Bugs in SAP2000 v14.2

[benny]

Bugs in SAP2000 v14.2

For FloorLL of 2.4 kPa on square floor slab panel, the maximum load delivered to beams is w(span)/2 = 2.4(6)/2 = 7.2 kN/m. Which means the area load distribution to frame elements are correct.


But in the member force diagrams for frames, the maximum load delivered is 7.2(2) = 14.4 kN/m.

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In ETABS v9.7 member force diagrams for frames, the maximum load delivered is 6.911 kN/m. There is a difference of 0.289 kN/m with respect to 7.2 kN/m, but this will not affect the results.

Therefore, by comparing the results of SAP2000 v14.2 to the results of ETABS v9.7, the bending moment, shear, and deflection has been doubled in SAP2000.

SAP2000 and ETABS model files:

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[struceng]

Dear Benny,

I checked your Sap2000 model and found that you doubled the FloorLL on all beams. You first gave distributed frame loads to the frames and in addition the same load is coming from area elements with "Uniform area load". This is why you are reading doubled results. So there seems no bug on this subject.

Etabs is reducing the load because it considers the intersection between beam-floor and removes this intersection area from floor. This is why the loads are a little bit reduced in Etabs.

But I also want to comment on your loadings. You made a PDELTA (nonlinear case) analysis and then started all other load cases from the stiffness of this PDELTA analysis results. But:

1) If you will combine these load cases, this will result in extra deflection readings from normal because Sap2000 will add the deflection from PDELTA (caused by DL) for all load cases in that combination.

2) There is no need to do that for vertical load cases like FloorLL since no effect (neglectible) on moment results (but effects deflections of course). You should do that for vertical loads like EQX and EQY loads (or wind) that will not be used in the same combination. But in some seismic codes they are combined together so you should be careful again.

I hope this helps.

Regards.

[ascetic19]

Dear Benny,

I examined your models. As i saw, in sap doubled loads on frames that one is from slab and the other one from self. in etabs there is only load from slabs.

i think, you countered doubled forces in sap because of double loading.

regards,

ascetic

[benny]

Dear Ascetic,

I examined, and you are correct. The SAP2000 model was an import from ETABS .s2k files. After importing there was no LL in the Load Pattern of SAP2000. So I applied again the floor DL and floor LL thinking it was not carried over.

My apology if ever it creates confusion to some members of the forum.

[ascetic19]

Dear Benny,

it is very important to check our softs. Actually, after lots of comments about patched exe. 's size of those.

best regards,

ascetic