Search Results (156)

We have proposed the reduction in triple integral to double integral that is used in multiple shear mechanism model for faster 3D nonlinear ground motion analysis. In this study, we propose reformulation of the mechanism which results in the expression of an elasto-plastic tensor as the product of strain and 4th-, 6th- and higher-order tensors. Storing these high-order tensors in a database, we can eliminate numerical computation required for the triple or double integration. Because the database is stored in the memory of a computational node, it is necessary to design the database considering the trade-off relation between the database size and the accuracy of computing the elasto-plasticity tensor. We carried out numerical experiments to verify the reformulation that uses the database for high-order tensors and to examine the performance of using the database. It is shown that the computational time is reduced to approximately 2% by using the reformulation and the database. Full article

This study develops a comprehensive workflow for the analytical seismic vulnerability and structural performance assessment of a special-importance steel building located in a region of elevated seismic hazard in southern Spain. The work addresses the need for reliable analytical methodologies for facilities that must remain operational during earthquakes. The proposed framework integrates a probabilistic seismic hazard assessment, including uniform hazard spectra and hazard disaggregation to identify control earthquakes. Additionally, an analytical vulnerability assessment under the Spanish seismic design code, NCSE-02, is performed. Operational modal analysis and nonlinear analysis are combined to retrofit the numerical model of the building and capture the building’s realistic seismic response. The resulting demand spectra are derived from site-specific ground-motion scenarios for Los Barrios (Cádiz, Spain). Retrofitting strategies are designed and assessed to ensure compliance with the code-defined performance requirements. Results indicate that the retrofitted model reproduces the building’s dynamic behaviour with improved reliability, and that the strengthening interventions enhance seismic performance while still allowing moderate damage in specific components. These findings highlight the importance of analytical vulnerability approaches and code-oriented retrofitting when evaluating the seismic performance and vulnerability of essential facilities. The study demonstrates that rigorous analytical methods provide a robust basis for defining seismic vulnerability in special-importance buildings and support improved decision-making for structural safety and resilience. Full article

Uplift pressure is a major contributor to seismic instability in arch dam abutments, particularly where jointed rock masses form wedge-shaped failure blocks. This study develops an integrated numerical framework combining nonlinear finite element analysis, the Londe limit-equilibrium method, and Incremental Dynamic Analysis (IDA) to quantify the seismic stability of multiple abutment wedges in the Bakhtiari Arch Dam. A three-dimensional finite element model is used to compute dam–abutment thrust forces, while sixteen far-field ground motions are scaled to capture the progression of wedge instability with increasing spectral acceleration. Uplift pressures on joint planes are varied to represent different levels of grout curtain performance. The results indicate that uplift pressure is the dominant factor controlling wedge stability, substantially reducing effective normal stresses and shifting IDA and fragility curves toward lower acceleration demands. Deep wedges (WL4, WL5, WL6 located in the left abutment of the dam) exhibit the highest vulnerability, with instability probabilities exceeding 50% at spectral accelerations as low as 0.34 g under 50% uplift conditions, compared with values greater than 0.65 g for upper wedges. Parametric analyses further show that increasing the joint friction angle significantly enhances seismic resistance, whereas cohesion has a comparatively minor effect. The findings emphasize the necessity of accurate uplift characterization and wedge-specific seismic assessment, and they highlight the crucial role of grout-curtain effectiveness in ensuring the seismic safety of arch dam abutments. Full article

The behavior of shield tunnel lining structures is known to be influenced by segmental joints. Most studies conducted in this area use simplified models, which may not properly simulate the behavior of the segmental joints. This study utilizes a full-reinforced concrete segment model to rigorously investigate the seismic behavior of joints in a segmental tunnel lining, explicitly accounting for segment–segment contact, interaction, and joint bolts. Specifically, a comprehensive full dynamic analysis of a two-dimensional (2D) lining–soil model, incorporating nonlinear constitutive models for both concrete (CDPM) and soil (Mohr–Coulomb), was conducted to investigate the effects of joint bolt type, seismic intensity, and vertical excitation component on the seismic response. The lining–soil model was excited using three ground motions. The results indicate that the joint rotation is significantly influenced by the amplitude and frequency content of ground motions, which has implications for the watertightness of the gasketed joint. In particular, including the vertical component of the excitations was found to increase the diametral deformation by at least 150% and tended to increase other structural responses. Moreover, the bolt tension increased significantly by over 400% with only a 150% increase in seismic intensity, highlighting the strong nonlinear sensitivity. However, due to the inherent constraints of the 2D plane-strain assumption, the influence of the bolt type remains inconclusive. Full article

