Search Results (895)

The Trepponti bridge in Comacchio (Italy) is a significant masonry landmark characterised by a complex geometry. Its structure comprises five irregularly connected segments, creating pronounced geometric discontinuities. Accurately modelling this configuration is challenging due to the highly complex mechanical behaviour of masonry. This study presents a robust computational strategy for the nonlinear structural assessment of such heritage bridges. The methodology integrates a parametric meshing environment (PoliBrick plugin) with nonlinear finite-element analysis in Straus7. An initial discretisation is generated through PoliBrick, undergoes geometric optimisation to produce an analysis-ready model. The bridge is homogeneously modelled and meshed through macro-blocks obeying a Mohr–Coulomb failure criterion. Material parameters are defined according to the LC1 knowledge level stipulated by the Italian structural code. Differential settlement scenarios are simulated by imposing controlled vertical displacements on individual and paired piers. This approach enables evaluation of structural displacement, stress distribution, and crack propagation. The analyses reveal a markedly asymmetric structural response, identifying two specific piers as critical vulnerable elements. The proposed framework demonstrates that parametric meshing effectively reconciles accurate geometric representation with computational efficiency. It offers a practical tool for guiding the conservation and safety evaluation of irregular vaulted masonry bridges. Full article

Fracturing is a key technology for developing deep coalbed methane, in which the wettability contrast between proppants and coal bridges significantly influences flowback efficiency. This study integrates in situ wettability measurements with phase-field simulations to analyze the mechanisms by which wettability contrast, proppant distribution, and capillary number affect microscale fracturing fluid flowback. The results indicate that: (1) Proppant spatial distribution governs displacement pathways, with the centralized aggregation pattern reducing residual saturation by 5.4% compared to the lateral aggregation pattern under the same capillary number; (2) under the centralized aggregation pattern, neutrally modified proppants lower residual saturation to 5.87%, representing a reduction of approximately 52.8% compared to the unmodified system; and (3) microscopic throat constraints and macroscopic symmetric placement work synergistically to alleviate retention heterogeneity and enhance flowback uniformity. Based on these findings, a dual-target optimization strategy of “neutral wettability modification of proppants + central symmetrical placement” is proposed, providing theoretical support for efficient flowback in deep coalbed methane wells. Full article

Dam displacement monitoring is crucial for assessing structural safety; however, conventional models often prioritize single-task prediction, leading to an inherent difficulty in balancing monitoring data quality with model performance. To bridge this gap, this study proposes a novel two-stage analytical framework that synergistically integrates an improved isolation forest (iForest) with a metaheuristic-optimized random forest (RF). The first stage focuses on data cleaning, where Kalman filtering is applied for denoising, and a newly developed Dynamic Threshold Isolation Forest (DTIF) algorithm is introduced to effectively isolate noise and outliers amidst complex environmental loads. In the second stage, the model’s predictive capability is enhanced by first employing the LASSO algorithm for feature importance analysis and optimal subset selection, followed by an Improved Reptile Search Algorithm (IRSA) for fine-tuning RF hyperparameters, thereby significantly boosting the model’s robustness. The IRSA incorporates several key improvements: Tent chaotic mapping during initialization to ensure population diversity, an adaptive parameter adjustment mechanism combined with a Lévy flight strategy in the encircling phase to dynamically balance global exploration and convergence, and the integration of elite opposition-based learning with Gaussian perturbation in the hunting phase to refine local exploitation. Validated against field data from a concrete hyperbolic arch dam, the proposed DTIF algorithm demonstrates superior anomaly detection accuracy across nine distinct outlier distribution scenarios. Moreover, for long-term displacement prediction tasks, the IRSA-RF model substantially outperforms traditional benchmark models in both predictive accuracy and generalization capability, providing a reliable early risk warning and decision-support tool for engineering practice. Full article

