Meng Zhang

Near-fault ground motions (NFGMs), characterized by forward-directivity velocity pulses, impose severe kinematic demands that challenge conventional structural systems. As modern civil engineering pivots toward rapid functional recovery, a critical paradigm shift is required: moving from component-centric kinematic vulnerability diagnostics to network-level systemic resilience optimization. This comprehensive review elucidates this transition, conceptualizing an integrated “3C Resilience Framework”—encompassing Coupled-multi-hazard, City-scale, and Carbon-friendly dimensions—as a strategic roadmap for next-generation seismic design. A pivotal focus is the physical evaluation of contemporary regulatory evolutions, specifically the multi-point spectral lower-bound constraints in American Society of Civil Engineers Standard 7-22 (ASCE 7-22) and the site-specific scaling factors in Eurocode 8. We demonstrate that these spectral floors are physically essential for flexible and isolated structures to constrain long-period kinetic energy, thereby mitigating the underestimation of residual drifts that fundamentally dictate repairability. Furthermore, this review explicitly aligns structural performance with the UN Sustainable Development Goals (SDG 9 & 11). By synthesizing advanced mitigation topologies with surrogate-assisted computational paradigms, this roadmap bridges the micro-to-macro scale gap between physical structural degradation and regional functional restoration, providing an actionable blueprint for sustainable urban networks.

Large steel frame support structures may encounter multiple-hazard coupling effects, such as earthquakes and wind loads, during their service period, and their combined damage effects are often significantly greater than those under single-hazard conditions. This study focuses on a single case example of large steel frame support structures, adopts a one-way CFD (Computational Fluid Dynamics)-to-structure loading analysis method to quantify the distribution of wind drag coefficients influenced under shielding effects, and reveals the response amplification and transition behavior under earthquake–wind load coupling effects through a systematic parametric analysis. The results demonstrate that within the simulated wind speed range (10–30 m/s), the drag coefficient of the structure is insensitive to the Reynolds number. The drag coefficient of the first row of members remains stable at approximately 1.25, whereas those of the second and subsequent rows are concentrated in the 0.6–0.8 range and decrease progressively along the wind direction. This pattern challenges the conventional design assumption of using a unified drag coefficient. Based on the analyzed cases, under earthquake–wind coupling effects, the structural amplitude amplification effect demonstrates significant load-dominant transition characteristics—when the earthquake acceleration is low (0.05 g), the wind load-induced amplitude amplification effect is pronounced, reaching 206.3%. As the earthquake intensity increases, the amplification effect stabilizes at approximately 9%. This study identifies structural drag coefficients for considering shielding effects, reveals the coupling mechanism between earthquakes and wind loads, and provides theoretical support for the multihazard performance-based design of temporary large-scale spatial structures. It should be noted that the findings and the proposed load-dominance transition characteristics are primarily applicable to temporary large-scale spatial frame structures operating within a service wind speed range of 10 to 30 m/s.

This research introduces a novel approach for seismic fragility assessment by employing a long short-term memory (LSTM) neural network to identify the most effective scalar and vector intensity measures (IMs). This approach enables the rapid and accurate plotting of vector fragility surfaces for shield tunnels embedded in layered soils and subjected to seismic actions. First, an extensive suite of two-dimensional, fully nonlinear soil–structure interaction analyses was executed to generate ground–motion–structure response pairs. These records were subsequently leveraged to train the LSTM network, which received free-field acceleration time histories and directly output critical engineering demand parameters along the tunnel lining. The developed framework significantly mitigates computational expenses while maintaining an acceptable level of fidelity relative to the reference finite element results. Consequently, it serves as an alternative to traditional time history evaluation techniques. Second, we conducted an IM screening process using the results of the LSTM predictions. On the basis of criteria such as relevance, efficiency, practicality, and professionalism, we benchmarked 17 scalar IM and 3 vector IM candidate schemes. The findings indicate that the peak ground velocity (PGV) serves as the most effective scalar IM, whereas the combination of peak ground acceleration (PGA) and PGV forms the optimal vector IM. Finally, probabilistic demand and capacity models are integrated within a fully analytical fragility formulation to derive both scalar and vector fragility estimates. Comparative evaluation reveals that vector IM based fragility surfaces markedly reduce epistemic uncertainty and furnish refined probabilistic descriptions of damage states (DSs) across the seismic demand space.

