Search Results (5,530)

To meet the development needs of high-rise timber structures, current cross-laminated timber (CLT) shear walls typically feature a single-layer thickness of 35 mm with more than three laminations in the stack. However, such thickness easily leads to resource waste in small-scale residential buildings, while increasing transportation and hoisting costs, which is not conducive to the prefabrication and lightweight development of timber structures. To adapt to the development trend of China’s timber structure market towards public buildings such as cultural and tourism projects and small-scale residential buildings including new rural housing renovation, this study focuses on thin CLT shear walls with an overall thickness of 48 mm (16 mm per layer) and conducts research on their lateral load-bearing performance. Monotonic lateral static load tests and finite element (FE) simulations were carried out on thin CLT shear walls without openings, with different opening areas, and with the same opening area but different positions. A corresponding FE model was established and validated, with a focus on analyzing the influence of opening parameters on the shear performance of the walls. The research results show that wall openings significantly reduce the bearing capacity and shear stiffness of the walls: compared with the wall without openings, the ultimate load and shear stiffness of the walls with openings decrease by 20.4–28.6% and 36.3–42.3%, respectively. Among them, increasing the opening height has a more obvious weakening effect on the bearing capacity; for the same opening area, a wider opening results in a more significant decrease in stiffness. The FE model exhibits reliable accuracy, with the error between the experimental and simulation results in the elastic stage controlled within 10%, and the influence of the under-wall support on the shear stiffness is relatively small. Opening parameters have a prominent impact on the stiffness of the wall in the elastic stage, and the influence of the opening position is more critical—the smaller the distance from the opening to the top of the wall, the more obvious the decrease in overall stiffness. Full article

This paper proposes a novel mortise-and-tenon grouted masonry (MTGM) structure to enhance the mechanical performance and engineering applicability of masonry. The axial and eccentric compressive behavior of the system was systematically investigated through experimental testing and numerical simulation. A refined three-dimensional finite element model, developed in DIANA, effectively accounted for material nonlinearity and interfacial contact, with its high accuracy confirmed by experimental results. The parametric analysis of 52 numerical models elucidated the influence of block strength, core material type, wall thickness, steel fiber content, and geometric ratios on the compressive strength, deformation capacity, and failure modes. The results demonstrate that using steel fiber-reinforced concrete (SFRC) as the core filling material significantly enhances ductility and toughness; an SFRC content of 1.6% increased the ultimate strain by approximately 37%. Furthermore, increasing the eccentricity from 0.1 to 0.3 led to an average 40% reduction in load-bearing capacity. Theoretical analysis led to the derivation of calculation formulae relating to key axial compression parameters. Furthermore, a stress–strain constitutive relationship suitable for MTGM was established, featuring a parabolic ascending branch and a linear descending branch (R² = 0.992). For eccentric compression, a practical design method was developed based on the plane section assumption, which demonstrated superior predictive accuracy compared to existing code provisions. This study provides a reliable theoretical foundation and practical computational tools for the structural design and application of MTGM. Full article

Conventional deep cement mixing (DCM) columns commonly experience performance constraints and site-specific challenges arising from heterogeneous geological and loading conditions. This study investigates the vertical stress distribution, settlement behavior, and failure mechanisms of Variable-Section Deep Cement Mixing (VSDCM) columns through a series of finite element modeling. A comparative assessment is also conducted with two uniform-diameter columns of 0.5 m and 0.8 m. It is evident that the VSDCM columns possess 90% of the bearing capacity of the corresponding large-diameter columns. It exhibits a relative settlement 4–5 times smaller than that of the small-diameter column composite foundation, indicating a dominant role of enlarged head in stress redistribution and load sharing within the composite foundation. The stress arch exhibits a vertical influence range of approximately 0–0.4 m, within which load redistribution is significant. The VSDCM column encounter two stress peaks due to its variable cross-section, triggering failure at both, with the small-diameter section beneath the enlarged head being the most critical zone. The reduced material demands of the VSDCM column results in higher engineering economy, supporting its applicability as a sustainable and cost-effective ground improvement technique. Full article

