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.

Shallow foundations supporting high-rise structures are often subjected to extreme lateral loading from wind and seismic activities. Nonlinear soil-foundation system behaviors, such as foundation uplift or bearing capacity mobilization (i.e., rocking behavior), can act as energy dissipation mechanisms, potentially reducing structural demands. However, such merits may be achieved at the expense of large residual deformations and settlements, which are influenced by various factors. One key factor which is highly influential on soil deformation mechanisms during rocking is the foundation embedment depth. This aspect of rocking foundations is investigated in this study under varying subgrade densities and initial vertical factors of safety (FSv), using the PIV technique and appropriate instrumentation. A series of reduced-scale slow cyclic tests were performed using a single-degree-of-freedom (SDOF) structure model. This study first examines the deformation mechanisms of strip foundations with depth-to-width (D/B) ratios of 0, 0.25, and 1, and then explores the effects of embedment depth on the performance of square foundations, evaluating moment capacity, settlement, recentering capability, rotational stiffness, and damping characteristics. The results demonstrate that the predominant deformation mechanism of the soil mass transitions from a wedge mechanism in surface foundations to a scoop mechanism in embedded foundations. Increasing the embedment depth enhances recentering capabilities, reduces damping, decreases settlement, increases rotational stiffness, and improves the moment capacity of the foundations. This comprehensive exploration of foundation performance and soil deformation mechanisms, considering varying embedment depths, FSv values, and soil relative densities, offers insights for optimizing the performance of rocking foundations under lateral loading conditions.

Sources such as wind or severe seismic activity often exert extreme lateral loading onto the shallow foundations supporting high-rise structures such as bridge piers, buildings, shear walls, and wind turbine towers. Such loading conditions may cause the foundation to exhibit nonlinear responses such as uplift and bearing capacity mobilization of the supporting soil (i.e., rocking behavior). Previous numerical and experimental studies suggest that while such inelastic behaviors may engender residual deformations in the soil-foundation system, they offer potential benefits to the overall integrity of structures through dissipating energy and reducing inertia forces transmitted to the superstructure, thereby limiting seismic demand on structural elements. This study investigates the effect of footing shape on the rocking performance of shallow foundations in different subgrade densities and initial vertical factor of safety (FSv). To this end, a series of reduced-scale slow cyclic tests under 1 g condition were conducted using a single degree of freedom (SDOF) structure model. The performance of different footing shapes was studied in terms of moment capacity, recentering ratio, rocking stiffness, damping ratio, and settlement. For three foundations with different length-to-width ratios, the results indicate that increasing the safety factor and length-to-width ratio leads to thinner, S-shaped moment-rotation curves, mainly owing to the enhanced recentering capability and the P-delta effect. Moreover, across all foundation types, the repetition of a limited loading cycles with consistent rotation amplitude does not cause stiffness degradation or moment capacity reduction.