## 3 Case Study
### BIM Model of the Building's State of Conservation
#### 3.3.1 Structure of the BIM and Definition of Parameters  
The modelling software used in this case study is Autodesk's Revit. The set of models prepared for analysis and assessment of the building's state of conservation is the departure point of an information repository on the life cycle of an existing building with the respective periodic updates, which functions as a digital twin of the existing building.  
This updated model enables the building's state of conservation to be ascertained at all times and serves to support the drafting of plans and projects for the management and rehabilitation of the building. In this set of associated models, there is a 'datum' model for non-geometric information (original building plan, reports, energy studies, etc.) and three models covering (by field) the damage to architectural elements (envelope), structural damage and pathological processes detected in plumbing and sewerage installations, to locate damage affecting the four elements required by the specific regulations governing technical inspections of buildings: roof, facade, foundations and structure and the water supply and sewerage installations. Figure 6 depicts the three-dimensional model and the models that have been federated with the architectural model.  
Figure 5: (**a**) Relation of LEICA RTC 360 laser scanning stations; (**b**) point cloud of the building.  
Five sets of parameters were also defined: general data, architectural data, another covering parameters to identify the state of conservation of the elements analysed, a set to assess the intervention needed for each instance of damage and finally, corrective measures. In the latter set, the start and end dates of the damage repair work are defined, another indicates whether or not the damage has been corrected, and the last parameter contains reference information on the intervention carried out. These parameters were defined in the initial contract documentation by means of a table that detailed the parameter's name, description, hierarchy (project parameter, type or exemplar) and type of field (text, URL, dropdown menu, yes/no, etc.). These parameters are shown in Table 2.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter Set** & **Parameter** & **Description** & **Hierarchy** & **Type** \\ \hline \multirow{3}{*}{General Data (GD)} & GD\_Project & Project name & P & Text \\  & GD\_Phase & Project phase & P & Dropdown menu \\  & GD\_Address & Project address & P & Text \\ \hline \multirow{3}{*}{Architectural Data (AD)} & AD\_Original Project & Original project documentation & P & URL-PDF \\  & AD\_BTI & Building Technical Inspection documentation & P & URL-PDF \\  & SC\_Damage Code & Damage codification & I & Text \\ \hline \multirow{3}{*}{State of Conservation Conservation (SC)} & SC\_State of Conservation & State of conservation of the analysed element & I (instance) & Dropdown menu \\  & SC\_Group or element & Analysed group or element & I & Text \\  & SC\_Subgroup & Analysed subgroup & I & Text \\ \cline{1-1}  & SC\_Symptons & Symptoms description & I & Multi-linear text \\ \cline{1-1}  & SC\_Image & Image of the element & I & URL-image \\ \cline{1-1}  & SC\_Severity of damage & Severity of the damage & I & Dropdown menu \\ \cline{1-1}  & SC\_Diagnosis & Description of possible causes & I & Multi-linear text \\ \hline \multirow{3}{*}{Damage Assessment (DA)} & DA\_Assessment & Urgency of the intervention & I & Dropdown menu \\ \cline{1-1}  & DA\_Observations & Explanatory notes & I & Text \\ \cline{1-1}  & DA\_Safety measures & Need for safety measures & I & Yes/no \\ \hline \hline \end{tabular} \(\times\)  
\end{table}
Table 2: Set of parameters on the building’s state of conservation.  
Figure 6: (**a**) Three-dimensional model of the building; (**b**) set of models linked to the architectural model: ‘datum’ model, MEP model and structural model.