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The NGA-Subduction Project is a multi-year, multidisciplinary project with the goal of developing a ground motion database and ground motion models for global subduction zone earthquakes including those in Japan, Taiwan, Cascadia, Alaska, New Zealand, South America, and CentralAmerica. Our ground motion model development is currently at the stage of identifying regional trends in path terms. We use a combination of data inspection and regression techniques to distinguish path effects in the data, including differences between interface and inslab events, forearc/back-arc effects, regional effects, and azimuthal effects. Our approach to modeldevelopment is to first develop a path model capturing these effects, then to investigate source and site effects. The parameterization of functional form is guided in part by the scaling expected by a generic equivalent point-source stochastic model. We expect regionalization in path and will investigate further regionalization in site response and in overall model bias.

Earthquakes begin with abrupt shifts along the faults. These movements release seismic waves that propagate through the Earth, shaking the ground as a result of the stored “elastic strain” energy being released. Property loss and human deaths occur due to improper design of structures under the earthquake loading conditions. It is observed that Peninsular India witnessed steady-to-serious earthquakes in the last 50 years. Amaravati is the prospective capital city of Andhra Pradesh State, which is situated on the Coromandel Coast of Peninsular India. The upcoming capital city, Amaravati, requires an earthquake hazard analysis because important engineering structures and infrastructure systems will be constructed in the near future. In this study, a probabilistic approach is used to assess the earthquake hazard for Amaravati City (latitudes: 16∘24′36′′–16∘35′24′′N and longitudes: 80∘24′25′′–80∘36′18′′E), India. The seismic risks of Amaravati City presented in terms of the configuration of ground motion parameters, peak ground acceleration (PGA), and spectral response acceleration (Sa) at 0.05s and 1s for 2% and 10% Risks of Exceedance in 50 years, are produced. The uncertainties involved in seismic risk prediction are accounted for by selecting different attenuation relations developed for globally shallow crustal intraplate earthquakes with a logic tree approach. Additionally, the seismic risk values are disaggregated for Amaravati City (16∘31′37′′N and 80∘29′46′′E) to understand the individual contributions of seismic sources in terms of earthquake magnitude and site distance. The uniform hazard spectra are developed for the important places of the Amaravati Capital City and are compared with the Indian seismic code [IS 1893 (Part 1): Criteria for earthquake-resistant design of structures — Part 1: General provisions and buildings] for the rocky site. It is found that the estimated PGA values for Amaravati City are higher than the values recommended by IS 1893 (Part 1) for the rocky site. The results of this study will be very helpful for the composition of earthquake-resistant infrastructures in Amaravati City. [ABSTRACT FROM AUTHOR]

Velocity pulse with strong energy input is the significant feature of near-fault ground motions. Bridges close to or passing across seismic faults may suffer from higher failure risk, which is inseparable from the influence of velocity pulse. This study aims to evaluate the nonlinear response characteristics of bridge structures under various near-fault ground motion conditions. A typical isolated continuous girder bridge is adopted, and two corresponding finite element models, i.e., considering and ignoring the heating effect of lead core bearings (LRBs), are established based on the OpenSees platform. Then, a total of 40 near-fault ground motion records are selected, and the pulses are extracted. Both the energy-based and deformation-based seismic responses are captured and compared to reveal the differences for the isolated bridge subjected to the original waves and the extracted pulses. The results highlight that the accuracy of the seismic evaluation based on the extracted pulses strongly depends on the precondition that the pulse period is close to the fundamental period of the isolated bridge. Hence, inputting the extracted pulses for predicting the in-elastic seismic response of isolated bridges locating at near-fault region is not an adequate replacement for those original waves of near-fault ground motions. In addition, the heating effect of LRBs will be magnified for the seismic response of isolated bridges subjected to the extracted pulses, and it will mainly affect the seismic responses of bearings and piers, i.e., the former increases and the latter decreases. [ABSTRACT FROM AUTHOR]

As a contribution to step 3 of the ESG6 blind prediction exercise, we present an application of two different, purely empirical approaches to estimate the strong ground motion at a soft site ("KUMA") from the observed ground motion at a reference rock site ("SEVO") for the two largest shocks of the Kumamoto 2016 sequence. The two methods estimate the non-linear transfer function between a reference rock and a sedimentary site by modifying the linear transfer function derived from weak motion recordings. The modification is based either on a machine learning tool based on a wide collection of Japanese weak and strong motion recordings and the associated site metadata (method 1), or on an estimate of a site-specific parameter related to an average non-linear site response (method 2). The acceleration time series are then derived at the sedimentary site of interest using an estimation of the time delay between wave arrivals at the rock and site stations, and a minimum phase assumption for the site transfer function. These predictions were made blindly, but after the ESG6 conference they could be compared both with the actual ground motion recorded at KUMA during the two shocks, and the average and range of all other predictions preformed for this benchmark. Both of these purely empirical methods provide an honorable prediction of usual engineering ground motion parameters of the two target events. The performance of these two purely empirical approaches is at least comparable to those of the numerical simulation methods for the foreshock—if not better—and slightly worse for the (largest) mainshock. As the methods required only recordings of weak motions at the target and a referent sites and very simple description of the soil profile. The use of moderate motions to constrain the frequency shift prediction for the second method and the consideration of an alternative phase modification are possible ways to improvement. [ABSTRACT FROM AUTHOR]

Summary: Acceleration measurements are often used for model updating of civil engineering structures, especially in the case of seismic monitoring. It is yet unclear if accelerations alone would generate an accurate and robust finite‐element (FE) model. This study examines this notion and analyzes the possibility of using other vibration monitoring data for model updating of shear‐wall tall buildings. This study compares the accuracy and robustness of the FE models being optimized via accelerations, roof displacement, wall rotations, interstory drift ratios, and the linear combination of these measurements. A numerical case study is analyzed using Timoshenko beams for modeling the lateral vibration of a benchmark 42‐story building under seismic excitations. Results show that the acceleration response of the examined building is mostly governed by its higher vibration modes. Depending on the characteristics of ground motions, using accelerations alone may generate an FE model biased towards higher‐order modes without effectively capturing the lower‐order modes. For instance, the first modal frequency of the updated FE model could be 12.0% lower than the true value, and the reconstructed displacement and rotation responses are noticeably inaccurate. Employing multi‐source monitoring data for model updating, for example, the combinations of roof displacement and acceleration measurements, could reduce the normalized root‐mean‐square errors in displacements by more than 70%. This study also quantifies the robustness of the FE model under various measurement noise levels and 50 pairs of earthquake records. Finally, the effects of multi‐source data on FE model updating are validated via experiments on a 7‐story shear wall building. Analysis reveals that a more accurate and robust FE model can be determined via a combination of accelerations and top displacement than via acceleration alone. [ABSTRACT FROM AUTHOR]

Summary: Near‐field ground motions with fling‐step and forward‐directivity characteristics contain large‐amplitude pulses in velocity history, causing severe damage to stilted buildings in mountainous areas. In this study, three groups of 20 near‐field ground motions with fling‐step and forward‐directivity characteristics and 10 far‐field ground motions were selected as seismic inputs. Nonlinear response history analysis (NLRHA) was performed on plane finite element models of two seven‐story stilted frame structures, one with steel braces in the stilted story and the other without steel braces in the slope direction. Structural seismic response obtained from NLRHA was discussed in terms of inter‐story drift ratio (IDR) and peak floor acceleration (PFA). In addition, damage to two structures was assessed using the modified Park–Huang damage model. The results show that stilted structures exhibit greater inter‐story ratios and damage index values under near‐field ground motions with fling‐step characteristics and forward‐directivity characteristics than far‐field ground motions, where the stilted story has the highest amplification ratio in both IDR and damage index among floors. Designers should pay sufficient attention to the influence of ground motions with fling‐step and forward‐directivity characteristics on seismic demands and damage to stilted structures. The peak inter‐story ratio and damage index of stilted structures with steel braces were significantly lower than that of stilted structures without braces, proving the validation of setting steel braces on reducing the seismic demands of stilted structures and improving structural seismic safety. Additional NLRHA performed using artificial pulses shows that the seismic response of stilted buildings is related to pulse periods of near‐field ground motions and the greatest seismic demands and damage are obtained when the pulse period is 1.5–1.6 times the fundamental period of the stilted building. [ABSTRACT FROM AUTHOR]

