Seismic vulnerability assessment of RC buildings at compartment scale: the use of CARTIS form

Large-scale seismic vulnerability assessment methods allow to classify the vulnerability of groups of buildings according to recurring parameters. The parameters necessary for the application of these methods may come from the adoption of survey forms. The 1st level CARTIS survey form collects the parameters of an area (town compartment) characterized by homogeneity among building types. The variation of the parameters within the same compartment may lead to the definition of several typological-structural groups of buildings, which can be characterized by different vulnerability. Therefore, the assessment of the seismic vulnerability of a compartment requires knowing the distribution of different typologies and their relative structural performance. In this work the vulnerability is evaluated at town compartment level starting from the vulnerability of the RC building typologies, by applying the RE.SIS.TO® method to the data collected from the 1st level CARTIS forms. In particular, a tree chart representation, characterized by variable number of branches depending on the different number of possible choices allowed by CARTIS form, is proposed for data organization of the typological-structural groups of buildings

Seismic risk assessment of a new RC-framed skin technology for integrated retrofitting interventions on existing buildings

A RC-framed-skin technology for the integrated seismic and thermal retrofitting interventions on existing buildings, recently proposed by some of the authors, is thoroughly investigated. By means of numerical analyses, its effectiveness and suitability within the framework of seismic risk class assessment is proved. The system is composed of a RC-framed structure with an external reinforced plaster layer that does not offer a structural contribution to the capacity of the system in ultimate conditions, but which can be effective by increasing the lateral stiffness in serviceability conditions. The system is realized from the outside of the existing building so guaranteeing limited invasiveness of the intervention and preventing the interruption of the building use by their occupants. An existing RC building, representative of a typical example of the Italian building stock, is analyzed as a case study, and its seismic risk class upgrade, obtained by the proposed strengthening intervention, is assessed by non-linear static analysis. The numerical models are developed within the OpenSees framework. The Expected Annual Loss (EAL) parameter, together with the Life Safety Index (LS-I), are chosen as synthetic measures that include both aspects related to Ultimate Limit state (ULS) and Serviceability Limit State (SLS) conditions. The risk class accounting for or disregarding the contribution of the external reinforced plaster are finally compared

A methodology for the evaluation of morphology-based constitutive laws of corroded steel rebars

The assessment of degraded reinforced concrete (RC) existing structures is nowadays a topical problem since several ones have an age close to or higher than their design life. The degradation state of the structure needs to be properly assessed and included in the adopted numerical or analytical models. In this framework, rebars corrosion phenomena can modify the structural behavior of RC members, especially when the corrosive attack is localized in specific areas. As an example, in presence of localized concentrations of chlorides, pitting corrosion of the steel bars occurs, with a localized reduction of the bar section through pits. In this work, the results of a preliminary experimental survey performed on artificially corroded steel rebars are shown, to define an integrated methodology for the definition of material constitutive laws, accounting for morphological aspects of the corrosion phenomenon. A set of steel rebars, embedded in concrete prisms, have been artificially corroded with an accelerated process through electrolytic cells, to obtain local marked pits. The steel rebars have been extracted, cleaned, weighed and subjected to 3D scanning using two different techniques (one based on laser scanning and the other based on structured-light scanning) to evaluate the effective corrosion amount and morphology. Finally, tensile tests were carried out to evaluate the stress-strain curves and the values of yielding, ultimate strengths and elongation to fracture. The presented data and methodology can represent a useful reference for the definition of phenomenological constitutive laws for steel rebars affected by pitting corrosion