The Industry Foundation Classes (IFC) is an open standard in construction for the digital description of building models. It is also referred to as BIM (Building Information Modelling).

Logical building structures (e.g., walls, slabs, openings) and their related properties (e.g., material, component strength) are mapped. With the help of IFC files, complex spatial planning data can be transferred between different software systems.

IFC is supported by numerous software for the exchange of building data. Its application areas are, among many others, 2d/3d CAD, static and energy analysis, and determination of quantities or costs.

AxisVM IMPORT #

AxisVM supports the import/export of IFC files from versions 2.0 through 2×4 (current Version, also referred to as IFC4). IFC files can be imported through the menu File / Import.

In case the IFC file is not shown, the file type must be changed (selection  menu at the bottom of the window).

In import dialogue, several options can be chosen.

If an IFC model is already imported into the current model, it is possible to update it to readjust changes. The modifications are documented in an additional window.

Automatic detection of changes: This function lists new, modified and deleted objects when reimporting IFC files. Each change can be approved or ignored. Selecting a difference in the tree, shows the selected element’s position within the current model.

Filtering objects: the user can select elements according to different criteria.

Files with format IFC 2×4 (current version) can contain the definition of loads, supports and joints, as well as other structural elements. In this case, the option „Static model“ at Import Method is available for reading the file.

After importing the file, the architectural model will be visible in AxisVM.

The individual components are colored by type.

	Wall (vertical surface), brown
	Slab (horizontal surface), green
	Column (vertical bar), blue
	Beam (horizontal bar), yellow
	The quick access button (bottom right) toggles the visibility and/or snap function for lines and nodes of the architectural model
	The visibility and the snap function of individual object groups on the IFC model can be activated or deactivated from the layer manager

STATICAL MODEL #

The function “Architectural Model” (tab “Elements”) is used for the generation of a static model based on the IFC data.

AUTOMATIC GENERATION #

First, the elements from the architectural model to be edited can be selected.

The model framework will be created from selected layer elements. Columns will be reduced to their axis and walls, slabs and roofs will be reduced to their center plane. Framework nodes and lines become part of the AxisVM model and are independent of the background layer.

After the selection of the desired elements and the confirmation with “Continue”, the components‘ properties can be defined.

The properties are assigned independently for every type of structural element. The component’s thickness (for surface elements) or cross-section (for line elements) can be inherited from the architectural model (“auto”),  or it can be manually set.

If different properties are to be assigned to a single type of structural element, it can be done in multiple steps, selecting only elements with matching properties. Alternatively, the properties can be set uniformly at first and subsequently modified in the AxisVM model.

After the assignment of all necessary properties of structural elements, an AxisVM model is created.

An automatically generated model from IFC data uses the same elements as a model built entirely inside AxisVM. The same procedures to complement and modify the model apply.

ASSIGNING OBJECTS’ PROPERTIES MANUALLY #

When importing IFC files, detecting the static frames of objects is not always possible. Those objects whose static frame detection failed are drawn to the screen with a dashed line. The user has many possibilities to create, modify these objects or delete them from the static model.

POST-IMPORT MODIFICATIONS #

After importing the architectural data and generating the static model, it usually must be edited. Below some typical differences are given between architectural and calculation models.

Depending on the software and procedures used for modelling, additional differences between the IFC model and the intended static system can occur. In any case, the automatically generated model has to be checked and if necessary, adjusted by the engineer. However, the adjustments usually take less effort than the manual modelling of the structure.

WALL/SLAB CONNECTION #

Depending on the input method, it can happen, that walls are extended above slabs. The top edge of the wall has to be corrected so that the axes of both elements connect and this way allows for the consideration of the static relationship between wall and slab.

DETAIL LEVEL & MODEL SIMPLIFICATIONS #

In many cases, the architectural model is too detailed for statical analysis (e.g., minor misalignment of elements). The user should simplify the static model at these points to make the later modifications easier, optimize calculation time and facilitate the result analysis.

CORNERS BETWEEN WALLS #

Corners can correctly connect between walls (left picture, bottom walls), or a gap can be between them (left picture, top walls) in the imported structure. The result depends on the input method, and the user can correct them in the statical model.

OVERLAPPING SLABS #

An overlap of slabs may result from the creation of stepped slabs. Such an overlap does not reproduce the structural behaviour of slab recesses. In general, the architectural model doesn’t contain any static connection between the two parts of the slab. Therefore the slab recess has to be modeled manually after the IFC import.

NON-STRUCTURAL ELEMENTS #

Non-structural elements or elements with no static significance (e.g., railings) have to be removed (deleted) from the model. It is essential to ensure that not only the unwanted elements but also the associated geometry objects (nodes, lines) are deleted since there will affect the mesh generation.

COMPLEMENTING THE MODEL #

Architectural models do not contain all statically relevant information. Particularly the following properties have to be complemented in many cases.

• Material properties (can be taken from the material database in the generation of the static model)
• Supports
• Element connections (e.g., joints)
• Loads

Source: Ingware.com (Support Book)