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This study develops a methodology for conducting a quantitative seismic risk assessment for shallow-buried tunnels that are induced by active fault dislocations. A case study for a tunnel crossing a strike-slip fault zone is performed using this method. The fault-tunnel crossing angle, the bedrock overburden thickness, the tunnel burial depth, the lining thickness, and the soil properties parameters are analysed in terms of their effects on the seismic responses, fragility curves, and seismic risks for the tunnels. This methodology could quantify the seismic risk of existing metro tunnels that pass through active fault zones, and could also assist in the establishment of a benchmark tunnel design for designing a tunnel that passes through an active fault zone. [ABSTRACT FROM AUTHOR]

Despite the potential of long duration earthquakes in subduction zones, little attention has been paid on seismic vulnerability assessment of highway bridges that are simultaneously undergoing prolonged corrosion deterioration. Consequently, this study presents a framework for considering the joint impact of ground motion duration and chloride-induced corrosion deterioration on the lifetime seismic vulnerability of aging highway bridge structures. The proposed framework is then applied to a representative case-study multi-span simply supported highway bridge located in subduction earthquake zone within Seattle, U.S.A. A detailed three-dimensional analytical models are first developed that account for the nonlinear behaviour of different bridge components, including experimentally validated column model capable of capturing cyclic degradation of force–deformation response. Suites of spectrally equivalent short and long duration ground motions are adopted followed by an incremental dynamic analysis-based framework for seismic fragility assessment. Deterministic seismic response assessment reveals a higher seismic demand on multiple bridge components under long duration ground motion record as compared to spectrally equivalent short duration record. Lastly, the bridge components and system fragility curves are developed considering modelling and deterioration uncertainties. Results reveal the significant vulnerability of bridge components and system under the joint impact of long duration earthquake shock and corrosion deterioration. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of multi-components strong motion duration on seismic performance of high concrete-faced rockfill dams (CFRDs) by fragility analysis based on the method of incremental dynamic analysis (IDA). The contributions of all compositions of earthquake excitations are considered by the definition of integrated duration based on the concept of significant duration. The nonlinear finite element model of a 2D 200-m-high CFRD is established as a case study and the vertical and horizontal displacements are selected as damage measures. Fragility curves and probabilities of two sets of 23 and 25 spectrally equivalent as-recorded bi-directional long-duration and short-duration motions are determined under different failure grades and intensities. The results show that the duration of vertical component has a certain effect on correction between strong motion duration and deformation of the dam and fragility analysis indicates that the ground motions with long duration can make more risk of failure of high CFRDs than short duration motions. Therefore, the seismic performance of high CFRDs will be reformed by taking the effect of ground motion duration into seismic design and risk assessment consideration. [ABSTRACT FROM AUTHOR]

Bridges subjected to mainshock–aftershock sequences experience significant damage as a result of repeated shaking. Therefore, neglecting the effects of multiple earthquakes may lead to a considerable underestimation of bridges seismic vulnerability. The uncertainties in modeling bridge structural systems as well as the representation of seismic loads significantly affect the bridge vulnerability, especially for horizontally curved bridges, where complex loading conditions exist. In this study, fragility curves for horizontally curved bridges are developed for both mainshock only and mainshock–aftershock sequence cases. The seismic response of a typical four-span horizontally curved reinforcement concrete box-girder bridge is evaluated using the cloud analysis method and the effects of uncertainties on the probability of failure of the bridge components are examined and quantified using the Latin hypercube sampling technique. The results from this investigation indicate that considering the mainshock only could significantly underestimate the damage level even by around 50% and that incorporating uncertainties could change the bridge capacity by more than 45% of its estimated value. [ABSTRACT FROM AUTHOR]

The seismic vulnerability of high-speed railway (HSR) bridges may be overestimated or underestimated when the track structure is oversimplified in a finite element model. Thus, the author established a track-bridge model considering CRTS II slab ballastless track and a trackless-bridge model. The effect of track constraint on the seismic vulnerability of various bridge components and overall system was evaluated by comparing the seismic vulnerability curves of different models under longitudinal earthquakes. The track structure itself was also evaluated, and the multiple components of the track structure were found to be under threat of seismic damage and needed seismic risk assessment. [ABSTRACT FROM AUTHOR]

