Evaluation of the Seismic Vulnerability of Existing Pre-Code Rc Core Structural Systems Through Non-Linear Pushover Analyses

Abstract

In the last years, a growing attention has been devoted to the seismic vulnerability assessment of existing Reinforced Concrete (RC) framed buildings designed only for gravitational loads. The seismic behavior of existing framed buildings with an inner RC stairwell core has been investigated much less so far, even if this structural typology has known a certain spread from the Seventies onwards, especially in the Italian largest urban areas. In this work, the seismic behavior a relevant and representative example of existing pre-code RC core medium rise building is evaluated by performing nonlinear pushover analyses. The effect of different modelling assumptions regarding the degree of collaboration between frames and RC walls on the structural response is discussed. The influence of masonry infills on the global structural response is also evaluated by running the analyses both on the bare structure and on a structural model considering a distribution of masonry panels not regular in elevation: the latter distribution corresponds to a typical situation for the considered typology.

Time‐dependent seismic fragility curves for existing RC core‐wall buildings exposed to corrosion

“…This represents a further complication in the assessment criteria for the definition of damage states associated with fragility curves, making the extendibility to core-wall buildings of engineering demand parameters (EDP) commonly adopted for frames not so obvious. [10][11][12][13] Another aspect of concern is that seismic risk assessment of the existing RC building stock is commonly performed with reference to initial values of material properties and strengths, so neglecting the effect of progressive deterioration due to time-dependent phenomena on the structural performance of the building. However, one of the primary sources of structural degradation is represented by reinforcement corrosion caused by exposure to environmental agents, namely carbonation and chloride attacks.…”

“…On the other hand, in most cases, the asymmetric position in the plan of core walls gives rise to a structural irregularity that may lead to torsional motions under seismic actions and dangerous stress concentration in some perimetral frame elements. This represents a further complication in the assessment criteria for the definition of damage states associated with fragility curves, making the extendibility to core‐wall buildings of engineering demand parameters (EDP) commonly adopted for frames not so obvious 10–13 …”

“…The problem is afforded through refined numerical analyses carried out with Abaqus, and focusing the attention on a testbed, representative of the investigated structural typology 18 . The seismic response of this testbed was already analyzed by the same authors in previous works, 11,12 with reference to the uncorroded situation. The proposed procedure and the choice of appropriate demand parameters for the definition of damage states in the case of RC core‐wall buildings are further deepened in this study, where it is also validated through comparisons with other results from the literature referred to both RC framed structures and dual systems.…”