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With the development of performance-based seismic design, the residual displacements of structures have become a key factor in determining the post-earthquake functionality and post-earthquake repair cost. However, the factors affecting the residual displacement responses of the RC structure and the corresponding influence laws have not been uniformly understood. This paper systematically investigates the influence of structural properties and ground motion characteristics on the residual displacements of the RC bridge columns, especially the near-fault pulsed ground motion characteristics. To this end, the ultimate quasi-static residual displacement and the dynamic residual displacement are first defined and introduced. Then, Bouc–Wen models and the finite element models of RC columns are selected as target models, and quasi-static analyses and dynamic time history analyses of the two models are performed to obtain the residual displacement responses. The results show that the structural properties and ground motion characteristics significantly affect the residual displacement responses of the RC bridge columns. The influence laws of structural properties on residual displacement responses of different models obtained by using different analysis methods are inconsistent, and it is also differences in the influence laws when using different residual displacement indexes. Furthermore, the residual displacement responses of the RC columns subjected to near-fault pulsed ground motions are larger compared with ground motions without pulses, and they increase with the increasing of the pulse period. The symmetrical pulsed ground motions result in higher residual displacement demands compared with antisymmetric pulsed ground motions. [ABSTRACT FROM AUTHOR]

In order to develop the direct normalized inelastic displacement spectrum rather than the inelastic displacement ratio or reduction factor that is suitable for self-centering structures when subjected to near-fault pulse-like (NFPL) ground motions, the nonlinear time history analysis for a single degree of freedom (SDOF) system with a generalized flag-shaped (FS) hysteretic model is realized using Matlab software. A total of 85 NFPL records are arranged as the seismic input, the inherent viscous damping ratio, ξ, is respectively determined as 0.02 and 0.05 for typical steel and concrete structures, the variation range of all considered parameters, including the ductility, the vibration period, the energy dissipation coefficient and the post-yield stiffness ratio of the hysteretic model is specified, then the constant-ductility inelastic displacement spectra for different seismic records and different model parameters are calculated and statistically studied. It is found the normalization of the natural period and the displacement by the pulse period, namely T/Tp and xm/Tp2, can significantly reduce the variation of displacement spectra. The influence of the post-yield stiffness ratio ranging from 0 to 0.20 on the normalized spectra is slight and can be neglected. Besides, as T/Tp increases, the normalized displacement first increases and then slowly decreases, the normalized period corresponding to the peak displacement is approximately 1. When T/Tp is about less than 0.7, the displacement spectra are positively correlated with the ductility, μ, followed by a negative correlation between them as T/Tp grows larger. Moreover, increasing the energy dissipation coefficient will reduce the displacement response, but when the coefficient is greater than 1, its impact on the displacement is rather small. Finally, the equation of the normalized displacement spectra as a function of T/Tp and μ is proposed, in which an adjustment factor, Ωβ, is added to account for the influence of the energy dissipation coefficient on the displacement spectra. [ABSTRACT FROM AUTHOR]

The present study aims to analyze the correlation between ground motion parameters and energy demands of low-rise RC buildings without shear walls. Two regular 4- and 7-story residential buildings were seismically designed to represent low-rise RC buildings. In order to establish the requirements of single degree of freedom (SDOF) systems as well as multi degree of freedom (MDOF) systems, the dynamic features of "equivalent" SDOF systems were defined by using MDOF systems. The correlation of 20 ground motion parameters (GMPs) of 44 records with the energy demands obtained from a total of 176 nonlinear time history analyses was examined for the SDOF and MDOF systems within the scope of this study. The ground motion parameters (GMPs) were taken as intensity measures (IMs). In contrast, maximum input energy was used as a demand measure (DM) and these energy values were normalized with the masses of the buildings for cases, where the buildings were evaluated together. Parameters related to acceleration and velocity are generally found to yield better results in comparison to the ones related to frequency and displacement. Velocity Spectrum Intensity (VSI) and Arias Intensity (Ia) were obtained to have the highest correlation values as a single parameter. This study suggested new equations by combining multiple ground motion parameters for SDOF and MDOF systems to better reflect damage potential than a single parameter. The use of multiple parameters in combination results in better correlation coefficients. [ABSTRACT FROM AUTHOR]

Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2 × 10–4. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings. [ABSTRACT FROM AUTHOR]

The regional seismic risk assessment plays an important role in the disaster prevention and mitigation. The accurate time-history analysis for a region provides an important data base for regional seismic risk assessment. However, an accurate calculation method is limited, then, its accuracy still lacks validation. Meanwhile, there is also a lack of risk assessment methods and indicators applicable to the regional accurate time-history analysis, both of which hinder the seismic risk assessment. In this paper, a regional-scale time history analysis-driven method is proposed for the quantitative evaluation of regional seismic damage risk and verified with a real earthquake damage survey. First, the regional time history analysis method is introduced, including the automatic modeling, response calculating, result analysis and 3-D visualization modules. Second, a calculation method for seismic damage degrees (DD) of buildings is introduced. Subsequently, the probabilistic models of each DD under the ground motions with a specific intensity are calculated based on regional-scale nonlinear time history analysis. Next, the concept of the three-level seismic damage risk is offered, then a determining workflow of seismic damage risks is proposed based on the code-abiding three-level design requirement. Afterward, the regional seismic damage index is suggested for the quantitative evaluation of earthquake-induced damage risk. Finally, the actual seismic damage database of 192 buildings in epicenter of Ludian Earthquake is established through on-site investigations, then used to verify the regional simulation's accuracy. Consequently, it could be an aid to accurately present seismic damage distribution assessments and effectively develop seismic risk mitigation strategies. [ABSTRACT FROM AUTHOR]

This paper investigates the inelastic displacement ratios (IDRs) and displacement ductility demands of a wide range of single-degree-of-freedom (SDOF) systems subjected to pulse-like ground motions (GMs) of the 2023 Pazarcık (Kahramanmaraş) earthquake. A set of twenty-seven GMs characterized as pulse-like are utilized in the study. As-recorded velocity time histories of horizontal components are rotated over 90° at a step of 1° to attain the waveform with the largest peak ground velocity (PGV) over all horizontal orientations. Inelastic displacement ratio and displacement ductility spectra are computed through nonlinear response history analysis (RHA). Local amplifications of both spectra are observed at some periods. The results of this study show that large inelastic displacement and ductility demands are imposed on certain reinforced concrete (RC) structures. Finally, predictive models of the mean inelastic displacement ratio and mean ductility demand spectra (DDS) are developed based on the Gauss–Newton algorithm (GNA). The model provides a strong correlation between the computed and the estimated data, and sufficient convergence criteria. The results of this study collectively emphasize the necessity of integrating pulse-like GMs into future revisions of earthquake codes. [ABSTRACT FROM AUTHOR]

This study presents a neural network-based model for predicting linear quadratic regulator (LQR) weighting matrices for achieving a target response reduction. Based on the expected weighting matrices, the LQR algorithm is used to determine the various responses of the structure. The responses are determined by numerically analyzing the governing equation of motion using the state-space approach. For training a neural network, four input parameters are considered: the time history of the ground motion, the percentage reduction in lateral displacement, lateral velocity, and lateral acceleration, Output parameters are LQR weighting matrices. To study the effectiveness of an LQR-based neural network (LQRNN), the actual percentage reduction in the responses obtained from using LQRNN is compared with the target percentage reductions. Furthermore, to investigate the efficacy of an active control system using LQRNN, the controlled responses of a system are compared to the corresponding uncontrolled responses. The trained neural network effectively predicts weighting parameters that can provide a percentage reduction in displacement, velocity, and acceleration close to the target percentage reduction. Based on the simulation study, it can be concluded that significant response reductions are observed in the active-controlled system using LQRNN. Moreover, the LQRNN algorithm can replace conventional LQR control with the use of an active control system. [ABSTRACT FROM AUTHOR]