Inelastic displacement ratios are critical parameters in the seismic design of reinforced concrete (RC) box girder bridges. Existing approaches of displacement prediction, including the Displacement Coefficient Method and the Capacity Spectrum Method, typically rely on simplified single-degree-of-freedom (SDOF) models, which do not fully account for the complex and nonlinear behavior of multi-degree-of-freedom (MDOF) bridge systems. Moreover, the AASHTO Guide Specifications apply the equal displacement rule through the inelastic displacement modification factor R_d, which may underestimate displacement demands for short-period structures. This study evaluates the accuracy of the AASHTO R_d using nonlinear time history analyses of six RC box girder bridge models subjected to 28 recorded ground motions from California. Each ground motion included two orthogonal components applied in the longitudinal and transverse direction. Both elastic and inelastic displacement demands were determined in each direction, and inelastic displacement ratios (C_μ) were computed and compared with AASHTO predictions. A new predictive equation for C_μ was developed to capture response variability. While AASHTO R_d aligns with the average behavior, it fails to provide reliable estimate across the full range of seismic conditions. A comprehensive parametric study was conducted to examine the influence of column boundary condition, column height, superstructure deck width, number of spans, and damping ratio on C_μ. While the elastic and inelastic displacement decreases with an increase in damping ratio, the result shows that C_μ increases with higher damping ratios. Accordingly, a revised amplification factor was proposed to better represent the inelastic displacement demand in MDOF bridge systems. Full article

Hydrophilic interaction liquid chromatography (HILIC) is widely used for the analysis of glycans and oligosaccharides, yet the molecular basis of retention remains incompletely understood. In this study, we investigated dextran ladders labelled with 2-aminobenzamide (2-AB) and Rapifluor-MS™ (Waters, Milford, MA, USA) across a wide range of degrees of polymerization (DP 2–15), temperature conditions (10 °C to 70 °C), and gradient programs using a Acquity™ Premier Glycan BEH Amide column (Bridged Ethylene Hybrid, Waters, Milford, MA, USA). Van’t Hoff analysis revealed distinct enthalpic and entropic contributions to retention, allowing identification of a mechanistic transition from enthalpy-dominated docking interactions at low DP to entropy-driven dynamic adsorption at higher DP. This transition occurred reproducibly between DP 4–6, depending on the fluorescent label, while gradient steepness primarily influenced the location of the minimum enthalpy. Molecular dynamics simulations provided additional evidence, showing increased conformational flexibility and end-to-end distance variability for longer oligomers. This finding is consistent with entropy-dominated adsorption accompanied by displacement of structured interfacial water. Together, these results establish a molecular-level framework linking retention thermodynamics, conformational behavior, and solvation effects, thereby advancing our mechanistic understanding of glycan separation in HILIC. Full article

The blowout preventer (BOP) is the most important and the last line of safety defense in drilling engineering. Once a blowout occurs and the BOP fails, engineers will lose control of the entire wellbore pressure, and combustible fluids in the formation will continuously sprayed out, which can easily cause huge losses of life and property. At present, reliable and highly recognized emergency measures for BOP failure are lacking. Therefore, we propose a plugging method after the failure of the BOP that can maintain good control within the secondary well control. Numerical and experimental results indicate that using a small-to-medium displacement (1–2 m³/min) during the early stage of plugging and applying multiple plugging and killing cycles significantly improves plugging stability and killing efficiency. PEEK (polyether ether ketone) was selected as the bridging material for field plugging tests on full-scale blowout preventers, verifying its sealing effectiveness at pressures up to 80 MPa. Subsequently, the CFD–DEM was used to simulate the well killing process after plugging. This study mainly focused on the transportation of particles in a pipeline and the analysis of the process of well killing after plugging. The research results indicate that PEEK demonstrates sufficient pressure-bearing capacity under real blowout conditions. Also reveal that PEEK’s exceptional wear resistance and impact strength help maintain sealing stability during repeated particle–wall collisions, effectively reducing secondary erosion and prolonging the operational lifespan of temporary plugging structures. After undergoing six high-pressure tests of 70 MPa and two high-pressure tests of 80 MPa within 25 min, it remained intact. Both cylindrical and spherical particles can smoothly pass through the storage tank and double-bend pipeline at different displacements. Considering the retention effect of the plugging material, it is recommended to use 1–2 m³/min of pumping the plugging material at medium and small displacements in the early stage of plugging. During the process of plugging and killing, it is recommended to use alternating plugging and killing across multiple operations to prevent further blowouts to achieve the best plugging and killing effect. Full article

