Earthquake Engineering & Structural Dynamics最新文献

Real-time hybrid simulation (RTHS) integrates numerical simulation and physical experiment to provide an effective and efficient technique for large- or full-scale testing in size-limited laboratories. Real-time hybrid simulation with model updating (RTHSMU) further expands RTHS beyond the laboratory capacities. Numerical substructure parameters are corrected by model updating based on test data acquired from the experimentally tested physical substructure. Structures with multiple similar critical components can then be tested in a more economical and efficient way. This study presents a new model updating method for RTHSMU based on efficient global optimization (EGO). Kriging meta-model is used to construct the complex relationship between constitutive parameters and structural response errors. EGO and moving window techniques are integrated to identify model parameters to achieve efficient adaptive sampling with minimal computational cost. A two-story steel moment resisting frame with self-centering viscous dampers is used to experimentally verify the efficacy of the proposed method. Compared with widely used unscented Kalman filter, the proposed method has advantages of ease of use and shows similar or better performance. Identified parameters from the proposed method are further shown to effectively improve the accuracy of structural responses under different ground motion excitations.

This study investigates the application of ordinal regression models in seismic fragility curve modeling, providing a flexible alternative to the traditional log-normal distribution function. A comparative analysis is conducted among various ordinal regression approaches, including the traditional Cumulative model as well as alternative methods like Sequential and Adjacent Category models, along with extensions that account for category-specific effects and heteroscedasticity. These models are applied to bridge damage data from the 2008 Wenchuan earthquake, using both frequentist and Bayesian inference methods. Model diagnostics, including surrogate residuals, are performed to assess model fit and performance. A total of eleven models are examined, from basic forms to those incorporating category-specific effects and variance heterogeneity. The Sequential model with category-specific effects, rigorously evaluated using leave-one-out cross-validation, outperforms the traditional Cumulative probit model. The findings highlight significant differences in the predicted damage probabilities, emphasizing the potential of more flexible fragility curve modeling techniques to improve seismic risk assessments. This study underscores the importance of ongoing evaluation and refinement of modeling techniques to enhance the predictive accuracy and applicability of seismic fragility models in performance-based earthquake engineering.

The current centrifuge and shaking table test for a shield tunnel is constrained by the equipment available, leading to a low similarity ratio between the test model and an inconsistent relationship between the soil and structure. Hence, the design of a steel frame, composed of steel plates and springs, has been proposed as an innovative loading device for performing shaking table experiments on large-scale shield tunnels. The proposed loading device, inspired by the response displacement method, incorporates the steel frame to provide support for the tunnel model and transfer the seismic loading from the shaking table, while the springs serve as a representation of the soil-tunnel interaction. In order to validate the accuracy and effectiveness of the loading device, the device, and tunnel are simplified as Euler-Bernoulli beams and linked together with springs to establish an analytical model, and the high-order partial differential equation of the beam is solved to derive analytical solutions for the device and the tunnel. Furthermore, results from the numerical analysis and geotechnical box test on a shaking table system have also been obtained. Based on these results, the loading device is proven to be an effective method of applying seismic loading to the tunnel while maintaining its stability. With the use of the loading device, the shaking table test for a large-scale shield tunnel could be successfully executed, resolving the issue of mismatched similarity between the soil and tunnel model.

The realistic prediction or simulation of the seismic behaviour of critical structures is highly sensitive to many aspects, including the earthquake source, propagation path, region topography, geological conditions and local complex structural dynamic analysis system. However, integrating the above key factors in a framework for generating realistic ground motions (GMs) and conducting dynamic analyses at specific engineering sites remains challenging. This task necessitates assessing the crucial elements involved in the seismic design of hydraulic tunnels (HTs), with the ultimate objective of safeguarding human lives in areas prone to seismic activity. To achieve this objective, a multiscale framework leveraging the spectral element method (SEM) and finite element method (FEM) is proposed. This framework involves establishing a coupling strategy between the SEM and FEM to address geological media–structure interaction problems. The SEM is utilised to generate and propagate elastic waves within the soil, while the FEM allows the studied structure to be comprehensively represented. The coupling technique is implemented using the weak-coupling strategy in conjunction with the time domain reduction method (DRM). Then, a series of dynamic analyses and seismic performance assessments of the HT with the coupling SEM-FEM method are conducted. The results indicate that (1) the nonlinear dynamic responses of the HT induced by the physical-based GM align with the recorded GMs, verifying the practicability of the proposed framework for source-to-HT simulation; (2) physical-based GMs of the hanging wall and foot wall, rupture fault distances and mountain locations can significantly impact the seismic performance of HTs.

This study introduces an energy-based framework for rapidly assessing damage and fragility in regional buildings under mainshock-aftershock sequences. First, the ultimate energy of the structure is derived from the relationship between two time-varying parameters: effective intrinsic energy and input energy. An energy-based damage index is then defined, with uncertainties of the structure and earthquake quantified through Latin hypercube sampling. Subsequently, a Gaussian Process model, enhanced with K-Means clustering and Bayesian optimization, is employed to predict the structural ultimate energy. A Convolutional Neural Network-Long Short-Term Memory Network with an Attention mechanism model with a weighted loss function is developed to capture the structural energy time-history responses, integrating correlation analysis and hyperparameter optimization. A comparative analysis is performed with previous machine learning models. The framework's effectiveness is validated through a comparative study with the inter-story drift ratio (IDR) index. Finally, the framework is applied to Zeytinburnu in Istanbul, Turkey. The results indicate that reducing the dimensionality of the database through correlation analysis effectively decreases data dimensions while maintaining accuracy. In rapid damage assessment tasks, energy is a superior damage indicator compared to IDR, as it correlates positively with critical parameters such as building height and peak ground acceleration (PGA). It enables a tenfold reduction in response data, enhancing training efficiency by 7.4 times. PGA_as/PGA_ms of 1.0 is recommended for analyzing mainshock-aftershock effects, providing a more comprehensive perspective on structural performance and ensuring a conservative estimate of regional structural fragility.

Freestanding artifacts are carriers of cultural heritage, and earthquake damage should be avoided as much as possible. Seismic mitigation measures for lowering the center of gravity (CG) by filling a mass have not been well investigated. Using a ceramic vase as a typical artifact object, the correlations between the location of the CG and the filling material were analyzed, and lead beads were determined to be the candidate material for the experimental and analytical investigations. Rectangular rigid block models of the vase with and without mass filling were constructed for rocking analysis. Comparative free-rocking and shaking-table tests were performed on vases with and without mass filling. Mass filling can reduce the coefficient of restitution, free-rocking time duration, and quarter period while increasing the damping ratio. Instrumented earthquake records from a seven-story building were employed in the comparative shake table tests of the vases. The filling mass considerably reduced the rotation and displacement amplitudes compared with those of the empty vase, whereas the reduction in the acceleration amplitude was not as apparent. The experimental and computational results for each test series were identical. Fragility curves were constructed using the shaking-table testing results. Analytical results were obtained utilizing additional instrumented earthquake records experienced by the building. Given the peak floor acceleration, the probability of failure of the filled vase was reduced compared with that of the empty vase. The effect of the story level on the probability of failure was not prominent. This study is advantageous for the seismic mitigation of various freestanding artifacts in buildings and other nonstructural components.