This study focuses on evaluating the performance of an aged heritage building made of unreinforced brick masonry under seismic conditions, both with and without retrofitting. To achieve this, an experimental examination was conducted using a scaled-down model of a single-story unreinforced building, constructed on a shake table at a 1:4 geometric scale. The responses of this model were recorded at the roof level, primarily in the form of displacements. Subsequently, the same scaled model was replicated in SAP2000 finite element (FE) software. The results obtained from the FE model closely matched the experimental findings, validating the computational approach. Following this validation, an existing masonry heritage school building situated at Aligarh Muslim University, Aligarh, was chosen for further investigation. In this subsequent analysis, natural frequencies and mode shapes were computed through model analysis, revealing closely spaced natural frequencies. To assess the seismic performance of the heritage building, a nonlinear time history analysis was conducted using actual ground motion data from the Koyna earthquake. The maximum compressive and tensile stresses generated numerically under both gravity and earthquake loading conditions were compared with permissible stresses in accordance with Indian masonry standard codes. The finite element model demonstrated that the building remains structurally sound under gravity loading, although some vulnerable areas were identified under earthquake loading conditions. To mitigate the stresses in these vulnerable zones, various retrofitting techniques were explored. Notably, the application of steel flats on floors and walls, along with GFRP sheeting, proved to be an effective solution, reducing stress levels by up to 90%. [ABSTRACT FROM AUTHOR]

Geometric complexities play an important role in the nucleation, propagation, and termination of strike-slip earthquake ruptures. The 2021 Mw7.4 Maduo earthquake rupture initiated at a large releasing stepover with a complex fault intersection. In the epicentral region, we conducted detailed mapping and classification of the surface ruptures and slip measurements associated with the earthquake, combining high-resolution uncrewed aerial vehicle (UAV) images and optical image correlation with field investigations. Our findings indicate that the coseismic ruptures present discontinuous patterns mixed with numerous lateral spreadings due to strong ground shaking. The discontinuous surface ruptures are uncharacteristic in slip to account for the large and clear displacements of offset landforms in the epicentral region. Within the releasing stepovers, the deformation zone revealed from the optical image correlation map indicates that a fault may cut diagonally across the pull-apart basin at depth. The left-lateral horizontal coseismic displacements from field measurements are typically ≤0.6 m, significantly lower than the 1–2.7 m measured from the optical image correlation map. Such a discrepancy indicates a significant proportion of off-fault deformation or the possibility that the rupture stopped at a shallow depth during its initiation phase instead of extending to the surface. The fault network and multi-fault junctions west and south of the epicenter suggest a possible complex path, which retarded the westward propagation at the initial phase of rupture growth. A hampered initiation might enhance the seismic ground motion and the complex ground deformation features at the surface, including widespread shaking-related fissures. [ABSTRACT FROM AUTHOR]

This research provides a practical and feasible retrofitting solution for soft story in reinforced concrete (RC) buildings with masonry infill walls for example in Nepal through numerical analysis. It is well understood that stiffness and strength of the soft story floor can be increased significantly by adding RC shear wall in the frame opening of the ground floor, making lateral deformation of that floor negligible. With this consideration, the authors have developed a numerical optimization framework for optimizing the RC shear wall in the open floor of soft story building incorporating socio-technical aspects from their previous publication [Timsina, K., Gadagamma, C. K., Numada, M. and Meguro, K. [2019b] "Development of a numerical optimization framework for solving soft-story problem in reinforced concrete frame buildings," Seisan-Kenkyu]. The objective function for numerical optimization is cost minimization with the constraints of usability, performance, and complexity from a detailed field study. In this paper, the numerical optimization framework is developed and solved using the sequential quadratic programing (SQP). The whole scheme has been incorporated inside the 2D-Applied Element Method (AEM). The retrofitting solution thus obtained from the numerical optimization has been analyzed using the incremental dynamic analysis to know the capacity of the frame structure in earthquake ground motion. It shows that the retrofitting method can significantly enhance the soft story frame's capacity and ensure the dwellers' interests are not compromised. [ABSTRACT FROM AUTHOR]

A 500-kV power transformer substation was focused on for seismic performance examination. Finite element models of the power transformer, isolation layers, site soil, bus bars and support structure were established under various analysis conditions. By inputting typical ground motions into the models, seismic time history responses were obtained. First, the seismic performance, critical position and failure modes of a single power transformer without isolation were examined. Then, the effect on the power transformer by arranging isolation bearings was confirmed. Moreover, the influence of site soil dynamic characteristics on the isolating performance of the power transformer was examined. Finally, the influence of the length margin of the bus bars on the seismic response of the isolated power transformer was analyzed. It was revealed that the bottom of the transformer bushings which were made of porcelain was a weak part. Installing isolation bearings effectively reduced the maximum stress response of the bushing for most ground motions. The dynamic characteristics of the site soil significantly affected the isolation efficiency of the power transformer, and the expected isolation effect was achieved when the soil was soft. The displacement response of the transformer was largely increased by isolation, the pulling effect of the bus bars on the porcelain bushing was significant. When the length margin of the bus bars was enlarged to 1.0 m, the influence on the bushing decreased to a low level that could be ignored. [ABSTRACT FROM AUTHOR]

One of the most widely used linear techniques for solving damage identification problems and prediction of the system dynamic behavior is modal testing and analysis. However, most of real structures exhibit nonlinear behavior during their lifetime caused by a number of various reasons. The presence of nonlinearity in a structural system changes its dynamic characteristics; hence, the use of linear techniques is improper for prediction of the system behavior. In this paper, a vibration-based nonlinearity identification technique was proposed to identify early changes in a dynamic system prior to significant damages. This technique combines the time series Autoregressive Moving Average with Exogenous Inputs (ARMAX) modelling, probability theory, and Fuzzy C-Means (FCM) clustering algorithm to categorize the linear and nonlinear dynamic behaviors of a dynamic system. The technique aims to categorize the linear and nonlinear behaviors of a structure, when it is subjected to various levels of excitation source. To show the validity of the proposed method, a series of shake table tests was performed on a six-span steel truss bridge model. The bridge model was excited using different amplitudes of ground motion to control the nonlinearity degree of rubber-based supports. It can be concluded from the analysis results that the new vibration-based nonlinearity identification technique was able to identify nonlinear behavior of the bridge model once it was subjected to different levels of earthquake excitations. This algorithm was able to categorize the linear and nonlinear behaviors of the bridge model and define a specific threshold for different excitation sources. [ABSTRACT FROM AUTHOR]

Estimating the story drift directly from acceleration records is challenging. This paper presents a systematic integration scheme involving the empirical mode decomposition of signals to estimate the earthquake-induced displacement of buildings, including their permanent deformation after an earthquake. A three-phase algorithm is proposed. In phase-1, the displacement waveform without residual displacement is estimated, then in phase-2 the residual deformation is calculated. Combining both phase-1 and phase-2, the displacement waveform is estimated. Three types of acceleration data, namely, shaking table test data, seismic response data for a building, and near-fault ground motion data, were used to validate the proposed method. [ABSTRACT FROM AUTHOR]

