Search Results (88)

Prefabricated post-pouring UHPC (ultra-high performance concrete) beam–column joints have the advantages of strong integrity, excellent seismic performance and good durability, but there are also problems of easy cracking of old and new concrete interfaces and concrete near the interface. Therefore, a new type of post-cast UHPC joint is designed in this paper. The joint is connected by post-cast UHPC at the beam and column sections far from the core area, and the keyway is set in the connection section to solve the defect that the old and new interfaces easily crack. The refined finite element model of the joint was established by using the finite element software ABAQUS (2023). Through the simulation of 10 working conditions, the typical failure modes and seismic performance of the joint were discussed in depth, and the influence of key parameters such as the lap length of steel bars, the strength of steel bars and the strength of post-pouring UHPC was analyzed. The results show that the joint cracks first appear at the junction of the beam–column core area and develop along the cut-off interface between ordinary concrete and UHPC. No macroscopic cracks were observed in the post-pouring UHPC connection section, and the structure was finally destroyed due to the crushing of ordinary concrete. Increasing the lap length of the steel bar can improve the peak bearing capacity and stiffness of the joint, but it will accelerate the stiffness degradation. Increasing the strength grade of steel bars can significantly improve the bearing capacity and stiffness of the joints, but the energy dissipation capacity is slightly reduced. In addition, the improvement effect of UHPC strength is closely related to the strength of steel bars: when an HRB500 steel bar is used, high-strength UHPC can show better bearing capacity, stiffness and energy dissipation performance, while the improvement effect is not significant when an HRB400 steel bar is used. The research results can effectively inhibit the development of interface cracks and provide a theoretical reference for the subsequent full-scale test and the seismic design of precast joints with post-cast UHPC connections. Full article

This study addresses the complexity and high cost associated with traditional temporary formwork in post-cast strips. An innovative use of fish-scale mesh as a permanent interface material is proposed. This material serves as both construction framework and a connector during the service phase. The study investigates the enhancement mechanism of fish-scale mesh on the interfacial bond between new and old concrete. A multi-parameter experimental framework combined with full-field strain measurement was employed. Three specimen types with varying hole heights and numbers were designed and fabricated. Macro-mechanical properties were evaluated through double-shear and splitting-tensile tests. The interfacial strain field was quantified with high precision and visual clarity using Digital Image-Correlation (DIC) technology. Results show that introducing fish-scale mesh alters the interface failure mode. In mesh-free specimens, failure occurs through brittle interfacial delamination. With fish-scale mesh, failure transitions to ductile rupture within the concrete body. The number of holes has the greatest effect on shear strength, followed by hole height. Among all configurations, the fish-scale mesh with a hole height of 6 mm and 30 holes demonstrated the best performance. The shear strength and splitting strength increase by about 32% and 13%, respectively, compared to mesh-free specimens. Based on experimental results and theoretical derivation, a shear-bearing capacity formula for the fish-scale mesh interface is proposed. This model innovatively incorporates the shear key area of the fish-scale mesh, along with weakening and disturbance coefficients derived from experimental data. The theoretical model was validated against experimental results, showing a good agreement and supporting the use of fish-scale mesh as a permanent interface material. Full article

A bond interface between new and old concrete is inherently present in bridge widening and rehabilitation projects. Under marine environmental conditions, this interface provides a preferential pathway for chloride ion transport, thereby accelerating chloride-induced corrosion of the bridge structure. Although the mechanical bonding performance of such interfaces has been extensively investigated, the durability of new-to-old concrete systems remains significantly inferior to that of monolithic concrete, particularly in terms of resistance to chloride penetration. In this study, chloride erosion tests on new-to-old concrete specimens were conducted under drying–wetting cycle conditions to investigate the influence of the bond interface on the spatial distribution and temporal evolution of chloride concentration. The results indicate that the chloride concentration at the bond interface is significantly higher than that in other regions. This leads to a dual transport mechanism, where chloride ions not only diffuse inward perpendicular to the exposed surface but also migrate laterally from the interface into the adjacent concrete driven by concentration gradients. Based on these findings, an interface influence coefficient is proposed to quantify the effect of the bond interface on chloride transport capacity. This coefficient exhibits a strong fit with the GaussAmp function. Furthermore, a diffusion coefficient model for new-to-old concrete incorporating the effect of the bond interface is established. Full article

