Analysis types in FEM-Design
Depending on the current FEM-Design module you can do different calculations: displacement, internal forces, stresses, stability, imperfections, stability analysis, eigenfrequencies and/or seismic analysis. Some extra settings such as cracked-section analysis, non-linear behaviour etc. are also available for certain modules.
- Linear static analysis for all structure types
- Linear elastic and ideal plastic behaviur of supports, edge connections and trusses
- Static analysis according to second order theory for spatial structures, global stability analysis-buckling shapes and critical loads for spatial structures
- Dynamic analysis-vibration shapes and eigen frequencies for all structure types
- Seismic calculation-response spectra method for 3D models
- Non-linear static analysis-supports resisting only compression
- Cracking analysis-tracking of the cracking process
- 3D Solid Mohr Coulomb soil interaction
|Overall features||Advanced features|
Finite element mesh in FEM-Design
FEM-Design offers a fully automatic finite element mesh generation by using optimized (factory default) or custom mesh settings.
The program generates mesh with elements having an average element size optimized for the structure and its environment (supports and loads). The process can contain automatic element refinement and peak smoothing algorithm according to the settings. The generated mesh can be modified with special easy-to-use edit and modify functions.
Finite element types:
Depending on the FEM-Design version (FEM-Design Plate / Wall, 3D Structure / Frame), the engine uses the following finite elements:
|Element type||Finite elements|
|Line elements||Beam and truss|
|2D shell elements||4-, 8-, 9- nodes rectangular elements
3-, 6- nodes triangular elements
|3D volume elements||4-, 6-, 8-, 10-, 17-, 27- nodes elements|
Peak smoothing in FEM-Design
One of the most unique features of FEM-Design is the Peak smoothing that makes it possible to avoid the singularity problems.
As an effect of the mesh refinement, the calculated results are converging to the theoretical solution. The problem is that at certain places we get infinite inner forces according to the theory, so the inner forces increase each time by refining the mesh. These places could be: point supports, endpoints of edge supports, vertices of surface supports, endpoints of beams and columns, endpoints of intersection lines of adjoining surfaces, point loads, endpoints of line loads, vertices of surface loads etc. In practice, usually, the singularity problem occurs at supports because they heavily influence the inner forces (e.g. negative moments) in ratio.
Peak smoothing region
The program defines peak smoothing regions to solve the possible singularity problems. Basically, these regions are the active zones in the environment of the singularity, where the inner forces change substantially as a result of mesh refinement. Peak smoothing regions can be generated automatically by the mesh generator or calculation processes. An automatic generation always results in circular peak smoothing regions with centre points placed in the location of the singularity. The radius of a circular smoothing region depends on the geometry of singularity locations.
All of the available calculation in FEM-Design can be performed with diaphragms or without diaphragms if the diaphragms were defined in the model. By the different types of calculations, the results will be analogous with the adjusted option.
The usage of the diaphragm tool is optimal by storeys of high-rise buildings but the diaphragm modeling tool is also useful by other engineering problems. The diaphragms could be several regions, but they must be horizontal. The shapes of the diaphragms can be arbitrary and they can be separated also on the specific storey levels. There can be more diaphragm regions on the same horizontal level and they will work independently from each other.
There are two different options for the diaphragm calculation:
- Rigid membrane
- Fully rigid
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FEM-Design has all the tools you need to analyze precast concrete structures.
Edge connections with an elastic and plastic definition
The key to good analysis results in precast concrete lies in the connections. It is easy to model the connections both elastic and plastic. In FEM-Design all connection components (but also supports) can be set to:
- “infinite” rigid: blocked motion/rotation
- “free”: released motion/rotation
- semi-rigid: given stiffness value (spring) against motion/rotation
Compression and tension behaviour of connections (and supports) can be set separately, and by components.
The nonlinear behaviour of supports and connections can be controlled by one signed component. It means, if the force in the connection/support happens to act in this selected direction, all spring constants will be set to 0.
The program calculates the forces and/or moments in the connection objects by direction component and their resultants.
Overturning of walls
With the help of resultants of edge connections, wall’s overturning can be examined as below.
Sliding of edge connections
The result is the ratio of the design force and the friction capacity. The friction factor can be set in the edge connection dialogue. Edge connection’s sliding is calculated in each edge connection separately by comparing the x’ component of the connection force as design force, and the limit force calculated by the y’ components of the connection forces and the friction coefficient of the edge connection.
The seismic analysis in FEM-Design
FEM-Design offers the seismic analysis in two of its modules: FEM-Design 3D Structure and FEM-Design Frame.
FEM-Design offers the following methods of seismic calculations according to Eurocode 8.
Seismic loads are taken into account according to the Response Spectrum Analysis method of Eurocode 8 or Turkish seismic code. Only the response spectrum and some additional parameters have to be defined as Seismic load. Required spectrums can be defined with the Seismic load by using standard spectra (automatic) or by manual definition (unique).
Besides displacements, reactions, connection forces and internal forces, the program calculates the Equivalent loads and the “Base shear force”. Results can be displayed by vibration shape (selected at calculation settings), from torsional effect, from sums by direction and from the total sum (Seismic max). If equivalent loads are displayed, also the “base shear force” appears on screen (in grey color). Torsional moment effect on the whole structure can also be displayed, if the torsional effect was taken into consideration during the calculation.