As an effective measure to decrease the residual displacement under earthquakes, unbonded prestressed concrete (UBPRC) columns have been carefully investigated in previous research, while the influence of the complex characteristics of near-fault excitations on the residual displacement of UBPRC is less mentioned. This paper, therefore, focuses on the influence mechanism of the pulse effect and vertical effect of near-fault ground motions on the residual displacement of UBPRC columns. The residual displacement, at first, is formulated as a function of the coupled parameter T1-p (the ratio of the structural period to the pulse period). Then, the effect of near-fault vertical ground motion on the residual displacement is qualified based on the established mathematical model. Further, the model has been applied to investigate the effect of structural properties (dead load axial compression ratio, longitudinal reinforcement ratio, prestressing axial compression ratio, prestressing reinforcement ratio) on the residual displacement of UBPRC columns subjected to the joint action of horizontal and vertical ground motions. This research provides a quantitative methodology to quickly obtain the residual displacement spectra of the UBPRC columns under varying conditions combined with ground motion and structural parameters. [ABSTRACT FROM AUTHOR]

The present study investigates the correlation between several seismic parameters and structural responses of reinforced concrete buildings. A large number of ground motion parameters including magnitude and epicentral distance are extracted from 61 near-field earthquake records. A first correlation is made between all the seismic parameters. A 3D model of two reinforced concrete buildings of five and ten stories is developed, and Nonlinear Time History analysis is performed for all ground motion records. The performance of buildings is expressed in terms of interstory drift ratios, roof drift and base shear forces. Relationships between base shear and ground motion parameters are evaluated with coefficient of determination. Correlations studies between seismic parameters, interstory drift ratios, and roof drifts are calculated using Pearson and Spearman correlation coefficients. The correlation between base shear and acceleration parameters, roof drift and PGA reveals high determination coefficients. On the other hand, the maximum interstory drift ratio is weakly related to seismic parameters for both buildings. The results also showed that maximum interstory drift ratio and roof drift are relatively well correlated with some acceleration ground motion parameters according to Spearman coefficient. [ABSTRACT FROM AUTHOR]

The existing constitutive models of shape memory alloy (SMA) cannot accurately describe the mechanical behavior in martensitic strengthening segment since their loading and unloading paths in strengthening segment completely overlap. This study proposes a multi-segment linear mathematical model for SMA, which realizes the separation of loading path and unloading path in strengthening segment. A four-story steel frame structure and corresponding braced structures with various SMA constitutive models are designed, and seismic control effects of SMA braces with these models are analyzed and compared through time history analysis. The results show that the sub-cycle unloading mode of SMA constitutive model affects the seismic mitigation capacity of SMA brace in a certain extent. The position of the inflection point of unloading path has very little influence on the structural control ability of SMA braces. The SMA brace using the SMA constitutive model with a single linear sub-cyclic unloading path has the minimal seismic response and the highest seismic reduction ratio. For most evaluation indexes, the seismic mitigation ability calculated by the proposed path separation constitutive model is in the middle of the results calculated by the existing models. SMA models without considering the mechanical behavior of strengthening segment may lead to an erroneous estimation of the energy consumption of SMA brace and the structural damage. The difference of simulation results among various SMA constitutive models is almost independent with ground motion. [ABSTRACT FROM AUTHOR]

The near-fault ground motion records show a noticeable velocity pulse effect, which poses a significant seismic threat to the high-speed railway track–bridge system. This study conducts the seismic response analysis of the track–bridge system under near-fault ground motions with forward directivity and fling-step effects. It quantifies the degree of damage of each track–bridge system's key component using the component's stiffness degradation coefficient. In addition, this research investigates the influence of velocity pulse effects from near-fault ground motions on earthquake-induced residual geometric irregularities and earthquake-induced dynamic irregularities. It explores the post-earthquake running performance of high-speed trains based on the input of earthquake-induced irregularities, providing a theoretical basis for the seismic design method of the track–bridge system based on running safety. The research results indicated that the stiffness degradation of the track–bridge system under near-fault pulse-type ground motions is more severe compared to near-fault non-pulse ground motions and mid-far-field ground motions. The amplitudes of earthquake-induced residual geometric irregularity and earthquake-induced dynamic irregularity of rails under near-fault pulse-type ground motions are much greater than those under near-fault non-pulse and mid-far-field ground motions. The earthquake-induced alignment irregularity significantly impacts high-speed trains' derailment coefficient and transverse acceleration. Consequently, failing to account for the velocity pulse effect of near-fault ground motions can lead to an overestimation of the post-earthquake running capacity of the track–bridge system. Seismic design considerations for high-speed railway bridges must prioritize the influence of velocity pulse-type ground motions. [ABSTRACT FROM AUTHOR]

There are many parameters that affect the seismic behavior of the bridge, especially in the new type of bridges. In this research, the seismic behavior of a cable-arch bridge as a new type of bridge with a hybrid system of an arch and stay cables has been studied considering the effect of seismic hazard probabilities and vertical excitations. By considering these parameters, the seismic analysis was investigated in three steps: Response spectrum analysis to obtain general seismic behavior of the bridge, time-history analysis using seismic ground motion records to capture dynamic responses, and pushover analysis to determine the capacity of the bridge. The performance of the bridge was monitored, and the significance of considering seismic hazard probabilities and vertical excitations was investigated. Pointing out the effects of these parameters on the seismic behavior of the bridge, the results indicated a requirement for considering them to provide the seismic safety of the bridge. [ABSTRACT FROM AUTHOR]

Site amplification factors (SAFs) of seismic ground motions are essential in evaluating and estimating seismic hazards. In our previous study, the authors proposed a simple and cost-effective method to estimate a SAF based on a deep neural network (DNN) model and microtremor horizontal-to-vertical spectral ratio (MHVR). Since the previous DNN model was based on the observed SAFs and MHVRs within a limited district in Japan, the applicability of the previous model to non-source regions with different site conditions was limited. This study explored the application of a transfer learning (TL) technique to adapt an existing (pre-trained) DNN model to new regions and a different database. The SAFs obtained through generalized spectral inversion technique (GIT) at the seismic observation stations (K-NET and KiK-net) in Japan were collated as the ground truth for site effects. MHVRs recorded at the stations in several districts of Japan were collected to construct a data set for the development of the TL model. Subsequently, a TL model was constructed, leveraging the neural network layers and their weights from the pre-trained model while incorporating additional neural network layers to enhance the performance. During the training process, a total data set of 112 sites was divided into training set, validation set, and external test set by 1:1:5. Utilizing a cross-validation strategy, the residuals between pSAFs (pseudo-SAFs) estimated by the TL model and the observed SAFs were analysed for the external test set containing 80 sites. The results showed that the TL model outperformed the pre-trained DNN model. The cross-validation results demonstrated that almost consistent prediction results were obtained regardless of any combination of 16 sites selected as the training set. Furthermore, by contrasting the influence of varying training set sizes on the performance of the TL model and comparing the TL model to a DNN model with an extended training set, the effectiveness of constructing the model with the limited number of data (16 sites) was ascertained. Finally, the effectiveness and limitations of the TL model were evaluated using MHVRs with peak frequencies falling outside the training set's range. [ABSTRACT FROM AUTHOR]

A Tunable Friction Pendulum System (TFPS) was proposed to investigate its seismic isolation control performance in bridge structures. First, the structural design and theoretical model of TFPS are given. Second, the mechanical properties of TFPS are studied through finite element simulation. Then, the above TFPS is introduced into the bridge structure, and the analysis model is established based on SAP2000. Finally, a nonlinear time-history analysis is carried out on the bridge structure, and the seismic isolation performance of TFPS is evaluated by using the dynamic characteristic response index of the bridge structure. Theoretical derivation and finite element analysis results show that TFPS can adjust the dynamic characteristics in real time according to the spectral characteristics of the ground motion input and the response of the structure itself, so that the friction force can be continuously adjusted and energy consumption can be adjusted. [ABSTRACT FROM AUTHOR]

