Error at Joint

Question

I am working with a fairly large model consisting of a steel frame building with the floor modeled using plates connected to the beams. I keep getting the following error: 
 
 ***ERROR - AT JOINT 2234 DIRECTION = MZ 
 PROBABLE CAUSE NEGATIVE DIAGONAL =>LDLT MTX 
 K-MATRIX DIAG= 1.1249905E+06 L-MATRIX DIAG= -1.1469693E-02 EQN NO 2895 
 
 Does anyone have any advice on how to fix this or what the cause of the error is? 
 
 Thanks.

Sye · Accepted Answer

MX releases were applied in beams. Considering the fact that members are not free to rotate about their own axis, these should be taken out. 
 
You applied MY, MZ release in beam 797 which is part of a continuous beam and hence the release is not appropriate and should be removed. 
 
You applied a number of plate releases out of which the FZ degree of freedom, which is for out of plane shear, is also released. This does not seem right as that would prevent plates from putting any vertical load ( including its selfweight) on the supporting beams. I think these should be taken out. 
 
With the above changes, the analysis is being carried out. Since you posted the file using secure upload, I am not posting the modified file in the forum. Please let me know if it is OK to do that. If not and you need the modified file, please send me your email address and I will email it to you.