Convention of bending moment signs

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GianmarcoManzo
Posts: 19
Joined: Tue Sep 17, 2019 2:38 pm

Convention of bending moment signs

Post by GianmarcoManzo » Sun Nov 24, 2019 8:39 am

Hi,
I have modelled the same structure with STKO and with Seismostruct and I have seen that the sign of the bending moment is discordant. The global axes is the same and also the local axes of the elements. So, the question is: What is the Convention of bending moment signs in STKO? And why is It unlike the one obtained with seismostruct ?? Thanks.

MassimoPetracca
Posts: 37
Joined: Wed Jul 24, 2019 11:10 am

Re: Convention of bending moment signs

Post by MassimoPetracca » Thu Nov 28, 2019 5:32 pm

Hi Gianmarco,

Can you post a picture comparing the two apparently discording results? It should be the same but let's check

GianmarcoManzo
Posts: 19
Joined: Tue Sep 17, 2019 2:38 pm

Re: Convention of bending moment signs

Post by GianmarcoManzo » Sun Dec 01, 2019 6:21 pm

Place some photos showing both the orientation of the local axis of the element and the global axis (in both software). The diagram of the moment in STKO is visible with the colors while from seismo there is the diagram in 3D and I also reported the 2D one with the values. The values ​​are perfectly identical but with opposite signs everywhere (I report only the photo of a piece of the structure). What might it depend on? Different sign convention? What is that of STKO? thanks
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MassimoPetracca
Posts: 37
Joined: Wed Jul 24, 2019 11:10 am

Re: Convention of bending moment signs

Post by MassimoPetracca » Mon Dec 02, 2019 9:57 am

Yes, Sign convention in OpenSEES appears to be the opposite of that of SeismoStruct or MidasGEN

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