The best source to find information about the capacity design philosophy is the following book: SEISMIC DESIGN OF REINFORCED CONCRETE AND MASONRY BUILDINGS. of T. Paulay and M.J.N Preistley. You should go to chapter 1.4.1, were you will find the main features of this philosophy.
For me, i find this philosophy a much more rational way to design concrete buildings, since you have the control of where the plastic hinges in the structure will form, and the method gives you the guidelines to detail these plastic hinge regions. Also you have control of the failure mode of the whole building.
I hope ive been helpful to you
best regards
Ernesto