The paper presents the model, methodology and results of experimental research focused on identification of the wave form generated during the crossing of 30-ton and 60-ton vehicles on a ribbon-type pontoon bridge and the analysis of its influence on the characteristics of the maximum draught. A review of the literature revealed that ribbon-type pontoon bridges are subject to significant vertical deflection. This results from the need to generate sufficient buoyant force to balance the weight of crossing vehicles. The area of maximum draught occurs directly beneath the vehicle and moves along with it, generating a front wave—referred to as a bow wave—which propagates along the crossing and alters the local draught of individual pontoons. Due to the fact that pontoon bridges transfer loads through buoyancy force, a key issue in the process of their design is the precise knowledge of the formation of the volume of the droughted part. No information was found in any publication about the influence of the front wave on the draught form of a ribbon-type pontoon bridge. Their authors do not indicate that the analytical or simulation models they use reflect this phenomenon. Equally, the analysis of the methodologies and results of experimental studies in this area did not show that any attempts were made to identify the form of the front wave. The paper presents the results of measurements of vertical displacements of individual pontoon blocks of the crossing and the characteristics of the front wave occurring during the passing of 30- and 60-ton vehicles with speeds ranging from 7.4 to 30 km/h. Based on the obtained data, an attempt was made to identify the phenomenon of undulation of the surface of the water obstacle and its impact on the loads on the bridge structure. The results allow for identifying a significant front wave with a wavelength of 30–50 m, appearing clearly at speeds above 21 km/h. This wave substantially affects the draught measurement—at a speed of 25 km/h, the maximum draught increased by approximately 30%. Statistical analysis confirmed the significance of this effect (p < 0.05), indicating that wave formation must be considered for accurate determination of pontoon block draught. Furthermore, the mass of the vehicle had a strong influence on the wave and draught parameters—the 60-ton vehicle produced wave troughs and draught depths 55–65% greater than those of the 30-ton vehicle. Full article

This research investigates the seismic behavior of continuous-span base-isolated bridges integrated with fluid inerter damper (FID) through a linear analytical framework under recorded earthquake excitations. The resisting mechanism of the FID is modelled as a combination of inertial and viscous forces, which are functions of the relative acceleration and velocity between connected nodes. Linear time-history simulations and a series of parametric analyses are conducted to examine how variations in inertance, damping ratio, and installation location affect key seismic response parameters, including deck acceleration, bearing displacement, and substructure base shear. Comparative analyses with conventional viscous dampers and isolation alone establish the relative effectiveness of FID. Analysis indicates that FID effectively reduces deck accelerations through apparent mass amplification, suppresses bearing displacements via viscous damping, and redistributes seismic forces depending on placement strategies. An optimum inertance range is identified that minimizes accelerations without amplifying base shear, with abutment-level placement proving most effective for pier shear control, while intermediate placement provides balanced reductions. Overall, FID consistently outperforms viscous dampers and conventional isolation, underscoring their potential as an advanced inerter-based solution for both new bridge design and retrofit applications. Full article