Tool wear in CNC milling increases friction and torque demand at the tool-workpiece interface, which is reflected in spindle motor current. This study develops a non-intrusive tool wear condition classification method using spindle motor current monitoring during practical CNC milling of commercial medium-carbon steel workpieces (JIS S50C/AISI SAE 1050-equivalent; as-received and non-heat-treated; nominal laboratory hardness approximately 4.3 HRC). Experiments were performed on a Tongtai MDV-508 vertical machining center at fixed cutting conditions (3000 rpm spindle speed, 2 mm axial depth of cut, 5 mm cutting width, and 300 mm/min feed rate) using eight TiAlN-coated fine-grain WC–Co solid carbide end mills (10 mm diameter, four flutes; nominal Co binder approximately 10 wt%). An oil-based HS Highstart/HS-SSHS-BH10 cutting fluid was applied through the machine external coolant nozzle in flood mode at an estimated nominal flow rate of approximately 3 L/min and near-room coolant temperature (25 ± 2 °C), and was used as supplied without dilution. A clamp-type AC current sensor was installed on one phase line supplying the spindle motor, and current was acquired using an NI-9221 module at 20 kHz. Cutting intervals were isolated by envelope-based segmentation, concatenated, and divided into 1 s windows (0.5 s overlap) for feature extraction. Three feature sets were evaluated: time-domain statistics, frequency-domain statistics, and an FFT→PCA hybrid representation. Tool states (New, Mid-life, Old) were labeled using post-process surface roughness Ra thresholds supported by microscope observation. The PCA transformation was fitted only on training data and then applied to the held-out test data. A logistic regression classifier achieved 97.44% test accuracy (152/156 windows; 95% Wilson CI: 93.59–99.00%) with the PCA-hybrid features, outperforming time-domain (89.74%) and frequency-domain (94.87%) models. The results support spindle current monitoring as a low-cost approach for quality-aligned tool condition monitoring, while the external validity remains limited to the tested machine, material, tool, coolant, and cutting-parameter combination. Full article

Historical and cultural districts are the outcome of cultural sedimentation brought about by urban development, and they embody distinctive urban historical and cultural connotations. Ignoring the protection of the historical and cultural value contained in streetscapes will not only decrease the life quality of residents but will also diminish distinctive local urban features. This study focused on the Fangcheng historical and cultural district in Shenyang. The scenic beauty estimation method was employed to evaluate urban style and features’ visual quality, while the semantic differential method was used to obtain the subjective perceptual features of samples. The study also systematically explored the dynamic relationship between urban style and features’ quality and subjective perception in historical and cultural districts. The results show that color richness, coherence, iconic status, and continuum all exert significant positive predictive effects on visual preferences regarding urban style and features. Color richness was the primary determinant of urban style and features’ visual quality. Continuum interfaces, a unified spatial texture, and coordinated dimensions contributed significantly to improving urban style and features’ visual quality in historic and cultural districts. The distinctiveness and cultural iconic status of historical and cultural districts enhanced the residents’ identity and place memory. Moreover, the coherence and continuum of style between the old and new elements promoted an integrated aesthetic experience. The evaluation results revealed that the overall visual quality of urban style and features of most streets was medium. However, streets with a higher visual quality cluster among historical streets and commercial streets. The residential streets demonstrated a significantly lower visual quality. Establishing a comprehensive evaluation system that integrates urban style and features, subjective perception, and the style of historical and cultural districts can contribute to covering the shortage in the traditional urban style and features’ research and also provide a basis for urban regeneration at the micro scale. Full article