Displacement-based design (DBD) methods were originally developed in the 1990s for concrete structures and later modified for light-frame wood buildings and mass timber buildings. DBD methods use displacement as the design criterion to minimize economic losses, control component damage, and enable rapid return to functionality for increased resilience. This paper introduces a performance-based design check procedure that uses the direct displacement-based design (DDD) method and numerical pushover analysis for the design of cross-laminated timber and light-frame shear (CLT-LiFS) buildings. Prestressing CLT panels with embedded posttensioning high-strength steel cables or external high-strength steel rods enable them to provide robust lateral load resistance and self-centering capacity. LiFS walls offer additional lateral load resistance and energy dissipation through the slip of nail connections. A six-story CLT-LiFS building was used as a design example meeting three performance levels (damage limitation, life safety, 15 and collapse prevention) based on ASCE/SEI 41-17 criteria. Each performance level corresponds to a set of three criteria: interstory drift limits, cable stress limits, and CLT compressive strain limits at the rocking interface. The design was checked using a series of nonlinear time history (NLTH) analyses with a suite of ground motion records. The results from the design check procedure and the statistical distributions of performance criteria from NLTH analysis confirmed that the six-story CLT-LiFS building met performance expectations. Additionally, a collapse fragility curve was developed to provide a comprehensive understanding of the building's behavior. [ABSTRACT FROM AUTHOR]

The bidirectional ductile end diaphragm concept uses energy-dissipating buckling restrained braces (BRB) as fuses located at the end of a bridge superstructure's floating spans. This system using BRBs can provide seismic resilient and damage-free bridges fully operational immediately after an earthquake. A shake-table testing program was conducted to subject a 1/2.5-scale specimen to series of ground motions. The specimen tested represents one span of a five-span bridge having BRBs connected to the abutment and the pier next to it. The purpose of these tests was to experimentally validate proposed connection details when subjected to the three-dimensional (3D) displacement histories (compared with the axis of the BRBs) that resulted from bidirectional ground motions and the fact that the connections must accommodate inclined BRB layouts. The test protocol included earthquake displacement histories that represent design demands, cycles of thermal excitations, and (to eventually make the BRBs fail) extreme motions. The testing program validated the effectiveness of the proposed concept and the ability of BRBs to sustain multiple ground motions before failure. [ABSTRACT FROM AUTHOR]

• A hybrid method by integrating the advantages of frequency-wavenumber method and finite element method. • The entire process simulation from the source to the local terrain has been achieved. • Seismic response of mountains due to point dislocation source. • The crustal velocity structure and source parameters influence the seismic response. This paper proposes a hybrid method to analyze seismic responses from the source to complex terrain. The hybrid method is based on the domain reduction idea, dividing the overall model into global domain (including the source and propagation path) and local domain (including complex terrain). For the propagation of seismic wave fields in the global domain, a frequency-wavenumber method based on the exact dynamic stiffness matrix is adopted. For the local domain, the finite element method combined with the artificial boundary substructure method is used to analyze the seismic response of complex terrain. The advantage of this hybrid method is that the frequency-wavenumber method can accurately and efficiently calculate the three-component ground motion of the global large-scale model, while the finite element method has a variety of elements and constitutive models, which can finely simulate the local complex terrain. We take the Zigong Xishan Park site as the research object, and verify the correctness of the hybrid method. Based on this, we use the hybrid method to simulate the seismic response of the site, focusing on the propagation process of seismic waves on the mountain surface, the spatial distribution of peak ground displacement, and the effects of crustal velocity structure and source parameters on the seismic response of the mountain. The results show that the propagation of seismic waves and the distribution of peak ground displacement are closely related to changes in terrain, and the crustal velocity structure and source parameters have significant effects on the seismic response of the mountain. [ABSTRACT FROM AUTHOR]

China, situated in the circum-Pacific seismic belt, experiences frequent seismic activity and faces diverse geological conditions, making structural stability of paramount importance, especially under seismic conditions. The majority of current earthquake generation methods do not consider the nonstationary nature of earthquakes. This paper introduces a spectral representation-random function model for generating nonstationary earthquakes, effectively simulating stochastic seismic ground motion. Furthermore, traditional slope stability analysis methods are deterministic and incapable of providing probabilistic assessments of slope instability. Therefore, this paper proposes a unified framework for static and dynamic structural reliability analysis based on the direct probability integration method, quantifying the impact of stochastic seismic ground motion on the dynamic reliability of slope stability. Finally, the proposed methods are applied to an excavation slope in Nanjing, using sliding displacement and safety factors as evaluation criteria to study the reliability of the slope under the influence of stochastic seismic events. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of soil–structure interaction (SSI) on the inelastic displacement ratio of bridge structures subjected to near-fault pulse-like earthquake ground motions. SSI was modeled using a discrete-time recursive filter approach and frequency-dependent foundation–soil impedance functions. A total of 105 near-fault earthquake ground motion records were used for the analysis. The study also compared the soil–foundation–superstructure (SFS) system with a fixed-base system to explore the effects of spectral period normalization, strength reduction factor, earthquake magnitude, site-to-source distance, and peak ground velocity on the inelastic displacement ratio. The findings indicate that both the SFS and fixed-base systems have significant inelastic displacement demand under near-fault earthquakes, with values that can be 2–3 times higher than those predicted by ASCE-41-13, particularly in the short period range. Furthermore, as the structural period approaches the earthquake pulse period, the SFS system generally shows larger inelastic displacement ratios compared to the fixed-base system. The analytical results provide insight into the factors affecting the inelastic displacement ratio for near-fault pulse-like earthquakes. [ABSTRACT FROM AUTHOR]

Torsional status indicators of asymmetrical plan systems are evaluated. The ratio of two modal participation factors in a translational direction (lower to higher mode) is proved as a more accurate indicator than the ratio of translation and rotation dominant modal periods. Seismic responses of low-rise asymmetric-plan frames are then assessed through linear elastic and nonlinear response analysis of representative systems under bi-axial ground motion pairs. The results revealed that those systems that are initially identified as torsionally stiff exhibit a torsionally stiff nonlinear response, whereas those initially categorized as torsionally balanced or flexible evolve to a stiffer torsional performance. [ABSTRACT FROM AUTHOR]

An updated strong-motion database of the Iranian earthquakes has been used to propose empirical equations for the prediction of peak ground velocity (PGV), peak ground acceleration (PGA), and 5%-damped Spectral Accelerations (SA) up to0.0 s for geometric mean of horizontal components. Some records from the NGA-West2 are added to the database to enrich it at near source distances for large magnitude events. Lack of data in the near source distances causes less accuracy in previous Iranian Ground Motion Models (GMMs) in comparison with the current study. In this work, the regression analyses have been performed on a truncated database which causes to obtain unbiased results. We used 3015 acceleration time series from 594 earthquakes after truncation of data to develop a new GMM. The provided model is valid for Joyner-Boore distances ranging from 0 km to80 km and magnitudes ranging from 4 to 7.9 and Vs30 ranging from50 m/s to500 m/s. [ABSTRACT FROM AUTHOR]

The 1 January 2024 Noto-Hanto (Noto Peninsula) earthquake (MJMA 7.6) generated strong ground motion, large crustal deformation and tsunamis that caused significant damage in the region. Around Noto Peninsula, both offshore submarine and partially inland active faults have been identified by previous projects: Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and Japan Sea Earthquake and Tsunami Research Project (JSPJ). We inverted the tsunami waveforms recorded on 6 wave gauges and 12 tide gauges around Sea of Japan and the GNSS data recorded at 53 stations in Noto Peninsula to estimate the slip amount and seismic moment on each of active faults. The results show that the 2024 coseismic slips were 3.5 m, 3.2 m, and 3.2 m on subfaults NT4, NT5 and NT6 of the JSPJ model, located on the northern coast of Noto Peninsula and dipping toward southeast. A smaller slip, 1.0 m, estimated on NT8 on the southwestern end of the 2024 rupture, may be attributed to its previous rupture during the 2007 Noto earthquake. The total length of these four faults is ~ 100 km, and the seismic moment is 1.90 × 1020 Nm (Mw = 7.5). Almost no slip was estimated on the northeastern subfaults NT2 and NT3, which dip northwestward, opposite to NT4–NT5–NT6, and western subfault NT8. Aftershocks including the MJMA 6.1 event occurred in the NT2–NT3 region, but they are smaller than the potential magnitude (Mw 7.1) those faults can release in a tsunamigenic earthquake. Similar features are also found for the MLIT model; the 2024 slip was only on F43 along the northern coast of Noto Peninsula, and northeastern F42 did not rupture, leaving potential for future event. [ABSTRACT FROM AUTHOR]

