Search Results (320)

The horizontal bearing mechanism of pile–soil composite foundations adjacent to retaining walls is significantly affected by asymmetric lateral constraints caused by retaining wall movement, a scenario that remains inadequately explored in conventional design. This study employs a validated three-dimensional finite element model to investigate the response of such foundations to rotational displacement of a nearby wall. A comprehensive parametric analysis quantifies the influence of pile configuration, cushion properties, soil modulus, and loading conditions. The results demonstrate that rotational displacement (RB mode) induces a highly non-uniform load distribution within the pile group. The middle-front row piles emerge as critical load-bearing components, experiencing significant load amplification (load-transfer coefficients η_p up to 2.3). Key parameters, including pile length and cushion stiffness, selectively regulate system stiffness or optimize load sharing. Increasing the pile–wall distance is identified as an effective measure to reduce load concentration on front-row piles. The findings provide quantitative insights and practical guidance for the performance-based design of composite foundations under asymmetric constraints. Full article

High-performance fiber-reinforced cementitious composite (HPFRCC) has shown considerable potential as a strengthening material for improving the crack resistance, integrity, and deformation capacity of masonry structures. In aging concrete hollow block masonry walls subjected to long-term eccentric compression, material degradation may lead to premature cracking, local crushing, stiffness deterioration, and reduced safety margins, thereby adversely affecting structural reliability and service performance. However, studies on the eccentric compression behavior of HPFRCC-strengthened concrete hollow block masonry walls with simulated material degradation remain limited. In this study, experimental, finite element, and theoretical analyses were conducted on three HPFRCC-strengthened specimens with an eccentricity ratio of 0.5y, namely a 30 mm double-sided strengthened specimen, a 45 mm double-sided strengthened specimen, and a 30 mm single-sided strengthened specimen. The failure modes, load–displacement responses, lateral deformation, strain development, and DIC strain distribution characteristics were investigated. The results showed that, under the test conditions considered in this study, the double-sided strengthened specimens exhibited higher load-bearing capacity, greater stiffness, and better structural integrity than the single-sided strengthened specimen. Among them, the 45 mm double-sided strengthened specimen reached the highest peak load of 1643 kN, whereas the 30 mm double-sided strengthened specimen exhibited a gentler post-peak response, more dispersed crack development, and better deformation compatibility. The finite element results were generally consistent with the experimental results; the ratios of the experimental to numerical peak loads ranged from 0.96 to 1.01, while the corresponding peak displacement ratios ranged from 1.02 to 1.09. Within the parameter range considered in the numerical analysis, increasing the strengthening thickness was generally beneficial to the eccentric compression capacity. The proposed preliminary sectional bearing capacity model showed acceptable agreement with the test results for the specimens considered in this study; however, its broader applicability requires further validation using additional specimens. Full article

Background and Objectives: Adolescent idiopathic scoliosis (AIS) may influence pelvic orientation and lower-limb alignment; however, data on coronal lower-limb alignment after completion of spinal treatment remain limited. This study aimed to evaluate lower-limb radiographic alignment in AIS patients after spinal treatment and to determine whether these parameters differ according to main curve location. Materials and Methods: In this retrospective study, 70 AIS patients treated surgically (n = 52) or with brace therapy (n = 18) between 2010 and 2020 were analyzed. Patients were grouped according to main curve location as thoracic (n = 28), lumbar (n = 21), or thoracolumbar (n = 21). Pre-treatment standing full-spine radiographs were used to assess Cobb angle, coronal balance, and pelvic coronal obliquity angle (PCOA). After completion of spinal treatment, full-length weight-bearing lower-limb radiographs were evaluated for femoral and tibial lengths, mechanical axis deviation (MAD), femoral neck–shaft angle (NSA), anatomical lateral distal femoral angle (aLDFA), and mechanical lateral distal femoral angle (mLDFA). Additional treatment-stratified, treatment-adjusted, and threshold-based analyses were performed. Results: PCOA, coronal balance, bilateral MAD, right aLDFA, and right mLDFA differed significantly among the three curve-location groups. The lumbar group demonstrated more negative MAD values than the thoracic group, indicating a tendency toward valgus alignment (right MAD: −5.88 ± 8.8 mm vs. 3.65 ± 7.9 mm, p = 0.004; left MAD: −3.5 ± 7.5 mm vs. 3.75 ± 7.0 mm, p = 0.005). After adjustment for treatment modality, age, and main Cobb angle, curve location remained significantly associated with right MAD, left MAD, right aLDFA, and right mLDFA. However, the proportion of patients with clinically relevant malalignment, defined as MAD exceeding ±10 mm in at least one limb, did not differ significantly among the groups. Conclusions: AIS patients show subtle but measurable differences in coronal lower-limb alignment after completion of spinal treatment. Lumbar and thoracolumbar curves are associated with greater pelvic obliquity and a tendency toward more valgus mechanical-axis alignment, whereas limb lengths and NSA remain comparable among curve-location groups. These findings appear to represent mainly radiographic or biomechanical variations rather than overt clinically relevant deformity in most patients. Full article