To address the difficulty of controlling surrounding rock subjected to repeated repair-induced disturbances, the characteristics of the roadway surrounding rock and its deformation–failure mechanisms were examined. An experimental scheme for surrounding-rock control was formulated, and a three-dimensional numerical model was established. Four support schemes were evaluated to identify a rational support method and corresponding parameters: (a) rock bolts and cable bolts; (b) rock bolts, cable bolts, and floor cable bolts; (c) rock bolts, cable bolts, floor cable bolts, and U-shaped closed steel sets; and (d) rock bolts, cable bolts, floor cable bolts, U-shaped closed steel sets, and grouting. Comparative analyses were conducted in terms of plastic-zone evolution, stress-field distribution, surrounding-rock displacement, and the mechanical response of the support structures. The results indicate that, in roadways experiencing multiple repair disturbances and supported only by rock bolts and cable bolts, distinct stress-concentration zones develop within the supported surrounding rock, suggesting that reliance solely on bolts and cables is unfavorable for effective rock-mass control. Grouting improves the overall integrity and self-bearing capacity of the surrounding rock. Both the U-shaped closed support and the combined U-shaped closed support with grouting effectively restrain surrounding-rock deformation, and the corresponding stress distribution shows no pronounced stress-concentration zones. Based on the analyses of surrounding-rock displacement, support-structure loading, and incremental shear strain, the effectiveness of the support schemes in mitigating roof and floor displacement ranks, in descending order, as (d), (c), (b), and (a). Engineering practice further demonstrates that the combined support system consisting of 29U-type sets, grouted bolts, and bundle-type grouted cable bolts provides effective control over the deformation and failure of the roadway surrounding rock. Full article

Osteophytes (OPs) are a diagnostic hallmark of osteoarthritis (OA). However, the mechanisms underlying their initiation and their relationship with early subchondral bone changes remain poorly understood. Existing research primarily relies on animal models and late-stage OA tissue, leaving the initial morphological events leading to OP formation unclear. Background/Objectives: This study aimed to identify early changes in the subchondral bone as a key trigger for OP initiation in human OA through a comprehensive histological analysis of the subchondral area, including its peripheral regions. Methods: We conducted an extensive histological examination of full-section human tibial plateaus, including load-bearing and non-load-bearing compartments, obtained from patients with early and late stages of OA. Results: Our data demonstrate that subchondral bone changes, including osteoporosis, osteosclerosis, and microcracks, begin at the pre-chondropathic stage alongside microscopically intact cartilage. We identified a previously undescribed zone on the vertical wall of the tibial condyle (the VEPLS zone), characterized by reduced calcium content in the cortical plate and the persistence of embryonic cartilage, making it morphologically vulnerable. The first event in OP formation is microcracks in the cortical angle and the adjacent subchondral trabecula. These injuries initiate reparative osteogenesis, which, under continuous traumatic load (presumably shear forces due to joint instability), becomes insufficient, leading to cortical angle protrusion and OP formation. OP growth is accompanied by the deformation of the VEPLS zone cortical plate, causing vascular impairment and exacerbating bone weakness. Conclusions: Based on our findings, we propose the concept of tissue micro-instability. This concept posits that osteophytosis results from chronic microcracks and failed bone regeneration in vulnerable subchondral structures, induced by joint instability. We define an OP as a pathological outgrowth arising from this tissue micro-instability. Our study highlights the critical role of the peripheral subchondral area, particularly the VEPLS zone, in OA pathogenesis. Full article

This review offers a comprehensive analysis of the mechanical behavior and evolving design strategies of bridge bearings subjected to vertical seismic loading. Existing studies underscored that intense vertical ground motions—particularly those with high peak accelerations and rich frequency content—can provoke separation and subsequent impact between girders and bearings. Such interactions are especially harmful due to the inherently limited tensile resistance of conventional bearing systems. To evaluate vertical seismic performance, two core parameters are emphasized: tensile capacity and controlled energy dissipation. In recent years, the concept of tensile-resistant seismic design has garnered growing interest. By integrating high-strength steel cables, shape memory alloys (SMA), and advanced elastomeric materials, researchers have developed novel mechanisms that enhance the vertical resilience of bearings. This review synthesizes current understanding of near-fault seismic phenomena, recent advancements in bearing technology, and prospective research directions, thereby offering theoretical insight for optimal bearing selection and design, and contributing to the refinement of relevant engineering codes and standards. Full article

