Seismic vulnerability of buildings

As defined by the Civil Protection Department: Seismic vulnerability is the propensity of a structure to suffer damage of a given level, in the face of a seismic event of a given intensity.
The national legislation on construction safety has recently undergone profound transformations, both as regards the definition of the effects induced by the environment (the "actions") and as regards the levels of protection required, and the related assessment methodologies with respect to these effects.
As far as the "actions" are concerned, the most important innovation concerns the definition of the seismic hazard of the national territory: the Order of the President of the Council of Ministers n°3274 of 2003 established in fact that no part of the territory can no longer be considered free from the possibility of an earthquake occurring during the expected life of a building, at the same time defining the reference intensity for safety checks, set for each individual site, also according to the intended use of the individual building.
The same O.P.C.M. - in paragraph 3 of article 2 - has placed the obligation on the respective owners to proceed with the seismic verification of both buildings of strategic interest and infrastructural works whose functionality during seismic events assumes fundamental importance for civil protection purposes , and of the buildings and infrastructural works that may be relevant in relation to the consequences of a possible collapse.
The Engineering studio has gained many years of experience in performing vulnerability checks on existing buildings - both public and private - having started their execution from the first years of entry into force of the aforementioned O.P.C.M.
The seismic vulnerability of a building is divided into distinct operational phases, divided as follows:
Historical-critical analysis: knowledge of the building history of a building is an indispensable element both for the evaluation of its current safety (both static and seismic), also in consideration of the correct definition of the repair, improvement or seismic adaptation interventions that one wanted to go to implement. The reading and examination of all the existing design documentation will make it possible to highlight the construction period, the construction techniques and rules, the standards used at the time of construction, the original form and subsequent modifications of the building, any deformations and /or the instability with the crack patterns present, the consolidation interventions carried out over time.
Geometric survey: it is aimed at defining both the external geometry and the details of all the construction elements with a structural function: the geometric survey of the structural elements must therefore allow the identification of the structural organization, the identification of the position and dimensions of beams, pillars, stairs and partitions, and the identification of the floors and their typology.
Mechanical characterization of materials: in order to achieve adequate knowledge of the mechanical characteristics of materials and their degradation, we will base ourselves on the available design documentation, and on carrying out a campaign of investigations and dedicated in situ tests, performed on the structures, such as coring , rebound hammer, ultrasound and pull out tests on concrete, taking steel samples and hardness testers on steel, coring, sonic tests and flat jack tests on masonry.
Evaluation of structural safety: it is the final work on which all the data collected in the early stages converge, and which requires an in-depth study of all the data collected, as well as the execution of static and dynamic structural checks by carrying out a structural modeling with "finite elements": it will make it possible to determine the extent of the seismic actions that the structure is able to support with the level of safety required by the current NTC 2018 regulations.