The application of prefabricated assembly technology in underground structures has increasingly garnered attention due to its potential for urban low-carbon development. However, given the vulnerability of such structures subjected to unexpected seismic events, a resilient prefabricated underground structure is deemed preferable for mitigating seismic responses and facilitating rapid recovery. This study proposes a resilient slip-friction connection-enhanced self-centering column (RSFC-SCC) for prefabricated underground structures to promote the multi-level self-centering benefits against multi-intensity earthquakes. The RSFC-SCC is composed of an SCC with two sub-columns and a series of multi-arranged replaceable RSFCs, intended to substitute the fragile central column. The mechanical model and practical manufacturing approach are elucidated, emphasizing its potential multi-level self-centering benefits and working mechanism. Given the established simulation model of RSFC-SCC-equipped prefabricated underground structures, the seismic response characteristics and mitigation capacity are investigated for a typical underground structure, involving robustness against various earthquakes. A multi-level self-centering capacity-oriented design with suggested parameter selection criteria is proposed for the RSFC-SCC to ensure that prefabricated underground structures achieve the desired vibration mitigation performance. The results show that the SCC with multi-arranged replaceable RSFCs exhibits a significant vibration isolating effect and enhanced self-centering capacity for the entire prefabricated underground structure. Benefiting from the multi-level self-centering process, the RSFC-SCC illustrates a robust capacity that adapts to varying intensities of earthquakes. The multi-level self-centering capacity-oriented design effectively facilitates the target seismic response control for the prefabricated underground structures. The energy dissipation burden and residual deformation of primary structures are mitigated within the target performance framework. Given the replacement ease of RSFCs and SCC, a rapid recovery of the prefabricated underground structure after an earthquake is ensured.

This study presents a novel seismic control system, the Mega-Sub Controlled Structure System (MSCSS), to address vibration control challenges in tall and super-tall buildings under intense seismic excitations. The proposed hybrid VD-TFPB-controlled MSCSS integrates Triple Friction Pendulum Bearings (TFPBs) as base isolators with Viscous Dampers (VDs) between the mega frame and the vibration control substructure, enhancing damping and seismic performance. MSCSS without VD and MSCSS with VD models are established and verified using an existing benchmark. The hybrid VD-TFPB-controlled MSCSS is then developed to evaluate its vibration control response while considering soil-structure interaction (SSI). Numerical analyses with earthquake records demonstrate its superior performance compared to MSCSS without and with VD systems. Nonlinear dynamic analyses reveal that the hybrid system significantly improves vibration control. However, under SSI, increased structural flexibility leads to higher frame stress and more plastic hinges, particularly on soft soil, which amplifies vibrations. Despite these challenges, the hybrid VD-TFPB-controlled MSCSS effectively enhances seismic resilience, offering a robust solution for tall buildings.

Designers often assume a rigid foundation for buildings in seismic zones, believing it ensures safety during earthquakes. However, this assumption may neglect important factors, such as soil-structure interaction (SSI) and the potential for collisions between adjacent buildings. This study investigates the effect of dynamic SSI on the seismic pounding response of adjacent buildings. A nonlinear finite-element analysis was performed on three cases: bare buildings, buildings with linear fluid viscous dampers (LFVDs), and buildings with nonlinear fluid viscous dampers (NFVDs). The dynamic contact technique, in which contact surfaces with both the contactor and target, was employed to mimic the mutual pounding. Key seismic response parameters, including acceleration, displacement, inter-story drift, and pounding forces, were analyzed. The results showed that dynamic SSI significantly affects the seismic performance of adjacent buildings, altering the number, timing, and intensity of collisions. In some cases, SSI increased inter-story drifts beyond code-permissible limits, indicating that relying on a rigid foundation assumption could lead to unsafe structural designs. Additionally, SSI had a notable impact on the forces in NFVDs, highlighting the need for careful design considerations when using these devices. The study further investigates the effect of soil flexibility on the performance of nearby structures under different seismic excitations, focusing on the NFVDs case with a 10 % damping ratio. Incremental Dynamic Analysis (IDA) and fragility analysis were conducted to assess performance under seismic excitations, focusing on three performance levels: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). While SSI had minimal impact on the more flexible buildings, it significantly affected the more rigid building, particularly at LS and CP levels, making it more vulnerable to damage compared to buildings on rigid foundations. These findings underscore the importance of incorporating SSI in seismic design to ensure structural safety.

