Probabilistic seismic performance assessment of code-compliant multi-story RC buildings (original) (raw)
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The RINTC research project (RINTC Workgroup, 2018), financed by the Italian Department of Civil Protection, is aimed at evaluating the seismic risk of buildings conforming to the Italian building code. Within the framework of this project, the attention has been recently focused on existing buildings, too. In this study, case-study structures, representative of the existing residential reinforced concrete (RC) building stock in Italy, are analyzed. These structures are three-storey buildings with compact rectangular plan, and they have been defined through a simulated design process, in order to represent two types of buildings, namely designed for gravity loads only during 1970s (gravity load designed, GLD) or for moderate seismic loads during 1990s (seismic load designed, SLD). GLD buildings are assumed to be located in three different sites, namely Milan, Naples and Catania, in increasing order of seismic hazard. SLD buildings are assumed to be located in L'Aquila. The assumed design typologies are consistent with the seismic classification of the sites at the assumed ages of construction. The presence of typical nonstructural masonry infill walls (uniformly distributed in plan as external enclosure walls) is taken into account, assuming three configurations along height, namely "bare" (without infills), uniformly infilled and "pilotis" (without infills at the bottom storey) buildings. Two 554 COMPDYN 2019 7 th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis (eds.
2014
Practical methods for the probability-based seismic assessment of structural performance in terms of fragility curves relies on estimates of demand produced by earthquakes of different intensities. The uncertainties associated with these estimates are highly dependent on the interface variable adopted as the intensity measure (IMs), generating a need for analyzing the suitability of different candidate IMs, particularly in terms of their efficiency. An efficient IM is one that results in a relatively small dispersion of seismic demand measures, or engineering demand parameters (EDPs), conditional to each considered IM. Selecting an efficient IM will result in a narrower confidence interval for the conditional median EDP value for a given IM level or, from a different perspective, in a smaller number of analyses needed to obtain an acceptable confidence interval. To this aim, the simple study presented in this paper deals with the prediction of displacementbased response of a case-study reinforced concrete (RC) frame building, representative of mid-rise RC building classes in the Mediterranean region. The prediction is performed via statistical relationship between multiple (scalar) ground motion IMs and various EDPs, namely peak (over time) inter-storey drift ratio, maximum (over all stories) peak inter-storey drift ratio and roof drift ratio. Only a small set of potential IMs are considered in the preliminary investigation discussed in this study, namely peak ground acceleration, spectral acceleration at the initial fundamental period (for a damping ratio of 5%), and two advanced scalar parameters accounting for spectral shape over a range of periods. The relationship is built on data obtained from analysis of the frames subjected to over nine hundred ground motion records. An innovative capacity spectrum method is employed, which uses inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. This approach has the advantage of simplicity and rapidity over other methods using accelerograms, as nonlinear dynamic analysis.
Seismic performance is obtained for a five-storied reinforced concrete frame building performing non-linear dynamic time history analyses. Performance of the building was obtained as a mean of fragility function of spectral acceleration. Earthquake ground motion records are selected from online source considering local earthquake faults scenario proposed in Comprehensive Disaster Management Program (CDMP) and then scaled to fit with Bangladesh National Building Code (BNBC) 1993 design response spectra. Since the structure is considered as typical reinforced concrete ordinary moment resisting frame located in Bangladesh, mechanical properties and other associated parameters are chosen according to Bangladeshi perspective. Each ground motion spectrum is matched with design code spectrum at fundamental time period of the building. Non-linear static pushover analysis is performed to determine damage states from pushover curve. Four damage states (from slight to collapse) are defined based on simplified assumptions. A set of dynamic time history analyses are carried out in order to obtain probability density function of the displacement demand correspond to different level of ground motions. Cumulative distribution of each associated damage states allows deriving fragility curves. Finally four fragility curves are obtained for four damge grades (slight, moderate, severe and collapse).