In this paper, an innovative self-centering coupled shear link (SC-CSL) used between the steel brace and brace connection plate in the concentrically brace steel frame (CBF) is developed by combining the coupled shear link (CSL), shape memory alloy (SMA) bars and disc springs. Firstly, the hysteresis performance and failure mode of the SC-CSL are analyzed using the validated finite element method. Then, the seismic performances of CBF with a steel brace, CSL and SC-CSL are analyzed. Numerical results show that the innovative SC-CSL has excellent bearing capacity and low residual deformation. The SMA bars mainly sustain tension while the disc springs static under tension force, and the disc springs sustain compression while the SMA bars are static under compression force. The tension and compression forces of the SC-CSL can be almost equivalent with reasonable SMA bars and disc springs. In addition, the seismic performances of CBF, CBF-CSL and CBF-SC-CSL are almost the same, and no yielding or damage occurs to the steel beams, steel columns and steel braces during frequent earthquakes. The steel brace in the CBF has a severe buckling phenomenon. The CBLs with an elastic steel brace can have excellent bear capacity and deformation capacity. The residual deformation of CBF-SC-CSL visibly decreases during rare earthquakes, which shows good seismic performance and seismic resilience capacity.

Grouted sleeve connections are widely used in precast structures due to their excellent connectivity and ease of construction. However, variations in local stiffness within the grouted sleeve region and the relatively weak integrity of the concrete interface at the joint have negatively impacted the seismic performance of precast structures. This paper systematically summarizes the seismic performance tests, theoretical calculations, and numerical analysis of grouting sleeve connection joints, precast assembled components, and precast overall structures. Firstly, this paper elucidates the basic structure and force transmission mechanisms of grouted sleeves while summarizing the critical factors that influence the mechanical performance of sleeve grouted connections. Secondly, the influence laws of the strengthening effect of grouted sleeves on the mechanical properties of precast assembled structures are analyzed. Additionally, the impacts of the arrangement patterns of grouted sleeves and grout defects on the seismic performance of precast structures are investigated. Meanwhile, the calculation methods for the bearing capacities (bending, shear, and torsion) of precast assembled structures connected by grouted sleeves are summarized. Finally, the modeling methods of numerical analysis models for grout sleeve splice and precast assembled components connection with grouted sleeves are analyzed. Based on these, the following researches directions need to be explored: stiffness compatibility between sleeves, steels, and concrete; grouting quality assurance and detection methods; unified constitutive model for grouting material; calculation method for the bearing capacity of precast structure with grouted sleeve connections considering grouted sleeves, concrete, and steels factors.

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.

Currently, the construction of concrete filled steel tube (CFST) arch bridges in China is developing rapidly, and a large number of CFST arch bridges are located in the high-seismicity zones. The seismic resistance issues of CFST arch bridges have received widespread attention. This article first surveyed 360 domestic and foreign research literatures related to the seismic resistance of CFST arch bridges, and provided a macro discussion on their research direction and trends based on the number of publications. Afterwards, the current research progress and shortcomings were summarized in detail from four aspects: seismic simulation and analysis methods, seismic response characteristics, seismic damage analysis, and seismic isolation of CFST arch bridges. Finally, an outlook was made on the issues worth further research on the seismic resistance of CFST arch bridges in the future. The results show that the dynamic analysis method can accurately obtain the seismic response of structures, the coupling behavior of dynamic response amongst components, the optimization and reasonable design method of structural design parameters, the reasonable deployment method of seismic reduction and isolation measures and the mechanism of their impact on structural response, as well as the universal damage assessment process are of great significance for the seismic resistance of CFST arch bridges. In addition, seismic risk assessment, the application of digital technology, and universal research methods and data analysis methods are key areas worth studying in the future. The research can provide a reference for the engineering and academic communities in the seismic analysis, design, and evaluation of existing and pending CFST arch bridges.

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.

