Civil Engineering Association

the results of modal analysis is not the same in comparison with the results found with the CSI SAP software .. STAADPRO.
if the result of modal analysis is incorrect, the seismic survey will automatically be false

I dont know how are you defining diafragms, or same condition properties, but i guarantee you because it will be muched perfectly,
I can send you same models ( 25 story floors) designed by etabs and rsa 2010, and all eigenvalues ( mode shapes ) are very matched,
But be sure that you are defining same property, conditions, loads to mass conversion, same for both softwares,

regards

Rigid Floor Diaphragm which assumes that the floor is very rigid to experience any in-plane and out-of-plane deformation. The rigid diaphragm action of floors assumes that the floor is stiff enough to undergo rigid body movement.

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The rigid floor diaphragm assumption may not be appropriate if a relatively narrow building has closely spaced shear walls (i.e. the shear walls are stiffer than the floor diaphragm). In the case of a low rise building, the floor diaphragms may be flexible compared to the shear walls as in light wood framed construction. For long narrow buildings with deep beams the rigid floor diaphragm assumption has to be evaluated carefully. The presence of a slab opening for elevators or stairs can weaken the floor diaphragm action. Wood and metal decks without concrete fills may not be modeled as rigid diaphragms unless the floor system is braced properly. Hence, the use of these options in softwar requires good engineering decision making based upon the actual site conditions.

The concept of the "Master-Slave" facility is that the slave node will deflect as it's master node. Precisely speaking, if the master sustains a rigid rotation of theta, the slave will undergo a displacement of the value of the translational displacement of the master plus R* sin (theta) – where R is the distance between the master and the slave. Thus, when you model a rigid link via master-slave it is important to know, which node will primarily be displaced due to the loads applied and which will follow the former due to rigidity in connection. The former should be specified as master and the nodes following it should be specified as slaves. Thus, a specification of master-slave would need an understanding of the deflection pattern of the model under the loads.

(09-02-2010, 09:36 AM)rachid1968 Wrote: [ -> ]dears freinds
dynamic analysis of structures with software versions 14.5-21 robotbat not mention any error messages, but if you throw the dynamic analysis of the same file with the version analyzed robot2009-2011 error messages show the unstable node type "n".
After much checking, I think these versions are a big problem

Try to go to JOB PREFERENCES - STRUCTURAL ANALYSIS and click rlink elements.

I already applied what you have proposed, but the 2009-2011 version still have this problem.
if you make a 3D study of a building wall without bracing, you remarquras the 2009-2011 version work properly without any errors.