To address issues such as web and bottom plate cracking and insufficient bending capacity in in-service prestressed concrete box girder bridges, this study proposes internal prestressing and section enlargement composite reinforcement. Firstly, taking a bridge of Shenhai Expressway as the background project, the combined reinforcement method is designed and the reinforcement effect is analyzed by MIDAS/Civil. Secondly, through numerical analysis, the influence of the bond shrinkage of self-compacting concrete with different mix ratios on the stress of the web of the original box girder is analyzed, and the interface between the new and old concrete is carried out. The analysis of the loss of the new prestress on the bonding surface of the new and old concrete is carried out by parameters such as the interface planting rate, the interface shear stiffness and the reinforcement structure. Furthermore, the theoretical calculation method of prestress loss rate of new and old concrete bonding interface is obtained. The results show that the flexural capacity of the normal section of the main beam is significantly improved after reinforcement, and the surplus coefficient is 1.18, which meets the requirements of the secondary safety level, and the mid-span deflection is improved by 34.28%, which verifies the effectiveness and feasibility of the combined reinforcement method. When the content of fly ash is 54%, the bond shrinkage strain and shrinkage stress of self-compacting concrete are reduced to the lowest level, which has the least influence on the existing box girder structure. It is suggested that the reinforcement ratio between the new and old concrete interface is 0.6%, and the interface roughness is 0.9 mm, which can increase the shear resistance of the new and old concrete interface and effectively reduce the transfer loss of prestress at the interface. Error analysis shows that the proposed semi-empirical calculation method has high accuracy with a deviation of less than 10%. Full article

High-slump concrete is highly sensitive to vibration due to its low viscosity and weak cohesion, factors that critically influence its performance development and long-term durability. In practice, vehicle–bridge coupled vibrations during half-width bridge construction represent a typical condition that intensifies these effects. This study investigates performance deterioration of high-slump concrete subjected to simulated vibration modes reflecting construction scenarios. Mechanical and durability properties were evaluated, and microstructural changes were analyzed using SEM. Results show that early vibration enhances compressive strength at early ages, but this benefit diminishes with curing. The bonding performance at the new–old concrete interface is highly sensitive to vibration timing, casting-to-final setting vibration greatly reduces bond strength, while initial-to-final setting vibration causes minor damage or slight improvement. Vibration modes also differently affect durability: initial-to-final setting weakens frost and abrasion resistance, whereas casting-to-final setting enhances pore structure and chloride resistance. SEM analysis reveals vibration-induced dispersion of hydration products, reduced C-S-H gel formation, and increased microcracks at the fresh–old interface. Both vibration modes further promote microcracks and porosity after freeze–thaw cycles, damaging the gel structure. Overall, this study clarifies the mechanisms by which vibration timing governs the performance evolution of high-slump concrete and provides a scientific basis for optimizing vibration procedures to ensure durability and interfacial reliability in engineering applications. Full article

Shear strength, which indicates the interfacial bond performance between new and old concrete, is critical in the field of structural reinforcement and rehabilitation. However, the absence of standardized testing equipment has hindered the accurate quantification of this parameter. To address this gap, a dedicated shear-loading apparatus was designed in this study, and finite element modeling was conducted to simulate the shear performance of concrete with different interface roughness. The results show that failure consistently occurs at the interface and that roughness has significant influence on shear capacity. In order to reveal the relationship between shear strength and surface roughness, shear experiments were conducted on new–old concrete using the device we designed. The surface of old concrete was treated by water-jetting, electric hammering, grooving, or grout seal strip to create different profiles, the roughness was quantified by 3D scanning and Fourier transform analysis, and fresh concrete was then cast atop the processed surfaces to form composite specimens. The results show that the correlation between shear strength (τ) and Fourier transform roughness (FTR) can be described with the equation τ (MPa) = 0.546FTR² + 1.832FTR − 0.447. Full article

Accurate prediction of shear strength at the interface between new and old concrete is vital for the structural performance of repaired and composite systems. However, the underlying shear transfer mechanism is highly nonlinear and influenced by multiple interdependent factors, which limit the applicability of conventional empirical models. To address this challenge, an interpretable machine-learning (ML) framework is proposed. The latest database of 247 push-off specimens was compiled from the recent literature, incorporating diverse interface types and design parameters. The hyperparameters of the adopted ML models were optimized via a grid search to ensure the predictive performance on the updated database. Among the evaluated algorithms, eXtreme Gradient Boosting (XGBoost) demonstrated the best predictive performance, with R² = 0.933, RMSE = 0.663, MAE = 0.486, and MAPE = 12.937% on the testing set, outperforming Support Vector Regression (SVR), Random Forest (RF), and adaptive boosting (AdaBoost). Compared with the best empirical model (AASHTO, R² = 0.939), XGBoost achieved significantly lower prediction errors (e.g., RMSE was reduced by 67.8%), enhanced robustness (COV = 0.176 vs. 0.384), and a more balanced mean ratio (1.054 vs. 1.514). The SHapley Additive exPlanations (SHAP) method was employed to interpret the model predictions, identifying the shear reinforcement ratio as the most influential factor, followed by interface type, interface width, and concrete strength. These results confirm the superior accuracy, generalizability, and explainability of XGBoost in modeling the shear behaviors of new–old concrete interfaces. Full article

