The influence of different concrete classes on the seismic response of a seismically isolated building

In this study, an eight story seismically isolated building representing a mid-rise type building was employed to investigate the effect of usage of different concrete classes (C20, C25, C30, C40, and C50) on the seismic response of a seismically isolated building. The prototype fixed base buildings were converted to seismically isolated buildings by introducing rubber isolators at base level. Analyses were conducted by using two different isolation systems (QW5Tb3 and QW10Tb3).The modelling of conventional fixed base prototype seismically isolated buildings and their modal analyses were conducted on finite-element program SAP2000, whereas, modelling of seismically isolated buildings and nonlinear time-history analyses were conducted using 3D-BASIS program. Floor accelerations, Story shears and inter-story drift ratios were the key structural responses considered. The analysis results showed concrete strength have significant effects on the seismic behaviour of the structures. Seismically isolated buildings with isolation system having 5% characteristic strength, C40 and C50 concrete buildings showed less first floor accelerations as compared to the lower concrete class buildings. In addition, isolated buildings with C40 and C50 concrete showed much more inter-story drift ratio values at each floor level as compared to isolated buildings with C20, C25 and C30 concrete which showed values very close to one another

The European Seismic Risk Model 2020 (ESRM20)

This study describes the development of the various components of the European Seismic Risk Model 2020 (ESRM2020) which will be able to generate, using open-source software developed by the GEM Foundation (the Open Quake-engine), a number of Europe-wide risk metrics including average annualised human and economic losses (AAL), probable maximum losses (PML), and risk maps showing the losses for specific return periods or scenario events. The latest developments towards pan-European exposure models for residential and non-residential buildings and fragility/vulnerability models for damage, economic loss and casualty assessment will be presented. For engineered buildings within the exposure model (reinforced concrete, steel), a simulated design is undertaken using the key aspects of seismic design codes in force across Europe over the past 100 years. The designed MDOF building is then transformed to a SDOF model and nonlinear dynamic analyses are run using a large number of ground motion records, after which cloud analysis is used to develop the fragility functions. For non-engineered buildings (unreinforced masonry, confined masonry, adobe), the SDOF models have been directly developed from simplified formulae, experimental tests and previous studies. Collaboration from local experts at various stages of the model development, initiated through workshops, is an important component of the model, as well as the extensive calibration and validation

FRAGILITY CURVES DEFINITION OF EXISTING REINFORCED CONCRETE BUILDINGS DESIGNED FOR GRAVITY LOADS

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Simplified assessment of seismic performance for RC building classes towards preliminary applications of SISMABONUS incentive at the community scale

This paper applies a simplified approach for the attribution of seismic risk classes SRC to infilled reinforced concrete RC archetype buildings representative of existing gravity load designed GLD building typologies in Italy and investigates on the effect of possible local retrofit interventions to reduce SRC. The evaluation is based on simplified modeling of lateral seismic behavior and on the estimate of the peak ground acceleration PGA corresponding to attainment of building capacity at increasing damage limit states. The SRC is attributed as the minimum between two classes, depending on safety level (percentage of new building standard %NBS) and on expected annual loss EAL. It is shown that, due to brittle failures induced by local infill-frame interaction and consequent low seismic capacity at life safety limit state, the lower (worst) SRC is generally attained for the considered building typologies, independently from the seismic hazard at the site. The application of local retrofit interventions allows ameliorating the SRC and it is found that the most probable SRC for retrofitted building typology depends on the seismic hazard at the sitelower SRC are obtained for zones of higher hazard. Application to RC building typologies in the town of Pompei, near Naples, and cost benefit analysis CBA is performed to investigate on the convenience of alternative retrofit strategies towards risk reduction at the community level

Seismic assessment via EC8 of modern heritage structures:Knowledge of the structure and analysis methodologies