As vital components of urban rail transit networks, subway stations are widely scattered across diverse urban districts, whose sustainability performance exerts a notable impact on the overall urban ecological and environmental quality. This study constructs a three-dimensional numerical model to conduct a comparative assessment of the seismic behavior of subway stations adopting different bearing systems at beam-column joints. The seismic responses of two typical structural configurations, a traditional rigid-jointed subway station and another equipped with rubber isolation bearings, are examined under a series of ground motions, with due consideration of amplitude scaling effects and material nonlinearity. A comprehensive evaluation is carried out on key performance parameters, including structural acceleration responses, column rotation angles, damage evolution processes, and internal force distributions. Based on this analysis, the research clarifies the sustainability implications by establishing quantitative correlations between seismic response indices (i.e., deformation extent, damage degree, and internal force magnitudes) and post-earthquake outcomes, such as repair complexity, material requirements, carbon emissions, and socioeconomic effects. The results can advance the integrated theory of seismic-resilient and sustainable design for underground infrastructure, providing evidence-based guidance for the optimization of future subway station construction projects. Full article

Accurately reproducing the mechanical and dynamic behavior of fractured rock masses remains a key challenge in rock engineering, especially in marble quarry environments where discontinuity networks, excavation geometry, and topographic effects induce highly non-linear stress distributions. This study presents a multidisciplinary and physically calibrated numerical approach integrating field stress measurements, structural characterization, and dynamic modeling using the Distinct Element Method (DEM). The analysis focuses on a marble quarry located in the Apuan Alps (Italy), a tectonically complex metamorphic massif characterized by intense deformation and pervasive jointing that strongly influence rock mass behavior under both static and seismic loading. The initial stress field was calibrated using in situ measurements obtained by the CSIRO Hollow Inclusion technique, enabling reconstruction of the three-dimensional principal stress regime and its direct incorporation into a 3DEC numerical model. The calibrated model was then employed to simulate the dynamic response of the rock mass under seismic loading consistent with the Italian Building Code (NTC 2018). This coupled static–dynamic workflow provides a realistic evaluation of ground motion amplification, stress concentration, and potential failure mechanisms along pre-existing discontinuities. Results demonstrate that physically validated stress initialization yields a significantly more realistic response than models based on simplified lithostatic or empirical assumptions. The approach highlights the value of integrating geological, geotechnical, and seismological data into a unified modeling framework for a sustainable quarry stability analysis in fractured rock masses. Full article

The Philippines, located along the Pacific Ring of Fire, is highly susceptible to significant seismic activity arising from the active convergence of major tectonic plates. These seismic events often induce ground shaking intense enough to trigger soil liquefaction, particularly in geologically sensitive regions such as Davao del Sur. This study presents a nonlinear static and dynamic analysis of a mat foundation for a proposed midrise building located within the liquefaction-prone zone of Padada, Davao del Sur. Geotechnical data were obtained through rotary drilling and Standard Penetration Tests (SPTs), which provided the basis for developing the numerical model. Liquefaction assessment was conducted using the PLAXIS Liquefaction Model (UBC3D-PLM), confirming that the site adjacent to the Padada–Mainit River exhibits a high liquefaction potential. Subsequently, finite element analyses were performed in PLAXIS 3D using ground motion records from the 2013 Bohol Earthquake, scaled to 1.0 g, and modeled under the Hardening Soil Model with Small-Strain Stiffness (HSsmall). Results showed excess pore pressure ratios approaching 1, and vertical displacements of the mat foundation exceed 100 mm. These results suggest severe degradation in soil strength, as well as reduced friction angles and mobilized pressure. Full article

In performance-based seismic design theory, the accurate selection of ground motion intensity parameters is crucial for the probabilistic assessment of structural seismic performance. To achieve efficient, sufficient, applicable, and complete prediction of structural seismic demands, this study systematically evaluates the comprehensive performance of 35 commonly used ground motion intensity measures (IMs). The research begins by analyzing 178 real records from the Pacific Earthquake Engineering Research Center (PEER) database, employing the Spearman rank correlation to reveal intrinsic relationships among the parameters. Subsequently, a ground motion database classified according to four site types based on Chinese seismic design codes is established. Combined with seven single-degree-of-freedom (SDOF) structural models of different periods, the performance of the IMs is comprehensively evaluated from four dimensions: correlation, efficiency, applicability, and completeness. Finally, by comparing the evaluation results under both bilinear and Clough stiffness-degrading bilinear hysteretic models, the robustness of the parameter selection is verified. The results demonstrate that: acceleration-related parameters are most suitable for short-period structures, velocity-related parameters for medium-period structures, and displacement-related parameters for long-period structures. Parameters Sv_avg and Sd_avg exhibit consistent performance across all period ranges and under different site conditions, and the evaluation results remain consistent across different hysteretic models. This study provides a systematic basis for the rational selection of intensity parameters in probabilistic seismic demand analysis, significantly enhancing the reliability and precision of seismic performance assessment. Full article

