Abstract:To address the inadequacies in the research of vertical permanent component connection joints， a column-to-column dry connection joint suitable for the jacking reverse construction is proposed. A static load-bearing calculation model for the new joint is developed. A finite element model is established to analyze the effects of parameters such as axial compression ratio， upper-to-lower column height ratio， and bolt arrangement in the joint on its seismic performance. The results indicate that the new joint can reliably connect the upper and lower segments of the column. The specimens exhibit ductile bending failure under a reasonable shear-span ratio. With the axial compression ratio increasing， the ultimate load of the specimen decreases. When the upper-to-lower column height ratio is 1/3， the bearing capacity of the specimens with the new column-to-column connection joint is equivalent to that cast-in-place specimen. Under high axial compression ratios， its displacement ductility is close to that of the cast-in-place specimen， and the energy dissipation capacity is only about 6% lower when the height ratio of the upper-to-lower column height ratio is 1/3. The proposed restoring force model is in good agreement with the simulation results.

Abstract:To address issues such as multi-compartment design， heavy self-weight， and susceptibility to cracking and water leakage in prefabricated assembled reinforced concrete （RC） box utility tunnels， this paper proposes a ribbed ultra-high performance concrete （UHPC） utility tunnel structure. Static loading tests were conducted on UHPC plates with three different cross-sectional shapes， rectangular， trapezoidal， and flat， with varying rib heights， to analyze the effects of parameters such as reinforcement ratio， rib height-to-width ratio， steel strength， and UHPC compressive and tensile strengths on the flexural behavior of the components. The results indicate that all specimens exhibit under-reinforced failure， with the steel reinforcement yielding while the compressive capacity of the UHPC is fully utilized. Under the same material usage， the rectangular ribbed plate demonstrates significantly higher load-bearing capacity and stiffness than the trapezoidal ribbed and flat plates. A 50 mm increase in rib height improved the load-bearing capacity by approximately 20%. Increasing the reinforcement ratio， rib height， steel strength， and UHPC tensile strength effectively enhances the load-bearing performance of the ribbed UHPC plates. In particular， using steel reinforcement with a yield strength exceeding 785 MPa or a reinforcement ratio above 2.5% cause the failure mode to shift from under-reinforced to an appropriately reinforced mode.

Abstract:Five shear bearing capacity tests on aluminum alloy connections with diagonally arranged bolts were conducted， confirming the uneven distribution of internal forces among bolts. The influence of parameters such as diagonal angle， bolt spacing， and material properties on the internal force distribution of bolts was studied through parameterized numerical analysis. The research results indicate that the shear force shared by the most unfavorable bolts can reach 180% of the average shear force. Based on the experimental results and numerical analysis， the formula for calculating the maximum internal force distribution coefficient of bolts was obtained through fitting.

Abstract:To investigate the mechanical performance of composite shear walls with irregular steel trusses and concrete， the shear lag effect and skeleton curve were studied. Based on the principle of minimum potential energy， the energy variational method was used to calculate the longitudinal stress distribution inside the flange. The effective coefficient was introduced to consider the role of the end section steel vertical rod of the flange in resisting horizontal loads on the wall. The stress and strain distribution of the bottom section of the shear wall in different stress states were analyzed according to the assumption of a plane section， and the moment curvature relationship of the section was obtained. The load on the top of the wall was calculated based on the bending moment， while the displacement of the top of the wall was calculated based on the curvature distribution and shear stiffness of the wall. A skeleton curve analysis method considering shear lag effect was established based on the characteristic points of cracking point， yield point， peak point， and limit point. Experimental results show that this method can accurately predict the mechanical performance of special-shaped steel trusses-composite shear wall.

Abstract:Eight axial compression tests on irregular octagonal hollow section columns were conducted， along with material tensile tests on the material extracted from different regions of tube. The experimental results indicate that the failure mode of irregular octagonal cold-formed thin-walled hollow steel stub columns is local buckling instability， and their load-bearing capacity cannot reach their yield strength. Finite element analysis was also performed on the steel tubes， validating the accuracy of the finite element model with experimental results， followed by parameter analysis to supplement the experimental data. The experimental data and finite element model results were used to evaluate the existing cross-section capacity formulas in Chinese， European， and American standards， as well as those reported in the existing literature. The evaluation results indicate that the existing formulas are not suitable for calculating the capacity of irregular octagonal thin-walled high-strength hollow steel tube stub columns. Therefore， a new formula was proposed. The test data and finite element model results were compared with the calculated results of the proposed formula， demonstrating that the proposed formula can accurately predict the capacity of the specimens.

