Objective: To explore the clinical efficacy of shoulder arthroscopic one-knot-two-wire suture bridge technique in the treatment of small and medium-sized rotator cuff tears. Methods: The clinical data of 22 patients w...Objective: To explore the clinical efficacy of shoulder arthroscopic one-knot-two-wire suture bridge technique in the treatment of small and medium-sized rotator cuff tears. Methods: The clinical data of 22 patients with small and medium-sized rotator cuff injuries treated with the one-knot-two-wire suture bridge technique from February 2022 to June 2023 in the Department of Orthopaedics of Jingzhou Hospital Affiliated to Yangtze University were retrospectively analysed, among which 14 cases were male and 8 cases were female;the age ranged from 35 to 68 years old, with an average of (50.86 ± 10.80) years old. All cases underwent an MRI examination of the shoulder joint to understand the type and degree of injury. The duration of the disease ranged from 120 to 166 d, with a mean of (141.23 ± 13.46) d. The evaluation of the operation time, intraoperative bleeding, visual analogue scale (VAS) of pain, Constant-Murley score and Sugaya grading of shoulder MRI were performed at the last follow-up. Results: All 22 patients were followed up for 12 - 18 months, with a mean of (14.68 ± 1.89 d). The operation time was 38 - 58 min, mean (48.18 ± 5.92) min;intraoperative bleeding was 5 - 15 mL, mean (10.00 ± 3.45) mL. All patients achieved normal healing without re-tear, vascular and nerve injury, incision infection, anchor nail loosening and dislodgement and other complications. At the last follow-up, both shoulders were normal in shape and symmetrical on both sides. The VAS score was 0 - 1.2 points, with an average of 0.61 ± 0.42 points, and the Constant-Murley score was 70 - 98 points, with an average of 86.09 ± 8.56 points. The Sugaya classification of MRI examination was 17 cases of grade I, 4 cases of grade II, and 1 case of grade III. Conclusion: One-knot-two-wire suture bridge technique is used for the treatment of small and medium-sized rotator cuff tears with short operative time, low bleeding, and good clinical outcome.展开更多
A method combining finite difference method(FDM)and k-means clustering algorithm which can determine the threshold of rock bridge generation is proposed.Jointed slope models with different joint coalescence coefficien...A method combining finite difference method(FDM)and k-means clustering algorithm which can determine the threshold of rock bridge generation is proposed.Jointed slope models with different joint coalescence coefficients(k)are constructed based on FDM.The rock bridge area was divided through k-means algorithm and the optimal number of clusters was determined by sum of squared errors(SSE)and elbow method.The influence of maximum principal stress and stress change rate as clustering indexes on the clustering results of rock bridges was compared by using Euclidean distance.The results show that using stress change rate as clustering index is more effective.When the joint coalescence coefficient is less than 0.6,there is no significant stress concentration in the middle area of adjacent joints,that is,no generation of rock bridge.In addition,the range of rock bridge is affected by the coalescence coefficient(k),the relative position of joints and the parameters of weak interlayer.展开更多
The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which ...The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which limits the speed of electromagnetic transient(EMT)simulations.To overcome these limitations,a novel EMT equivalent model based on a generalized branch-cutting method is proposed to improve the simulation efficiency of the DAB model.The DAB topology is first decomposed into two subnetworks through branch-cutting and node-tearing methods without the introduction of a one-time-step delay.Sub-sequently,the internal nodes of each sub-network are eliminated through network simplification,and the equivalent circuit for the port cascade module is derived.The model is then validated through simulations across various operating conditions.The results demonstrate that the model avoids the loss of accuracy associated with one-time-step delay,the relative error across different conditions remains below 1%,and the simulation acceleration ratios improve as the number of modules increases.展开更多
This study introduces an innovative“Big Model”strategy to enhance Bridge Structural Health Monitoring(SHM)using a Convolutional Neural Network(CNN),time-frequency analysis,and fine element analysis.Leveraging ensemb...This study introduces an innovative“Big Model”strategy to enhance Bridge Structural Health Monitoring(SHM)using a Convolutional Neural Network(CNN),time-frequency analysis,and fine element analysis.Leveraging ensemble methods,collaborative learning,and distributed computing,the approach effectively manages the complexity and scale of large-scale bridge data.The CNN employs transfer learning,fine-tuning,and continuous monitoring to optimize models for adaptive and accurate structural health assessments,focusing on extracting meaningful features through time-frequency analysis.By integrating Finite Element Analysis,time-frequency analysis,and CNNs,the strategy provides a comprehensive understanding of bridge health.Utilizing diverse sensor data,sophisticated feature extraction,and advanced CNN architecture,the model is optimized through rigorous preprocessing and hyperparameter tuning.This approach significantly enhances the ability to make accurate predictions,monitor structural health,and support proactive maintenance practices,thereby ensuring the safety and longevity of critical infrastructure.展开更多
