problem with analysis of 3D model with RigidDiaphragm

[cvatansever]

Dear All,

While the static analysis of a 3D steel building, without rigid diaphragms, under vertical loads is successfully completed, when we added the rigid diaphragms using the master nodes in the mid-spans of the building into the model, the following error occurs.

analyze failed, returned: -3 error flag

Do you have an idea on what the reason of the error can be ?

Cuneyt,

[fmk]

no other messages?

[rwm]

I had this problem and it was caused by my master nodes being insufficiently constrained.

If the Z-axis is the vertical, so your diaphragm is in the X-Y plane ($perpDirn = 3), then RigidDiaphragm will constrain the master node displacements in the X- and Y-directions, and rotations about the Z-axis. It is therefore necessary to restrain the master nodes against displacements in the Z-direction, and rotations about the X- and Y-axes, which can be done using:

fix $masterNodeID 0 0 1 1 1 0