The urban lifeline engineering system, serving as a key infrastructure that ensures the daily lives of residents, the functional operation of the city, the healthy development of the economy, and the long-term stability of society, is the cornerstone of resilient city construction. Research on seismic resilience assessment methods for urban lifeline engineering systems has achieved certain progress both domestically and internationally. However, the seismic resilience design methods for urban lifeline engineering systems remain underdeveloped. This paper expounds on the concept of seismic resilience design for urban lifeline engineering systems and delineates the differences between seismic resilience design for urban lifeline engineering systems and traditional seismic design for individual urban lifeline facilities. The basic framework of seismic resilience design, characterized by the “two dimensions”, is put forward, which ensures the structural seismic safety of individual facilities through the structural safety design of individual facilities, and guarantees the post-earthquake functionality and rapid recovery of the engineering system through the resilience coordinated design among individual facilities. The basic requirements for seismic resilience design, characterized by the “three objectives”, are established, ensuring structural seismic safety of individual facilities, meeting predetermined functionality of individual facilities and the engineering system, and enabling rapid recovery of the engineering system. The key steps of seismic resilience design, characterized by the “four components” are proposed, which include determining the seismic resilience goals for the engineering system, structural safety design for individual facilities, post-earthquake functionality verification for the engineering system, and identification of technologies and strategies for the rapid recovery of the engineering system. A unified seismic resilience design approach for urban lifeline engineering systems is established. This paper takes a road transportation system as an example to conduct seismic resilience design. The preliminary results validated the rationality and feasibility of the proposed seismic resilience design approach. The design approach enables the transition of seismic design for urban lifeline engineering systems from structural seismic design, which ensures the structural seismic safety of individual facilities, to seismic resilience design, which ensures post-earthquake functionality and rapid recovery of the engineering system. The proposed approach can also provide a practical solution to improve their seismic resilience.

Due to the influence of topography and traffic routes, small radius curved bridges with eccentrically support piers and variable pier heights are widely used. Due to the irregularity of the bridge caused by the difference in pier heights and the eccentric supports, a complex stress form of pressure-bending-shearing-torsion coupling in the eccentrically support pier will occur. Taking an interchange ramp bridge as the engineering background, a centralized hinge-fiber model based on nonlinear finite element software was constructed. The seismic vulnerability of eccentrically compressed piers in two models was compared by adopting the incremental dynamic analysis method. These two models include a model with the concave-type variable height piers (the CTVHP curved bridge) and a model with gradient variable height piers (the GVHP curved bridge). The results show that: in the small radius bridge with eccentrically support pier and variable pier heights, the probability of torsional damage of the intermediate pier is higher. When the pier torsional damage occurs, the exceeding probability of each pier damage level in the CTVHP curved bridge is greater than that in the GVHP curved bridge, which will lead to more serious torsional damage. Therefore the arrangement of the CTVHP curved bridge should be avoided in seismic design, at the same time, the seismic capacity of the intermediate pier should be enhanced. The research results of this paper can provide a basis for similar bridges.

The main task of the building structure array is to record the failure process of civil engineering structures in detail, and to provide structural response information for many related studies such as seismic design, seismic damage assessment, and earthquake safety alarm. However, due to the constraints of economic cost, field testing technology and data processing level, it is unrealistic to deploy sensor monitoring equipment on all floors of the entire structure, so how to obtain the most complete structural information with the least number of sensors is the purpose of optimizing the layout of structural array sensors. Considering the advantages and disadvantages of the effective independent method and the modal kinetic energy method, a unit stiffness energy-driving point retention method was proposed, considering the advantages and disadvantages of the effective independent method and the modal kinetic energy method. In this method, the unit stiffness modal energy is used as the information matrix, and the principle of effective independence method is used to screen the measurement points, so as to ensure that the high-energy measurement points maintain linear independence to the greatest extent. Finally, taking a steel frame as an example, the proposed method, the effective independence method, the modal kinetic energy method and the unit stiffness method are used to lay the sensors on the model respectively, and the modal assurance criterion and the Fisher information matrix criterion are used to evaluate the layout results of the four methods. The results show that, compared with the other three methods, the proposed method has the least number of sensors when the mode vectors are linearly independent, and the proposed method can obtain the most modal information with the same number of sensors.

