The cutter head, a pivotal component of the tunnel boring machine (TBM), endures high-risk working conditions involving high temperature, pressure, and hardness. The intricacy and variability of working conditions give rise to high torque, substantial thrust, and stochastic impact loads, ultimately leading to the damage and failure of the cutter head. In this paper, the mechanical and fatigue properties of the 8 -meter-class spoke-web composite cutter head have been investigated through the finite element method (FEM) more academically. Specifically, this article explores the typical working conditions (full load, eccentric load, and extreme condition) and different geologies (soft soil, composite formation, and hard rock) that the cutter head encounters. The findings demonstrate that under extreme working conditions, the cutter head experiences a maximum equivalent stress of 250.76 MPa. Additionally, the maximum displacement of 4.83 mm occurs on the outer ring when subjected to a one-half eccentric load. Concisely, the FEA validates the cutter head's structural rationality in stiffness and strength. Furthermore, a fatigue durability analysis of the cutter head structure was conducted using nCode DesignLife based on the stress method, determining its fatigue life range to be between 6.857E+4 and 1.253E+7 cycles, with an error not exceeding 20% compared to the theoretical fatigue life. This research provides valuable insights for the structural design and fatigue life studies of cutter heads for TBMs.

In the transitional waters of 30 to 90 m, jacket foundation has great application potential due to its advantages of light weight, high structural stiffness and good stability. In addition to the long-term normal wind and waves, the wind turbines will suffer from typhoons and waves in extreme bad weather. Currently, research on the dynamic response of jacket supported OWTs in clay under severe typhoons is very rare. The study develops a numerical method to calculate the dynamic response and fatigue damage of jacket supported OWTs under typhoon loads by incorporating a simplified single bounding surface model of clays. Through three-dimensional numerical analysis across various scenarios, this study investigates the dynamic response characteristics of jacket supported OWTs on clay soil. It also examines the impact of wind-wave coupling effects on the fatigue damage experienced by these structures. It was found that severe typhoons can lead to notable permanent tilting of the jacket foundation, thereby failing to meet the requirements of normal serviceability limits. The most critical nodes of the OWT are situated at the mudline of the pile foundations, followed closely by the bottom of the tower structure. The most significant fatigue damage occurs for wind-wave co-directional coupling loading along the orthogonal direction of the OWT. The research outcomes provide valuable guidance for enhancing the typhoon-resistant design of jacket supported OWTs.

The design of steel catenary risers (SCRs) is mainly affected by fatigue performance in the touchdown zone (TDZ), where the riser cyclically interacts with the seabed. This cyclic motion leads to seabed soil softening and remoulding. However, over an extended period of riser operations, the seabed soil undergoes a drainage because of small motion amplitudes of the floating vessel during calm weather or a limited contact with the seabed due to vessel relocation. This may cause recovery of the soil strength associated with excess pore pressure dissipation resulting in an extra fatigue damage accumulation in the TDZ. In the current study, a global SCR analysis has been conducted using a series of coded springs along the TDZ to model advanced SCR-seabed interactions. The instantaneous undrained shear strength of the soil is determined by using a recently developed effective stress framework. The effects of soil remolding and consolidation were integrated during both the dynamic motion of the SCR and intervening pause periods within the critical-state soil mechanics. The model updates the SCR-soil interaction spring at every time increment of dynamic analysis, calculating the cross- stress range while taking into account the overall configuration of the riser on the seabed. The study showed that the consolidation may result in an increased fatigue damage of about 23 %, which is currently neglected by the existing non-linear SCR-soil interaction models.

