Search Results (209)

This study numerically examined the anchorage mechanism of rebar hooks under varying straight development lengths, including high stress levels. A three-dimensional rigid body spring model (3D RBSM) was used for the investigation and successfully reproduced the experimental pullout test stress–slip relationships and inner–outer strain distributions for the rebar hook with and without a straight development length. A validated numerical model was used to assess local concrete stresses and internal crack propagation, enabling a clear interpretation of how straight development length influences the anchorage mechanism. The results revealed that increasing straight development length increases stiffness, reduces rebar strains and concrete stresses in the hook region, promotes crack formation around the rebar surface, and forms maximum tensile stresses closer to the top surface, ultimately resulting in earlier splitting failure at high rebar stress levels. A comparison of cases with and without hooks shows that combining the hook with straight development length improves stress distribution, delays crack propagation, and increases anchorage by reducing tensile stress concentrations near the top surface and side faces. These findings provide valuable insights into the role of straight development length in the anchorage performance of 180-degree rebar hooks. Full article

The large deformation of soft rock within tunnels not only induces cracking in the initial supports and distortion of steel arches but also compromises the structural integrity of the secondary lining. In this study, we first examined the cracking characteristics of the secondary lining on both sides of the Baoligang Tunnel situated in a strong tectonic zone. A total of 257 cracks were identified, with 118 located on the left side of the tunnel and 139 on the right side. The triaxial compression test revealed that the failure characteristics of carbonaceous slate are mainly caused by shear slip failure due to the presence of weak bedding planes. Subsequently, a tailored blasting charge structure was designed to demolish the reinforced concrete secondary lining. This design incorporated a dense arrangement of blasting holes and interval charging techniques applied to the arch shoulders and sidewalls of the blasting zone, effectively fracturing the secondary lining in the left tunnel of the Baoligang Tunnel. Finally, an analysis was conducted based on vibration signals recorded during the dismantling process from three representative sections. The recorded vibration velocities from Case 1 indicate that the explosive charge has a relatively minor impact on the lining of the right tunnel. The peak particle velocity (PPV) recorded from the damaged lining closest to the blast center on the left side is 31.48 cm/s, exceeding the allowable vibration standard. Thereafter, the Hilbert–Huang Transform (HHT) was employed to identify the dominant frequency of the recorded vibration signals, which was determined to be 64 Hz. In Case 2, the PPVs at all monitoring points are below the vibration control standard for traffic tunnels. In Case 3, the PPVs suggest that the vibration has a minimal effect on the newly installed initial support. Full article

To evaluate the fire safety performance of the joint region in prefabricated buildings, specifically when the grout in the slurry layer is under an unconstrained state. Total 54 pull-out specimens were designed to investigate the effects of elevated temperatures (20 °C, 200 °C, 300 °C, 400 °C, 500 °C, and 600 °C) and steel bar positions (center, mid-side, and corner) on the bond behavior between the grout and steel rebars. The failure modes, bond strength, ultimate displacement, and load–slip curves of the specimens were recorded. The peak load of the specimens with the temperature increasing first rose and then declined, exhibiting a trend consistent with the variation in compressive strength of the grout with temperature. At 600 °C, the ultimate loads of the center, mid-side, and corner specimens decreased by 53.46%, 52.53%, and 51.28%, respectively, compared with those at ambient temperature. At ambient temperature, the bond strength of the mid-side specimen was 11.24% lower than that of the central specimen, but 19.98% higher than that of the corner specimen. At 500 °C, the bond strength of the mid-side and corner specimens decreased by 15.76% and 39.26%, respectively, compared with that of the center specimen. The failure mode changed from steel-rebar fracture to pull-out failure due to the high temperature exposure and the steel rebar position. Finally, based on the post-heating strength test results of grout specimens, a bond strength calculation formula and a bond–slip constitutive model, considering both steel rebar position and temperature, were developed, achieving a correlation coefficient (R²) close to 1.0. Full article

