Prototyp - ISA

SOF - Athens. An interactive graphical model generator for the complete structural analysis model of building structures has been developed.

Considerable time advantages and flexibility will enable faster design cycles and study of more variations. Object oriented concepts will enable future extensions and easy integration of additional modules.

The prototype is a highly interactive system integrated within CAD as much as possible.

Additionally, a reinforcement design expert system is developed which suggests based on a knowledgebase several suitable arrangements of reinforcement to the user. The system consists of two separated system components: a process model to depict the design progress and a product model to represent the basic design objects which are concrete members and their reinforcement.

The used CAD schema of the layer structure includes a topology like 'who' author, 'where' localization, 'what' contents etc. The attributes are divided into categories which are identification attributes, relation attributes and characterization attributes. A further classification needed is according to disciplines. The instances for the different attribute classes which are necessary for structural analysis applications are summarized like:

• identification attribute like beam element or elastic support element
• relation attribute like number of cross section
• characterization attribute like concrete or steel type.

Integration of structural analysis with its specialized, highly optimized database and data generation within the product model is carried out with a direct interface from the structural analysis database to the product model on the basis of ISO 10303 (STEP).

The structural analysis model generation has the following capabilities:

• As much as possible automatic generation of the structural analysis model. Additionally, it is able to set all the necessary elements of the numerical model directly on the architectural model.
• All physical properties like thickness, material constants etc. can be taken (if possible from the product model), automatically into account.
• The elements that are being generated fulfil as much as possible all the requirements for numerical stability and convergence.
• The finite element mesh takes into account all geometric discontinuities that affect the precision of the computation.
• Automatic application of the boundary conditions and the loading.
• Automatic optimization of the profile and the bandwidth of the stiffness matrix is implemented.

Between the structural analysis database and the drawing file there exist an unambiguous correlation. That means that it will be possible at any time to convert the finite element database into a drawing file and vice versa.

Automatic mesh generation is very important for the practical use of finite element methods. Two types of automatic mesh generation have been incorporated. The macro element technique (mapped mesh) and the free (fully automatic) meshing technique. The main advantage of the free meshing technique is that it can generate strongly graded meshes on arbitrary domains.