Upgrading the industrial structure is an essential step for economic growth and the transformation of old and new development drivers. Counties situated at the rural–urban interface hold a comparative advantage in industrial upgrading compared to cities, converting agricultural resource dividends into economic value. However, whether agricultural innovation talent can facilitate this process requires further investigation. Based on a sample of 1771 Chinese counties, this study employs a quasi-natural experiment using China’s “World-Class Disciplines” construction program in agriculture and establishes a difference-in-differences (DID) model to examine the impact of agricultural innovation talent on county-level industrial structure upgrading. The results show that agricultural innovation talent significantly promotes industrial upgrading, with this effect being more pronounced in counties with smaller urban–rural income gaps, greater household savings, and higher levels of industrial sophistication. Spatial spillover effects are also evident, indicating regional knowledge diffusion. Knowledge empowerment emerges as the core mechanism: agricultural innovation talent drives industrial convergence, responds to supply–demand dynamics, and integrates digital and intelligent elements through knowledge creation, dissemination, and application, thereby supporting county-level industrial upgrading. The findings highlight the necessity of establishing world-class agricultural research and talent incubation platforms, particularly emphasizing the supportive role of universities and the knowledge-driven contributions of agricultural innovation talents to county development. Full article

In shield tunneling, ensuring bonding performance at new-to-old concrete interfaces between segments and linings is crucial for composite lining stability. While extensive research exists on the mechanical bonding behavior of such interfaces, comparative studies on two prevalent treatment methods—scabbling and grooving—remain limited. This study systematically evaluates these techniques’ effects on interfacial bonding via direct shear tests, benchmarking against smooth-interface specimens. Complementary cohesive zone modeling simulations further analyze stress distribution and damage evolution during shear failure. The results demonstrate that scabbled specimens exhibit 10.5%~18.2% higher shear strength than grooved counterparts under increasing normal stress, with both treatments significantly enhancing load–transfer synergy through mechanical interlocking. Furthermore, the energy-based bilinear cohesive model accurately predicts full-interface behavior, providing practical guidance for interface treatment selection in tunneling engineering. Full article

How can AI help us connect to the past in terms of conservation? How can 17-year-old photos be helpful in renewed preservation efforts? This research aims to use AI to connect both in a seamless 3D reconstruction of heritage from images taken of Gongfan Palace, Yunlin, Taiwan. AI-assisted 3D modeling was used to reconstruct the details of these images across different 3D platforms of the 3DGS or NeRF models generated by Postshot^®, RODIN^®, and KIRI Engine^®. Mesh and point models created using Zephyr^® were referred to and assessed in three sets. The consistent and inconsistent reconstructed results also included AI-assisted modeling outcomes in Stable Diffusion^®- and Postshot^®-based animations, followed by a 3D assessment and section-based composition analysis. The AI-assisted environment concluded with a recursive reconstruction involving 3D models and 2D images. AI assisted the 3D modeling process in an alternative approach, producing extraordinary structural and visual details. AI-trained models can be assessed and their use extended to composition analysis by section. Evolved documentation and interpretation using AI enables new structures and the management of resources, formats, and interfaces as part of continuous preservation efforts. Full article