The indirect identification of bridge frequencies through coupled vehicle-bridge dynamics is a critical area of research that underpins the health monitoring of bridges. Traditional methods in this domain, however, impose significant constraints on the parameters and operational velocities of the vehicles involved. These restrictions significantly hamper the real-world applicability of these indirect methods since they cannot be smoothly integrated into the analysis of standard vehicles in normal driving conditions. To bridge this gap in the literature and practice, the current study presents a pioneering approach that capitalizes on the dimensionless response of vehicles in transit to indirectly identify bridge frequencies. The research commences by formulating a set of dimensionless equations characterizing the motion of the vehicle-bridge system. From this theoretical groundwork, the study derives a system state equation and an output signal equation, both predicated upon an enhanced subspace identification technique. This study introduces an innovative equation that captures the dimensionless residual response signal from the dual axles of a single vehicle, incorporating temporal variances in the process. This methodological framework successfully negates the adverse impact of road surface irregularities, effectively sidestepping limitations linked to vehicle parameters within conventional subspace identification methods. The versatility of this approach allows for its application to any typical vehicle in motion across a bridge. Then, the study validates the practicality of the proposed indirect approach for the frequency identification of simply supported beam bridges using the dimensionless response of a dual-axle vehicle. Through rigorous numerical analyses, this study examines the influence of driving speeds, road surface conditions, and stochastic vehicle loads on the indirect identification of bridge frequencies. The results highlight the necessity of adequate load excitation to dependably identify bridge frequencies, especially for eliciting the higher-order modal vibrations of bridges, which are essential for accurately identifying modes at higher frequencies. Finally, empirical evidence is provided through field tests conducted on a high-pier simply supported beam bridge. By inputting the monitored dynamic contact force between the vehicle and bridge into the proposed enhanced subspace identification model, this study validates the feasibility and accuracy of this novel approach. The experimental results affirm that the short-time stochastic subspace identification(ST-SSI) technique effectively isolates the first two modal frequencies of the bridge, outperforming the multivariable output error state space(MOESP) method in identifying higher-frequency modes. This research substantially broadens the scope of bridge frequency identification to include standard vehicles within regular traffic flows, simultaneously improving the precision of frequency detection, especially for higher-order modes.

Roller compacted concrete gravity dams have developed rapidly since the 1980s due to their advantage of fast construction speed. Generally, induced joints are set between the dam sections of roller compacted concrete gravity dams and the joints are cut discontinuously with a slotting machine, with the joint surface being non-exposed. The overall seismic response and safety of the dam considering the influence of induced joints are worth attention. This paper proposed a simulation method for the induced joints of roller compacted concrete gravity dams. Established a three-dimensional finite element model of a certain roller compacted concrete gravity dam. Calculated and analyzed the stress, deformation and plastic damage behavior under static and dynamic loads of the overall model of the roller compacted concrete gravity dam and compared it with a single dam section model to study the influence of induced joints on the dam seismic response. The results showed that the stress level and damage degree of the highest dam section in the riverbed are similar under the two models and the seismic responses of the single dam section model were greater in some parts. In addition, the overall model can simulate the damage and cracking process of the induced joints of the roller compacted concrete gravity dam and can more reasonably simulate the overall response of the dam, especially the stress distribution of the dam sections at both dam abutments.

To investigate the seismic response of single-hole with two-track shield tunnels and inside prefabricated internal structures, this paper adopts stratum-structure method and viscous-spring artificial boundaries, utilizing the concrete damage plasticity (CDP) model to structures and establish the finite element models based on the Shanghai airport link line. After simulating, analyzing, and comparing, the seismic response of single-hole with two-track shield tunnels under five earthquakes has obtained. The results reveal that: internal structures, which can effectively increase the lateral stiffness of tunnel and reduce the diameter deformation rate, are beneficial to the seismic performance of tunnel. However, due to the internal structures, the most severely damaged part of the tunnel will change. Although the under-track structure increases the transverse stiffness of tunnel, the side walls on both sides of middle box culvert will be the first damaged parts under seismic wave. The seismic performance of partition walls is the worst among all components, and its response is controlled by the medium to long periods of seismic wave. Damage to the middle partition wall is mainly concentrated on the top and bottom. The seismic performance of the tunnel structure is relatively good, while the seismic performance of the internal structure is relatively poor, especially the middle partition wall. Future design and research should focus on the partition walls.

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.

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.