I'm sure this is something simple but I've got a model that runs fine without inputted masses. My goal is to determine the period/natural frequency of the structure. Started by running a self-weight only analysis and adding Y supports at all of my nodes. Then took those reactions and applied the same magnitudes as my nodal mass in the Y direction (only supporting the nodes that are actually supported). I've done this in the past with success but I'm getting a very generic "Error during analysis" error. Any thoughts as to what this could entail?
See attached.FF Vibration Test.zip
It helps to tell us what application you are using. In this model, with Ram Elements version 16.02.00.88 I get some instability warnings in analysis.
[Information] Active degrees of freedom 6 (Tx Ty Tz Rx Ry Rz)[Warning] Local instability at or near Node Node 118[Warning] Local instability at or near Node Node 119[Warning] Local instability at or near Node Node 120[Warning] Local instability at or near Node Node 118[Warning] Local instability at or near Node Node 119[Warning] Local instability at or near Node Node 120[Error] Error during analysis
This is due to having hinged members connected to pinned supports. That leaves the node(s) free to rotate. Ether don't hinge the beams (and fix one end against rotation), or make the supports rotationally fixed to avoid the problem.
See also: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3038/ram-instability-in-finite-element-analysis-tn