Aluminum alloy has been increasingly widely used in the construction field due to its green advantages of light weight, easy processability, high corrosion resistance, and recyclability, which conforms to the concept of green energy conservation and sustainable development in modern architecture. To improve its performance, carbon fiber-reinforced polymer (CFRP) was used to reinforce aluminum alloy pipes. A total of 22 groups of specimens with different lengths, thicknesses, and CFRP configurations were constructed to study their mechanical properties under axial compression. The experimental results show that CFRP reinforcement can effectively inhibit the lateral deformation and delay the global buckling of aluminum alloy pipes, among which the three-segment and full-coverage reinforcement have significant effects; the combination of aluminum and CFRP can transform direct failure into progressive failure and improve bearing capacity. This composite material not only has an excellent high strength-to-weight ratio and durability, but also can reduce structural self-weight. Full article

The effects of Ti/Nb microalloying-induced MC-type carbide precipitation and tempered microstructure evolution on the dry-sliding wear behavior of low-carbon martensitic wear-resistant steels were systematically investigated. Three experimental steels with different microalloying strategies (0.04Ti, 0.1Ti, and 0.04Ti/Nb) were subjected to quenching and subsequent tempering. Microstructural features, carbide characteristics, and mechanical properties were characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing, and impact testing, while wear performance was evaluated by pin-on-disk tests under dry-sliding conditions. The results indicate that wear resistance is governed by the combined effects of tempered martensite stability and MC-type carbide precipitation. Low-temperature tempering effectively reduces the wear mass loss of Ti-containing steels by enhancing their resistance to abrasive shear deformation while maintaining sufficient toughness. In contrast, the Nb-containing steel exhibits a stage-dependent wear response associated with the formation and destabilization of oxide-derived third-body debris during sliding. (Nb,Ti)C precipitates act as microscale load-bearing units, contributing to strength enhancement and subsurface damage suppression, but their influence on wear behavior strongly depends on tempering temperature. The dominant wear mechanism is abrasive micro-cutting, accompanied by fatigue-induced spalling and oxidation-assisted damage at later stages. These results demonstrate that wear performance cannot be correlated with hardness alone, but instead requires the coordinated optimization of carbide precipitation and tempered microstructural stability. This work provides microstructural guidance for the design of microalloyed martensitic wear-resistant steels. Full article

This study comprised an experimental investigation of the in-plane performance of composite floor slabs under out-of-plane effects. Two composite floor slabs were subjected to pure in-plane loading, and in-plane and out-of-plane coupled loading, respectively. The study analyzed crack patterns, failure modes, and load–displacement curves, and evaluated how out-of-plane effects influenced in-plane performance. The test results indicated that both specimens exhibited a typical shear-tension failure mode, forming diagonal shear cracks. The specimen with out-of-plane loading exhibited a trend for lateral development of the shear cracks. The load–displacement curves of the two specimens showed obvious strength degradation, stiffness degradation, and a pinching effect. By comparing the two specimens, it could be observed that at a small out-of-plane displacement angle, the in-plane ultimate bearing capacity of a specimen was not significantly weakened; however, as the out-of-plane displacement continued to increase, the in-plane bearing capacity of the specimen decayed more rapidly. Full article

Indisputably, the evolution of innovative manufacturing methods such as additive manufacturing (AM) or 3D printing in the last decade has started gradually to influence the construction field, offering significant benefit potential, particularly in the field of metallic materials. In the case of aluminium alloys, the implementation of the wire arc additive manufacturing (WAAM) method, an AM sub-type, has recently emerged as a promising alternative to conventional rolling and extrusion, enabling unprecedented geometric flexibility, lower energy demand, and reduced tooling costs. However, the selection of an appropriate feedstock alloy poses a major challenge, as inherent trade-offs between strength, ductility, and printing-induced anisotropy arise. In this context, this study presents a thorough multi-scale numerical investigation, spanning from the cross-sectional to the global structural scale. The structural performance of several two-story moment-resisting frames was evaluated, comparing frames featuring WAAM-fabricated columns against conventional extruded and rolled benchmarks. The assessment included three 3D-printed alloys (Al-Mg, Al-Cu, Al-Mg-Si), differing in ductility levels, featuring topology-optimized and internal lattice-reinforced cross-sectional geometries. Linear elastic analyses reveal that global lateral stiffness heavily governs the response of slender frames, where WAAM was able to efficiently decrease the corresponding inter-story drifts by maximizing cross-sectional inertia without necessitating the utilization of larger external member dimensions. Furthermore, nonlinear static (pushover) analyses provided valuable insight into critical design considerations, exposing a profound strength-ductility trade-off in printed aluminium alloy load-bearing members. Full article

