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To overcome negative effects of traditional masonry infilling walls (MIWs) on the seismic resilience of a self-centering prestressed concrete (SCPC) frame, a novel SCPC frame with sliding infill walls (SCPC-SIW frame) is proposed. This study compares the seismic performance of the SCPC-SIW frame and the SCPC frame with MIWs (SCPC-MIW frame) through quasi-static tests, fragility analysis, and risk assessment. To begin, quasi-static tests on single-story SCPC-SIW and SCPC-MIW frame specimens are performed to compare their failure characteristics, hysteresis response, energy dissipation, and self-centering ability. The numerical simulation methods for SCPC-SIW and SCPC-MIW frame specimens are then presented and validated. Subsequently, two four-story SCPC-SIW frames and two four-story SCPC-MIW frames are designed, and their dynamic response under MCE is preliminary analyzed. Finally, the fragility analysis and risk assessment of these multi-story SCPC-SIW and SCPC-MIW frames are conducted to determine the probability of their peak inter-story drift ratio (PIDR), residual inter-story drift ratio (RIDR), and peak floor acceleration (PFA) exceeding the specified limit states under any intensity earthquake and within 50 years. The results indicate that, except for cracks caused by fatigue damage appearing on the SIW at the end of loading, the SCPC-SIW frame specimen remains undamaged, whereas the SCPC-MIW frame specimen exhibits diagonal step cracks on the MIW. The hysteresis curve of the SCPC-SIW frame specimen exhibits an ideal and repeatable flag shape, whereas the stiffness and strength of the SCPC-MIW frame specimen degrade during the test. Besides, the probability of exceeding the 4% PIDR and exceeding 0.2% and 0.5% RIDRs within 50 years for the SCPC-SIW frame is significantly lower than that for the SCPC-MIW frame. The SCPC25-MIW frame has a higher probability of exceeding the 1 g PFA within 50 years than the SCPC25-MIW frame. In other cases, the SCPC-SIW frame has a lower probability of exceeding 1 g, 2 g, and 3 g PFA within 50 years than the SCPC-MIW frame. [ABSTRACT FROM AUTHOR]

Slopes have a significant impact on the ground motion characteristics, which can aggravate the damage degree of building structures during a strong earthquake. However, many studies have focused on the design response spectra under flat site conditions and fewer researchers have investigated the impact of slope topography on the design response spectra. In this study, the numerical simulation is used to obtain the seismic response of slopes and the differential evolution algorithm is used to obtain the standardized response spectra of the acceleration time histories along the ground surface behind the slope crest. The impacts of slope height (H), slope gradient (i), average shear wave velocity in the top 30 m (VS30) and distance from the slope crest (x) on the characteristic parameters of the design response spectra are then investigated. The results show that H, i, VS30 and x have a little influence on the normalized second inflection point period (mean(Tg/Tg,ff)) but a great influence on the normalized plateau value (mean(αmax/αmax,ff)). Specifically, both mean(Tg/Tg,ff) and mean(αmax/αmax,ff) show a trend from increasing first to decreasing and stabilizing finally as x increases; the mean(αmax/αmax,ff) shows an increasing trend as H increases, but a decreasing trend as i or VS30 increases. Finally, to provide some guidance for the seismic design of building structures near slopes, two approximate relationships are proposed: (1) between mean(Tg/Tg,ff) and x, and (2) between mean(αmax/αmax,ff) and H, i, VS30, x. The main innovation of this paper is that the relationship between the characteristic parameters of the design response spectra and the slope site characteristic parameters is clearly summarized and quantified for the first time. [ABSTRACT FROM AUTHOR]

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]

Empirical and probabilistic risk analysis methods can relatively accurately predict the seismic vulnerability of reinforced concrete (RC) structures. Using various intensity measures to estimate and forecast the seismic hazard of RC structures can contribute to the development of typical structural seismic resilience and vulnerability models. However, traditional empirical and analytical vulnerability studies rely more on field observation data and seismic risk algorithms and less on numerical simulation analysis for validation and optimization, resulting in limitations and fuzziness in the accuracy of the developed structural risk models. To explore the damage modes of RC frame structures under different intensities, this paper innovatively combines numerical model algorithms with empirical vulnerability methods to conduct empirical vulnerability and numerical simulation analyses on RC structures. Using probability statistics and nonlinear regression analysis methods, a prediction model for estimating the fragility of RC structures was proposed, and 858 RC structure damage samples from a typical city (Dujiangyan) during the Wenchuan earthquake in China on May 12, 2008, were used for model verification and comparative analysis. Using seismic response analysis theory, 901,530 acceleration records of the Wenchuan earthquake detected by eight actual seismic stations were selected, and nonlinear dynamic time history analysis was conducted. A four-story RC structural model was established using finite element software, and numerical simulation analysis was conducted on the model using 117,863 real earthquake acceleration data points obtained from actual monitoring stations during the Wenchuan earthquake. The acceleration time history curves and incremental dynamic analysis curves of the RC structure under different intensity measures were generated. By combining the moire algorithm and numerical simulation technology, damage stress clouds of steel bars and concrete under different intensity measures were generated, and the accuracy of the developed empirical vulnerability model was verified via numerical simulation results. [ABSTRACT FROM AUTHOR]

The track structure has an effect on the dynamic characteristics of the bridge structure, which makes the seismic response of the bridge structure complicated. In this paper, an assessment method is proposed to evaluate the seismic risk of bridge structure, including over-limit risk and over-limit scale. Based on a newly proposed simplified model with high accuracy and high computational efficiency, a total of 3000 calculation conditions are analyzed and the sample stability of response is validated to ensure the reliability of the seismic risk analysis. The seismic risks in the longitudinal direction of the track-bridge model are compared with that of the trackless model, and the influence of the constraint effect of China Railway Track System II ballastless track structure on the seismic risk of the structure is obtained. The influence of the number of spans and PGA on track constraints is also revealed. The analysis results, based on a large number of samples, show that although track constraints can reduce the seismic risk of some phenomenon, such as girders' collision, the expected enhancement of longitudinal seismic safety of the system cannot be guaranteed in general, especially when the number of spans is large. However, it is noted that the track constraint can effectively control the over-limit scale of the system, which can reduce the expected repair cost after an earthquake. Therefore, it can be considered that the positive effect of the track constraints is more significant in economy than in structural safety when the bridge is subjected to a longitudinal earthquake excitation. [ABSTRACT FROM AUTHOR]

