Search Results (1,997)

Amidst the green transition of the energy structure, as a sustainable innovation, photovoltaic pavement technology has garnered significant attention for its ability to utilize road surfaces for clean energy generation. However, roadway infrastructure must meet both load-bearing and safety requirements, making the structural performance analysis of photovoltaic pavements particularly crucial. This study focuses on load-bearing photovoltaic highways and employs finite element simulation to systematically analyze the effects of different surface transparent layer thicknesses and base sidewall thicknesses on the dynamic mechanical response of the photovoltaic pavement structure. The results indicate that increasing the surface transparent layer thicknesses significantly reduces structural deformation, stress, and strain, thereby enhancing overall stiffness and stability. Similarly, increasing the base sidewall thicknesses within a certain range also markedly improves structural performance, although the benefits tend to plateau beyond a specific thickness. Optimizing the structure can significantly enhance the load-bearing capacity and durability of photovoltaic pavements, thereby facilitating the achievement of green transportation and sustainable energy goals, and making a significant contribution to sustainable development. Full article

This study focuses on the problem of local instability of sandwich panels, which consist of two thin but relatively stiff facings and a thick but shear-deformable core. Such structures are commonly used in civil engineering and in the aerospace, aviation, and automotive industries. A case is presented in which one of the facings is deep-profiled. Due to typical mechanical or thermal interactions, this facing is subjected to compression. The thick core of the sandwich panel plays a stabilizing role. However, at a specific critical load, local stability is lost, representing a typical form of damage that occurs in sandwich panels. In the case of a deep-profiled facing, the geometry of the facing must also be taken into account, specifically the fact that the bends resulting from profiling constitute a significant limitation to its deformation. In this study, expressions are derived that enable the determination of the critical (wrinkling) stress, taking into account the geometry of the compressed facing bands and various boundary conditions defined along their edges. The energy approach is used to solve the problem. The presented solution to the problem of local instability is illustrated using examples. The obtained results indicate that the use of narrow bands is particularly effective while also allowing for determination of the maximum benefits resulting from deep profiling of the facings. This information is essential when considering changes to the geometry of industrially produced sandwich panels or when optimizing the load-bearing capacity of individual sandwich elements. Full article

Ductility, as a fundamental mechanical property, allows structures to undergo inelastic deformations and dissipate seismic energy while maintaining their load-carrying capacity without substantial strength degradation. Thus, the estimation of structural ductility demand has consistently constituted an essential topic of research interest in earthquake engineering. In this study, an iterative procedure for estimating the ductility demand of elastoplastic single-degree-of-freedom (SDOF) systems through dissipated energy is introduced. The proposed procedure helps the determination of ductility demand by use of only elastic response spectra. It initially estimates the hysteretic energy as a proportion of the total input energy. Then, ductility demand is estimated with the help of a developed equation by performing regression analyses based on the nonlinear time history analyses results of elastoplastic single-degree-of-freedom (SDOF) systems with a certain strength. Time history analyses were carried out by using an extensive earthquake ground motion database, which includes a total of 268 far-field records, two horizontal components from 134 recording stations located on firm soil sites. Full article

Self-centering structures have emerged as a promising seismic design solution, offering advantages in structural safety, rapid post-earthquake functionality recovery, and life-cycle economy. This paper introduces a self-centering beam–column joint that integrates superelastic shape memory alloys (SMAs) and prestressed steel tendons as restoring components. A numerical model was developed in OpenSees and validated against experimental results, with discrepancies in residual deformation within 10%. The validated model was used for parametric studies on strand area, prestress, and SMA configuration. The results show that the proposed joint sustains a maximum drift of 6% while maintaining nearly zero residual drift (less than 0.2%), and its hysteresis curve exhibits a stable flag-shaped pattern. The equivalent viscous damping ratio exceeds 0.1, confirming excellent deformation and energy dissipation capacities. These findings highlight the joint’s potential for application in seismic-resilient steel frames. Full article

Alginate and chitosan (Ag/Cs) combined form an effective platform to develop biocompatible hydrogels with customizable properties for controlled drug release. Cannabidiol (CBD), a hydrophobic compound with anti-inflammatory and antibacterial effects, represents a powerful strategy to enhance their therapeutic performance. A/Cs hydrogels were produced using the CELLINK^® printer with 12 and 24 mg/mL of CBD. SEM and FTIR were assessed. Viscoelasticity was assessed using oscillatory rheology. Structural strength was evaluated via uniaxial compression. Swelling and absorption were measured gravimetrically under physiological conditions. CBD was successfully incorporated into the 3D-printed A/Cs hydrogel. Increasing the CBD concentration led to mechanical changes such as a dose-dependent decrease in G′ and a slight reduction in the linearity threshold (typically 10–30% from medium loads), while still maintaining G′ > G″. FTIR showed shifts in O–H/N–H and C=O, indicating hydrogen bonding without new reactive bands. Microscopic images revealed moderate pore compaction and increased tortuosity with dose. At higher CBD concentrations, the hydrogel resisted compression but could deform further before failure. Equilibrium swelling and absorption kinetics decreased with increasing dose, resulting in a reduced initial burst and lower water uptake capacity. The CBD-loaded hydrogel provides a mechanically suitable and molecularly stable platform for local drug release in the oral cavity. Full article

