https://communities.bentley.com/products/ram-staad/f/ram-staad-forum/179879/period-for-multiple-diaphragms-in-modelHow does RAM calculate the period for a building that has separated diaphragms. Attached is an image of two towers that are connected on the bottom three floors and then are separate the rest of the way up.en-USTelligent Community 12https://communities.bentley.com/thread/523102?ContentTypeID=1Tue, 21 May 2019 16:27:13 GMT6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:416472de-ea2f-40c3-934e-8ccbeb776737Seth Guthrie<p>If you perform the eigenvalue analysis you can report or graphical animate the mode shapes. You should see some modes for the separate towers moving independently.&nbsp; We determine the dominant mode based on mass participation, so the program will probably use a reasonable mode shape for T is static seismic loads, but you can always over ride the T if there is another mode shape you want to be considered for the period.</p> <p>For towers with radically different dynamic behavior, some users want one T used for one tower and another T used for the other tower. That&#39;s not currently possible short of splitting the model into two parts, or using user defined story forces.&nbsp;</p><div style="clear:both;"></div>