The ability of an intensity measure (IM) to accurately reflect the characteristics of ground motions is of utmost importance for seismic fragility assessment. Traditional investigations focused on selecting the optimal IM have primarily been conducted based on ordinary reinforced concrete (RC) structures. The direct application of IM specifically tailored for ordinary RC structures in the fragility analysis of self-centering prestressed RC (SCP-RC) structures will potentially introduce increased uncertainties of ground motions. This paper aims to conduct a comprehensive analysis to identify the optimal vector-valued IMs (vIMs) for the fragility assessment of SCP-RC structures. A total of eight vIMs were constructed by combining various scalar-valued IMs (sIMs) associated with the peak values and spectra of ground motions. A 5-story SCP-RC structure was designed to evaluate the efficiency and correlation of the established vIMs using a multi-parameter damage measure (mDM). Probabilistic seismic demand models for the eight examined vIMs were developed. A comparative analysis between the fragility surface slices obtained using the identified optimal vIM and the fragility curve derived from the corresponding sIM was performed. The results indicate that (PGV, I N p /PGV) is the most suitable vIM for accurately quantifying the fragility of SCP-RC structures. The seismic fragility surface is more efficient than fragility curve in estimating the seismic performance of SCP-RC structures. [ABSTRACT FROM AUTHOR]

Earthquakes are a major cause of damage and human losses to the built environment, including cultural heritages, monumental buildings and historical centers. In the last decades, the seismic performance of buildings has received special attention due to the interest in the built heritage conservation and protection of human life, particularly with respect to masonry structures which have shown evidence of poor behavior once subjected to seismic loads. The present work contributes to the seismic safety assessment of the out-of-plane behavior of unreinforced masonry walls through a displacement-based approach, providing the capacity for different out-of-plane geometric indexes and its seismic response in different earthquake-prone regions. The analyses are conducted using a seismic probabilistic framework, considering the most common out-of-plane mechanisms, different material properties, various slenderness ratios, and a wide range of seismicity levels to cover the seismic hazard in Europe. The results presented can be useful for seismic safety assessment and to incorporate vulnerability models for seismic risk analysis. [ABSTRACT FROM AUTHOR]

Pushover analysis is a common nonlinear static procedure, performed to evaluate seismic response of civil structures. This approach allows considering the structural nonlinear behavior under earthquake loading in a simplified yet effective way; however, in its classic formulation, it is limited by restrictive and unrealistic assumptions. Thus, the basic method is inadequate for the accurate analysis of buildings without a vertical plane of symmetry and/or for multi-component earthquakes, where torsion effects cannot be neglected. Furthermore, standard pushover analysis only comprises one dominant mode of vibration; higher modes, and therefore their effects, are not accounted for. For all these reasons, the standard technique is generally not considered suitable for the assessment of buildings at high risk of natural-technological (NaTech) events, such as nuclear facilities in areas of high seismic activity. To overcome these limitations, a multi-modal pushover analysis procedure is here tested and validated on the data from a non-symmetric structure (the SMART case study) under multi-component earthquakes. In detail, the procedure applies a linear combination of modal load patterns, defined according to the well-established Direct Vectorial Addition (DVA) method. With respect to other existing multi-modal pushover analysis techniques, elliptical response envelopes are employed to calculate the corresponding combination factors. Innovatively, the identification of the dominant modes for the load pattern is not limited to the classic maximization of the forces at the basis of a structure but rather generalized to shear and displacement maximization at different heights and locations throughout the whole structural frame. [ABSTRACT FROM AUTHOR]

Analysis of recorded seismic response of an eight-story passively-controlled steel building located in Sendai is reported in this paper. Vibration monitoring system has been instrumented to test the effectiveness of dampers and actual performance of passively-controlled structures under earthquake since it was constructed in 2003. A data-driven stochastic subspace identification methodology with an alternative strategy to remove spurious modes is developed and implemented to the recorded actual earthquake response to extract dynamic properties of the passively-controlled eight-story steel building from the recorded floor acceleration data. Thus, the inherent damping characteristic of the building is identified under various earthquakes. Moreover, the variation of the estimated natural frequencies, mode shapes, and damping ratios for all the earthquake recordings are illustrated. To further investigate serviceability of the passively-controlled steel building during an earthquake, probabilistic model updating is developed to estimate the model parameters and infer the response of the structure based on the identified modes. Besides, seismic performance assessment of the passively-controlled steel building from the estimated dynamic characteristics and model parameters during service period is also discussed. [ABSTRACT FROM AUTHOR]

The performance of clay-pile-pier system under earthquake shaking was comprehensively examined via three-dimensional finite element analyses, in which the complex stress-strain relationships of a clay and piled pier system were depicted by a hyperbolic-hysteretic and an equivalent elastoplastic model, respectively. One hundred twenty ground motions with varying peak accelerations were considered, along with the variations in bridge superstructure mass and pile flexural rigidity. Comprehensive comparison studies suggested that peak pile-cap acceleration and peak pile-cap velocity are the optimal ground motion intensity measures for seismic responses of the pier and the pile, respectively. Furthermore, based on two optimal ground motion intensity measures and using curvature ductility to quantify different damage states, seismic fragility analyses were performed. The pier generally had no evident damage except when the bridge girder mass was equal to 960 t, which seemed to be comparatively insensitive to the varying pile flexural rigidity. In comparison, the pile was found to be more vulnerable to seismic damage and its failure probabilities tended to clearly reduce with the increment of pile flexural rigidity, while the influence of the bridge girder mass was relatively minor. [ABSTRACT FROM AUTHOR]

