Search Results (651)

In this study, an L₁₆(4³) orthogonal experimental design was employed to optimize the preparation process of rubber-modified asphalt, and a series of rheological tests were conducted using a dynamic shear rheometer to systematically investigate the compatibility mechanisms among the four components: base asphalt and rubber particles. The results indicate that process parameters exert varying degrees of influence on performance. The optimal combination determined was: base bitumen temperature of 170 °C, shear rate of 4000 r/min, and shear time of 40 min, followed by isothermal curing at 170 °C for 60 min. Rheological analysis indicates that resin and asphalt are the key components determining the high-temperature rheological properties of rubber-modified asphalt; notably, L74, which has the highest asphalt content, exhibits excellent high-temperature performance. Grey correlation analysis shows that the correlation coefficient between resin content and creep recovery capacity is 0.82, while the correlation coefficient between asphalt content and resistance to permanent deformation is 0.86. Furthermore, the goodness-of-fit value of the multiple regression model exceeded 0.99, further confirming the reliability of the research results. This study provides a precise characterization of compatibility, thereby offering a theoretical foundation and technical support for material selection and process control in the application of rubber-modified asphalt. Full article

This study investigates the thermo-mechanical response of geocell-reinforced concrete pavements through scaled model tests and three-dimensional finite element analyses. Static, thermal, traffic, and coupled temperature–loading tests were conducted to clarify the deformation evolution, strain distribution, and damage-related response of the reinforced structure. The results show that, under static loading, pavement settlement evolves through three stages, namely initial compaction, plastic development, and stable strengthening, indicating progressive mobilization of geocell confinement. Under thermal loading, slab strain exhibits pronounced spatial and temporal non-uniformity, and the slab center is identified as the thermally sensitive zone. Under coupled temperature–loading conditions, both strain and settlement show a non-monotonic response near 1.1–1.3 kN, suggesting a potential damage-initiation range. Post-test crack observations further provide direct qualitative evidence that local cracking damage occurred in the slab under representative loading conditions. Under traffic loading, permanent deformation accumulates with load repetitions and is highly sensitive to load amplitude, indicating a load-sensitive transition in cumulative deformation behavior rather than a definitive fatigue threshold. Numerical results further show that geocell reinforcement reduces central settlement by 17.4% relative to plain concrete pavement and by 7.6% relative to doweled pavement, while producing a smoother deflection basin and a more uniform stress distribution. Parametric analyses indicate that the optimum geocell height is approximately one-third of the slab thickness; beyond this range, the marginal reinforcement benefit decreases. Overall, the results demonstrate that geocell reinforcement can effectively improve load transfer, deformation compatibility, and thermo-mechanical stability of concrete pavements under the investigated conditions. Full article

This work experimentally evaluates the geometry-driven structural efficiency and normative performance of sandwich-type composite roofing tiles composed of a miriti wood core and fiberglass-reinforced polymer faces. Trapezoidal-profile tiles were manufactured by hand lay-up and assessed according to ABNT NBR 16753, including visual inspection, fiber content, water absorption, apparent flexural behavior, deformation resistance, and impact resistance. The miriti core exhibited an extremely low mean density of 0.091 ± 0.008 g/cm³ (CV ≈ 8.8%), enabling lightweight sandwich configurations with an average overall thickness of approximately 8 mm. Fiberglass contents ranged from 27.5% to 32.1% by mass. Sealed sandwich specimens showed median water uptake values of approximately 2.5% after 2 h and 6.0% after 24 h immersion. Deformation resistance tests indicated admissible deflections of 15.0–15.75 mm (L/40), supported by applied masses between 39.6 and 104.3 kg (≈388–1023 N) without rupture or permanent damage. Apparent flexural stresses ranged from 6.7 to 9.3 MPa, with apparent moduli between 0.7 and 1.9 GPa. All tiles achieved 100% approval in deformation, impact (2–8 J), and visual criteria. The results demonstrate that geometric effects dominate structural performance, validating miriti wood as an efficient and sustainable core for normatively compliant composite roofing systems. Full article