The mechanical performance of curved bridges under the action of an earthquake is complex. To obtain the influence of seismic parameters on the seismic response of curved girder bridges, this paper relies on a large slope small-radius curved steel box girder bridge (LSCGB) and selects seismic wave incidence angle, vertical component of ground motion, and site category as seismic parameters to carry out nonlinear time history analysis. Based on the analysis results of the case bridge, it is shown that the torsional vibration of the first 10 modes of LSCGB is significant, the modes are dispersed, and the contribution of high-order modes of vibration cannot be ignored. The most unfavorable seismic wave incidence angle is in the direction of 45°∼60° counterclockwise Angle from the central connection line of Pier No. 1 and Pier No. 4 of the bridge. The seismic response of the curved bridge components increases with the vertical seismic intensity, and the influence on displacement responses is more significant. The basic vibration period of curved girder bridges built on soft soil sites is extended by approximately 18.23%, and the seismic response of key components increases with the softening of the site soil. Therefore, when analyzing the seismic response of LSCGBs, the influence of vertical component of ground motion and site category should not be ignored. [ABSTRACT FROM AUTHOR]

This study provided a comprehensive understanding of the source process of the 1819 M 7.7 Kachchh Indian earthquake using physics‐based dynamic rupture modeling and strong ground motion simulations. We successfully simulated the spontaneous dynamic rupture along a curved non‐planar fault using the 3‐D curved‐grid finite‐difference method (CGFDM). The estimated earthquake magnitude is around 7.6, consistent with previous estimations. Our simulations accurately replicated macroscopic rupture patterns and surface deformation, showing agreement with observed data along the Allah Bund fault (ABF) with a maximum displacement ∼5.5 m at the Earth's surface. The maximum modeled coseismic slip on the fault was approximately 7.5 m. Notably, the ABF exhibited characteristics of a weak barrier (leaky barrier) at the bending part, allowing the rupture to propagate further. Despite limitations in surface deformation calculations, the modeled values aligned with the trend of surface fault slip, with a slight deviation in the epicenter toward the east compared to earlier studies. We observed a homogeneous principal stress oriented N25°E, consistent with the present day Indian plate motion. The estimated horizontal peak ground velocities (PGVh) and the maximum value of Intensity X+ aligns well with observations. Furthermore, conducting thorough case studies on significant earthquakes and potential seismic scenarios in stable continental regions is crucial. Such studies play a vital role in validating and improving dynamic rupture models. When combined with statistical methods, this research holds great promise for advancing seismic hazard assessments, earthquake engineering, and strategies for disaster management. Plain Language Summary: This paper is centered around the simulation of the dynamic rupture of the 1819 M 7.7 Kachchh earthquake in India. We have successfully replicated the earthquake's behavior using a three‐dimensional simulation method. The study's results demonstrate the significant influence of the local tectonic setting and non‐planar fault structure on earthquake generation and rupture progression. Although slight discrepancies exist between the simulation results and actual observations, the simulations capture significant trends and reproduce macroscopic rupture patterns. The estimated magnitude of the earthquake aligns well with previous studies. The study highlights the role of fault bending and its impact on surface deformation, contributing to a better understanding of seismic hazards and providing insights for seismic hazard assessments and earthquake source characterization. This work is valuable for comprehending earthquake sources, particularly from earthquake perspectives in the SCR region and other areas. Key Points: Dynamic rupture simulations of the 1819 Kachchh M 7.7 earthquake replicate co‐seismic fault slip, enhance our knowledge of the earthquake sourceWeak barrier characteristics observed at the bending part of the fault enabled further rupturing, influenced by SH and the nucleation pointContributes to understanding earthquake hazards, enhancing seismic assessment, engineering, and disaster management strategies [ABSTRACT FROM AUTHOR]

Topography can strongly affect ground motion, and studies of the quantification of hill surfaces' topographic effect are relatively rare. In this paper, a new quantitative seismic topographic effect prediction method based upon the BP neural network algorithm and three-dimensional finite element method (FEM) was developed. The FEM simulation results were compared with seismic records and the results show that the PGA and response spectra have a tendency to increase with increasing elevation, but the correlation between PGA amplification factors and slope is not obvious for low hills. New BP neural network models were established for the prediction of amplification factors of PGA and response spectra. Two kinds of input variables' combinations which are convenient to achieve are proposed in this paper for the prediction of amplification factors of PGA and response spectra, respectively. The absolute values of prediction errors can be mostly within 0.1 for PGA amplification factors, and they can be mostly within 0.2 for response spectra's amplification factors. One input variables' combination can achieve better prediction performance while the other one has better expandability of the predictive region. Particularly, the BP models only employ one hidden layer with about a hundred nodes, which makes it efficient for training. [ABSTRACT FROM AUTHOR]

On 5 September 2022, a Ms 6.8 earthquake struck Luding County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China. This seismic event triggered over 16,000 landslides and caused serious casualties and infrastructure damages. The aim of this study is to perform the detailed landslides susceptibility mapping associated with this event based on an updated landslide inventory and logistic regression (LR) modeling. Firstly, we quantitatively assessed the importance of different controlling factors using the Jackknife and single-variable methods for modeling landslide occurrence. Subsequently, four landslide susceptibility assessment models were developed based on the LR model, and we evaluated the accuracy of the landslide susceptibility mappings using Receiver Operating Characteristic (ROC) curves and statistical measures. The results show that ground motion has the greatest influence on landslides in the entire study area, followed by elevation, while distance to rivers and topographic relief have little influence on the distribution of landslides. Compared to the NEE plate, PGA has a greater impact on landslides in the SWW plate. Moreover, the AUC value of the SWW plate significantly decreases for lithological types and aspect, indicating a more pronounced lithological control over landslides in the SWW plate. We attribute this phenomenon primarily to the occurrence of numerous landslides in Permian basalt and tuff in the SWW plate. Otherwise, the susceptibility results based on four models indicate that high-susceptibility areas predicted by different models are distributed along both sides of seismogenic faults and the Dadu Rivers. Landslide data have a significant impact on the model prediction results, and the model prediction accuracy based on the landslide data of the SWW plate is higher. [ABSTRACT FROM AUTHOR]

In the absence of records of near-fault ground strains and rotations from strong earthquakes, deterministic physics-based simulations have become an important tool for characterizing these motions in the low-frequency range (e.g., < 1.0 Hz). Building on a previous study of near-fault ground strains and rotations from actual strike-slip ruptures conducted by the authors, this article investigates the spatial and temporal characteristics of such motions generated by actual earthquakes with predominantly dip-slip mechanisms. This is achieved by performing forward ground-motion simulations of the 1994 Mw 6.7 Northridge, the 1989 Mw 6.9 Loma Prieta, and the 1985 Mw 8.1 Michoacan earthquakes using previously published finite-fault rupture models. For each considered seismic event, time histories of ground strains and rotations are generated at near-fault recording stations and at a dense grid of observation points. This is accomplished by finite differencing translational motions simulated at very closely spaced stations using a kinematic modeling approach. The simulation results show large-amplitude axial strain, shear strain, and rocking in the near-fault region. For the considered earthquakes, the maximum peak ground strain over all grid points is of the order of ~ 100–250 μstrain, whereas the maximum peak ground rocking ranges from ~ 100 to ~ 200 μrad. The attenuation characteristics of peak ground strains and rotations differ for the considered seismic events and depend on the component of interest and the rupture distance. Finally, peak ground rocking can be reasonably estimated from peak vertical ground velocity using a properly selected scaling factor despite the significant variability of the latter in the near-fault region. Filtering out the very low frequencies of ground motion (< 0.1 Hz), including the static offset, significantly affects the scaling factor. [ABSTRACT FROM AUTHOR]

