Freeze-thaw cycles in seasonally frozen soil affect the boundary conditions of aqueducts with pile foundations, consequently impacting their seismic performance. To explore the damage characteristics and seismic behaviour of aqueduct bent frames in such regions, a custom testing apparatus with an integrated cooling system was developed. Two 1/15 scale models of reinforced concrete aqueduct bent frames with pile foundations were constructed and subjected to pseudo-static testing under both unfrozen and frozen soil conditions. The findings revealed that ground soil freezing has minimal impact on the ultimate bearing capacity and energy dissipation of the bent frame-pile-soil system, but significantly enhances its initial stiffness. Additionally, the frozen soil layer exerts a stronger embedding effect on the pile cap, ensuring the stability of the pile foundation during earthquakes. However, under large seismic loads, aqueduct bent frames experience greater damage and residual deformation in frozen soil compared to unfrozen soil conditions. Therefore, the presence of a seasonally frozen soil layer somewhat compromises the seismic performance of aqueduct bent frames. Subsequently, a finite element model considering pile-soil interaction (PSI) and frozen soil hydro-thermal effects was developed for aqueduct bent frames and validated against experimental results. This provides an effective method for predicting their seismic behaviors in seasonally frozen soil regions. Furthermore, based on the seismic damage characteristics of aqueduct bent frame with pile foundations observed in pseudo-static tests, a novel selfadaptive aqueduct bent frame system was designed to mitigate the adverse effects of seasonally frozen soil layer on seismic performance. This system is rooted in the principle of balancing resistance with adaptability, rather than solely depending on resistance. The seismic performance of this innovative system was then discussed, providing valuable insights for future seismic design of reinforced concrete aqueduct bent frames with pile foundations in seasonally frozen soil regions.

Although considerable research has explored the static and seismic bearing capacity of strip footings on slopes or excavations, the influence of clay strength anisotropy on the bearing capacity of strip footing near excavations, specifically considering pseudo-dynamic conditions, remains unexplored. This study used the finite element limit analysis (FELA) method to evaluate the impact of clay strength anisotropy on the seismic bearing capacity of strip footings. The effects of various dimensionless parameters on the bearing capacity were examined, which include shear wavelength, the setback distance ratio, vertical height ratio, soil strength ratio, soil strength heterogeneity, anisotropic ratio, and horizontal and vertical acceleration coefficients. Design charts were developed to compute the seismic bearing capacity of strip footings on nonhomogeneous and anisotropic excavations under pseudo-static conditions. Furthermore, the effects of vertical acceleration coefficients and shear wavelength on the seismic bearing capacity of strip footing near excavation in nonhomogeneous and anisotropic soils were investigated.

Earthquakes are one of the natural occurrences that can lead to massive disasters, either on structures or infrastructure. The seismic response and performance of underground infrastructure such as tunnels against earthquake vibrations is predictably severe due to the complex interaction between tunnels and the surrounding soil, especially one embedded in poor soil material properties. In view of this, previous experiences of tunnel damages subjected to earthquake loads have been reported in the literature. Thus, rigorous analysis is necessary to provide indepth knowledge and understanding of the seismic response of tunnels which beneficial to engineering practitioners in especially in early design stage in order to avoid the future risk of tunnel damage and failure during an unpredictable earthquake event. The aim of this study is to investigate the effect of overburden depth on seismic response of tunnels using the simplified pseudo-static analysis, while simultaneously to emphasize the shortcoming of conventional closed-form solution. This study presents a two-dimensional (2D) simplified pseudo-static analysis of soil-tunnel model embeded at 10m and 20m overburden depth subjected to increasing levels of seismic intensity at the transverse direction of tunnel axis. The numerical investigation was performed using the finite element program PLAXIS 2D. The circular shaped tunnel lining are assumed to be elastic, while the soil is considered as homogeneous, and isotropic in plane strain condition. Considering the complex soil-tunnel interaction, the tunnel lining and soil interface is assumed as no-slip condition. The numerical result of pseudo-static analyses were compared with the conventional closed-form Wang's analytical solution to verify the reliability of the obtained results. The results denoted that the tunnel embedded at 10 m overburden depth experienced considerable seismic-induced deformation and structural forces than tunnel buried at 20 m depth. The deformation and seismic induced structural forces of tunnel increased with increment on the magnitude of earthquake loadings. Thus, it can be concluded that the shallow tunnel suffered more damages compared to the tunnel embedded at deeper depth. Overburden depth of tunnel plays a significant role in modifying the seismic response of tunnel apart of the imposed magnitude of earthquake loadings. The conventional closed-form analytical method tends to overestimate the seismic response of tunnel compared to numerical pseudo-static analysis.

