Seismosoft | Earthquake Engineering Solutions

I've prepared a simple model of a frame to perform a eigenvalue analysis but when I apply nodal constraints to it, response parameters are very desultory.
when I remove nodal constraints the results are acceptable.
I need to apply diaphragm to model for more coplicated analysis and this problem have been desturbing me!
please check this problem.
file is available in this address:

http://www.4shared.com/file/q_8ffyk9/IDA28b.html

Dear iranstruct,

Apologies for the delay with which we are responding.

You are right, the eigenvalue solver seems to not be handling the constraints in adequate manner; we are currently implementing a new eigensolver which will hopefully not feature the same problems.

We would note in any case that problems with a 2D model may not necessarily propagate into the 3D more complex one one, hence it may be worth to try analysing the latter as well, perhaps starting with smaller 1-2 storeys models.

Seismosoft Support