In current engineering practice, the torsional effects of ground motions are only considered implicitly through "accidental eccentricity coefficients". In seismic design codes, these coefficients account for not only the unintended (or uncertain) asymmetric distributions of structural mass and stiffness in the plan but also the torsional components of ground motions. The torsional effects may develop due to wave passage effects or the incoherency of translational ground motions along the foundation systems. While it is possible to obtain torsional components of ground motions directly from seismic records with modern instruments, such sensors are uncommon. Therefore, several numerical procedures have been proposed in the literature for estimating torsional components of ground motions from translational measurements. In this study, the Single Station Procedure (SSP)—based on the deconstruction of translational ground motions into body waves and the subsequent reconstruction of rotational ground motions—is employed to obtain torsional ground motions for seven different seismic events in Turkey. Additionally, the corresponding accidental eccentricity coefficients that can cause the same response modification with torsional ground motions are determined. First, a conventional procedure is utilized to obtain the corresponding accidental eccentricity coefficients. Various drawbacks of the conventional procedure, such as negative eccentricity coefficients, are addressed. Then, a relatively obscure definition of accidental eccentricity is revived to propose a novel procedure for determining accidental eccentricity coefficients. It is observed that the proposed procedure yields higher values for the accidental eccentricity coefficients than the conventional procedure. It also observed that the torsional spectrum provided in Eurocode 8 provisions requires higher eccentricity values than those implied by the recorded ground motions from Turkey. [ABSTRACT FROM AUTHOR]

This paper presents a study of acceleration demands in low-rise reinforced concrete (RC) buildings with torsion, evaluated by quantifying peak floor accelerations (PFAs) and floor response (acceleration) spectra (FRS). The study was performed with the aim to provide simple empirical formulas to quantify the amplification effects due to torsion, which can occur in most of the existing and new RC buildings. With this goal in mind, a set of eight archetype buildings was selected, characterized by an increasing floor eccentricity obtained by moving the centre of rigidity (CR) away from the centre of mass (CM). Numerical models of the proposed set of archetype RC buildings were considered in both linear elastic and nonlinear configurations. For the latter, the properties of models were widely varied, by systematically modifying parameters of plastic hinges, in order to obtain a sample of 1000 models. Non-structural components (NSCs) were considered linear elastic in all cases. To investigate acceleration demands, a set of forty Eurocode 8 spectrum-compatible ground motion records were used as input. For linear elastic building models, it was observed that the change of demands depends on the position of the NSC (in-plan and in-height), and on the distance between CR and CM. On the other hand, for nonlinear models, additional parameters must be considered, such as the building ductility (μ) and yielding force (Vy). New regression models were proposed for quantifying the observed differences in PFAs and FRS when torsion occurs. The efficiency of the proposed models was assessed by testing the new formulas on an existing case study building, as well as on the well-known SPEAR building. [ABSTRACT FROM AUTHOR]

Soil exhibits inherent spatial variability, creating a significant source of uncertainty in geotechnical assessments. This variability becomes particularly critical when evaluating the seismic performance of infrastructure such as multi-span highway bridges, since traditional methodologies in bridge design often oversimplify soil properties by assuming uniformity. This approach, however, may lead to considerable inaccuracies in determining structural response under seismic activity. The complexity of soil–structure interaction (SSI) in such multi-span structures further exacerbates the influence of soil spatial variability on the overall structural response to seismic events. Although numerous studies have explored the impact of spatial variation in ground motions on seismic performance, a noticeable gap exists in the literature addressing soil spatial variability in the SSI modeling and its impact in the seismic response of multi-span bridges. Accordingly, this research aims to address this gap by proposing a numerical framework that integrates the inherent spatial variability of soil in SSI modeling by means of random fields theory and 3D nonlinear dynamic finite element models into the seismic performance analysis of multi-span bridges. The findings from a case study reveals a significant influence of soil spatial variability on structural response, leading to discrepancies in vulnerability assessment between different bridge components and highlighting the importance of incorporating spatial variability in soil parameters into seismic assessments of bridges. Moreover, soil variability appeared to slightly impact system-level vulnerability. Although the main conclusions are developed from a case study and are applicable to bridges with similar characteristics and seismic demand, the proposed approach can readily be applied to other bridge configurations and seismic environments. [ABSTRACT FROM AUTHOR]

In low to moderate seismic regions such as the Korean peninsula, it is difficult to perform seismic hazard analyses to construct hazard maps and curves because only a limited number of strong ground motion records is available. In this study, to solve such obstacles, ground motions are simulated using a stochastic model for Fourier amplitude spectrum (FAS) in frequency domain and shaping window model in time domain. The generalized inversion technique is adopted to determine the seismological characteristics (source, path, and site effects) of the FAS for Korean region. The validity of the source, path, and site effects obtained from the GIT and that of simulated ground motions is verified. [ABSTRACT FROM AUTHOR]

RC double-column medium height bents (DCMBs) are widely applied in the mountain areas as the substructure of highway bridges, and the two columns are normally connected by RC link beams to enhance the lateral stability. However, serious damage and/or large residual displacement were repeatedly observed in the DCMBs after many major earthquakes, which may make the bridges lose functionality and have to be demolished and rebuilt. In order to improve the seismic performance of the bridges, a novel self-centering variable friction dissipation brace (SCVFB) using SMA plates is developed to replace the traditional RC link beams in the DCMBs in this study. The mechanical properties of the shape memory alloy (SMA) plate were investigated experimentally. Then, the analytical model of the DCMBs with inverted-V SCVFBs (DCMB-SVFB) is built, and the corresponding design philosophies of the SCVFB in the DCMB are proposed based on the concept of structural fuse. Subsequently, the hysteretic behaviors of the DCMB-SCVFB in the transverse direction are analyzed, and the dynamic responses of the whole bridge under near-field ground motions are also investigated. For comparison, the seismic behaviors of the bridges with original bents (the bridges with and without link beams) and the bridges retrofitted with buckling restrained braces (BRBs) are also presented. The results show that the SCVFB has stable energy dissipation capability and excellent self-centering ability, even without the need of prestressing. Compared with the original bridge, the bridges with SCVFBs and BRBs are featured by higher strength, larger stiffness, better energy dissipation capacity, and less damage. In particular, the SCVFB can effectively reduce the residual displacement of the bridge and quickly restore the traffic capacity. [ABSTRACT FROM AUTHOR]

The Sichuan–Yunnan area is one of the most seismically active regions in China. As ground-motion models form a key component of seismic hazard analysis, it is important to select (or develop) appropriate models for this area. The increasing number of digital ground-motion records of earthquakes in this area has allowed the development of local ground motion prediction equations (GMPEs). This study compares and, later, recommends appropriate GMPEs for the Sichuan–Yunnan area. We first evaluate the inherent quality of local GMPEs, with respect to their underlying datasets, the variables used and their functional forms, to determine a set of candidate GMPEs. Then we investigate how well the predictions from the GMPEs match observations computed from strong-motion records of recent earthquakes in this area. The fit between predictions and observations varies significantly amongst the GMPEs. The results suggest that some recent local GMPEs would lead to biased ground-motion estimates due to limitations of their underlying datasets and functional forms. Based on both evaluations of inherent quality and compatibility with observations, only one local GMPE is recommended. A comparison of the predictions from three widely-used non-local GMPEs indicates that ground motions in the Sichuan–Yunnan area appear more variable than those in other regions but that predictions from these non-local GMPEs are generally unbiased. We recommend use of a mixture of robust local and non-local GMPEs within seismic hazard analyses to capture the epistemic uncertainty in ground-motion prediction for this area. [ABSTRACT FROM AUTHOR]

