Developing 3D digital twins of historic buildings and implementing BIM technologies on conservation heritage projects using H-BIM methodologies and workflows
Data-driven Building Information Modelling (BIM) technology has brought new tools to efficiently deal with real and the virtual environments in the field of Architecture, Engineering, Construction, and Operation (AECO). For historic assets, BIM represents a great opportunity, enabling preventive maintenance and decision-making, heritage management and interpretation. The potential application of Historic-BIM is in creating a Digital Twin of the building asset.
In this article we’ll take a closer look at the concept of consolidation and dissemination of heritage information, showing the process involved in creating interactive virtual environments for restoration and preservation of existing buildings using H-BIM methodologies, from 3D modelling to decay and degradation analysis, down to defining interventions and the integration with structural and MEP technical systems modelling.
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What is H-BIM?
BIM (Building Information Modelling) addresses various processes in terms of:
These different phases are also mirrored through an information model that contains data relating to the building’s entire life cycle, from planning, through to construction, leading up to demolition and dismissal of the asset.
This approach also applies to historical buildings too therefore defining H-BIM (Heritage or Historic Building Information Modelling).
With the development of H-BIM, we can now create detailed models of historic buildings with intelligent objects, e.g. information relating to the building, its components and features, which can be updated, replaced and implemented over time. In addition to typical 3D modelling, H-BIM provides for a detailed and comprehensive analyses of the existing surveyed stage regarding materials, identification of deterioration patterns.
Having a digital model of historical heritage is a much cheaper tool to allow building investigations because, unlike other areas of study, there is no way to take buildings to laboratories or store them in museums or galleries like other historical artifacts.
It’s crucial to highlight that HBIM is a process applied to existing buildings, whether they are of monumental or historical-artistic importance or common dwellings from the last century. Therefore, the scope of BIM methodologies also includes the creation of 3D models using digital scanning technologies to survey the current state of historic buildings, such as photogrammetry and laser scanning, expediting the process of generating the digital model. Photogrammetry is a low-cost method and captures building textures and materials by creating a 3D model from photographs.
The potential of BIM for existing buildings
Until now, H-BIM hasn’t been widely used in the construction industry due to the lack of shared regulations and standardised workflows, and above all due to the difficulties involved in the modelling and information acquisition phases. In fact, modelling a historic building means taking into account elements that cannot be standardised or traced back to predefined deformations, irregularities, uncertainties regarding construction techniques or the presence of degradation phenomena, etc.
At present, many software packages are adapting to these requirements in order to manage the whole digitisation process of the existing building heritage with a more methodologic manner.
Edificius, for instance, has a new BIM modelling environment developed specifically for HBIM, with a rich library of typical historic building objects and specific object editors that adapt to particular modelling needs, such as:
Vault Editor– enables you to model different types of vaults using new specific objects (barrel, rampant barrel, half-barrel, pavilion, polygonal-based pavilion, ribbed, ribbed with polygonal-base, dome, lunettes, horizontal cut and vertical cut)
Rib– allows you to insert ribs at the vault intrados and extrados, either manually or automatically using the magic wand
Wooden floor deck– create and customise a wooden deck by setting thickness, cross-section, beams spacing and rotation
Degraded area– another specific editor for defining degraded surfaces to which a specific material can be applied
Damage area– an editor for identifying and highlighting damages on a specific building elements
Orthophoto– assign orthophotos to building elements and obtain a faithful representation of any surveyed stage completing it with material information.
This makes it easy to overcome modelling difficulties (even with large irregularities, complex decorations, out-of-date building systems) and to take full advantage of all the benefits of HBIM, which include:
- quick processing of the 3D model
- use of intelligent parametric objects
- document and data management
- greater control of the project and of investigation and analysis campaigns
- information and models sharing
- planning of maintenance work
- asset promotion
- creating databases that can be updated over time
- application of advanced technologies such as virtual or augmented reality.