Given the interest earned recently by modern heritage structures, seismic assessment criteria of Eurocode 8, for ordinary reinforced concrete structures, are applied to a modern heritage RC building. The case study, the Tower of the Nations in Naples, allows a discussion on knowledge approaches, analysis methodologies and modeling choices that can be considered. Modal dynamic identification, in situ inspections, and testing provided the necessary knowledge of the structure. Linear and nonlinear models of the structure are built up accounting for tuff infills' stiffness and strength contribution. Numerical modal properties are compared with those obtained through dynamic identification. Lumped plasticity model for reinforced concrete elements and equivalent strut macro models for tuff and concrete infills are employed for the nonlinear model of the structure. Seismic assessment through nonlinear dynamic analyses is carried out for two Limit States. Finally, fragility curves through cloud analysis are obtained for the different limit states considered. </jats:p

Performance evaluation of reinforced concrete buildings with softer ground floors

Određivanje seizmičkog ponašanja je važan zadatak seizmičke analize prema zahtijevanom ponašanju konstrukcije. Podudaranje rezultata dobivenih prema različitim normama od velike je važnosti u postupku seizmičkog ocjenjivanja konstrukcija. U radu je opisana nelinearna analiza ponašanja triju armiranobetonskih zgrada s mekim prizemljem primjenom metode konačnih elemenata prema normama FEMA-356 i FEMA-440, te turskim potresnim normama iz 2007. Za svaku konstrukciju je prikazano stanje oštećenosti, modalna svojstva, međukatni pomaci i globalne razine ponašanja te su dani odgovarajući prijedlozi.Determination of seismic performance is a significant task in the performance-based seismic analysis of structures. The consistency between analysis results obtained according to various codes is highly significant for seismic evaluation of structures. Non-linear performance of three reinforced concrete buildings having a soft storey irregularity is studied based on the finite elements analysis according to FEMA-356, FEMA-440, and Turkish Earthquake Code - 2007. Damage situations, modal properties, storey drift ratios, and global performance levels are comparatively presented for each structure, and appropriate suggestions are given

Analytical versus observational fragilities::the case of Pettino (L’Aquila) damage data database

A damage data database of 131 reinforced concrete (RC) buildings, collected after 2009 L’Aquila (Italy) earthquake, is employed for the evaluation of observational fragility curves. The specific interpretation of damage data allowed carrying out fragility curves for slight, moderate, and heavy damage, (i.e., DS1, DS2, and DS3), defined according to EMS 98 macroseismic scale. Observational fragility curves are then employed for the calibration of FAST analytical methodology. FAST method is a spectral based approach, meant for the estimate of fragility curves of infilled RC buildings up to DS3, evaluated, again, according to EMS98. Kullback–Leibler divergence is employed to check the matching between analytical and observational fragilities. FAST input variables can vary in quite large ranges and the calibration provides a valuable suggestion for the application of the method in other cases in which field damage data are not available. Results showed that optimizing values, for the input variables calibrated, are in good agreement with typical values assumed in literature. Analytical results showed a very satisfactory agreement with observational data for DS2 and DS3, while systematical underestimation was found for the case of DS1

2012 Emilia earthquake, Italy:reinforced concrete buildings response

Data of the Italian National Institute of Statistics are collected aimed at characterizing Reinforced Concrete (RC) building stock of the area struck by the 2012 Emilia earthquake (number of storeys, age of construction, structural typology). Damage observations, collected right after the event in reconnaissance reports, are shown and analyzed emphasizing typical weaknesses of RC buildings in the area. The evolution of seismic classification for Emilia region and RC buildings??? main characteristics represent the input data for the assessment of non-structural damage of infilled RC buildings, through a simplified approach (FAST method), based on EMS-98 damage scale. Peak Ground Acceleration (PGA) capacities for the first three damage states of EMS-98 are compared with registered PGA in the epicentral area. Observed damage and damage states evaluated for the PGA of the event, in the epicentral area, are finally compared. The comparison led to a fair agreement between observed and numerical data