Understanding how strain is transferred across the interior of tectonic plates is fundamental to quantifying lithospheric deformation. The Central Anatolia Transition Zone (CATZ), situated between the North and East Anatolian fault systems, provides a unique natural laboratory for investigating how continental deformation evolves from localized faulting to distributed shear. In this study, we integrate InSAR analysis with Global Navigation Satellite System (GNSS) velocity data, and stress tensor inversion with supporting gravity and seismic datasets to characterize the geometry, kinematics, and geodynamic significance of the CATZ. The combined geodetic and geophysical observations reveal that the CATZ is a persistent, left-lateral deformation corridor (i.e., elongated zone of Earth’s crust that accommodates movement where the landmass on the opposite side of a fault system moves to the left relative to an observer) accommodating ~4 mm/yr of shear between the oppositely moving eastern and western sectors of the Anatolian Plate. Spatial coherence among LiCSAR-derived shear patterns, GNSS velocity gradients, and regional stress-field rotations defines the CATZ as a crustal- to lithospheric-scale transition zone linking the strike-slip domains of central Anatolia with the subduction zones of the Hellenic and Cyprus arcs. Stress inversion analyses delineate four subzones with systematic kinematic transitions: compressional regimes in the north, extensional fields in the central domain, and complex compressional–transtensional deformation toward the south. The CATZ coincides with zones of variable Moho depth, crustal thickness, and inferred lithospheric tearing within the retreating African slab, indicating a deep-seated origin. Its S-shaped curvature and long-term evolution since the late Miocene reflect progressive coupling between upper-crustal faulting and deeper lithospheric reorganization. Recognition of the CATZ as a lithospheric-scale transition zone, rather than a discrete active fault, refines the current understanding of Anatolia’s kinematic framework. This study demonstrates the capability of integrated satellite geodesy and stress modeling to resolve diffuse intra-plate deformation, offering a transferable approach for delineating similar transition zones in other continental regions. Full article

On 7 January 2025, an Mw 7.0 earthquake struck Dingri County, Shigatse, Tibet. This was the largest event in the region in recent years. Analysis of the Dingri earthquake is urgent for understanding the coseismic slip and early postseismic deformation characteristics. In this study, the coseismic characteristics were analyzed by using Lutan-1 and Sentinel-1 data with the Differential Interferometric Synthetic Aperture Radar method, and then the Okada elastic half-space dislocation model was used to invert the coseismic slip distribution of the seismogenic fault. The postseismic characteristics were analyzed by Sentinel-1 ascending and descending orbits, then time-series deformation results were obtained with the Small Baseline Subset InSAR method. The main results are as follows: (1) The maximum coseismic subsidence is −2.03 m and the maximum coseismic uplift is 0.68 m, the coseismic deformation is concentrated on the west side of the new rupture trace generated by the coseismic events; (2) the ruptured fault is dominated by normal faulting with a minor strike-slip component, and the slip is mainly distributed at depths of 0–15 km, with a maximum slip of about 3.97 m; (3) the deformation characteristics of the fault in the postseismic stage are basically consistent with those during the coseismic stage. The research results play an important role in understanding the earthquake fault tectonic activities. Full article

This paper investigates a friction oscillator model in both its Integer-Order and Fractional-Order formulations. The lack of classical solutions for the governing differential equations with discontinuous right-hand sides is addressed by adopting a Differential Inclusion framework. Using Filippov regularization, the discontinuity is replaced by a set-valued map satisfying appropriate regularity conditions. Selection theory is then applied to construct a Lipschitz-continuous, single-valued function that approximates the set-valued map. This procedure reformulates the discontinuous initial value problem as a continuous, single-valued one, thereby providing a rigorous justification for the proposed approximation method. Numerical simulations are performed to study stick–slip attractors in both the Integer-Order and Fractional-Order cases. The results demonstrate that, in contrast to the Integer-Order system, periodic attractors cannot occur in the Fractional-Order regime. Full article