A method for the estimation of expected annual losses under seismic action, using a component-level approach, is proposed. The method follows the general steps of current Performance-Based Earthquake Engineering approaches and two distinct alternatives are evaluated depending on how the collapse cases are identified. Results are compared with a commonly implemented structure level approach, showing that the latter presents an upper bound in loss estimation. The accuracy of simplified structural analysis alternatives, such as nonlinear static procedures, is also evaluated. The method is found to be suitable for economic loss assessment under seismic hazards, producing performance measures easy to understand for different decision makers. [ABSTRACT FROM AUTHOR]

A major limitation with conventional post-tensioned (PT) shear wall in seismic areas is its low energy dissipation, which is tackled by placing additional mild steel reinforcement at the intersection of the wall and the foundation, called internal energy dissipating reinforcement (EDR). While the behavior of hybrid walls with internal EDR is satisfactory, the replacement of them post-yielding (i.e., after an earthquake) poses a major concern. Therefore, in this study, a new simple arrangement is proposed with external-energy-dissipating-reinforcement (EEDR) to facilitate its easy placement and replacement. This proposed system is expected to enable convenient rehabilitation of the wall after an earthquake and will keep it ready for next seismic shock. A detailed numerical study has been conducted to examine the feasibility of the proposed configuration. The proposed model depicts rocking behaviour with sufficient self-centering and energy dissipation. Having external EDR in the hybrid PT shear wall resulted in an increase in energy dissipation but keeping the strength and stiffness of the wall nearly unaffected. This study has highlighted the effectiveness of proposed external EDR system without significantly compromising the performance of a hybrid PT shear wall during an earthquake. [ABSTRACT FROM AUTHOR]

Seismic responses of high-rise buildings are dominated by the first few vibration modes; therefore, high-floor responses contain long predominant vibration periods. However, it may not be achievable to investigate the seismic performance of nonstructural facilities at high levels of high-rise buildings in the laboratory by using seismic shake tables because of the actuator stroke limitation. In this study, an advanced control strategy that incorporates a transfer system with modern control algorithms is proposed for shake tables to replicate high-floor responses of high-rise buildings subjected to earthquakes. First, design diagrams are proposed to determine the parameters of the transfer system. Then, a set of friction pendulums is adopted as the transfer system for the proof-of-concept stage. A mathematical model for the set of friction pendulums is developed for numerical studies prior to real experimental validation. Three linear controllers and three nonlinear controllers are designed and synthesized to verify the feasibility and applicability of the proposed strategy. Finally, the friction pendulum set is installed on a uniaxial shake table to replicate the roof responses of a 34-story building subjected to historical earthquakes. Experimental results demonstrate the proposed control strategy successfully replicates floor responses of the high-rise building that cannot be achieved formerly. [ABSTRACT FROM AUTHOR]

Monotonic and shaking table tests are performed using strip footings placed near a model slope. Test results indicate that footing restraint conditions affect the seismic response of near-slope footings, in terms of amplification factor and critical peak ground acceleration (PGA). The theoretical seismic bearing capacity correction factor (ηγe) vs. seismic coefficient (kh) relationships based on pseudo-static methods are in good agreement with the experimental values of ηγe provided that correction factors for load inclination, load eccentricity, footing set-back are accounted for. Furthermore, a correct empirical relationship between kh and PGA is vital in applying theoretical ηγe in earthquake engineering practices. [ABSTRACT FROM AUTHOR]

The paper presents and discusses seismic fragility functions of code-conforming buildings in Italy. The structures under consideration are taken from those considered by a large Italian research project (RINTC), aiming at evaluating the seismic reliability of new-design buildings. Design refers to a variety of structural typologies (i.e. un-reinforced masonry, reinforced concrete, steel, and precast concrete buildings) and configurations (e.g. number of stories, floor plan, and the presence of infills), as well as to sites with different hazard levels and local site conditions. The seismic fragility of the structures is evaluated via multiple-stripe nonlinear dynamic analysis using the equivalent-single-degree-of-freedom (ESDoF) systems calibrated based on pushover analysis of the three-dimensional structural models. The seismic response of the ESDoF models is also validated in terms of demand-capacity ratio and risk of failure compared to those of the three-dimensional structural models. Along with providing fragility curves for the buildings located at high-hazard sites, the study discusses the issues that significantly affect the fragility assessment for those located at low-to-mid hazard sites. [ABSTRACT FROM AUTHOR]