The March 20, 2014, magnitude Mw3.9 earthquake near Arzew, Algeria, instigated a study to deepen comprehension of seismic activity and hazard in the region. Analyzing data from Algerian and Spanish seismic networks, we explored earthquake characteristics and rupture mechanisms. The earthquake's epicenter was located at 35.825° latitude and -0.366° longitude, with a depth of 7 km, exhibiting intensity IV-V in the Arzew-Oran area. Preceding this event, a magnitude MD3.1 foreshock occurred on February 1, 2014, at the same location. The waveforms of the foreshock and mainshock exhibited striking similarities, validating the effectiveness of the Empirical Green's Function method employed for deconvolution. Through waveform inversion and P-wave polarities, we estimated the focal mechanism, revealing a near-pure strike-slip mechanism with nodal planes oriented ~E-W and ~N-S. The rupture process, characterized by multiple episodes, propagated predominantly from the south towards the N5°-15°E direction at a velocity around 2.7 km/s along an 870 m fault length in 0.32 seconds. The mainshock's fault plane was identified as the N-S plane, indicating the direction of rupture propagation. Source parameter estimation utilizing the EGF method revealed larger corner frequencies and stress drops compared to individual spectra estimation, attributed to the method's improved correction for attenuation and site effects, without the need for simplified a priori models. Despite its low magnitude, the 2014 Arzew earthquake provided valuable insights into the region's seismic behavior, contributing significantly to ground motion predictions. In particular, the study highlights the necessity of accounting for rupture directivity in seismic hazard assessments and mitigation strategies. [ABSTRACT FROM AUTHOR]

SUMMARY: The amplitude, frequency and polarization of ground motion at the surface can be affected by the local geology. While low-velocity sediments and fill can amplify ground motions in certain frequency ranges, the low velocities found in fault zones can also produce prominent wavelets. In this paper, we provide further evidence that polarization of ground motion can be affected by the geological fabric in fault zones that have sustained significant brittle deformation. Aside from the well-known effect of fault-trapped waves in the low-velocity zone with polarization azimuths parallel to the fault strike, the effect of stiffness anisotropy was recently recognized with polarization azimuths at high-angle to the fault strike and orthogonal to the locally predominant fracture field in the fault damage zone. To clarify further such features, we investigate directional amplification effects across the San Jacinto fault zone in Southern California using seismic data recorded by permanent seismic stations and dense across-fault arrays. We observe three main polarization trends. The first trend parallel to the fault strike is ascribed to fault-trapped waves along the low-velocity zone, in agreement with several studies in the last decade in the same region. The second and third trends are orthogonal to the orientation of R and T Riedel planes, respectively. They are related to the stiffness anisotropy in densely fractured rocks in the damage zone, which are more compliant orthogonal to their fractures. At some locations the two effects are superimposed, occurring in different and distinct frequency ranges. Directional amplification at rock sites can be important for expected ground motion and seismic hazard. However, in seismic engineering the current prescriptions of seismic codes do not account for amplification effects at rock sites at frequencies of engineering interest. [ABSTRACT FROM AUTHOR]

SUMMARY: Geophysics and Geotechnical Engineering commonly use 1-D wave propagation analysis, simplifying complex scenarios by assuming flat and homogeneous soil layers, vertical seismic wave propagation and negligible pore water pressure effects (total stress analysis). These assumptions are commonly used in practice, providing the basis for applications like analysing site responses to earthquakes and characterizing soil properties through inversion processes. These processes involve various in situ tests to estimate the subsurface soil's material profile, providing insights into its behaviour during seismic events. This study seeks to address the limitations inherent to 1-D analyses by using 3-D physics-based simulations to replicate in situ tests performed in the Argostoli basin, Greece. Active and passive source surveys are simulated, and their results are used to determine material properties at specific locations, using standard geophysical methods. Our findings underscore the potential of 3-D simulations to explore different scenarios, considering different survey configurations, source types and array sets. [ABSTRACT FROM AUTHOR]

SUMMARY: Microseismic monitoring is an important technique to obtain detailed knowledge of in-situ fracture size and orientation during stimulation to maximize fluid flow throughout the rock volume and optimize production. Furthermore, considering that the frequency of earthquake magnitudes empirically follows a power law (i.e. Gutenberg–Richter), the accuracy of microseismic event magnitude distributions is potentially crucial for seismic risk management. In this study, we analyse microseismicity observed during four hydraulic fracture treatments of the legacy Cotton Valley experiment in 1997 at the Carthage gas field of East Texas, where fractures were activated at the base of the sand-shale Upper Cotton Valley formation. We perform waveform cross-correlation to detect similar event clusters, measure relative amplitude from aligned waveform pairs with a principal component analysis, then measure precise relative magnitudes. The new magnitudes significantly reduce the deviations between magnitude differences and relative amplitudes of event pairs. This subsequently reduces the magnitude differences between clusters located at different depths. Reduction in magnitude differences between clusters suggests that some attenuation-related biases could be effectively mitigated with relative magnitude measurements. The maximum likelihood method is applied to understand the magnitude frequency distributions and quantify the seismogenic index of the clusters. Statistical analyses with new magnitudes suggest that fractures that are more favourably oriented for shear failure have lower b-value and higher seismogenic index, suggesting higher potential for relatively larger earthquakes, rather than fractures subparallel to maximum horizontal principal stress orientation. [ABSTRACT FROM AUTHOR]

Selecting or generating ground motions (GMs) that elicit seismic responses matching specific standards or expected benchmarks for nonlinear time‐history analysis (NLTHA) is crucial for ensuring the rationality of structural seismic design and analysis. Typical GM inputs for NLTHA, either natural or artificial, are normally spectrum‐compatible, which may produce significant variations in analysis results, even using multiple GMs. This paper introduces a response‐compatible ground motion generation (RCGMG) method for generating GMs that are tailored to be response‐compatible. NLTHA results using only a few of these artificial GMs can closely approximate the mean responses from a large set of natural spectrum‐compatible GMs or target responses. The RCGMG method adopts the response diagram in the time domain (RDTD) to characterize the nonstationary features of GMs and their impacts on structural dynamic responses. A physics‐guided conditional generative adversarial network is developed to produce artificial RDTDs with features and impacts of RDTDs of natural GMs. These generated RDTDs are then mapped into response‐compatible GMs through a feedforward neural network. To verify the effectiveness of RCGMG, NLTHA of different structure models under various site conditions and target spectra is conducted. Seismic responses of NLTHA using RCGMG‐generated GMs are compared with responses from spectrum‐compatible natural GMs. The results demonstrate that responses from RCGMG GMs are closer to the target responses, with fewer GM inputs and robust generalization performance. [ABSTRACT FROM AUTHOR]

Velocity response spectrum (SV) plays a critical role in the seismic design of structures equipped with velocity-dependent dampers. Often, the SV is approximated using the pseudo-velocity response spectrum (PSV), because of the lack of information on the SV in seismic codes. As indicated in the existing literature, the error of this approximation is significant for short and long periods, and therefore, researchers have started to develop PSV to SV conversion models for obtaining SV more accurately. Recent studies discovered that the relationship between the PSV and SV is affected not only by structural parameters, but also by magnitude, distance, and site class. However, models for converting PSV to SV including magnitude, distance, and site class as input parameters have not been developed. To this end, a PSV to SV conversion model including magnitude, distance, and site class is proposed in this study based on a large number of real ground motion records (16,660 horizontal acceleration time histories) selected from the Japan Strong Motion Network. Furthermore, since the magnitude and distance are not specified in the seismic design, a response-spectrum-shape factor, s, is discussed to reflect the influences of magnitude and distance. Accordingly, an SV/PSV model incorporating s is established. The proposed models show better accuracy than the existing models for cases with different magnitudes, distances, and site classes. [ABSTRACT FROM AUTHOR]