Background/Objectives: The preliminary experience with new dual-mobility system for small Japanese patients was introduced in this paper. Methods: Twenty-nine hips which underwent primary THA were retrospectively reviewed. All cups were inserted via Hardinge lateral approach. The ability to perform formal Japanese sitting in a kneeling position (Seiza in Japanese) and bowing while sitting (Zarei in Japanese) was evaluated. The mean follow-up was 6 months. Results: The mean age at surgery was 70 years, mean height was 156 cm, mean weight was 58 kg, and mean body mass index was 23.6. The acetabular cups utilized were a hemispherical hydroxy-apatite coated cup (25 hips) and a hemispherical trabecular titanium cup (4 hips), with diameters of 46 mm in 5, 48 mm in 15, 50 mm in 3, 52 mm in 1, 54 mm in 3, 56 mm in 1, and 62 mm in 1; mean diameter was 49.4 mm. No postoperative dislocations including intraprosthetic dislocation or metal allergy were observed. The mean Harris hip score improved significantly from 39 points preoperatively to 89 points postoperatively (p < 0.05). Radiographic evaluation demonstrated bone ingrowth stability in all cases according to Engh’s criteria and no aseptic loosening of the implants. Mean hip flexion increased from 75° preoperatively to 90° postoperatively (p < 0.05). The ability to perform Seiza increased from 8 patients preoperatively to 23 patients postoperatively (p < 0.05). The ability to perform Zarei (deep bowing) increased from 7 patients preoperatively to 20 patients postoperatively (p < 0.05). Conclusions: This novel dual-mobility system designed for smaller Japanese patients offers three distinct advantages: (1) availability of 42, 44, 46 and 48–66 mm outer diameter cups, (2) 1 mm deeper center of rotation, providing increased jumping distance compared to other designs, and (3) improved assembly instrumentation (cement-gun-type bearing press). Early clinical results suggest that this newly developed dual-mobility THA system is well-suited to the lifestyle and anatomical characteristics of Japanese patients. Full article

The effect of treatment time on arc-enhanced glow discharge plasma-assisted nitriding (AEGD-PAN) of AISI M2 high-speed steel was investigated for non-heat-treated and heat-treated substrates. Nitriding treatments were carried out at 350 °C for 1.5 and 3.5 h, producing diffusion layers with thicknesses ranging from approximately 38 to 75 µm without formation of a continuous brittle compound layer. X-ray diffraction combined with Rietveld refinement revealed the progressive formation of γ′-Fe₄N and ε-Fe₂₃N nitrides together with lattice expansion of the α-Fe matrix, indicating nitrogen supersaturation and precipitation strengthening within the diffusion zone. Heat-treated specimens exhibited higher surface hardness, reaching ~1350 HV_0.1, while non-heat-treated substrates developed pronounced hardness gradients associated with diffusion-controlled layer growth. Scratch testing showed improved resistance to contact-induced damage with increasing nitriding time, particularly for the 3.5 h treatment, where lateral cracking was significantly reduced and load-bearing capacity increased. Multi-pass scratch wear tests revealed a reduction in the Archard wear coefficient by up to four orders of magnitude compared with untreated M2 steel. These results demonstrate that AEGD-PAN at moderate temperature enables efficient diffusion layer formation and significant improvement in the tribological performance of high-alloy tool steels. Full article

Coal gangue is one of the most abundant solid wastes generated during coal mining. The use of coal gangue for underground backfilling is widely recognized as an effective approach to reducing waste accumulation and promoting sustainable utilization. To further investigate the bearing and deformation behavior of underground gangue filling materials, combined with the underground occurrence conditions of crushed gangue in goaf, a self-designed loading apparatus for crushed gangue was employed to perform lateral compression experiments on crushed gangue. The compaction deformation, fractal dimension, and acoustic emission evolution characteristics of crushed gangue under the influence of lithology, water content state, particle size distribution, and axial pressure were analyzed. The results indicate that higher rock strength, lower moisture content, smaller particle size range, and lower axial pressure significantly enhance the bearing capacity and reduce axial strain. The fractal dimension increases with decreasing rock strength, increasing moisture content, and increasing axial pressure, reflecting intensified particle fragmentation. The acoustic emission response exhibits three different stages, corresponding to void compaction, void filling, and structural adjustment. Axial pressure has been identified as the main factor controlling acoustic emission energy release, while water content significantly suppresses acoustic emission energy and event frequency. The key roles of particle sliding, rotation, and torque-driven rearrangement in controlling overall deformation were elucidated. These findings provide theoretical support for the mechanical behavior of gangue filling in the goaf and the sustainable disposal and resource utilization of mining waste. Full article

