The China Railway Track System (CRTS II) slab track—a longitudinally connected ballastless system—is widely used in China, with about 7365 km currently in service. In contrast with German ballastless tracks, which cover limited mileage and operate in milder climates, CRTS II slabs in China face large temperature swings and harsher environments, resulting in defects—especially upwarping. This study examines the critical instability mechanism of CRTS II track slabs under thermal loading. First, scale tests measured arch displacement and longitudinal push-slab force while accounting for the rebar‑anchoring system. A mathematical model and simulation model were then developed. To study the dynamic characteristics for upward buckling in longitudinally connected slab track system, a track dynamic response analysis model was constructed that includes the effects of vehicle load, earthquake action, and temperature effect simultaneously. Rail vertical deformation increases nonlinearly with rising temperature, seismic intensity and train speed. When the seismic intensity reaches level 5 with a 60℃ temperature rise, or levels 6-7 with a 50℃ temperature rise, the track experiences upward buckling exceeding 2 mm, necessitating post-earthquake inspection and repair. Adopting moderately reduced fastener stiffness, track slab elastic modulus, the elastic modulus of the CA mortar layer, enhances seismic resilience in ballastless track design.

The correlation between seismic intensity measures (IMs) and structural response is crucial in accurately assessing the seismic performance of reinforced concrete (RC) frame structures. However, the correlation analysis using either nonlinear dynamic analysis (NDA) or common machine learning (ML) methods is time-consuming. To address these challenges, this paper proposes an ML-based method to accelerate the correlation analysis process using the recently developed low-rank matrix guided least-squares support vector machines for regression (LRLS-SVMR). Given a large-scale seismic response data set, the proposed method first employs LRLS-SVMR to extract features with a lower dimension. Then, a parametric prediction model can be learned from the data set, where the inputs are the extracted features and the output is the structural response quantity. The computational complexity of the learning process is only proportional to the dimension of the features and irrespective of the number of training data points. The proposed method is applied to the correlation analysis between IMs and structural response for three typical RC frame structures, considering different damage levels due to longitudinal reinforcement buckling. The prediction accuracy and computational efficiency of the proposed method are validated by comparisons with other widely used ML methods based on a large-scale data set covering 30,219 data points generated by the NDAs on the mentioned RC frame structures. The research findings show that the peak ground velocity correlates best with the maximum interstory drift ratio (MIDR), followed by spectra acceleration at the first period, peak ground displacement, and peak ground acceleration. Moreover, the structural damage due to longitudinal reinforcement buckling has a relatively small impact on the correlation between the mentioned IMs and the MIDR.

The damping model can influence the results of seismic response analyses of structures. This effect is particularly pronounced under elastic and weakly nonlinear conditions, where damping-induced energy dissipation plays a crucial role and directly affects the structural response. Moreover, the influence of damping models may vary depending on the characteristics of ground motion excitations. Conventional viscous damping models may involve mass-proportional and geometric-stiffness-proportional components, which are associated with incorrect dissipation of energy in rigid-body modes. This issue is especially relevant for base-isolated buildings, where rigid-body motions can be substantial. In response to these limitations, recent research has proposed new complex damping models for time-history analysis. This study investigates the effects of different damping models on isolated structures by comparing the performance of uniform damping (a type of complex damping) with that of Rayleigh damping (a type of viscous damping). The evaluation is conducted using 30 near-field and far-field ground motions. First, the impact of damping models on response spectra for various damping ratios is examined. Then, dynamic responses of typical seismically isolated composite frame structures using different damping models under different ground motions are analyzed and compared. The results indicate that higher-order structural responses, such as acceleration, are more sensitive to the choice of damping model than lower-order responses like displacement. Specifically, uniform damping tends to produce larger acceleration responses. The differences between the models increase with the damping ratio; for instance, at a damping ratio of 30%, acceleration response spectrum differences can exceed 70% at certain periods. Additionally, Rayleigh damping results in more than 10% smaller deformation estimates for seismic isolation bearings, potentially leading to unconservative designs.

Seismic risk assessment for residential buildings is a priority in Eastern Canada, given its densely populated cities and history of earthquake activity. A crucial component of this assessment is the development of an accurate and practical inventory model, which relies on comprehensive investigations and the collection of reliable data on residential buildings. A simple yet reliable inventory framework is essential to streamline the process of building inventory while reducing costs and time. Moreover, there is a need for more refined and standardized classifications of the structural systems of residential buildings. This study proposes a new inventory modelling framework for residential buildings, applied to Montreal as a case study, with a focus on the number of residential units. The two main objectives of this study are: (1) to conduct a historical review of residential construction practices in the city, defining common materials and structural systems; and (2) to determine their distribution across administrative areas, including both independent municipalities and boroughs within the City of Montreal. To achieve these objectives, previous studies and various pertinent resources were evaluated to trace the evolution of residential construction, and two open-access databases were employed and integrated to derive results. The analysis covers over 900,000 residential units, revealing that approximately 30% and 22% are associated with buildings constructed using wood light frames and concrete shear walls, respectively, while 48% correspond to buildings with mixed wood-masonry structural systems as well as masonry buildings. This inventory model offers practical insights into the distribution of residential units by structural systems, improving future simulations to estimate uninhabitable unit rates, population displacement, and shelter needs, which will support and strengthen community resilience.

