, nor is it as simple as saying that the reverse is true.
Often the increase in efficiency and hence the reduction in time and costs of preparing deliverables is offset by the increase in expectation and potential additional services, which may be naively promised for no additional fee. Those seeking work and agreeing terms at the top of a company need a good understanding of the various costs and efforts involved in preparing a particular set of data by those at the coal-face.
This is nothing new, but the upheaval of new technology and the clamour for available work has seen a few companies over-promise and strip out all profits from a job.
There are new roles emerging within the industry that will need to be filled, and hence opportunities to offer new services and grow additional revenue streams. Someone within a project team will need to take on BIM leadership and co-ordination. Do you want that role and the associated fee and responsibility?
Who owns the model? This is always an interesting question because unless it is stated in the contract documentation, the BIM data is simply a means to an end in preparing the drawings that you are obliged to deliver. If the client or contractor then asks the architect for a copy of the model for clash detection, review or even FM, should he expect to get it for free?
Many would argue that if I paid for your time in preparing the information, then I can expect to have it in the original format that it was prepared in. Whichever side of the fence you sit on, it is much better all round if this is clarified at a contractual level and not fought over at the back end.
Protecting embedded intellectual property is a topic that logically leads on from the model ownership.
If a lot of time is spent developing a data-rich and efficient library of components, and a model containing such elements can easily be mined for elements, this will inevitably lead to these elements falling into the hands of competitors and there is very little you can do about that. This should not be used as a reason not to build libraries but should be considered when defining the specification of such efforts.
Data format is also an aspect of the market which will come under intense scrutiny in the future.
BIM is not about a single piece of software, nor even a specific type of software, but a means of interacting with data from many perspectives and objectives, and hence the exchange formats are ultimately more important than the software used in any one part of the building life-cycle.
Formats such as IFC are hopefully going to step in and fill the gaps that currently exist and allow stakeholders to pass information freely around the design, construction and maintenance teams without large amounts being lost along the way.
Contract and insurance
Much has to change in order to allow BIM methodology to reach full potential and for the entire industry to properly embrace the new way of working and collaborating.
Various initiatives aimed at proving the effectiveness of IPD contracts (Integrated Project Delivery) or similar are both available and underway and these new contract documents should ease the adoption of BIM by eliminating some of the risks surrounding litigation, but this mitigation of risk is not the only contract-related change that we will probably see in the near future.
One example of an area that will have to change radically if we are ever to realise the collaborative advantages of working in a fully co-ordinated 3D model is the terms of contract for building services consultants and designers.
Recent years have seen a steady decline in their involvement, often to nothing more than schematic design and plant-room layout.
Even this small amount has been done at a relatively advanced stage of the design process, leaving little room for influencing proposals without significant cost implications.
As far as the insurance industry is concerned, BIM adoption has made them nervous to say the least. The current consensus seems to be that BIM is a free-for-all and that the only way to protect themselves is to ring-fence BIM activity and effectively treat it as a means to an end in the production of drawings, with the sharing of models prohibited.
This is due in no small part to the lack of common standards and mandated protocols by which they can gauge the capability of a company or the requirements of a project, and hence assess the inherent risks. It is something that the whole industry has to work to overcome and as standards are defined and gain acceptance in the future, we will see the emergence of professional accreditation and qualifications which can then be mandated by underwriters and sought as a mark of quality.
The final word
BIM is a mind-set, not a software application, and adopting BIM methods can require an overhaul of the design process, team structure and even business practices in order to achieve the full potential of the technology.
This is not going to happen overnight, as much because the industry will need to adapt as it is because of the internal upheaval and cost, but the potentials are an exciting area of development with new revenue streams, additional services, increased efficiency and a wider involvement in the whole building lifecycle.
It is not so new as to be an untested technology, but it is new enough not to be able to see the ultimate potential yet.