Seismically triggered subaqueous mass movements in lakes may generate tsunamis that can cause significant damage on the shore. In this study, we assess the seismic response and stability of subaqueous slopes in Swiss lakes based on recorded seismological data, historical and geological information and geotechnical surveys. We performed seismic investigations at multiple locations in Lake Lucerne using Ocean Bottom Seismometers (OBS). For these locations, we derived ground-motion amplification functions from local and regional earthquakes and horizontal-to-vertical spectral ratios (H / V) from the earthquake and ambient vibration recordings. The results show (1) very high amplification levels, often exceeding values of 50–100 in the frequency range between 1 and 10 Hz, (2) the fundamental frequency of resonance in the range of 0.5–3.5 Hz and (3) laterally variable site response even for closely located stations. We sought also the signatures of non-linear site response in the H / V curves or ground-motion amplification functions but found only weak indicative effects and no clear evidence. This is most likely due to the low levels of ground motion recorded during the OBS campaigns. We conducted back analyses of historical earthquakes in Switzerland with available documental and/or geological evidence of induced (tsunamigenic) subaqueous slope failures in Swiss lakes. The data set of historical events was complemented with a selection of instrumentally recorded earthquakes in Switzerland. For the analyses, we selected multiple sites in Swiss lakes which failed in the past or are prone to failure in the future. We modelled the ground motion at these locations assuming Swiss standard reference rock conditions (v s 30 = 1105 m s−1). The modelled ground motion intensity measures (IM) included peak ground acceleration (PGA), peak ground velocity (PGV) and pseudospectral acceleration (PSA) at 0.3, 1 and 2 s. We estimated the minimum ground motion and macroseismic intensity at reference rock conditions required to trigger the failures of subaqueous slopes. In addition, we defined a threshold for the seismic triggering of such failures in terms of moment magnitude (M w) and epicentral distance (Re) as: $$\begin{eqnarray} M_{\rm w}=2.891+1.904\log_{10}(R_e+5.166)\: {\rm for}\: R_e\ge 3.7\: {\rm km}. \end{eqnarray}$$ Our results are consistent with previous studies based on worldwide observations. Furthermore, we related the modelled ground motions to the Swiss seismic hazard products and estimated the return period of critical ground shaking responsible for triggering subaqueous slope failures (with potential for tsunami generation) to be in the range of 36–224 yr. Finally, based on previously collected geotechnical data (in situ Cone Penetration Testing and laboratory sediment analysis), we determined the most likely values of the seismic coefficient k to be used with the ground motion IMs modelled at reference rock conditions in infinite slope stability analyses to estimate the factor of safety (FS). For PGA, we found a k = 1; for PGV, k = 2; for PSA0.3s, k = 0.6; for PSA1s, k = 2 and for PSA2s, k = 5.5. These estimates are conservative and affected by the trade-off between the thickness of unconsolidated sediments and the slope angle. Thus, we recommend applying them to slopes with a low-to-moderate gradient (<15°) and sediment thickness of more than 2 m. [ABSTRACT FROM AUTHOR]

As a physical analysis method, susceptibility not only predicts the probability of failure of a structure under different hazard levels but also prevents disasters induced by structural damage due to vulnerable members. To study the susceptibility of steel clarification tank under earthquake action, this study analyzes the dynamic response of steel clarification tank under near-field impulse, near-field no impulse, and far-field ground shaking, derives IDA curve clusters by incremental dynamic analysis method, and conducts related studies to analyze the susceptibility of clarification tank structures through susceptibility curves. The results of the study show that the probability of failure of the clarification tank under different ground shaking intensities is different. The probability of liquid wave height transcendence of the clarification tank under seismic action is the largest, the probability of liquid wave height transcendence of the clarification tank under near-field pulsed seismic action is the second, the probability of liquid wave height transcendence of the clarification tank under near-field nonpulsed seismic action is the smallest, and the probability of transcendence occurs similarly in near-field pulsed and far-field seismic actions. [ABSTRACT FROM AUTHOR]

This article presents a methodology to assess the seismic vulnerability of essential buildings through analytical fragility curves, applied to the administrative building of the Universidad Nacional del Centro del Perú, for various damage states and different levels of seismic demand according to ATC-40 and SEAOC -VISION 2000. It is shown that the fragility curves through the probability of damage matrices allow us to reasonably estimate the probable state of the building after a seismic event, which in the case of the building under analysis shows that it is more vulnerable in the North-South direction (Y axis). [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]

Severe failure of improperly designed and poorly constructed structures may occur due to the amplified and prolonged ground motion during an earthquake, and hence prediction of the ground motion characteristics at the soil surface is crucial. In this study, based on the prepared simplified engineering geomorphic map, we performed a one-dimensional (1D) nonlinear site response analysis for seismic site characterization of the recently proposed Detailed Area Plan (DAP) area of Dhaka City, the Capital of Bangladesh. The engineering geomorphic unit-based map was prepared from image analysis and verified with the collected borehole data and surface geology map. The study area was classified into three major geomorphic units and seven sub-units subject to the subsurface soil profiles. Nine earthquake time histories, seven from the PEER NGA WEST2 data set and two synthetics, and seven identified subsurface soil profiles were used for nonlinear site response analysis, along with the BNBC 2020 uniform hazard spectrum as the target spectrum. For the selected earthquake ground motions, the near-surface soil response of the DAP area showed de-amplification of acceleration in the short period and amplification of acceleration in the long period. The amplified long-period acceleration could cause severe damage in inappropriately designed and poorly constructed long-period structures. The outcome of this study could be used to prepare a seismic risk-sensitive land use plan for the future development of the DAP of Dhaka City. [ABSTRACT FROM AUTHOR]

A method to calculate structural functionality for building structures based on structural natural frequency was proposed for seismic loading events. Structural functionality loss and recovery were determined by monitoring the change of structural natural frequency during the earthquake events or repair activities. A shape factor was introduced, structural functionality recovery function (SFRF), to consider the repair strategy and repair speed. As an example, this method was applied to obtain the structural functionality curve and seismic resilience of a half scale two-story reinforced concrete (RC) frame structure. This structure was subjected to a series of ground motions on a shake table and then repaired by carbon fiber cloth a total of four times. The results indicate that the SFRF is able to capture the recovery trend of a structure in the repair process. Meanwhile, a damage index-repair target (DI-RT) curve, representing the 5% difference between the proposed and traditional SFRFs, was used to investigate the impact of structural damage degree and repair target. The areas above the curve indicates that the difference between the proposed and traditional SFRFs cannot be ignored. [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]

The seismic vulnerability of bridges may be reduced by the application of Geotechnical Seismic Isolation (GSI) below the foundations of the columns and the abutments. However, the role of GSI on the seismic response of bridges has been limitedly examined in literature. Therefore, this research has been conducted to study the effect of applying GSI on the seismic response of bridges to address the aforementioned gap in knowledge. Advanced nonlinear dynamic three-dimensional finite element analyses have been conducted using OpenSees to study the influence of the GSI. The cases of traditional and isolated bridges subjected to earthquakes have been considered to assess the GSI effects. The results showed that the GSI reduces the seismic effect on the column while its effect seems to be less significant for the abutments. In addition, fragility curves for the traditional and isolated cases have been developed and compared to provide insights with a probabilistic-based approach. The results of this paper provide a useful benchmark for design considerations regarding the use of GSI for bridges. [ABSTRACT FROM AUTHOR]