Bridge pier failures from granular flow impacts are common.Installing defense piles upstream is an effective mitigation strategy,yet their protective mechanisms and standardized design guidelines are unclear.This stud...Bridge pier failures from granular flow impacts are common.Installing defense piles upstream is an effective mitigation strategy,yet their protective mechanisms and standardized design guidelines are unclear.This study employed 3D discrete element method to analyze the influence of defense pile size and placement on its performance across 219 scenarios,providing a detailed examination of their protective mechanisms.Results show that optimizing these factors can reduce the maximum impact force on bridge piers by up to 94%.In terms of size,a critical height threshold is identified,beyond which increasing pile height does not enhance protection.This threshold depends on the movement height of granular particles at the slope base.Protection effectiveness varies with pile size:when H≤0.05 h(H is the height of defense piles,h is the height of bridge),protection marginally improves with increasing height and diameter;for 0.05 h<H<0.15 h,protection strongly correlates with both parameters;for H≥0.15 h,diameter becomes the dominant factor.In terms of placement,an optimal longitudinal distance exists between the defense pile and the bridge pier.The larger the diameter,the greater the optimal longitudinal distance.However,the transverse distance is inversely related to protection effectiveness.Mechanistic analysis shows that defense piles are more effective at redirecting particles to prevent direct collisions with the pier(contributing 100%impact energy reduction before the non-dimensional travel time t*=7.01 and 63%–100%afterward)than at reducing particle velocity.This study provides insights into the protective mechanisms of defense piles and informs strategies for optimizing bridge pier protection in granular flow-prone regions.展开更多
Probabilistic assessment of seismic performance(SPPA)is a crucial aspect of evaluating the seismic behavior of structures.For complex bridges with inherent uncertainties,conducting precise and efficient seismic reliab...Probabilistic assessment of seismic performance(SPPA)is a crucial aspect of evaluating the seismic behavior of structures.For complex bridges with inherent uncertainties,conducting precise and efficient seismic reliability analysis remains a significant challenge.To address this issue,the current study introduces a sample-unequal weight fractional moment assessment method,which is based on an improved correlation-reduced Latin hypercube sampling(ICLHS)technique.This method integrates the benefits of important sampling techniques with interpolator quadrature formulas to enhance the accuracy of estimating the extreme value distribution(EVD)for the seismic response of complex nonlinear structures subjected to non-stationary ground motions.Additionally,the core theoretical approaches employed in seismic reliability analysis(SRA)are elaborated,such as dimension reduction for simulating non-stationary random ground motions and a fractional-maximum entropy single-loop solution strategy.The effectiveness of this proposed method is validated through a three-story nonlinear shear frame structure.Furthermore,a comprehensive reliability analysis of a real-world long-span,single-pylon suspension bridge is conducted using the developed theoretical framework within the OpenSees platform,leading to key insights and conclusions.展开更多
This study conducted shear resistance tests on steel-UHPC composite beams,focusing on structural stiffness changes during the test process,strain analysis of UHPC panels,internal reinforcement bars,steel structures,an...This study conducted shear resistance tests on steel-UHPC composite beams,focusing on structural stiffness changes during the test process,strain analysis of UHPC panels,internal reinforcement bars,steel structures,and shear connectors,as well as the failure processes and modes of UHPC panels and the structure.Through theoretical analysis,the contribution of UHPC panels to the overall vertical shear resistance capability was clarified.A shear load-bearing capacity calculation method was established,thereby considering the combined beam shear bearing capacity calculation formula of the UHPC panel and the steel beam web.展开更多
The fatigue of heavy-haul railway bridges is considered a key concern due to high stress levels and cyclic loading.The evaluation of fatigue reliability is required to include factor correlations.A major challenge is ...The fatigue of heavy-haul railway bridges is considered a key concern due to high stress levels and cyclic loading.The evaluation of fatigue reliability is required to include factor correlations.A major challenge is presented by the construction of the cumulative distribution function(CDF)and the description of correlations between random variables.In this study,the copula function is used to analyze the fatigue failure probability of the Shuohuang heavy-haul railway bridge.A C-vine copula(CVC)-based joint probability density function(JPDF)is derived with eight correlated parameters.To enhance efficiency in small failure probability calculations,the subset simulation and most probable point(MPP)Monte Carlo importance sampling are introduced based on the Rosenblatt transform and C-vine model.Comparisons with traditional Monte Carlo methods confirm that high accuracy and efficiency are achieved.The results show that when parameter correlations are ignored,failure probability is underestimated,increasing safety risks in bridge assessments.展开更多
