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A multi-purpose and multi-scale tool for the seismic vulnerability and risk classification of critical buildings, such as schools, is proposed for pre- and post-event decision-making to mitigate the risk and reduce losses. The herein proposed "RiskSchools" system, is capable of performing the seismic risk assessment and grading of school buildings at various scales (district, municipality, region etc.), using (a) a pre-seismic rapid visual screening and grading of the school buildings in different vulnerability-risk classes and (b) a seismic risk assessment of the school buildings population, applying probabilistic or scenario-based methods for the seismic hazard and analytical methods for the vulnerability and risk assessment, also leading to a grading of the buildings' risk. The results of the two approaches are compared and combined through a flexible and adaptable expert elicitation scheme to provide a final classification of the seismic risk of the school buildings in the scale of interest and a prioritization scheme with respect to the need for seismic upgrade and retrofitting. The RiskSchools system consists of a powerful, state-of-the-art, user-friendly, and easy-to-use smartphone application for the compilation of the inventory and the rapid visual screening, and a project-dedicated multi-purpose webGIS platform for the seismic vulnerability and risk classification of school buildings at any scale. Although it is initially developed and applied to the school building stock of the Region of Central Macedonia in Greece, it has been specifically designed to be easily applied to other regions of Greece and worldwide and adapted to other critical buildings, like health care and hospital buildings. The ultimate scope of the RiskSchools System is to allow for the optimal design of decision-making procedures in support of disaster management to enhance critical buildings resilience. [ABSTRACT FROM AUTHOR]

Evidence of past earthquakes highlighted the seismic vulnerability to buildings due to soil liquefaction and lateral spreading phenomena. Damage to buildings on a liquefiable site, especially on a gently sloping site, can be severe. The liquefied soil can undergo permanent lateral ground displacements as large as several meters in some cases, which can be severely disastrous to buildings. Recent physical tests and effective stress analyses of nonlinear dynamic soil-structure interaction (SSI) proved that simplified empirical processes are often improper for evaluating liquefaction-induced building settlements. A better understanding of the SSI effects is also essential in cases where the underlying soil is susceptible to liquefaction. In this respect, the interaction of the earthquake excitation and ground failure (i.e. soil liquefaction and lateral spreading) for buildings considering SSI is investigated herein. Typical low-code reinforced concrete (RC) frame buildings of different heights with shallow spread footings on liquefiable level-ground or sloping soils subjected to ground shaking are considered. The direct SSI approach is implemented. Predictive relationships are established between the maximum normalized differential displacements (horizontal or settlement) and the permanent ground displacement (PGD) vector at the level of foundation for low-code RC frame buildings with shallow spread footings on soils with high liquefaction potential subjected to ground shaking. Finally, vulnerability is expressed in terms of fragility and vulnerability curves as well as in terms of fragility surfaces as a function of two intensity measures. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate whether existing generic fragility curves for various residential building typologies can be safely applied for the vulnerability assessment of school buildings. We select three representative typologies of actual reinforced concrete (RC) school buildings in Thessaloniki, Greece and we conduct a detailed fragility analysis combining field inspection and structural monitoring data to advanced numerical modeling. Building-specific fragility and vulnerability curves are derived for the three school buildings based on 3D incremental dynamic analysis (IDA) of the calibrated numerical models. The comparisons of the developed curves with generic ones showed their significant differences. [ABSTRACT FROM AUTHOR]

Recent strong seismic events have highlighted the high vulnerability of port facilities resulting in significant physical damages and important socio-economic losses. The most widespread source of seismic damage to port structures is often not related to the ground shaking itself but to the induced phenomena principally associated to the liquefaction of loose, saturated soils that often prevails at coastal areas. In this context, this study aims at the investigation of the influence of soil liquefaction on the seismic performance and vulnerability of typical port gravity quay walls. Different gravity quay wall configurations are examined with varying base width/height ratios. Two-dimensional incremental dynamic analysis is conducted for the soil-quay wall system, under effective stresses using OpenSees software, considering a representative set of fifteen real ground motion records as input ground motion at the bedrock. Two numerical approaches are applied to investigate the effect of liquefaction on its seismic performance and vulnerability assessment: the first one without considering liquefaction, while the second considers the effects of liquefaction. The damage measure is defined in terms of the normalized seaward displacement. Fragility and vulnerability curves are finally derived in terms of different intensity measures and compared with available literature curves. Results show the important role of liquefaction in increasing the seismic vulnerability of the typical port quay wall. [ABSTRACT FROM AUTHOR]

