Master - Slave question
Master - Slave question
(OP)
We had another engineer (no longer with us) who modeled a 3 story steel moment frame building using the master slave command. He had it set to MASTER RIGID. When I took over the project after he left, I deleted the master slave command, and instead modeled flat plates to simulate the slab on metal deck floors. When I did this, everything starts failing.
I checked it again using a revised MASTER DIA XZ command, instead of RIGID command. It behaves basically exactly like my model with the plates.
Can someone explain what the RIGID command is doing please, and when you would want to use it?
It seems to be locking every node against any rotation, but allowing translation. Whereas my plates (and the DIA XZ master command) allow rotation at the nodes.
I am somewhat worried about the results, as many beams and columns are now failing, some by as much as 300%. They all worked when the master was set to RIGID.
Any insight is very much appreciated.
I checked it again using a revised MASTER DIA XZ command, instead of RIGID command. It behaves basically exactly like my model with the plates.
Can someone explain what the RIGID command is doing please, and when you would want to use it?
It seems to be locking every node against any rotation, but allowing translation. Whereas my plates (and the DIA XZ master command) allow rotation at the nodes.
I am somewhat worried about the results, as many beams and columns are now failing, some by as much as 300%. They all worked when the master was set to RIGID.
Any insight is very much appreciated.





RE: Master - Slave question
Hope this answers your query.
Bill
RE: Master - Slave question
Floor diaphragms modeled as SLAVE ZX will have embedded plates with zero inplane forces/stresses but will have bending moments and transverse shears. Floor members would have zero axial & My but would have nonzero Vy & Mz. So for those directions code checking has the possibility of failing.
For modal dynamics with a diagonal mass matrix (masses lumped at the nodes); the master node should be at the c.g. of the masses of the associated slave nodes.
RE: Master - Slave question
Anyway, the end result on this project is we are making the contractor weld in cover plates on about 30% of the buildings columns, and a few of the beams! This steel was already fabricated and erection had already just started, when we discovered the problem. So this one word is going to cost us big time.