shell forces 1

[idrogio]

Hi, when I open the "element force/stress contour for shell" dialog, I find the option to choose M1 M2... but I don't know what N1 N2 and N12 are. I've looked in the manual but I've found nothing.

thanks

 

[danijelSA]

Internal force in sap2000 are indentified with:

Normal Forces: prefix F

Moments: prefix M

Shear Forces: prefix V

In sap2000 force we can show using local or
global coordinate system. All calculation are
based on global coordinate system, but we can
see force and in some diferent coordinate system.
In most situation we do not need to define new
systems or to changing default local.

Sufixs are using to define direction of internal
forces.

Local System: This system are using if we want to
see particulary internal force (like mx, my, mxy).

Global System: In this system we present only main
internal force which sa2000 calculated using below
equation:
Mman,min=((mx+my)/2)+/- sgrt(((mx-my)/2)^2+mxy^2)

For designing always are mandatory main force, but
we can assume that on critical position particular
and main forces are same (mxy->0).

 

[idrogio]

Yes, and what does N stand for?
I don't understand it
thanks

 

[dawn836]

N stand for normal force in shell section
what Mxy mean?
and what N12 mean?

 

[danijelSA]

One of autors software sap2000 is said:
Do not use finite elements software if you
don't truly understand all aproximation and
method which software use for calculations.

First what you have to know before using sap2000
is basics theory of structures.

If you don't (idrogio) know what is normal force you
must stay away from sap2000...

M12 = Mxy is torsional moment in shell.
Force N12 is force per unit area which lie in plane
ortogonal to plane N1 and N2.
From equilibrium -> N12 = N21

Danijel

 

[idrogio]

Listen... Try to be more polite.
And I asked for "N forces" and Daniel said that
"Normal Forces: prefix F"
then dawn said
"N stand for normal force in shell section"
That was not very clear to me....
I know basic thery of stryctures, but in Italy we use quite a different simbology.
So sorry if a made a question that you think is dumb...
the next time please be more polite.

bye

 

[Guest262653]

Actually I had the same problem... And please don't tell me to check my "Theory of structures"...
So, Fii stands for membrane forces
Mii stands for the bending field
And what does Nii stands for? I Wonder if those "specialists" have found a new stress...