To reveal the progressive collapse mechanism of reinforced concrete spatial beam–slab structures with unequal spans and improve their collapse-resistant design level, this study investigates the progressive collapse resistance of reinforced concrete spatial beam–slab structures with unequal span arrangements. A finite element model of the spatial frame structure was developed in ABAQUS under inner column failure conditions, and pushdown analysis was employed for numerical simulation of the test samples. The effects of the inner column failure position, beam–slab parameters, floor slab damage performance, and beam-end internal forces on the collapse capacity of reinforced concrete spatial beam–slab structures were analyzed. The results indicate that, under inner column failure, the floor slab contributes 40–50% of the structure’s bearing capacity; under side column failure, it contributes 20–30%; and under corner column failure, it contributes 15–25%. A larger beam span reduces the structure’s bearing capacity after column failure. Additionally, equal-span designs exhibit a “lag” in force compared with unequal-span designs, and lateral constraints of the floor slab have minimal influence on the bearing capacity of slabless structures. The beam and slab design parameters significantly affect the bearing capacity and ductility of a structure. The damage performance of the floor slab under small deformations reflects its yield mode, enabling inference of the crack distribution. These findings provide scientific insight into the progressive collapse mechanism of unequal-span reinforced concrete spatial beam–slab structures. On the practical side for engineering design, a bearing capacity formula incorporating the influence of the floor slab in unequal span arrangements is proposed. The innovation of this paper lies in systematically analyzing the differences in progressive collapse between equal-span and unequal-span structures, as well as the influence of the floor slab on the progressive collapse of unequal-span structures, thereby providing a theoretical basis for research on the progressive collapse of unequal-span structures such as the Xuankou Middle School in Wenchuan. Full article

The new crossed cable-truss spoke structure (CCTSS) significantly improves the lateral stiffness and integral stability of the ordinary spoke cable-truss structure, but it still has the shortcomings of general tensile structures, like low redundancy and weak collapse resistance. Its collapse resistance is still unclear. In the paper, the structural characteristics of CCTSS are introduced. Secondly, the influence of initial prestresses on the collapse performance of CCTSS is studied. Then the collapse response features and collapse mechanism of the members and joints of CCTSS are revealed under the actions of no loads, full-span loads and half-span loads. Finally, a calculation method of the dynamic force amplification coefficient is proposed based on the collapse results of CCTSS, and a calculation method of the importance of members and joints is further proposed based on the dynamic internal force amplification coefficient, which indirectly evaluates structural collapse resistance. The results show that CCTSS has good local collapse resistance, but the failure of ring cables and joints at the ring cables will cause the structure to lose its integral bearing capacity. Meanwhile, the proposed calculation method of the importance of components and joints has a simple calculation process and is convenient to utilize, which has good engineering application value. The research content provides a theoretical basis and analysis method for structural safety design. Full article

A rock-socketed pile model load test was conducted for the renovation project of the dangerous old bridge at Shaoping Bridge. The experiment focused on the core parameter of the roughness factor (RF) of the pile body, revealing its influence on the bearing characteristics. The study delved into the load–displacement relationship, ultimate bearing capacity evolution, axial force transmission mechanism, average lateral resistance performance characteristics, and pile–soil relative displacement law of test piles in complex rock formations under different RF values. The research results indicated the following: The test pile exhibited typical brittle failure. At the moment of failure, the load at the pile head dropped abruptly, resulting in a steep drop in its load–displacement curve. Under ultimate load conditions, the average attenuation amplitudes of axial force in the four test piles decreased progressively in Rock Layer I, II, and III, measuring 26.96%, 14.86%, and 10.84%, respectively. The average side resistance distribution along the pile shaft showed a single-peak pattern, peaking in Rock Layer I. Increasing RF effectively enhanced the bearing capacity of test piles. However, a higher RF value does not necessarily yield better results, as it exhibits an inverted U-shaped relationship with bearing capacity. Under the specific conditions of this study, the highest bearing capacity among the tested RF values was observed at RF = 0.168; beyond this threshold, performance actually declined. The pile-top load was primarily shared by side resistance and end bearing resistance. Both components initially increased and then decreased with increasing RF, where the end bearing resistance accounted for 43.64~49.47% of the upper load. Full article

