By Giovanni Marcelli
Even though the construction industry is still defining Building Information Modelling (BIM)—its scope and its processes—this new approach in design is a harbinger of good news and a catalyst of positive change for the industry.
A good definition of BIM is: “the
virtual representation of the physical and functional characteristics of
a facility which is a shared information repository for collaboration
throughout its lifecycle”. On a per-project basis, specifications are
also emerging that address and enforce the role of BIM participants, as
well as the timing of BIM tasks.
In the
foreseeable future, more projects will be modelled before any
construction site work begins and, consequently, contractors will gain
the great benefit of knowing more precisely what they need to build and
how. Though it requires a much larger investment in design upfront and a
lot more collaboration between owners, architects, engineers and
contractors, it is the significant saving in time, effort and money at
the construction phase that make it a compellingly sound investment.
Discussions
on BIM are not always simple; the impacts of BIM may even have the
potential to alter the roles of engineer and contractor. BIM has already
begun to change the construction process. The question is: How will
construction take place by the time we’re fully building in a BIM world?
Early indications show that, for the right projects, BIM has become a
very compelling proposition—even at this early stage when most people
are still learning and refining their BIM skills.
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Today,
full 3-D models are built in CAD as well as in BIM; adding to this
confusion is the fact that many BIM functions are actually achieved in
CAD. This is because certain BIM functions are still more feasible in
software like Autodesk’s AutoCAD than in BIM software like Revit, also
by Autodesk. For example, there are many more tools available for
driving sheet-metal fabrication from AutoCAD MEP than from Revit MEP.
However, there are ways in which BIM exceeds CAD.
The benefits of BIM
A BIM
model is more parametric; that is, changing a parameter of a BIM object
(like a piece of equipment or a run of pipe) will affect any view of
that object throughout the model. In CAD, multiple views of the same
components might require manual updating (for example, elevation versus
cross-section views) and, therefore, are prone to discrepancies caused
by human error.
More so
than CAD, BIM is designed for other parameters that stakeholders may
wish to add to the model objects, such as physical, price, procurement,
performance or even maintenance data.
Beyond
CAD, BIM refers to processes as well as tools that support an evolution
of the building industry toward Virtual Design and Construction (VDC). A
premise of VDC is to “build it twice”—that is, to virtually complete a
model (to the required specs) onscreen first before beginning to build
it physically onsite. On certain projects, the savings in physical
construction outweighs the cost of virtual construction, and these
savings increase with the complexity of the project.
BIM benefits for prefabrication
Given
the ever shortening construction cycles and the accuracy of BIM
technologies, the potential for prefabrication is becoming increasingly
appealing. Prefab has generated good returns for those contractors who
have adopted it in the past; it provides greater returns in the future
and may preclude some contractors from projects if they cannot leverage
prefabrication. It will no longer be optional if we are to avoid severe
stacking of trades. The building model helps considerably in the prefab
process because the contractor has complete knowledge of what is needed,
and there are fewer chances of conflicts and interference among systems
and trades.
Not all
jobs can be prefabricated to a large extent; however, any job can
benefit from some form of prefab. I expect manufacturers will start
selling more preassembled products for the electrical trade. In fact, I
am surprised that it has taken this long. Buying all the individual
components as we are currently doing and assembling them at the
jobsite—when the building is ready—is both costly and risky.
The
most significant benefits derived from prefabrication are:
•
Substantial labour savings
•
Reduced field crews
•
Reduced project duration
•
Improved safety
• Less
field labour and less risk
• Fewer
large tools
• Fewer
lost or wasted materials
With
BIM becoming a reality for more projects as we go on, I see
prefabrication becoming more common and easier because projects will be
better designed. Imagine doing the actual site installation in a
fraction of the conventional time, or having much smaller crews on the
jobsite, fewer people from other trades, fewer deliveries, fewer
backorders, and much less garbage disposal and job cleanup. Imagine
being better able to assess project completion while greatly mitigating
risk.
The reality of BIM
The BIM
concept is sound, efficient and productive. The creation of a virtual
model before the real building goes into production presents many
advantages. Problems that would normally surface during the construction
stage and cause costly changes and delays will be uncovered and
resolved while building the model. A virtual model can be built for a
modest amount of money and can be easily modified.
Despite
of its benefits, the more substantial upfront investment and diverse
skills/knowledge required to build the virtual model can hamper the
proliferation of BIM. Add to this the fact that owners are used to
paying smaller fees for drawings and specs, and some like to
conveniently leave the drawings partly unfinished so they can make
changes as late in the process as possible and better accommodate the
needs of their tenants.
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We can
also appreciate that engineers like the current process better, and some
may hesitate to participate in BIM because they know that limiting the
detail of their work will keep them less liable. As for skills and
knowledge, the BIM process truly pushes the equation to the next level;
we are now dealing with modelling and no longer just detailing. The
detailing process, for valid reasons, is somewhat incomplete at present,
since engineers are not given time, information or enough money to
produce a fully detailed set of drawings. Detailing is simpler than
modelling in that the symbols on the drawings are just symbols whereas,
in the model, we have objects that may contain real-world data.
When it
comes to estimating, it may be some time before the virtual model
includes enough building objects for estimators to complete their
takeoffs without the need for additional 2-D or CAD drawings. And unless
the designer works for the contractor, designers generally do not want
liability for the accuracy of the quantities, leaving such details to
the estimators.
It is
too early to speculate whether BIM will move beyond supplementing CAD to
someday replacing it. Many continue to find it more cost effective to
build the model (or parts of it) in AutoCAD then import those parts into
Revit as needed. It is unlikely that BIM will ever literally make 2-D
drawings obsolete, or fully replace CAD for use on simpler projects.
While
electrical and mechanical contractors continue getting more adept at
modelling geometrically in CAD, the concept of virtual modelling is
relatively new and, today, there are more BIM mechanical software tools
available than electrical. However, given the vast market potential, it
is reasonable to expect substantial progress in the development of more
powerful tools in the foreseeable future.
As the
landscape of the construction industry evolves, technologies and
processes such as BIM and prefabrication will continue to become
standardized with goals of improving workflow and minimizing costs. It
stands to reason that, as we get better at it, greater benefits from BIM
will be attained, and it will become the industry-standard building
process for medium- to large-scale projects.
Giovanni Marcelli is the founder and CEO of Accubid
Systems, which started back in 1985 when Marcelli (an electrical
contractor at the time) became disappointed with the software available
to contractors. Today, Accubid is a leading provider of estimating,
billing and project management software for electrical and mechanical
contractors. In 2005, Marcelli was honoured with the Independent
Electrical Contractors Association’s (IEC) National Industry Achievement
Award for outstanding contributions to the electrical industry. CLICK HERE
for Accubid.
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