Cable-stayed bridges have been widely used in high-speed railway infrastructure.The accurate determination of cable’s representative temperatures is vital during the intricate processes of design,construction,and mai...Cable-stayed bridges have been widely used in high-speed railway infrastructure.The accurate determination of cable’s representative temperatures is vital during the intricate processes of design,construction,and maintenance of cable-stayed bridges.However,the representative temperatures of stayed cables are not specified in the existing design codes.To address this issue,this study investigates the distribution of the cable temperature and determinates its representative temperature.First,an experimental investigation,spanning over a period of one year,was carried out near the bridge site to obtain the temperature data.According to the statistical analysis of the measured data,it reveals that the temperature distribution is generally uniform along the cable cross-section without significant temperature gradient.Then,based on the limited data,the Monte Carlo,the gradient boosted regression trees(GBRT),and univariate linear regression(ULR)methods are employed to predict the cable’s representative temperature throughout the service life.These methods effectively overcome the limitations of insufficient monitoring data and accurately predict the representative temperature of the cables.However,each method has its own advantages and limitations in terms of applicability and accuracy.A comprehensive evaluation of the performance of these methods is conducted,and practical recommendations are provided for their application.The proposed methods and representative temperatures provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.展开更多
A multi-level evaluation model for the superstructure of a damaged prestressed concrete girder or beam bridge is established, and the evaluation indices of the model as well as the rating standards are defined. A norm...A multi-level evaluation model for the superstructure of a damaged prestressed concrete girder or beam bridge is established, and the evaluation indices of the model as well as the rating standards are defined. A normal relative function about the evaluation indices of each element is developed to calculate the relative degree, and for each element there are no sub-level elements. When evaluating the elements in the sub-item level or the index level of the model, the weights of elements pertain to one adopted element, taking into account their degrees of deterioration. Since the relative degrees and structure evaluation scales on the damage conditions are applied to characterize the superstructure of damaged prestressed concrete girder bridges, this method can evaluate the prestressed structure in detail, and the evaluation results agree with the Code for Maintenance of Highway Bridges and Culvers （JTG Hll--2004 ）. Finally, a bridge in Jilin province is taken as an example, using the method developed to evaluate its damage conditions, which gives an effective way for bridge engineering.展开更多
Combined with current specifications and stress characteristics of concrete filled steel tubular （CFST） arch bridges, the determination principle of safe-middle-failure threestage mode is given. Accordingly, damage ...Combined with current specifications and stress characteristics of concrete filled steel tubular （CFST） arch bridges, the determination principle of safe-middle-failure threestage mode is given. Accordingly, damage probability and failure probability and the corresponding reliability indices are calculated; a direct relationship between reliability indices and three-stage working status is made. Based on the three-stage working mode, a combined FNM （finite element-neural network- Monte-Carlo simulation） method is put forward to estimate the reliability of existing bridges. According to time-dependent reliability theory, subsequent service time is divided into several stages; minimum samples required by the Monte-Carlo method are generated by random sampling; training samples are calculated by the finite element method, and the training samples are extended by the neural network; failure probability and damage probability are calculated by the Monte-Carlo method. Thus, time dependent reliability indices are obtained, and the working status is judged. A case study is investigated to estimate the reliability of an actual bridge by the FNM method. The bridge is a CFST arch bridge with an 83.6 m span and it has been in operation for 10 years. According to analysis results, in the tenth year, the example bridge is still in safe status. This conclusion is consistent with the facts, which proves the feasibility of the FNM method for estimating the reliability of existing bridges.展开更多
Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress grad...Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.展开更多