The behavior of base-isolated buildings under near-fault (NF) ground motions with fling-step and forward-directivity characteristics is investigated using three-dimensional nonlinear finite element models. Nonlinear response history analysis (NLRHA) is also carried out after removing the dominant pulse from the NF ground motion records. The results obtained for 10-story base-isolated buildings with and without shear walls, indicate that NF ground motions with fling-step and forward-directivity characteristics produce large inter-story drift ratios and floor accelerations, compared to the case when the dominant pulse is removed. Additional NLRHA carried out using artificial pulses shows that the isolator and superstructure responses are larger for pulses with fling-step characteristics, compared to pulses with forward-directivity characteristics. [ABSTRACT FROM AUTHOR]

Multistoried masonry infilled concrete (RC) frame with open ground storey has been recognized as a serious stiffness irregularity that has led to typical soft storey collapse of many buildings in past seismic events. Present study represents extensive static and dynamic analyses to investigate the seismic behavior of masonry infilled soft storied RC buildings. Several soft storied 2D frames with variation in number of storeys, number of spans, percentage of infilled frame panels, height to horizontal extent ratio as well as randomness of infill positions have been analyzed and the behavior of frames is investigated. Effect of variation of these parameters on base shear, natural period of vibration, storey drift etc. are studied. Results show that the base shear is significantly increased in presence of structurally active infill panels as compared to static analysis while randomness in the distribution of infill shows no appreciable influence. The findings show that seismic forces obtained from static analysis leads to significantly under-designed ground storey columns in soft storey buildings and are vulnerable during earthquake. Magnification of base shear as a function of amount of infill number of storeys are presented which may act as a guideline for the engineers towards safer design of columns and other elements of buildings with open and soft ground storey in a rational manner. [ABSTRACT FROM AUTHOR]

The paper develops a methodology for the seismic vulnerability assessment, Displacement-Based Assessment (DBA), of one-story and multi-story precast concrete frames with non-emulative connections. The method is based on the Direct Displacement-Based Design procedure initially developed by Priestley. The DBA is particularly suitable for the evaluation of the seismic response of flexible structures, as it considers displacements as the leading parameters to estimate the seismic vulnerability. The proposed procedure specifically accounts for the influence of beam–column connections, P-∆ effects, and second mode of vibration. The validation has been performed by means of nonlinear time history analyses. [ABSTRACT FROM AUTHOR]

An iterative framework is introduced in this present study to detect seismic isolation precursors of the shortcut calculation method for the isolated benchmark high-speed railway RC bridge. The spatial finite element (FE) analysis model of a benchmark isolated high-speed railway reinforced concrete (RC) bridge system under high-speed railway vehicles is set up based on the equivalent linear method. The vehicle with two bogies is assumed to be represented by a 3 D discrete rigid multi-body system with 23 degrees of freedoms (DOFs). The present study compares the nonlinear seismic response of a high-speed railway bridge with and without isolation bearings. Numerical results demonstrate that the isolation system with the optimal parameters can simultaneously reduce the deck displacement and the internal force of the isolated railway bridge under near-fault (NF) ground motions with various peak accelerations and peak velocity ratios, to ensure the adequate isolation efficiency of isolated structures. Specifically, the study shows that the seismic response of the seismically isolated bridge (IB) and the running safety indexes of the train are primarily dominated by the contents around the fundamental frequency of the train-bridge system subjected to the earthquakes. [ABSTRACT FROM AUTHOR]

