BIM

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The digital construction revolution: BIM or Building Information Modeling

The construction industry is grappling with an epochal change, a digital revolution that is changing the traditional way of designing: BIM or Building Information Modeling.

After having dealt with the theme of BIM in public procurement, today we are entering the bowels of what is considered the most important revolution of recent times and which will soon become the universal standard of the construction industry: from 2025 in fact, it will be mandatory for all new works created.

In a few years, Building Information Modeling has revolutionized the architecture, engineering and construction (AEC) sector through the use of information technology, increasing the productivity, efficiency, quality and sustainability of buildings. BIM allows integrated design, involving the various professional figures (architects, engineers, builders) through the entire life cycle of an architectural work, in a circular economy perspective, "from cradle to cradle" (from cradle to cradle): design, construction, operation and disposal / reuse / recycling.

We recall that construction, in Europe, is responsible for 40% of energy consumption, 36% of greenhouse gas emissions and 33.5% of total waste generated by all economic activities (Eurostat 2016) - mainly due to activities of construction, use, renovation and demolition. The digitization of buildings, together with energy efficiency policies, green procurement and energy communities aim to accelerate the process of decarbonisation of the economy by 2050 (EU target).

What is BIM?

As defined by the NIBS (National Institute of Building Sciences), Building Information Modeling is "a digital representation of the physical and functional characteristics of a structure, a shared knowledge resource of information that forms a reliable basis for any decision along its cycle of life, from conception to demolition “.

BIM, therefore, is not a software or a 3D project, but rather a set of technologies, processes and methods that allow different stakeholders to collaboratively design, build and manage a work in a virtual environment.

BIM is the virtual representation of the building, an accurate digital reproduction of every single component, which allows control and analysis activities throughout the building process, allowing to extract the data and documents necessary during the design, execution and management phases.

The peculiarity of BIM is to have in a single 3D model, a vast amount of information and documents, which perfectly identify each element, linking it uniquely to its real counterpart.

So for a wall we can know the information about its physical characteristics (weight, mass, density), mechanical (compressive strength, traction, impact), energy (thermal dispersion, transmittance, vapor permeability) production (company, costs), divided by whole component (window, door…) or by material (brick, concrete, wood, insulation…) -.

This information can be exploited for a multitude of analyzes and checks on the virtual model: energy analyzes, sustainability and environmental impact or structural checks, metric calculations for cost estimation, work schedules, the construction and management phase of the work, without neglecting the forecasts of future maintenance and decommissioning interventions.

Before delving into the abyss of computer design, let's make a small historical digression to discover digital design, from its origins to today.

History and evolution of digital drawing: from CAD to BIM

Initially it was the CAD. Although the term Computer-Aided Design had already appeared in 1959, it was only in 1963 that it came to life, thanks to Ivan Sutherland who, on the occasion of his PhD thesis at MIT, developed the software Sketchpad, the first prototype of a graphic interface that gives start to the era of digital design.

A first definition, ancestor and precursor of Bim, was introduced in 1974, by what is considered the spiritual father: Chuck Eastman. He, highlighting the strong limitations of traditional computer design (cad), used until then to describe a building, introduces a new mode of graphic representation: the BDS or Building Description System.

"The BDS was initiated to demonstrate that a computerized description of a building could replicate or enhance all of the current strengths of drawings as a means of designing, constructing and operating buildings, as well as eliminate most of their current points. weak. Our premise was that a computer database could be developed that would allow the geometric, spatial and property description of a very large number of physical elements, arranged in space and "connected" as in a real building. An important feature of the BDS model is its ability to generate drawings. From this unique database, the designer can request any plan or section, perspective or exploded view and receive high quality construction detail documents, quickly and at low cost. All drawings produced from the same database would automatically be consistent ”.

Despite the tenuous formal dissonances, Eastman's description of BDS corresponds incredibly to today's BIM or Building Information Modeling, which arrived only 18 years later, in 1992 by Nederveen and Tolman ("Modeling Multiple Views in Buildings", 1992). The merit of Laiserin (who is often attributed the authorship of BIM) is that of having condensed the acronym in a definitive way.

