Aiming at the problems of random failure position, large amount of steel cutting and excessive welding length of traditional cross-core concrete-filled steel tube buckling-restrained brace ( CSBRB), a new type of perforated cross-core concrete-filled steel tube buckling-restrained brace (PCSBRB) is proposed in this paper. The structure and characteristics of PCSBRB are introduced, and the calculation equation of basic mechanical parameters is given. Six groups of PCSBRB models with different opening parameters and one group of CSBRB models are designed, and the quasi-static finite element analysis is carried out by ABAQUS software. The effects of the structural rationality of PCSBRB, the opening ratio and the number of openings on the mechanical properties, energy dissipation performance, stress distribution, high-order deformation characteristics, in-plane instability of the opening section and the equivalent cumulative plastic strain of PCSBRB are studied. The analysis results show that the structure of PCSBRB is reasonable, and the bearing capacity and energy dissipation performance are similar to those of CSBRB. The yield area of PCSBRB is located in the opening section, which has the advantages of fixed-point yield and multi-point energy dissipation. The hysteresis curves of PCSBRB with reasonable design is stable, full and symmetrical. For PSCBRB with too small opening rate, the stress is concentrated at the limit hole, and the purpose of fixed-point yielding cannot be achieved. For PCSBRB with too large opening rate, the opening section is prone to in-plane instability, resulting in a decrease in the bearing capacity of PCSBRB. The opening rate of PCSBRB should be 33%~50%. When the total length of the opening section is 1500 mm, the number of openings is set to 4~8, and the performance is similar. Compared with CSBRB, PCSBRB has higher material utilization and lower welding cost.

On December 18, 2023, a magnitude 6.2 earthquake occurred in Jishishan County, Gansu Province, with a maximum intensity of Ⅷ degrees. In order to analyze the damage characteristics of different structural types of buildings constructed by the standard and self-built methods in the townships, a seismic damage survey was conducted on the buildings in the macro-seismological center of the earthquake-Dahejia Town. The typical seismic damage characteristics of reinforced concrete shear wall structures, masonry-concrete composite structures, reinforced concrete frame structures, and other structural types were summarized, and the causes of damage were analyzed. The results of the investigation and analysis show that the standard-built masonry-concrete composite structures and reinforced concrete shear wall structures suffered minor damage as a whole, which does not affect the continued use of the buildings. The load-bearing columns and beams of the standard-built frame structures are basically intact, but the infill walls are severely damaged, which affects the use of the building and the cost of later repair is relatively high. The self-built buildings are more severely damaged than the standard-built buildings, and the damage patterns are complex and diverse, which seriously affects the production and life of the residents. In view of the many problems in the earthquake-resistance of township houses, it is suggested that the relevant government departments organize professional units to carry out appraisal of existing buildings and provide multiple sets of repair and reinforcement schemes. For new and under-construction self-built houses, the regulatory intensity should be increased, and the professional skills of the personnel involved in house construction should be enhanced through training. For the urgently developing and constructing township areas, the relevant departments should strictly follow the relevant regulations of the seismic code, take the lead in the construction of civil houses, and improve the overall seismic capacity of the region.

To address the issue of the single energy dissipation form of traditional metal dampers, this paper proposes a new type of metal-double hinge friction hybrid damper, leveraging the characteristics of large yield displacement in bending metallic dampers and small yield displacement in rotational friction dampers. The construction principles and main parameter calculation methods of the hybrid damper are elaborated to achieve the objective of phased energy dissipation from frequent earthquakes to the maximum considered earthquakes. Experimental research on the mechanical performance of the hybrid damper was conducted, comparing the hysteresis curves, strain development, stiffness degradation and energy dissipation capabilities of dampers made of LY160 and Q355 steel materials and in different construction forms. The results show that the hybrid damper has good energy dissipation performance, with fuller hysteresis curves compared to traditional metal dampers. Within the range of metal yield displacement deformation, the damper primarily dissipates energy through friction, exhibiting multi-level yielding characteristics and a higher equivalent viscous damping ratio. The restoring force model for the hybrid damper is proposed and verified with experimental results. By adjusting the parameters of the metal damper and the double hinge friction damper, a performance-based design can be achieved to meet the seismic demands of various application scenarios. A new type of metal-double hinge friction hybrid damper has been developed.