Cantilever casting concrete arch bridge using form traveller has a broad application prospect.However,it is difficult to obtain reasonable initial cable force in construction stage.In this study,stress balance and inf...Cantilever casting concrete arch bridge using form traveller has a broad application prospect.However,it is difficult to obtain reasonable initial cable force in construction stage.In this study,stress balance and influence matrix methods were developed to determine the initial cable force of cantilever casting concrete arch bridge.The stress balance equation and influence matrix of arch rib critical section were established,and the buckle cable force range was determined by the allowable stress of arch rib critical section.Then a group of buckle cable forces were selected and substituted into the stress balance equation,and the reasonable initial buckle cable force was determined through iteration.Based on the principle of force balance,the initial anchor cable force was determined.In an engineering application example,it is shown that the stress balance and influence matrix methods for the determination of initial cable force are feasible and reliable.The initial cable forces of arch rib segments only need to be adjusted once in the corresponding construction process,which improves the working efficiency and reduces the construction risk.It is found that the methods have great advantages for determining initial cable force in cantilever casting construction process of concrete arch bridge.展开更多
Based on reasonable assumptions that simplified the calculational model,a simple and practical method was proposed to calculate the post-construction settlement of high-speed railway bridge pile foundation by using th...Based on reasonable assumptions that simplified the calculational model,a simple and practical method was proposed to calculate the post-construction settlement of high-speed railway bridge pile foundation by using the Mesri creep model to describe the soil characteristics and the Mindlin-Geddes method considering pile diameter to calculate the vertical additional stress of pile bottom.A program named CPPS was designed for this method to calculate the post-construction settlement of a high-speed railway bridge pile foundation.The result indicates that the post-construction settlement in 100 years meets the requirements of the engineering specifications,and in the first two decades,the post-construction settlement is about 80% of its total settlement,while the settlement in the rest eighty years tends to be stable.Compared with the measured settlement after laying railway tracks,the calculational result is closed to that of the measured,and the results are conservative with a high computational accuracy.It is noted that the method can be used to calculate the post-construction settlement for the preliminary design of high-speed railway bridge pile foundation.展开更多
This article explores the fundamentals of small-radius curved ramp bridges.It covers the selection of box girder spans,support methods,and forms,along with design optimization techniques for this type of bridge struct...This article explores the fundamentals of small-radius curved ramp bridges.It covers the selection of box girder spans,support methods,and forms,along with design optimization techniques for this type of bridge structure.The purpose of this paper is to provide robust support for enhancing the design quality of these bridges and ensuring their efficacy in real-world applications.展开更多
Mechanical behavior of concrete slab of large-span through tied-arch composite bridge was investigated by finite element analysis (FEA). Improved methods to decrease concrete stresses were discussed based on compariso...Mechanical behavior of concrete slab of large-span through tied-arch composite bridge was investigated by finite element analysis (FEA). Improved methods to decrease concrete stresses were discussed based on comparisons of different deck schemes, construction sequences and measures, and ratios of reinforcement. The results show that the mechanical behavior of concrete slab gets worse with the increase of composite regions between steel beams and concrete slab. The deck scheme with the minimum composite region is recommended on condition that both strength and stiffness of the bridge meet design demands under service loads. Adopting in-situ-place construction method, concrete is suggested to be cast after removing the full-supported frameworks under the bridge. Thus, the axial tensile force of concrete slab caused by the first stage dead load is eliminated. Preloading the bridge before concrete casting and removing the load after the concrete reaching its design strength, the stresses of concrete slab caused by the second stage dead load and live load are further reduced or even eliminated. At last, with a high ratio of reinforcement more than 3%, the concrete stresses decrease obviously.展开更多
Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure...Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.展开更多