Abstract:To address the inefficiency in manual identification of diverse anomalies in structural health monitoring （SHM） data， a method based on ensemble learning model is proposed to detect the abnormal data in super high-rise building SHM systems. By employing short-time Fourier transform， the time-frequency domain information containing the main structural vibrational modes is extracted and compressed， thus the feature extraction and high-fidelity compression of original data attained. Moreover， a Bagging ensemble strategy is introduced， and multiple training subsets are generated through bootstrap sampling， based on which each individual neural network model is trained independently. By aggregating the prediction results of multiple well-trained models， the precision of anomaly detection is enhanced. Furthermore， the proposed method is applied into the Shanghai Tower SHM system to validate the feasibility and reliability. The results indicate that the diagnosis accuracy reaches 98.8% by the proposed ensemble model-based abnormal data detection method， and high precision and strong robustness of the anomaly SHM data diagnosis are confirmed.

Abstract:Based on a unified fracture phase-field theory， a fluid-solid-phase multiphysics coupling numerical method is developed and applied to investigate the influence of in-situ stress and natural fractures on hydraulic fracturing and fracture morphology. Numerical simulation studies demonstrate that the fluid-solid-phase coupling numerical method can accurately predict fracture morphologies under tension， shear， and combined tension-shear hydraulic fracturing. The pressure head required to initiate fractures is positively correlated with the in-situ stress level， while the fracture morphology is significantly influenced by the lateral pressure coefficient. Natural fractures alter the distribution of pore pressure， which in turn affects the branching and intersection of hydraulic fractures， leading to diverse fracture morphologies.

Abstract:A self-designed low-pressure horizontal rotating drum experimental setup， combined with digital image processing technology， was used to capture various characteristic parameters of particle flow under different atmospheric pressure conditions， in order to study the impact of atmospheric pressure on the flow characteristics of particle materials. The results show that under low-pressure conditions， both the upper and lower repose angles of the particle avalanche flow decrease to varying degrees， reducing the stability of the particle accumulation in the drum and enhancing its flowability. For the entire horizontal drum particle flow collapse system， the lack of additional disturbances caused by air molecules （airflow） under low-pressure conditions diminishes external disturbances， leading to a more ordered and stable state of motion. The collapse angle and collapse duration， however， are not highly sensitive to changes in atmospheric pressure.

Abstract:To address the challenges posed by intense hydrodynamic interaction between sliding masses and ambient water in submarine landslide dynamics， this paper developed a coupled two-phase flow （incompressible smoothed particle hydrodynamics）ISPH model incorporating particle shifting and gradient correction techniques to enhance numerical stability. The model was validated against underwater landslide experiments and then applied to analyze the impact of terrain variations on landslide evolution. The results indicate that the landslide exhibit the strongest dynamic performance at the characteristic corner， with the sliding distance increasing by approximately 14% compared to other conditions. Steeper slope changes tend to trigger fluid uplift， promoting particle dispersion and turbidity current formation， thereby increasing the risk of damage to underwater infrastructure. Unlike dry conditions， submarine landslides display a two-stage dynamic behavior， where momentum exchange between particles and fluid sustains continued motion over flat regions， partially explaining long-runout phenomena.

Abstract:Based on the economic census data of Shanghai from 2008， 2013， and 2018， this paper systematically characterizes the spatial agglomeration of cultural and creative industries in the city， using continuous spatial units formed by enterprise locations as the analysis objects. The characterization considers multiple dimensions， including distribution patterns， agglomeration forms， hierarchical structures， and intensity types. The analysis reveals that the spatial agglomeration of cultural and creative industries in Shanghai has expanded from the urban center to the broader metropolitan area， transitioning from an “urban single-center” to a “metropolitan single-center” pattern and forming a “core-periphery” spatial differentiation. This agglomeration exhibits a multi-scale nested structure of “block-zone-urban district-city.” with the zone scale serving as a key level， showing trends of specialization and youthfulness.

Abstract:A multi-granularity defect recognition and safety assessment method is proposed for facility surfaces， using bridges as a representative example. The approach integrates a CAE_ViT network model with a sequential hierarchical coupled information framework （SHCIF） and a fuzzy comprehensive evaluation （FCE） system. First， the SHCIF and three corresponding granularity-specific recognition models are established， with datasets constructed and augmented for each granularity level. The SHCIF and cross-granularity classification strategy are designed to enhance defect severity recognition accuracy by leveraging information from both bridge component and defect type granularities. Second， transfer learning is applied to fine-tune the CAE_ViT pre-trained model for bridge defect detection， with classification performance further improved through cross-granularity decision-making. Finally， an analytic hierarchy process-entropy weight method （AHP-EWM） weighting system is incorporated into the FCE to achieve quantitative safety assessment of bridges based on apparent surface conditions， considering bridge locations， components， defect types， and severity levels. Experimental results show macro-average F1-scores of 94.1%， 81.6%， and 75.3% for the three granularity levels， respectively， with cross-granularity classification reaching 82% accuracy. A case study on bridge safety evaluation demonstrates the effectiveness， systematicness， and extensibility of the method.

