Abstract
Existing reinforced concrete (RC) buildings in Europe have generally been designed without proper consideration of seismic actions and capacity design principles, and thus they tend to be vulnerable to earthquakes. Moreover, since a significant proportion of the aforementioned buildings were developed during the 1950s and 1960s, they are currently close to the end of their service life. Therefore, seismic assessment of existing RC building is a major issue in structural engineering and construction management, and the related seismic analyses should take into account the effect of material ageing and degradation. This paper proposes a practice-oriented procedure for quantifying seismic reliability, taking into account the main effects of carbonation-induced degradation phenomena. It summarizes the main aspects of the most up-to-date models for the seismic degradation of concrete and RC members and shows how nonlinear static (pushover) analyses can be utilized (in lieu of the most time-consuming non-linear time history analyses) in quantifying seismic reliability with respect to the performance levels of relevance in seismic engineering. A relevant case study is finally considered with the aim to showing how some parameters, such as exposure class and cover thickness, affect the resulting seismic reliability of existing RC buildings.
Highlights
In Europe, the vast majority of reinforced concrete (RC) structures were built in areas classified as non-seismic at the time of construction and before seismic codes came into force [1]
The present paper presents a preliminary approach for practice-oriented seismic reliability analysis of RC structures affected by material degradation
Some preliminary results are reported with the twofold aim of showing the potential of the proposed procedure and figuring out the influence of some relevant parameters on the resulting reliability performance of a simple, yet widely representative, structure considered as a case study
Summary
In Europe, the vast majority of reinforced concrete (RC) structures were built in areas classified as non-seismic at the time of construction and before seismic codes came into force [1]. The aforementioned procedures provide structural engineers with somewhat simplified methodologies for the assessment of seismic risk, namely the mean annual probability PLS of a structure to achieve a given limit state (LS) as exposed to a seismic hazard described by hazard curves In addition to their simple conceptual framework, they require carrying out a huge number of non-linear time history analyses that are increasingly time-consuming as the level of detail of the numerical models increases, as is usually required to achieve a sufficient accuracy in simulating the structural response of the existing structures. The present paper proposes a general practice-oriented framework and some preliminary results about the evaluation of seismic reliability of RC structures affected by carbonation-induced degradation phenomena To this end, a simple yet mechanically consistent implementation of the effects of material degradation in a structural analysis model is described. The outcomes of some parametric analyses are presented in order to quantify the evolution of PLS (seismic risk) resulting from alternative scenarios involving different environmental exposures, material properties and structural detailing in terms of concrete cover
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