The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the sy...The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the system's vibration characteristics could be established by its simplified dynamic analysis model,making it convenient for providing a reference to the optimization of design and safety analysis.A double-mass six-degree-of-freedom model for curved girder bridges with isolation bearings installed at the top of the bridge piers is built and a simplified analysis method for the vibration characteristics of the system is provided.Combined with the Matlab programming,the influences of radius of curvature,central angle,bridge deck width and damping ratio of the isolation layer and circular frequency of the isolation layer of isolated curved girder bridges on the pseudo-undamped natural circular frequency(called pseudo-frequency for short)and system damping ratio are systematically analyzed,and the sensitivity of vibration characteristics of isolated curved girder bridges is studied.The results show that the vibration characteristics of isolated curved girder bridges can be reflected well with this simplified model and calculation method.The pseudo-frequency of curved girder and system damping ratios increases with the increase of the isolation layer.The third-order vibration characteristic is more sensitive to the parameters of a curved girder,and the first-order vibration characteristic is sensitive to both central angle and radius of curvature to some extent while insensitive to the width of the bridge deck.Furthermore,the second-order vibration characteristic is not sensitive to the parameters of a curved girder.展开更多
文摘Objective: To explore the clinical efficacy of shoulder arthroscopic one-knot-two-wire suture bridge technique in the treatment of small and medium-sized rotator cuff tears. Methods: The clinical data of 22 patients with small and medium-sized rotator cuff injuries treated with the one-knot-two-wire suture bridge technique from February 2022 to June 2023 in the Department of Orthopaedics of Jingzhou Hospital Affiliated to Yangtze University were retrospectively analysed, among which 14 cases were male and 8 cases were female;the age ranged from 35 to 68 years old, with an average of (50.86 ± 10.80) years old. All cases underwent an MRI examination of the shoulder joint to understand the type and degree of injury. The duration of the disease ranged from 120 to 166 d, with a mean of (141.23 ± 13.46) d. The evaluation of the operation time, intraoperative bleeding, visual analogue scale (VAS) of pain, Constant-Murley score and Sugaya grading of shoulder MRI were performed at the last follow-up. Results: All 22 patients were followed up for 12 - 18 months, with a mean of (14.68 ± 1.89 d). The operation time was 38 - 58 min, mean (48.18 ± 5.92) min;intraoperative bleeding was 5 - 15 mL, mean (10.00 ± 3.45) mL. All patients achieved normal healing without re-tear, vascular and nerve injury, incision infection, anchor nail loosening and dislodgement and other complications. At the last follow-up, both shoulders were normal in shape and symmetrical on both sides. The VAS score was 0 - 1.2 points, with an average of 0.61 ± 0.42 points, and the Constant-Murley score was 70 - 98 points, with an average of 86.09 ± 8.56 points. The Sugaya classification of MRI examination was 17 cases of grade I, 4 cases of grade II, and 1 case of grade III. Conclusion: One-knot-two-wire suture bridge technique is used for the treatment of small and medium-sized rotator cuff tears with short operative time, low bleeding, and good clinical outcome.
基金supported by the National Natural Science Foundation of China(No.42277175)Guangxi Emergency Management Department 2024 Innovation and Technology Research Project,China(No.2024GXYJ006)+2 种基金Hunan Provincial Department of Natural Resources Geological Exploration Project,China(No.2023ZRBSHZ056)The First National Natural Disaster Comprehensive Risk Survey in Hunan Province,China(No.2022-70)Guizhou Provincial Major Scientific and Technological Program,China(No.2023-425).
文摘A method combining finite difference method(FDM)and k-means clustering algorithm which can determine the threshold of rock bridge generation is proposed.Jointed slope models with different joint coalescence coefficients(k)are constructed based on FDM.The rock bridge area was divided through k-means algorithm and the optimal number of clusters was determined by sum of squared errors(SSE)and elbow method.The influence of maximum principal stress and stress change rate as clustering indexes on the clustering results of rock bridges was compared by using Euclidean distance.The results show that using stress change rate as clustering index is more effective.When the joint coalescence coefficient is less than 0.6,there is no significant stress concentration in the middle area of adjacent joints,that is,no generation of rock bridge.In addition,the range of rock bridge is affected by the coalescence coefficient(k),the relative position of joints and the parameters of weak interlayer.
基金The Technology Project of State Grid Corporation of China Headquarters(No.5400-202318547A-3-2-ZN).
文摘The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which limits the speed of electromagnetic transient(EMT)simulations.To overcome these limitations,a novel EMT equivalent model based on a generalized branch-cutting method is proposed to improve the simulation efficiency of the DAB model.The DAB topology is first decomposed into two subnetworks through branch-cutting and node-tearing methods without the introduction of a one-time-step delay.Sub-sequently,the internal nodes of each sub-network are eliminated through network simplification,and the equivalent circuit for the port cascade module is derived.The model is then validated through simulations across various operating conditions.The results demonstrate that the model avoids the loss of accuracy associated with one-time-step delay,the relative error across different conditions remains below 1%,and the simulation acceleration ratios improve as the number of modules increases.
