Peng Chen

Seismic pounding against moat walls (MWs) may occur in seismically base‐isolated buildings equipped with insufficient isolation clearances, especially during strong pulse‐like earthquakes. Serious MW pounding significantly amplifies the story drifts and floor accelerations of the superstructure, impairing structural isolation effectiveness. Hence, various passive gap dampers (GDs) have been developed in isolation systems to provide adaptive deformation mitigation, accommodating multiple earthquake intensities. This study comprehensively investigates the seismic performance of adaptive base‐isolated systems incorporating various GDs during strong earthquakes. Three typical types of passive GDs, that is, steel, shape memory alloy (SMA), and viscous GDs, were considered. An analytical model was developed for the inelastic two‐degree‐of‐freedom system incorporating GDs. Parametric response analyses were numerically conducted by varying the types and design parameters of GDs and the pulse period ratios of ground motions. The results demonstrate that adaptive systems with GDs exhibit superior deformation mitigation in the isolation layer during pulse‐like earthquakes, compared with conventional systems without GDs. The comparisons of various GDs indicate that steel GDs characterized by full energy dissipation are effective in decreasing the maximum force in the isolation layer and maximum deformation of the superstructure, while the insufficient self‐centering capability may increase the deformation responses and the risk of MW pounding in the isolation layer, during pulse‐like earthquakes. In contrast, SMA GDs with superelastic effect and medium energy dissipation achieve better mitigation in the maximum and residual deformations of the isolation layer, decreasing the risk of MW pounding. On average, steel and SMA GDs exhibit comparable maximum deformation and acceleration of the superstructure. Viscous GDs exhibit significantly higher maximum shear force and energy dissipation during pulse‐like ground motions. Therefore, compared with hysteretic GDs, viscous GDs may achieve superior deformation mitigation in the isolation layer, while increasing the maximum deformation and acceleration of the superstructure, during pulse‐like ground motions. Design recommendations are proposed for adaptive isolation systems incorporating various passive GDs, advancing the seismic design for mitigating MW pounding and enhancing seismic resilience.

Shape memory alloys (SMAs) have attracted increasing attention in recent years for their application in self‐centering (SC) seismic structures. To take full advantage of their recovery capability and energy dissipation (ED) potential, SMAs are typically incorporated into plastic hinge regions of reinforced concrete components as longitudinal reinforcement or utilized in high‐performance seismic protection devices. However, for widely used nickel–titanium SMAs, their smooth surface and poor machinability present significant challenges for the design of reliable mechanical connections with conventional steel reinforcement. To address this issue, this study proposes an efficient SMA–steel bar connection strategy that integrates swaged sleeves on SMA bars with straight‐threaded couplers, enabling reliable force transfer and rapid specimen assembly. The structural configuration and key design considerations of the proposed connection system were first presented. Experimental investigations were then conducted to evaluate its mechanical performance, with particular emphasis on the effects of sleeve length and bar diameter. Test results demonstrate that the proposed connection system provides a stable mechanical splice and reliable load transfer under various loading conditions, while maintaining the characteristic flag‐shaped hysteretic response of SMAs. Although the ED capacity of SMAs is lower than that of conventional hysteretic dampers, their primary function is to provide substantial SC capability to structural systems, which makes them highly attractive for seismic design. This study provides an efficient and reliable connection solution for SMA bars, supporting their wide application in seismic‐resilient structural systems.

Heliostats constitute essential elements within concentrating solar power (CSP), where their structure, load profiles, and operational environment render wind loads a critical factor in their design considerations, as these loads directly impact the cost of energy generation. The aerodynamics significantly influence wind-induced effects, resulting in considerable variability in wind loads among different heliostat geometries. This study utilizes the Computational Fluid Dynamics (CFD) methodology to systematically examine the aerodynamic behavior of an isolated pentagonal heliostat. Employing the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with an atmospheric boundary layer inlet condition, the investigation focuses on the flow field and wind load characteristics at four representative pitch angles: 0° (stow position), 30°, 60°, and 90°. Findings indicate that the pitch angle exerts a decisive impact on flow separation patterns. Specifically, as the elevation angle decreases, the flow regime shifts from being predominantly influenced by the mirror surface to being governed by the support structure, mediated through an interactive coupling between these components. At the 60° operational pitch angle, the pentagonal heliostat’s distinctive corner geometry induces an asymmetric vortex configuration—characterized by a smaller vortex at the top and a larger one at the bottom—thereby disrupting the conventional vortex distribution observed in symmetric heliostat designs. A further analysis of wind load characteristics indicates that, compared to a quadrilateral heliostat, the pentagonal mirror exhibits a significantly lower Elevation Moment Coefficient, despite a slight increase in the normal force coefficient. This reduction is attributed to a balancing mechanism: the “vortex structure asymmetry” creates an upper-large–lower-small distribution of absolute negative pressure on the support surface, while the “stagnation point position” shift with elevation angle produces an upper-small–lower-large distribution of absolute positive pressure on the reflector. The interaction between these opposing trends minimizes the net pressure differential across the mirror height, thereby contributing to superior overall aerodynamic performance. The reduction in the elevation moment coefficient contributes to enhanced structural wind resistance, thereby improving the overall energy efficiency and economic viability of concentrating solar power.