The dynamic lateral pressure on silo wall generated by stored materials under earthquake sequences effects is a critical factor affecting silo safety. In this paper, a series of shaking table tests were conducted on a 1:20 scale plexiglass silo model under empty, half-filled, and fully filled conditions to investigate the dynamic lateral pressure distribution and strain response under earthquake sequences. The earthquake excitations of the 1940 El-Centro earthquake (El), the 1952 Taft earthquake (TF), and an artificial wave (AW) were selected and used in the shaking table tests. The test findings show that in the lower third of the silo, the stored materials and the silo structure move in sync, greatly reducing the dynamic lateral pressure in this region. Consequently, the lateral pressure on the silo side wall is lower than the internal horizontal pressure. As the storage height increases, the lateral pressure at the silo center becomes lower than the lateral pressure at the silo wall, indicating that the increased storage mass triggers internal force redistribution within the granular material. Under identical filling conditions and mainshock peak ground acceleration (PGA), the overpressure coefficient varies non-uniformly with silo height. The maximum value occurs at 1.6 m from the base (upper region), primarily due to dynamic material-wall interactions at the top during seismic excitation. Under identical mainshock-aftershock sequences, the strain response of the silo increases with both storage mass and PGAs, demonstrating significant correlation with filling conditions. The lower silo region represents a critical zone where relative motion between the stored materials and silo wall induces abrupt stiffness variations and potential structural damage. The test results can provide references for the seismic design of silos.

In existing studies, researchers tend to use peak values as indicators that directly reflect the time-frequency characteristics of structural responses. However, there is limited research on the time-frequency analysis of structures considering soil-structure interaction (SSI), making it difficult to intuitively obtain information about structural vibration intensity, fundamental frequency, and duration. Therefore, using the results from a previously conducted shaking table test of a 12-story frame structure with SSI effect, wavelet analysis is employed to perform wavelet packet transformation on the time-history response signals of the frame model. This process obtains the corresponding time-frequency relationship and the maximum energy variation index of each floor, which can reveal the variation patterns of structural responses in the time and frequency domains comprehensively, and evaluate the structural damage state under various earthquake excitations. In this present study, the experimental results of the 12-story frame structure are further analyzed in time and frequency domains, decomposition and reconstruction of acceleration responses, energy distribution of each frequency band, and total energy ratio. The results show that, firstly, the shallower the depth of the soil, the larger the seismic response, and the response at the pile foundation is larger than that at the free field, indicating that SSI effect amplifies the response of the soil. Secondly, the acceleration amplitude of the SSI system is smaller than that under fixed-base condition, and the SSI effect reduces the overall energy of the structure. Finally, the middle levels of the structure have the largest probability of maximum energy variance index, therefore appropriate strengthening measures should be considered in the seismic design of the structure.

Hydraulic structures subjected to prolonged operational conditions inevitably experience damage and potential structural resonance, which threaten their stability and safety. Structural health monitoring (SHM) is a well-established approach to ensuring safety; however, conventional methods primarily rely on contact sensors, which are inadequate for comprehensive monitoring of large and complex structures. Video-based noncontact monitoring techniques effectively address this limitation. This study proposes a field-deployable, phase-based video method to measure micro-vibrations of large hydraulic structures. Rather than batch processing full frames, vibration time histories are extracted from user-defined pixels or pixel groups, enabling efficient region of interest (ROI)—level analysis with synchronized high-speed videos. We then assess the method's robustness under varied illumination conditions, shooting angles, and scales, and visualize micro-motions using frequency-selective motion magnification. On an aging aqueduct, video-derived responses show strong agreement with those obtained via displacement sensors; the correlation coefficient with sensor data reaches up to 0.96, accurately capturing the spectral peak bands within the 0-100 Hz and demonstrating exceptional robustness in the 0-20 Hz. Based on the discussion of practical limits, we provide guidelines for low-texture, large-scene monitoring. Adequate and uniform illumination is essential, and local fine-scale features can significantly improve accuracy. The correlation coefficient can be increased by 0.1-0.3. Perpendicularity between the shooting angle and the target vibration direction is critical for obtaining high-precision data.

A large-span atrium-type subway station structure (LASS) using Y-shaped cast steel combined with steel tubular columns (YSTC) as the support system (Y-LASS) was proposed and applied. Departing from the traditional medium plate structure, the LASS adopts an innovation space system that combines the platform floor and hall floor to achieve a large space architectural effect for subway station. To evaluate the seismic performance of the LASS, the bearing capacity and yield process of the YSTC were analyzed through quasi-static tests, while the seismic response was studied through shaking table tests. The results indicate that the Y-LASS exhibits superior seismic performance. When the inter-story drift angle achieved 1/50 during repeated loading, the YSTC began to yield from its bottom portion; As horizontal lateral displacement increased, no reduction in the structural bearing capacity was observed, but the stress at the weld between Y-shaped cast steel and steel pipe column was close to the yield stress. Under the seismic action, the maximum strain of the YSTC appeared in the middle of the lower column and was higher than the side wall, where the seismic resilience needed to be strengthened. As the burial depth reduces, the seismic response of the rest of the station structure intensifies. The results offer valuable insights and practical guidance for the reasonable design and structural safety assessment of similar subway station structures.

To optimize the connection between the beam and the concrete-filled steel tubular flat column (CFSTFC), a new connection using the vertical internal plates as stiffeners was proposed. In this paper, the seismic performance of the joint in the center column was studied by the quasi-static test of two middle joint specimens with 10-mm-thick and 14-mm-thick steel tubes. The failure of the joint was concentrated in the beams, and the CFSTFC remained elastic. The tested joint showed good seismic performance. Changing the thickness of a steel tube has little influence on the stiffness, strength, and ductility of the rigid joint. Then, the influence of the axial compression ratio on the seismic performance of the joint was investigated by finite element analysis. With the axial force increasing, the seismic performance of the joint gradually decreased. Finally, a simplified fiber element model of the joint was proposed and validated by the test and solid element model results.