Long-term safety assessment of deep geological repositories for spent nuclear fuel requires explicit evaluation of thermo-mechanical (TM) processes induced by decay heat and their influence on fractured host rock. A safety-relevant, though low-probability, scenario concerns shear reactivation of fractures intersecting deposition holes, which could compromise canister integrity if displacement exceeds design limits. This study presents a three-dimensional discrete element modelling approach to analyze the thermal evolution of the Forsmark repository (Sweden) and the associated long-term response of a discrete fracture network (DFN) during the post-closure phase. The model explicitly represents repository panel, deterministic deformation zones, and a stochastically generated fracture network embedded in a bonded particle assembly representing the rock for Particle Flow Code (PFC) numerical simulations. Time-dependent heat release from spent nuclear fuel canisters is implemented using a physically based decay power function. A deposition panel-scale heat-loading formulation accounts for deposition-hole and tunnel spacing. Two emplacement scenarios are analyzed: (a) a simultaneous all-panel heating scenario, used as a conservative bounding case, and (b) a sequential panel heating scenario representing staged emplacement and closure. The simulations show that temperature and thermally induced stress evolution are sensitive to the emplacement and closure sequence. Sequential heating produces a more gradual thermal build-up and lower peak temperatures than simultaneous heating, indicating that thermal and stress perturbations in the host rock can be influenced not only through repository design, but also by operational strategy. Thermally induced fracture shear displacement displays a systematic temporal response. Fractures located within the deposition panel footprint develop shear displacement rapidly during the early post-closure period, reaching peak values at approximately 200 years, followed by gradual relaxation as temperatures decline. The average peak shear displacement on fractures is on the order of 2–3 mm, while fractures outside the panel footprint show smaller early-time displacements and a more prolonged long-term response. All simulated shear displacements remain more than one order of magnitude below the commonly cited canister damage threshold for Forsmark of approximately 50 mm, even for the conservative simultaneous heating case. These results indicate that thermally induced fracture shear is unlikely to cause direct mechanical damage to canisters. At the same time, the persistence of residual shear displacement after heating implies permanent fracture dilation, which may influence long-term hydraulic properties and indirectly affect processes such as groundwater flow and canister corrosion. The modelling framework and results presented here were conducted for review purposes independently from the Swedish safety case, and provide a mechanistic basis for evaluating thermally induced fracture deformation in crystalline rock repositories and contribute to bounding the role of thermo-mechanical processes in the safety assessment of spent nuclear fuel disposal at Forsmark. Full article

The integration of vertical greenery systems (VGSs) into existing reinforced concrete (RC) buildings raises questions regarding interface kinematics and the permanent displacement of soil-retaining elements under seismic excitation. This study experimentally investigates the residual displacement of façade-mounted living walls and rooftop planter pods anchored to a deficient RC frame under shake table excitation. A 1:3 scale reinforced concrete frame was tested in two distinct phases: initially as a deficient, unretrofitted structure (Phase A), and subsequently as a retrofitted system integrated with vertical greenery elements (Phase B). High-precision terrestrial laser scanning (TLS) was employed before and after successive seismic excitation stages to generate dense three-dimensional point clouds. Cloud-to-cloud comparison techniques were used to quantify global structural displacement and local kinematic behavior of greenery components, while results were validated against conventional displacement sensors. The RC frame exhibited millimeter-scale permanent displacements consistent with draw-wire measurements. In contrast, planter pods demonstrated configuration-dependent behavior, including up to 8 cm translational sliding and rotational responses reaching 13° under repeated excitation, whereas living wall panels remained stable. Notably, a 95% reduction in point cloud density reproduced global deformation patterns with an RMSE of 3.03 mm and quantified peak displacements with only ~2% deviation from full-resolution results. The findings demonstrate the capability of TLS-based monitoring to detect differential kinematic behavior of integrated VGSs, while highlighting the variability in performance of friction-based rooftop anchorage utilizing different robust planter pod fixing systems. Full article

Asphalt pavements are frequently subjected to fatigue cracking, rutting, and surface wear, which accelerate maintenance needs and shorten service life. This study evaluates the performance enhancement of NHA Class B dense-graded asphalt mixtures (12.5 mm NMAS) prepared with a 60/70 penetration grade binder through carbon fiber (CF) reinforcement. Chopped fibers (~12.7 mm) were incorporated via the dry mixing process at dosages of 0.5%, 1.0%, and 1.5% by binder weight. The results indicate that the 1.0% CF mixture delivered optimal performance, with ITS increasing by 51.9%, Marshall stability improving by 38.4%, resilient modulus rising by 42.6%, and rut depth decreasing by 69.2% compared to the unmodified control. Dynamic stability reached 33,750 passes/mm, demonstrating substantial resistance to permanent deformation. Statistical analysis using one-way ANOVA confirmed that all improvements were significant (p < 0.05). Despite a ~6.7% increase in initial cost, the CF-modified mix exhibited strong economic viability, achieving a benefit–cost ratio of 4.79 and significant life-cycle savings over 20 years. These findings underscore carbon fiber as an effective modifier for developing durable, high-performance asphalt composites with reduced maintenance requirements. This work contributes to the advancement of smart and sustainable pavement technologies for resilient transportation infrastructure. Full article