This study presents a comprehensive evaluation of a novel spinneret design to enhance polymer melt extrusion performance in fibre spinning production. Computational fluid dynamics (CFD) simulations using ANSYS Polyflow 2024 R2 are employed to analyse flow behaviour, pressure distribution, and shear profiles within the die. The novel design demonstrates improved flow uniformity, reduced pressure fluctuations, and minimized high-shear regions compared to a baseline spinneret. Experimental validation is conducted through side-by-side extrusion tests using polypropylene and thermoplastic polyurethane, confirming the simulation results. Throughput efficiency tests further reveal that the novel spin pack design significantly reduces residence times by 16% and accelerates purging cycles, indicating fewer polymer stagnation zones and enhanced material changeover efficiency. The computational parametric study conducted on PP shows that the novel design demonstrates improved flow uniformity and a significant reduction in operating pressure, achieving an 11% decrease in die-head pressure compared to the baseline spinneret. Additionally, the optimized geometry successfully minimizes high-shear regions while maintaining a manageable maximum shear rate increase of approximately 19% at the walls, which aids in preventing wall slip. These enhancements lead to lower extrusion pressures and more consistent processing across various polymers. By minimizing material waste and improving process reliability, the new spinneret design contributes to a more sustainable, cost-effective manufacturing process. Overall, these improvements provide a valuable framework for advancing extrusion technologies and optimizing spinneret geometries for high-performance polymer extrusion. The novelty of this work lies in introducing a spinneret geometry specifically optimized to minimize melt residence time, an outcome directly linked to reduced material degradation and waste. Full article

This study proposes an indirect approach that estimates roll force from motor current signals in a rolling mill. Motor current is first converted to motor torque using an induction-motor equivalent-circuit model, then to roll torque via the gear ratio, and finally to roll force through a torque-arm relationship. A laboratory-scale rolling mill was designed and fabricated to experimentally validate the approach. Two torque-conversion schemes were examined: Method A, which determines the slip of the induction motor from measured rpm and recalculated motor parameters, and Method B, which estimates slip from measured motor current and applies a finite element (FE)–based response surface function to calibrate the converted torque. The converted roll torques were validated against FE analysis, and the resulting roll forces were compared with load cell measurements under various rolling conditions. Deviation, defined as the average difference between the FE-predicted torque and the converted torques, ranged from −11.9% to 28.8% for Method A and −7.2% to 13.8% for Method B. Roll force deviations from measurements ranged from −14.1% to 14.9% for Method A and −3.7% to 14.2% for Method B. Method A provided a straightforward and computationally light conversion route but was more sensitive to rpm-measurement noise, whereas Method B yielded smoother temporal behavior at the cost of FE-based calibration. The results demonstrate that both methods can reproduce the overall evolution of roll torque and roll force using only motor-side measurements, offering a practical foundation for real-time monitoring in rolling mills where stand-by-stand load cells are unavailable. Full article

Under cyclic loading, almost immediately after its onset, a surface layer forms where hardening and softening processes occur. The interaction of plastic deformation traces with each other, and with other structural elements, leads to the formation of a characteristic microstructure on the surface of a component subjected to cyclic loading. The set of factors (conditions) acting during cyclic loading determines the nature of slip band accumulation, the integral structurally sensitive fatigue parameter, expressed as the slope of the left side of the fatigue curve linearized in logarithmic coordinates, and the location of the breaking point on the fatigue curve in the high-cycle region. A combined review of numerous data on the fatigue of metals, obtained under various combinations of factors, and the generalization of these results through a normalization procedure for obtaining the relative (recalculated) parameters of fatigue, allows us to derive a universal method for “S-N” curve prediction. However, extensive generalization decreases the prediction accuracy for specific cases; therefore, it is proposed to form limited generalized dependencies corresponding to specific operating conditions. This paper evaluates the accuracy of fatigue limit prediction using generalized and limited-generalized relationships of fatigue recalculated parameters for various fatigue curves obtained from independent experimental data. Full article