This study aims to optimize geotextile placement depth to enhance subgrade strength and achieve sustainable pavement design. Laboratory tests were conducted to characterize the soil and evaluate the effect of geotextile placement at depths of 3/4D, 1/2D, and 1/4D (where D is the total specimen depth). California bearing ratio (CBR) tests revealed that positioning the geotextile at 0.3D significantly improves subgrade strength, yielding a 78.08% increase in soaked CBR (from 5.84 to 10.4) and a 136.56% improvement in unsoaked conditions (from 3.72 to 8.8). Pavement analysis using IITPAVE software further demonstrated that geotextile placement at 0.3D effectively reduces fatigue and rutting strains, allowing reductions in pavement layer thicknesses-16.67% for bituminous concrete (BC) and dense bituminous macadam (DBM), 38.18% for water bound macadam (WBM), and 25% for granular sub-base (GSB). These optimizations lead to a cost saving of Indian Rupee36,06,610 ($42,430) per kilometer. The findings highlight the practical and economic benefits of placing geotextile at 0.3D depth (150 mm for a 500 mm subgrade), offering improved pavement performance, material savings, and enhanced sustainability. This research benefits pavement engineers, contractors, and transportation agencies by offering a sustainable, cost-efficient design strategy. Additionally, the findings provide a foundation for future research into geosynthetic reinforcement techniques under varying soil conditions, supporting the development of resilient, eco-friendly pavements.

Concrete pavements in saline soil environments of cold regions are not only subjected to vehicle loads but also severely impacted by freeze-thaw cycles (FTC) and composite salts, resulting in durability issues that shorten their designed service life. This paper induced fatigue damage in concrete based on the fatigue cycles derived from the residual strain method. It investigated the variations in the physical and mechanical properties of fatigue-damaged concrete during 100 cycles of FTC and chloride-sulfate attack, revealing the deterioration mechanisms through NMR, XRD, and SEM analysis. Utilizing the GBR algorithm, the prediction model for damage layer thickness were developed. The results showed that, due to physical crystallization, salt freeze-thaw damage, expansion of ionic attack products, and fatigue loading damage, Friedel's salt and ettringite were initially the primary products formed. Subsequently, gypsum emerged, and ultimately Friedel's salt underwent decomposition. After 10 attack cycles, the porosity and the proportion of macropores and capillary pores continued to increase, resulting in a rapid decrease in mass, dynamic elastic modulus, and flexural strength, accompanied by an increase in damage layer thickness. As fatigue damage degree increased, the pore structure degraded, thereby amplifying these changes in macroscopic properties. Incorporating basalt fibers into concrete could enhance its resistance to degradation, with the optimal dosages being 0.15 % and 0.10 %. The GBR-based model of damage layer thickness demonstrated a high degree consistency with experimental data, resulting in a correlation index of R2 = 0.989. This study lays the foundation for assessing the durability of pavement concrete in salt-freezing environments.

Although; over-saturation of pore-water has been known as potential stress agent, there hasn't been attention to subgrades behavior under extreme dry state. For improved design and construction to mitigate cracks, the two extreme states were considered at Cargo Airport site around fractured Abakaliki anticlinoria, Nigeria. Dynamic tests (remote sensing, electrical-resistivity) and static tests (Atterberg limit, Standard Penetration, Dynamic Cone Penetrometer) produced results that formed basis of modeled solutions, and revealed potential shear planes. Such planes typically reflected low friction angle between 11 degrees and 13 degrees, as well as cohesion ranging from 13 to 23 kPa; indicating isolated silty clay with Plasticity index (PI) = 1.5, and verified through stress-curves behavior in response to pore-pressure status. Such responses created various spaces between the curves. Comparing the space relations in ratios showed novel mathematical demonstration for pavements stability prediction.

This research investigates a methodology for probabilistic life prediction of buried steel pipelines subjected to external corrosion. A unified methodology is developed considering multiple stages of degradation related to external corrosion (due to soil) and fatigue. These stages include corrosion pit nucleation, pit growth, transition from pit to short crack, short crack growth, transition from short to long crack, stable long crack growth, and unstable fracture. The methodology is useful in obtaining stage-specific forecasts for the fatigue life of buried steel pipelines subjected to external pitting corrosion fatigue. State-of-the-art computational models are used to predict damage initiation and evolution at each stage. The variability in environmental, material, and loading parameters is propagated through these models to obtain a probabilistic estimate of the remaining service life (RSL) of the pipe. Insights from probabilistic RSL prediction highlight the influence of soil type and pipe coating material on corrosion fatigue life. Global sensitivity analysis is then employed to quantify the relative importance of environmental factors (pH, pipe/soil potential, and chloride concentration), material properties (threshold stress intensity factor), and the range of cyclic stress experienced by the pipe.