In order to reveal the damage mechanism of ancient timber structures and to make a reasonable evaluation of the damage degree under earthquakes, this paper proposes a multi-scale seismic damage evolution analysis method for the ancient timber structure. Based on the generalized force-deformation relationship and performance-based seismic design, the generalized damage index is established through test data fitting analysis, thus multi-scale consistency damage indices are proposed. According to the multiple point constraint method (MPC), a multiple-scale model is developed for ancient timber structures, which can reveal macro mechanical properties and local failure details. The proposed damage evolution analysis method is validated by a cyclic loading test of mortise-tenon joint and a shaking table test of the multi-story timber framework, and the evolution process and results are also shown. The proposed multi-scale analysis method provides evaluation results of seismic appraisal for existing ancient timber structures, including assessments at the local material, component to overall structural levels. Furthermore, it elucidates the evolutionary relationships between each level of the whole structure, providing a scientific basis for reinforcement and repair work.

The slopes of hydropower projects in southwest China are high and steep and located in high seismic intensity regions. Consequently, there is a risk of earthquake-induced slope instability. Taking the drainage building intake slope of Lawa Hydropower Station at Jinsha River as an example, the dynamic finite element method is used to simulate the slope under rare strong seismic conditions. Based on this, an analysis of the slope dynamic response is conducted. Then, the post-earthquake slope deformation, stress and plastic zone distribution are studied. Finally, the dynamic stability of the slope below the spillway structure is evaluated using the dynamic strength reduction method, which reveals its potential instability mechanism. The results indicate that the acceleration response of the slope shows an elevation amplification effect, a surface amplification effect and a structural surface amplification effect. The slope undergoes the maximum permanent deformation of 10.2 mm after the earthquake, creating new local tensile stress zones and plastic zones. In rare seismic conditions, the safety factor of the potential sliding mass on the slope is 1.80, and its potential failure mechanism is deformation failure with fault JF1 as the rear boundary surface and rock mass at the slope toe shear damaged. This study can provide reference for the dynamic response and stability analysis of complex high and steep rock slopes with favorable-dipping faults under seismic action.

In response to the current inability of the strong-motion observation network to provide seismic input records covering all areas of the epicenter vicinity, a technical framework for the rapid generation of kilometer-grid strong motion time histories has been established. Taking the M_S6.8 earthquake in Dingri, Xizang on January 7, 2025, as an example, the detailed processes of each technical procedure are described, and work on the inversion of the source rupture process, estimation of regional site conditions, and simulation of strong motion time histories has been carried out. The following results are obtained. The earthquake released a seismic moment of 4.7×10¹⁹ N•m, corresponding to a moment magnitude of 7.05. The fault slip is predominantly normal with a small amount of left-lateral strike-slip component, and the maximum slip displacement exceeded 3 meters. The rupture lasted for more than 20 seconds, mainly propagating in the northward direction, which may cause potential directivity effects. A V_S30 distribution map and engineering site classification map with a resolution of 30 arcseconds are provided, and the sites in the vicinity of epicenter area are mainly classified as ClassⅠand ClassⅡ, with V_S30 values ranging from 260 m/s to 510 m/s in the majority of the southeast area. Simulated three-component acceleration time histories for 14 996 virtual observation points in the near-field area (27°30′N~30°00′N、86°18′E~88°36′E) are provided, and the accuracy of the simulation results is verified by actual observation records. The maximum horizontal peak ground acceleration(PGA) can reach 1.0 g, and the 0.4 g and 0.2 g isolines approximately coincide with the IX and Ⅷ isoseismals, while the 0.10 g and 0.05 g isolines enclose areas slightly smaller than the Ⅶ and Ⅵ isoseismal zones. This research work and its results can provide reasonable seismic input for the damage identification, disaster evaluation, and resilience assessment of various disaster-bearing bodies in the epicentral area.