Round-ended bridge piers are specifically utilized for high-speed railways in mountainous areas. However, the protective measures for such piers under debris flow remain limited, especially regarding the various components in the debris flow. This study introduces a reinforced concrete (RC) composite structure to improve the debris flow impact resistance of round-ended piers and investigates the impact from three different components of debris flow, including the bulk impact of slurry, collisions of large boulders, and abrasion of rock fragments. The results indicate the following: (1) The RC composite structure effectively mitigated the macroscopic damage from all types of debris flows. This structure significantly decreased gravel accumulation in the front of the pier body and reduced the size of scouring pits. These effects are superior to those of steel casing protection. (2) The RC composite structure significantly reduced the pier top displacement and pier body bending moments and optimized the pressure distribution on the pier body. The peak pressure reduction reached 95.7%, 88.4%, and 97.7% under three different debris flows. These effects were more pronounced than those under steel casing protection, for which the corresponding reductions were 18.2%, 70.9%, and 69.7%. (3) The RC composite structure effectively absorbed impact-induced vibrations and weakened shock effects on the upstream face, exhibiting superior capabilities compared with those of steel casing. The RC composite structure showed particularly outstanding performance in gravel-dominated debris flows. Ultimately, the RC composite structure could be an effective technique for enhancing the resistance of round-ended bridge piers against debris flows. Full article

In response to the issue of local damage to mountainous bridges easily caused by rockfall impacts, carbon fiber cloth and steel plate strengthening methods were adopted to deeply study the impact of the width of carbon fiber cloth and steel plates on the strengthening effect. This study investigates the strengthening effectiveness of Carbon Fiber-Reinforced Polymer (CFRP) wraps and steel jackets on circular bridge piers, utilizing the ABAQUS finite element method. The analysis focuses on the effects of varying load conditions and confinement widths ranging from 100 to 200 cm, with a specific case study of a bridge pier in Nanchuan District, Chongqing. The research results show that the width of carbon fiber cloth and steel plates has a significant impact on the bridge pier’s impact resistance and damage resistance. There exists an optimal strengthening width that maximizes the strengthening effect. The stress distribution and displacement changes under different load conditions are affected by the width of the steel plate; the wider the steel plate, the better the strengthening effect, but the effect is not strictly linear. A comprehensive analysis method integrating multi-directional stress and displacement data was developed, incorporating weighting factors based on structural safety relevance. For both strengthening methods, a set of fitted formulas for widths between 100 cm and 200 cm was derived. This study provides systematic insights and practical guidance for the design of impact-resistant strengthening systems for bridge piers. Full article

Friction pendulum bearings (FPBs) can effectively improve the seismic performance of bridges in class II sites. However, for class III and IV sites, using only FPBs under large earthquakes can easily cause significant displacement of the main beam, leading to beam collapse. In order to improve the seismic performance of railway simply supported beam bridges under poor geological conditions, this study proposes a new type of combined seismic isolation device, which extends the vibration period of the bridge through hyperbolic spherical bearings and provides energy dissipation through circular steel dampers. Based on the relevant design parameters of the steel damping and the bearing, their mechanical models are calculated and superimposed to obtain the mechanical model of the combined seismic isolation device, and the model is verified through experiments. Then, a bridge model using this device is established using OpenSees, and the effects of pier height, pier height difference, and far-field long-period seismic motion on pier bottom bending moment and support displacement under class III and IV sites are analyzed. The damage status and indicators of the combined device were provided, and the fragility of the device was analyzed. The results show that under design displacement (300 mm), the hysteresis curves of the combined seismic isolation device are with good consistency in mechanical properties in all directions and strong energy dissipation capacity, and the applicable pier height range of the device is determined under class III and IV sites. This study can provide a reference for the seismic isolation design and practical railway simply supported beam bridges. Full article

