A utility tunnel is an infrastructure that consolidates multiple municipal pipeline systems into a shared underground passage. As long linear structures inevitably cross different soils, this paper aims to accurately assess the seismic damage to a shallow-buried utility tunnel in a non-homogeneous zone by employing a viscous-spring artificial boundary and deriving the corresponding nodal force equations. The three-dimensional model of the utility tunnel-soil system is established using finite element software, and a plug-in is developed to simulate the three-dimensional oblique incidence of SV waves with a horizontal non-homogeneous field. In this study, the maximum interstory displacement angle of the utility tunnel is used as the damage indicator. Analysis of structural vulnerability based on IDA method using PGA as an indicator of seismic wave intensity, which considers the angle of oblique incidence of SV waves, the type of seismic waves, and the influence of the nonhomogeneous field on the seismic performance of the utility tunnel. The results indicate that the failure probability of the utility tunnel in different soil types increases with the incident angle and PGA. Additionally, the failure probability under the pulse wave is higher than that under the non-pulse wave; Particular attention is given to the states of severe damage (LS) and collapse (CP), particularly when the angle of incidence is 30 degrees and the PGA exceeds 0.6g, conditions under which the probability of failure is higher. Additionally, the failure probability of the non-homogeneous zone is greater than that of sand and clay; the maximum interlayer displacement angle increases with the incident angle, accompanied by greater PGA dispersion, indicating the seismic wave intensity. The maximum inter-layer displacement angle increases with the incident angle, and the dispersion of the seismic wave intensity indicator (PGA) becomes greater. This paper proposes vulnerability curves for different working conditions, which can serve as a reference for the seismic design of underground structures.

With the rapid development of infrastructure in western China, numerous arch bridges have been constructed as vital transportation hubs spanning river canyons. Understanding the impact of canyon topography on the seismic response of long-span half-through arch bridges crossing canyons is essential. This study first establishes a seismic input method for oblique P-wave and SV-wave incidence, based on the viscous-spring artificial boundary theory, which transforms ground motions into equivalent nodal loads on artificial boundaries. The feasibility of this proposed method is systematically validated. Subsequently, parametric investigations are carried out to explore the effects of seismic wave incidence angle, canyon depth-to-breadth ratio and soil elastic modulus on the ground motion amplification characteristics in V-shaped canyons under oblique P-wave and SV-wave excitations. Finally, dynamic response patterns of the arch ribs and the stress-strain relationships at critical structural components are thoroughly analyzed. Key findings reveal that SV-waves induce significantly different ground motion amplification effects compared to P-waves, with the wave incidence angle and canyon width-to-depth ratio being crucial influencing factors. The connection between the arch footings and the concrete cross braces constitutes the most vulnerable region, frequently exhibiting maximum stresses that exceed the yield strength of C40 concrete under multiple scenarios. Notably, when the depth-to-breadth ratio (D/B) is 0.75, the peak stress at the arch footings reaches 5.18 x 10(7)kPa, surpassing the yield stress threshold of C40 concrete. These findings highlight the need for special seismic fortification measures at these critical connections during bridge design. This research offers valuable insights into the seismic design of long-span arch bridges in complex topographic conditions.

This study established a numerical model for soil-structure interaction (SSI) to examine the effects of the spatial incidence angle of SV waves and soil nonlinearity, utilizing viscoelastic artificial boundaries (VAB) and equivalent nodal force (ENF) method. Both the foundation's and superstructure's torsion and rocking responses were then analyzed. The findings indicate that subjected to spatially oblique incident SV waves, the rectangular foundation primarily has the rocking response while the torsional response is negligible. Furthermore, the maximum torsional and rocking angles about the x-axis at each frame floor are significantly enlarged by comparison with the perpendicular incident case. Moreover, the soil nonlinearity could increase the foundation's rocking angle and enlarge the maximum torsion and rocking responses of the structure's floors. Consequently, structural seismic damage assessment requires considering both the soil nonlinearity and incident seismic wave angles.

The seawater-seabed interface affects the dynamic response of the seabed, but a detailed study on this topic has not been performed. In this paper, a general fluid/porous medium interface is introduced into the seawaterseabed model to control the permeability of the seawater-seabed interface. Analytical solutions for the seismic response of a nearly saturated seabed under oblique incidence P and SV waves are derived. The study revealed that the impacts of the interface conditions on saturated soil and nearly saturated soil are significantly different. For a saturated seabed, when the seabed permeability coefficient is k f = 10 - 4 m /s, the interface conditions have a significant impact on the dynamic response of the seabed. The interface conditions not only have a significant impact on the dynamic behavior of the soil near the interface but also have an impact on the displacement, pore water pressure, and effective stress of the soil in the whole sediment layer. Therefore, when the seabed is gravel, coarse sand, or fine sand, it is necessary to consider the impact of fluid/porous medium interface conditions on the dynamic response of the nearly saturated seabed.