What options are available to increase the participation factors in a model with multiple disconnected systems in AutoPIPE?
The participation factors can be increased by increasing number of mass points so that missing mass at the supports is minimized. However, that may not be effective for all models. Another way to have more mass is to add more modes up to the limit of 999. Change the Modal analysis setting for number of modes to 999, before analyzing the model
In large models with multiple disconnected systems (segments that represent other systems of piping not all connected in one group, check groups of segments by pressing Select> Connected Segment> provides a list of segment groups or disconnected segments) another more effective way is to reduce the model size, so that more modes can be analyzed in a smaller model.
If needed, create a new model for each disconnect found in the original model. If some of these disconnected piping has a much larger frequency, then you will not get a single mode for that subsystem and the analysis may not be correct even if there model achieves 95% modal participation.
For ZPA option, this options will essentially impose a static force just like static earthquake analysis and would apply to subsystems with no frequencies. Subdividing the model is more important for shock or water hammer type of loading since the loading have a higher frequency.
What are the Participation Factors and the Captured Modal Mass
Comments about Modal Analysis
"Frequencies" sub-report
Bentley AutoPIPE