This study proposes a new algorithm based on the smoothed Significant Velocity Half-Cycles for efficient and accurate identification of pulse-like velocity ground motions. The empirical-mode decomposition (EMD) based algorithm is initially employed with providing some valuable insights into its failure. Next, a concept of riding waves is presented and two additional criteria are established. The proposed algorithm is demonstrated to successfully exclude the ambiguous records with insignificant pulse characteristics when compared with six benchmark identification methods. This article also provides a dataset of 325 strong pulse-like records identified from the NGA-West2 database, which is practical importance in earthquake engineering field. [ABSTRACT FROM AUTHOR]

Numerical studies on freestanding structures typically leverage the Distinct Element Method where the response is dictated by joints; however, the response carries significant uncertainty due to joint stiffness parameters. This study aims to quantify the influence of joint stiffness parameters on the global response of freestanding structures subjected to seismic excitation in a probabilistic formulation. By using a range of joint stiffness values with rectangular rigid blocks of different aspect ratios, the impact of joint stiffness parameters is evaluated against a large suite of historical ground motions. Results indicate that increasing contact stiffness results in increased stability against overturning. [ABSTRACT FROM AUTHOR]

The objective of this study is to explore the seismic fragility of reinforced concrete bridges, specifically in response to the vertical components of ground motions, utilizing fragility surfaces. The examination of bridge responses involves the application of optimally selected intensity measures through three-dimensional nonlinear time-history analyses, encompassing uncertainties in both superstructure materials and soil–structure interaction effects. In this investigation, an extended Probabilistic Seismic Demand Model (e-PSDM) is employed, leveraging fragility surfaces to concurrently consider vertical and horizontal excitations. The results obtained from this approach are compared with traditional fragility curves. This study emphasizes Pile-cap displacement and drift ratio as pivotal engineering damage parameters, acknowledging their sensitivity to the influences of both soil–structure interaction effects and vertical ground motion. The fragility surfaces derived from the study reveal a correlation between increased vertical spectral accelerations and elevated probabilities of surpassing both slight damage and collapse limit states. These observations underscore the critical significance and practical utility of fragility surfaces in the context of performance-based seismic assessment and design for reinforced concrete bridges. The findings from this research contribute valuable insights into the nuanced behaviour of reinforced concrete bridges under seismic conditions, emphasizing the relevance of incorporating vertical components in fragility assessments for a more comprehensive understanding of structural vulnerability. [ABSTRACT FROM AUTHOR]

In this study, we utilize two metaheuristic algorithms, particle swarm optimization, and biogeography-based optimization, to select and scale ground motion (GM) records for use in the time history analysis of structures. This method ensures that there is no alteration to the phase or shape of the response spectra of the records. The proposed methodology demonstrates an ability to search through hundreds of earthquake records and propose a combination of 11 record pairs and scaling factors, resulting in a mean spectrum that aligns with the target spectrum. We applied the proposed research to two sites in separate geographical regions in the United States: Memphis and San Francisco, and we followed the ASCE 7-22 procedure. Selected ground motions underwent scaling adjustments represented by scalar values in a user-defined range. Furthermore, we present error metrics, comparing the target spectrum with the mean spectrum derived from the selected records. To showcase the effectiveness of our approach, we conducted a comparative analysis against results obtained from PEER-NGA methodology. The outcomes show that the methodology can be viewed as an effective and reliable approach for obtaining appropriate GM records for the time history analysis of structures. [ABSTRACT FROM AUTHOR]

This study investigated the seismic performance and self-centering behavior of a three-story steel frame equipped with self-centering brace (SCBs) using pseudodynamic tests aided by OpenSees version 2.5.7 and OpenFresco version 2.7.0. The three-story self-centering braced frame (SCBF) was simplified to a three-story shear building model, and a generic experimental element with three nodes with horizontal degrees of freedom was used to establish a two-dimensional (2D) numerical model. The input ground motions were scaled to a service level earthquake (SLE), design basis earthquake (DBE), maximum considered earthquake (MCE), and a very rare earthquake (VRE) with 63%, 10%, 2%, and 0.5% probability of exceedance in 50 years, respectively. The test results demonstrated the excellent seismic performance and self-centering behavior of the SCBF. The maximum story drift ratio and maximum residual story drift ratio of the SCBF under a VRE were 1.91% and 0.119%, respectively, below the thresholds of 2.0% and 0.5%. The SCBs provided more than 90% of the initial lateral stiffness of the SCBF and dissipated approximately 55% of the seismic input energy. The seismic performance of the SCBF satisfied the no-damage criterion under an SLE and DBE. Although the columns in Story 1 yielded under an MCE and VRE, no visible residual deformation of the column flanges was detected in Story 1 after the tests. In addition, the maximum residual drift ratio of Story 1 was only 0.066%. Therefore, the columns in Story 1 only required simple and quick reinforcements before being usable. Unexpected factors, such as the fit-up tolerances around the pins, out-of-sync activation of the SCBs in the same story, residual deformation of the SCBs, and the out-of-sync activation of the two groups of disc springs in the same SCB, did not affect the seismic performance and self-centering capacity of the SCBF. [ABSTRACT FROM AUTHOR]

This study quantitatively evaluated the level of conservatism or accuracy of four typical directions used to assess the maximum structural response over all nonredundant seismic input angles: fault-normal and fault-parallel (FN and FP), the direct maximum direction (MD), the maximum peak ground velocity (PGV) direction, and the principal axes directions. Two eight-story models of symmetric and asymmetric buildings were developed, and two ensembles of ground motion records were selected considering three varying ground motion intensities. Bidirectional nonlinear response-history analyses (RHAs) were performed by rotating each pair of ground motion horizontal components to 26 orientations, from 0° to 170° in increments of 10° as well as four critical and their orthogonal directions. The effect of rotating the ground motions on several engineering demand parameters (EDPs) was investigated and the seismic demands in four critical directions were compared and evaluated deterministically and probabilistically. The four critical directions were re-evaluated by considering the largest response between two orthogonal pairs. The results show that the response in the maximum PGV direction is very close or equal to the maximum value over all orientations, especially for high levels of ground motion intensities, and thus is recommended for ground motion selection in performance-based seismic design and assessment. In addition, the influence of rotation angle is effectively reduced when using the larger seismic response value of the two orthogonal pairs while maintaining the same number of RHAs. [ABSTRACT FROM AUTHOR]

Following the 2016 Chauk earthquake in Bagan (Myanmar), numerous old pagodas and temples suffered severe damage. This research presents a study on the seismic hazard analysis of the Bagan city in Myanmar, based on a probabilistic framework focussing on analysing 43 temples with their associated local soil information. To this end, two seismic source models are developed based on the tectonic setting of the region and information available. Instrumental and historical records are compiled from both literature and international earthquake catalogues while conducting catalogue completeness. This study uses state-of-the-art ground motion models to perform probabilistic seismic hazard analysis and develop seismic hazard maps for different return periods in the region. Results are also expressed for selected temples in the region in terms of site-specific uniform hazard spectra. The findings indicate significant seismic activity, with peak ground acceleration in the region ranging from 0.25 to 0.36 g for a return period of 2475 years, 0.22–0.32 g for a return period of 975 years, and 0.18–0.24 g for a return period of 475 years. The updated hazard levels indicate that the literature slightly underestimates hazard in the region under study. [ABSTRACT FROM AUTHOR]

In past, several ground motion prediction models (GMMs) were developed in Himalayan region. However, there is no comprehensive review available for the developed GMMs. In order to fill the gap, in the present study an attempt has been made to review the existing GMMs for Himalayan region. The study focuses on the seismotectonic setting of the region, source of seismic data, GMMs used for conducting hazard analysis of different locations and various developed GMMs by several researchers. Further, applicability of these generated GMMs was inspected thoroughly using available seismic records of Indo-Himalayan region. For this purpose, predicted peak ground acceleration (PGA) and peak spectral acceleration (PSA) obtained by using the GMMs for different magnitudes and distances are compared with recorded data by computing root mean square error (RMSE) and Chi-square value. Moreover, log-likelihood (LLH) scoring method has been applied and proper weights of the GMMs have been proposed. [ABSTRACT FROM AUTHOR]