With the development of urban rail transit, the subway inevitably needs to run through the main channel of the South-to-North Water Diversion. With the subway being put into operation, the deformation during the construction period has been gradually stabilized, and the cyclic vibration load of the train during the operation period has gradually affected the channel structure. Therefore, in order to further investigate the effect of vibration load on the structure of the Middle Route of the South-to-North Water Diversion Project during the operation period, this paper, based on the actual cases of undercrossing projects in different regions, established a tunnel-soil-channel finite element model considering silty clay and fine sand under different burial depths by using ANSYS. The vertical vibration levels of the roadbed, tunnel wall and channel bottom are extracted and compared with the measured vibration acceleration levels. The dynamic displacement and maximum tensile (compressive) stress under different working conditions are analysed, and the fatigue life of the canal concrete structure is predicted using the obtained maximum tensile (compressive) stress. The results show that under the condition of fine sand, 1 times the hole diameter is the most unfavourable condition. In the prediction of concrete fatigue life by S-N equation, the number of trains that can pass under the most unfavourable condition is about 6.68 x 1010, which is far more than the number of trains that can pass within the service life of the tunnel.

This paper presents a comprehensive on-site decision-making framework for assessing the structural integrity of a jacket-type offshore platform in the Gulf of Mexico, installed at a water depth of 50 m. Six critical analyses-(i) static operation and storm, (ii) dynamic storm, (iii) strength-level seismic, (iv) seismic ductility (pushover), (v) maximum wave resistance (pushover), and (vi) spectral fatigue-are performed using SACS V16 software to capture both linear and nonlinear interactions among the soil, piles, and superstructure. The environmental conditions include multi-directional wind, waves, currents, and seismic loads. In the static linear analyses (i, ii, and iii), the overall results confirm that the unity checks (UCs) for structural members, tubular joints, and piles remain below allowable thresholds (UC < 1.0), thus meeting API RP 2A-WSD, AISC, IMCA, and Pemex P.2.0130.01-2015 standards for different load demands. However, these three analyses also show hydrostatic collapse due to water pressure on submerged elements, which is mitigated by installing stiffening rings in the tubular components. The dynamic analyses (ii and iii) reveal how generalized mass and mass participation factors influence structural behavior by generating various vibration modes with different periods. They also include a load comparison under different damping values, selecting the most unfavorable scenario. The nonlinear analyses (iv and v) provide collapse factors (Cr = 8.53 and RSR = 2.68) that exceed the minimum requirements; these analyses pinpoint the onset of plasticization in specific elements, identify their collapse mechanism, and illustrate corresponding load-displacement curves. Finally, spectral fatigue assessments indicate that most tubular joints meet or exceed their design life, except for one joint (node 370). This joint's service life extends from 9.3 years to 27.0 years by applying a burr grinding weld-profiling technique, making it compliant with the fatigue criteria. By systematically combining linear, nonlinear, and fatigue-based analyses, the proposed framework enables robust multi-hazard verification of marine platforms. It provides operators and engineers with clear strategies for reinforcing existing structures and guiding future developments to ensure safe long-term performance.

In recent years, the increasing use of mulching in agricultural practices has been driven by its benefits in weed suppression, soil moisture retention, and improved soil structure. However, Korean farms typically perform mulching and soil covering separately, leading to excessive labor requirements. To address this issue, this study analyzes the safety of a newly developed mulching and soil covering machine. To evaluate its structural safety, strain gauges were attached to critical points of the machine, and strain data were collected under various Power Take-Off (PTO) and engine speed conditions. The measured strain was converted into von Mises stress and maximum shear stress, and the safety factor was calculated using the maximum shear stress theory and the strain energy theory. Additionally, fatigue life was predicted using the rainflow counting method, the Goodman equation, and Palmgren-Miner's rule. The results indicate that the safety factor ranged from 1.65 to 16.54 based on the maximum shear stress theory and 2.42 to 19.83 based on the strain energy theory, confirming that the machine can withstand operational loads without failure. Furthermore, fatigue life prediction revealed that the lowest estimated fatigue life is 14,575 h, equivalent to approximately 607 years of continuous use. These findings demonstrate that the developed machine possesses high safety, making it a viable solution for improving efficiency in mulching and soil covering operations.