Mass Source / Effective Seismic Weight

Using Define>Mass Source, CSiPlant enables users to define an unlimited number of “Mass sources” which can convert selected gravity-direction (-Z) assigned loads into equivalent mass in all 3 translational directions (X, Y, and Z) for use in static acceleration load cases and dynamic analysis load cases. 

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 in the structural model. Those gravity-direction loads need to be considered in the calculation of static acceleration loads and for analysis of all dynamic analysis cases. If, for example, a user assigns a 450 kip gravity direction load on the structure to account for the weight of fin fan air cooled heat exchangers, that load should change the calculated natural frequency and also change the static seismic load calculation for that model. 

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.

Define menu>Mass Source is also used to define Center of Gravity (CG) cases with CG reported in Display menu>Show Tables>Analysis Results>Joints>Assembled Joint Masses report. This enables users to consider multiple different CG scenarios all in the same run.

Mass source functionality is available with all CSI structural analysis software products.