Tiered geosynthetic-reinforced soil (GRS) retaining walls are becoming increasingly popular in earthquake-prone areas due to their excellent earthquake resistance. Typically, near-field strong ground motion is characterized by a significant vertical component and/or a long-period velocity pulse. However, this is seldom considered in the current design of tiered GRS walls. In this study, two centrifuge shaking table tests were conducted to investigate the earthquake performance of tiered GRS walls under bidirectional and pulse-like excitations. The results revealed that under bidirectional excitation, the wall model underwent significant deformation. The confining pressures in the soil increased due to vertical motion, resulting in notable changes in the shear modulus of the backfill. Due to large differential settlement and vertical excitation, the earth pressures were significantly impacted. In the second case, pulse-like motions induced considerable shear strains in the backfill, leading to significant alterations of the shear modulus and dynamic damping of the structure. The facing exhibited distinct deformation modes, with some sliding at the toe. The peak wall displacement and reinforcement strain were both notably higher than the residual values. However, in both cases, the connections between the reinforcements and the facing endured relatively large strains, and need to be considered in seismic design. • Seismic behavior of tiered GRS walls under near-field ground motions were tested. • The effect of vertical seismic motions on tiered walls is discussed. • Specific seismic response of tiered walls under pulse-like excitations is examined. [ABSTRACT FROM AUTHOR]

Accurate seismic ground response analysis is crucial for the design and safety of civil infrastructure and establishing effective mitigation measures against seismic risks and hazards. This is a complex process due to the nonlinear soil properties and complicated underground geometries. As a simplified approach, the one-dimensional wave propagation model, which assumes that seismic waves travel vertically through a horizontally layered medium, is widely adopted for its reasonable performance in many practical applications. This study explores the potential of sequence deep learning models, specifically 1D convolutional neural networks (1D-CNNs), long short-term memory (LSTM) networks, and transformers, as an alternative for seismic ground response modeling. Utilizing ground motion data from the Kiban Kyoshin Network (KiK-net), we train these models to predict ground surface acceleration response spectra based on bedrock motions. The performance of the data-driven models is compared with the conventional equivalent-linear analysis model, SHAKE2000. The results demonstrate that the deep learning models outperform the physics-based model across various sites, with the transformer model exhibiting the smallest average prediction error due to its ability to capture long-range dependencies. The 1D-CNN model also shows a promising performance, albeit with occasional higher errors than the other models. All the data-driven models exhibit efficient computation times of less than 0.4 s for estimation. These findings highlight the potential of sequence deep learning approaches for seismic ground response modeling. [ABSTRACT FROM AUTHOR]

In relation to its rapid infrastructure expansion, exemplified by projects like the Najran Valley Dam or the rehabilitation of agricultural terraces, Saudi Arabia stands out among the Arabian Gulf nations. To mitigate the earthquake-related risks effectively, it is imperative to conduct an exhaustive analysis of its natural hazards. The southwesternmost region of Saudi Arabia is the main subject area of this study for the probabilistic seismic hazard assessment (PSHA), which aims to identify the peak ground acceleration (PGA) and spectral acceleration (SA) values. The investigation encompasses a 10% and 5% probability of occurrence over a 50-year exposure time for both B/C and C NEHRP soils. In order to take into account the earthquake activity that takes place in the vicinity of the Red Sea Rift, which in fact may have an impact on the seismic hazard in this active tectonic region, different seismic source zones were especially designed for this evaluation. Various characteristics such as the uncertainties related to the b-value, the expected maximum magnitude, and different ground motion prediction equations (GMPEs) were integrated using a logic tree scheme. Additionally, regression relationships between the computed ground motion values were established, and a novel design response spectrum was developed and recommended for several cities. Regarding the key findings, it is significant to highlight that the seismic hazard decreases towards the northeast, when moving away from the Red Sea Rift, confirming anticipated trends where proximity to the rift corresponds to increased seismic hazard. Notably, cities such as Farasan Island, Jazan, Al Qunfundhah, Al Lith and Al Birk present the highest observed hazard values among all the cities analyzed. For these cities, the obtained maximum SA values for both 475 and 975 years under B/C site conditions are as follows: 0.268 g and 0.412 g, 0.121 g and 0.167 g, 0.099 g and 0.150 g, 0.083 g and 0.135 g, and 0.066 g and 0.118 g, respectively. These results emphasize the crucial necessity of adequately evaluating and thoroughly updating the seismic hazard inherent to these particular areas to enhance the risk reduction and disaster readiness initiatives. [ABSTRACT FROM AUTHOR]

The occurrence of a series of earthquakes of different magnitudes or multiple mainshocks has been reported recently. This leads to the liquefaction of sand due to excess pore pressure generation under undrained loading conditions, which alters the stable structure of the soil to an unstable form. The response of saturated sandy deposits under these conditions is rarely experimented by researchers and the present study highlights this issue. Here six shake table test results are analyzed to understand the initiation of liquefaction in the sand at varying base accelerations (0.15 g, 0.2 g and 0.3 g) at continuous and series of identical shaking events. Multiple shaking events were provided to simulate earthquakes at closely spaced time intervals. The surface settlements and response of excess pore water pressure at various depths within a saturated sand bed due to these shaking events are investigated. The results showed that the soil layer near the surface of the soil is most likely to be liquefied. Also, the re-liquefaction resistance of the sand remains constant for the first few shakings, but the dissipation time of excess pore water pressure decreases with increasing density. [ABSTRACT FROM AUTHOR]

One effective technique for mitigating the earthquake-induced liquefaction potential is the installation of stone columns. The permeability coefficients of stone columns are high enough to cause a high seepage velocity or expedited drainage. Under such conditions, the fluid flow law in porous media is not linear. Nevertheless, this nonlinear behavior in stone columns has not been evaluated in dynamic numerical analyses. This study proposes a dynamic finite element method that integrates nonlinear fluid flow law to evaluate the response of liquefiable ground improved by stone columns during seismic events. The impact of non-Darcy flow on the excess pore pressure and stress path compared to conventional Darcy law has been investigated numerically in stone columns. Furthermore, the effects of different permeability coefficients and stone column depths have been studied under near and far field strong ground motions. The results indicate that the non-Darcy flow increases the excess pore water pressure as high as 100% in comparison to the Darcy flow. [ABSTRACT FROM AUTHOR]

Ancient timber structures have a high cost for conducting dynamic time-history response analysis due to the presence of many nonlinear components, such as mortise-tenon joints and Dou-Gon. To enhance the efficiency of evaluating the seismic performance of ancient timber structures through dynamic analysis, a simplified dynamic response analysis method based on SPO2IDA was adopted to evaluate the seismic performance of a timber frame palace with nine-purlin in Qing Dynasty of China and the results were compared with those obtained using the traditional pushover analysis method. The results showed that there were only slight differences in the seismic response of the ancient timber structure determined by the two methods when the structure was in a nonlinear stage. During a Ⅸ degree rare earthquake, the displacement response differed by 0.004 m, while the median seismic intensity during the third level of damage limit state differed by 0.079 g. The traditional pushover analysis method may underestimate the seismic resistance of the ancient timber structure, but the SPO2IDA algorithm can better capture the uncertainty of the structural vulnerability model at different limit stages caused by ground motion input, achieving the goal of quickly evaluating the seismic performance of the ancient timber structure with acceptable accuracy. [ABSTRACT FROM AUTHOR]