文摘This study introduces an innovative“Big Model”strategy to enhance Bridge Structural Health Monitoring(SHM)using a Convolutional Neural Network(CNN),time-frequency analysis,and fine element analysis.Leveraging ensemble methods,collaborative learning,and distributed computing,the approach effectively manages the complexity and scale of large-scale bridge data.The CNN employs transfer learning,fine-tuning,and continuous monitoring to optimize models for adaptive and accurate structural health assessments,focusing on extracting meaningful features through time-frequency analysis.By integrating Finite Element Analysis,time-frequency analysis,and CNNs,the strategy provides a comprehensive understanding of bridge health.Utilizing diverse sensor data,sophisticated feature extraction,and advanced CNN architecture,the model is optimized through rigorous preprocessing and hyperparameter tuning.This approach significantly enhances the ability to make accurate predictions,monitor structural health,and support proactive maintenance practices,thereby ensuring the safety and longevity of critical infrastructure.
基金supported by the National Natural Science Foundation of China(Grant numbers 41977233)。
文摘Bridge pier failures from granular flow impacts are common.Installing defense piles upstream is an effective mitigation strategy,yet their protective mechanisms and standardized design guidelines are unclear.This study employed 3D discrete element method to analyze the influence of defense pile size and placement on its performance across 219 scenarios,providing a detailed examination of their protective mechanisms.Results show that optimizing these factors can reduce the maximum impact force on bridge piers by up to 94%.In terms of size,a critical height threshold is identified,beyond which increasing pile height does not enhance protection.This threshold depends on the movement height of granular particles at the slope base.Protection effectiveness varies with pile size:when H≤0.05 h(H is the height of defense piles,h is the height of bridge),protection marginally improves with increasing height and diameter;for 0.05 h<H<0.15 h,protection strongly correlates with both parameters;for H≥0.15 h,diameter becomes the dominant factor.In terms of placement,an optimal longitudinal distance exists between the defense pile and the bridge pier.The larger the diameter,the greater the optimal longitudinal distance.However,the transverse distance is inversely related to protection effectiveness.Mechanistic analysis shows that defense piles are more effective at redirecting particles to prevent direct collisions with the pier(contributing 100%impact energy reduction before the non-dimensional travel time t*=7.01 and 63%–100%afterward)than at reducing particle velocity.This study provides insights into the protective mechanisms of defense piles and informs strategies for optimizing bridge pier protection in granular flow-prone regions.
基金Sichuan Science and Technology Program under Grant No.2024NSFSC0932the National Natural Science Foundation of China under Grant No.52008047。
文摘Probabilistic assessment of seismic performance(SPPA)is a crucial aspect of evaluating the seismic behavior of structures.For complex bridges with inherent uncertainties,conducting precise and efficient seismic reliability analysis remains a significant challenge.To address this issue,the current study introduces a sample-unequal weight fractional moment assessment method,which is based on an improved correlation-reduced Latin hypercube sampling(ICLHS)technique.This method integrates the benefits of important sampling techniques with interpolator quadrature formulas to enhance the accuracy of estimating the extreme value distribution(EVD)for the seismic response of complex nonlinear structures subjected to non-stationary ground motions.Additionally,the core theoretical approaches employed in seismic reliability analysis(SRA)are elaborated,such as dimension reduction for simulating non-stationary random ground motions and a fractional-maximum entropy single-loop solution strategy.The effectiveness of this proposed method is validated through a three-story nonlinear shear frame structure.Furthermore,a comprehensive reliability analysis of a real-world long-span,single-pylon suspension bridge is conducted using the developed theoretical framework within the OpenSees platform,leading to key insights and conclusions.
文摘This study conducted shear resistance tests on steel-UHPC composite beams,focusing on structural stiffness changes during the test process,strain analysis of UHPC panels,internal reinforcement bars,steel structures,and shear connectors,as well as the failure processes and modes of UHPC panels and the structure.Through theoretical analysis,the contribution of UHPC panels to the overall vertical shear resistance capability was clarified.A shear load-bearing capacity calculation method was established,thereby considering the combined beam shear bearing capacity calculation formula of the UHPC panel and the steel beam web.