As the core component of electrified railway power supply systems, the fatigue performance and reliability of catenary support structures are directly related to the operational safety of high-speed railways. To address the problem of structural fatigue damage caused by increasing train speed and high-frequency operation, this study develops a refined finite element model including a support structure, suspension system and support column, and the dynamic response characteristics and fatigue life evolution law under train operation conditions are systematically analyzed. The results show that under the conditions of 250 km/h speed and 100 times daily traffic, the fatigue lives of the limit locator and positioning support are 43.56 years and 34.48 years, respectively, whereas the transverse cantilever connection and inclined cantilever have infinite life characteristics. When the train speed increases to 400 km/h, the annual fatigue damage of the positioning bearing increases from 0.029 to 0.065, and the service life is shortened by 55.7% to 15.27 years, which proves that high-speed working conditions significantly aggravate the deterioration of fatigue in the structure. The reliability analysis based on Monte Carlo simulation reveals that when the speed is 400 km/h and the daily traffic is 130 times, the structural reliability shows an exponential declining trend with increasing service life. If the daily traffic frequency exceeds 130, the 15-year reliability decreases to 92.5%, the 20-year reliability suddenly decreases to 82.4%, and there is a significant inflection point of failure in the 15–20 years of service. Considering the coupling effect of environmental factors (wind load, temperature and freezing), the actual failure risk may be higher than the theoretical value. On the basis of these findings, engineering suggestions are proposed: for high-speed lines with a daily traffic frequency of more than 130 times, shortening the overhaul cycle of the catenary support structure to 7–10 years and strengthening the periodic inspection and maintenance of positioning support and limit locators are recommended. The research results provide a theoretical basis for the safety assessment and maintenance decision making of high-speed railway catenary systems.

To study the aerodynamic and vibration characteristics of iced conductors under the influence of wind fluctuations, a harmonic superposition method is used to simulate nonuniform wind speeds. A user-defined function is written on the basis of the secondary development function of the Fluent 2021 R1 software to determine the displacement and velocity of the conductor at each time step, and a two-way fluid–structure interaction (FSI) numerical simulation of an iced conductor under a nonuniform wind field is performed via an overset mesh method. In the analysis, the aerodynamic coefficients and galloping characteristics of iced conductors under different degrees of freedom (DOFs) are investigated by considering different combinations of quasi-steady theory, unsteady theory, a uniform wind field, and a nonuniform wind field. The results show that in a nonuniform wind field, the mean, standard deviation (SD), and peak values of the drag and torsion coefficients of the conductors calculated via unsteady theory are significantly larger than those calculated via quasi-steady theory, indicating that the obtained aerodynamic coefficients of the latter (the mean values are typically used) conceal the characteristics of the iced conductors in an actual wind environment and ignore the adverse effects of the variability.

Taking an actual 3MW steel–concrete composite wind turbine tower as an example, a finite element model of the tower structure was established, and static bearing capacity and dynamic time history response analyses were performed to identify the locations where the structure is prone to failure. On this basis, the fatigue lives of the turbine tower at the most unfavorable locations were predicted using linear cumulative damage theory, and the fatigue reliability at the corresponding locations of the structure was calculated using the kriging–subset simulation method. The most dangerous locations of the tower that are most prone to failure are as follows: the bottom of the leeward side of the upper steel tube, the flange of the steel tube, the bolt-hole imprinting surface of the flange, the leeward side of the transition tube, and the top of the leeward side of the concrete tube. The failure risk of the flange and bolt-hole imprinting surface of the upper steel tube is relatively high, followed by that of the transition tube. This indicates that special attention should be given to the design and daily maintenance of this part. The fatigue resistance of the tower can be enhanced by improving the strength of the flange plate or increasing the number of bolts and strengthening the transition tube.

Based on the WindPACT-3MW wind turbine tower commonly used in wind power engineering, a finite element model (FEM) of a hybrid wind turbine tower combining an upper steel tube with a lower steel truss is designed and established. On this basis, a static optimization analysis, wind-induced vibration analysis, and fatigue life analysis of the hybrid tower structure are performed. The results show that under the same design parameters, the overall stiffness and static bearing capacity of the tower structure can be significantly improved by using subdivided truss webs, increasing the truss height as much as possible and increasing the width of the truss base appropriately. Under normal operation conditions, the response of the tower structure in the along-wind direction is significantly greater than the response in the crosswind direction, indicating that the aerodynamic thrust generated by the rotation of the blades is the main factor causing the wind-induced vibration of the tower structure. For the tower structure analyzed in this study, when considering the entire range of wind speeds from the cut-in wind speed to the cut-out wind speed, the fatigue life of the structure is 38.5 years.

Sealing net structures are frequently used as protective devices for newly constructed transmission lines that intersect existing lines. They aim to ensure safety during the construction and operation of the intersecting lines. To explore the wind deflection response characteristics of sealing net structures under wind loads, a model of the sealing net structure was created using ANSYS/APDL software for finite element analysis. This model represents an overhead sealing net structure spanning an existing line. The results obtained from finite element simulations aligned well with the theoretical calculations, indicating the validity of the established finite element model for accurately analyzing the wind-induced response of the sealing net structure. Expanding on this foundation, the study analyzed the impact of various factors on the wind deflection of the sealing net. These factors encompass the span, wind speed, pretension of the catenary cable, wind direction angle, arrangement angle, and method of additional stay cables. The research investigated the influence of these factors on the wind deflection of the sealing net structure. Additionally, a proposal was presented for arranging the closure structure to mitigate wind deflection. This proposal provides valuable guidance for the design and safety considerations of transmission lines and sealing net structures.