It is crucial to quickly and accurately assess the losses for post-disaster relief and reconstruction after earthquake disasters. This article focuses on the research of normalized business requirements for earthquake on-site disaster loss investigation and assessment. By establishing a unified earthquake on-site disaster loss investigation and assessment system, it optimizes the information transmission process at the earthquake on-site, improves the timeliness of earthquake information transmission, and achieves the flattening of survey data collection, analysis, and management. Through the implementation of functions such as calculating the earthquake damage index of sampling points, comprehensively evaluating the intensity map, and semi-automatically generating assessment reports, the system improves the efficiency of earthquake disaster response and the accuracy of disaster loss assessment, providing strong guidance and a basis for post-disaster reconstruction. At the same time, the accumulation and analysis of earthquake on-site loss investigation and assessment cases serve as a reference for future emergency response and risk assessment. Finally, this article also presents further research throughts and methods to gradually improve the system’s functionality, rendering it more practical and sustainable.

The pile-columns of frame piers is a widely used substructure in bridge engineering. The current seismic design specifications for bridges require the pile to remain elastic following the capacity protection principle. Therefore, identifying the sensitivity of various design parameters to seismic demands of the piles is an important prerequisite for the capacity protection design of the piles. For this purpose, based on a coupled soil-pile-structure finite element modeling method, the sensitive parameters of pile-columns of frame piers to pile seismic demand are studied. Firstly, distribution mechanisms of bending moment under different earthquake intensity are investigated, together with understanding the contribution of ground surface tie beam to withstand the pile-shaft bending moment. On this basis, standardized seismic demand indicators representing the maximum bending moment of the pile, the corresponding depth, and the recommended reinforcement range are proposed. The sensitivity of tie beam, pile, column and soil parameters to the seismic demands of piles is analyzed. Based on the sensitivity parameter definition standards derived in this paper, the high and low sensitivity parameters of the pile seismic demand are identified. The research results can provide a reference for the seismic design of bridges supported by extended pile-shaft frames with ground surface tie beams in cohesionless soils based on pile capacity protection principle.

The response spectrum is a crucial foundation for seismic design. The constitutive models of traditional numerical simulation methods fail to adequately capture the complex site conditions and dynamic processes of soil with high uncertainty, which causes significant discrepancies between calculated and measured response spectra. This paper used 2428 sets of bedrock and surface seismic records from horizontal site stations by KiK-net in Japan. It established a BO-XGBoost-SS model for predicting ground acceleration response spectra, taking soil layer information and bedrock input as primary features through a stratified sampling training strategy guided by site categories. Results demonstrate that the constructed model exhibits good predictive performance, with an R² evaluation metric of 0.87 for surface acceleration response spectrum, with R² values above 0.8 for various periods. Applying dynamic time warping (DTW) distance analysis to assess the prediction match of individual response spectrum, the model proposed shows stability across different site categories, overcoming the deficiencies of numerical methods in underestimating high-frequency ground motion and anomalously amplifying long-period response spectrum. Validation with the latest ground motion records as an external dataset further confirms the model’s generalization ability. Through shapley additive explanations (SHAP) analysis, the contributions of features to model predictions are elucidated, revealing key features influencing response spectrum predictions, consistent with existing knowledge. The study’s findings provide training strategies and assessment guidance for the development of site response prediction models, offering new insights into the application of machine learning in seismic zoning and earthquake-resistant design of engineering structures.

Strong ground motion data serve as the basis for establishing ground motion models. It is difficult to establish ground motion models in areas lacking sufficient strong motion data. This paper reviews several methods for establishing ground motion models in areas lacking strong motion data, including the numerical simulation method, the hybrid empirical method, and the referenced empirical approach. The numerical simulation method employs high-frequency and low-frequency ground motions simulated by stochastic and deterministic methods, respectively, to develop ground motion models. The hybrid empirical method can effectively solve the problem of lack of data by combining numerical simulation and actual observation data and applying the empirical ground motion model of the reference area to the target area by using the adjustment factor. The referenced empirical approach is based on the small earthquake records in the study area and adapts the existing empirical ground motion model to suit the specific regional situation with simplicity and effectiveness. Each of these three types of methods has its own characteristics, numerical simulation methods can take into account the characteristics of the seismic source, complex geological and site conditions, and the calculation results depend on the accuracy and precision of the source model and the subsurface velocity structure. The hybrid empirical method combines the flexibility of numerical simulation methods and the statistical characteristics of observed data, and can establish a relatively reliable model. The referenced empirical approach is quicker and simpler but is dependent on the data of the small earthquakes. Finally, this paper suggests that artificial intelligence and multi-source data fusion can be used to improve the accuracy and reliability of ground motion model in areas lacking strong motion data.