Fire hazard presents a critical challenge to the structural reliability of underground modular infrastructure. This study examines the fire resistance performance of prefabricated monolithic utility tunnels featuring longitudinal threaded connections. A series of fire exposure tests was conducted on assembled utility tunnel specimens using different bolt materials and thermal conditions, enabling evaluation of fire behavior, deformation behavior, and residual capacity. The observed thermal properties revealed significant temperature gradients across tunnel sections, with the peak internal–external differential reaching 536.8 °C. Post-fire mechanical degradation was evident in reduced stiffness and ductility, and the residual load-bearing capacity declined by up to 12.28% compared to unexposed specimens. Specimens using high-strength threaded bolts demonstrated superior performance compared to stainless steel bolt specimens, exhibiting a 4.67% higher residual capacity and 13.87% less residual deformation. A sequential thermal–mechanical finite element model was developed and calibrated based on experimental results, offering a reliable simulation framework for investigating fire-induced damage and residual strength in modular utility tunnel systems. These findings provide a quantitative basis for fire safety assessment. Full article

Global coastal reclamation areas face significant land subsidence, threatening infrastructure and sustainable development. China’s large-scale projects show particularly severe subsidence. For example, Tianjin’s Binhai New Area contains 413.6 km² of reclaimed land, and subsidence is driven by soft soil consolidation, industrial loads, and dynamic land use changes. This study addresses the unique geology of coastal reclamation zones: thick, soft clay layers; high porosity; and low soil strength. We employed optimized Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technology using 48 Sentinel-1A radar images (2019–2022), which generated high-resolution annual deformation rate maps revealing a north-high, south-low subsidence gradient. Crucially, validation against leveling data confirmed reliability. The systematically quantified results demonstrate built areas and the bare ground intensifies subsidence through structural loads and soil compression. Land use transitions also exacerbate differential settlement. For coastal cities and reclamation zones, key strategies emerge, including regulating structural loads in high-subsidence areas, managing soft soil consolidation, and implementing dynamic monitoring. Aligning development intensity with geological capacity is essential, and adopting adaptive spatial planning can mitigate subsidence hazards. This approach offers a scientific framework for enhancing global coastal resilience. Full article

Bulk-fill composite resins (BFCRs) have emerged as efficient alternatives to conventional restorative systems, enabling placement in thicker increments without compromising polymerization; however, their comparative mechanical performance under clinically demanding conditions remains uncertain. This study aimed to evaluate and compare the mechanical properties—flexural strength (FS), elastic modulus (EM), strain (ε), and displacement (δ)—of three high-viscosity bulk-fill resins: Filtek One™ Bulk Fill (3M ESPE), Tetric^® N-Ceram Bulk Fill (Ivoclar Vivadent), and Opus™ Bulk Fill (FGM). Thirty specimens (n = 10 per group) were fabricated according to ISO 4049:2019 and subjected to three-point bending tests. Statistical analysis included Shapiro–Wilk testing for normality, one-way analysis of variance (ANOVA) with Tukey’s post hoc comparisons, multivariate analysis of variance (MANOVA), and Spearman’s correlation. Filtek One™ Bulk Fill exhibited the highest FS 142.5 megapascals (MPa) and EM 4.2 gigapascals (GPa), with significant differences compared to Tetric^® N-Ceram Bulk Fill and Opus™ Bulk Fill (p < 0.001). Opus™ Bulk Fill demonstrated greater deformation capacity before fracture (p = 0.015). MANOVA revealed a significant effect of resin type on overall mechanical behavior (Wilks’ λ = 0.132; p < 0.001). Strong correlations were observed between strength and stiffness (ρ = 0.82), and between stiffness and deformation (ρ = –0.68). These findings confirm that BFCRs differ significantly in mechanical behavior, with Filtek One™ Bulk Fill exhibiting superior stiffness and resistance, while Opus™ Bulk Fill showed greater deformation capacity. Such differences support material selection based on the functional and anatomical demands of restorations, contributing to improved clinical performance and longevity. Full article