The occurrence of earthquake events has caused numerous causalities and economic losses within the construction industry in the past and present years. However, people have insufficient knowledge and awareness of the impact of earthquakes, especially in understanding the seismic response of complex underground construction industries such as tunneling. Careful consideration of the impact of earthquakes on such structures is crucial due to previous experiences of catastrophic earthquake events that severely damaged underground structures. This study aims to investigate the effect of different soil material properties ( i.e., soft soil and rock) on the seismic response of circular tunnels under increasing earthquake ground motion using simplified pseudo-static analysis, while simultaneously emphasizing the shortcomings of conventional closed-form solutions. To achieve this, a two-dimensional (2D) simplified pseudo-static analysis of a soil-tunnel model embedded at 20m depth was investigated under increasing levels of seismic intensity at the transverse direction of the tunnel axis using PLAXIS 2D software. The tunnel is modeled as a circular shape with a 0.5m thick tunnel lining embedded at a depth of 20 m from the ground surface in two different types of soil profiles i.e. soft soil and rock. The soil is treated as a single-phase medium without excess pore pressure. The six seismic intensities of peak ground acceleration (PGA) ranging from 0.1g to 0.6g were considered in this study. For validation purposes, the numerical results of pseudo-static analyses were verified with the analytical closed-form solution using Wangs' method 1993. The findings indicate that the tunnel embedded in soft soil experienced maximum structural forces for bending moments and axial forces compared to rock. Results denoted that the seismic responses of the tunnel increased with the increment of earthquake magnitude and its epicenter. Notably, the results of analytical methods seemed to be underestimated compared to numerical analyses.

Integral abutment bridges (IABs) have been widely applied in bridge engineering because of their excellent seismic performance, long service life, and low maintenance cost. The superstructure and substructure of an IAB are integrally connected to reduce the possibility of collapse or girders falling during an earthquake. The soil behind the abutment can provide a damping effect to reduce the deformation of the structure under a seismic load. Girders have not been considered in some of the existing published experimental tests on integral abutment-reinforced-concrete (RC) pile (IAP)-soil systems, which may not accurately represent real conditions. A pseudo-static low-cycle test on a girder-integral abutment-RC pile (GIAP)-soil system was conducted for an IAB in China. The experiment's results for the GIAP specimen were compared with those of the IAP specimen, including the failure mode, hysteretic curve, energy dissipation capacity, skeleton curve, stiffness degradation, and displacement ductility. The test results indicate that the failure modes of both specimens were different. For the IAP specimen, the pile cracked at a displacement of +2 mm, while the abutment did not crack during the test. For the GIAP specimen, the pile cracked at a displacement of -8 mm, and the abutment cracked at a displacement of 50 mm. The failure mode of the specimen changed from severe damage to the pile top under a small displacement to damage to both the abutment and pile top under a large displacement. Compared with the IAP specimen, the initial stiffness under positive horizontal displacement (39.2%), residual force accumulation (22.6%), residual deformation (12.6%), range of the elastoplastic stage in the skeleton curve, and stiffness degradation of the GIAP specimen were smaller; however, the initial stiffness under negative horizontal displacement (112.6%), displacement ductility coefficient (67.2%), average equivalent viscous damping ratio (30.8%), yield load (20.4%), ultimate load (7.8%), and range of the elastic stage in the skeleton curve of the GIAP specimen were larger. In summary, the seismic performance of the GIAP-soil system was better than that of the IAP-soil system. Therefore, to accurately reflect the seismic performance of GIAP-soil systems in IABs, it is suggested to consider the influence of the girder.

