Expeditious seismic assessment of existing moment resisting frame reinforced concrete buildings. Proposal of a calculation method

Recent earthquakes that have struck Italian territory have emphasized the necessity to assess the seismic safety of the existing built heritage, comprising, for a substantial part, Reinforced Concrete (RC) buildings designed between the 50 s and 80 s. Those buildings were designed in accordance with regulations that, although showing a growing seismic awareness, were certainly inadequate to design buildings capable to withstand the design earthquakes prescribed by the more recent Italian Technical Standards for Constructions (NTC 2008). At the same time, the recent proposal made by the technical community to equip each existing building with a seismic suitability certificate encourages the development of a rapid method for seismic safety assessment. This paper presents a method to carry out a simplified and fast non-linear static seismic assessment of an existing RC building. This method is based on: (a) the selection of the RC elements that, based on engineering judgment, are expected to be the most vulnerable ones, and on (b) the subsequent evaluation of the structure displacement capacity corresponding to their failure. Simple and conservative plane structural models are proposed to carry out such evaluations. With the aim to appraise its potentialities, the proposed procedure is also applied to some RC buildings whose experimental and numerical results were published in the latest scientific literature. Strengths, weaknesses and possible further developments are highlighted.