Reliability‐based design optimization (RBDO) traditionally relies primarily on high‐fidelity and computationally expensive simulations to search for and evaluate design solutions. However, significant disparities could emerge for complex nonlinear behavior that are challenging for numerical modeling. In contrast to mitigating the impact of inaccurate numerical modeling through optimization algorithms, laboratory experiments realistically capture the complex nonlinear behavior of structures or their components. Real‐time hybrid simulation (RTHS) is widely considered as an efficient and cost‐effective technique for integrating numerical modeling with experimental testing for structural response evaluation. This study proposes an innovative framework that utilizes RTHS for the performance assessment of candidate designs to enable RBDO of structures subjected to pulse‐like ground motions. RTHS tests are conducted to physically evaluate structural responses through realistically replicating complex nonlinear behavior of experimental substructures. This study introduces a novel penalty function‐based efficient global optimization (P‐EGO) method to minimize the required number of laboratory tests through surrogating the response quantities of interest derived from RTHS. The proposed framework is experimentally evaluated for design optimization of a two‐story four‐bay steel moment‐resisting frame with self‐centering viscous dampers subjected to pulse‐like ground motions. The results demonstrate innovative application of RTHS in dynamic optimal design to account for uncertainties. It offers an effective and efficient alternative for traditional RBDO through pure computational simulation, particularly when structural components pose challenges for numerical modeling. [ABSTRACT FROM AUTHOR]

Strong earthquake disasters can cause noticeable damage correlations among regional buildings with similar mechanical properties, termed structure‐to‐structure seismic damage correlation, which has a pronounced impact on the regional seismic risk assessment and therefore needs to be properly quantified. This study first introduces a time‐domain analytical and equivalent frequency‐domain analysis based on random vibration theory for calculating structure‐to‐structure seismic damage correlation coefficients. Subsequently, by employing the spatially consistent white noise excitation and the spatially varying white noise excitation with the Luco–Wong coherence function, the structural filtering effect and the ground motion spatial correlation effect are progressively incorporated, and an analytical interstructural damage correlation model incorporating structural dynamic properties and spatial distance is derived. Comparations with Monte Carlo simulations and existing empirical models demonstrate that the proposed analytical model possesses a clear physical basis and high reliability. Finally, a case study was conducted on a district having 29,461 buildings in Shanghai, China to illustrate the influence of interstructural damage correlation on the regional seismic risk. Results show that disregarding the interstructural seismic damage correlation can lead to underestimation of overall loss uncertainty. [ABSTRACT FROM AUTHOR]

Prediction of the soil seismic response is of primary importance for geotechnical earthquake engineering. Conventional physics‐based models such as the finite element method (FEM) often face challenges due to inherent model assumptions and uncertainties of model parameters. Furthermore, these physics‐based models require significant computational resources, particularly when simulating seismic responses across numerous soil sites. In this study, a multi‐ input integrative neural network is developed for predicting soil seismic response based on the recorded data from a large number of downhole array sites. Ground motions, seismic event information, and wave velocity structures of the sites are utilized as input data in the proposed neural network, enabling the model to adapt to various site conditions. Comparative assessments against state‐of‐the‐art FEM models demonstrate that the proposed models exhibit superior prediction performance with increased efficiency. Furthermore, the pre‐training technique, a transfer learning method, is employed to predict the seismic response at new stations. By fine‐tuning the pre‐trained model derived from the extensive dataset with limited recorded data from new stations, high‐precision seismic response predictions can be realized, illustrating the adaptability and efficacy of the proposed approach in data‐scarce conditions. [ABSTRACT FROM AUTHOR]

A novel, practical, and computationally efficient probabilistic methodology for the stochastic generation of suites of fully non‐stationary artificial accelerograms is presented. The proposed methodology ensures that the produced ground motion suites match a given target spectral mean and target variability for the whole period range of interest. This is achieved by first producing an ensemble of random target spectra with the given mean and variability and then using them to generate artificial, target spectrum‐compatible, acceleration time‐histories with spectral representation techniques. Spectral correlation can also be assumed for the generated ground motion spectra. Based on the same backbone, two different formulations are proposed for generating spectrum‐compatible acceleration time‐histories of the non‐stationary kind. The distinction between these two variants lies in the techniques employed for modeling the temporal and spectral modulation, focusing on the site‐compatibility of the produced records. The first approach uses past‐recorded seismic accelerograms as seed records, and the second proposes and uses a new, probabilistic time‐frequency modulating function. The outcome of the proposed methodology is suites containing site‐compatible ground motion time‐histories whose spectral mean and variability match those obtained from any of the usually employed target spectra used in the earthquake engineering practice. An online tool implementing the proposed methodology is also freely provided. [ABSTRACT FROM AUTHOR]

This study presents the experimental results on a scaled bridge model with a newly proposed unidirectional rocking isolation bearing system (referred to as Uni‐RIBS) on a shaking table. The bridge model features one superstructure girder and four bearings. The experimental input encompassed a variety of recorded, design, and harmonic ground motions, characterized by differing peak accelerations, with or without vertical components, and time‐scaled attributes. The superstructure girder's mass was altered for two conditions (full and half). The test results validate the rocking mechanism inherent in the Uni‐RIBS and demonstrate the analytical model's accuracy in predicting the system's dynamics, including its negative stiffness, mass‐independent, and energy dissipation characteristics during bearing rotation reversals. Additionally, this study examines the effectiveness of a simplified numerical model in varying complexities for predicting the seismic responses of the bridge model. [ABSTRACT FROM AUTHOR]

Synthetic ground motions (GMs) play a fundamental role in both deterministic and probabilistic seismic engineering assessments. This paper shows that the family of filtered and modulated white noise stochastic GM models overlooks a key parameter—the high‐pass filter's corner frequency, fc$f_c$. In the simulated motions, this causes significant distortions in the long‐period range of the linear‐response spectra and in the linear‐response spectral correlations. To address this, we incorporate fc$f_c$ as an explicitly fitted parameter in a site‐based stochastic model. We optimize fc$f_c$ by individually matching the long‐period linear‐response spectrum (i.e., Sa(T)$Sa(T)$ for T≥1s$T \ge 1\,{\rm {s}}$) of synthetic GMs with that of each recorded GM. We show that by fitting fc$f_c$ the resulting stochastically simulated GMs can precisely capture the spectral amplitudes, variability (i.e., variances of log(Sa(T))$\log (Sa(T))$), and the correlation structure (i.e., correlation of log(Sa(T))$\log (Sa(T))$ between distinct periods T1$T_1$ and T2$T_2$) of recorded GMs. To quantify the impact of fc$f_c$, a sensitivity analysis is conducted through linear regression. This regression relates the logarithmic linear‐response spectrum (log(Sa(T))$\log (Sa(T))$) to 7 GM parameters, including the optimized fc$f_c$. The results indicate that the variance of fc$f_c$ observed in natural GMs, along with its correlation with the other GM parameters, accounts for 26% of the spectral variability in long periods. Neglecting either the fc$f_c$ variance or fc$f_c$ correlation typically results in an important overestimation of the linear‐response spectral correlation. [ABSTRACT FROM AUTHOR]

Local soil conditions play a crucial role in shaping ground surface responses and impacting the intensity of ground shaking. In this study, the influence of different site profiles on computed ground motion was investigated using a 2D equivalent linear analysis approach. Four distinct site profiles: sand, clay, sand-clay-sand-clay, and clay-sand-clay-sand profiles were considered. The results were presented using multiple metrics, including surface acceleration, displacement, modulus decreasing ratio, and coherence analysis. Notably, the clay profile significantly influenced ground motion, while the sand profile exhibited relatively lower seismic activity. This suggests that softer sites significantly influence ground motion, leading to potentially high levels of shaking. [ABSTRACT FROM AUTHOR]