Background: Emergency rescuers frequently carry heavy equipment for extended periods, making musculoskeletal disorders a major occupational concern. Loading type and road slope play important roles in inducing physical fatigue; however, the assessment of physical fatigue under these conditions remains limited. Aim: This study aims to investigate physical fatigue under different loading types and road slope conditions using both electromyography (EMG) and eye movement metrics. In particular, this work focuses on eye movement metrics as a non-contact data source in comparison with EMG, which remains largely unexplored for physical fatigue assessment. Method: Prolonged load-bearing walking was simulated to replicate the physical demands experienced by emergency rescuers. Eighteen male participants completed experimental trials incorporating four loading types and three road slope conditions. Results: (1) Loading type and road slope significantly affected EMG activity, eye movement metrics, and perceptual responses. (2) Saccade time (ST), saccade speed (SS), and saccade amplitude (SA) exhibited significant differences in their rates of change across three stages defined by perceptual fatigue. ST, SS, and SA showed strong correlations with subjective fatigue throughout the entire load-bearing walking process, whereas pupil diameter demonstrated only a moderate correlation with subjective ratings. (3) Eye movement metrics were incorporated into multivariate quadratic regression models to quantify physical fatigue under different loading types and road slope conditions. Conclusions: These findings enhance the understanding of physical fatigue mechanisms by demonstrating the potential of eye movement metrics as non-invasive indicators for multidimensional fatigue monitoring in work environments involving varying loading types and road slopes. Full article

Geopolymer mortars were produced from construction and demolition waste using a binary binder of recycled brick powder/recycled concrete powder (RBP/RCP = 70/30 wt%), activated with a hybrid alkaline solution (NaOH/Na₂SiO₃/KOH) and reinforced with sisal fibres at 0–2 wt%. Mechanical performance (compression and three-point bending) and microstructure–phase evolution (XRD, FTIR, SEM-EDS) were assessed after low-temperature curing. Sisal addition delivered a strength–toughness trade-off with a reproducible optimum at ~1.0–1.5 wt%; at 2.0 wt%, fibre clustering and connected porosity reduced the effective load-bearing section, penalising flexure more than compression. Microstructural evidence indicates coexistence and co-crosslinking of N-A-S-H and C-(A)-S-H gels—enabled by Ca from RCP—leading to matrix densification and improved fibre–matrix anchorage. Fractographic features (tortuous crack paths, bridging, and extensive pull-out at ~1.5 wt%) are consistent with an extended post-peak response and higher fracture work without compromising early-age strength. This study achieves the following: (i) it identifies a practical reinforcement window for sisal in RBP/RCP geopolymers, (ii) it links gel chemistry and interfacial phenomena to macroscopic behaviour, and (iii) it distils processing guidelines (gradual addition, workability control, gentle deaeration, and constant A/S) that support reproducibility. These outcomes provide a replicable, low-embodied-CO₂ route to fibre-reinforced geopolymer mortars derived from CDW for non-structural and semi-structural applications where flexural performance and post-peak behaviour are critical. Full article

Traditional flexible polyurethane (PU) foams frequently exhibit limited mechanical support and suboptimal moisture–heat regulation, which can compromise the microenvironmental comfort required for high-quality sleep. In this study, natural luffa fibers (LF) were incorporated as a microstructural modifier to simultaneously enhance the mechanical and moisture–heat regulation performance of PU foams. PU/LF composite foams with varying LF loadings were prepared via in situ polymerization, and their foaming kinetics, cellular morphology evolution, and physicochemical characteristics were systematically investigated. The results indicate that LF functions both as a reinforcing skeleton and as a heterogeneous nucleation site, thereby promoting more uniform bubble formation and controlled open-cell development. At an optimal loading of 4 wt%, the composite foam developed a highly interconnected porous architecture, leading to a 7.9% increase in tensile strength and improvements of 19.4% and 22.6% in moisture absorption and moisture dissipation rates, respectively, effectively alleviating the heat–moisture accumulation typically observed in unmodified PU foams. Ergonomic pillow prototypes fabricated from the optimized composite further exhibited enhanced pressure-relief performance, as evidenced by reduced peak cervical pressure and improved uniformity of contact-area distribution in human–pillow pressure mapping, together with an increased SAG factor, indicating improved load-bearing adaptability under physiological sleep postures. Collectively, these findings elucidate the microstructural regulatory role of biomass-derived luffa fibers within porous polymer matrices and provide a robust material basis for developing high-performance, sustainable, and ergonomically optimized sleep products. Full article

