Only the first " n " of required " m " Eigen values found. The solution guarantees that these are lowest frequencies (i.e., largest periods). This partial result may satisfy the design requirement regarding mass participation. To use this result, set required number of Eigen values for Load Cases to " n " and re-run the analysis. Or increase the number of Eigen Values searched and re-run the analysis.

Solution:

The program generates this error message if it fails to find all eigenvalues (i.e., structural periods) requested by the user. The Eigen solution is a sub-space iterative method in which the program creates a sub-space of the real problem (reduced system) and tries to convergence iteratively to lowest frequencies (or highest periods). The error message indicates that the program successfully found the first "n" eigenvalues and it is assured that they are the highest periods (i.e., till the first "n" value, no eigenvalues are skipped). If the design criteria for total mass participation is satisfied with these "n" periods, the user can use this result first setting number of eigenvalues searched to "n" and re-run the analysis again.

This kind of behavior is usually observed when some part of the structure is too stiff compared to other part of the structure or many nodes at a story level are disconnected and only a few nodes are attached to rigid diaphragm at the same story (again not uniform stiffness distribution) and hence, the solution experience some numerical trouble in converging.

Eigen Analysis Failed. Any Modal instability, Severe P-Delta Effects, Irrational Stiffness\Mass Distributions or Improper Node Connect\Disconnect Information May Cause This Error. Analysis Terminated.

Solution:

This might be an indication of a poor stiffness vs. mass proportioning or unrealistic P-Delta effects. It is advised first to run the model without P-Delta and observe the behavior of the model. Please see "Solution Techniques" and "Pseudo-Flexible Floor Diaphragms" (i.e. Excessive P-Delta Deformation at Story: label ) for limitations of P-Delta method. Sometimes this error is also encountered when too many nodes are disconnected from rigid diaphragms while only a few nodes are connected at a particular story level.

Also, check the mass of each diaphragm; indiscriminate use of the "Combine mass" command could also cause this error, particularly, if the level in question has lateral members.

Response Spectra Analysis: Error Opening File.

Solution:

This error is encountered if the response spectra file is corrupted. Correct or reinstall the file.