Yeast protein (YP) offers nutritional and sustainable benefits; however, its poor gelation properties limit its use in soft material formulations. This study investigates the rheological behavior and the formation of crosslinked networks using YP–polysaccharide mixtures for extrusion-based 3D printing. Binary bioink blends with alginate (Alg) or xanthan gum (XG) showed enhanced viscosity and exhibited shear-thinning properties. However, a high concentration of Alg negatively affected the material’s thixotropic recovery. On the other hand, YP–XG bioink displayed more pronounced elastic behavior and demonstrated thixotropic recovery, though they lacked the capacity for ionic crosslinking. A triple bioink formulation consisting of 8% (w/v) YP, 2% (w/v) Alg, and 0.5% (w/v) XG effectively combined the advantages of both polysaccharides. Alg provided structural stability through calcium crosslinking, while XG offered rheological flexibility. These bioinks were successfully printed using embedded 3D printing and maintained their shape fidelity after printing. The crosslinked triple hydrogel exhibited good mechanical strength, volume retention after crosslinking, structural integrity under compression of up to 70%, and recovery after deformation that indicates high structural stability. This research presents an effective strategy to enhance the application of yeast-derived proteins in sustainable, animal-free 3D printed food products and other soft biomaterials. Full article

Traditional manufacturing methods of wind tunnel nozzles are often cumbersome, time-consuming, and costly. The study of spinning forming technology for wind tunnel nozzles provides a pathway to improve manufacturing efficiency while reducing both cost and production cycle. However, when processing alloy steel (20MnMo), challenges arise due to large deformation, high-temperature loading, and complex wall-thickness control. To address these issues, this work proposes a die-less multi-pass hot spinning process. A three-dimensional dynamic explicit finite element model was developed to simulate the stress–strain evolution during multi-pass spinning. In the first pass, an L9 orthogonal experimental design was applied to analyze the influence of spinning parameters on forming stress and plastic deformation capacity, thereby determining the optimal combination of workpiece rotation speed, axial feed, and radial feed rates. The optimized design strategy was subsequently extended to ten passes. Based on simulation results, hot spinning experiments were conducted, followed by precision machining of the nozzle’s inner and outer surfaces. Inspection results indicated that the deviations in contour and wall thickness between simulation predictions and actual specimens were both less than 0.5%. This study establishes an integrated process route combining numerical simulation, hot spinning, and finishing, providing both theoretical support and practical guidance for the high-precision and high-stability manufacturing of complex thin-walled nozzle structures. Full article

Auxetic structures, characterized by a negative Poisson’s ratio and unique form-fitting deformation, are adopted for designing a bra pad that would facilitate bras with a flexible and adaptive fit. This study compares the pressure distribution between auxetic and traditional molded bra pads, highlighting the advantages of auxetic materials in applying uniform pressure and addressing health concerns. Seven athletic female participants with a bra size of 75B comprise the study sample. Anthropometric data of naked breasts are collected by using three-dimensional (3D) scanning to obtain the underbust and full bust dimensions in the standing and leaning forward positions, while the pressure distribution is measured with the Novel Pliance^® pressure measurement system in three poses: standing, static cycling, and dynamic cycling. The results show that the auxetic designs of bra pads consistently apply a more uniform pressure distribution compared to traditional foam pads, with mean pressures of 2.92 kPa for auxetic pads compared to 4.81 kPa for traditional foam pads during static cycling. Moreover, auxetic pads reduced maximum pressure by 25% compared to molded cups, and spatial variability was halved (SD 0.85 kPa vs. 1.70 kPa). Notably, at the bra neckline, auxetic pads exhibit increased pressure as the body leans forward, demonstrating their ability to adapt to changing breast shapes while maintaining adequate bra-breast contact. In contrast, in the lower breast area, the auxetic pads show a decrease in pressure, which indicates their capacity to accommodate variations in breast girth or volume without exerting excessive force. These findings highlight the superior adaptability and wear comfort provided by an auxetic structure, which shows its potential to address the dynamic support needs of active women. Overall, the auxetic designs of a bra pad in this study represent a significant advancement in sports bra technology and offer a promising alternative to traditional molded cups in activewear design. Full article