As a cornerstone of China’s energy infrastructure, the coal mining industry relies heavily on the stability of its underground roadways, where the support of soft rock formations presents a critical and persistent technological challenge. This challenge arises primarily from the high content of expansive clay minerals and well-developed micro-fractures within soft rock, which collectively undermine the effectiveness of conventional support methods. To address the soft rock control problem in China’s Longdong Mining Area, an integrated material–structure control approach is developed and validated in this study. Based on the engineering context of the 3205 material gateway in Xin’an Coal Mine, the research employs a combined methodology of micro-mesoscopic characterization (SEM, XRD), theoretical analysis, and field testing. The results identify the intrinsic instability mechanism, which stems from micron-scale fractures (0.89–20.41 μm) and a high clay mineral content (kaolinite and illite totaling 58.1%) that promote water infiltration, swelling, and strength degradation. In response, a novel synergistic technology was developed, featuring a high-performance grouting material modified with redispersible latex powder and a tiered thick anchoring system. This technology achieves microscale fracture sealing and self-stress cementation while constructing a continuous macroscopic load-bearing structure. Field verification confirms its superior performance: roof subsidence and rib convergence in the test section were reduced to approximately 10 mm and 52 mm, respectively, with grouting effectively sealing fractures to depths of 1.71–3.92 m, as validated by multi-parameter monitoring. By integrating microscale material modification with macroscale structural optimization, this study provides a systematic and replicable solution for enhancing the stability of soft rock roadways under demanding geo-environmental conditions. Soft rock roadways, due to their characteristics of being rich in expansive clay minerals and having well-developed microfractures, make traditional support difficult to ensure roadway stability, so there is an urgent need to develop new active control technologies. This paper takes the 3205 Material Drift in Xin’an Coal Mine as the engineering background and adopts an integrated method combining micro-mesoscopic experiments, theoretical analysis, and field tests. The soft rock instability mechanism is revealed through micro-mesoscopic experiments; a high-performance grouting material added with redispersible latex powder is developed, and a “material–structure” synergistic tiered thick anchoring reinforced load-bearing technology is proposed; the technical effectiveness is verified through roadway surface displacement monitoring, anchor cable axial force monitoring, and borehole televiewer. The study found that micron-scale fractures of 0.89–20.41 μm develop inside the soft rock, and the total content of kaolinite and illite reaches 58.1%, which is the intrinsic root cause of macroscopic instability. In the test area of the new support scheme, the roof subsidence is about 10 mm and the rib convergence is about 52 mm, which are significantly reduced compared with traditional support; grouting effectively seals rock mass fractures in the range of 1.71–3.92 m. This synergistic control technology achieves systematic control from micro-mesoscopic improvement to macroscopic stability by actively modifying the surrounding rock and optimizing the support structure, significantly improving the stability of soft rock roadways. Full article

Background: To compare the biomechanical strength of three fixation techniques for the elbow anterior capsule and coronoid process using a synthetic ulna model. We hypothesize that a cortical suture button would be equivalent to the bone tunnel model but inferior to a screw-post construct. Methods: A biomechanical study was conducted using a composite ulna bone model to simulate coronoid process fixation with three techniques: traditional trans-osseous bone tunnel repair, suspensory fixation using a cortical button, and a screw-post construct using a 3.5 mm cortical screw. All constructs were assembled using high-strength suture. Each specimen underwent axial loading on an Instron machine until failure, defined as loss of fixation through the dorsal cortex. Peak ultimate strength was recorded. Statistical analysis was performed using one-way ANOVA and Tukey’s HSD test. Results: The suture button construct demonstrated the highest mean ultimate strength at 490.3 ± 125.2 N, significantly greater than both the bone tunnel (328.8 ± 86.4 N, p < 0.01) and screw-post constructs (273.4 ± 54.5 N, p < 0.001). While the bone tunnel construct exhibited a 20.3% higher strength than the screw-post construct, this difference was not statistically significant (p = 0.13). The screw-post construct showed the least variability in strength to failure but the lowest overall strength. The suture button demonstrated the greatest mechanical strength but also the most variability. Conclusions: Suspensory fixation using a titanium cortical suture button provides significantly greater mechanical strength compared to traditional bone tunnel and screw-post techniques in a synthetic ulna model. While variability was greatest with the suture button construct, its superior load-bearing capacity suggests potential advantages in stabilizing the elbow through anterior capsule and coronoid fracture repair. These findings support further clinical investigation of suture button fixation as a viable technique in complex elbow injuries. Full article

To clarify the influence of gouge-induced altered layers on fracture initiation and load-bearing capacity of pipelines, X70 pipeline steel is taken as the research object. The geometry and partition of the altered layer are first determined by means of a micro-Vickers hardness array and a threshold criterion, and its mechanical parameters are then obtained from small-scale tensile tests. The altered layer is subsequently embedded into a finite element model of a gouged pipe as an independent material domain, and the Gurson–Tvergaard–Needleman (GTN) damage model is employed to simulate damage evolution and crack propagation under pure internal pressure and combined internal pressure and tensile loading. The results indicate that, compared with the base metal, the yield strength and ultimate tensile strength of the altered layer increase by about 39% and 47%, respectively, while the elongation to failure decreases from 16% to 1.8%, exhibiting a typical “high-strength–low-ductility” behavior. When the altered layer is considered, the fracture initiation location under pure internal pressure shifts from the base metal to the altered layer, and the burst pressure decreases from 19 MPa to 16.5 MPa. Under the combined internal pressure and tensile loading, the peak load changes little, whereas the ultimate displacement is reduced by about 26.5%, leading to a marked loss of pipeline ductility. These findings demonstrate that the gouge-induced altered layer has a significant effect on the fracture initiation pressure, failure mode, and load-bearing characteristics of gouged pipes. Modeling it as an independent material domain in finite element analysis can more realistically capture the failure behavior and safety margin of gouged pipelines, thereby providing a more reliable theoretical basis for improving integrity assessment criteria for externally damaged pipelines. Full article

