Earth fissures pose a significant risk to the seismic safety of underground structures at earth fissure sites (USEFs), particularly for large-scale underground frame structures such as subway stations. To date, the failure mechanism of USEFs has only been analyzed qualitatively and requires further comprehensive investigation. Moreover, the existing failure prediction methods for USEFs are complicated, challenging to execute, time-consuming, and incur significant financial costs, necessitating the establishment of a simple and efficient failure prediction method. This study conducted a shaking table test on a USEF to investigate the dynamic response of earth fissure sites and the seismic damage characteristics of a USEF. Based on the experimental results, a tailored pushover analysis method was developed to predict the seismic failure of the USEF and was applied to reveal its underlying seismic failure mechanisms. It was found that low-frequency ground motions are significantly amplified at the earth fissure site and that the acceleration amplitudes at the hanging wall and footwall are nonuniform. This nonuniform acceleration leads to significant extrusion and separation between the hanging wall and footwall. The extrusion causes the soil to rise, exerting additional axial pressure and bending moments on the lateral resistance members. These additional forces lead to uneven internal force distributions within the USEF, highlighting that structurally weak members are prone to failure and accelerating structural damage. The bottom column at the hanging wall is the critical seismic member of the USEF, which requires focused reinforcement and monitoring to increase resilience. The tailored pushover analysis method accurately represents the deformation characteristics at earth fissure sites. The method captures distinct structural destruction patterns, enhancing its utility in seismic failure prediction for USEFs.

This study investigates the seismic response of a rocking wall frame structure considering dynamic soil-structure interaction (DSSI) through shaking table tests. A comparison with conventional frame structures and structures with fixed-base foundations is made to examine the influence of DSSI effects on various aspects including structural damage distribution, dynamic characteristics, and floor responses. Test results indicate that the presence of a rocking wall reduces structural responses across different site conditions, although the reduction is less significant under soft soil conditions compared to fixed-base foundation conditions. Overall, DSSI diminishes the mitigating effect of the rocking wall on the maximum structural response. Furthermore, a three-dimensional finite element model of the shaking table test is established. The numerical model employs the equivalent linear method to simulate the soil's nonlinear behavior and incorporates the concept of the rocking wall. Comparative analysis between experimental and simulated results demonstrates that the model effectively predicts the dynamic response of the rocking wall frame structure in DSSI systems.

Earthquake-induced liquefaction is a geological disaster that caused extensive damage to buildings, railways, dams. Due to the construction techniques and economic conditions, the subsurface layers of some buildings must be reinforced to resist seismic loads. Microbial-induced desaturation is a development technique which can be used for existing buildings to mitigate liquefaction. Shaking table tests were conducted to survey the effect of microbial induced desaturation on liquefaction-prone foundations beneath buildings. The test results showed that, lower saturation degree delays the generation of excess pore pressure and reduces its magnitude. It appears that the resistance to excess pressure increases as saturation degree is reduced from 100% to 93.4% or 85.6%. Desaturation prevents the decay of the amplitude of acceleration oscillations, but increases the accelerations of the structure. The settlement of the sandy soil decreases as the saturation degree decreases. Resistance to liquefaction increased by more than twice than that in the saturated sample after induced desaturation to 93.4%. The weight of the building structure contributes to the anti-liquefaction capacity.

With the development of the Chinese economy and society, the height and density of urban buildings are increasing, and large underground transportation hubs have been constructed in many places to alleviate the pressure of transportation. Commercial buildings are usually developed above the large underground transportation hubs, so the underground structures may have very shallow depths or no soil cover. The seismic response and damage mechanisms of such underground structures still need to be studied. In this paper, an example of a project in China is taken as an object to analyze the seismic response and damage mechanism of the structure after simplification. The spatial distribution of deformations and internal forces of such structures and the location of the maximum internal forces are obtained, and the effect of the frequency of seismic motions on the structural response is obtained. Finally, an elastoplastic analysis of such structures is carried out to assess the damage location and the damage evolution process.

Multiple research studies and seismic data analyses have shown that multi-directional long-period ground motion affects crucial and intricate large-scale structures like oil storage containers, long-span bridges, and high-rise buildings. Seismic damage data show a 3-55% chance of long-period ground motion. To clarify, the chance of occurrence is 3% in hard soil and 83% in soft soil. Due of the above characteristics, the aseismic engineering field requires a realistic stochastic model that accounts for long-period multi-directional ground motion. A weighted average seismic amplification coefficient selected NGA database multi-directional long-period ground motion recordings for this study. Due to the significant low-frequency component in the long-period ground motion, this research uses empirical mode decomposition (EMD) to efficiently decompose it into a composite structure with high- and low-frequency components. Given the above, further investigation is needed on the evolutionary power spectrum density (EPSD) functions of high- and low-frequency components. Analyzing the recorded data will reveal these functions and their corresponding parameters. Proper orthogonal decomposition (POD) is needed to simulate samples of high- and low-frequency components in different directions. These samples can be combined to illustrate multi-directional long-period ground motion. Representative samples exhibit the seismic characteristics of long-period multi-directional ground motion, as shown by numerical examples. This proves the method's engineering accuracy and usefulness. Moreover, this study used incremental dynamic analysis (IDA) to apply seismic vulnerability theory. This study investigated whether long-period ground motions in both x and multi-directional directions could enhance the seismic response of a high-rise frame structure. By using this method, a comprehensive seismic economic loss rate curve was created, making economic loss assessment clearer. This study shows that multi-directional impacts should be included when studying seismic events and calculating structure economic damages.

This paper employs a three-dimensional nonlinear finite element method to analyze settlement and deformation during construction. By considering the interaction between the superstructure, foundation, and subgrade, the method reveals both the magnitude of settlement and the distribution of uneven settlement across the structure. This information is used to adjust the foundation design or implement structural measures to ensure uniform settlement, thereby preventing damage caused by differential settlement. In terms of absolute settlement values, the Mohr-Coulomb model predicts the largest settlement, with a maximum value of approximately 11.7 cm. The linear elastic model calculates the smallest settlement, with a maximum value of around 4.5 cm. The Duncan-Chang model offers an intermediate prediction, with a maximum settlement value of about 8.9 cm. Utilizing the ABAQUS finite element software, a 3D model of a natural foundation strip for a three-story masonry structure was developed. The Duncan-Chang nonlinear elasticity model, which effectively describes the behavior of hardening soil, was applied within the software platform to conduct a detailed numerical simulation. At the same time, the paper assumes that the foundation soil is considered the linear elastic model and the Moore-Coulomb ideal elastic-plastic model is compared with the internal force of the superstructure under different foundation models obtained. According to the maximum principal stress analysis, the areas where the wall may be damaged are received, and the measures to reduce the uneven settlement are proposed.