I have Produced a simple rocking column pilot model using SAP2000 and am getting an extremely large period which is incorrect. I have attached the model to this forum. The foundation is 6mx6m and the height and diameter of the column is 12m and 2.5m. I dont understand why I am getting a period of 50000 seconds and there are still large forces being transfered to the structure during an earthquake excitation. I believe the mass used in the modal participation is correct.