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In seismically active regions, high-filled embankment slopes on liquefiable soils tend to damage after strong earthquakes. Therefore, post-seismic damages should be estimated as soon as possible to mitigate potential losses. Fragility function is an efficient tool for assessing the seismic vulnerability conditions of structures, which links the probability of exceeding different limit states to seismic intensity. An embankment slope on liquefiable soils at Yading Airport in China was selected as the study object, and a series of numerical analyses of the embankment-foundation system utilizing the finite element method were conducted. Advanced dynamic constitutive models considering liquefaction and hysteresis characteristics were also adopted to simulate the nonlinear stress–strain behavior of soils under cyclic loadings. The post-seismic stability of embankment slopes was assessed using the strength reduction method (SRM) based on the stress–strain analysis. On this basis, the permanent ground deformation (PGD) at the ground-free field conditions was selected as the intensity measure (IM), while the factor of safety (FoS) of the slopes was selected as the damage measure (DM). Then, a procedure was presented for deriving seismic fragility functions with different damage states in light of incremental dynamic analysis (IDA). This paper aims to investigate the effects of different embankment typologies, such as the thickness of liquefiable soils and slope inclination, on the post-seismic vulnerability of embankment slopes. The fragility curves constructed in this study may soon be helpful for predicting the post-seismic damage of similar high-filled embankment slopes on liquefiable soils, which enables efficient traffic control and rapid disaster response. [ABSTRACT FROM AUTHOR]

Railway transportation, as an important lifeline during earthquake relief and post-disaster reconstruction, has an extremely significant role. The study of track irregularity caused by earthquakes is the basis for ensuring traffic safety after their occurrence. In this paper, a finite element model of a five-span simply supported high-speed railway beam bridge with the China Railway Track System (CRTS) II was established and an experimental verification was performed. Eighty arbitrarily selected seismic waves were extracted from the Pacific Earthquake Engineering Research Center (PEER) strong ground motion database and a nonlinear time-history analysis was performed on the finite element model. The frequency–domain distribution law of earthquake-induced track irregularities was studied. A stable target earthquake-induced track irregularity spectrum model was constructed, and its expression was fitted. According to the results, in the case of transverse earthquakes, the rails experienced noticeable alignment irregularity and cross-level irregularity, while the amplitude of the gauge and vertical irregularity were relatively small. The target irregularity spectrum has a higher amplitude in the low-frequency components. When peak ground acceleration (PGA) was low, earthquake-induced track irregularity was not obvious, but the deteriorating effects of earthquakes on track irregularities increased significantly with increasing PGA. [ABSTRACT FROM AUTHOR]

For China Railway Track System (CRTS) I twin-block slab tracks, the interface between the sleeper and track slab is susceptible to damage under the coupled effect of long-term train load and external environment factors. In order to analyze the damage behavior and identify the type of debonding at the interface, this paper established a three-dimensional finite element model and introduced the cohesion zone model and concrete damaged plasticity model to simulate the interface damage and the inner-layer damage of the track slab, respectively. The interface debonding induced by the temperature effect was analyzed, and the debonding types were identified based on the obtained vertical vibration responses of the sleeper surface under the train load. The results reveal that the damage mainly occurs on the bottom and lateral sides at the interface under the temperature load. The track model can be refined further to obtain higher analysis accuracy with acceptable calculation time using the sequential loading method. The 26 damage features derived from the time domain, frequency domain, and time–frequency domain are in good representativeness in reflecting the damage information hidden in the vibration signals. Among them, the peak values (maximum vertical acceleration of the sleeper) are 55.0, 56.7, 60.3, and 61.6 m/s2 for no debonding, debonding on the lateral side, debonding at the bottom, and debonding on the longitudinal side of the interface under train load, respectively. Moreover, the identification accuracy of the debonding type can reach 93.75% combining the particle swarm algorithm and support vector machine. It indicates that the proposed identification method is effective and reliable to provide theoretical guidance for developing scientific maintenance and repair strategies for twin-block slab tracks. [ABSTRACT FROM AUTHOR]

This paper performs degradation assessment and safety evaluation of a concrete gravity dam at Shenwo reservoir in Liaoning province of China by using two methods, i.e. deterministic method and probabilistic method, respectively. The deterministic responses of representative sluice piers are computed through static pushover and dynamic analyses. The probabilistic uncertainty analysis, including time invariant and time variant reliability analyses, is based on finite element (FE) reliability theory. For time invariant case, the material and loading parameters are considered as random variables, including elastic modulus, Poisson's ratio, mass density and pushover forces. For time variant case, the earthquake history is simulated by using random process, and the first-order reliability method (FORM) approximation combined with Koo's analytical solution is used to compute the mean upcrossing rate for given performance functions, through which the failure probabilities are calculated. Based on the analysis results using these two methods, the safety and reliability of the dam is assessed. Furthermore, the performance assessments of the dam in its current state are compared with those in the original state (i.e. when the dam was built) to quantify its performance degradation. Finally, the assessment results of using the deterministic and probabilistic methods are compared, and the discrepancies between them are quantified and explained. The computation is based on a general FE analysis platform for earthquake engineering simulation, OpenSees. [ABSTRACT FROM AUTHOR]

The mutation of mass and stiffness between the superstructure and substructure of a hydropower station can lead to the whiplash effect on the hydropower house during an earthquake. This paper explains the mechanism of the whiplash effect based on the theory of structural dynamics. A Chinese hydropower house was taken as a test case to discuss the whiplash effect on this type of structures. An integral finite element model and partial models of the hydropower house were established according to its structural features, arrangement forms and loading features. The dynamic response and the whiplash effect of the hydropower house were investigated by direct time integration using the Newmark method. [ABSTRACT FROM AUTHOR]