...
This unique capability becomes particularly important for realistic pipe-structure interaction since heavy equipment, cable trays, and other objects with significant mass are typically modeled as assigned gravity-direction loads on the structure. Those gravity-direction loads need to be considered in the calculation of static acceleration loads and for analysis of all dynamic analysis cases. If a user builds a structural frame model or imports a structural model, the ability to convert gravity-direction loads into mass becomes a critical consideration for analysis of static accelerations and dynamic load cases. If, for example, you assign a 200 kip gravity direction equipment load on your structure, that load should change the calculated natural frequency of the model. If it doesn't, you have a problem.
In addition, ASCE and other standards require seismic loads to be analyzed for both the scenario with piping and equipment full of fluid contents, as well as the scenario of piping and equipment empty of fluid contents. Using the mass source dialogue, users can analyze static and dynamic seismic loads using a mass source which includes fluid contents and a mass source empty of fluid contents all in the same run for side-by-side evaluation of analysis and design results. Other piping stress and structural analysis programs force users to create multiple separate models with different sets of output results in order to analyze these scenarios.
...