There are numerous old arch bridges in Iran that have been used as railway bridges for more than 70 years. Field load testing of old railway bridges in km-23 and km-24 of Tehran–Qom railway have revealed important characteristics of the bridges and have proven that there is still a large capacity under service load. Since most of these bridges are not designed for earthquake excitation, seismic vulnerability of these structures is uncertain. This fact necessitates the investigation of the earthquake resistance of these kinds of bridges. In this paper, seismic performance of bridges is assessed by the pushover analysis. These bridges are plain concrete arch structures with different span length and mechanical properties which have been built 70 years ago. The results of dynamic load tests are used to calibrate a finite element model of the bridges in which a plain strain analysis is carried out. Using non-linear static analysis method, suggested by several modern standards, the capacity curves of the structures and non-linear demand spectrum are obtained. The choice of control nodes in the pushover analysis and their influences on seismic performance of plain concrete arch bridges are investigated. The crown, centre of mass and a virtual point are selected as control nodes and it is demonstrated that the capacity curves are almost identical in all control node cases. Finally, the demand levels of the bridges are determined and compared with capacity curves. The results show that the earthquake resistance of these kinds of bridges totally depends on material properties and geometry of the structures. [ABSTRACT FROM AUTHOR]

Prior to modern seismic codes, several road bridges were not designed for earthquakes in many moderate seismic regions. The seismic performance of these bridges is questionable. A portfolio of 30 non-seismically designed bridges is compiled for seismic reliability assessment. Fragility analysis is conducted, and the reliability of each structure is determined considering typical moderate seismic areas. The study shows that slab and multi-girder bridges with elastomeric bearings perform worse, whereas girder bridges with conventional bearings and multi-girder bridges with monolithic joints have better behavior. It is also shown that seismic design per Eurocode 8 leads to a reliability index of ~2. [ABSTRACT FROM AUTHOR]

Probabilistic loss modeling can be used to develop risk reduction measures, such as the identification of regions more prone to human and economic losses, or to develop financial mechanisms to transfer the earthquake risk from local governments to the private sector. This study addresses several critical issues in probabilistic loss modeling, and provides recommendations depending on the intended final use of the risk results. Modeling issues related to convergence in probabilistic event-based analysis; consideration of epistemic uncertainties within a logic tree; generation of different types of loss exceedance curves; and derivation of risk maps are thoroughly investigated. The Metropolitan Area of Lisbon is used to explore these issues, and it is demonstrated that different assumptions in the loss modeling process can lead to considerably different risk results. Furthermore, the findings and recommendations of this study are also relevant for institutions that promote the assessment of earthquake hazard and risk, such as the Global Earthquake Model Foundation. [ABSTRACT FROM AUTHOR]

Shear walls are important lateral force-resistant components of tall buildings. Hence, a reliable numerical model that can accurately represent the mechanical characteristics and large deformations of shear walls is critical for realistic collapse simulation of tall buildings. Based on the theory of generalized conforming element, a high-performance quadrilateral flat shell element, NLDKGQ, accounting for the large deformation using the updated Lagrangian formulation, is proposed herein and implemented in OpenSees. The reliability of NLDKGQ is validated using classical benchmark problems and reinforced concrete specimens. In addition, its capability in simulating the collapse of a tall building is also demonstrated. [ABSTRACT FROM AUTHOR]

We describe the formulation and application of an integrated general regional seismic loss assessment (RSLA) method for buildings in seismic regions. An efficient method for RSLA is valuable for engineers involved in city planning, risk management, and insurance dealings. In contrast to previously reported methods, the framework presented herein is hazard-based and utilizes a regional rapid seismic hazard deaggregation tool that allows regional assessment to be conducted more efficiently. The proposed technique is implemented as an example to assess general regional seismic loss in Los Angeles County for a ground motion hazard with 10% probability of exceedance in 50 years. [ABSTRACT FROM AUTHOR]

Many existing reinforced concrete (RC) structures around the world have been designed to sustain gravity and wind loads only. Past earthquake reconnaissance showed that strong earthquakes can lead to substantial damage to non-seismically designed RC buildings, particularly to their beam-column joints. This paper presents a novel retrofit method using buckling-restrained haunches (BRHs) to improve the seismic performance of such joints. A numerical model for RC joints is introduced and validated. Subsequently, a new seismic retrofit strategy using BRHs is proposed, aimed at relocating plastic hinges and increasing energy dissipation. The results indicate the retrofit method can effectively meet the performance objectives. [ABSTRACT FROM AUTHOR]

