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Turkish Good work. I am preparing my second project in version 10. My first project was a one-story building. Now I'm dealing with a 5 storey building. The 1st free vibration period of the building seems to be too long. In a 5-storey building, it should be around 0.5-0.6 seconds, but around 0.9 seconds. I exported the ide model to Sap2000 and checked it in Sap2000. Sap2000 gave a value close to what I expected. Since my model has a basement and a raft, I set up another trial model with a very simple carrier, without a 5-storey basement, in case I'm making a mistake. In this model, the result given by İdecad in Modal E1 is 0.91 seconds, while the result given by the same model in Sap2000 E1 is 0.58 seconds. I don't think it's normal to have that much difference. Or is there something I don't know about, I wanted to ask. Attached are trial models.
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Inconsistency in Modal Analysis
- Thread starter miralay
- Start date
nurgulkaya
New Member
Hello there; The reason for the difference in modal analysis is that while effective section stiffness is used in ideCAD, you do not use it in sap2000. When entering information in Sap2000, the following operations should be done: 1- If fully rigid diaphragm is used, beam sections must be entered with a table 2- Effective section stiffnesses must be entered 3- For modeling of rigid arms, only the rigid zone factor=0.5 in the end length offset sub-tab on beams should be taken. Good work.
Ms. Nurgül, frankly, I did not think that there could be effective section stiffnesses. Because as an engineer, I would like to see the current behavior of the structure first. In that case, can I create a new modal analysis myself and get a solution without using effective section stiffnesses?