You have to know the cross - section of each beam or column in order to calculate "I" moment of inertia , in order to plug it into the formula. Or in the case of the more exotic methods , computers will solve it based on the geometry of the cross section.
You must know how big the members are...
I would take it as a beam that is pinned at both ends. Use Roarks and Young to find a formula for a simple beam supported at both ends. In order to assume it is fixed at both ends, it must be welded to the columns and the columns must be absolutely rigid. Keith