This study is focused on an evaluation of the correlation between the soil conditions and the seismic damage observed after the Vrancea March 4, 1977 intermediate-depth earthquake in Craiova, Romania. A significant number of existing studies in the literature have focused on the evaluation of damage for Bucharest, but the effects of the 1977 earthquake in Craiova have been very rarely discussed and presented. Craiova was the second city in Romania after Bucharest in terms of building damage and casualties as a result of the 1977 Vrancea seismic event, even though it is situated at a considerable distance (more than 250 km) from the epicenter. The 1977 event affected old low-rise masonry structures located in the central part of the city, as well as low-rise unreinforced masonry structures built after 1950. The soil conditions are evaluated based on a recently compiled collection of geological, geotechnical, and ground motion data from the study area. No correlation between the earthquake observed damage andthe number of standard penetration test (SPT) blows at a depth of 6 m or the soil layer at a depth of 3 m can be inferred from the available data. Moreover, the analyses show practically no influence of the terrain slope on the ground motion amplitudes for Craiova, which is situated on the left bank of Jiu River. The vulnerability characteristics of unreinforced masonry structures from Craiova and other cities are also evaluated in this study. The relative frequencies of unreinforced masonry structures having increased damage degrees is significantly larger for the Iasi and Craiova data sets. Finally, an estimation of the peak ground accelerations in four cities in Romania is evaluated based on the damage of unreinforced masonry structures. [ABSTRACT FROM AUTHOR]

Acceptable seismic performance, ease and low cost in design and implementation are advantages of passive dampers, but fixed performance parameters corresponding to the type and amount of input energy reduce their efficiency. In this research, a new two-level passive damper in rigid connections with variable stiffness, strength, and energy absorption capacity is introduced and its seismic performance in 5, 10, and 15-story steel frames is evaluated with nonlinear dynamic analysis using SAP2000 software. The results show that, despite the different dynamic parameters in the selected seismic records, such as the frequency content and duration of ground motions, the performance of the structures under all earthquakes has improved significantly, which confirms the effectiveness of the proposed damper in rigid connections on improving the seismic performance structures. Besides, results prove the proposed damper effectiveness on decreasing the structural response such as maximum displacement and base shear. The average displacements reduced by 61%, 51% and 16% compared to those of BSEEP-4ES connections for the 5, 10 and 15-story frames, respectively. Besides, maximum base shear forces reduced by average of 29% and 15% compared to those of BSEEP-4ES connections for the 5 and 10-story frames, respectively. [ABSTRACT FROM AUTHOR]

Before the anticipated Nankai Trough earthquake, the effects of multiple cascading hazards on bridge performance and the associated functionalities of road networks must be assessed to develop recovery strategies. This paper presents a framework for assessing the probabilistic connectivity of road networks exposed to both ground motion and tsunami, considering the spatial correlations among hazard intensities. To evaluate the joint probabilities of bridge states (i.e., passable and impassable states) and the probabilistic connectivity of road networks, the total probability theorem was used to integrate spatially correlated seismic and tsunami hazard assessments into the fragility estimates that consider the cascading effects of ground motion and tsunami-induced damages to bridges. For illustrative purposes, the probabilistic connectivity of hypothetical road networks in Japan that could be affected by both ground motion and tsunami during the anticipated Nankai Trough earthquake was assessed using the proposed method. The results showed that seismic retrofitting of bridges located along the route where the probability of impassable states due to tsunami is very low can enhance the probabilistic connectivity of entire road networks. [ABSTRACT FROM AUTHOR]

Segmental tunnel is widely adopted in the urban transportation system, thereby its seismic resilience is a cornerstone for resilient cities. The segmental tunnel is an assembly of reinforced concrete segments, bolts, gaskets, gaps, etc., and exhibits highly nonlinear behavior when subjected to external loadings. Yet, in practice, its seismic response is generally estimated via a holistic modeling approach where the segmental tunnel is represented by a homogeneous beam or shell element with equivalent stiffness. Here, a multi-contact joint-based model is developed for a segmental tunnel, incorporating the nonlinearities embedded in the assembly with acceptable computational costs. The reinforced concrete segment is represented as the displacement-based fiber beam element, whereas the complex interaction among the configurations of the joint, i.e. bolt, gasket, and contacting concrete, is modeled via the zero-length section element. The proposed model’s accuracy is validated via a series of experimental data under three loading scenarios. A sensitivity analysis demonstrates that the mechanical response of segmental tunnels highly relies on the assembly configurations. The proposed model is implemented to investigate the seismic response of a typical segmental tunnel under various ground motions, demonstrating its applicability in seismic safety assessments, particularly in capturing the nonlinear response of segmental tunnels under high-intensity earthquakes. [ABSTRACT FROM AUTHOR]

Ground surface deformations can be observed during the coseismic and postseismic periods. The accurate determination of displacements is of paramount importance for the assessment of the destructive power of large earthquakes and the characterization of fault behaviors. Therefore, we employ the sub-daily Global Positioning System (GPS) solutions at 19 GPS stations to determine the coseismic and postseismic deformations of the 2010 moment magnitude (Mw) 8.8 Maule earthquake. Using sub-daily GPS data, we can accurately measure both coseismic and early postseismic deformation signals, which can precisely identify the distribution of coseismic slip and the spatiotemporal evolution of early afterslip within the first 36 h. In particular, the sub-daily solution can provide more accurate and quicker results, nearly 10% smaller than those with the daily solution. Furthermore, there is significant ground motion in the immediate postseismic period, which decreases rapidly thereafter. The largest postseismic deformation observed during the first 2 h occurred at station CONZ and amounted to 3.6 cm. During the immediate postseismic period of the 2010 Maule earthquake, afterslip is the dominant mechanism, while poroelasticity plays a negligible role within the first 36 h. Meanwhile, early aftershocks tend to occur in the boundary and the inner part of the afterslip, indicating that the afterslip has the potential to drive the occurrence of aftershocks in the initial stages of postseismic activity. [ABSTRACT FROM AUTHOR]

Regional seismic fragility assessment of bridge portfolios must address the embedded uncertainties and variations stemming from both the earthquake hazard and bridge attributes (e.g., geometry, material, design detail). To achieve bridge‐specific fragility assessment, multivariate probabilistic seismic demand models (PSDM) have recently been developed that use both the ground motion intensity measure and bridge parameters as inputs. However, explicitly utilizing bridge parameters as inputs requires numerous nonlinear response history analyses (NRHAs). In this situation, the associated computational cost increases exponentially for high‐fidelity bridge models with complex component connectivity and sophisticated material constitutive laws. Moreover, it remains unclear how many analyses are sufficient for the response data and the resulting demand model to cover the entire solution space without overfitting. To deal with these issues, this study integrates Gaussian process regression (GPR) and active learning (AL) into a multistep workflow to achieve efficient regional seismic fragility assessment of bridge portfolios. The GPR relaxes the probability distribution assumptions made in typical cloud analysis‐based PSDMs to enable heteroskedastic nonparametric seismic demand modeling. The AL leverages the varying standard deviation to select the least but most representative bridge‐model‐ground‐motion sample pairs to conduct NRHA with much‐improved efficiency. Both independent and correlated multi‐output GPRs are proposed to deal with bridge portfolios with seismic demand correlations among multiple components (column, bearing, shear key, abutment, unseating, and joint seal). Considering a single benchmark highway bridge class in California as the case study, the AL‐GPR framework and the associated component‐level fragility results are investigated in terms of their efficiency, accuracy, and robustness. The fragility results show that 70 AL‐selected samples would enable the GPR to derive bridge‐specific fragility models comparable to the ones using the multiple stripes analysis approach with 1950 ground motions considered for each individual bridge. The AL‐GPR model also successfully captures the physics of how bridge span length, deck area, column slenderness, and steel reinforcement ratio would change the damage state exceedance probabilities of different bridge components. The efficiency of AL stems from the fact that, with the multi‐output independent GPR, a stable and reliable fragility model can be achieved using 50 AL‐selected samples compared to at least 270 randomly chosen samples. The proposed methodology advances the state of the art in enabling more efficient and reliable regional seismic fragility assessment of multi‐component bridge portfolios. [ABSTRACT FROM AUTHOR]

