Simple Beam SAP2000 Results Do Not Match Hand Calcs

Question

Simple Beam SAP2000 Results Do Not Match Hand Calcs

CWEngineer (Civil/Environmental)

(OP)

19 Jan 06 14:27

I am trying to model a simple beam (Lenght = 40 ft) with uniform horizontal load of 8k/ft.  The supports at the end of the beam are pinned connections.

I model this simple beam using Plan Frame in the Analysis options.

The values of the reactions at the supports of my hand caluculationis and SAP 2000 agree.  V = (w)(L/2) = 160 k.

However my moments do not agree.  My SAP 2000 results are showing a moment of 1066 k-ft at the reactions, which should be zero.

I would really appreciate if someone can give me some advice one what might be going wrong here.

THANKS

CWEngineer (Civil/Environmental) · Answer 1 · 2006-01-19 15:58:37

I just noticed that that moment diagram is shifted down, starting at -1066 up to 533. If somehow, this moment diagram gets ship up by 1066 I will match my hand calcs of 1600 which is (1066+533) at the center.

But I am still trying to figuere out why this momement diagram got shifted down.

IJR (Structural) · Answer 2 · 2006-01-31 09:12:30

Are you new to Sap2000 or similar software?

Could be that you simply have included self weight without knowing you have done that.

Best place to start is simply try to rebuild the examples given in the software.

CWEngineer (Civil/Environmental) · Answer 3 · 2006-01-31 11:22:46

Yes, I am new to SAP2000 and was interested in modeling beams with loading and finding the reactions. I found out what i was doing wrong. When place the restraints I used the default that SAP2000 uses, which is a pin for the left reaction and then rollers for the rest.

I was changing all the roller restraints to pin, but leaving the pin (left reaction) how it was since I thought it was a pin. But I did not know that the pin was restraint against rotation. Once I remove the rotation restraints everything worked out.

THANKS

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Simple Beam SAP2000 Results Do Not Match Hand Calcs