Liquefaction constitutes the most common source of seismic damage to buildings resting on saturated soils. Soil-structure interaction (SSI) may also significantly affect the seismic response of structures, modifying their dynamic characteristics and the seismic response at the foundation level. Although progress has been made on the investigation of the influence of soil liquefaction and SSI on the structural response, studies combining both phenomena are very limited. To bridge this gap, we investigate the integrated influence of both liquefaction and SSI on the seismic response and vulnerability of low-code reinforced concrete (RC) moment resisting frame buildings. A two-storey non-ductile RC frame building is adopted as reference. The following numerical models are developed: (1) a fixed-base structure subjected to free-field (FF) motion neglecting liquefaction (and SSI); (2) a fixed-base structure subjected to FF motion allowing liquefaction; (3) a flexible-base structure (i.e. including SSI) resting on soil subjected to outcrop bedrock motion neglecting liquefaction; (4) a flexible-base structure resting on soil subjected to outcrop bedrock motion allowing liquefaction. Conducting nonlinear incremental dynamic analysis for the above-described configurations, we derive seismic fragility curves considering (or not) SSI and/or liquefaction effects for different damage limit states through statistical correlation of the calculated engineering demand parameter with appropriate intensity measures. We also generate vulnerability curves to quantify the expected structural losses. Results show the substantive role of liquefaction and SSI in altering the seismic fragility and vulnerability of non-ductile low-rise RC frame buildings. [ABSTRACT FROM AUTHOR]

Harbours are crucial assets for the sustainment and development of human activities. The recent devastating tsunami events as well as the increasing number of people, structures and economic activities being exposed to tsunami hazards revealed the need for the estimation of the effects of tsunami wave on seaport structures. However, only a limited number of tools to estimate the potential impacts of tsunami are available until now. This study aims at developing analytical tsunami fragility functions for some representative typologies of seaport structures in Greece. In particular, low-code moment resisting frame (MRF) and dual reinforced concrete (RC) buildings of various heights, and a typical warehouse are considered in the analysis. A numerical investigation is performed considering different combinations of tsunami loads based on FEMA P646 (2008) [1] recommendations for gradually increasing tsunami inundation depths and for the various structure typologies. To minimize the uncertainties related to the definition of damage limit states, tsunami nonlinear static analyses are performed and appropriate tsunami capacity curves are derived for the considered structures. Structural limit states are defined on tsunami capacity curves in terms of threshold values of material strain. For the complete damage state, shear failure is also considered, since the collapse of structures may be caused by the occurrence of either a flexural or shear failure in structural components. Fragility curves are numerically calculated for the different damage states using nonlinear regression analysis. They could be used within a probabilistic risk assessment framework to assess the vulnerability of low-code RC buildings and typical warehouses exposed to tsunami hazard along European-Mediterranean and other regions of similar facilities worldwide. [ABSTRACT FROM AUTHOR]

While liquefaction has been widely recognized as being one of the principal earthquake hazards resulting to significant economic and societal losses, research in the vulnerability assessment and quantitative evaluation of the expected physical damages to building structures is rather limited. In this respect, this study aims at the vulnerability assessment of typical low-code reinforced concrete (RC) frame buildings of various heights with shallow flexible foundations subjected to differential permanent displacements due to liquefaction. Nonlinear static analyses are carried out for each considered structural typology assuming different gradually increasing differential displacement patterns applied as quasi-static loads directly at its supports (footings). Different damage mechanisms are examined including a flexural damage of the building members and a shear failure of the columns. The proposed methodology results to the development of lognormally distributed fragility curves for different structural damage states as a function of the liquefaction induced differential displacements. It is shown that the height of the structure as well as the existence or not of a horizontal component of the differential displacements represent key factors affecting the vulnerability assessment. Vulnerability curves are also constructed to assess the expected direct losses in normalised cost terms. The whole approach is illustrated through a specific example. [ABSTRACT FROM AUTHOR]

• Framework to assess the fragility of RC buildings to ground shaking and liquefaction. • Nonlinear incremental dynamic analysis under effective stresses of the soil. • Consideration of soil-structure interaction and soil liquefaction potential. • Conventional fragility curves for buildings due to ground shaking and liquefaction. • Fragility surfaces for buildings due to combined ground shaking and liquefaction. The recent strong seismic events have demonstrated that most damage to coastal buildings is often associated with liquefaction effects. The occurrence of earthquake-induced ground shaking and liquefaction may be dramatic for buildings and poses a considerable threat to people. However, the influence of the simultaneous action of ground shaking and soil liquefaction considering soil-structure interaction (SSI) effects on the structural behaviour of buildings has not been adequately studied yet. In this respect, we propose a methodology for the fragility assessment of non-ductile reinforced concrete (RC) moment-resisting frame buildings exposed to combined ground shaking and soil liquefaction, based on a fully coupled numerical approach considering SSI. A fully coupled (u-P) formulation is employed, which can capture in cohesionless soils the permanent shear-strain accumulation during dilation and soil liquefaction. Two-dimensional incremental dynamic analysis of the nonlinear SSI systems is conducted for the estimation of the building response. The proposed methodology yields either conventional fragility curves, or coupled fragility surfaces, which are a function of more than one intensity measures and provide useful and important information for an integrated fragility assessment. It is shown that the height of the building resting on liquefiable soil may significantly affect its vulnerability to combined ground shaking and soil liquefaction, with the non-ductile low-rise RC frame buildings suffering more structural damages compared to the mid- and high-rise ones. Also, the high-rise buildings, even susceptible to liquefaction, do not sustain severe structural damages but only sink or tilt. The proposed fragility models can be adapted to estimate the risk of typical non-ductile RC frame buildings exposed to ground shaking and soil liquefaction. [ABSTRACT FROM AUTHOR]