Lead Rubber Bearings (LRBs) are widely used in seismic isolation systems due to their excellent energy dissipation and stability under dynamic loading. However, under extreme conditions, LRBs undergo large strain stiffening, degradation, and strength reduction due to lead core heating. These factors pose challenges for accurately modeling their nonlinear behavior. The commonly used Bouc–Wen model in engineering struggles to capture the complex hysteretic characteristics of LRBs. This study develops an improved Bouc–Wen model that effectively captures large strain nonlinearities. In addition, the model incorporates a strength reduction factor to account for lead core heating and an adjustment coefficient to characterize initial hardening. A data‐driven approach is further introduced to intelligently predict shape parameters, improving computational efficiency and practical applicability. The proposed model is validated through dynamic compression‐shear tests under various loading protocols, particularly those involving large deformation and long‐duration loading. Comparisons based on hysteresis curves, equivalent stiffness, and equivalent damping ratio demonstrate that the proposed model more accurately reproduces LRB behavior. It effectively captures key nonlinear effects, leading to improved accuracy in seismic isolation analysis and design.

Reinforced concrete (RC) structural walls are commonly used as lateral-load resisting systems for mid- and high-rise buildings. Due to their relatively large stiffness and high strength, there is a consensus in the earthquake engineering community that well-designed RC walls exhibit superior performance under strong earthquakes. The expected energy dissipation mechanism of cantilever walls is flexural yielding concentrated at the bottom of the wall (i.e., the plastic hinge region). However, the bottom walls of high-rise buildings usually experience complex force and moment combinations, making them prone to considerable damage under extreme conditions, which can cause irreparable failure and interruption of functionality. Therefore, improving the seismic performance of bottom RC walls is one of the critical issues for high-rise buildings in earthquake-prone regions. First, the current design practices of axial compressive behavior, global instability, and minimum reinforcement ratio for RC walls were summarized. Design considerations for improving the seismic performance of RC walls under extreme conditions were discussed. Subsequently, three typical failure modes (axial compressive failure, global instability, and shear failure) of the RC wall and the improvement measures were validated through finite element analyses. Numerical results demonstrate that the embedded steel plate can efficiently improve the performance of walls under high axial compressive force and large shear force conditions, providing one of the successful solutions for improving seismic resilience of RC walls.

High‐damping rubber bearings (HDRBs) are among the most widely used seismic isolators in bridge and building engineering. However, they exhibit significant nonlinear behavior, particularly under large‐strain deformation. Key nonlinearities include large‐strain hardening, degradation, temporary hardening, and initial hardening. Incorporating all these characteristics into a single macroscopic model is challenging. This study reviews the most relevant and accurate models for HDRBs and highlights their significant features. To address the limitations in existing models, an improved Bouc–Wen (IBW) model is proposed and implemented in OpenSees. Reversed loading cycles were conducted on HDRB specimens, and the widely adopted deformation history integral (DHI) model is also introduced for comparative analysis. The IBW model is validated by comparing it with DHI model and experimental results, with comparisons focused on the shape of hysteretic loops, equivalent stiffness, and damping ratios. Results demonstrate the applicability and accuracy of the proposed numerical element in modeling HDRBs under displacement‐controlled reversed loading. The IBW model proves more concise and effectively represents the primary nonlinearities of HDRBs. Overall, it outperforms the DHI model in scenarios involving large strains and initial loading cycles, while the DHI model shows slightly higher accuracy in low‐to‐moderate strain cycles. Future research should investigate strength degradation under prolonged loading and the dynamic response of both bearings and isolated superstructures under seismic loading.