Recent studies have shown that the site coefficients obtained from site response analyses of Korean soil sites are significantly different from those specified in the current Korean seismic code, especially in the short-period portion of site response. This difference is mainly attributed to the shallow bedrock conditions (bedrock depth usually less than 30 m) in Korea. This study proposes a new site classification system and site coefficients for shallow bedrock sites based on site response analyses of more than 300 sites. The proposed site classification scheme and site coefficients proposed in this study are an improvement over the current seismic code and previous studies. [ABSTRACT FROM AUTHOR]

This paper first critically reviews a seismological model and then a three-segment curve model (in log-log space) to model the Q-f relationship is proposed to overcome the potential biased estimation in the long-period range by the "coda wave" method. The optimal curve-fitting process is performed to determine the Q-f relationship for the Hong Kong region. The calibrated seismological factors are incorporated with the stochastic simulation procedure to generate synthetic ground motions, which are validated through comparison with seismic records. The impact of long-period ground motions on the seismic response of high-rise buildings is finally manifested through a numerical study. [ABSTRACT FROM AUTHOR]

Most of buildings and structures are usually projected according to two main axes. However, the geographical position of these buildings varies randomly. Such random distributions of the azimuthal positions of structures, in most of the cities, generally, are not accounted for when assessing their seismic risk; certainly, the direction of the seismic loads is another highly random variable. Moreover, an additional important source of uncertainty is related to the structural response, mainly due to the random character of the mechanical properties. There is a consensus that uncertainties must be considered for adequately assessing the seismic risk of structures, but these directionality effects have not been deeply explored so far. In this article, the influence of the high uncertainty involved in these input variables on the expected seismic damage is analysed. Thus, an actual earthquake, which affected the southern part of Spain, is studied. Notably, damages on a group of affected buildings, located close to the epicentre, are analysed and discussed in detail. The results show that the influence of the random azimuthal position of structures is an important source of uncertainty and that it should be taken into account when estimating the expected seismic risk in urban areas. [ABSTRACT FROM AUTHOR]

This study investigates the seismic response of reinforced concrete buildings designed according to the current Italian building code. Number of stories, site hazard, presence and distribution of masonry infill panels, and type of lateral resisting system are the key investigated parameters. The main issues related to design and modeling are discussed. Two Limit States are considered, namely Global Collapse and Usability-Preventing Damage. The main aim of the study is a comparison between the seismic response of the buildings, investigated through nonlinear static and dynamic analyses. Irregularity in the distribution of infill panels and site hazard emerge as the most influential parameters. [ABSTRACT FROM AUTHOR]

This paper reports on results of nonlinear analyses performed within the RINTC project on an RC building isolated with different systems (High Damping Rubber Bearings, High Damping Rubber Bearings and Flat Sliding Bearings, Friction Pendulum System) and designed according to the Italian design code. The seismic response has been evaluated under different seismic input levels of two sites with different hazard and by considering two Limit States: Global Collapse and Usability-Preventing Damage. The influence of seismic stoppers and modelling uncertainties is also evaluated. Results permit to compute the implicit collapse risk and to identify critical aspects of current design procedures. [ABSTRACT FROM AUTHOR]

In this study, industrial single-story RC precast buildings are investigated. Twenty-four case studies have been considered, in which the column height, the beam spans and the seismic hazard level are varied. The seismic design of the selected case studies is performed according to the Italian building code and additional technical documentation. Three-dimensional nonlinear models are defined to perform static and dynamic analyses for the seismic assessment of the selected case studies. Demand/capacity ratios in terms of the selected engineering demand parameters are computed for ten increasing values of the seismic input return period. [ABSTRACT FROM AUTHOR]

This article describes the structural design, nonlinear modeling, and seismic analysis of prototype single-storey non-residential steel buildings made of moment-resisting portal frames in the transverse direction and concentric braces in the longitudinal direction. Various design parameters (building geometry, seismic hazard, foundation soil category) and different modeling assumptions (bare frame model, model including cladding elements, ground motions including vertical accelerations, and modeling uncertainties) were considered to investigate their effects on the simulated seismic performance. [ABSTRACT FROM AUTHOR]