In order to predict the bearing capacity of steel plate-concrete reinforced composite (SPRC) coupling beams more conveniently. In this paper, it is of great significance to study the bearing capacity prediction model of SPRC coupling beams by machine learning (ML) method. Firstly, the SPRC coupling beam database is established by collecting the existing experimental data. On this basis, six ML algorithms, including extreme learning machine (ELM) algorithm, back propagation neural network (BPNN) algorithm, support vector machine (SVM) algorithm, K-nearest neighbor (KNN) algorithm, random forest (RF) algorithm and extreme gradient boosting (XGBoost) algorithm were used for data regression training. Through the comparative analysis of model performance indicators, it is found that the prediction model based on XGBoost algorithm has the best robustness and generalization ability. Compared with the softened strut-and-tie model (SSTM), it has higher calculation accuracy and stability. A high-precision SPRC coupling beam bearing capacity prediction model based on ML method is proposed. In addition, the sensitivity analysis of the parameters affecting the bearing capacity of SPRC coupling beams is also carried out. The results show that the influence degree of each characteristic parameter on the bearing capacity of SPRC coupling beams is in descending order as follows: steel plate ratio (ρ_p), coupling beam section height (h), coupling beam section width (b), span-depth ratio (l_n/h), stirrup yield strength (f_vy), longitudinal reinforcement ratio (ρ_s), longitudinal reinforcement yield strength (f_sy), stirrup ratio (ρ_t), steel plate yield strength (f_py), concrete compressive strength (f_cu).

To study the dynamic response characteristics of submarine sedimentary layer under seismic action, this paper establishes a single-layer unsaturated porous medium seabed model, presents its governing equations, boundary conditions and wave field expressions, and obtains the analytical solutions for the steady-state responses of unsaturated seabeds under different bottom permeability conditions. Through numerical examples, the influences of different bottom permeability conditions, saturation degrees, permeability coefficients, incident wave frequencies and depths on the solid surface displacement amplification factor and pore water pressure are analyzed, and the following main conclusions are drawn: under low-frequency conditions, the influence of the saturation degree of the sedimentary layer on the displacement amplification factor and pore water pressure is relatively weak. While in the case of increasing frequency, the influence of the saturation degree on the displacement amplification factor and pore water pressure is significantly enhanced. Under low-frequency conditions, for the sedimentary layer with a permeable bottom, the displacement amplification factor and pore water pressure are relatively large. While under high-frequency conditions, for the sedimentary layer with an impermeable bottom, the displacement amplification factor and pore water pressure are relatively large.

On January 7, 2025, an earthquake of magnitude M_S6.8 struck Dingri County, Xizang Autonomous Region. In this paper, the near-field seismic wave field and instrumental intensity field were simulated using the strong ground motion simulation and prediction cloud platform of the Institute of Engineering Mechanics, China Earthquake Administration (CEA), combined with the kinematic seismic source model, the regional public velocity model and the digital elevation model. The simulated and measured instrumental seismic intensities are comparable at the stations of the National Seismic Intensity Rapid Reporting and Early Warning Project. The simulated high intensity zones are mainly distributed around the place of the surface projection fault, and the simulated instrumental seismic intensity field is basically the same as the survey seismic intensity field. On the basis, the earthquake damage to typical buildings (mainly earth/stone and wood structures) and casualties was evaluated and the evaluation results were also comparable to the actual data.

In order to study the mechanical properties of ultra-high performance concrete (UHPC)-reinforced damaged specimens, a total of 10 UHPC-reinforced damaged reinforced concrete beams were designed. These beams were subjected to a four-point bending performance test to study the crack development, damage pattern, load carrying capacity, and displacement of UHPC-reinforced reinforced concrete beams under bending. The effects of different reinforcement thicknesses and different reinforcement methods on the bending performance of UHPC-reinforced damaged RC beams were analyzed. The experimental study shows that the load carrying capacity of UHPC-reinforced damaged RC beams is greatly improved, and the ultimate load is improved by up to 194%.The number of cracks that occur when damage occurs is more than that of the original beams, and the development is more complete; the ductility is greatly improved compared with the original beams, and the displacement ductility coefficients of the reinforced beams are considered to be increased by 49.77%~178.31% compared with that of the original beams. The calculation method and basic assumptions of the ultimate load of the UHPC-reinforced concrete beams are proposed, and the test parameters are substituted into the formula. The results are more consistent with the test values, indicating that the proposed formula can effectively predict the ultimate load of such reinforced beams.