Large-span corrugated steel utility tunnels are widely used owing to their large spatial spans and excellent mechanical properties. However, under seismic forces, they may experience significant deformation, making repair challenging and posing a serious threat to personal safety. To study the seismic performance of corrugated steel utility tunnels, an equivalent orthotropic plate was introduced, and a simplified three-dimensional refined finite element model was proposed and established. Considering the site conditions of the structure, the structural parameters, and different seismic input conditions, a detailed analysis was conducted using the endurance time analysis method. The results indicated that the simplified model agreed well with the experimental results. The seismic input conditions significantly affected the relative deformation of the structure. Under the action of P waves (compression waves) and P + SV waves (compression and shear waves), the deformation of the upper part of the structure was relatively uniform, whereas under the action of SV waves (shear waves), the deformation of the crown was more evident. The greater the burial depth of the structure, the stronger the soil-structure interaction, and the smaller the increase in relative deformation. In soft soil, the structure was more likely to be damaged and should be carefully observed. Additionally, increasing the corrugation profile of the steel plates during the design process was highly effective in enhancing the overall stiffness of the structure. Based on the above calculation results, the relative deformation rate was proposed as a quantitative index of the seismic performance of the structure, and corresponding values were recommended.

This paper investigated the influence of chloride ion erosion and aftershocks on the seismic performance of transmission tower structures in Xinjiang, China. Based on chloride ion diffusion laws and steel corrosion mechanisms, the time-dependent deterioration of reinforced concrete was analyzed. Finite element models considering corrosion effects were established for different ages(0a,50a,70a,100a) in a saline soil environment using ANSYS/LS-DYNA. Ten mainshock-aftershock sequences tailored to the site type was constructed, and the cumulative damage index (DI) was adopted as a metric for structural damage. The results indicate that aftershocks and steel corrosion significantly impact transmission tower damage, with damage extent influenced by the intensity of the main shock. Stronger aftershocks cause greater additional damage, potentially exceeding 50 % cumulative damage when their amplitude matches the main shock. Steel corrosion alone can lead to nearly 40 % damage. Its influence on seismic fragility varies with damage state, especially under moderate to complete damage, where longer service life increases vulnerability. The coupling of corrosion and aftershocks further elevates structural vulnerability. Hence, in seismic assessments of transmission towers in saline soil environments, combined effects of main and aftershocks, and corrosion, must be accounted for.

The main problem in expansive soil treatment with steel slag (SS) is the relatively slow hydration reaction that occurs during the initial period. To circumvent this, SS-treated expansive soil activated by metakaolin (MK) under an alkaline environment was investigated in this study. Based on a series of tests on the engineering properties of the treated soil, it can be reported that SS could enhance the strength and compressibility of expansive soil, with strength increasing by approximately 108 % for SS contents exceeding 10 % compared to 3 % lime-treated soil, and the compression index reducing by 20 %. Further addition of MK plays a dual role, enhancing strength for higher SS content while excessive MK leads to strength reduction due to insufficient pozzolanic reactions and hydration product transformation. Expansive and shrinkage behaviors are notably improved, with a 5 % increase in SS content reducing the free swelling ratio by 0.66 %-5.9 %, and the combination of 15 % SS and 6 % MK achieving a nearly 300 % reduction in the linear shrinkage ratio. Microstructural analysis confirms the formation of hydration gels, densification of the soil structure, and reduced macropores, validating the enhanced mechanical and shrinkage resistance properties of the SS-MK-treated expansive soil. Additionally, to develop predictive models for mechanical and the content of hardening agents (SS and MK), the experimental data are processed utilizing a backpropagation neural network (BPNN). The results of BPNN modeling predict the mechanical properties perfectly, and the correlation coefficient (R) approaches up to 0.98.

