## 3 Case Study: Generation of the Structural Model
### Physical Model  
* The modelling software used was Revit from Autodesk. In the process, several significant distinct ways of working were verified during the conception of the structure:
* Revit enables the introduction of the coordinates in the survey point and project base point allows all objects to have their real coordinate and elevation associated;
* Since the process involves 3D modelling, when the solution is created in a plan view, it will be reflected in all other plans;
* An additional advantage is that the structure can be observed in a 3D perspective, contributing to a clear understood of the solution in progress;
* The project browser, associated to the model, presents an organized directory in order to support collaboration and coordination, avoiding inconsistencies between disciplines or tasks;
* The schedules of material take-off are dynamic tables that can be always be updated, following the solution alternatives or adjustments;  
Figure 1: A realistic image of the structural project and the foundation plant [20]. * The project represented in a BIM model form, can be easily examined simplifying the detection of inconsistencies, regarding the type of information associated with each object. Revit software includes a structural menu with a wide variety of parametric objects representative of the most frequent structural components, facilitating the modelling process of the required structural solution. First, the available CAD drawings, representing each structural plant, were imported and positioned over the correspondent level of the model. After, level by level, the necessary structural elements (columns, beams and slab) were selected, retrieving them from the concrete reinforcement's components library, and then adjusted in order to represent, with correctness, the established structural solution. Initially, some basic definitions were considered, in particular the work unites and the materials, associated to the adequate mechanical characteristics, namely, the Concrete C30/37 and the Steel A500 NR SD (Table 1). The values of the mechanic properties were introduced with their correct values, as they are later used in the structural analyses stage. The modelling process of the structural solution is then initialized. A floor solution is defined based on the size of the spans between the columns and the presence or absence of beams. All the elements were pre-sizing, were the thickness of the slabs, the cross-section dimensions of the beams and the columns, and finally the dimensions of the foundation elements, were established (Figure 2). The beams and columns were adequately positioned according to the grids outlined. The modelling system allows to replicate the modelled elements from one floor to the others, speeding up all process. Since the upper floors were similar, this feature was used, replicating the structural elements from the level 0 to the other 3 floors. In addition, the building presents a stair column and an elevator core (Figure 3):  
* The stair element was first modelled only as an architectural element and, therefore, it cannot be associated with an analytical element or modelled with reinforcements. To solve this problem, the stair was created as a sloped floor element, which belongs to a structural category. Thus, as it was modelled as a structural element of the category slab, with the geometry of the stair, later, it would be possible to insert reinforcement in it;
* The elevator core is composed of three structural walls with 25 cm thickness and the wall with openings with 25 cm. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Materials** & & & **Proprieies** & \\ \hline Concrete & fck (MPa) & fcd (MPa) & fctm (MPa) & Ecm (GPa) & \(\gamma\)c (kN/m\({}^{3}\)) \\ C30/37 & 30 & 20 & 2,9 & 33 & 25 \\ \hline Steel A500 & fyk (MPa) & fyd (MPa) & Es (GPa) & \(\gamma\)s (kN/m\({}^{3}\)) \\ NR SD & 500 & 435 & 200 & 78 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of design materials.