This paper introduces a framework to estimate the seismic response of buildings at a regional scale by using representative indicator buildings. A robust database of buildings is required in the proposed framework to provide high-level structural and site information of the buildings. In this study, a database of 234 reinforced concrete buildings with five or more stories located in the central business district of Wellington, New Zealand was selected as a case study. In a prior phase of the research, the buildings were clustered into typologically similar clusters and eight representative indicator buildings were selected, where an indicator building was the closest building to the mean cluster structural and site characteristics. In this work, the concept of using indicator buildings to estimate building response across each cluster is investigated. First, three-dimensional structural models of each of the eight selected indicator buildings from the Wellington database were developed using the opensource structural analysis program OpenSeesPy. Five models were developed for each indicator building: one nonlinear model, one linear model, and three linear supplementary models where the effective stiffness of the structural members were modified to represent the period range of all buildings across a given cluster. The supplementary models were used to develop a period correction relationship to modify the estimated drifts based on the spectral shape of the imposed ground motion. Ground motions from the 2016 Kaikōura and 2013 Seddon earthquakes in New Zealand, as well as the 1995 Kobe earthquake in Japan, were selected to evaluate the proposed framework. The relationships between predicted elastic and inelastic drifts were explored, and polynomial regression models were investigated to provide drift correction accounting for the spectral shape of the three earthquakes. Finally, the efficacy of the proposed framework in estimating the response of all buildings across all clusters and the applicability of this framework as a near real-time impact tool were demonstrated using post-earthquake damage reports from the Kaikōura and Seddon earthquakes. [ABSTRACT FROM AUTHOR]

This technical report explains details on the results of the investigation to build a subsurface structural model and a selection of earthquake data at the target site of the blind prediction exercise for "The 6th International Association of Seismology and Physics of the Earth's Interior/International Association of Earthquake Engineering International Symposium on the Effect of Surface Geology on Seismic Motion (ESG6)." The selection process of the target site in the Kumamoto Plain, Japan, in ESG6 was explained with a historical review of the blind prediction tests in the previous ESG conferences. We have collected existing subsurface structural and earthquake data and conducted geophysical and geotechnical surveys in and around the target site to generate important velocity structure and the earthquake data used in the blind test. Microtremor data were obtained in triangular arrays ranging in side lengths from 1 to 962 m, and active surface wave data were derived along a 36-m line at the site. These data were provided for the prediction of a subsurface structural model in the first step of the blind prediction exercise. We also conducted a velocity logging in a borehole to a bottom depth of 39 m at the site and laboratory tests of soil samples from the borehole. We constructed a velocity profile of the shallow and deep sedimentary layers from a combination of the geophysical and geotechnical data at the site, and validated it by comparing the characteristics of the ground motion data from the moderate event. This "preferred velocity model" was provided as a standard model to the participants in the second and third steps of the blind prediction test to predict the earthquake ground motions of a moderate event and the mainshock of the 2016 Kumamoto earthquake. [ABSTRACT FROM AUTHOR]

The mutual gravitational interaction of binary asteroids, which make up approximately 15 per cent of the near-Earth asteroid (NEA) population, provides a continuous tidal force, creating ground motion. We explore the potential of kilometre-sized binary asteroids as targets for seismological studies of their interior structure. We use a numerical model wherein each body is constructed of discrete particles interacting via gravity and contact forces. The system's orbital properties are modelled based on those of typical binary NEAs: a secondary body orbits a primary body at a distance of a few to 10 primary radii, resulting in orbital periods of a few tens of hours. We varied the elastic moduli (stiffness) of the constituent particles and measured a strain of a few micrometres caused by the orbiting satellite. Over eight orbital periods, the acceleration of the strain vector along the primary body's equatorial axis indicates that tidally induced ground motion generated by a binary asteroid system is detectable by modern seismometers, like the instruments deployed on the InSight mission to Mars. Owing to the relatively short orbital period of the satellite – a mean of 25.8 h for known binary NEAs – only a modest mission lifetime would be required for a seismometer to adequately characterize an asteroid's interior through tidally induced deformation. Future deployment of seismometers on binary asteroids will allow for a detailed characterization of the structure of these objects. [ABSTRACT FROM AUTHOR]

Low computational efficiency and non-linearity behaviour make the simulation of the overall building structure problematic to attain with a single dynamic or static method. Thus, this paper uses a plastic deformation (PD) method based on concrete plasticity theory (CPT) for comparative analysis of multi-storey reinforcement cement concrete (RCC) and composite buildings under common and rare earthquake loads. For this purpose, a 15-storey tall building was selected for analysis using ABAQUS software. At first, a possible building model was created and then plastic deformation analysis was performed using the new PD method under both common and rare earthquakes. After that, a nonlinear time history analysis was conducted, and the results of plastic strain distribution, lateral displacement, peak acceleration, storey stiffness, shear force, storey drift, normalised shear, and top deflection of the RCC and composite buildings were studied deeply. The fundamental time period of the RCC model was found to be 5.2 s while the fundamental time period of the composite model was 6 s. Under common and rare earthquake leads, the peak acceleration of the RCC building was 19% and 22% higher than composite buildings, respectively. Under common and rare seismic loads, the top deflections of the composite building were 33% and 36% higher than those of RCC buildings, respectively. In the case of the RCC building, it was found in this study that higher peak acceleration (PA) of the ground motion led to higher storey top displacement, storey drift, shear force and top deflection under both ground motions. Numerical results suggested that the use of composite structure is more durable than RCC structure. It was also concluded that the PD method could also be effectively used for the analysis of RCC and composite buildings under dynamic loads. [ABSTRACT FROM AUTHOR]

Rapid and accurate prediction of peak ground acceleration (PGA) is an important basis for determining seismic damage through on-site earthquake early warning (EEW). The current on-site EEW uses the feature parameters of the first arrival P-wave to predict PGA, but the selection of these feature parameters is limited by human experience, which limits the accuracy and timeliness of predicting peak ground acceleration (PGA). Therefore, an end-to-end deep learning model is proposed for predicting PGA (DLPGA) based on convolutional neural networks (CNNs). In DLPGA, the vertical initial arrival 3–6 s seismic wave from a single station is used as input, and PGA is used as output. Features are automatically extracted through a multilayer CNN to achieve rapid PGA prediction. The DLPGA is trained, verified, and tested using Japanese seismic records. It is shown that compared to the widely used peak displacement (Pd) method, the correlation coefficient of DLPGA for predicting PGA has increased by 12–23%, the standard deviation of error has decreased by 22–25%, and the error mean has decreased by 6.92–19.66% with the initial 3–6 s seismic waves. In particular, the accuracy of DLPGA for predicting PGA with the initial 3 s seismic wave is better than that of Pd for predicting PGA with the initial 6 s seismic wave. In addition, using the generalization test of Chilean seismic records, it is found that DLPGA has better generalization ability than Pd, and the accuracy of distinguishing ground motion destructiveness is improved by 35–150%. These results confirm that DLPGA has significant accuracy and timeliness advantages over artificially defined feature parameters in predicting PGA, which can greatly improve the effect of on-site EEW in judging the destructiveness of ground motion. [ABSTRACT FROM AUTHOR]