Pipeline leakage can induce ground surface settlements and structural responses in existing tunnels. A thorough understanding of pipeline–tunnel interactions is crucial for optimizing urban underground design and establishing construction guidelines. As urban underground spaces undergo rapid, large-scale development, their layouts have grown increasingly complex. Previous studies have mainly focused on the leakage propagation range and the resulting strata instability during tunnel excavation, while paying limited attention to the effects of pipeline leakage on existing tunnels. This study systematically investigated the mechanical response of existing tunnel structures to pipeline leakage under different layout configuration conditions using numerical modeling. A two-dimensional numerical model was developed to simulate the pipeline leakage process and its impact on adjacent tunnels. The research established a correlation between surrounding rock strength parameters and the saturation degree while examining the evolution patterns of leakage effects in various tunnel–pipeline arrangements. The analysis specifically focused on the mechanical influence of horizontal pipeline–tunnel distance, quantitatively determining the relationships among pipeline–tunnel spacing, leakage duration, and structural internal force. The horizontal pipeline–tunnel distance did not influence the development of the leakage zone above the tunnel vault but significantly altered the seepage path length and interface contact area. The complete encapsulation of the tunnel periphery by the leakage zone required progressively longer durations with increasing horizontal offsets: 16 days (0 m), 20 days (3 m), and 33 days (6 m). Corresponding circumferential contact ratios at 10 days were measured at 68.9%, 56.4%, and 30.6%, respectively. Furthermore, prolonged seepage duration led to increased ground subsidence with expanded affected areas, while the maximum settlement decreased proportionally with greater horizontal separation from the tunnel. These findings provide valuable insights for planning, designing, and maintaining “old tunnel-new pipeline” systems in urban underground development. Full article

Background/Objectives: The structural integrity and strength of the transgingival soft tissue seal around dental implant surfaces remain critical challenges. Therefore, animal models should include all three implant/tissue interfaces: bone, connective tissue, and epithelium. Thus, we sought to explore the rabbit mandibular diastema as a site for candidate intra-oral implant placement. Methods: Ninety-six custom mini-implants (with one of four different surfaces: machined, acid-etched, and with or without a nanotube coating) made from titanium 6/4 alloy were placed in the mandibular diastemas of twenty-four 16-week-old New Zealand white rabbits, with the implant collar above the alveolar crest. After 7, 21, and 42 days, the bony and connective tissue/implant interfaces were examined by light and scanning electron microscopy (SEM). Results: Of ninety-six implants, eight implants were found exposed to the oral cavity, with no evidence of soft tissue inflammation, suggesting that transmucosal implant placement would have been feasible. No significant differences were observed in collagen fiber orientation and fibrous tissue thickness by polarized light microscopy. However, SEM images showed that at all three time points, topographically complex nanotube surfaces had a profound effect on soft tissue peri-implant deposition, although functionally oriented collagen fibers were not identified attached to the implant surface. These surfaces also showed reparative peri-implant bone in the collar region. An intramembranous form of de novo bone formation was observed, together with tartrate-resistant acid-phosphatase-positive osteoclasts and multinucleate giant cells in the peri-implant endosseous compartment. Conclusions: Our results demonstrate that the rabbit mandibular diastema provides an intra-oral method of implant placement without the necessity of an extra-oral approach, tooth extractions, or bone augmentation procedures. Furthermore, given that three implant tissue interfaces can potentially be studied (bone, connective tissue, and epithelium) this model provides advantages over more traditional implant placement sites in the appendicular skeleton. Full article

Worldwide energy needs are growing, requiring new extraction techniques for crude oil from old reservoirs. However, conventional chemicals face difficulties when exposed to harsh reservoir environments such as solubility in high saline water and heat stability under harsh reservoir environments. This study investigates the potential of newly synthesized polymeric ionic liquids (PILs) as alternative options. A series of PILs was synthesized and characterized by using NMR and FTIR techniques. It was noticed that a PIL without ethoxy groups exhibits precipitation and therefore is not suitable for oilfield applications. However, the incorporation of ethoxy groups in the chemical structure of PILs leads to excellent solubility in low to high salinity brine. The solubility of the synthesized PILs in formation water, seawater, and deionized water, as well as their thermal stability using thermal gravimetric analysis (TGA), was assessed. In addition, the surface properties, including critical micelle concentration (cmc), surface tension (γ_cmc), surface excess concentration (Γ_max), minimal surface area per molecule (A_min), free adsorption energy (ΔG°_ads), and free micellization energy (ΔG°_mic), were also evaluated. The findings revealed that adding ethoxy groups in PILs led to a drop in Γ_max and an increase in A_min, suggesting reduced monolayer compactness at the air/water interface. The synthesized PILs demonstrated remarkable solubility, heat stability, and resistance to salt, rendering them well-suited for oilfield applications under challenging reservoir environments. Full article