- 360 Publisher
- Alias
- AutoCAD
- AutoCAD Civil 3D
- AutoCAD Electrical
- AutoCAD for Mac
- AutoCAD LT for Mac
- AutoCAD Map 3D
- BIM 360 Glue
- Building Design Suite
- Constructware
- Creative Finishing
- Design Review
- Factory Design Suite
- Flame Premium
- Green Building Studio
- Infr. Map Server
- Infrastructure Modeler
- Installation Help
- Inventor
- Inventor ETO
- Inventor Fusion
- Inventor Fusion Technology for Mac
- Inventor LT
- Inventor Publisher
- Navisworks
- Navisworks Freedom
- PLM 360
- Product Design Suite
- Project Galileo
- Project Photofly
- Project Simulus
- Revit
- Revit LT
- Robot Structural Analysis Professional
- Sim 360 Pro and Sim 360 Moldflow
- Simulation 360
- Simulation CFD
- Simulation DFM
- Simulation Job Manager
- Simulation Mechanical
- Simulation Moldflow
- Simulation Moldflow Adviser
- Simulation Moldflow Communicator
- Simulation Moldflow Insight
- Simulation Moldflow Insight 360
- Smoke
- Vasari
- Vault
Table of contents
No headersAfter creating a simulation and establishing the parameters that you want evaluated, you then run the simulation. The simulation produces a set of results for all the combinations of parameters you have defined.
A simulation performs the following tasks:
- Creates the simulation.
- Performs static or modal analysis.
- Displays error and warning messages about analysis allowing you to change the input data.
After the simulation, evaluate the results in the graphics region.
Running a simulation
Running a simulation produces the analysis results for all the combinations of the defined variables. Before you run a simulation, we recommend that you complete the following tasks:
- Confirm that all components use correctly defined materials with sufficient definition for simulation.
- Loads are assigned.
- Constraints are applied.
- Assign releases or rigid links, as needed.
- Exclude components that are not affected
by the forces and deformation from the simulation:
- Open the assembly browser under the simulation node (Simulation browser view).
- On the context menu, click Suppress.
To run a simulation,
click the Simulate command 
in the Solve panel. Alternatively,
in the Frame Analysis browser right-click the Simulation node and
select Simulate. The progress bar displays showing the status of
the simulation.
To cancel the simulation in process, click Cancel or the ESC key.
When you run the simulation
and there are some problems in your frame model there is a high
probability that the results are invalid. A warning icon 
displays before the Results browser
node. Expand the Status folder in the browser to see the list of
errors and warning messages. We recommend resolving any warnings
that are displayed to get correct analysis results.
When producing simulations,
you can modify parameters: change beam materials or properties,
add loads, constraints, define rigid links, or assign releases.
The Results become out-of-date. A browser decoration icon 
appears next to the Results
browser node. This signifies that the results are out of sync with
the current input. You update results by doing the following:
- Click the Simulate command in the Solve panel.
- Right-click the Simulation node in the browser and click Simulate.
Common warnings or errors in simulation
Following is a list of
some warnings and errors that can occur when you run simulations and
how to resolve them. The Warning and Error 
icons associated with messages
indicate whether the process can or cannot proceed without modification,
respectively.
The error and warning messages are displayed in the separate dialog box, as well as in the Status folder in the browser.
The error messages indicate a critical error
in your model and the simulation cannot run. No results can be obtained.
Fix such errors to run simulation. For example, "No constraint defined"
error indicates that you did not defined any constraint to your
model and simulation cannot proceed without any constraint defined.
Assign a constraint to the frame model.
The warning messages indicate some problem in
your frame model. The problem is not so critical to stop the simulation
so the Results are obtained. However, there is a high probability
that the results are invalid due to errors in your model. For example,
the simulation runs, and the warning message displays "Isolated
nodes have been found." Your frame model contains nodes not connected
with any calculation element or structure object. The results of
the simulation are affected and invalid. We recommend resolving any
warnings that are displayed to get correct analysis results.
Results are accurate when no error or warning message displays.
Note: To minimize the possibility of errors in calculation, for static analysis, select the DSC Algorithm (Beam Releases) option in the Solver tab of the Frame Analysis Setting dialog box.
| No load defined. | Apply loads to your model to simulate the appropriate boundary conditions. |
| No constraint defined. | Apply constraints to your model to simulate the appropriate boundary conditions. |
| Some materials are not defined correctly. | Click Assign Materials to view the material status of the parts. Apply material overrides in the Simulation environment or return to the Model environment and assign materials to the appropriate parts. |
| No frame members were found in the assembly. | Use Frame Generator tools to add frames to your assembly to perform frame analysis. |
Instability (of type 1) detected at node XY. | There is zero value element on the diagonal of stiffness matrix. Caused by mechanical instability of a structure, when a part of the structure is a mechanism (too many releases or incorrect definition of releases, or the number, type and positions of constraints are not sufficient) |
Instability (of type 2) detected at node XY. | There is zero value element on the diagonal of inverted stiffness matrix. Caused by mechanical instability of a structure, when a part of the structure is a mechanism (too many releases or incorrect definition of releases, or the number, type and positions of constraints are not sufficient) |
Instability (of type 3) detected at node XY. | There is a suspiciously high ratio between maximum and minimum values on the diagonal of inverted stiffness matrix Occurs when there are large differences in section profiles of some elements or an abnormally short element exists. |
| Bar superposition. | Occurs when beams in your assembly are overlapping or are placed in the same spot. Bar superposition is not allowed during model conversion and simulation. Delete or move one of the beams in your assembly to resolve the error. |
| Separate structure. | Occurs when the structure model consists of two or more separate parts. It is not an obstacle in calculations, the results are correct. Displays as a warning message whether it is an intended modeling effect. |
Isolated nodes have been found. Isolated node with additional attributes found. | Occurs when model contains nodes not connected with any calculation element or structure object. If the node contains an attribute such as a constraint or load, this attribute does not affect the calculation model. |
| Required number of modes (n) is too big. | The required number of the free vibration modes in the modal analysis is bigger than the number of the dynamic degrees of freedom. The problem usually results from too many constraints or lack of masses in the model. The number of the calculated vibration frequencies will be reduced to the number of dynamic degrees of freedom. |
| Matrix is not positive defined - the critical load may have been exceeded. | The load applied to the structure exceeds the critical load value. The structure is in the unstable region. |
| Modal analysis error: mass matrix is not positive definite. | The modal analysis may not be calculated, the eigenvalues are negative. This type of problem appears in case of an incorrect model which is an unstable mechanism. |
| No convergence of nonlinear problem. | The calculations of the non-linear problem assume applying the full load into equal increments (by default - five). The solution for each increment is calculated iteratively. If the solution is not found - the process diverges, the load increments are automatically reduced. If the assumed number of steps is exceeded without reaching the full load, the lack of convergence is reported. The results are results for an incomplete load. To improve the convergence, the following parameters of the non-linear case may be changed:
|
The use of elastic or non-linear releases needs using of the DSC elements. It is suggested to use "DSC algorithm" in case of dynamic and non-linear analysis of structure containing released directions. | DSC algorithm introduces hidden, zero-length, two-node beam element instead of the released element node. It is an alternative solution for the static condensation of the stiffness matrix, which gives correct solution for the typical problems of the linear analysis. Using the DSC elements improves the convergence for the non-linear analyses, and gives more precise results for the modal analysis if the elastic releases appear. |