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RE: STAAD or RISA?

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Scott

First of all, I am amazed you are commenting on software without having them in front of you. Your memory must be reaaaaaly good, my friend.

There is a very simple way for you verify the accuracy of the master slave aspect in STAAD. Open the example problem # 26 that comes with their program. It is a multi-storey building example with 2 load cases. Load case 2 consists of loads which cause the structure to undergo torsional deformation when seen from above. Run the analysis and view the displaced shape. You will observe that the deflected shape does indeed correctly reflect the behavior that a structure of this type will undergo when subject to such loading. If you wish to explore the matter further, you can work with example number 9 also. If you create a model similar to that, where the plates are substituted with a master-slave (DIAPHRAGM in ZX plane) command, and an eccentric load is applied at one of the top corners, you will see that the answers are remarkably close to what you will get if you apply such a lop-sided load on the example 9 model. I'll be happy to send it to you if you wish.

I-cheeeee-ro rules! (I love my M's)

Dave

PRCE

PS

For Gerard, please don't generalize on what "American" engineers think or don't think. I worked for the USACE (who by the way standardize on STAAD.Pro) and I know comments like that gets everybody into trouble.

Dave,

I am curious...what do you use the master/slave funciton for?  Is it
per chance to "model" the diaphram action in a 3-D model?  If so, you may
want to be a little careful with STAAD.  While they may have updated the
function, I do know that in older versions (not too old) the master/slave
could not be used to get a true rigid diaphram effect.  The master/slave
function makes ALL the slave joints translate the same as the master joint
in plane of interest.  The result is that using the master/slave method
will not allow for torsional rotaion of floor plane due to relative
stiffness of lateral frames/walls.  In otherwords, your model (if using
the master/slave function to model the diaphram) will be ignoring the
torsional effects of the lateral loads.

RISA does have a diaphram option that at least appeared (it has been a
while and I don't have RISA to use at this time) to include the torsional
effects.

HTH,

Scott
Ypsilanti, MI




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