To optimize the support performance of rock bolts in high-stress environments, this study employs the ANSYS (Version 2022 R2) finite element numerical simulation method to systematically investigate the influence of bolt geometrical parameters (rib spacing, rib height, and bolt diameter) on the stress state of the anchoring system. A bolt–resin–sleeve model was established to analyze Mises equivalent stress distribution and peaks under a 150 kN pull-out load. The simulation results indicate that a rib spacing of 36 mm effectively promotes the diffusion of pre-stress into deeper regions, with peak stress in the bolt rod and resin ring increasing by 34.42% and 61.64%, respectively, compared to a spacing of 12 mm. Further increase in rib spacing provides limited enhancement in peak stress. A rib height of 1.0 mm achieves optimal system performance without excessively compromising the interfacial stress level. Increasing the diameter to 22 mm raised peak stress in the bolt, sleeve, and resin by 14.19%, 30.48%, and 50.77%, respectively, compared to 18 mm, balancing load capacity and material use efficiently. The optimal parameter set (36 mm spacing, 1.0 mm height, and 22 mm diameter) was validated in a field trial in Zhongmacun Mine’s 3903 East Transportation Bottom Drainage Roadway. Monitoring recorded maximum roof subsidence of 102.9 mm, stabilizing within 25 days (daily deformation < 0.2 mm), confirming the excellent performance of the bolt support system with this parameter combination in high-stress roadways. This study provides a theoretical basis and engineering reference for the optimal design of high-performance rock bolts. Full article

The overturning resistance of trees under lateral loads depends on the interaction between their root system and the surrounding soil, with leeward lateral roots being particularly important. This study presents a parametric investigation into the behaviour of leeward lateral roots during tree overturning using the finite element method (FEM) based on a beam-on-nonlinear-Winkler-foundation (BNWF) approach. The model efficiently simulates large root–soil deformations using non-linear p-y connectors, the properties of which were calibrated against 2D plane-strain continuum FEM simulations and validated against analytical solutions for pipeline bearing capacity (an analogous problem). Simulations varied in root diameter, length, and material properties. A critical root length was identified, beyond which further increases in length do not enhance the root’s contribution to tree moment capacity, defining an optimal root length for peak resistance. The study further demonstrates that moment capacity is profoundly more sensitive to root diameter than to length. Initial rotational stiffness, which is highly relevant to non-destructive field-based winching tests, was also found to be primarily controlled by diameter and independent of length for most practical cases. A direct comparison between leeward and windward roots under specified rotation conditions confirmed the greater mechanical contribution of leeward roots to anchorage, which is consistent with field observations. Full article

Ordinary concrete exhibits inherent brittleness, which restricts its deformation capacity and durability under extreme loading conditions. Engineered cementitious composites (ECC) have been developed to address these limitations; however, conventional ECC often suffers from relatively low compressive strength, limiting its use in demanding structural applications. To overcome this drawback, high-strength ECC (HS-ECC) was prepared by incorporating high-volume mineral admixtures and three types of synthetic fibers-polypropylene (PP), polyethylene (PE), and polyvinyl alcohol (PVA). This study aimed to investigate the influence of fiber type and dosage on the flexural behavior of HS-ECC and to propose a toughness evaluation framework better suited to its strain-hardening characteristics. A comprehensive experimental program, including compressive and four-point bending tests, was conducted to evaluate failure modes, flexural performance, and post-cracking behavior. Results showed that PE fibers significantly enhanced flexural strength and toughness, PP fibers provided superior deformability at higher dosages, while PVA fibers tended to fracture due to strong matrix bonding, limiting their effectiveness in high-strength matrices. Based on the observed load–deflection responses, a physically meaningful flexural toughness evaluation method was developed, which reliably captured elastic, hardening, and softening stages of HS-ECC. The findings not only clarify the role of different fiber types in HS-ECC but also offer a new evaluation approach that can guide fiber selection and mix design for structural applications. Full article

The failure behaviour of historic unreinforced masonry (URM) structures is strongly influenced by the properties of bricks and mortar. Over time, degradation processes compromise these materials, with significant effect on structural response and safety. Nevertheless, deterioration effects on the nonlinear behaviour of masonry have been only marginally investigated. This study investigates the mechanical behaviour and failure mechanisms of historic brick masonry with weak and irregular mortar joints, representative of Mediterranean traditional constructions. An extensive experimental programme was conducted on mortars, historic clay bricks, prisms, wallets, and triplet specimens, complemented by in-situ flat jack tests. Results confirm the critical role of mortar quality and joint irregularities in reducing compressive and shear strength and in influencing deformation capacity of historic masonry. The experimental findings served as a basis for the calibration of a Finite Element Model (FEM), subsequently employed to gain deeper insight into the governing failure mechanisms in a real study case. A critical discussion of compression and shear failure criteria is presented, focusing on historic masonry. Experimental and analytical comparisons show major discrepancies in classical criteria, especially with degraded mortars. The study shows that in historic masonry with weak joints, failure is often governed by compression rather than shear. Full article