Spectacular BIM – Modelling historic structures with a BIM approach

Supporting surveys and diagnostic studies with a BIM approach at Hőgyes-Schöpf-Merei Pharmaceutical Research Centre of Semmelweis University

Modelling based on point clouds by establishing the LOA (Level of Accuracy) levels before modelling was very important, as our 3D laser scanners can register coordinates of up to millions of points per second. Optimisation is an important aspect already at the data capture stage, and it is good to define the exact objectives of the use as early as possible.

When the HSM project was launched, it was defined based on the USIBD (U.S. Institute of Building Documentation) v2.0-2016 document (link), which has been updated to 3.0 in 2019, and was also defined in the Lechner Center’s BIM Manual (link), which was published in autumn 2019, and will be included in the harmonized standard MSZ-EN ISO 19650. In modelling, this meant that, for example, to capture the plane of a wall surface with crumbling plaster and a slightly different vertical surface, it is necessary to determine the maximum difference of millimetres between the model and reality. While the measuring tool is capable of the most accurate category, the rational demand for architectural use in survey design is around 5 centimetres accuracy (which is demonstrably more useful and effective in terms of material and human resources compared to the inaccuracy and time-consuming nature of a manual measurement). In the case of certain details, such as building decorations or sculptures, the survey model often has to meet stricter criteria. For example, a BIM model may be expected to be able to automatically consolidate these details and to be a physical model element that can be used for a heritage inventory or for restoration and building diagnostic documentation, and to which additional valuable information can be linked at any stage of the building.

At TSPC, we were already monitoring national standards and documents from several countries prior to the ISO standardisation processes in our country and integrating them into our own company systems. This practical knowledge and experience has been made available to support the work of the Hungarian BIM standardisation body and has also been applied to a development project at Semmelweis University. From the outset, the BIM documents associated with the design task has had to include the elements that are now included in the standards.

A specific technical challenge of the HSM project was that at that time there was no standardised BIM document available for the contractors, such as an EIR (Exchange Information Requirements) to define the information exchange requirements, so this had to be prepared together with the BEP (BIM Execution Plan) document. This document determines how BIM requirements are to be met throughout the project. So the first step was to define what, when and exactly for what purpose we would model from the highly detailed point cloud, how we would do it (at what level of detail, with what geometric accuracy and with what key information content) and how this would be extended during the design phases.

It is also an exciting discovery to create a survey model that shows reality in 3D on one screen, and on the other screen you can virtually ‘rediscover’ how our ancestors built. An architect’s knowledge of building structure and the history of architecture is useful here, but it is also necessary to look ahead, what and how we are going to model. A BIM approach and TSPC’s BIM managers help to achieve this. A survey model can now be developed that can also show the number of bricks to be removed. We were approached by the contractor of another project with a similar structure during construction, and in 1-2 engineer days we were able to generate a point cloud based 3D BIM model of the building, which allowed us to compare and verify the discrepancies between the previous 2D architect’s plans and reality, and to obtain more accurate model-based quantitative information.

Modelling historic structures

In a classical BIM model (completely new building, clean formula, clear framework), it is possible to focus on automation, efficiency, economy. For a BIM model used to redesign an existing building complex with historic structures, these are critical aspects, but there are also a number of relationships that complicate the formula, all of which need to be taken into account and incorporated into the model at the information level. During planning, this gives the opportunity to simulate in advance different spatial and temporal organisational solutions, such as how and which part of the institution can continue to operate and when a particular department has to move to which part of the building. Construction can be ensured during operation, and during execution you know exactly what is happening and when and how much it will cost.

Unique stairs and handrails

Typically, block staircases with arched arms, drawn steps and wedge-shaped block stone staircases are required to be modelled, which are a challenge for modern BIM architectural software. In many cases, strategic cooperation with software vendors, such as Graphisoft, is necessary and in-house solutions need to be developed in parallel with the project.

Efficiency and economy are important. To simplify it to one thing, you could say that we are modelling only what we also quantify.  The reality is, of course, more nuanced, with many of these requirements to be met: quantification-architecture-rationality-economy-information loss-avoidance-buildability, organisation, etc.

Historic slab structures

It is typical for buildings of this age to have a brick vaulted basement, slabs between floors of one of the steel-beam-brick slab types, while the end slab is often of timber, in some cases dense-beam wood. Typically, for a slab with beams, clever modelling will both show the exact quantity of material (beam length, section type, brick quantity, infill quantity) and provide the correct technical representation without extra data processing on the sections.

Unique windows and doors and locksmith structures (railings, decorations, grilles)

The project presented here – and buildings of this type in general – is characterised by a much more varied and unique design of the windows and doors than is the case with the structures in common use today. It is often accompanied by accessories such as security grilles, window grilles, building ornaments and sophisticated locksmith structures. Modelling these usually requires custom solutions, as the primary targets of modern BIM design software are not historic buildings. The content and appearance of the model are fundamentally important from an architectural point of view, and 3D modelling is also inevitable because the section, façade, perspective view taken at any point of the building is a representation of reality and is updated immediately during redesign. There is no unnecessary, repetitive extra work like in previous 2D processing.

Roof structures

The point cloud survey helped to record the current condition of the timber roof structures for diagnostic testing, and more complex documentation was available on site by modelling the major deflections, buckling and post-tensioning of nodes with steel beam reinforcement. Thanks to technological tools, it was possible to send information back to the design team from the site via a tablet and to refine some of the data, mark the elements to be replaced and precisely mark the overlapping structures. Normally these are time-consuming and drawing-intensive tasks, but with the BIM model this often 1-2 month engineering task can be reduced to 2-3 days, while being documented in a much more readable way. The information collected and further developed during this process is then valuable during operation, as it can be developed into a precise and informative structure for the institution’s technical experts, into an operational model that can be well planned and calculated.

Information content from the elements of the BIM model

BIM documents predefine, by design phase, which elements must contain which information, which can be accessed from any view, retrieved, automatically captioned. In addition to the geometric information, each element also has a required minimum non-geometric information content, which can be used to identify: the model element type, identifier, name, classification, foil, rebuild status, structural role and other characteristics. Among other properties, there are project-specific elements that belong to the critical minimum information content, but only for a specific project. For example, in the case of the HSM project, such essential but unique characteristics include the ‘Building section’ code, the definition of the ‘Rebuilding’ additional information and the definition of the ‘Schedule’ sequence. Since it can be divided into several building units, it is always necessary to know exactly where the element belongs. In the same way, it is not enough to determine at the stage of reconstruction whether a certain element is existing, to be demolished or new, nor even to determine at which stage it will be demolished; for example, in the case of an existing opening window protected as a monument, it may be necessary to determine whether it needs to be rebuilt in its original structure, whether it is sufficient to renovate only its surface, or whether it can be replaced entirely by a new structure, since it must meet energy requirements that are quite different from the original in order to be modern. For many structures that cannot be precisely defined without exploration, it is also possible to mark them in the model, for example as hypothetical structures. With this information, either during diagnostic testing or during construction, specific documentation can be automatically generated from the model to help prepare for and manage unforeseeable events in the field.

Staff list

Participants in the BIM (building information modelling) processing of the survey plans for the project presented:

Csilla Szántó Project Manager Architect

Andrea Tóth-Lovrity Project Manager Architect

Enikő Barta Architect

Máté Csapó BIM Manager

Tímea Dittel Architect

Zoltán Écsi Architect

Tamás Holics Architect

András Kauth BIM Manager

Henrietta Kovács Architect

Dóra Szalai BIM Manager

Éva Zsemlye Architect

and LIMA Design Kft. as a consortium partner of TSPC.