This study determined the elastic properties of “green” concrete with cement partially replaced by oil shale ash (OSA) and reinforced with short basalt integral fibers (BIFs). Commercially available Deutsche Basalt Faser (DBF) GmbH Turbobuild Integral basalt fibers were used. There is currently a high demand both for strengthening concrete and applying ecological approaches with respect to circular economy. Oil shale ash is the byproduct of oil shale combustion. Basalt fiber is produced by melting basalt rock. Both BIF and OSA are used as additives in concrete. Cement replacement by OSA non-linearly changes the concrete’s strength properties, and the addition of BIF improves them. An experimental investigation was conducted using four-point bending tests and cube sample compression tests. Theoretical methods such as Voigt and Reuss boundaries, the Halpin–Tsai method, and the Mori–Tanaka method were used to predict the elastic properties of the fabricated samples. The theoretical models can provide useful information, although they may not fully capture the real properties observed experimentally. The results show that BIFs protect against instant brittle destruction. The experiments demonstrated an optimal OSA concentration for a fixed amount of BIF, resulting in the highest load-bearing capacity of the concrete. The addition of either 15% OSA only or 20% OSA and CBF can increase the stiffness of the concrete. This article provides guidance to the construction sector on using OSA and CBF together. Full article

Longan (Dimocarpus longan Lour.) exhibits vigorous vegetative growth and strong fruit setting ability but suffers from alternate bearing. The role of endogenous hormones in mediating the effects of fruiting load remains unclear. This study investigated how the initial fruiting branch rate (IFBR) and initial fruit number per cluster (INFC) regulate endogenous hormones in the aril and leaflets of mature ‘Shixia’ longan. Key findings reveal the aril as the hormonal sink, accumulating auxin (IAA) and abscisic acid (ABA), while leaves retain IAA precursors (TRP) and conjugates. Higher IFBR and INFC increased the demand for IAA in the aril to support expansion but simultaneously elevated ABA levels in leaves. Notably, IFBR exerted a stronger influence than INFC. These hormonal changes were significantly correlated with the fruit shedding rate and soluble solid content. Overall, the endogenous hormone profile was optimized by maintaining a moderate IFBR of approximately 60% and an INFC within the range of 60 to 80, achieving balance between fruit expansion, leaf vitality, and yield. The results provide a hormonal basis for precise crop load management in longan cultivation. Full article

Modern power transmission systems are required to meet increasingly stringent demands, including a wide range of transmission ratios, compact dimensions, high precision, energy efficiency, reliability, and thermal stability under dynamic operating conditions. Among the solutions that satisfy these requirements, cycloidal reducers are particularly prominent, with their application continuously expanding in industrial robotics, computer numerical control (CNC) machines, and military and transportation systems, as well as in the satellite industry. However, as with all mechanical power transmissions, friction in the contact zones of load-carrying elements in cycloidal reducers leads to power losses and an increase in operating temperature, which in turn results in a range of adverse effects. These undesirable phenomena strongly depend on lubrication conditions, namely on the type and properties of the applied lubricant. Although manufacturers’ catalogs provide general recommendations for lubricant selection, they do not address the fundamental tribological mechanisms in the most heavily loaded contact pairs. At the same time, the available scientific literature reveals a significant lack of systematic and experimentally validated studies examining the influence of lubricant type on the energetic and thermal performance of cycloidal reducers. To address this identified research gap, this study presents an analytical and experimental investigation of the effects of different lubricant types—primarily greases and mineral oils—on the thermal stability and efficiency of cycloidal reducers. The results demonstrate that grease lubrication provides lower total power losses and a more stable thermal operating regime compared to oil lubrication, while oil film thickness analyses indicate that the most unfavorable lubrication conditions occur in the contact between the eccentric bearing rollers and the outer raceway. These findings provide valuable guidelines for engineers involved in cycloidal reducer design and lubricant selection under specific operating conditions, as well as deeper insight into the lubricant behavior mechanisms within critical contact zones. Full article