GPS measurements recorded at active sites in central Italy during the seismic events of greatest magnitude (24 August, 26 and 30 October 2016) were processed in kinematic mode according to the Precise Point Positioning (PPP) technique. The resulting data were the displacements and, by derivation with respect to time, the velocities and instantaneous horizontal accelerations. Elastic response spectra along the orthogonal walls of the site (if the GPS antenna was fixed to a building) or along the geographical directions (if the antenna was fixed to the ground) were obtained from the derived accelerations. The maximum amplitudes, i.e. "peak vibrations", were then extracted from the response spectra. These peaks, unlike the co-seismic movements, represent the maximum instantaneous vibrations recorded following the "shock" produced by the seismic waves and thus are representative of both the discomfort perceived by the populations and the structural damage. This study shows that GPS is becoming an increasingly important tool to measure and monitor the dynamic responses of a structure. The results also provide a complete picture of the displacements induced by the seismic sequences in the earthquake-affected areas, leaving unresolved some questions concerning the localization of the phenomena and the causes of the structural deformations. [ABSTRACT FROM AUTHOR]

The paper analyzes the static behavior and the seismic vulnerability of the “San Francesco ad Alto” building in Ancona (Italy), which is currently used as a Regional Headquarter of the Marche Region by the Italian Army and was formerly a monastery. The global static structural behavior and the dynamic properties have been evaluated using the Finite Element modeling technique, in which the nonlinear behavior of masonry has been taken into account by proper constitutive laws. The concepts of homogenized material and smeared cracking are used to evaluate the capacity of the monastery to withstand lateral loads together with the expected demands resulting from seismic actions (N2 method), using a nonlinear static analysis (pushover). The comparison of seismic demand and capacity confirms the susceptibility of these types of buildings to extensive damage and collapse, as frequently observed in similar buildings. This paper aims to point out that advanced numerical analyses can offer significant information on the understanding of the actual structural behavior of historical buildings. It is believed that the methodology and the overall conclusions of this case study are valid for many historical monasteries in Europe. [ABSTRACT FROM AUTHOR]

Historical masonry structures are often located in earthquake-prone regions and the majority of them are considered to be seismically vulnerable and unsafe. Historical masonry towers are slender structures that exhibit unique architectural features and may present many inadequacies in terms of seismic performance. The seismic protection of such typologies of structures and the design of effective retrofitting interventions require a deep understanding of their behavior under horizontal loads. This paper presents the results of the seismic performance evaluation of historical masonry towers located in Northern Italy. A large set of case studies is considered, comprising a significant number of towers with high slenderness and marked inclination. First, a preliminary assessment of the dynamic behavior of the different towers is carried out through eigenfrequency analyses. Then, non-linear dynamic simulations are performed using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is adopted for masonry. The huge amount of results obtained from the non-linear dynamic simulations allows a comparative analysis of the towers to be performed in order to assess their seismic vulnerability and to show the dependence of their structural behavior on some geometrical characteristics, such as slenderness, inclination, and presence of openings and belfry. The evaluation of different response parameters and the examination of tensile damage distributions show the high vulnerability of historical masonry towers under horizontal loads, mainly in the presence of marked inclination and high slenderness. Some general trends of the seismic behavior of the towers are deduced as a function of the main typological features. [ABSTRACT FROM AUTHOR]

The paper evaluates seismic fragility characteristics of skewed bridges under simultaneous action of orthogonal ground motion components. The effect of skew angle on bridge seismic fragility characteristics is investigated through nonlinear time-history analyses of Painter Street Overpass, a 38.5° skewed bridge located in Rio Dell, CA, and six representative bridges with skew angles varying between 0° and 50°. Ground motion incident angle is varied from 0° to 180° to investigate the effect of the direction of ground motion incidence on bridge seismic performance. Bridge seismic response is used to generate fragility curves and contours plots that quantify the sensitivity of bridge fragility characteristics on skew angle and incident angle. For any value of incident angle, bridge seismic vulnerability increases with an increase in skew angle; however, no such general trend is found to describe the effect of incident angle on bridge fragility characteristics. Results show that the variation of maximum rotation of bridge columns for an earthquake does not follow any particular trend with the change in skew angle and incident angle. Analysis-based fragility curves are further compared with empirical fragility curves generated using real-life seismic damage data of skewed bridges and a reasonable agreement is observed between these two. [ABSTRACT FROM AUTHOR]