In 1987 Graphisoft Archicad developed the concept of “virtual building”. In 1994, the IAI - International Alliance of Interoperability (USA) was founded, for an integrated development of applications, which created the first exchange standard, the IFC - Industry Foundation Classes. Two years later, in 2005, the IAI changes its name to BuildingSmart-.

Since 2007, the United States, pioneers of digital design, have required the use of BIM for all large projects that receive public funding. Europe only arrives in 2011, driven by the UK (following the example of Norway and Finland) which draws up the National Plan for the use of BIM in all public projects, with the aim of reaching level 2 in 2016 .

Evolution of the BIM regulatory framework

In Europe, the legislation incentivising the use of BIM in the construction sector occurs only in recent years. Excluding the Scandinavian countries, pioneers together with the United States of the digital construction revolution, the rest of European countries rely on the spirit of initiative of national policies.

The UK has already released a plan since 2011 to impose the use of BIM and collaborative procurement methods on all publicly funded projects. The target? Reduce waste and costs.

Europe closely follows the visionary policy of the UK. 2014 is the year of the turning point: a radical reform process of Public Procurement begins, shared by the whole European Union. In fact, the Procurement Directive (D 2014/24 / EU) which, in paragraph 4 of article 22, introduces the use of BIM in member states: "For public works contracts and design competitions, member states may require the use of specific electronic tools, such as electronic simulation tools for building information or similar tools. "

In Italy, BIM was introduced in 2016 by the New Procurement Code (Legislative Decree 50/2016) which, in Article 23, governs the introduction of electronic methods and tools in the design of public works: "Planning in the field of public works is divided, according to three levels of subsequent technical investigations, into technical and economic feasibility project, final project and executive project and is intended to ensure: the rationalization of design activities and related checks through the progressive use of specific electronic methods and tools such as modeling for building and infrastructure (BIM) "-.

Nevertheless, it is only since 2019 that use has become mandatory and progressive in terms of the complexity of the works, thanks to the Baratono Decree (DM 560/2017), also called the BIM Decree. The national technical standard UNI 11337 completes the legislative framework, specifically defining many aspects related to the use of Building Information Modeling. A standard, attached to ISO 19650-1-2: 2019 which, for the value of the contents, is among the most influential in Europe.

The advantages of integrated design

The BIM methodology provides an open and collaborative, integrated form of design, "through collaboration throughout the life cycle of an asset supported by the creation, collection and exchange of 3D models and shared, intelligent, structured and connected data" ( UK BIM TASK GROUP, 2014).

The benefits of integrated design are, among others:

reduction of errors

higher productivity

lower costs and times

These advantages are evident in the well-known graphical representation developed by Patrick MacLeamy, shown below:

The curve graphically compares the traditional process (CAD) with BIM: in the face of a greater initial commitment (of costs, times and means), the BIM method allows a large subsequent saving. The costs of a project, in fact, increase in proportion to the degree of definition reached: a modification in the course of execution of the works will therefore be much more onerous than in the design phase of the work.

This entails considerable advantages related to the reduction of costs and times that the process would undergo as a result of changes in the course of work.

Having a virtual model of the building that contains all the information of the real building, allows control and analysis activities throughout the entire life cycle. This is a great advantage that allows an efficient design, reduces errors (and therefore costs) and optimizes time-.

The adoption of BIM also allows real-time monitoring of the state of the structure. This allows problems to be quickly identified and a solution to be found promptly.

The levels of maturity of BIM

The concept of BIM as a digital drawing has evolved over time, passing from the two-dimensional CAD format to a three-dimensional model, up to the building information model or Building Information Modeling.

Bew-Richards' 2008 BIM maturity model defined four levels of BIM (0 to 3), from the paper-based silo approach to the collaborative, fully integrated and interoperable model-based approach.