Rammed earth building has garnered attention from researchers due to its low energy consumption and excellent thermal performance. However, addressing the issue of low seismic performance in rammed earth buildings still lacks effective solutions. This study investigated the influence of embedded steel wire mesh and bamboo reinforcement mesh on the in-plane seismic performance of rammed earth walls through pseudo-static tests. Four half-scale models of rammed earth walls were constructed, each with dimensions of 1900 mm in length, 1200 mm in width, and 250 mm in height. The experimental results were compared in terms of failure mode, hysteresis response, lateral bearing capacity, displacement, ductility, stiffness degradation, damage index, and energy dissipation capability. The peak ground acceleration (PGA) for each specimen was calculated using the N2 method to assess their seismic performance. The results indicated that both steel wire mesh and bamboo reinforcement mesh can significantly enhance the seismic performance of rammed earth walls. Finally, based on the hysteresis curves of the specimens and the strain test results of the steel wire mesh or bamboo reinforcement mesh, this study proposed a hysteretic model and lateral bearing capacity calculation formula for rammed earth walls.

Given the horizontal low cycle reciprocating motion of the integral abutment bridge pile foundation under cyclic loading of temperature, the traditional reinforced concrete (RC) pile cannot be applied to accommodate the large longitudinal deformation appropriately because of its significant lateral stiffness and its weak cracking resistance; the surface area of the H-shaped steel (HS) pile is small, it cannot provide enough friction in deep soft soil areas, and due to its high cost and easy buckling during pile driving, it is not suitable for domestic popularization. This paper proposes a new concept of composite stepped pile consisting of HS and rectangular RC piles, the RC pile in the lower provide sufficient friction, reduce the length of the pile to save materials, and the stability is also good; the HS pile in the upper has good horizontal compliance, which can meet the horizontal deformation requirements of the integral abutment bridge. Pseudo-static tests of model piles were carried out of one HS pile and two HS-RC stepped piles with different stiffness ratios of 0.25 and 0.5. The test results show that the cracking displacements of HS-RC (0.25) and HS-RC (0.5) stepped piles are 10 similar to 15 mm and 5-8 mm, respectively, and the corresponding cracking loads are 4.66-5.99 kN and 3.22-4.52 kN, indicating the stepped pile with a smaller stiffness ratio has a stronger crack resistance; The HS-RC stepped pile has larger plastic deformation capacity, and its initial stiffness of pile-soil system is smaller, 0.48 times and 0.57 times that of RC piles, respectively, and can be applied to integral abutment bridges. Based on these tests, a finite element (FE) model using OpenSees software was validated and used for a detailed numerical simulation analysis considering the pile-soil interaction of HS-RC stepped piles. Simulating the low-cycle reciprocating motion of full-scale stepped piles under the control of displacement loads, the effects of stiffness and length ratios on the load-bearing performance of stepped piles were studied and analyzed. The FE simulation found that the stepped pile's crack resistance can be improved by reducing the stiffness of the HS pile's upper section. Still, the stepped pile's horizontal load-bearing capacity (deformation) is very low if the stiffness is unreasonably small. Furthermore, increasing the upper HS pile length cannot significantly change the horizontal load-bearing capacity of the stepped pile because the deeper pile below the inflection point will not significantly take part in the bending deformation. According to the simulation, the theoretical optimum ratio is 0.33. With the practical construction and soil property variance, it is recommended that the length ratio of the stepped pile be around 0.33 to 0.5.

This paper presents the design and commissioning of a novel pseudo-static test apparatus for underground structures that accounts for soil-structure interaction by simulating the soil with suitably designed springs. The developed apparatus was employed to conduct 1:10 large scale tests on a two-story three-span prefabricated subway station structure. Two comparative cyclic load tests were conducted: one involved the developed springs-structure system; and one involved the structure alone (no springs). The test results demonstrated important differences in the damage location, damage degree, bearing capacity, and deformation capacity of the prefabricated subway station structure under the two loading conditions (i.e., with and without springs). The presence of springs (i.e., soil-structure interaction) enhanced the lateral collapse resistance of the underground structure and affected the inter-story displacement ratio (IDR) between the upper and lower layers of the two-story prefabricated subway station structure. However, it did not affect the deformation coordination of the walls and columns of each layer. A finite element model of the prototype station was also established to conduct dynamic time history analysis simulating the soil-structure interaction. The results from the dynamic analysis validated the effectiveness of the pseudo-static test method employing the spring-structure system. The excellent agreement between the calculated dynamic responses and the responses obtained from the pseudo static tests confirmed the ability of the developed apparatus to conduct seismic tests on complex large-scale underground structures such as prefabricated subway stations. Thus, this test methodology might be utilized to attain valuable insights into the seismic performance of prefabricated subway stations at a relatively low cost and effort.