The objective of this study is to develop and evaluate a new type of energy dissipation box damper, designed for use in seismic-resistant structures. This damper utilizes natural granular materials, primarily sand, as the key damping mechanism. The research was conducted through a series of experiments to investigate the mechanical properties of the damper under different operational conditions. The study focused on the effectiveness of sand as a damping agent, the examination of various damper configurations including both single and dual silhouette models, and the assessment of damper performance under variable testing rates. It was found that sand, with its fine and smooth particles, offers excellent damping properties. The single silhouette model, in particular, demonstrated improvements in stability, load distribution, and energy dissipation efficiency when used with sand. The damper showed robust hysteresis behavior, proving its reliability under high-load scenarios. Additionally, the influence of testing rates on the damping behavior was significant, with higher rates improving the damping ratio in sand-based systems. The LuGre model was applied to provide a mathematical representation of the experimental findings; however, some discrepancies were noted, attributed to the model's limitations and the experimental uncertainties. The results highlight the damper's potential as an economical alternative for seismic resistance, leveraging the low cost and simplicity of natural materials. The design of the damper focuses on simplicity and ease of maintenance, making a significant contribution to the progress in earthquake mitigation technologies.

The study of vibration isolation devices has become an emerging area of research in view of the extensive damage to buildings caused by earthquakes. The ability to effectively isolate seismic vibrations and maintain the stability of a building is thus addressed in this paper, which evaluates the effect of horizontal ground excitation on the response of a structure isolated by a coupled isolation system consisting of a non-linear damper (QZS) and a friction pendulum system (FPS). A single-degree-of-freedom system was used to model structures whose bases are subjected to seismic excitation in order to assess the effectiveness of the QZS-FPS coupling in reducing the structural response. The results obtained revealed significant improvements in structural performance when the QZS-FPS system uses a damper of optimum stiffness. A 30% reduction in displacement was recorded compared with QZS alone for two signals, one harmonic and the other stochastic. The response of the QZS-FPS system with soft stiffness to a harmonic pulse reveals amplitudes reaching around eight times those of the pulse at low frequencies and approaching zero at high frequencies. In comparison, the rigid QZS-FPS coupling has amplitudes 0.9 and 3.5 times higher than those of the harmonic signal. Thus, the resonance amplitudes observed for the QZS-FPS system are lower than those reported in other studies. This analysis highlights the performance differences between the two types of stiffness in the face of harmonic pulses, underlining the importance of the choice of stiffness in vibration management applications. The stochastic results show that on both hard and soft soils, the new QZS-FPS system causes structures to vibrate horizontally with maximum amplitudes of the order of 0.003 m and 0.007 m respectively. So, QZS-FPS coupling can be more effective than all other isolators for horizontal ground excitation. In addition, the study demonstrated that the QZS-FPS combination can offer better control of building vibration in terms of horizontal displacements.

To mitigate the metro-induced vertical vibration of the indoor substation structure, this study proposes a gas-spring quasi-zero stiffness air damping isolator (AD-QZSI) with excellent low dynamic stiffness and high-static stiffness characteristics. The working principle and mechanical properties of the AD-QZSI are introduced and studied through theoretical and numerical methods. A model for substation considering soil-structure-equipment interaction is established using the software ABAQUS, its accuracy is validated based on a series of measured data from actual projects, and the AD-QZSI's simulation method and parameter design method are described in detail. The air damper's stiffness ka is integrated into the isolator's mechanical model, theoretically and numerically achieving an accurate simulation of AD-QZSI's nonlinear mechanical properties. The numerical results have an error of less than 5% with the measured data, indicating that the model is able to better capture the actual structure's dynamic characteristics and is reasonable to be employed for subsequent analysis. Numerical results show that AD-QZSI can significantly reduce the structural vertical vibration, and its control effect is better in the whole frequency band, in particular, the effect is also visible in the low-frequency band, indicating that its vibration isolation frequency band is wider than that of traditional QZS isolator. With the vibration source distance increasing, the control effect of AD-QZSI presents a tendency to decrease and then level off, and its vibration isolation gain is weakened by the continuous increase of the damping ratio greater than 0.01. Moreover, the equipment's dynamic amplification factor of the isolated structure decreases significantly. Finally, the proposed AD-QZSI can obtain ideal quasi-zero stiffness characteristics by adjusting the air pressure, and the adopted air damper belongs to the green low-carbon components, featuring great practical value and application prospects.