Level 0: the information on the project is mainly on paper.

Level 1: a mixture of paper (2D) and / or 3D environment.

Level 2: Discipline-focused proprietary BIM or “pBIM”. Each discipline produces its own project information within a 3D environment. The intelligence is then added to the models by attaching data / information; for example, specifications or dimensions for each object / component. Standards are established for the production, exchange and storage of information in a CDE. Each model interfaces with each other via middleware software, thus allowing integration to help coordination.

Level 3: fully integrated “iBIM”. A single collaborative model is accessible to all team members, allowing multiple users to work on the model simultaneously.

Any changes to the information of a particular discipline update those of another in real time.

BIM design development technology is currently stuck at level 2.

The dimensions of BIM

The use of intelligent models has extended the scope of BIM far beyond the three dimensions. Now the digital model affects the entire construction process (planning, design, construction, management) and the entire life cycle (LCA) of the work, from conception to decommissioning. We therefore have the 4D dimension (times, time schedule), 5d (costs, quantity) and so on.

With reference to the recent Italian regulation UNI 11337 part 6, the seven dimensions correspond to:

1D: Concept design

2D: Production of 2D drawings (plans, elevations and sections);

3D: Three-dimensional rendering of the artefact;

4D: Analysis of duration or times (programming);

5D: Cost analysis (calculations, estimates and economic evaluations);

6D: Work management phase 8 - use, maintenance and disposal -

7D: Assessment of sustainability

The Italian standard exchanges the 6D and 7D dimensions, previously attributed respectively to sustainability and use / management / maintenance. These seven dimensions are final but work in progress: other additional ones are being studied.

Levels of development (LOD) of BIM models

The quantity and quality of the information content of the objects that make up the digital BIM models are defined as LODs or levels of development. Each element of the model must be a verified representation in terms of size, shape, position, quantity and orientation of the actual installation and placement in the project.

The level of detail of an object must be considered as the set of all information of a geometric and non-geometric type (normative, economic, etc.) that can be represented in graphic form (2D and 3D) and in alphanumeric form in order to give rise to a more correct evaluation of information contents such as time (4D), costs (5D), sustainability (6D) and management (7D).

The reference scale of the levels of development of the elements, as an output of the BIM model, is that developed by the American Institute of Architects referred to in the BIM Forum LOD Specification 2020.

It identifies 5 degrees of complexity of the model, with progressive levels of depth, gradually more accurate and detailed:

LOD 100: concept. Elements do not represent geometry, but symbols or other generic representations of information.

LOD 200: approximate geometry. The elements are represented graphically but in a generic way, such as volume, quantity, position or orientation.

LOD 300: precise geometry. Elements are graphically represented as specific systems, objects or assemblies from which quantity, shape, size, position and orientation can be directly measured.

LOD 350: suitable for implementation. The elements have improved with the addition of information regarding interfaces with other building systems. For example, a LOD 350 masonry wall element would include jamb conditions, connecting beams, grouted cells, dowel locations, and joints - information that allows the model user to coordinate the wall element with others. systems in the facility.

LOD 400: "as built". The elements are modeled with sufficient detail and accuracy for the fabrication of the represented component.

This scale should be considered as a reference and nothing prevents you from proposing additional and specific information contents. By way of example, the development levels for the various phases of the design can be indicated: definitive (at least LOD 300) and executive (at least LOD 350).

Italian LODs (UNI 11337: 2017)

In translating the American classification of LODs, Italy has tried to adapt them to its own needs. The UNI 11337 standard, in analogy with the US and British reference legislation, defines the Development Levels of digital objects as "evaluation of both the development levels of graphic and non-graphic attributes".

The first novelty that immediately catches the eye is that now the Levels of Development are not indicated with numbers (as is the case in the US or UK), but with letters (from A to G):

LOD A: symbolic object. Symbolic representation in 2D (or 3D if necessary). It does not express geometry constraints. The qualitative and quantitative characteristics are purely indicative.

