Working with Structural Applications
Structural applications can be divided into the following main categories:
•Analysis and design (steel, reinforced concrete, timber etc.) applications
These applications carry out and document static calculations based on various techniques (e.g. finite element method).
These carry out preparatory tasks and ensure the connection between the analysis application and the architectural profession.
•Detailers (steel, reinforced concrete, precast, etc.)
These create detailed construction documentation of the structure and communicate with the manufacturers.
Some applications cover several of these functions. This diagram describes the general workflow for data exchange between ARCHICAD and a structural application:
Types of Structural Applications
The most complete level of interoperability is achieved using an intelligent 3D model connection - as opposed to a drawing representation - in which the building model being exchanged represents 3D structural objects (slabs, walls, columns, beams, windows, roofs etc.), each with specific, defined attributes and properties.
Model-based exchange between the architect and the structural engineer can follow one of two concepts:
•managing a reference model; or
•converting the model to native formats.
The reference model concept ensures the “security” of the architectural model and the structural model files, since each office remains responsible for his/her own model. Thus, the structural engineer receives a file from the architect, but does not modify it; he/she uses the architectural information as a basis for building up his own structural model. This occurs manually, using the tools of his own software, but automatic element conversion utilities also exist to speed up the process. Similarly, the architect leaves intact the file received from the structural engineer, while taking into account its suggestions for modeling load-bearing elements. This way, each discipline’s own file is independent of the one received as a reference.
ARCHICAD Structural Workflow
The other approach to model-based exchange is to convert the other party’s model elements into the native format of one’s own application. The converted model is transformed according to the specifications of the recipient, so the original version of the model is not preserved. This approach is most typical of data exchange between architectural and analysis programs.
ARCHICAD can combine the advantages of both approaches. The 3D model obtained from the structural engineer - regardless of the method used to import it - is always transformed into native ARCHICAD elements. At the same time, it is possible to use the imported elements as a reference, since they can be automatically placed onto their own, protected layers (which are locked to prevent editing). This reference-model approach is also supported by the Merge and Link workflows. Since the incoming elements or modifications are converted into native format, they become an active part of the architectural model, while retaining their properties (e.g. material, profile) assigned in the structural model.
The 3D models exchanged between the architectural and structural disciplines can be considered in three categories:
The architect works on the architectural model, based on her own design and on the client’s requirements. Already during the design phase, the architect should keep in mind that the model will later be exchanged with a structural engineer. For example, she can define the building elements’ structural function; define initial materials to be used; choose columns and beams with standard profiles; define the load bearing core of composite elements. In addition to this preparatory work, she can filter the model so as to narrow down the data to be exchanged: this way, only the structural model, containing just structural elements, will be exported. Naturally, the architect can export the entire architectural model, if the structural engineer’s program is capable of filtering and collecting the model data that he/she needs to work with.
Exporting a structural model from ARCHICAD is sufficient for data exchange with most structural applications (the “management” and “detailer” types). However, analysis and design softwares require the so-called Analysis model in order to run their calculations. These applications can often convert the structural model to Analysis model themselves, or they can use the Analysis model converted by a management/detailer program as the input. An Analysis model is a 2D or 3D representation of the structural model that includes not only planes (in the case of wall, slab, roof elements) and axes (columns and beams) of elements, but also their structural characteristics (e.g. stiffness, material, profile). The simplified analysis model also differs geometrically from the structural model: for example, curved surfaces are represented as a collection of planes; element intersections may be modified.
The export and import of 3D model data often takes place using IFC. In addition, many applications provide native Add-Ons for data exchange with other specific programs. Some engineers or applications (especially analysis applications) will just exchange data at the most basic level: they import CAD drawings (that is, the lines and points representing floor plans, sections and elevations), and use them as a reference for building the analysis model.
Models and drawings are often accompanied by other documentation, such as suggestions or reports; the most commonly used format for these is PDF. ARCHICAD contains a number of techniques for displaying the structural model and for differentiating it from the architectural design. In addition, ARCHICAD can interpret and store the imported structural data, such as the proposed or utilized materials, and the properties of profile elements.
ARCHICAD provides built-in tools and IFC specific settings to support model exchange between the architectural and structural professions. These include:
•Partial Structure Display: Use this to view the simplified load-bearing structure of architectural models.
See also Partial Structure Display on page 95.
•Layers and Layer Combinations. Use customized layer settings to show/hide sets of elements for structural purposes.
See also Layer Display Modes on page 96.
•IFC export settings can be customized to save a structural view containing only the objects which are important to structural engineers.
Architectural vs. Structural Model
•Use the Trace & Reference tool in ARCHICAD to visualize the differences (for example modified position of walls, columns, increased/decreased thicknesses and sections etc.) between an analyzed structural model saved as an IFC file and its original.
See also Trace & Reference on page 97.
The architectural-structural workflow usually requires several “round trips” of information exchange. For example, depending on the results of strength analysis and design calculations, the structural engineer may propose changes in the size (thickness, height, profile etc.) and the position of structural elements. Many applications, including ARCHICAD, have functions that serve to detect and manage these geometrical changes. ARCHICAD’s model-based change management feature and the Trace & Reference tool help to keep this process transparent.
As part of an IFC model-based data exchange workflow, ARCHICAD’s Detect IFC Model Changes tool enables you to:
•compare two subsequent versions of a structural/mechanical model (IFC files),
•identify the differences between the two versions (new, deleted and modified elements),
•insert the changes into the current ARCHICAD model or into an empty ARCHICAD project file,
•list the changes as ARCHICAD Mark-Up Entries.
The controls of the Mark-Up Palette enable you to easily navigate among the changed elements in both 2D and 3D windows and to differentiate and select them, so you can carry out the needed changes in the architectural model.
When merging several versions of structural/mechanical data (whether model-based or drawing based) into ARCHICAD, you can place each subsequent version onto its own layer, and save them as separate views. Next, you can open one view, then use the Trace & Reference function to display another view – representing the other variant - alongside or on top of the first one. The program does not recognize the changes automatically, but you can use the Trace functions to identify changes visually in the Floor Plan, Section/Elevation/IE, 3D Document, Worksheet, Detail or Layout windows. Next, you can carry out the needed changes manually in the ARCHICAD model.
Detect IFC Model Changes