Active tuned mass damper (ATMD) is widely adopted as a reliable active device to protect tall buildings subjected to earthquake excitations from severe seismic damages. Soil-structure interaction (SSI) phenomena effects on the free vibration characteristics and the seismic responses of tall structures. This study presents the design of an adaptive sliding sector controller (ASSC) for the active control of tall buildings equipped with an ATMD system considering the SSI effects. The ASSC technique is designed based on the hyper-surface of the sliding mode which is surrounded by a sector and can consider the uncertainty of system parameters. To validate the efficiency of the ASSC technique, its design is first implemented for a 40-story building equipped with an ATMD system under an artificial earthquake excitation for different soil types. Then, the performance of the designed ASSC technique is evaluated in mitigating the seismic responses of the structure subjected to five real earthquake excitations considering the SSI effects. In addition, the efficiency of the designed ASSC strategy is compared against that of the two controller techniques including proportional-integral-derivative (PID) and linear-quadratic regulator (LQR). Comparative results demonstrate the efficiency of the ASSC strategy for the reduction of the structural responses under real earthquake excitations.

The seismic performance of a long-span triple-tower suspension bridge is a critical consideration in engineering communities. To promote a better seismic design, this paper presents a parametric study on the structural seismic control using hysteretic steel dampers. The finite element model is firstly established, and an introduction to the mechanical properties of the E-shaped hysteretic steel damper is made. Then, a seismic analysis is conducted under uniform earthquake excitations. Considering the effect of wave passage, the performance of hysteretic steel dampers in seismic control is further analyzed. The results indicate that the travelling wave effect greatly affects seismic responses. Increasing the damper elastic stiffness can effectively reduce the relative displacement between the main girder and either the left or the central tower. This treatment is effective for the right tower only when the wave velocity is among 400-1600 m/s, while it makes little contribution in other ranges. At an arbitrary wave velocity, increasing the damper elastic stiffness would cause minor changes to the shear forces of side towers, while its influence on the central tower is significant. A reasonable damper design for the long-span triple-tower suspension bridge depends on an essential prior evaluation of the wave velocity based on soil conditions.

A tuned liquid damper (TLD) is one of the most economically passive vibration control strategies for controlling the wind-induced vibrations of structures such as wind turbines (WT). The literature on fluid-structure interaction limits the scope of analysis to either the influence of wind on tower, or liquid on tank. Meanwhile, it does not consider the applicability of damper installation inside the tower or even inside the nacelle. This study adopts an integrated experimental and numerical approach to find an applicable TLD configuration to mitigate vibrations of a 5-MW wind turbine considering the mutual effects between wind, tower, and liquid damper. It uses the Ansys Fluent module in the tower's TLD and wind-induced vibrations. It starts with wind load simulation, including the vortex shedding effect. Then, it presents the sloshing water behavior and validates it with an experimental model. Parametric study has been conducted to consider the effect of different mass ratios, frequency ratios, and the influence of soil stiffness on the response on the WT tower. The experimental analysis demonstrates TLD's feasibility in mitigating vibration sufficiently with a 40% displacement reduction. A single TLD with a 4% mass ratio can reduce the lateral deformations by 7.32 and 12.5% of WT with fixed and partially fixed end conditions, respectively. While using a configuration of 3 TLDs with a 12% mass ratio extends the fatigue life by 38% and offers a gain in lateral deformations reduction that reached 48.73 and 71.45% for both fixed and partially fixed end conditions.

This paper presents an experimental and analytical study on a steel slit damper designed as an energy dissipative device for earthquake protection of structures considering soil-structure interaction. The steel slit damper is made of a steel plate with a number of slits cut out of it. The slit damper has an advantage as a seismic energy dissipation device in that the stiffness and the yield force of the damper can be easily controlled by changing the number and size of the vertical strips. Cyclic loading tests of the slit damper are carried out to verify its energy dissipation capability, and an analytical model is developed validated based on the test results. The seismic performance of a case study building is then assessed using nonlinear dynamic analysis with and without soil-structure interaction. The soil-structure system turns out to show larger seismic responses and thus seismic retrofit is required to satisfy a predefined performance limit state. The developed slit dampers are employed as a seismic energy dissipation device for retrofitting the case study structure taking into account the soil-structure interaction. The seismic performance evaluation of the model structure shows that the device works stably and dissipates significant amount of seismic energy during earthquake excitations, and is effective in lowering the seismic response of structures standing on soft soil.