• A generalized CWT method is proposed for multi-pulse ground motion identification. • The proposed method overcomes the limitation of the classical CWT method that requires a wavelet basis. • Single- and multi-pulse ground motions from two near-fault earthquakes are identified. • The spectral velocity of multi-pulse ground motion may contain multiple peaks in the high-period range. The near-fault pulse-like ground motion is of practical importance since it tends to cause severer damage to structures than ordinary ground motion in engineering and helps characterize the seismic source and the kinematic characteristics of the geological fault in seismology. However, previous investigations mainly focus on single-pulse ground motion. As one of the particular seismic records in the near-fault earthquake, the multi-pulse ground motion is rarely considered caused by the absence of an effective identification method. Hence, a generalized continuous wavelet transform (GCWT) method is proposed by combining convolution analysis with evaluation parameters to facilitate wider studies on multi-pulse ground motion. In identification, the proposed method requires each pulse in the multi-pulse ground motion to satisfy the same criteria and excludes the effects of attenuation component. In methodology, the proposed method overcomes the limitations of the classical CWT method that requires a wavelet basis and provides a workable and flexible framework for pulse-like ground motion identification. Based on the method, single- and multi-pulse ground motions from two typical near-fault earthquakes on the PEER NGA-West2 database were identified. The effects of the pulse model and ground motion orientation on identification are discussed. Besides, the 5% damped spectral velocity of multi-pulse ground motions potentially contain multiple peaks in the high-period range. This phenomenon implies that the risk would be underestimated for the response spectrum-based seismic hazards and risk analysis if the multi-pulse features are not, or are insufficiently taken into account. [ABSTRACT FROM AUTHOR]

Drift-based performance limits are commonly used in seismic performance assessment. However, many studies have indicated substantial considerations for the displacement-based approach when applied to historical masonry structures. Variability in failure mechanisms, geometrical uncertainties in structural form, loading and boundary conditions and incompatible performance damage limits among codes can be examples to such considerations. This article discusses the reliability of the drift limits recommended in different codes and guidelines by comparing drift values obtained from the time-history and pushover analyses of 11 historical masonry mosques. The effect of material stiffness on the drift capacity of the structures was evaluated in regards to possible lower and upper value of modulus of elasticity in masonry elements. It was determined that the drift values proposed in the codes and guidelines can lead to incorrect and unsafe seismic evaluation on architectural heritage. For historical masonry mosques, global drift ratio values between 0.01–0.07, 0.06–0.25, 0.08–0.45% are recommended for damage limitation, significant damage and near collapse limit states, respectively. Simplified equations incorporating dimensional and mechanical properties are proposed to determine the drift ratio limits of historical mosques. [ABSTRACT FROM AUTHOR]

The evaluation of seismic risk in structures requires information on both site hazard and structural vulnerability. Hazard can be quantified via probabilistic seismic hazard analysis, while seismic vulnerability can be quantified using structural analysis; the former is typically specified via predefined national hazard models, whereas the latter is more structure-specific and can be computationally expensive depending on the numerical modelling and analysis procedure complexity. As a compromise, various simplified seismic response evaluation methods have emerged and been implemented in assessment codes and guidelines (e.g., N2 method in Eurocode 8, SPO2IDA in FEMA P695). Furthermore, the seismic assessment and rehabilitation of existing structures have seen the introduction of risk classification guidelines. These are tools to primarily assist practitioners and decision-makers in understanding and managing seismic risk and the possible implications of different retrofitting schemes. Risk classification guidelines typically use loading-based quantities such as the seismic capacity-to-demand ratio. However, several drawbacks are associated with adopting loading-based quantities, namely the lack of uniformity of the actual seismic risk, expressed as a mean annual frequency of limit state exceedance. To address these drawbacks, this paper outlines a relatively simple pushover-based methodology for the direct evaluation of seismic risk (PB-Risk) for non-ductile infilled frame structures. The article describes a step-by-step framework for the simplified characterisation of hazard, vulnerability and subsequently seismic risk. It is quick and easy to implement within a practical and code-based setting and can be adopted within risk classification guidelines. The application of the proposed PB-Risk methodology is demonstrated via several case study applications, and its robustness in characterising seismic risk with respect to other simplified non-linear static formulations for infilled frame buildings is shown. [ABSTRACT FROM AUTHOR]

Conversely, the numerical modeling of the seismic behavior of masonry structures represents a very complex problem due to the constitutive law of this structural material and its highly nonlinear behavior. Historical structures represent a significant percentage of existing constructions in numerous seismic-prone regions, and some of these are iconic monuments of their countries. Damage fragility curves were identified for typological building classes, defined by considering parameters present in both post-earthquake observations and census data with the aim of extending the results to the whole national territory. [Extracted from the article]

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]

This is achieved by fitting different parametric device models to experimental data from a shaking table testing campaign for a scaled three-storey frame structure equipped with TID/TMDI with hysteretic gel dampers as well as with viscous eddy current dampers. The emergence of the inerter, both as an idealized mechanical element and as a device, contributed a new dimension to the field of structural vibrations control over the past 20 years, by enabling the provision of readily scalable inertia to structures and to dynamic vibration absorbers without adding any significant gravitational mass. In this respect, the inerter element and associated devices complement the frequency-independent negative stiffness (NS) device configurations, oftentimes materialized technologically through pre-tensioned springs, which have also attracted significant recent interest for seismic response mitigation of buildings. [Extracted from the article]

Long-span cable-stayed bridges often have a design service life of more than a hundred years, during which they may experience multiple earthquake events and accumulate seismic damage if they are located in seismic-prone regions. Earthquake occurrence is discretely and randomly distributed over the life cycle of a long-span cable-stayed bridge and often causes sudden drops in the structural performance instead of yearly fixed seismic performance degradation. This study thus proposes a digital twin-based life-cycle seismic performance assessment method for long-span cable-stayed bridges. The major components of this method include: (1) a seismic hazard analysis-based generation method of earthquake occurrence sequence; (2) a digital twin-based structural response prediction method considering lifetime earthquake occurrence and sequence; and (3) a service life quantification method. The proposed method is applied to a scaled long-span cable-stayed bridge with a series of shake table tests. The results show that the digital twin can closely reproduce the life-cycle seismic response of the bridge under sequential earthquakes. The proposed assessment method provides a more intuitive presentation of the life-cycle seismic damage accumulation process and a more accurate estimation of the service life of a long-span cable-stayed bridge. [ABSTRACT FROM AUTHOR]

In the context of fluid-induced seismicity, various injection parameters have been shown to affect fault behaviour differently, although existing studies about their effects sometimes show contradictory results. Aseismic slip is also known to affect seismicity, but its exact contribution remains elusive. To address these, we perform numerical modelling to understand the effects of injection volume and rate on long-term seismic and aseismic fault slip behavior. Our results suggest that both parameters can affect various aspects of fault behaviour to different extents, and, in some cases, their roles are interdependent, thus they should be examined simultaneously in order to fully characterize their effects on triggered fault responses. Within the model space, we observe the fault predominantly releasing aseismic energy, which plays a significant role in altering the timing of triggered earthquakes that follow and exhibits lasting impacts in subsequent seismic cycles. In terms of seismic responses, increasing injection rate enhances the size of the triggered cluster, while increasing injection volume increases seismicity rate of the sequence. Detailed characterization of the patterns of earthquake occurrence and moment release with respect to different injection parameters can offer insights into establishing safe bounds of injection operation and potentially mitigate seismic hazard. [ABSTRACT FROM AUTHOR]

