During the last 10 years, earthquake-resistant engineering has seen great progress. Concepts such as plasticity, energy absorption, non-elastic behaviour, seismic isolation have nowadays become familiar to a wider engineering audience, and are used in a large number of projects for the  design of existing structures’ strengthening and the improvement of structural behaviour during earthquake. The publication of issues 273, 274, 356 of the American association’s FEMA journal greatly contributed towards this, as well as the ATC’s issue 40. These include instructions regarding the acceptable range of plastic deformation for every kind of structural element, which can be utilized to evaluate structural behaviour. The calculation of non-elastic deformations can be achieved by approximating them through the push over method, i.e. by the application of a static horizontal load, gradually increasing up to the highest possible displacement, that can appear within this particular system, for a given earthquake spectrum. This method is also mentioned in the recent ‘recommendations for pre-seismic and post-seismic building strengthening’, but it is not clarified how to apply it in practical problems.