Steel tube filled with concrete
 

Hello all,

I am trying to model axially compresed composite column made of steel tube filled with concrete, but since I am novice in Ansys, there are many problems (and so little time to solve them).

So far i have manage to create geometry using next commands:
/prep7
rectng,0,75,0,300 !! for concrete core (150mm diameter, 300mm high)
rectng,75,80,0,300 !! for steel tube (160mm diameter, 5mm thick wall, 300mm high)

Next:
k,1001,0,0,0
k,1002,0,300,0
Moddeling/Operate/extrude/areas/about axis !! with this I get cilinder and tube

Define element type
ET,1,solid 65 !!for concrete
ET,2,shel181 !! for steel

And that is about it.
1.How to assign ET to cilinder to be solid65 and tube to be shell181?
2. What MP to assign to these element, since I am planning to do nonlinear analysis?
3.I have seen in one example TB command with a lot of numbers following, but cannot find what they mean.
4. how to add incrementally load to the upper surface?

Pls. help

Best regards