Humanity’s demand for nuclear energy has driven its development, yet the frequent occurrence of nuclear accidents has emphasized the crucial importance of safety. Earthquakes, especially near-field earthquakes, pose a substantial threat to the safety of large structures, such as nuclear power plants. Traditional seismic response analyses of nuclear power plants often depend on the assumption of vertical incidence of input motions. However, near-field earthquakes predominantly exhibit oblique incidence, resulting to more intricate and diverse effects. This paper realizes the simulation of obliquely incident ground motions by using the three-dimensional visco-spring artificial boundary method to build a comprehensive model of the nuclear containment structure and its surrounding soil. Subsequently, two typical input motions—P-waves and SV-waves—are selected and input into the model at varying angles of incidence to conduct an in-depth analysis of the seismic dynamic response of the nuclear containment shell. Based on the research results, it can be observed that the dynamic response of the nuclear containment shell under near-field earthquakes exhibits more complicated characteristics, which cannot be entirely captured by assuming vertical incidence of input motions. This finding emphasizes the significant impact of near-field seismic motion patterns on the dynamic response of nuclear power structures, providing quantitative insights and valuable references for the seismic design and optimization of similar projects.

There are various liquefaction assessment methods empirically based on test data used both domestically and internationally. Among them, the cone penetration test (CPT) has become a common method due to its inherent advantages. This paper elaborates on four commonly used CPT-based liquefaction assessment methods from both domestic and international sources: the NCEER method, the Code for investigation of geotechnical engineering method, the Specification for geotechnical invesitgation in soft clay area method, and the General rules for performance-based seismic design of buildings method. It compares the assessment results of these methods and utilizes data-driven classification and regression tree (CART) and random forest (RF) algorithms to study and analyze the importance of liquefaction influencing factors and the interplay among them. A new set of standards for determining liquefaction occurrence was developed, showing that: The General Rules method proposed by YUAN Xiaoming et al. is balanced with the highest accuracy for liquefaction assessment, achieving over 94% accuracy in seismic intensity zones of 7, 8 and 9, which is higher than the NCEER method, and significantly better than the Geotechnical Specification and Soft Soil Procedure methods. The NCEER method, though ranking second best, tends to misclassify a large quantity of non-liquefaction data as liquefaction in deeper layers of intensity zone 9, which is not consistent with reality. The performance of the Geotechnical Specification and Soft Soil Procedure methods is the worst. The accuracies of the two machine learning methods are 97.6% and 97.5% respectively, with the importance ranking of predictive variables being largely consistent. Factors such as relative density (D_r), soil behavior type index (I_c), fines content (FC), and cover thickness (CT) have a significant impact on triggering liquefaction, whereas peak ground acceleration (PGA), groundwater table (GWT), and critical thickness of the liquefiable layer (CTL) have a lesser impact. The proposed new standards for liquefaction triggering are in line with the impact trends of various influencing factors, providing references and support for the prediction and assessment of liquefaction triggering.

To address issues such as excessive displacement and inadequate self-resetting capabilities in isolated bridges employing traditional double concave friction pendulum bearings, a novel iron-based shape memory alloy-double variable friction pendulum bearing (Fe-SMA-DVFPB) was developed. This bearing integrates the variable friction mechanism on the sliding surface with the superelastic properties of shape memory alloy. A constitutive model for the bearing is established, and its equivalent analysis model is determined through theoretical analysis and numerical simulation. Based on practical engineering considerations, isolated bridges with different types of bearings are designed, and their seismic performance under near-fault ground motions is analyzed. The results show that the maximum isolator displacements of the three types of isolation structures under pulse-type earthquakes are 2.1, 1.63 and 1.47 times greater than those under non-pulse-type earthquakes, respectively. Compared to DCFPB-isolated bridges, Fe-SMA-DVFPB-isolated bridges exhibit the maximum reduction in isolator displacement of 38.9% under pulse-type earthquakes and 13% under non-pulse-type earthquakes. Additionally, the maximum reduction in residual displacement is 93.5% for pulse-type and 83.1% for non-pulse-type earthquakes. The use of Fe-SMA-DVFPB significantly improves control over both relative displacement and residual displacement. The reduction in relative displacement and residual displacement in Fe-SMA-DVFPB-isolated bridge bearings is significantly greater than the increase in bending moment and shear force at the pier base. Fe-SMA-DVFPB can further enhance the post-earthquake resilience of bridges.