How can the neutral axis of a concrete column under biaxial bending be determined. I mean if the load P is given along with the eccentricities ex and ey, how could the N.A. location and orientation be computed? Thank you.
Since concrete and steel are both non-linear materials the only accurate way to do it is numerically using trial and error.
Well I'm willing to make a program using Mathematica or a spreadsheet in excel in order to create the interaction curve of a column,so trial and error is no problem. Can you explain how shall I do it? Should I assume an initial N.A and then do the computations, and after that check if the computation check with the N.A assumed position?
That's pretty much it. Generally you have the vertical value of c and the rotation angle θ to locate it. Now if you are doing an interaction curve that is a little different because now you are finding capacities which I think will turn out to be a little easier to do. A good reference is Collins & Mitchell's "Prestressed Concrete Structures".