The optimal performance of buildings strongly depends on their structural configuration, as it influences the structural response to expected loads during life service. For instance, structural arrangements oriented to reduce torsional effects increase performance and, in turn, mitigate vulnerability to seismic events. However, several structural analyses should be performed to ensure that these structural arrangements are robust This can be computationally expensive depending on the type of analysis. The objective of this research is twofold. The first objective is to compare the dynamic response of two reinforced concrete buildings that are almost identical in height and floor area but whose structural elements are placed differently. The dynamic response of both structures was calculated via nonlinear dynamic analysis (NLDA) by considering a large set of ground motion records. Second, NLDA results were compared with those stemming from a spectral-based methodology. The comparison is made on the basis of the fragility and damage functions given different return periods. The results show that an adequate spatial distribution of structural elements reduces materials and increases safety and stability, since the expected damage is lower. Likewise, it is observed that the results based on reduced-order procedures accurately represent those obtained from NLDA while entailing a significantly lower computational cost. Full article

Background/Objectives: Non-invasive methods for evaluating rehabilitation outcomes in Parkinson’s disease (PD) remain limited. This preliminary study proposes a mechanics-informed machine learning (ML) framework integrating force-plate data with dimensionality reduction, clustering, and statistical analysis to objectively assess motor control and the effects of a targeted intervention. Methods: Twelve PD patients were randomly assigned to a PD control group performing standard exercises or an intervention group incorporating additional transverse-plane trunk motion exercises for 10 weeks. Ground reaction forces and center of pressure (COP) signals were recorded pre- and post-intervention using a force plate, alongside data from six healthy individuals as a benchmark. Features related to postural sway and COP dynamics were extracted and refined using Forward Feature Selection. Dimensionality reduction (t-SNE) and unsupervised clustering (K-means) identified group-level patterns. SHAP values and Cohen’s d quantified feature importance and effect size. Clustering robustness was assessed with bootstrapping, nested cross-validation, and permutation testing. Results: K-means clustering revealed clear pre/post-intervention separation in five of six intervention patients, with post-intervention states shifting toward the control cluster. Clustering showed strong performance (Silhouette 0.77–0.79; Calinski–Harabasz 100.8–184.9; Davies–Bouldin 0.29–0.45). The most predictive features (RMS-SML and PL-SAP) showed large effect sizes (Cohen’s d = –12.1 and –4.53, respectively) distinguishing PD patients from healthy controls. Traditional statistical tests (e.g., ANOVA) failed to detect within-group changes (p > 0.05), but ML-based methods captured subtle, nonlinear postural adaptations. Conclusions: This preliminary mechanics-informed ML framework detects PD-related motor deficits and rehabilitation-induced improvements using force-plate data, warranting validation in larger cohorts. Full article

This study aims to explore the seismic performance of large-span concrete-filled steel tubular (CFST) arch bridges under near-fault pulse-like ground motions (PLGMs). Firstly, a deck-type CFST arch bridge located in a high-intensity seismic zone is studied. Three typical near-fault ground motions (NFGMs), namely, forward-directivity pulses, fling-step pulses, and nonpulse ground motions, are chosen for analysis. The effects of pulse characteristics on the seismic responses of the large-span arch bridge are investigated using the nonlinear dynamic time-history analysis method. Subsequently, the near-fault PLGMs are synthesized using the record-decomposition incorporation method, which takes into account the pulse type, seismic source, and site characteristics. The validity of the proposed synthesis method is evaluated from three perspectives: the time and frequency domains of ground motions and dynamic responses of the structure. Finally, the effects of the pulse type, fault distance, moment magnitude, and pulse superposition effect on dynamic responses of the large-span arch bridge are thoroughly studied. The results indicate that the arch bridge exhibits the most pronounced dynamic response to fling-step pulses and moderate responses to forward-directivity pulses, with nonpulse ground motions inducing the weakest response. The three pulse models accurately capture the essential characteristics of NFGMs. Moreover, the synthesized NFGMs, based on the same pulse type, show a high degree of consistency with the actual ground motion results. The dynamic responses are positively correlated with the number of pulse waveforms and the moment magnitude and negatively correlated with the fault distance. The dynamic response is most significant when the peak values of the two types of pulse records coincide. The pulse superposition effect dramatically affects dynamic responses of the arch bridge, so it needs to be fully taken into account in the seismic design of arch bridges. Full article