One‐dimensional site response analysis (1D SRA) remains the standard practice in considering the effect of local soil deposits and predicting site‐specific ground motions, although its range of applicability to realistic seismic wavefields is still in question. In this 1D approach, horizontal and vertical ground shaking are assumed to be induced by vertically propagating shear and compressional waves, respectively. A recent study based on analytical two‐dimensional (2D) plane waves and simple point source earthquake simulations has shown two mechanistic limitations in this 1D modelling technique for general inclined seismic waves, that is, systematic over‐prediction of the vertical motion and wave trapping in the 1D soil column. In this article, we evaluate in detail the applicability of this 1D modelling approach to realistic three‐dimensional (3D) simulated seismic wavefields in shallow sedimentary basins. Linear‐viscoelastic 1D SRA predictions using two types of input motions that are commonly used in practice—rock outcrop and in‐column motions, are compared with the reference true site response results from 3D earthquake simulations in terms of various measures in the frequency and time domain. It is shown that the horizontal motion in the 3D seismic wavefield exhibits dominant shear wave propagation phenomenon, while the vertical motion is a combined effect of compressional and shear waves and can be over‐predicted by the 1D approach when the incident seismic waves are inclined. Direct evidence of the wave refraction process that leads to the vertical motion over‐prediction is provided. 1D SRA with in‐column inputs can yield motions that have significantly longer duration compared to the true 3D site response solution due to trapped waves, casting in doubt the frequent need for increased soil damping in existing site studies to compensate for wave attenuation due to scattering alone. Sensitivity investigation on the increase of soil profile damping by a multiplier Dmul shows Dmul values compatible with those found in the literature for both horizontal and vertical motions. It is shown that the level of Dmul optimized for a best match of the spectral acceleration is dependent on the characteristic of the input motion and a larger Dmul is typically required for the vertical component. In contrast, 1D SRA with outcrop motions predicts motions with shorter significant duration due to its inability to capture the basin‐edge generated surface waves. A suite of ground motion simulations was performed to assess the sensitivity of the observations to the basin geologic structure including the velocity gradient, rock‐basin impedance contrast and basin depth. The analysis results show that the accuracy of the simplified 1D procedure is dependent on the wavefield composition of both the input motions and the true 3D site response solution. While the horizontal motions in shallow sedimentary basins can, to the first order, be reasonably captured by the simplified 1D approach, 1D SRA for the vertical component is in general not reliable and contributions from inclined shear waves should be accounted for in site‐specific evaluation of the vertical design ground motion. [ABSTRACT FROM AUTHOR]

In this paper the results of 2D dynamic finite element analyses of a zoned earth dam are presented and discussed with the aim of detecting proper intensity measures able to describe the variation of the crest permanent settlement with the characteristics of the input ground motion. A large set of horizontal components of earthquake records has been selected and used as input motion considering both upstream and downstream directions. This allowed to explore the activation of plastic mechanisms in the dam embankment and the amplification of the horizontal accelerations. Starting from the analysis results, two original intensity measures, related to the amplitude, energy and frequency content of the input motion, have been detected and original empirical predictive formulas have also been derived to estimate the permanent crest settlement of the dam. The effectiveness of the proposed intensity measures and the reliability of the novel relationships between these intensity measures and earthquake‐induced permanent crest settlements have been checked against (i) numerical results of further dynamic analyses carried out for the same dam using additional sets of input motions, (ii) numerical results available in the literature for two other earth dams and (iii) field data relative to the crest settlements induced in four earth dams by two recent large earthquakes. The whole set of analysis results allowed defining an empirical equation that appears as a promising general predictive tool for the earthquake‐induced crest settlement of earth dams. [ABSTRACT FROM AUTHOR]

Multi-axial real-time hybrid simulation (ma-RTHS) utilizes multiple loading devices to realize boundary control with multiple degrees of freedom (MDOF), thus being capable of handling complex dynamic scenarios and multidimensional problems. In this paper, a new control technique was developed by using a parallel configuration of double shaking tables to implement shear force and bending moment at the boundary between substructures. The dynamic forces are combined by inertia forces of controlled mass driven by electromagnetic shaking tables. The two shaking tables are packaged as a boundary-coordinating device (BCD). An enhanced three-variable control (ETVC) was proposed to consider the coupling effect between two shaking tables and incorporated with the adaptive time series (ATS) compensator to improve the synchronization of the two shaking tables. The proposed control method was verified by three rounds of hybrid tests on a four-story steel shear frame using different ground motions. Nine criteria were utilized to evaluate the performance of RTHS including both tracking performance and global performance indexes. It was proved that RTHS was successfully implemented, and the boundary forces were well-tracked by the proposed control strategy. Good tracking performance was achieved to prove the effectiveness of the strategy. [ABSTRACT FROM AUTHOR]

In order to study the effect of the velocity pulse on the dynamic response of the train-bridge system of the high-speed railway simple supported beam bridge, the velocity pulse is simulated by the trigonometric function method and superimposed with the far-field earthquake without pulse to synthesize the pulse with different pulse types, pulse periods and pulse peaks. A 10 × 32m typical high-speed railway simple supported beam bridge is considered an case illustrating study. Then, the dynamic response of train-track-bridge coupling system is calculated by train-track-bridge seismic analysis software TTBSAS. Afterwards, the influence of pulse near-field earthquakes parameters and vertical components on dynamic response of train-bridge system and the safety of the train on the bridge are discussed in detail.The new derailment evaluation index is adopted to evaluate driving safety under earthquakes. The train safety control of simply supported beam bridge under the action of near-field earthquake is studied. The results show that the impact of pulse ground motion on the dynamic response of the train-track-bridge coupling system is significantly higher than that of no-pulse ground motion, especially the impact on the bridge and rail subsystem is more significant than that of train subsystem. Under the excitation of ground motion intensity of 0.05g ∼ 0.15g, the safe speed threshold of pulse near-field ground motion is smaller than that of far-field ground motion. When the ground motion intensity is 0.20g ∼ 0.30g, the safe speed threshold of pulse near-field ground motion and far field ground motion is 200km/h. So, the pulse near-field earthquake poses a greater threat to the safety of the train on the bridge than the far-field earthquake. Therefore, the influence of pulse near-field earthquakes should be considered in the seismic design. The research results of this paper can provide theoretitcal support for the design of a high-speed railway bridge in the near-field area. [ABSTRACT FROM AUTHOR]

This study investigates the seismic behavior of long-span prestressed concrete box-girder bridges subjected to long-duration (LD) ground motions and spectrally equivalent near-fault (NF) and far-fault (FF) short-duration ground motions. For this purpose, the Kömürhan and Gülburnu Highway Bridges built with the balanced cantilever method using prestressed concrete box-girder were selected. This paper consists of two main sections. First, ambient vibration tests were conducted to identify the modal parameters of the bridges and calibrate the finite element models. Second, using three ground motion sets consisting of 42 acceleration records applied to the orthogonal and vertical directions of the bridges, the structural responses were evaluated and compared. In order to determine the type of ground motion that is critical for this type of bridge, these sets consist of 14 long-duration ground motions, 14 spectrally equivalent near-fault short-duration ground records, and 14 spectrally equivalent far-fault short-duration records. The comparison parameters considered for this study were displacements and internal forces in the piers and decks. The results strive to highlight the extent to which the duration and characteristics of the ground motion sets affect the structural behavior. Results indicate that the mean deck displacements of selected bridges obtained from FF short-duration records were nearly 10.70% and 7.44% less than those obtained from the LD and NF short-duration ground motions. These trends were also observed in the bridge piers. Moreover, increases of up to 17.54% and 26.65% in the mean shear forces of the piers under LD and NF short-duration ground motions were observed compared to those determined from the FF short-duration counterparts. Similar trends were observed in the bending moment values. It was also observed that far-fault short-duration records may have substantial consequences on such structures. [ABSTRACT FROM AUTHOR]