A procedure aimed to support designers in achieving structural improvements to reduce the seismic vulnerability of an electrical network is presented. This method based on the use of ASK4ELP software (Assessment of Seismic Risk for Electric Power Grids) allows minimising the costs of the actions needed in order to reach the required level of reliability, as defined by two different indexes of damage, namely the loss of transmitted power and the number of customers excluded from the service. An updating plan for the reinforcement of a power transmission grid includes the identification of its critical nodes, of the electromechanical components to be strengthened and of the related reinforcement level. In this paper, it is shown how the vulnerability assessment carried out with ASK4ELP can help in finding the optimal solution to these tasks, increasing the effectiveness-to-costs ratio. Three different empirical criteria for the individuation of the critical nodes are evaluated and the simulation of a significant part of the Italian transmission grid is presented: the results suggest that the most effective criterion for individuating the grid critical nodes should be given in terms of their exclusion probability. [ABSTRACT FROM PUBLISHER]

A seismic vulnerability procedure, based on the capacity/demand ratio approach, is applied to an irregular isolated bridge. Special features are incorporated in both, demand estimation and capacity evaluation. The seismic demand is represented by an average pseudo-acceleration spectrum derived from 159 earthquake accelerograms recorded in the region where the bridge is located. The capacity spectrum method is adopted for estimating the structural expected performance for several limit states. The capacity curve derived from a static non-linear procedure is obtained by means of a lateral load pattern that follows the displacement configuration, previously assessed by the use of time history analyses of the bridge supported on non-linear isolator bearings. Based on a moment–curvature analysis of the pier's sections, the maximum curvature ductility was established for each of the four defined performance limit states. Finally, probability density functions of the bridge capacity and demand were assessed and fragility curves were proposed aimed at determining the expected behaviour of the bridge as function of peak ground acceleration (PGA) of the typical strong motions recorded in the area. [ABSTRACT FROM PUBLISHER]

The objective of this work is to study the influence of various sources of uncertainties on the seismic response of structural systems. For this purpose, four test examples are considered, in particular two steel and two steel–concrete composite buildings. In order to study the impact of uncertainty on this type of structure, life-cycle cost analysis is performed for each structure, which is a measure of the damage cost due to future earthquakes that will occur during the design life of a structure. The calculation of the life-cycle cost of structural systems requires the calculation of the structural capacity in multiple earthquake hazard levels. Multicomponent incremental dynamic analysis (MIDA) is considered as one of the most efficient procedures for estimating the seismic capacity of 3D structural systems; therefore, in this work, MIDA is incorporated into the seismic loss estimation procedure. In order to take into account uncertainty on the mass, the material properties, the damping and the record-incident angle, the Latin hypercube sampling method is integrated into the MIDA framework. [ABSTRACT FROM PUBLISHER]

The seismic vulnerability of statues mounted on monolithic or multidrum columns is presented in this article. Emphasis is given to the procedure that should be followed for the assessment of the stability to future earthquakes, which is presented through the case study of the statue of Apollo at the Academy of Athens. The earthquake of 1999 (MW = 5.9), at a source distance of about 10 km, caused the base of the statue to slide on the column capital and rotate, with no evidence of any damage having been done to the column or to the Academy Building proper. Earthquake damage of monuments of this type is rarely noticed and, even if observed, is not reported in any detail. This particular case, therefore, offered the opportunity to investigate the stability of statues mounted on multi-drum columns, and also to present critical issues related to the assessment of their vulnerability, as the selection of the ground motions that should be used in the analysis, the determination of the parameters of the numerical models and the correct interpretation of the numerical results. Comments on the validity of the various methods currently in use by practicing engineers are also presented. [ABSTRACT FROM AUTHOR]