Greek classical temples constitute monuments of great historical and architectural value. The majority of them remain nowadays as free-standing multi-drum or monolithic columns or portals. Their present typology, in addition to their slenderness, render their response to seismic ground shaking quite distinct compared to that of modern structures. Rocking and/or sliding of the drums along their interfaces are the main modes of response under seismic loading. In this study, the seismic response of classical multi-drum columns is investigated by means of rigorous numerical analysis. An Ionic multi-drum column that has recently been restored at the Akropolis of Lindos in Rhodes, Greece, is used as a case study. The numerical analyses are performed using the finite element code ABAQUS. Numerical modelling is validated with a series of shaking table tests that were performed on a scaled multi-drum model column. Additional analyses are conducted by bonding perfectly the structural elements of the column, to investigate the seismic response of free-standing monolithic columns and compare with multi-drum columns of the same geometry. Through the presentation of representative results, critical parameters that affect the seismic response of this type of structures, including the amplitude and frequency content of the applied base excitation, the effect of uniaxial or multiaxial excitation and the interface characteristics, are highlighted and discussed. Particular emphasis is given on the stresses developed along the interfaces during shaking. The structural performance and overall stability of both the multi-drum and monolithic columns are investigated in terms of the maximum displacement of the capital against various intensity measures of the base excitation. The study contributes towards the improvement of the knowledge of the seismic performance of free standing rocking systems, such as the classical columns. [ABSTRACT FROM AUTHOR]

The present study focuses on the dynamic system identification of the Suleiman Mosque minaret in the medieval city of Rhodes, Greece. Suleiman Mosque was built in 1522 at the site of the destroyed Christian Church of the Apostles. First, we performed sets of ambient vibration measurements at the minaret of the monument. Based on these data, we calculated the eigenproperties of the minaret. Next, we modeled the monument in three dimensions, using the finite element method. Six numerical models were considered. Model Ι is the simplest one (isolated, fixed base minaret). Model VI is the most complicated one (simulation of the whole mosque also considering soil–structure interaction and foundation flexibility). The calculated predominant periods and mode shapes of Models I–VI are validated against the microtremor field measurements, recorded on the minaret's two floors and ground level. We elaborate on the reliability of finite element models for earthquake response evaluation, considering soil–structure interaction and foundation flexibility on the mode shape eigenfrequencies. Additionally, we discuss the seismic response of the minaret compared to the whole monument. We observed no significant difference in the first two modes of response, implying that the minaret's dynamic behavior is slightly affected by the entire mosque's presence. [ABSTRACT FROM AUTHOR]

Highlights • A multi-level framework for stress testing port infrastructures is presented. • Regulatory requirements do not exist, and risk objectives are based on judgments. • Critical components are identified, and recommendations are provided. • The results depend on the stress test level, analysis approach, and risk metrics. • The systemic risk for the tsunami hazard is very low compared to seismic risk. Abstract An engineering risk-based methodology for stress testing critical infrastructures is introduced and applied to the port of Thessaloniki in Greece exposed to seismic, geotechnical and tsunami hazards. The methodology workflow consists of four phases: Pre-Assessment, Assessment, Decision and Report phase. In the pre-assessment phase, all the necessary information is collected and archived. For the pilot study, the inventory includes the main port components namely buildings, waterfronts, cranes and the electric power system. Generic or site-specific fragility models are used for all exposed elements and considered hazards. Risk metrics and objectives are defined related to the functionality of the system and the structural losses. In the first level of the assessment phase, the performance of each component is evaluated using a risk-based approach. Then, a system level probabilistic risk analysis is conducted separately for earthquake and tsunami hazards. A complementary scenario-based risk analysis is carried out aiming to investigate the impact of site-specific response and extreme seismic events to the performance of the port. In the Decision phase, the results are compared with predefined objectives to decide whether the infrastructure passes, partly passes or fails the test. Guidelines and strategies to improve the performance and resilience of the port are summarized. [ABSTRACT FROM AUTHOR]

The paper presents an alternative site classification scheme and associated intensity dependent spectral amplification factors, aiming to contribute to the ongoing revision of Eurocode 8. The new classification scheme, introducing among the main classification parameters the fundamental period T 0 of the site, is an evolution of the recent work by Pitilakis et al. (2013) [1], while the main features of the amplification factors and the new seismic design actions are summarized in the use of two anchoring spectral values, for short (0.2–0.3 s) and intermediate (1.0 s) periods, instead of only one of the present version of Eurocode 8 (i.e. effective ground acceleration), and the scalar intensity variation of site amplification factors to account for soil nonlinearity. The work is based on a comprehensive analysis of a worldwide database of strong ground motion records from sites which dispose a very well-documented soil profile down to the seismic bedrock (Vs>800 m/s). • New site classification scheme, elastic spectra and amplification factors for EC8. • Main classification parameter is the fundamental period of the site. • Use of two anchoring spectral values for short and intermediate periods. • Scalar intensity variation of site amplification factors for each soil class. [ABSTRACT FROM AUTHOR]