Solid Models

Stress distribution on a solid model bridge
Stress distribution on a solid model bridge

Solid elements are used if a structure geometry, which is to be analyzed, cannot be described adequately by beam or area elements or if the ascertainment of the three-dimensional stresses is necessary for the evaluation of the structural behavior. Examples are the dynamic analysis of machine foundations or the calculation of concrete bridges with a complex geometry. The ability to model realistic support and connection conditions with contacts or nonlinear bedding also makes solid elements useful.

Mode shape of a machine foundation
Mode shape of a machine foundation

Solid Models:

  • Structure generation with model objects
  • Definition with extrusion of sections or polyhedron objects
  • Direct mesh generation of IFC objects (BREP)
  • Automatic mesh generation with local refinement
  • 8 and 10 node elements
  • Free point, line and area loads
  • Linear temperature fields
  • Free tendon layout / prestressing
  • Stability analysis
  • Nonlinear supports and bedding
  • Contact elements
  • Plastic theory (Huber-von Mises, Raghava, Rankine)
  • Thermal analysis

Modeling

Model objects are used to define a structure model. They consist of freely combinable partial solids that are created by the extrusion of sections or by entering polyhedrons with four to eight corners. Object properties like material, color, layer etc. can be assigned immediately. Bedding and contact properties can be defined at each model surface. Afterwards the complete solid model is meshed with tetrahedron elements taking into account all boundary conditions.

Loads

All necessary load types are available for the analysis of solid models:

  • Dead load and nodal loads
  • Free point, line and area loads
  • Support displacement
  • Linear temperature fields
  • Free tendon layout / prestressing
  • Creep and shrinkage
  • Load model 1 for bridge constructions
  • Dynamic train load

Analysis

For the FEM analysis a tetrahedron element with 10 nodes is available, which can exactly describe linear stress distributions and hence has a very good convergence of results. Also a high computation speed is associated with this element. Additionally to the static and dynamic abilities mentioned above stability analyses (second order theory, buckling, bulging etc.), contact elements and plastic material behavior (Huber-von Mises, Raghava, Rankine) are implemented.

Thermal Calculation

This allows the determination of transient temperature distributions in solid models. The thermal properties are assigned to the the solid faces. For the determined temperature distributions, the stresses and the strains can be calculated.

Results

The possibilities of result preparation are important to evaluate the quality of a calculation. They are necessary to understand and document the structural behavior. Among others the following result representations are available for solid models:

  • Deformation with animation
  • Color surfaces
  • Three-dimensional isosurfaces
  • Surface sections
  • Solid sections
  • Principal stress vectors
  • Integral internal forces for checks
  • Temperature distribution

After integration of the stresses with design objects, internal forces are available for the checks.