Seismic design codes have imposed some limitations on the maximum subtended angle of curved bridges and allow engineers to analyze and design them using an equivalent straight bridge. This paper investigates these limitations and evaluates the AASHTO code recommendations regarding the prediction of the seismic responses of curved bridges using an equivalent straight bridge for bridges with different abutment properties at different seismic hazard levels. In this regard, the seismic responses of 21 horizontally curved and straight RC four-span bridges with different abutment types are investigated. In 7 bridge models, soil-abutment-bridge interaction is neglected, while in the rest of the bridge models, the seat-type abutments with the participation of the nonlinear backfill soil, gap, and abutment piles are used in structural modeling. First, nonlinear static (pushover) analyses are carried out to evaluate the overall behavior of the bridges with different abutment configurations in the two perpendicular principal directions. Subsequently, nonlinear time history analyses are performed to predict the seismic response of bridge elements, including column drifts and deck displacements at the place of the abutments in the radial and tangential directions at different seismic intensity levels, including the design basis earthquake (DBE) and maximum credible earthquake (MCE) excitation levels. In addition, the actual maximum displacements of the components of the bridges (i.e., the total absolute displacements) were also predicted and evaluated for different cases. It was found that the abutment properties and boundary conditions had a significant effect on the seismic response assessment of curved bridges compared to straight bridges, while such parameters are not currently considered by the design codes. The results also indicated that by increasing the seismic intensity level, more limitations should be imposed on the use of the equivalent straight bridges. [ABSTRACT FROM AUTHOR]

Pinching characterizes the hysteretic response of several structural systems. It is associated with a reduced dissipated hysteretic energy under cyclic loading and can significantly affect seismic performance, especially under repeated earthquakes. Although several scholars proposed advanced joint arrangements with reduced pinching, ordinary timber structures present pronounced pinching effects due to the local damage to the timber joints. This paper quantifies the impact of variable pinching on the seismic performance of a timber structural archetype. The authors modeled the hysteretic response of a light-timber framed assembly using an empirical hysteresis model and assessed the sensitivity of the displacement demand of the chosen archetype to pinching, number of earthquake repetitions, and spectral acceleration. The choice of an elementary structural archetype, rather than a more complex system, allows isolating the effects of pinching, which could otherwise be disguised by other phenomena, like force redistribution between structural assemblies due to plasticization. [ABSTRACT FROM AUTHOR]

A new scheme of seismic strengthening of adobe structures has been proposed in this paper. The scheme involves horizontal and vertical bands of steel wire mesh plastered with cement-sand mortar. The effectiveness of the proposed scheme is assessed by dynamically testing a half-scale model of the adobe structure on a shaking table. The acceleration time history record of the 1995 Kobe earthquake was used to simulate the ground motion for the strengthened model which was increased sequentially in increments of 25% of peak ground acceleration (PGA). Initial (hairline) cracks were observed in the in-plane wall of the model at a PGA of 0.439 g. Although the out-of-plane walls also sustained damages, the in-plane walls were the most damaged parts of the structure. The proposed strengthening method reduced the torsional irregularity of the structure. It also increased strength, ductility and energy dissipation capacities of the walls. The data of observed structural damages and building drift were used to propose four performance levels for the strengthened adobe structures corresponding to the applied PGAs of ground motion. [ABSTRACT FROM AUTHOR]

Bridges are critical links in a transportation network that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. In order to explore the damage probability of long span prestressed concrete continuous rigid frame bridge in the event of earthquake, this study took the Longxi Jialing River Bridge as an example and presents seismic vulnerability assessment based on the incremental dynamic analysis method. Taking the curvature of the pier's most unfavorable section as the damage index, the seismic vulnerability curve of the pier was established with peak acceleration(PGA) as the independent variable and the probability of the structure exceeding a specific damage state as the dependent variable. Results demonstrate that under the action of a near-field earthquake, when PGA =0.5 g, the failure probabilities of slight damage is 0.02926, the failure probabilities of moderate damage is 0.01823, and the failure probabilities of severe damage is 0.00075. When PGA = 1.0 g, the failure probabilities of slight damage is 0.672 and 0.597 for moderate damage, 0.20109 for severe damage, and 0.00484 for complete damage. Under the action of a far-field earthquake, when PGA = 0.5 g, the failure probability of slight damage is 0.00194, and the failure probability of moderate damage is 0.00101 along the span direction. When PGA = 1.0 g, the failure probability of slight damage is 0.04358, 0.02802 for moderate damage, and 0.00138 for serious damage along the span direction. The complete damage of the bridge hardly occurs. With the increase of intensity of an earthquake, the failure probability of the pier gradually increases. After entering the moderate damage stage, the pier has relatively good ductility. This study provides a good reference for the seismic design of similar bridges. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular Y-shaped (CFST-Y) piers are good candidates for meeting the structural and aesthetic requirements of bridges. By using the theoretical and nonlinear static (pushover) analyses, the seismic performances of three types of CFST-Y piers were evaluated at different seismic hazard levels. The theoretical formulas were first proposed to estimate the lateral stiffnesses for piers with different pier–deck connections. Then, the structural ductility with the development of plastic hinges in piers was investigated based on the pushover analyses. The results demonstrate that the structural dimensions, deck mass, shear limit, and stiffness of bearings can remarkably affect the formation of hinges and thereby lead to different energy dissipation patterns to achieve the expected performance in piers. The findings suggest an economic design strategy of piers, using CFST-Y members as energy dissipation fuses with multiple hinges, to achieve low-level seismic performance cost-effectively. [ABSTRACT FROM AUTHOR]

Earthquakes have occurred frequently in western China (Sichuan, Tibet, etc.) while the complex site conditions in western regions bring great uncertainty to the seismic performance of isolated high-speed railroad bridges (HSRBs). By studying the relationship between structure-dependent and structure-independent seismic intensity measures, soil site conditions are taken into account in the probabilistic seismic demand model (PSDM), which is applied to analyze the failure probability of the isolated HSRB under different site conditions. Based on the design parameters and test results of a typical isolated HSRB in western region, the analysis of the finite element model of the structure was performed. Probabilistic seismic demand models of the isolated HSRB were developed. The seismic fragility curves of the isolated HSRBs were obtained and the failure probabilities under different site conditions were compared and analyzed. The evaluation of the failure probability that the failure probability of the isolated HSRBs in the site area with seismic intensity of 9 is 35.84% and 78.19% under the soil site categories D and E, respectively. Therefore, the seismic spectrum characteristics of the soil site are an important factor affecting the seismic response of isolated HSRB structures. This study provides a more effective modified PSDM for seismic performance assessment of isolated HSRBs under the different site conditions. [ABSTRACT FROM AUTHOR]

