composite stel concrete shear wall

Hi everyone,

I have to model a composite steel-reinforced concrete shear wall with steell encased profiles . I searched in the literature and I found that for concrete is used SOLID65 element, and for reinforcement and steel encased profile is used LINK8 -3D spar element. I defined this 2 elements and two materials for them, BISO and CREEP(implicit creep).

1)Where from can I get the 4 constants  to define creep? I found them in the manual in one exemple but I don't know what do they mean!

2) The encased steel profile is a rectangular holow section. I defined an element with some atributes(section, material, element type)  but after defining it from "preprocessor/modeling/create/element/element atributes/thru nodes" i see just a line whit no cross section atached. Why is  happening these?

3) Has this program an UNDO comand because i can't found it?

Thank's for your time!