Ventricular septal defect (VSD) occluders commonly rely on permanent nitinol frameworks, which may contribute to long-term mechanical mismatch and late complications. Here, we developed a tissue-compliant composite membrane by embedding a 3D-printed poly(vinyl alcohol) (PVA) grid within a shape-memory poly(glycerol dodecanedioate) (PGD) matrix. Grid spacing was varied from 0.1 to 0.5 mm to tune reinforcement density. FTIR indicated that PVA was incorporated mainly through physical interlocking rather than new covalent bonding. The composite preserved near-body-temperature shape recovery. In water at 37 °C, PVA reinforcement increased tensile modulus and fracture strength, although swelling also increased. Finite-element analysis and benchtop occlusion testing consistently showed lower deformation, less strain localization, and smaller bulge height for PGD–PVA than for PGD alone. In vitro assays showed low cytotoxicity, low hemolysis, and prolonged plasma recalcification time. A 12-week pilot degradation study showed that the faster mass loss observed in initial samples was mainly caused by exposed PVA cut edges; after switching to a fully encapsulated design, static mass loss became similar across groups, and dynamic PBS agitation produced about 10% mass loss at 12 weeks. These results support PGD–PVA as a reinforced membrane strategy for polymeric occluders. Full article

Permanent deformation, manifested as rutting, remains one of the most critical threats to the structural integrity and functional performance of flexible pavements. The Mechanistic–Empirical Pavement Design Guide (MEPDG) includes rutting models that are highly sensitive to the dynamic modulus (E*) of asphalt mixtures—a parameter that can be determined experimentally or predicted by analytical models. In this study, the influence of E* prediction error on rutting estimation is systematically evaluated by comparing laboratory-measured E* values with those predicted by two models: NCHRP 1-37A and a locally calibrated model. The dynamic pavement behavior and rut depth predictions were determined using the finite layer program 3D-Move under standard traffic loads. Comparative analysis revealed that the NCHRP 1-37A model tends to underestimate E*, leading to significant overestimation of vertical strains and accumulated permanent deformation. In contrast, the locally calibrated model provided predictions that closely matched the laboratory measurements, resulting in minimal deviation in rut depth estimates. The results highlight the importance of local calibration and model selection to improve the reliability of mechanistic–empirical pavement predictions, enabling smarter pavement performance evaluation and supporting more sustainable pavement management practices, especially when laboratory testing is not feasible. Full article

Reinforced concrete (RC) structures in marine environments face severe durability challenges due to chloride-induced corrosion. This study investigates the corrosion mechanism and degradation of axial compressive performance in RC columns under the combined effects of sustained loading and corrosion, taking the permanent–temporary integrated RC columns of the Pinglu Canal project as an example. The experimental variables included different sustained load levels and degrees of corrosion. Twelve rectangular RC columns were designed and tested. A specialized setup was developed to simultaneously apply sustained load and induce corrosion to the columns, while monitoring their creep deformation. The columns were subjected to accelerated electrochemical corrosion in a 5% NaCl solution, concurrently under sustained loads of 0, 0.3, and 0.6 times their designed axial compressive capacity, with exposure durations of 0, 30, 60, and 120 days, respectively. The study examined the effects of sustained load level and corrosion degree on the failure mode, concrete creep deformation, and load–displacement curves of the corroded RC columns. The results indicated that sustained loading shortened the duration of concrete expansion deformation and reduced its peak value. Furthermore, the expansion deformation of concrete delayed the creep of corroded columns by 25 to 35 days; after the expansion recovery, the creep rate increased significantly. For corroded columns without sustained loading, the ultimate bearing capacity decreased by 32.0% to 47.8%, with degradations in both stiffness and ductility. The application of sustained loading alleviated the degradation in the ultimate bearing capacity and stiffness of the corroded columns but exacerbated the degradation of their ductility. Finally, considering the effects of concrete expansion deformation and steel corrosion, a predictive model for the creep of RC columns under the coupled action of sustained loading and corrosion was proposed, aiming to provide a theoretical basis for the durability design and maintenance of RC structures in the Pinglu Canal project. Full article