This study evaluates the influence of site-specific strong-motion duration caused by interplate earthquakes on structural performance. Specifically, the seismic response of an equivalent single-degree-of-freedom (SDOF) system subjected to a set of accelerograms recorded at different soil-profile sites located in Mexico City is analyzed. The properties of the equivalent SDOF system were estimated from the dynamic characteristics and pushover curve of a steel frame. The accelerograms, whose total durations, t r , vary from approximately 120 s to 350 s, are associated with earthquakes that occurred in the Mexican subduction zone. In addition, several synthetic accelerograms were generated to evaluate the seismic performance of the equivalent SDOF system via fragility curves. Operational, life safety, and collapse performance levels were assessed. In particular, two approaches were considered for the evaluation of the effects of the strong-motion duration on the performance of the equivalent SDOF system. The first approach uses the peak displacement of the system as the engineering demand parameter (EDP), whereas the second approach uses an energy-based damage index. Results indicate that the strong-motion duration has a significant influence on the nonlinear response of the equivalent SDOF system when considering any of the mentioned EDPs. Overall, the greater differences in fragility are seen for sites that show the greatest response-spectrum amplitudes in the range of dominant periods, T s , near the fundamental period of the equivalent SDOF system. This study demonstrates the importance of properly characterizing the strong-motion duration when selecting site-specific accelerograms to perform nonlinear dynamic analyses. [ABSTRACT FROM AUTHOR]

Bond slip in RC beam–column joints may affect the seismic response or performance assessment of structures considerably. Explicit macroscopic models that satisfy the joint kinematics can be incorporated within a frame model to numerically account for the effect of bond slip. Seismic performance assessment of buildings generally rules out the explicit modeling owing to the associated computational cost. Simplified implicit models are instead preferred owing to the ease of implementation in a commercial finite element (FE) provided the model parameters are calibrated experimentally. Extrapolation of the calibration is generally not valid in other cases with different geometry, sizes and even loading protocols. Most commercial software do not offer the features to explicitly modeling the bond slip. Numerical modeling of bond slip is proposed in this paper that can be conveniently implemented in a commercial software such as Seismostruct. Unlike the prior art, the slip parameter can be extracted using a semiempirical approach preceded by the generation of a numerical database. The proposed framework is also validated against the experimental results of one exterior and one interior beam–column joints. Sample illustration on an example building designed against the same seismic hazard level but following the recommendations per IS 13920, ACI 318 and EC8 is considered for monotonic (without bond slip) and cyclic (with bond slip) pushover analyses. Consideration of bond slip initiates early yielding and results in reduction of secant stiffness at the onset of yielding. The extent of influence depends on the compliance of design standards. For example, relatively higher percentage of reinforcement when designed per IS 13920 (as compared to ACI 318 and EC8) leads to a somewhat lower slip parameter resulting in lesser yield displacement and reduction of secant stiffness at the onset of yielding. [ABSTRACT FROM AUTHOR]

This study aims for a probabilistic assessment of active seismic control of structures in the presence of uncertainties of the structural model and the stochastic model of the ground acceleration. First, sensitivity analyses based on the Borgonovo sensitivity index are conducted to measure the effect of uncertainty sources on the maximum and root mean square (RMS) of the main structural responses in different seismic hazard regions. Then, the reliability analyses are conducted using Monte Carlo simulation (MCS) and importance sampling (IS) methods to the estimation of failure probabilities and reliability indices of the structures in different seismic hazard regions, force capacity of actuators, and seismic performance levels. Numerical studies carried out on a 10-story structure show that the uncertainties in peak ground acceleration (PGA) and story stiffness have the most effects on the seismic responses of the structure. The effect of the considered uncertainties is negligible on the maximum demand control force. The results also show that equipping the structure with an active control system results in a significant reduction in the failure probabilities of the structure. The target reliability index for the uncontrolled structure in life safety seismic performance level may not be satisfied in high and very high seismic hazard regions, it can however be easily dealt with, using the proposed technique, in the corresponding controlled structures. By increasing the control force capacity, an increment is observed in the reliability index. A high and suitable reliability index is given for both controlled and uncontrolled in the collapse prevention seismic performance level. [ABSTRACT FROM AUTHOR]

Many studies have reported that the seismic responses of slopes and retaining structures are notably different under the effect of multiple seismic waves. Previous experimental studies on slopes have commonly used one or several typical seismic records with different peak ground accelerations as the input, while ignoring the randomness of seismic ground motions. This study used shaking table tests to investigate the stochastic seismic responses of a slope reinforced by an anchored pile structure. First, a stochastic ground motion model was adopted to generate a suite of random ground motions, which were then used as the input of shaking table tests. Then, probabilistic methods, kernel density estimation and the probability density evolution method, were used to quantify the effect of earthquake uncertainty on the seismic responses of the system in terms of the mean, standard deviation, evolutionary characteristics of the probability density functions, and dynamic reliability. The stochastic seismic responses of the model under random excitation were investigated in terms of the acceleration response, amplification effect, and dynamic earth pressure. The results demonstrate that the seismic responses of a slope have marked variability under stochastic excitation. A more reliable assessment result can be obtained by using probabilistic methods to quantify the seismic response of the slopes. [ABSTRACT FROM AUTHOR]

This paper considers the uncertainty in the shear wave velocity (Vs) of soil and rock profiles for use in earthquake site response calculations. This uncertainty is an important contributor to uncertainty in site response, which in turn is an important contributor to uncertainty in earthquake ground motions and in seismic hazard. The paper begins with a discussion of the different types of uncertainty and how they are characterized in probabilistic seismic hazard analysis, and how this differentiation is particularly ambiguous in the case of soil properties. This is followed by a description of the probabilistic models of Vs that are most commonly used in engineering practice, for both generic and site-specific applications. In site-specific applications, the uncertainty in Vs (which is measured by the logarithmic standard deviation or by the coefficient of variation of Vs) is lower than in generic applications, but other elements of the profile model are also different. Next, the paper discusses the issues that arise in characterizing the uncertainty in Vs in site-specific applications using non-invasive surface wave methods and summarizes the insights obtained by comparing the results from multiple blind studies in which the same surface-wave data (and no other site-specific data) were provided to multiple teams of analysts. Finally, the paper provides recommendations on how to characterize uncertainty in Vs for both generic and site-specific applications. [ABSTRACT FROM AUTHOR]

