Function
- Specify the iteration method and convergence conditions for performing a nonlinear analysis reflecting large displacement and material nonlinear analysis . The large displacement analysis can be applied to both general static analysis and construction stage analysis. Material nonlinear analysis can only be applied to static analysis. Prior to an analysis, specify the sequence of applying loads in Loading Sequence for Nonlinear Analysis, and define the convergence criteria for nonlinear analysis in Nonlinear Analysis Control. Specified loading sequence is effective when Newton-Raphson and Displacement-Control are selected as the Iteration Method. Large displacement analysis and material nonlinear analysis can be performed on Truss, Plate, Plane Stress, Plane Strain, Axisymmetric, and Solid elements.
Note
Tension-only/Compression-only element will be changed to Truss element in Eigenvalue Analysis.
Call
From the Main Menu select [Analysis] tab > [Analysis Control] group > [Nonlinear]
Input
Nonlinear Type
Select a type of nonlinear analysis
Geometry Nonlinear : Geometric large displacement nonlinear analysis
Material Nonlinear : Material plasticity static analysis
Note 1
Following elements can be used in geometry nonlinear analysis and/or material nonlinear analysis
| Element | Geometry Nonlinear | Geometry Nonlinear (Initial Force for Geometric Stiffness) | Material Nonlinear |
|---|---|---|---|
| Truss | O | O | O |
| Tension only | O | O | O |
| Hook | O | O | O |
| Cable | O | O | Δ |
| Compression only | O | O | O |
| Gap | O | O | O |
| Beam | O | O | Δ |
| Plate Thick | O | Δ | O |
| Plate Thin | O(Considered as Thick Plate) | Δ | O(Considered as Thick Plate) |
| Plane Stress | O | Δ | O |
| Plane Strain | O | Δ | O |
| Axisymmetry | O | Δ | O |
| Solid | O | Δ | O |
(O : Analysis can be performed. / X : Analysis cannot be performed. / △ : Corresponding elements are considered as linear elements and then analysis can be performed.)
Note 2
Geometry nonlinear analysis and/or material nonlinear analysis cannot be performed for the items marked ×.
| Limitation | Geometry Nonlinear | Material Nonlinear | Material + Geometry Nonlinear | Remark |
|---|---|---|---|---|
| Beam End Release | O | O* | O | |
| Plate End Release | O | O* | O | |
| Pretension Load | O | x | x | |
| Prestress Load | O | x | x | |
| Initial Forces for Geometric Stiffness | O | x | x | |
| Temperature Loads | O | x | x | |
| Material=SRC | x | x | x |
In case of Beam End Release and Plate End Release, the material nonlinear analysis cannot be performed for the following case:
1) When Load > Nonlinear Analysis > Loading Sequence for Nonlinear Analysis is used
Note 3
Analysis result is produced only at both I & J ends of elements in geometry nonlinear analysis.
Iteration Method
Select the method of iteration.
If Newton-Raphson is selected
Number of Load Steps
Divide the total load into the number of Load Steps and apply the loads by each step.
Maximum Number of Iterations/Load Step
Maximum number of iterations of analysis per Load Step.
If Arc-Length is selected
Number of Increment Steps
Maximum Number of Iterations/Increment Step
Maximum number of iterations of analysis per Increment Step.
Maximum Displacement Boundary
Magnitude of maximum displacement
Initial Force Ratio for Unit Arc-Length (%)
Ratio of the Initial Force per Unit Arc-Length
Note
Real number (decimal) can be input.
If Displacement-Control is selected
Number of Displacement Steps
Divide the total displacement into the number of Displacement Steps and apply the incremental displacement by each step.
Maximum Number of Iterations/Increment Step
Maximum number of iterations of analysis per Increment Step
Master Node
A reference node for displacement control
Direction
Direction of the displacement control
Maximum Displacement
The magnitude of maximum displacement to be applied to analysis
Convergence Criteria
Specify the basis on which to assess the convergence.
Energy Norm
Assess the convergence on the basis of Energy (Member force x displacement) Norm.
Displacement Norm
Assess the convergence on the basis of Displacement.
Force Norm
Assess the convergence on the basis of Member Force Norm.
Note
The selection of the convergence criteria for repeating or ending the analysis must be based on the condition to reflect the effects of various degrees of freedom. For example, in the case of Displacement Norm, if the displacement resulting from the corresponding analysis step is {D1}, and the total displacement accumulated from each step is {D2}, the Norm is expressed as . If this value is smaller than the specified value, a convergence is considered to have occurred and the program stops the iterative analysis.
The Remove Nonlinear Analysis Control Data Button : Remove the conditions for a nonlinear analysis.
Load Case Specific Nonlinear Analysis Control Data
The above defined Iteration Method is applied individually by load cases. If the same iteration method is applied to all the load cases, this dialog box need not be used.
Iteration Method
Specify between Newton-Raphson and Displacement-Control.
Data for Newton-Raphson/Arc-Length/Displacement-Control Method
Title of Iteration Method specified.
Step : Number of Load Steps entered
Load Factor: load factors for each increment, which can be user-defined or auto-generated by clicking on the Generation button.
8 steps are generated in the Dialog box above in accordance with the Number of Load Steps entered.
Load Factors can be user-defined, or auto-generated by clicking on the General Default Load Factor Button.
Note 1
When Arc-Length Method (ALM) is used to solve the nonlinear equilibrium equation, a real number can be inputted into the 'Initial Force Ratio for Unit Arc-Length (%)' text box in Nonlinear Analysis Control.
Note 2
In nonlinear analysis, the sequence of applying loads can be defined in Loading Sequence for Nonlinear Analysis. Loading sequence can be used when Newton-Raphson and Displacement-Control are selected as Iteration Method. In one model, both Displacement-Control and Newton-Raphson iteration method can be used. However, the load case specified as Newton-Raphson iteration method must be applied in advance of the load case specified as Displacement-Control method.