LOD B: generic object. Generic geometric representation or ingo mbro geometry. Qualitative and quantitative characteristics are approximate.

LOD C: defined object. Geometric representation defined. The qualitative and quantitative characteristics are defined in a generic way. They are applicable to all similar entities.

LOD D: detailed object. Detailed geometric representation. The qualitative and quantitative characteristics are specific to a plurality of similar products. Useful information for assembly and maintenance is included.

LOD E: specific object. Specific geometric representation. Qualitative and quantitative characteristics are specific to a single system. There is information related to manufacturing, assembly and installation (as well as what is useful for maintenance).

LOD F: object executed (as built). Specific geometric representation of what has been done (verified on site). The qualitative and quantitative characteristics are those specific to the product installed. There is information relating to manufacturing, assembly and installation (as well as what is useful for maintenance) valid for the entire life cycle of the work.

LOD G: object updated. Specific historicized representation of the specific object (verified on site). The qualitative and quantitative characteristics are those specific to the product installed and updated with respect to a previous state of affairs. There is information relating to management, maintenance and / or repair / replacement valid for the entire life cycle of the work. The level of degradation of the object is also recorded.

Another important innovation introduced by the Italian regulation UNI 11337: 2017 is the concept of BIM applied to conservation / maintenance and restoration (very widespread activities in our country): the LODs F and G are born, which go alongside the 5 levels of definition. already contemplated by European and international legislation.

The LOD F expresses the as-built detected with all the characteristics present in the real world (it is essentially the result of what is defined at the level of LOD E). In the information section, particular importance is given to any forms of deterioration present, in the presence of any test certificates as well as the time schedule of the planned interventions (maintenance plan).

The LOD G expresses the updated version of the virtual element and keeps track of the history of the interventions performed on the artifact: maintenance / replacement date, the "Maintainer" and the type of intervention carried out.

The LOD of the objects must be adapted to the Objectives and uses of the model (architectural, structural, plant engineering), in order to allow the extraction of the drawings, the quantities for the evaluation of the metric calculation or the data necessary for the maintenance of the systems built. .

The legislation is rapidly evolving. In fact, the new ISO 19650-1: 2018 has been active since December 2018, which has partially revolutionized the concept: the LODs are replaced by LOINs (Level of Information Need), divided in turn according to the type of information (geometric and non-geometric requirements). geometries) in LOI (information level) and LOG (geometry level) -. Each client can define the information and graphic level to be requested through the Information Specifications.

The professional figures of BIM

The UNI 11337 part 7 standard provides application indications on the methods of evaluation and certification of the professional figures that revolve around BIM, namely:

CDE Manager: manager of the data sharing environment

BIM Manager: manager of digitized processes

BIM Coordinator: coordinator of information flows

BIM Specialist: advanced operator of information management and modeling

The organizational structure is strongly hierarchical. Within the digital work environment where data is shared between all the actors participating in the building process, managed by the CDE Manager, the BIM Manager is responsible for organizing the various specializations: architectural, structural, plant design. For each of them, the competent BIM coordinator will coordinate the various BIM Specialist figures (architecture, structures, systems, infrastructures) who are responsible for the actual creation of the information model.

The UNI 11337-7 standard also defines the knowledge, skills and competence requirements of the professionals involved in the management and information modeling. To be admitted to the certification exam, candidates must meet the following minimum requirements (see table):

Only for the BIM Specialist, the specific experience can be replaced by a relevant Master of at least 200 hours of training and at least 3 months of internship in companies, supported by a declaration from the company itself confirming the indicated period and describing the role and the activity carried out by the candidate.

The generic work experience (6 months) can also be understood as an internship or internship activity.

For the assessment and certification of Building Information Modeling (BIM) professionals, UNI / PdR 78: 2020 was born "Requirements for the assessment of compliance with UNI 11337-7: 2018 '' Construction and civil engineering works - Digital management of processes construction information - Part 7: Requirements of knowledge, skills and competence of the professional figures involved in information management and modeling ". Result of the working synergy between UNI (Italian Standardization Body) and Accredia (Italian Accreditation Body), it was published on 2 March 2020-.