Abstract:This paper proposes a demagnetization fault diagnosis strategy based on sliding mode information fusion for permanent magnet synchronous motors. First， a demagnetization fault model for interior permanent magnet synchronous motor is developed. Next， a motor demagnetization fault monitoring method based on the sliding window mean error is proposed， utilizing monitoring indicators constructed from current data. Finally， a demagnetization fault diagnosis method based on sliding mode information integration is introduced， integrating multiple sliding mode indicators to locate demagnetization faults. The proposed method is validated on a hardware-in-the-loop motor experimental platform. The result shows that this strategy can quickly and accurately diagnose demagnetization faults under different operating conditions.

Abstract:The Official Aviation Guide （OAG） data from 2013 to 2022 is utilized to construct a weighted International Aviation Network（IAN） with countries/regions as nodes and air traffic volume as edges. The Louvain algorithm is employed to uncover the community structure within the IAN， revealing its spatiotemporal evolution. Further， structural hubs are identified through within-community z-score and participation coefficient， while functional hubs are pinpointed using coreness. The findings indicate that the IAN displays small-world characteristics with a multi-module pattern， influenced by geographical proximity and geopolitical dynamics. Communities within the IAN exhibit heterogeneity， reflecting distinct regional aviation cooperation patterns. The community structure of the IAN is stable yet evolving， the international political events can lead to changes in community structure， presenting opportunities within changes. Structural hubs constitute approximately 5.0% of the IAN， and functional hubs account for roughly 7.6%.

Abstract:Building on existing research， this paper first analyzed the key interfacial properties of nanobubbles （NBs）， including surface tension， zeta potential， and surface adsorption. It then explored the stability theories of NBs， such as the dynamic equilibrium model， dense gas theory， and pollutant adsorption theory. Drawing on these properties and theories， it revealed the remediation mechanisms of NBs for typical groundwater pollutants. Furthermore， it comprehensively assessed the impact of factors like pH， temperature， and surfactants on the remediation efficiency and stability of NBs， and proposed regulation and optimization strategies.

Abstract:To explore the ecological evolution of Dongting Lake wetland， six representative Landsat images from before and after the completion of the Three Gorges Project are selected for classification using support vector machine （SVM）， maximum likelihood （ML）， and CART decision tree （DT） algorithms. The dynamic degree and transition matrix models are utilized to analyze the dynamic pattern evolution characteristics， leading to the construction of the pressure-state-response （PSR） model for ecological health assessment. The results show that the CART DT algorithm has a good applicability. Dongting Lake wetland landscape is characterized by complex dynamics， increased fragmentation， and enhanced heterogeneity. The water area increases from 680.59 km2 to 913.47 km2， but due to the water storage of the dam and socio-economic activities like vegetation planting， the area sharply decreased during 2001―2004. Sand mining in the lake area leads to a reduction in mudflat area at a rate of 8.8 km2/a. The sedge and reed areas increase and decrease alternately， and the woodland area significantly decreased after peaking in 2016. The ecological health index increases from 0.345 to 0.661 and then drops to 0.335， showing fluctuations between a “sub-healthy” state， a “very healthy” state， and back to a “sub-healthy state”. Ecological health is under dual pressure from socio-economic factors （weight 0.262） and natural changes （weight 0.205）， especially with recent extreme climate changes impacting wetland health by as much as 0.281. Considering the balance and coordination between socio-economic development and the natural environment， it is necessary to optimize water resource management and increase investment in wetland conservation.

Abstract:The effect of the number of steel fiber end hooks on the performance of steel fiber reinforced concrete （SFRC） and its mechanism were studied through single wire pull-out test， compressive strength test， and notched beam bending-tensile performance test. The results show that as the number of end hooks on the steel fiber increases， the ultimate bond strength between the steel fiber and the concrete matrix also increases. The number of end hooks has little effect on the compressive performance of SFRC， although steel fibers with a single end hook can slightly enhance the compressive strength. With more end hooks， the descending branch of the SFRC flexural-tensile curve becomes less steep， the curve becomes fuller， and the specimens can sustain higher flexural-tensile stresses. As cracks continue to propagate， steel fibers with two or three end hooks enable SFRC specimens to maintain relatively high residual flexural-tensile strength even after fracture and large deformation occur.