A plane strain analytical model was developed for the interaction between inclined multilayered rock strata and concrete tunnel lining in deep buried tunnels, with both structures treated as homogeneous isotropic elastic bodies and two contact modes, no-slip and full-slip, considered. A non-iterative complex variable function method was employed, by which analytical challenges in multiply connected domains were overcome and explicit stress and displacement solutions were obtained. Validation was performed through boundary-condition checks and comparative numerical simulations. The results show that under different tangential contact modes, layer inclinations, and lateral pressure coefficients, the stress error on the inner surface of the lining remains in the order of 10⁻² Pa. The stress and displacement components on both sides of each interface satisfy the associated continuity conditions with excellent agreement. The proposed analytical method nearly perfectly satisfies all boundary and continuity conditions. Under non-hydrostatic loading conditions, the numerical and analytical results for different tangential contact modes also show excellent agreement. The von Mises stress errors are generally controlled within 0.03 MPa, and the maximum relative error—located near the inner surface of the lining—remains below 4%, while displacement errors stay below 0.2 mm. Interface stress jumps are accurately captured and oscillations in zones with high stiffness contrast are effectively avoided. The method is presented as a fast and reliable analytical tool for tunnel design under complex multilayered rock conditions. Full article

Background: Trapeziometacarpal osteoarthritis (TMC OA) is a prevalent degenerative disorder that causes considerable pain and functional limitations, especially in older individuals, whose ideal treatment is still debated in the literature. Various treatments are described to restore a good functional outcome of the thumb; over the past 50 years, biological arthroplasties have been considered the gold standard for treating advanced stages of TMC OA. However, in the last decade, the use of dual mobility cup prostheses has significantly increased, with numerous studies reporting excellent clinical outcomes. In this case report, we show the results of a patient treated on the left hand with suspension arthroplasty and on his right hand with dual mobility arthroplasty in one-stage surgery. The aim of this case report is to directly compare outcomes between trapeziometacarpal prosthesis and suspension arthroplasty performed simultaneously in the same patient. Case Presentation: The present case reports a 71-year-old male patient with bilateral TMC osteoarthritis, referred to our clinic in May 2024. His medical history included hypertension, hypertriglyceridemia, paroxysmal atrial fibrillation, and benign prostatic hyperplasia. On examination, the right hand showed grade 3 osteoarthritis according to the Eaton–Littler classification, with the trapezium maintaining adequate bone stock, making the patient eligible for trapeziometacarpal prosthesis implantation. Conversely, the left hand demonstrated scaphotrapezoid arthritis with a slight reduction in trapezial bone stock, indicating the need for trapeziectomy followed by suspension arthroplasty. Both procedures were performed during the same surgical session by the same experienced hand surgeon using a lateral approach. On the right side, the trapeziometacarpal joint surfaces were resected and replaced with a dual mobility prosthesis, while on the left side, the trapezium was excised, and suspension arthroplasty was performed using a slip of the flexor carpi radialis (FCR) tendon. Methods: The patient underwent simultaneous treatment with a dual mobility trapeziometacarpal prosthesis on the right hand and trapeziectomy with suspension arthroplasty on the left hand. Clinical outcomes (grip and pinch strength, pain, QuickDASH, satisfaction, and range of motion) were evaluated at 1, 3, 6, and 12 months. Paired comparative statistics were applied with significance set at p < 0.05. Results: At all follow-up intervals (1, 3, 6, and 12 months), the hand treated with a trapeziometacarpal prosthesis demonstrated superior grip and pinch strength compared to the hand treated with trapeziectomy and suspension arthroplasty, with the greatest difference observed at 3 months. At 12 months, grip strength increased from 28 kg to 40 kg in the prosthesis-treated hand and from 25 kg to 33 kg in the suspension arthroplasty hand. Paired comparisons were performed at each follow-up interval up to 12 months, confirming a significant difference for grip strength. Pain levels (VAS, Visual Analogue Scale) decreased progressively in both hands, with a more rapid reduction in the hand treated with a trapeziometacarpal prosthesis, reaching statistical significance. QuickDASH scores indicated an earlier return to daily activities in the hand treated with the prosthesis, although this difference was not statistically significant. Patient satisfaction was consistently higher for the hand treated with a trapeziometacarpal prosthesis, with the patient reporting a ‘very satisfied’ rating at all timepoints. Range of motion recovery, assessed through the Kapandji score and measurements of thumb abduction and extension, also favored the hand treated with the prosthesis, with statistically significant differences for abduction and extension, whereas the hand treated with trapeziectomy and suspension arthroplasty demonstrated more gradual improvement over time. Conclusions: This case highlights the functional efficacy of both surgical approaches—biological arthroplasty and trapeziometacarpal prosthesis—in the treatment of TMC osteoarthritis. Both procedures resulted in a good clinical outcome and high patient satisfaction. However, recovery was noticeably faster in the hand treated with a trapeziometacarpal prosthesis, which is consistent with findings previously reported in the literature. These observations suggest that, while both techniques are valid and effective, trapeziometacarpal prosthetic replacement may offer a quicker return to function in appropriately selected patients. Full article

