Evolution of Seismic Reliability of Code-Conforming Italian Buildings

• Published in: Journal of earthquake engineering : JEE Vol. 27; no. 7; pp. 1740 - 1768
• Main Authors: Iervolino, Iunio, Baraschino, Roberto, Spillatura, Andrea
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 19.05.2023; Taylor & Francis Ltd
• Subjects: base isolation; Building codes; Building design; Codes; Concrete; Damage prevention; Design; Dynamic analysis; Earthquake damage; Evolution; Failure rates; Fragility; Geological hazards; Industrial buildings; Limit states; masonry; Mathematical models; Nonlinear dynamics; Numerical models; Obsolescence; precast; Reinforced concrete; Reinforcing steels; Reliability; Reliability engineering; Research projects; Seismic activity; Seismic hazard; Seismic isolation; steel; Steel structures; Structural reliability; Structural safety; Three dimensional models
• ISSN: 1363-2469; 1559-808X
• DOI: 10.1080/13632469.2022.2087801

It is well known that the seismic structural reliability is not explicitly controlled in design carried out according to seismic contemporary building codes; that is, those enforcing a simplified version of performance-based design. This is even more true for structures designed with obsolete seismic codes or without any seismic provisions at all, which constitute most of the building stock in countries such as Italy. Between 2019 and 2021, a large research project, RINTC - Rischio Implicito delle Norme Tecniche per le Costruzioni (i.e. implicit risk of existing buildings designed according to the Italian codes), has addressed, in a coherent manner, the inherent seismic structural reliability of existing Italian structures built according to evolving codes, which have now been superseded by multi-limit-state-based provisions. To this aim, five structural typologies of residential and industrial buildings have been considered, that is, reinforced concrete, pre-cast reinforced concrete, base-isolated reinforced concrete, masonry, and steel structures. The building design accounts for the evolution of codes within the last century or more. Structures are supposedly located at five sites in the country, representative of different seismic hazard, both currently and at the time of design. Nonlinear state-of-the-art three-dimensional numerical models for the considered structures have been analyzed via multi-stripe nonlinear dynamic analysis, the results of which, in turn, have been used to evaluate the annual failure rate as a measure of seismic reliability with respect to two performance levels defined within the project and named global collapse and usability-preventing damage. These rates, finally, allowed to appreciate the variation of seismic safety with the evolution of codes and to compare with that implied by current design. The results of the study allowed to conclude that the evolution of seismic codes clearly tends to enhance the seismic reliability with the largest average improvement attributable to the enforcement of the current code.