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: actualization of the stiffness matrix after each iteration (the full Newton-Raphson method) increase of the number of load increments or iterations decrease of the tolerance of the solution
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.