Gas storage in depleted gas reservoirs has become a core facility for ensuring energy security and a key means of guaranteeing a safe and stable supply of energy. Steep pressure rise and fall cyclic fluctuations caused by strong injection and production are likely to lead to the destabilization of the geological structure of the gas storage reservoir. Among the geological formations, fault activation is a serious threat to the safety of gas storage reservoirs. In this study, faults with different filling types were depicted by real downhole cores. Through a series of shear tests, the effects of normal stress, filling thickness and fault angles on the lithology of rocks on both sides were investigated. (1) A novel testing method was developed for finely engraving faults on downhole cores, allowing for the simulation of real reservoir conditions. (2) An increase in normal stress results in enhanced shear strength, which in turn elevates the critical initiation stress of the fault. (3) Shear strength decreases with an increasing amount of fault mud, indicating that the critical initiation stress in faults filled with minor amounts of fault mud is higher than that in faults filled with significant amounts of fault mud. (4) For equal amounts of fault mud, the shear strength of fault specimens at a 40° angle exceeds that of specimens at a 10° angle. This implies that a greater degree of fault undulation corresponds to a higher critical slip initiation stress, reducing the likelihood of fault slip and enhancing stability. (5) The shear strength of fault specimens composed of sandstone-mudstone combinations is lower than that of specimens containing sandstone-sandstone combinations, suggesting that the critical slip initiation stress for sandstone-mudstone combination faults is comparatively lower. Full article

This work presents a numerical study of side boundary effects in pore-scale digital rock flow simulations, where the side boundaries are often treated as no-slip walls. While the capillary end effects from inlet and outlet boundaries are well known, the influence of side boundaries has not been systematically studied, especially for two-phase flow. We employ a well-established three-dimensional color-gradient lattice Boltzmann model to simulate immiscible two-phase flow on both real and synthetic rock samples. Our results reveal significant artifacts in small samples caused by side boundaries, leading to non-representative saturation profiles, even though absolute permeability remains consistent with larger samples. In drainage, non-wetting phase saturation is substantially lower near the side boundaries due to increased trapping of the wetting phase, while in imbibition, the wetting phase preferentially flows along the walls, forming steep V-shaped saturation profiles near the side boundaries. Increasing sample size can reduce boundary influence, but this is often impractical for certain samples, owing to, for instance, high computational demands. Enforcing periodic boundary conditions directly on the side boundaries only marginally improves saturation near the boundaries for the drainage cases, as poor pore connectivity across quasi-periodic boundaries remains a limitation, especially in low-porosity media, while the approach causes unphysically high wetting phase saturation near the side boundaries during imbibition. An alternative approach is to generate synthetic rock samples that are inherently periodic in the transverse directions, enabling more representative two-phase flow simulations. By comparing simulations with no-slip and periodic boundary conditions on a low porosity synthetic rock sample, the side boundary effects can cause more than 10% differences in steady-state saturation. Thus, synthetically generated periodic digital rock samples offer a promising solution for pore-scale studies of low-porosity media. Full article

