Can anyone derive the formula for calculating the deflection of beams?

Hi, sola ojo!

I'm sorry that no one has yet come along to address your question, so, I thought that I would give it a shot.

Have you tried the following search?

Architecture Deflection of Beams Formula - Google Search

I know that the formula is discussed on some of the sites of the search.

Another site that might be of particular help would be the following one.

http://en.wikipedia.org/wiki/Beam_(structure)

Thanks!