How to develop a historic building BIM model: HBIM project workflows
Generating a 3D BIM model of a historic building allows you to have all the benefits of BIM on a restoration project.
Let’s see how to develop the 3D model and the restoration project of a historical building with the HBIM methodology.
In summary, the main steps to follow are:
- CDE (data sharing environment) structuring
- data collection, processing and historical background documentation
- management and sharing of the collected documentation on collaborative platforms
- photographic survey and perspective calibration
- (from simple measuring up with traditional tools, to the latest technologies based on laser scanners, total Station, etc.)
- material survey
- surveyed stage 3D digital twin modelling with BIM Authoring tools
- model sharing on collaborative platforms
- study of the surveyed stage functional layout
- degradation analysis directly in the HBIM environment
- material layer compositions and construction phase analysis in the HBIM environment
- cracks and kinematics studies
- planning of investigations and tests
- identification of project interventions
- integration with BIM software for structural and installation systems design
- 3D digital twin modelling
- project verification in real time rendering views or in virtual reality (iVR)
- automatic cost estimating from the 3D model
- production of project and working drawings.
To find out more on this topic, take a look at the case study shown below and produced with Edificius.
A practical case study with Edificius
The objective of this practical example is to digitise a residential building from the early 1900s.
The first step is to run a site survey and to acquire all relevant geometric data using a 3D laser scanner. The output is a point cloud cluster, containing geometrical information, together with their coordinates in a known reference system with a colour coded distribution as obtained from the photographic site survey during the scanning phase.
The survey data is then imported into Edificius where the BIM modelling and digital twin creation process is completed.
The modelling phase always starts off from setting up the building’s floor levels,
Levels (mezzanine, first floor, roof level, etc) and the useful
subLevels with their relating elevation values. The site’s Land elevation map and contour lines were seamlessly imported directly from Google Maps, together with satellite imagery, using the Edificius for Google Maps integration.
The building modelling was facilitated by the Edificius H-BIM environment parametric objects, which allows the reproduction of the characteristic elements of historical architecture (vaults, wooden floor decks, ribs, etc.).
External walls, windows, staircase and all other façade details were then modelled (moldings, capitals, pilasters, etc.).
With the 3D modelling process completed, other useful information for project development can be shared using the collaborative usBIM.platform. This enables the entire team to have a centralized project data storage system to communicate, store and process allowing awareness of physical space performance and simulate the H-BIM assets in virtual space for decision making scenarios.
The potential application of the Digital Twin for Heritage purposes is its realistic representation in the form of an intelligent and semantically enriched 3D model (H-BIM), becoming a tool capable of managing information collected and modelled while improving its availability and accessibility among stakeholders (owners, facility management operators, tourists, etc.)
At this stage, an IFC model of the H-BIM DT model is exported leading to the integration process with the EdiLus software for structural modelling and analysis. The structural check workflow included:
- automatic architectural objects recognition in EdiLus
- structural modelling
- FEM model simulation
- identification of constraints
- loads analysis
- structural analysis.
The material characterisation and state of conservation assessment of decorative details across the facade were carried out together with the structural analysis. All this was facilitated by importing the textured mesh obtained from the laser scanner data. The orthophoto command allows you to overlay photos enriching the overall quality of the digital twin representation. The areas affected by degradation phenomena were then easily identified on the orthophotos. Edificius also automatically generates H-BIM legends for improved interpretation of degradation, decay and cracking patterns.
Unlike traditional processes, the H-BIM methodology offers the great advantage of creating and updating an extensive data-driven database of information regarding the state of conservation of an H-BIM asset. In addition, project Management with usBIM can lead to many other advantages too, such as:
- easy consultation, transmission and management of the state of conservation over time
- preparation of degradation sheets useful for identifying decays and diagnostic analyses
- definition of a protocol to be respected for each restoration operation to be carried out and integrated using usBIM.platform.