The performance of ballasted railway tracks under cyclic loading is a critical issue in urban railway systems, where high traffic frequency and geometric constraints accelerate track degradation, leading to the accumulation of plastic deformations that may reduce operational efficiency. This study presents a numerical framework for rail track performance assessment based on two complementary modeling approaches: a fully continuous Finite Difference Method (FDM) model, and a hybrid Discrete Element Method–Finite Difference Method (DEM–FDM) model. The continuous FDM simulations are employed to evaluate the global mechanical response of the track support system and to compute conventional stability indicators, including the factor of safety (FS). In parallel, the hybrid DEM–FDM simulations explicitly represent the ballast layer using DEM to capture inter-particle interactions, accumulation of permanent deformation, and particle fragmentation under cyclic loading, while rails, sleepers, sub-ballast, and subgrade are modeled using FDM to describe system-level load transfer. Ballast performance is assessed by linking safety factors obtained from the continuous models with mechanically derived permanent deformation and stress measures extracted from the hybrid simulations. The proposed dual-modeling framework enables a systematic investigation of the influence of ballast layer thickness and material type on deformation accumulation, stress transmission, and granular degradation mechanisms. The results reveal distinct behavioral trends among different ballast materials, showing that increased ballast thickness generally improves track performance, while material-specific degradation mechanisms govern the evolution of permanent deformation under repeated loading. The proposed approach establishes a quantitative bridge between traditional stability-based design metrics and deformation-based performance indicators, providing a rational basis for performance-based evaluation, comparison, and optimization of ballast configurations through a set of robust numerically derived relationships for railway track design. Full article

Structural evaluation of railway tracks in operation requires the integration of field measurements and numerical models capable of adequately representing the mechanical behavior of permanent railway pavement components. In this context, this study presents the structural analysis of a railway segment based on the combination of field instrumentation, laboratory testing, and numerical simulations grounded in the Finite Element Method, adopting linear elastic and resilient material behavior for all track components, using SysTrain software (v.1.88).The objective of this work is to assess the application of a back-analysis methodology based on field instrumentation and numerical modeling, as well as to verify the structural conditions of an in-service railway pavement. The back-analysis was conducted using the SysTrain software, with a focus on calibrating the ballast resilient modulus (RM) and analyzing its effects on the propagation of stresses, internal forces, and displacements throughout the track structure. To this end, field-measured deflections obtained from LVDT sensors installed at the sleeper ends were used, together with the geotechnical, resilient, and permanent deformation (PD) characterization of the underlying soil layers obtained in the laboratory. The results indicated that the calibration of the numerical model requires a ballast resilient modulus in the order of 1500 MPa, suggesting a condition of high layer stiffness. The simulations showed vertical stress levels below 100 kPa in the lower layers, while laboratory tests revealed the high susceptibility of the soils to PD, particularly under moisture variations. It is concluded that the applied methodology enables a consistent assessment of the structural conditions of the track and contributes to a more robust understanding of the ballast response under repeated loading, providing support for railway design, maintenance, and management criteria. Full article

Custom-made subperiosteal implants are increasingly used in clinical cases where significant bone loss due to trauma or disease renders conventional endosseous implant placement unfeasible. This study investigated how different internal structural designs affect the deformation and stress distribution in mandibular subperiosteal implants under clinically relevant loading conditions. An idealized implant geometry was defined based on average human mandibular dimensions, and four configurations with identical outer shape and connection features were created, differing only in sidewall architecture (solid, top-relieved, top-relieved with lateral perforations, and top-relieved lattice framework). All specimens were manufactured by metal additive manufacturing and evaluated using cone-beam computed tomography (CBCT). Mechanical testing was performed in two stages: (i) cyclic loading consisting of 500 bite cycles at an overall force of ~326–350 N and (ii) a single static high-load event of 2000 N, applied parallel to the fixation pin axes. CT datasets acquired before and after each stage were compared to detect permanent deformation. No measurable residual deformation was identified in any configuration; the only observed macroscopic change was an adhesive-bond limitation in one case, rather than structural yielding of the implant. Finite element analysis further supported these findings by identifying localized stress concentrations mainly at the implant–prosthetic interface and by revealing the load-transfer zones that govern the mechanical response. Overall, the results indicate that lightweight, perforated, and lattice-based internal designs can preserve global structural integrity across physiological and supra-physiological load ranges while enabling design optimization to improve stress distribution. Full article