The load characteristics of the helicopter tail rotor system are critical to flight safety and handling performance, and flight testing remains the most direct and reliable means to obtain authentic load data. In this paper, the well-established Wheatstone bridge strain measurement method is adopted to carry out accurate load testing on the helicopter tail rotor system. The tail rotor assembly mainly consists of the tail rotor shaft, pitch link, and tail rotor blades, which undertake different load transfer tasks during flight. Under actual operating conditions, the tail rotor shaft bears significant axial tension as well as combined lateral and vertical bending moments; the pitch link is primarily subjected to alternating axial tension and compression; and the tail rotor blades withstand complex loads including flapping bending, lagwise bending, and torsional moments. According to the distinct stress characteristics and force transmission paths of each component, targeted flight test maneuvers are reasonably designed. These maneuvers include steady-level flight at low, medium, and high speeds, zigzag climbing flight, near-ground side-rear flight, as well as deceleration-to-sprint and obstacle slope maneuvers specified in ADS-33E. Key flight parameters are selected for in-depth analysis to reveal the load distribution and dynamic variation patterns of the tail rotor under typical operating conditions. On this basis, a helicopter load risk test point matrix is established to identify high-risk working conditions and key monitoring positions. This study provides a solid theoretical and data foundation for subsequent flight test monitoring and structural strength verification. It effectively reduces flight test risks, improves monitoring efficiency and accuracy, and helps cut down the human, material, and financial costs associated with flight test monitoring. The research results can also provide important references for the design optimization and safety evaluation of helicopter tail rotor systems. Full article

Purpose: Prostate-specific membrane antigen (PSMA) is a well-established molecular target in prostate cancer (PCa). Both radionuclide imaging and near-infrared fluorescence (NIRF) imaging offer high sensitivity for in vivo tumor detection. PSMA-targeted dual-modality probes integrating these two imaging techniques provide complementary preoperative and intraoperative tumor visualization, thereby improving surgical guidance in PCa. In this study, we aimed to develop a novel dual-labeled PSMA probe combining radioactive and fluorescent properties to achieve precise tumor delineation during radical prostatectomy (RP). Methods: A high-affinity PSMA-targeted fluorescent probe (PSMA-DF) was synthesized using solid-phase synthesis. Subsequent radiolabeling with the radionuclide [⁶⁸Ga]Ga yielded the successful generation of a dual-modal PSMA-targeted molecular probe, namely [⁶⁸Ga]Ga-PSMA-DF. The probe was systematically evaluated both in vitro and in vivo, and its safety profile was assessed through acute toxicity testing. Tumor-bearing nude mouse models were established using PSMA-positive 22Rv1 and PSMA-negative PC-3 PCa cell lines. Imaging performance, tumor-targeting specificity, and biodistribution of the probe were comprehensively evaluated using micro-PET imaging, in vivo fluorescence imaging, and biodistribution studies. Results: High-quality and high-purity PSMA-DF was successfully prepared, which exhibited excellent optical properties. Following radiolabeling with [⁶⁸Ga]Ga, a dual-modality radionuclide-fluorescence probe ([⁶⁸Ga]Ga-PSMA-DF) was successfully constructed. In vitro cellular uptake studies demonstrated that 22Rv1 cells had relatively high uptake of the probe, reaching 7.34 ± 0.55 IA%/10⁶ cells at 120 min. In contrast, PC-3 cells and blocked 22Rv1 cells displayed minimal uptake, confirming the specific targeting ability of the probe. In vivo evaluations were conducted on tumor-bearing mice using micro-PET/CT and NIRF imaging. The results revealed that [⁶⁸Ga]Ga-PSMA-DF achieved high specific tumor accumulation in 22Rv1 xenografts, with the peak tumor uptake (SUVmax = 1.748 ± 0.132) and tumor-to-muscle ratio (11.542 ± 1.511) observed at 120 min. Notably, high-contrast fluorescence imaging was also achieved at later time points, yielding a tumor-to-background ratio (TBR) of 6.559 ± 1.415 at 48 h. Notably, ex vivo biodistribution data were consistent with in vivo imaging findings. Conclusions: This preclinical study demonstrates that [⁶⁸Ga]Ga-PSMA-DF exhibits high and specific uptake in PCa models, supporting its potential as a dual-modality tracer for both PET/CT imaging and real-time intraoperative fluorescence guidance during PCa surgery. Full article