UNI / PdR 78: 2020 is a technical document that supports the national standard. The reference practice was developed to provide information of an applicative nature in relation to the methods of assessing and certifying people, in compliance with the UNI 11337 part 7 standard, which defines the knowledge, skills and competence requirements of the professionals involved in the management and in information modeling.

Data sharing environment: ACDat or CDE

All the professional figures belonging to the BIM design team operate within a virtual work environment, a digital platform where all the information of the work is shared, updated, verified and validated: the Data Sharing Environment (ACDat) or Common Data Environment (CDE).

ISO 19650-1 defines CDE as: “agreed source of information for a given project or resource, for the collection, management and dissemination of each information container through a managed process”. The UNI 11337 standard identifies it as: "environment for organized collection and sharing of data relating to models and digital documents, referring to a single work or to a single complex of works".

The Data Sharing Environment or Common Data Environment is, ultimately, an IT infrastructure for the collection and management of organized data, including its own procedure for use, where only accredited subjects can share the information produced according to pre-established rules.

The four phases of the elaboration work, through the ACDat, are:

1) Work in progress: CDE area where the team carries out its work using the software systems of its organization. Unverified design data used only by the internal design team.

2) Shared: area of ​​the CDE where the team shares verified design data with other members of the project team.

3) Published: CDE area for coordination and design output validated for use by the total project team.

4) Archive: Area of ​​the CDE for the history of the project maintained for knowledge and regulatory and legal requirements.

The professional figure in charge of managing and organizing the data sharing environment is the CDE manager.

The digital environment is based on an IT infrastructure governed by specific systems:

security for access;

traceability and historical succession of the changes made to the information content;

conservation over time and relative accessibility of the information assets contained;

definition of responsibilities in the development of information content -;

for the protection of intellectual property

We remind you that UNI-EN-ISO 19650 is applied in Italy together with the UNI 11337 series, which is a complementary national standard.

Interoperability: Open BIM (IFC) and softwares

BIM is not a software, but a working methodology based on interoperability, collaboration, coordination and communication between the different actors (engineers, architects, builders) in the phases of the construction life cycle (design, construction, management and maintenance, decommissioning, etc.).

To better understand this concept, it is useful to know what is meant by “interoperability”: “The ability of two or more systems or components to exchange information and use the information exchanged” (IEEE, 1990).

To ensure efficient information exchanges, it is good practice to adopt open data formats (Open BIM), which guarantee the electronic exchange of information between the various software available on the market. There are in fact a plurality of computer programs that allow you to design in BIM language.

The electronic data formats, on the basis of which it is possible to set up an effective exchange between software platforms, are essentially of two types:

Proprietary formats (native formats);

Open standard (open formats).

The proprietary formats originate from a specific software (AllPlan, ArchiCAD, Autodesk Revit, Bentley Building, Tekla, Acca Edificius, VectorWorks) and allow the exchange of data between software belonging to the same manufacturer. The use of this technology can hinder the flow of information between different players in the building process and users of different software, reducing their interoperability.

When the data is not connected to any specific software application and that is not bound to it, we speak of "open BIM", an open standard format, which allows it to be shared, modified and used even between different software, in a manner capillary.

BuildingSMART International promotes the standardization of processes by implementing the Industry Foundation Class (IFC) as a neutral data model. IFC is considered to be the universal open standard for exchanging BIM information. It allows the exchange of data, both between different software platforms and between platforms belonging to the same suite, allowing to standardize workflows with the aim of achieving sharing and consistency.

And in Italy? Italian legislation encourages the use of openBIM open standard formats, such as IFC. Article 23 of the New Procurement Code, in paragraph 13, provides for the use of electronic tools that "use interoperable platforms by means of non-proprietary open formats, as well as for recovery, redevelopment or variants not to limit competition between technology suppliers and the involvement of specific projects among designers ".

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