Over the years, masonry structures have shown evidence of good behavior under vertical static loads; however, its characteristics make the use of this heterogeneous material unsuitable for buildings in seismic zones. Masonry building aggregates represent a common structural typology in many cities around the world. The present work addresses the seismic vulnerability assessment of an aggregate of mixed masonry-RC buildings in the region of Lisbon, which is characterized by moderate to high seismicity. Moreover, this typology was built before the enforcement of the first design code for building safety against earthquakes in Portugal (RSSCS). The numerical models were developed using the Applied Element Method (AEM) and calibrated based on experimental tests. The modeling technique applied was capable to identify the global and local failure mechanisms. A probabilistic approach allowed to compute the uncertainty in the seismic response, based on nonlinear static analyses. The site-specific ground motion was simulated using a non-stationary stochastic method. Subsequent fragility curves were derived, showing a significant probability that the structure will suffer moderate to extensive damage for a code compliant seismic assessment, corresponding to a 308-years return period and onshore seismic action. [ABSTRACT FROM AUTHOR]

The h-type anti-slide piles (hTPs) are extensively utilized in slope stabilization projects, yet their response to seismic activities remains inadequately understood. This study investigated the dynamic response of hTPs with circular cross-sections (hTCPs) through a shaking table test, focusing on seismic events along Jiuzhaigou-Mianyang highway slopes (ZK142 + 124 to ZK142 + 274). Time-frequency analysis using Fast Fourier Transform (FFT) and Hilbert-Huang Transform (HHT) was conducted. The peak acceleration and its direction, dynamic earth pressure and its sharing ratio, and moment were characterized, and the variations of pile displacement and the seismic damage on different parts of hTCPs were analyzed under varying loading conditions. Results reveal a distinct pressure distribution and damage characteristics between the long and short piles in hTCPs. A positive correlation between peak accelerations and loading conditions was observed in both long and short piles, with peak amplification occurring only at the top of long piles. Long piles exhibited diverse acceleration directions under different loading conditions, contrasting with the infrequent occurrence in short piles. The peak dynamic earth pressure distribution varied between the front and back side of pile bodies, with opposite overall trends between the long and short piles. The sharing ratio displayed an increasing followed by decreasing trend in long piles, but an opposite trend in short piles, with the turn point occurring at a loading condition of 0.3 g. These differences were significantly influenced by El Centro waves within a low frequency band (13.34 Hz–16.18 Hz), as a single large peak HHT energy spectrum was observed in long piles, but multiple and destructive low-frequency energy spectra in short piles. The results suggest an independent dynamic response occurred in the long and short piles of hTCPs during shaking table test, providing insights for their field engineering application in seismic active regions. • Potential damage was found through the dynamic earth pressure sharing ratio of piles. • Fourier spectra and pile displacement reveal damage modes. • Hilbert-Huang Transform spectra can pinpoint damage location of piles precisely. [ABSTRACT FROM AUTHOR]

This study explores comparative seismic performance of a shape memory alloy (SMA)-only device, a friction damper, and a hybrid self-centering device. The self-centering device considered in this study, named as superelastic friction dampers (SFDs), is a hybrid damper operating on a mechanism where SMA cables and frictional components are arranged in parallel. A detailed description of the device and an experimental characterization of mechanical behavior are presented first. Then, an 8-story archetype steel frame building is designed and modeled with each seismic protection device (SMA-only, hybrid self-centering, and friction only). To enable comparative performance assessment, each device is designed to have similar initial stiffness and the same maximum force at design displacement. Nonlinear time history analyses are conducted using a total of 44 ground motion records. The results are evaluated to compare performance of each frame design at design-basis and maximum considered earthquake hazard levels. Next, a risk-based seismic hazard demand analysis framework that involves comprehensive incremental dynamic analyses is employed for further assessing the performance of each system. The experimental results validate the parallel working mechanism of SMA cables and frictional components in the SFD, with 90% of the damper deformations recovered. Comparative analysis of seismic responses demonstrates the excellent performance of the SFDs in reducing interstory drift ratio, residual interstory drift ratio, and absolute acceleration responses. Furthermore, fragility analysis and risk-based seismic hazard assessment further reveal that the SFDs provide a well-balanced combination of energy dissipation capability and self-centering ability, thereby enhancing the seismic resilience of structures. • The working mechanism and mechanical performance of the superelastic friction damper have been experimentally validated. • Risk-based seismic hazard analyses have been conducted for frames equipped with various dampers. • SFD is capable of enhancing seismic resilience effectively by leveraging energy dissipation and self-centering capabilities. [ABSTRACT FROM AUTHOR]

This study focuses on developing probabilistic inelastic displacement ratio C R demand spectra for single-degree-of-freedom (SDOF) self-centering viscous damper (SC-VD) systems subjected to near-fault forward-directivity ground motions. In addition, this study presents a procedure for calculating the mean annual frequency (MAF) of the maximum inelastic displacement demand exceeding a specific displacement while considering the forward-directivity pulse effect to determine the maximum inelastic displacement demand hazard of the SC-VD structural system under near-fault forward-directivity ground motions. First, the effect of ground motion characteristics on C R demand is investigated. A probabilistic distribution model describing the probabilistic distribution of C R demand is then established. The effect of structural characteristics on key parameters in the probabilistic distribution of C R demand is investigated, and calculation models for key parameters are established. Based on the probabilistic distribution model and the calculation models for key parameters, the probabilistic C R demand spectra are developed. Finally, by combining the probabilistic C R demand spectra and the probabilistic seismic hazard analysis with the forward-directivity pulse effect, the procedure for calculating the MAF of the maximum inelastic displacement demand exceeding a specific displacement is presented to determine the maximum inelastic displacement demand hazard. The results indicate that the effects of ground motion characteristics should be treated as random variables, and that the Gamma distribution can reasonably describe the probabilistic distribution of C R demand. The proposed probabilistic C R demand spectra can reasonably estimate the actual C R demand, especially when R is large. Besides, the procedure for calculating the MAF of the maximum inelastic displacement demand exceeding a specific displacement is demonstrated to be effective in assessing the maximum inelastic displacement demand hazard through a set of SDOF SC-VD example systems. • A probabilistic distribution model of inelastic displacement C R demand is proposed. • The effect of structural characteristics on the probabilistic C R demand is studied. • A probabilistic C R demand spectrum under near-fault ground motions is developed. • A framework for calculating the inelastic displacement seismic hazard is proposed. [ABSTRACT FROM AUTHOR]