To reasonably evaluate the overall seismic performance of infilled wall frames, a corresponding nonlinear analysis model is constructed with infilled wall frames as the research object. It quantifies the failure levels of structural and non-structural components and proposes a method for extracting structural overall performance indicators. The vulnerability of the case frame structure is analyzed using the Incremental Dynamic Analysis (IDA) method. The results showed that the seismic performance of the infilled wall frame and the ordinary frame met the seismic fortification requirements, and the seismic capacity of the infilled wall frame was better. After implementing a 7-degree seismic fortification, the cumulative probability of basic integrity, minor damage, and moderate damage for infill wall frames reached 99.15 %, surpassing the fortification target of 1.5 g. However, the seismic capacity of ordinary frames was overestimated, as their cumulative probability of basic intact, minor damage, and moderate damage under a 7-degree seismic fortification was 99.7 %. Neglecting its impact, ordinary frames exhibited lower seismic performance compared to other structures, with a basic intact probability of only 48.49 % under frequent earthquake actions at 7 degrees. The research utilizes effective methods for evaluating the seismic vulnerability of infilled wall frames. [ABSTRACT FROM AUTHOR]

Two adjacent groundwater wells on the North China Platform are used to study how earthquakes impacted aquifers. We use the response of water level to solid Earth tides to document changes after earthquakes and how aquifer and fracture properties recovered to pre‐earthquake properties. We consider two models for the phase and amplitude of water level response to the lunar diurnal (O1) and semidiurnal (M2) tides: a leaky aquifer model, and a model in which fracture orientation determines the response. In the leaky aquifer model, changes arise from changes in permeability and storage; in the fracture model, changes are due to changes in apparent orientation of transmissive fractures. Responses in one well are best explained by the leaky aquifer model, and can explain the large amplitude coseismic water level and permeability changes and the non‐recoverable changes after the largest earthquake. Responses in the other well are consistent with the fracture model and show little coseismic change in water level but changes in apparent fracture orientation. Larger ground motions lead to larger coseismic water level changes and longer recovery times. We propose that the well in the more permeable and shallow aquifer has less variable pore‐pressures around the well. Larger coseismic strains from water level changes may enable longer‐lasting changes in aquifer properties. We conclude that relatively high permeability aquifers are less susceptible to impacts from seismic waves, and thus have small changes in water levels and hydrogeological properties. Plain Language Summary: After large earthquakes, the properties of aquifers can change, leading to changes in water levels in wells. We study changes in water levels that we attribute to changes in the properties of fractures or the permeabilities of aquifers that connect to the wells. We do so by monitoring how deformation caused by tides leads to changes in water levels in two wells. The deeper well in a less permeable formation has larger changes. The larger the ground motion from earthquakes and the larger the amplitude of the coseismic water level changes, the more likely and larger the changes in permeabilities. The larger the changes, the slower the recovery to pre‐earthquake properties. The shallower well in a more permeable formation has smaller changes and no long‐term changes in water level and hydrogeological properties, which we attribute to more uniform pore‐pressures around the well. Key Points: high permeability aquifers are less susceptible to disruption by seismic waveshydraulic property changes depend on the amplitude and frequency of ground motionlarger water level changes accompany larger changes in fracture orientation and irreversible changes in aquifer properties [ABSTRACT FROM AUTHOR]

Dynamic reliability evaluation of large-scale reinforced concrete (RC) structures is one of the most challenging problems in engineering practices. Although extensive endeavors have been devoted to mechanical analysis of concrete structures in the past decades, it was recognized that the randomness from both structural parameters and excitations have significant effects on the dynamic behaviors of structures with complex nonlinearity, damage, energy dissipation, and plasticity. Thus, great difficulty exists in evaluating the nonlinear stochastic responses and dynamic reliability of the real-world complex structures of large degrees of freedom. In the present paper, a physically driven method for refined probabilistic response and seismic reliability evaluation of real-world RC structures is proposed via synthesis of the refined mechanical analysis and the physically-based uncertainty propagation. In this method, the material parameters can be treated as probabilistically dependent random variables characterized by vine copulas, and the ground motion is modeled by non-stationary Clough–Penzien spectrum. The uncertainty propagation of arbitrary response quantity(-ies) of interest is governed by the dimension-reduced probability density evolution equation (DR-PDEE). The intrinsic drift coefficients in the DR-PDEE are the physically driven force for the uncertainty propagation and can be identified via data from representative dynamic analyses of the structure. The time-variant reliability of the structures can be captured by solving the physically driven DR-PDEE, which cannot be achieved by the general Monte Carlo simulation (MCS) due to the prohabitively large computational cost. Finally, a practical engineering application is shown in this paper for the probabilistic response and seismic reliability evaluation of a 24-story RC shear wall structure with nearly 280,000 degrees of freedom (DOFs). [ABSTRACT FROM AUTHOR]

The hysteretic damping tuned mass damper (HD-TMD), which exhibits linear damping force, has been achieved by variable friction devices. Such devices own the advantages of stable mitigation capacity and easy maintenance compared to viscous damping devices. Previous studies have mainly concentrated on the vibration mitigation effect of the HD-TMD system without explicit consideration of structural acceleration control. In this context, seismic optimizations of HD-TMD for structural acceleration control were presented, and the effective damping of HD-TMD was investigated. H∞ optimizations of the HD-TMD were considered for undamped and lightly damped structures with fixed-point theory, where the closed-form solutions of optimal and improved parameters were derived. Parametric analysis for the dynamic amplification factors (DAFs) of structural acceleration revealed that the closed-form solutions effectively tuned the DAF into double peaks and reduced the maximum response overall frequency. H2 optimizations were conducted with residue theory for the optimization of the undamped structure, and the optimal parameters of HD-TMD subjected to stochastic ground excitation were obtained by numerical searching and curve-fitting techniques. Effective damping of the HD-TMD was consequently examined using the stochastic stationary process in which the damping effect additionally provided to the structure was measured. The effectiveness of the proposed optimal solutions for the HD-TMD in the form of an available engineering variable friction device was thereby corroborated by twenty sets of seismic ground motions. Spectrum's results indicated that the proposed optimal parameters greatly improved the absolute structural acceleration response and provided excellent seismic mitigation capacity for structural displacement response. The response of the equivalent SDOF demonstrated almost the same trend of absolute structural acceleration reduction, which revealed the successful application of effective damping of HD-TMD for designers. Detailed analysis of the earthquake record indicated the functionality and effectiveness of the proposed methods of HD-TMD with the average absolute structural acceleration reduction ratio of 65.86% and 42.66% for maximum reduction and standard deviation reduction, respectively. [ABSTRACT FROM AUTHOR]

Digital twins efficiency lies in fast and representative solutions of inverse problems to accomodate models with physical observations. The quality of the solution of an inverse problem is conditioned by inherent features of the latter, in particular (i) the richness of available data, (ii) the a priori experimental and modeling knowledge that allows to regularize the ill-posedness nature of the problem, and (iii) the complexity of the space in which updated parameters are sought. We present in this contribution a fully automated physics-guided model updating framework dedicated to the correction of finite element models from low-frequency dynamics measurements. The proposed methodology is based on the minimization of a modified Constitutive Relation Error (mCRE) functional, whose basic idea is to construct mechanical fields and identify material parameters that are a trade-off between all available information (and associated confidence) but without any further assumption. The dependency into some expert-user's judgment is thus avoided. Dedicated rules are provided to automatically calibrate all mCRE internal tuning parameters as well as a strategy to optimize the space in which parameters are sought, leading to a fully autonomous algorithm. The performance and robustness of the proposed model updating methodology are illustrated using synthetic ground motion tests on a bending plate in which defects of various shapes are identified from noisy acceleration datasets, with inherent limitations due to richness of input loading, sensors sparsity and defect identifiability. [ABSTRACT FROM AUTHOR]

