RC structural systems appeared in practice after 1950, but with relatively weak and non-earthquake resistant structural elements. Modern RC systems started to be built after 1980. With the coming into effect of modern regulations, there arises the need for raising the level of seismic protection of existing RC structures that are not seismically built. The procedure for analysis and design is similar to the procedure for analysis and design of masonry buildings. For the RC elements, there is a more sophisticated method for definition of the capacity of strength, stiffness and deformability as well as definition of characteristic points in the P-δ working diagram.