Soil-steel composite bridges (SSCBs) are commonly utilized as overpasses. In the majority of existing studies, the transverse structural performance of SSCBs is primarily focused on, while neglecting their longitudinal structural performance. The aims of this paper are to clarify the longitudinal properties and compensate for the paucity of research on the longitudinal structural performance of SSCBs. In current study, field tests were conducted on a SSCB case bridge in a mining area, both in the construction stage and post-construction stage. Subsequently, longitudinal differences in the structural settlements, deformations, and hoop strains were analyzed. Additionally, a refined three-dimensional finite element model was developed and verified to analyze the transfer behavior of soil pressure above the structure along the longitudinal direction. The results indicate that in the construction stage, the difference in the soil-covered height primarily account for the differences in structural performances along the longitudinal direction. At the end of backfilling, the settlements, deformations, and hoop strains in the middle are all greater than those in the end sections. In the post-construction stage, further developments of longitudinal structural characteristics occur due to creep deformation of the foundation soil and disturbances from mining trucks. One year after construction, the structural characteristics have stabilized. The maximum settlement reaches -1.014 m and the maximum settlement difference reaches 0.365 m. The differential settlement ratio, at 0.62 %, remains within the 1 % limit specified in the CHBDC code. Due to longitudinal settlement differences, the soil pressure in the higher settlement zone is transferred to the lower settlement zone by the longitudinal soil arching effect, which benefits the load-bearing capacity of SSCBs.

Determining the optimal damping value of the isolation system in tall structures is challenging as it requires parametric studies and time-consuming nonlinear time-history analyses. Consequently, the influence of different parameters, such as displacement limitation, on the optimal damping of isolators in tall structures remains unclear. This study aims to investigate the optimal damping of isolators in tall structures under two scenarios: a) changing the displacement capacity of the isolators in proportion to the increase of damping (variable gap); b) maintaining a constant displacement capacity of the isolators as the damping increases (constant gap). The study also explores the influence of two additional parameters on the optimal damping of the isolation system, namely the ratio of isolator to superstructure period (TM/TS) and the soil type. The optimal design procedure is illustrated with reference to a case-study 14-story isolated steel structure with an ordinary concentrically braced frames (OCBF) system, isolated with the triple friction pendulum isolator (TFPI) system. The modified endurance time (MET) method is utilized to analyze the seismic response of the case-study structure under increasing levels of earthquake hazard. The analysis reveals that increasing damping in both constant and variable gap modes can effectively reduce the damage level of the structure. However, the effectiveness of increasing damping is limited and influenced by factors such as soil softness and the TM/TS ratio. The optimal damping values are determined based on the desired performance levels for both structural and nonstructural acceleration-sensitive components.

The shear stress-shear displacement relationship and shear strength parameters at the pipe-soil interface are crucial for calculating jacking force. To investigate these properties, a series of tests were performed using a large-scale direct shear device to examine the shear mechanics of the steel-sand interface under various conditions. The effects of particle size, normal stress, and slurry concentration on shear performance were analyzed macroscopically. Additionally, the evolution of interface micro-behavior was studied using discrete element software PFC 2D. The experimental results indicate that the particle size of the sand has a significant impact on the shear stress-shear displacement curve of the interface, with smaller particle sizes requiring greater shear stress to achieve stability during shear. The strain-softening degree of sand is affected by normal stress. The shear stress-shear displacement curve is more significantly affected by particle size with the increase of normal stress. By considering different slurry concentrations, it is observed that both the shear stress and the sliding friction coefficient reached a minimum value at a concentration of 14%. The numerical simulation results indicate that particle motion causes changes in the distribution of particle structures. The distribution of particle force chains is relatively dispersed before shear. Particles move vigorously toward the shear interface, and force chains primarily concentrate on the shear interface during shear. Shear stress is transmitted through particle movement, and particle displacement causes shear dilation within the contact zone. Particles essentially cease moving toward the shear interface, and the force chains no longer change once the shear band is formed.

Steel slag is an environmentally friendly material with significant potential as an alternative to gravel for encased columns in soft ground improvement. However, the performance of composite foundations improved by geosynthetic-encased steel slag columns (GESSC) remains somewhat unclear. This study compares the working performances of GESSC and geosynthetic-encased stone column (GESC) composite foundations, as well as untreated foundations, through a series of large-scale experiments. Additionally, cone penetration tests were conducted on both the untreated and GESSC foundations to assess changes in soil strength before and after loading. The results show that both GESSC and GESC significantly increase the bearing capacity of soft clay, demonstrating an approximate 10-fold increase compared to the untreated foundation. The GESSC composite foundation marginally outperforms the GESC in bearing capacity during the elastoplastic stage. Furthermore, upon reaching the ultimate bearing capacity, the GESSC exhibits greater radial strain and less settlement than the GESC, owing to the unique redistribution of steel slag and gravel. Both types of foundations effectively transmit vertical pressure to deeper soil layers, with GESSC demonstrating superior load transmission capabilities and a more uniform distribution of soil stress along the depth. The excess pore-water pressure and its accumulation rate within the GESSC foundation are typically lower than those in the GESC composite foundations, underscoring the superior drainage capabilities of GESSC. This enhanced drainage capacity leads to a higher consolidation ratio within the soil, resulting in a significant improvement in soil strength after loading compared to the untreated foundation.

