MODELLING ISSUES IN STAAD PRO

[aster123]

Daer,

I have modeled on 2 deck base frame (2 layer of beams fixed in W24x55 beam) for fixing the piping components. But some members are failing in deflection due to seismic load @X. is the model is correct. also i modeled 2 layer by connecting plates and removed the plates from code check.

 

[RJ Design]

Not sure which beams were failing but I noticed that the highlighted beams intersect and don't share a common node, the are essential cantilevered beams according to STAAD.

 

[RJ Design]

I believe it is simply due to no lateral support in the X direction. Those Beams are just relying on the torsional resistance of the Beams about the Z axis and getting thrown all around.

 

[aster123]

Dear RJ DesignWorks,

Thanks for your post. I spliced the beams for intersection. For the extended 2 cantilever beams(763 & 774) may be thrown out in x direction but direction. But beam 116 is already restrained with cross bracing and that also failing. Is there any issue in the modelling or the failure is due to the actual condition.

Also, i provided inactive member command. but that members still showing error in the results. Advise, if Ly.LZ, UNT & UNB is re required for this frame.

 

[RJ Design]

I added Beam 1234, from Nodes 34 to 91, to brace the beam in the X direction and it reduced the utilization ratio to 0.259. If you can add kickers to the others it should resolve your issues.

 

[aster123]

Hi,

But it will not look good, if I added bracing at both side. I have already used stiffener plates at the bottom of the that beam. How i reflect the same in staad. I hope stiffener plate can resist some of torsional moment in Y axis.