This study proposes an efficient method for selecting bi-directional ground motions in compliance with the KDS 41 criteria. The proposed method sequentially selects the required number of ground motions from available libraries without exhaustively evaluating all possible combinations, thereby improving computational efficiency. To validate the method, nonlinear response history analyses were performed on multi-degree-of-freedom (MDF) structures using the selected ground motions. The results demonstrate that the proposed method successfully identifies ground motions that closely match the target response spectrum with minimal variance. When selecting between 3 and 6 ground motions, maximum interstory drift ratio (MIDR) is generally overestimated, with errors increasing as the number of motions increases. However, when 7 or more ground motions are used, the mean MIDR errors remain within 20% for most structural models. This improves the accuracy of seismic demand predictions compared to relying on maximum responses from fewer motions. The results confirm the importance of using a sufficient number of ground motions to ensure reliable and efficient analysis. Full article

This paper presents a probabilistic methodology for generating fragility surfaces for low- to mid-rise steel moment-resisting frames (MRFs) under fire-following-earthquake (FFE). The framework integrates nonlinear dynamic seismic analysis, residual deformation transfer, and temperature-dependent fire simulations within a Monte Carlo environment, while explicitly accounting for uncertainties in structural properties, ground motions, and fire simulation. A fiber-based modeling strategy is employed, combining temperature-sensitive steel materials with fatigue and fracture wrappers to capture cyclic deterioration and abrupt failure. This formulation yields earthquake-only and fire-only fragility curves along the surface boundaries, while interior points quantify the joint fragility response under sequential hazards. The methodology is benchmarked against a machine learning (ML) synthesis framework originally developed for earthquake–tsunami applications and extended here to FFE. Numerical results for a three-story steel MRF show excellent agreement (R² > 0.95, RMSE < 0.02) between simulated and ML-generated surfaces, demonstrating both the efficiency and hazard-neutral adaptability of the ML framework for multi-hazard resilience assessment. Full article

This study quantifies the influence of soil–structure interaction (SSI) on key parameters of performance-based seismic design (PBSD) for steel moment-resisting frames. Specifically, PBSD is extended as a methodology in which explicit structural performance levels, such as immediate occupancy, damage limitation, life safety, and collapse prevention, serve as the basis for sizing and detailing structural members under specified seismic hazard levels, instead of traditional force-based design. The PBSD framework is further developed to incorporate SSI by adopting a beam on a nonlinear Winkler foundation model. This model captures the nonlinear soil response and its interaction with the structure, enabling a more realistic design framework within a performance-based context. To evaluate and quantify the influence of SSI in the PBSD method, an extensive parametric study is performed using 100 far-field ground motions, categorized into four groups (25 records each) corresponding to EC8 soil types A, B, C, and D. Nonlinear time history analyses reveal consistent trends across the examined frames. When SSI is neglected, the fundamental natural period (T) is systematically underestimated by approximately up to 3.5% on EC8 soil type C and up to 15% on soil type D. As a result, the base shear and the mean values of maximum interstorey drift ratios (IDRs) are overestimated compared to cases accounting for soil flexibility, with the largest drift discrepancies observed in frames with eight or more storeys on soil D. The analyses further reveal that softer soils (e.g., Soil D) lead to significantly higher q values, particularly for moderate-to-long period structures, whereas stiffer soils (e.g., Soil B) cause only minor deviations, remaining close to fixed-base values. A complementary machine learning module, trained on the same dataset, is employed to predict base shear, maximum IDR, and the behavior factor q. It successfully reproduces the deterministic SSI trends, achieving coefficients of determination (R²) ranging from 0.986 to 0.992 for maximum IDR, 0.947 to 0.948 for base shear, and 0.944 to 0.952 for q. Feature importance analysis highlights beam and column ductility, soil class, and performance level as the most influential predictors of structural response. Full article

In this study, a nonlinear dynamic model is developed to examine the stability and vibration behavior of a self-balancing electric Segway operating over irregular stochastic terrains. The Segway is treated as a three-degrees-of-freedom cart–inverted pendulum system, incorporating elastic and damping effects at the wheel–ground interface. Road irregularities are generated in accordance with international standard using high-order filtered noise, allowing for representation of surface classes from smooth to highly degraded. The governing equations, formulated via Lagrange’s method, are transformed into a Lorenz-like state-space form for nonlinear analysis. Numerical simulations employ the fourth-order Runge–Kutta scheme to compute translational and angular responses under varying speeds and terrain conditions. Frequency-domain analysis using Fast Fourier Transform (FFT) identifies resonant excitation bands linked to road spectral content, while Kernel Density Estimation (KDE) maps the probability distribution of displacement states to distinguish stable from variable regimes. The Lyapunov stability assessment and bifurcation analysis reveal critical velocity thresholds and parameter regions marking transitions from stable operation to chaotic motion. The study quantifies the influence of the gravity–damping ratio, mass–damping coupling, control torque ratio, and vertical excitation on dynamic stability. The results provide a methodology for designing stability control systems that ensure safe and comfortable Segway operation across diverse terrains. Full article