The lack of research on the slip behavior of the NW-trending faults in the central Tibetan Plateau constrains our understanding of the deformation models for this region. The Ba Co Fault, located in the central Tibetan Plateau, is a NW–SE-trending right-lateral strike-slip fault. Its eastern section has been active in the Holocene and plays an important accommodating role in the northward compression and east–west extension of the Tibetan Plateau. This study presents a detailed analysis of the geomorphic features of the eastern section of the Ba Co Fault in the Ngari Prefecture of Tibet, precisely measuring the newly discovered surface rupture zone on its eastern side and preliminarily discussing the activity of the fault based on the optically stimulated luminescence (OSL) dating results. The results reveal that the eastern segment of the Ba Co Fault displays geomorphic evidence of offset, including displaced Holocene alluvial–fluvial fans at the mountain front and partially offset ridges. A series of pressure ridges, trenches, counter-slope scarps, and shutter ridge ponds have developed along the fault trace. Some gullies exhibit a cumulative dextral displacement of approximately 16–52 m. The newly discovered co-seismic surface rupture zone extends for a total length of ~21 km, with a width ranging from 30 to 102 m. Pressure ridges within the rupture zone reach heights of 0.3–5.5 m, while trenches exhibit depths of 0.6–15 m. Optically stimulated luminescence (OSL) dating constrains the timing of the surface-rupturing earthquake to after 5.73 ± 0.17 ka. The eastern segment of the Ba Co Fault experienced a NW-trending compressional deformation regime during the Holocene, manifesting as a transpressional dextral strike-slip fault. Magnitude estimation indicates that this segment possesses the potential to generate earthquakes of M ≥ 6. The regional tectonic analysis indicates that the activity of the eastern section of the Ba Co Fault is related to the shear model of the conjugate strike-slip fault zone in the central Tibetan Plateau and may play a boundary role between different shear zones. Full article

Basalt fiber-reinforced polymer (BFRP) composites are increasingly utilized in photovoltaic mounting systems due to their excellent mechanical properties and durability. Bolted connections, valued for their simplicity, ease of installation, and effective load transfer, are widely employed for joining composite components. An orthogonal experimental design was adopted to investigate the effects of key parameters—including bolt end distance, number of bolts, bolt material, bolt diameter, preload, and connection length—on the load-bearing performance of three bolted BFRP plate configurations: lap joint (DJ), single lap joint (DP), and double lap joint (SP). Test results showed that the DJ connection exhibited the highest average tensile load capacity, exceeding those of the SP and DP connections by 45.3% and 50.2%, respectively. This superiority is attributed to the DJ specimen’s longer effective shear length and greater number of load-bearing bolts. Conversely, the SP connection demonstrated the largest average peak displacement, with increases of 29.7% and 52.9% compared to the DP and DJ connections. The double-sided constraint in the SP configuration promotes more uniform preload distribution and enhances shear deformation capacity. Orthogonal sensitivity analysis further revealed that the number of bolts and preload magnitude significantly influenced the ultimate tensile load capacity across all connection types. Finally, a calculation model for the tensile load capacity of bolted BFRP connections was established, incorporating a friction decay coefficient (α) and shear strength (τ). This model yields calculated errors under 15% and is applicable to shear slip-dominated failure modes, thereby providing a parametric basis for optimizing the tensile design of bolted BFRP joints. Full article