제목 | Perspectives on Historic BIM Developments in ItalyAECbytes | ||
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작성자 | BIMer | 작성일시 | 2016-12-16 11:15:40 |
내용 | Perspectives on Historic BIM Developments in ItalyAECbytes Viewpoint #82 (December 15, 2016) Stefano Della Torre
The BHIMM Project When in 2011 we launched the BHIMM
(Built Heritage Information Modeling Management) project, which involved six
Research Units and had been awarded to the Politecnico di Milano by the Italian
Ministry of University and Research, available literature concerning the
implementation of digital informative modeling on historic buildings was
definitely poor. The developments in the field that we
can see and glean from the literature now, only five years later, are simply
amazing. The technological transfer of BIM from the construction field to the
world of cultural heritage seems to be a more and more appealing subject for
academic researchers, but many doubts and problems arose looking for the most
effective road to a real implementation on this very peculiar market.
Several important Italian monuments have
been used to test BIM techniques as implemented in the heritage domain: for
instance, Milan Cathedral, the huge complex of Albergo dei Poveri in Genua
(Figure 1); the church of S. Maria di Collemaggio in L’Aquila that was damaged by the 2009
earthquake (Figure 2); and Masegra Castle in Sondrio in the Alpine region
(Figure 3), to name just a few. In the course of these implementations,
different solutions were explored, and almost all the activities that follow
each other along the cyclic management process of an historic building,
acknowledged and as such protected, have been explored with the perspective of
making them digital and interoperable as much as possible.
Built Cultural
Heritage Process The specific nature of the conservation
process of built cultural heritage is radically different from the construction
process, and therefore poses substantial challenges in implementing BIM on
these projects. The many pilot research BIM
implementations that were carried out under the aegis of the BHIMM project on
several Italian historic buildings demonstrated that the transition from the
traditional representation by 2D views associated with a restoration project to
a 3D parametric model cannot be just a matter of tools and procedures to be
customized: instead, it is necessary to understand the use of parametric tools
to renovate the whole heritage conservation and valorization process. The transition from drawing to BIM is
parallel with the transition from restoration as an event to conservation as a
process (we used to speak of planned conservation). Therefore, it is a
transition from a scheme that used to see restoration as a constructive process
(on existing premises instead of on free land), to the vision of a long-term
process, in which many different activities (management, maintenance,
monitoring, conservation, heating, restoration, etc.) are carried out by
different actors, who need to exchange a lot of information overcoming
asymmetries and cognitive gaps.
It is prudent, therefore, to approach
the topic of Built Heritage Information Modeling, or Historic BIM, by an
analysis of the processes well before working on the question on the
development of the tools.
From 3D Survey to
Objects-Oriented Model
It is well known that the precondition
for the ability of 3D models to support the management of existing buildings
has been the evolution of acquisition tools in the Geomatics field (also known
as surveying engineering or geospatial science). Point-clouds became familiar
to architects and conservators, as the costs of automatic surveying became
competitive with the costs of direct measurements. Generally, three basic problems are
pointed out when dealing with the step from point-clouds to parametric models
suitable for architectural conservation, and these topics have been largely
dealt with in the framework of BHIMM as well. First, in order to be used operationally
for conservation , the data that is collected cannot be limited to the external
surfaces of the objects, which have to be investigated and in some way
represented by their thickness, layers and internal features. In a BIM
environment therefore, the problem arises of characterizing elements as
three-dimensional not only from the geometric point of view, but also for
materials and techniques. Third, BIM models, as provided by
parametric software available today, use typified components, downloaded from
libraries, which can be enriched and customized, but any historic building is
the outcome of construction processes, besides changes and layering in progress
of time, which produce the variety that is just the core of the recognition of
authenticity, and therefore of value. The question of harmonizing the
oneness character with the typology approach is surely not new, as this was one
of the most discussed topics for Conservation theory. The solution of
producing individual objects embedded in the model, rather than in the software
library, has been successfully explored, but it entails giving up a series of
possible automations.
On this point, it would be worthwhile to
point out that there are already several products available with ready-made
families of elements typical of historic architecture, classified by periods,
often coming from the plates of architectural treatises. You can find on the market
Renaissance BIM, Gothic BIM, Regency BIM, or any period BIM. Using these
products can certainly help to make 3D models more realistic and
better-looking, but these models should serve to enhance data sharing, not
simply build sceneries fit for videogames. The risk is to consolidate a rough
level of detail, more than good for some purposes, but not exhaustive for the
whole process.
Historic BIM LODs
The trend nowadays, also from the
industry side, is to bridge the gap between survey and parametric modeling,
empowering the most popular software tools. Nevertheless, the intent of this
step has to be clarified, by means of some reflections on operational needs, on
the required levels of description and information. Being definitely different from the
design of a new building, the work carried out on an existing building,
especially when it is dealt with as a heritage object to be conserved and not
just retrofitted, is not a simple progression: it’s a matter of reverse engineering or downloading from
data banks. If we are able to imagine the ideal process developed up to its
regime, we see that the need of information sharing does not point to the
unique perfect model, suitable for any function, used by all the actors, as the
best option to strive for. Such a high level of detail in models
for cultural heritage may not be needed in some technical domains. For example,
single domains such as structural analyses, energy simulations, behavioral
studies, cost computation, etc. could refer to simplified versions of the
detailed model. However, sometimes even single technical activities require an
advanced level of detail, as well as different definitions of the parametric
objects. For example, a structural or energy analysis may need to sometimes
take into account an entire element, such as a wall or a column, and sometimes
just its layers, parts, stones, etc. At other times, the entire level of detail
of the model would be required for other kinds of analyses.
Model versus
Platform Reasoning about the inversion of the
elaboration flow leads, therefore, to a point already underscored by BIM
research—the
conceptual distinction between the (unique) interoperable model and the
platform, which enables data exchange among several “domain
specific” BIMs. Domain specific models (i.e., BIM for
architectural design, structural analysis, energy analysis, construction and
site design, cost analysis, management, maintenance, etc.) will undoubtedly
perform better than the huge single model, which should be also the exchange
platform. For each model, an individual
recognition of BIM objects can be carried out; each specific model should
download from the general data base just the useful data, and upload its output
in order to make it available for other domains through the platform.
This vision of BIM has been argued, e.g.
by Arto Kiviniemi, as the way to ensure the highest interoperability. It is
also the way to carry out a very important change in the heritage field, as the
required anticipation of detailed investigation, as well as the availability of
tools enabling a continuous control, will enhance the quality of the whole
process.
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