Based on the design concept of double-skin composite columns, this study proposes an enhanced configuration in which the inner steel tube is reinforced with fiber-reinforced polymer (FRP) stirrup-confined ultra-high-performance concrete (UHPC), leading to the development of FRP stirrup-confined UHPC–steel tube (FSCUS) hollow composite columns. Twelve glass FRP stirrup-confined UHPC–steel tube (GFSCUS) hollow composite column specimens were tested under axial compression. Analysis of load–displacement curves, and of load–strain curves of individual components, was performed. The effects of various parameters, including thickness and outer diameter of the steel tube, configuration and spacing of the GFRP stirrup, and steel fiber content of the UHPC, on the compressive behavior of the GFSCUS hollow composite columns were systematically investigated. The test results indicate that the influence of the thickness and outer diameter of the steel tube on the axial compression behavior is primarily governed by the effectiveness of the composite action between the steel tube and the confined concrete under axial compression load. The spacing and configuration of the FRP stirrup, conversely, determine the efficacy of the confinement provided to the concrete. The incorporation of steel fibers enhances both the peak load and the ductility due to their bridging effect. However, an excessive fiber content can restrict the lateral expansion of the concrete, thereby diminish the confining effect of the hoops and leading to a reduction in load-carrying capacity. Full article

Rapid assessment of seismic capacity for bridge pile group foundations under seismic loads is critical. This study employs the second-order central difference method to explore seismic capacity sensitivity and identify critical parameters. Subsequently, 1000 Latin hypercube samples were taken for these parameters, and 1000 analytical models were built. The overall displacement ductility is selected as the capacity indicator, and seismic capacity analysis is conducted on the models to obtain a capacity indicator. A BP model was constructed with the critical parameters as inputs and a capacity indicator as outputs to predict capacity values. Then, a regression function between capacity indicators and critical parameters is fitted to establish a capacity value assessment (CVA) model. Finally, capacity indicators are predicted using both the CVA model and the BP model, and the prediction results are compared. Results indicate that the critical parameters are tensile strength of reinforcing steel, cohesion of soil, cross-sectional area of pile, pile spacing, and longitudinal reinforcement ratio. The BP model can effectively predict the capacity indicators. The computational results of the CAV model show good agreement with the predictions from the BP model, demonstrating the reliability of the assessment model. This study provides a novel approach for disaster prediction of bridge pile group foundations. Full article

Steep rock slopes in mountainous regions present the coupled challenges of mechanical instability and ecological degradation, yet existing protection methods often focus on structural reinforcement alone, neglecting ecological recovery. To bridge this gap, this study develops an integrated ecological cement–soil (ECS) slope protection system that couples a porous cement–soil layer, galvanized mesh, and anchors to achieve simultaneous mechanical stabilization and vegetation restoration. Field experiments and finite-element simulations were conducted to evaluate the deformation control, strength development, and stress transfer mechanism of the ECS system. Results demonstrate that the ECS layer effectively limited surface displacement (<2 mm) while maintaining sufficient porosity (0.3–0.5 MPa strength) to support plant growth. This work provides a generalizable framework for eco-friendly slope protection, offering new insights for the sustainable rehabilitation of steep rocky terrains beyond the studied project site. Full article

The construction of long-span continuous steel truss rail-cum-road bridges for high-speed railways presents significant challenges, primarily due to structural complexity, stringent deformation tolerances, and intricate construction sequences. This paper presents a comprehensive construction control methodology developed and implemented for such bridges. Using a real-world bridge project in China as a case study, the methodology integrates mechanical analysis of key construction stages, deformation prediction, real-time monitoring, and adjustment techniques. Furthermore, the application of machine learning (ML) for camber prediction is explored. Key findings indicate that the longitudinal displacement (X-direction) of the top chord at the upper-deck closure segment is highly sensitive to temperature variations, with a differential of about 10–12 mm observed under a 15 °C temperature change. Consequently, closure welding is recommended near the design reference temperature, with field measurements guiding final fit-up adjustments. A comparative analysis between ML predictions and theoretical methods for member elongation revealed that the Extra Trees (ET) model and K-Nearest Neighbors (KNN) model achieved excellent accuracy, with errors within 2 mm, demonstrating the feasibility of ML-based camber setting. The proposed integrated approach, combining finite element analysis, real-time monitoring, and detailed sensitivity analysis of closure accuracy, proves effective in ensuring structural safety and meeting precise alignment requirements, particularly for high-speed railway track. The findings offer valuable insights for the construction control of similar long-span steel truss rail-cum-road bridges. Full article