SHELL181 Composite beam

[sai.pai]

Dear ANSYS users,

I am having trouble with a composite beam model, which is relatively simple. I have a steel I-beam that supports a concrete slab. I have modeled the beam and slab using SHELL181 elements. The I-beam therefore consists of 3 areas forming the I and the slab on top. I have combined the nodes of all elements forming this composite structure using CPINTF command. I fixed one edge of this assembly and added a point load at the other end.

I was able to solve this assembly and obtain the tip displacement. However, what I observed in my sensitivity analysis was that the E (modulus of elasticity) of concrete did not affect the tip displacement. This is confusing me as the E of concrete and steel affects displacement of the assembly.

I modeled the same assembly using SOLID185 elements and was able to notice the effect of varying the E of concrete slab.

Would the members here be able to provide me into any insight why I am observing this behavior?

I have already considered modeling the connection between the I-beam and slab using rigid spring elements and merging overlapping nodes.
_________________
Sai Ganesh S Pai
Doctoral Assistant
Swiss Federal Institute of Technology
CH-1015 Lausanne
Email: sai.pai@epfl.ch