Any risks arising during the construction phase of nuclear power projects become permanently embedded in the power station’s lifecycle, evolving into inherent and difficult-to-alter potential hazards. Consequently, identifying behavioral risks in this phase is critical to the successful delivery of nuclear power engineering projects. This paper proposes a behavior risk identification and early warning methodology for nuclear power construction operations based on artificial intelligence algorithms. The research employs text mining techniques to construct a risk indicator system for nuclear power construction operations; based on the You Only Look Once (YOLOv8) algorithm, it incorporates modules such as Deformable Convolutional Network (DCN), Generalized Lightweight Attention Network (GELAN), Efficient Channel Attention (ECA), and Atrous Spatial Pyramid Pooling (ASPP) to develop the DCN -GELAN-ECA- ASPP-YOLO for Nuclear Power Engineering (DGEAYoLo-NPE) model, and designs and develops a supporting behavior risk identification and early warning methodology. Results show that the precision of nuclear power construction behavioral risk detection reaches 94.3%, with a 2.2% improvement in precision. This study confirms that artificial intelligence technology can effectively enhance the behavior risk prevention and control capabilities of nuclear power construction operations. Full article

Leveraging differential interferometric techniques, ground-based synthetic aperture radar (GB-SAR) delivers highly accurate displacement measurements, typically reaching submillimeter scales. However, in practical engineering, minor platform instability induced by environmental factors gives rise to space-variant baseline errors, which affects the deformation value. In response to this issue, this paper presents a method combining Taylor expansion and singular value decomposition for estimation and compensation of the space-variant baseline error. Initially, the Gaussian Mixture Model (GMM) is employed to adaptively select high-quality Permanent Scatterers (PSs) to facilitate robust data provision for the following error parameter estimation. Subsequently, a three-dimensional multi-parameter model for the space-variant baseline error is established via Taylor expansion, followed by parameter estimation using Singular Value Decomposition (SVD). Experiments indicate that the proposed approach effectively mitigates the error phase arising from platform vibration, thereby enhancing the precision of GB-SAR deformation inversion. Full article

Stone Mastic Asphalt (SMA) mixtures are widely used in high-capacity road pavements due to their durability and resistance to permanent deformation. However, although electric arc furnace (EAF) steel slag and recycled crumb rubber have been individually investigated as alternative materials in asphalt mixtures, evidence regarding their simultaneous incorporation in SMA mixtures under full-scale construction and real traffic conditions remains limited. Moreover, quantitative environmental assessments are often restricted to simplified or qualitative approaches, with limited reporting of carbon footprint results. This study investigates the combined use of electric arc furnace (EAF) steel slag aggregates and recycled crumb rubber in SMA mixtures, integrating laboratory evaluation with full-scale field application on a high-traffic motorway. Two SMA 11 mixtures were designed and assessed: one incorporating steel slag aggregates as a replacement for natural coarse aggregates, and another combining steel slag aggregates with recycled crumb rubber added through the dry process (0.8% by mixture mass). Laboratory testing included volumetric characterization, moisture sensitivity and rutting resistance, while field validation covered surface macrotexture, skid resistance, executed thickness and interlayer bonding. Both mixtures fully complied with the applicable technical specifications, achieving indirect tensile strength ratios (ITSR) above 90% and wheel-tracking slopes below 0.07 mm/10³ cycles. A simplified comparative life-cycle assessment (LCA), limited to modules A1–A3, showed a reduction in CO₂-equivalent emissions of approximately 2% for the mixture containing steel slag and up to 27% for the mixture combining steel slag and recycled crumb rubber, mainly due to the valorization of industrial by-products and end-of-life tyres. Overall, the results demonstrate the technical feasibility and potential environmental benefits of these SMA mixtures within the defined scope of laboratory verification, short-term field performance and screening LCA. The contribution of this study lies in providing applied evidence from a full-scale motorway intervention, complementing predominantly laboratory-based studies and offering a quantified environmental comparison under consistent methodological assumptions. Full article