Tunnels, as critical underground infrastructures, often intersect with faults. Field investigations have underscored the susceptibility of fault-crossing tunnels to extensive damages during earthquakes. Hence, large-scale shaking table tests are conducted to investigate the deformation pattern and failure mechanism of fault-crossing tunnels under transverse excitation, particularly in non-rupture scenarios. The dynamic behavior of the tunnel, as expected, is dominated by the surrounding strata. Acceleration responses vary notably across different regions of the fault site. The disparity increases with the increments of seismic intensity and input frequency. The tunnel section at the interface between the fault and the hanging wall manifest the strongest acceleration, where the largest strains of the tunnel and most of the lining cracks also occur, highlighting its vulnerability to seismic vibrations. The damage-induced non-linearity of the tunnel is then identified by the decreasing dominant frequency thereof. The fault-crossing tunnel exhibits unique three-dimensional shearing-torsional deformations, elucidated through the test data and an analytical model. This deformation pattern provides a better understanding of the seismic responses of fault-crossing tunnels under seismic vibrations. • Dynamic responses of fault-crossing tunnels under seismic vibrations are studied by large-scale shaking table tests. • Faults have significant influence on tunnels under seismic vibrations even without rupture. • Vulnerable region of the tunnel, which is most intensely affected by the fault, is identified. • Deformation pattern and failure mechanism of fault-crossing tunnels under seismic vibrations are revealed. [ABSTRACT FROM AUTHOR]

Seismic fragility analysis is one probabilistic method that represents the conditional probabilities of exceeding different predetermined damage states for various given earthquake hazard levels, which is the essential part of probabilistic seismic risk assessment. It has gained much popularity recently because much more comprehensive and richer results than traditional probabilistic methods can be provided. The classical seismic fragility analysis of slopes is always performed through analytical approaches. In the present study, a novel seismic fragility analysis framework combined with shaking table model test results is proposed for probabilistic seismic performance and risk assessment of slopes. The shaking table model tests of a rock slope reinforced by pile-anchor structures were firstly performed subjected to a suite of real earthquake records with different intensity levels. Subsequently, the seismic responses from shaking table model tests were then gathered for the optimal analysis to determine the optimal engineering demand parameter (EDP) and earthquake intensity measure (IM) for seismic fragility analysis of slopes. At last, the identified most appropriate IM and EDP were selected to construct the scalar-valued fragility curves, vector-valued fragility surfaces and fragility surfaces considering acceleration elevation amplification effect by the proposed framework. The results indicate that using single IM to construct scalar-valued fragility functions may result in different failure probabilities depending on the chosen earthquake IM. The vector-valued fragility surfaces provide more information than ordinary fragility curves, and lead to more proper and realistic evaluations of seismic hazard of slopes. The methods and results presented in this paper also provide the basis for the probabilistic seismic risk and loss assessment of earthquake-induced slope geological disaster. • A novel seismic fragility analysis framework of slopes combined with the data from shaking table model tests is proposed. • The optimal EDP and earthquake IM for scalar- and vector-valued fragility analysis of slopes are identified. • The fragility surfaces of a slope considering acceleration elevation amplification effect are constructed. [ABSTRACT FROM AUTHOR]

Summary: Buildings may need large damping force under severe or near‐fault earthquakes, while existing friction dampers still need a high preload to provide enough reaction forces. In order to provide large damping forces at a small preload, this study proposes a new type of response‐amplified friction damper (RAFD) based on the amplification mechanism of a ball screw pair that combines the advantages of a friction damper and inerter device. The friction mechanism and the restoring force formula of the RAFD were derived theoretically, then pseudo‐static tests with various parameters were conducted. Finally, a single‐degree‐of‐freedom (SDOF) structure was employed to compare the effectiveness of the RAFD with a conventional friction damper under various earthquake levels. The results show that the RAFD has a significant friction amplification effect and significantly reduces the seismic responses of the SDOF structure. Particularly, the proposed RAFD with preload only 2 kN results in better effectiveness than the conventional friction damper with preload up to 20 kN. According to the pseudo‐static tests, the derived theoretical model can accurately describe the hysteresis behavior of the RAFD. A smaller gap in the RAFD can further improve the effectiveness in response mitigation. [ABSTRACT FROM AUTHOR]

This paper investigates the seismic response analysis of the 9-story SAC building equipped with pressurized sand dampers, a new type of low-cost energy dissipation device where the material enclosed within the damper housing is pressurized sand. The strength of the pressurized sand damper is proportional to the externally exerted pressure on the sand via prestressed steel rods; therefore, the energy dissipation characteristics of a given pressurized sand damper can be adjusted according to a specific application. The strong pinching behavior of pressurized sand dampers was characterized with a previously developed three-parameter Bouc-Wen hysteretic model that for this study was implemented in the open source code OpenSees with a C++ algorithm, and it was used to analyze the seismic response of the 9-story SAC building subjected to six strong ground motions that exceed the design response spectrum for all soil categories. The paper shows that for the family of strong ground motions used in this study, pressurized sand dampers with strength of the order of 5%–10% of the weights of their corresponding floors were able to keep the interstory drifts of the 9-story SAC building at or below 1%, while base shears and peak plastic hinge rotations were reduced in the damped configuration. Supplemental damping produced mixed results on floor accelerations; nevertheless, in most floors, peak accelerations were reduced. [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]

This study proposes a class of hybrid isolation systems constructed by combining Buckling Restrained Braces (BRBs) with Rubber Bearings (RBs) or Lead Rubber Bearings (LRBs) for mitigating the seismic responses in bearing-supported bridges under strong earthquakes. Firstly, two different hybrid isolation systems (RB–BRB and LRB–BRB) were preliminarily designed based on the energy-conservation concept in the case of a bridge with Y-shaped piers, which can meet all the energy demands at different seismic hazard levels. Further, seismic evaluations were conducted on the bridges with the LRB, RB–BRB, and LRB–BRB isolation systems based on the nonlinear time history analyses. The proposed hybrid isolation systems show a two-phase energy dissipation behavior, which facilitates the systems to reduce the seismic responses remarkably under different earthquake scenarios and achieve most of the performance objectives corresponding to the code-specified hazard levels. Finally, based on fragility analyses, the effects of the gap spacing and the stiffness ratio of the BRB to the pier were investigated with respect to the failure probability in the case of a bridge with LRB–BRB. It has been validated that the seismic performances of this study's bridge can be improved considerably with the optimized gap spacing and BRB stiffness. [ABSTRACT FROM AUTHOR]