Due to the environmental pollution caused by the production and consumption of cement, the demand for new and environmentally friendly methods to improve and strengthen the soil is increasing. In addition, reinforcing the soil with steel fibers improves the mechanical properties, including the formability and bearing capacity of the soil. The purpose of this research is to evaluate the effect of zeolite on the behavior of cemented sand soil reinforced with steel fibers. In the following, the unconfined compressive strength (UCS) test was used to check the compressive strength, and the flexural strength (FT) test was used to check the flexural. It should be mentioned that to improve the soil from cement in the amount of 5% by weight, zeolite in the amount of 0, 25, 50, 75 and 100% was used instead of cement, as well as steel fibers in the amount of 2% and random distribution in the curing of 28-day. In the results of unconfined compressive strength tests, the best replacement percentage of zeolite instead of cement in sandy soil was 25%, which initiated an increase in unconfined compressive strength and an increase in the failure strain of the sample. In the results of flexural strength tests, 25% of zeolite to replace cement in sandy soil affected the greatest increase in flexural strength and increased soft behavior. In addition, with the addition of steel fibers, the samples endured much more displacements than those without fibers. [GRAPHICS]

Stray currents can cause electrochemical corrosion of metals, accelerate material aging, and even pose safety hazards. By studying corrosion behavior and speed, the degree of damage caused by stray currents to metals can be evaluated, protective measures (cathodic protection, insulation design, etc.) can be optimized, the service life of metal structures can be extended, maintenance costs can be reduced, and the safe and stable operation of power systems and infrastructure can be ensured. Therefore, research on the electrochemical corrosion behavior and velocity analysis method of metals under AC stray current. This article mainly explores the influence of different alternating current (AC) stray current densities on the electrochemical corrosion behavior of 316L stainless steel. The experiment used Yingtan soil simulation solution, and analyzed the changes in indicators through electrochemical testing, corrosion morphology observation, and corrosion rate calculation. The results indicate that the corrosion rate of 316L stainless steel in soil simulation solution shows a trend of first decreasing and then increasing when disturbed by AC stray current density. In the initial stage, the synergistic effect of high concentrations of Cl-and O2 leads to a faster corrosion rate. Over time, corrosion products increase and form a film layer, which hinders harmful ion erosion and slows down the corrosion rate. However, after prolonged immersion, the corrosion product film may crack, crevice, or even peel off, causing crevice corrosion and galvanic corrosion, accelerating the corrosion process. AC stray current forms a tip discharge through the defect, further exacerbating corrosion. With the increase of AC interference current density, the corrosion rate of 316L stainless steel significantly increases, and the main corrosion form changes from uniform corrosion to localized corrosion. When the stray current density is greater than or equal to 200 A/m2, the corrosion degree of 316L stainless steel under the peeling coating reaches severe corrosion. This study is of great significance for understanding the impact of AC stray currents on metal corrosion and developing effective protective measures.

With the widespread application of deep excavation projects, deformation control of diaphragm walls and management of surrounding soil displacement have become major challenges in the engineering field. To address these issues, this study proposes a prefabricated multi-limb composite concrete-filled steel tube (CFST) internal support system. The mechanical performance and deformation characteristics of the fixed ends of the system were systematically analyzed through axial compression tests and numerical simulations.First, based on the CFST stress-strain model, the constitutive model was modified to account for the effects of stiffening ribs, and a stress-strain relationship model for mold bag concrete was introduced. The simulation results demonstrate that the modified model can accurately predict the stress behavior of the fixed ends. Next, to characterize the overall mechanical response of the structure, a load-displacement relationship model was established. This model, which is closely related to the CFST strength grade, effectively captures changes in the structural performance.The results indicate that during loading, the CFST internal support system exhibits good stiffness and load-bearing capacity. With an increase in the concrete strength grade, the yield load increases by 12 %, and the ultimate strain decreases by 27.76 %, significantly enhancing the mechanical performance of the structure. This study not only deepens the understanding of the design principles for CFST internal support systems but also introduces new theoretical frameworks and calculation methods, providing strong support for engineering design with broad application prospects.