"bending stress-strain curve" or "compression stress-strain curve"?

hi, 

for the thermal analysis i used solid 70 for concrete.while switching to structural analysis switched the element type.it switched automatically to solid 45. but for concrete analysis i need solid 65 element. in the structural environment can i remesh it using solid 65? how can we do the keyopt settings for solid 70?

i modelled concrete beam with solid 65 for concrete and link 8 for steel main reinforcement and stirrups.

 how can i ensure the connection between steel and concrete?

if anybody knows the answer pls reply

Hello Mahmood!

Experiments give force-displacement curves, not stress-strain curves, because these are the things you can measure. In a tension/compression test you assume(!) that the force is constant within the cross section of the specimen (wich gives you a constant stress), and the elongation is proportional with the length (which gives you a constant strain). These assumptions deliver us the general formulas stress=F/A, strain=dL/L. From that point of wiev you can use the stress-strain curve from the compression test, or create your own from the force-displacement curves (up to the necking point where constant stress and strain no longer hold).

Bending is a different story, since in bending you have NO constant stress. In bending you have tension on one side of the specimen, and compression on the other, and the magnitude of the stress is proportional with the distance from the neutral axis. In a three-point experiment (where a beam is fixed on the ends and bent in the middle) you can give the force as a function of the displacement in the middle. But because of the lack of constant stress state along the cross section, you cannot convert it to a stress-strain curve as you did in the compression!

What can you do? You use the stress-strain curves gained from the compression experiment and check the bending experiment with it. If the force-displacement curve you get fits with the given ones, you got your job done. If they do not, than you can start thinking why. One thing may be that the material has different stress-strain curves in tensoin and compression (in fact many material do so).If so, than you have to search for data on the internet, or start optimizing your own until your bending values fit.

I hope I could give some useful advice.

Regards, Andras