The structure of a high-speed railway (HSR) bridge with a track system is complex, and the computational efficiency of seismic analysis for a refine HSR bridge with a track system model (BM) is low. This study considers an HSR bridge with CRTS II slab ballastless track system as a case study and develops a simplified model (SM) based on a method for simulating track constraints with equivalent springs. To obtain the optimal equivalent springs stiffness of SM, a finite element structural parameters updating framework utilizing an improved genetic algorithm is established, and the updated SM's dynamic characteristics and seismic response are compared to BM's. In addition, it uses SM to analyze the over-limit state and applicability of the bridge structural essential components. The results indicated that the model simplification ratio of SM reaches 95%. The seismic response results of SM and BM accurately agree with an average relative error of 3% and a maximum relative error of less than 5%. The over-limit state of the structure seismic response tends to be stable as the number of ground motion samples increases. The shear and bending capacity of the pier and the deformation of the fixed support have a high over-limit risk under longitudinal seismic, which is worth noting in the engineering design. [ABSTRACT FROM AUTHOR]

The amplification of seismic waves due to surface topography and subsurface soils is a significant factor contributing to seismic site amplification and consequent damage. However, conventional deterministic analysis methods can hardly account for the impact of inherent spatial variability of subsurface soil properties. This study employs a random finite element method (RFEM) to address this limitation and investigate the amplification of ground acceleration in time and frequency domains for 2D slope models with varying magnitudes of soil elastic modulus (E) and coefficients of variation (COVs). Comprehensive insights are provided through the analysis of amplification indicators related to peak ground acceleration, Fourier spectrum ratio, and response spectra of input motion. It is found that the spatial variability of E reduces the maximum amplification factor (AF) at the slope crest. Frequency domain analyses show that considering spatially variable E leads to decreasing trends in Fourier spectra and mean values of the transfer function, especially in the mid-to-high-frequency range. However, transfer functions for topographic effects exhibit high-frequency amplification in models with a higher impedance ratio. For the response spectra, the topographic amplification factor (TAF) and spectra amplification factor (SAF) at longer periods gradually increase in random simulations, indicating the potential risk for long-period structures. The findings emphasize the significance of spatial variability in soil properties for seismic amplification, providing probabilistic insights for seismic design and optimization in complex site conditions. [ABSTRACT FROM AUTHOR]

Seismic site effects (topography, geology, internal fracture, et al.) and direction amplification are an important component in inducing a landslide during an earthquake. The evaluation of the dynamic response characteristics of a slope is the first and important step in earthquake engineering design and regional hazard assessment. To document the seismic response of an irregular slope, broadband seismic field monitoring seismometers were deployed along an earthquake-induced landslide Mogangling slope, on the one of important water systems in Sichuan, Dadu River. Field monitoring data reveal that ground motion is directionally amplified near 80° clockwise from North parallel to slope inclination when the frequency is between 3 and 4 Hz, at the crest of the Mogangling slope. During an earthquake, the peak ground acceleration of the M1 station (slope crest) is 5.3 times greater than the M3 station (near slope toe). The standard spectral ratio (SSR) of the slope crest/slope toe (M1/M3) reaches a value of 11.5 at 1.4 Hz, during the earthquake. A series of discrete element numerical models indicate that SSR of the field monitoring data can be reproduced considering the irregular geometry, surficial weak layer, and internal fractures. The recent Luding earthquake on 5 September 2022 with a magnitude of Ms 6.8 induced slope failure in the Mogangling slope reveals the seismic amplification effect again. Our findings can offer some important insights into the mechanism of earthquake-induced landslide and regional-scale landslide distribution. [ABSTRACT FROM AUTHOR]

Earthquake-induced plane failure is typically generated on bedding rock slopes. This failure mode has been widely observed in the past earthquakes in Western China (e.g., Wenchuan earthquake). Among them, the multi-slip plane failure may occur with the presence of multiple bedding planes or internal discontinuities within the slopes. This study developed an extended Newmark sliding block model to investigate the multi-slip seismic displacements of the bedding rock slopes. The unified formulation is presented for seismic sliding analysis of bedding rock slopes with arbitrary numbers and inclinations of bedding planes. Both horizontal and vertical earthquake ground motions and the possible amplifications that may result from site and topographic effects are considered. The developed model is validated by the results from shaking table test. The multi-slip mechanism and the effects of dip angle of bedding planes and vertical ground motion are investigated. The results show that (1) the multi-slip failure evolution is different to that identified from the traditional method, indicating the significant interactions among the seismic sliding behavior associated with bedding planes. (2) The influence of the vertical component of ground motion on the multi-sliding displacement is within a range of 20%. (3) The dip angle of sliding planes has a large effect on the sliding displacement, even if the yield coefficient remains the same. Finally, the proposed method is used to evaluate the seismic displacement and performance of the Liujiawan landslide that was triggered in Wenchuan earthquake. [ABSTRACT FROM AUTHOR]

Visual obstacle discovery is a key step towards autonomous navigation of indoor mobile robots. Successful solutions have many applications in multiple scenes. One of the exceptions is the reflective ground. In this case, the reflections on the floor resemble the true world, which confuses the obstacle discovery and leaves navigation unsuccessful. We argue that the key to this problem lies in obtaining discriminative features for reflections and obstacles. Note that obstacle and reflection can be separated by the ground plane in 3D space. With this observation, we firstly introduce a pre-calibration based ground detection scheme that uses robot motion to predict the ground plane. Due to the immunity of robot motion to reflection, this scheme avoids failed ground detection caused by reflection. Given the detected ground, we design a ground-pixel parallax to describe the location of a pixel relative to the ground. Based on this, a unified appearance-geometry feature representation is proposed to describe objects inside rectangular boxes. Eventually, based on segmenting by detection framework, an appearance-geometry fusion regressor is designed to utilize the proposed feature to discover the obstacles. It also prevents our model from concentrating too much on parts of obstacles instead of whole obstacles. For evaluation, we introduce a new dataset for Obstacle on Reflective Ground (ORG), which comprises 15 scenes with various ground reflections, a total of more than 200 image sequences and 3400 RGB images. The pixel-wise annotations of ground and obstacle provide a comparison to our method and other methods. By reducing the misdetection of the reflection, the proposed approach outperforms others. The source code and the dataset will be available at https://github.com/xuefeng-cvr/IndoorObstacleDiscovery-RG [ABSTRACT FROM AUTHOR]

The stochastic response of multi-story buildings isolated by laminated rubber bearing (LRB), lead-rubber bearing (N-Z system), friction pendulum system (FPS), and resilient-friction base isolator (R-FBI) is investigated under the independent multi-hazard scenario of earthquake ground motion (EQGM), wind load (WL), and blast-induced ground motion (BIGM), which are considered as uncertain inputs. A polynomial regression-based Monte Carlo simulation (PRBMCS) is proposed to enable computationally efficient fragility assessment of base-isolated buildings. The suitability of the PRBMCS for stochastic assessment of the base-isolated buildings is compared with the conventional Monte Carlo simulation (MCS), response surface method (RSM) and Cloud analysis. The fragility curves obtained using the PRBMCS are in good agreement with that of the MCS relatively. The study includes: the effects of the characteristic parameters of the four base isolators on the fragility of the base-isolated buildings under the three hazards; influence of the extent of uncertainty in the excitations; and comparison of fragilities of the base-isolated and fixed-base buildings. Notably, the influences of characteristic parameters of the isolators on the fragility of the base-isolated buildings are different under the three hazards. The differences in the stochastic behaviour under the different hazards could have contradictory influences on the selection of isolation parameters. [ABSTRACT FROM AUTHOR]