基金Project supported by the National Natural Science Foundation of China(No.52278180)。
文摘The fatigue of heavy-haul railway bridges is considered a key concern due to high stress levels and cyclic loading.The evaluation of fatigue reliability is required to include factor correlations.A major challenge is presented by the construction of the cumulative distribution function(CDF)and the description of correlations between random variables.In this study,the copula function is used to analyze the fatigue failure probability of the Shuohuang heavy-haul railway bridge.A C-vine copula(CVC)-based joint probability density function(JPDF)is derived with eight correlated parameters.To enhance efficiency in small failure probability calculations,the subset simulation and most probable point(MPP)Monte Carlo importance sampling are introduced based on the Rosenblatt transform and C-vine model.Comparisons with traditional Monte Carlo methods confirm that high accuracy and efficiency are achieved.The results show that when parameter correlations are ignored,failure probability is underestimated,increasing safety risks in bridge assessments.
基金Project(2017G006-N)supported by the Project of Science and Technology Research and Development Program of China Railway Corporation。
文摘Cable-stayed bridges have been widely used in high-speed railway infrastructure.The accurate determination of cable’s representative temperatures is vital during the intricate processes of design,construction,and maintenance of cable-stayed bridges.However,the representative temperatures of stayed cables are not specified in the existing design codes.To address this issue,this study investigates the distribution of the cable temperature and determinates its representative temperature.First,an experimental investigation,spanning over a period of one year,was carried out near the bridge site to obtain the temperature data.According to the statistical analysis of the measured data,it reveals that the temperature distribution is generally uniform along the cable cross-section without significant temperature gradient.Then,based on the limited data,the Monte Carlo,the gradient boosted regression trees(GBRT),and univariate linear regression(ULR)methods are employed to predict the cable’s representative temperature throughout the service life.These methods effectively overcome the limitations of insufficient monitoring data and accurately predict the representative temperature of the cables.However,each method has its own advantages and limitations in terms of applicability and accuracy.A comprehensive evaluation of the performance of these methods is conducted,and practical recommendations are provided for their application.The proposed methods and representative temperatures provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.
文摘A multi-level evaluation model for the superstructure of a damaged prestressed concrete girder or beam bridge is established, and the evaluation indices of the model as well as the rating standards are defined. A normal relative function about the evaluation indices of each element is developed to calculate the relative degree, and for each element there are no sub-level elements. When evaluating the elements in the sub-item level or the index level of the model, the weights of elements pertain to one adopted element, taking into account their degrees of deterioration. Since the relative degrees and structure evaluation scales on the damage conditions are applied to characterize the superstructure of damaged prestressed concrete girder bridges, this method can evaluate the prestressed structure in detail, and the evaluation results agree with the Code for Maintenance of Highway Bridges and Culvers （JTG Hll--2004 ）. Finally, a bridge in Jilin province is taken as an example, using the method developed to evaluate its damage conditions, which gives an effective way for bridge engineering.
基金The National Natural Science Foundation of China(No.10672060)
文摘Combined with current specifications and stress characteristics of concrete filled steel tubular （CFST） arch bridges, the determination principle of safe-middle-failure threestage mode is given. Accordingly, damage probability and failure probability and the corresponding reliability indices are calculated; a direct relationship between reliability indices and three-stage working status is made. Based on the three-stage working mode, a combined FNM （finite element-neural network- Monte-Carlo simulation） method is put forward to estimate the reliability of existing bridges. According to time-dependent reliability theory, subsequent service time is divided into several stages; minimum samples required by the Monte-Carlo method are generated by random sampling; training samples are calculated by the finite element method, and the training samples are extended by the neural network; failure probability and damage probability are calculated by the Monte-Carlo method. Thus, time dependent reliability indices are obtained, and the working status is judged. A case study is investigated to estimate the reliability of an actual bridge by the FNM method. The bridge is a CFST arch bridge with an 83.6 m span and it has been in operation for 10 years. According to analysis results, in the tenth year, the example bridge is still in safe status. This conclusion is consistent with the facts, which proves the feasibility of the FNM method for estimating the reliability of existing bridges.
基金Projects(51278166,51478163)supported by the National Natural Science Foundation of ChinaProject(2015B17414)supported by the Fundamental Research Funds for the Central Universities,China
文摘Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.
基金Projects(51478049,51778068)supported by the National Natural Science Foundation of ChinaProject(14JJ2075,2019JJ40301)supported by the Hunan Natural Science Foundation of China+1 种基金Project(17A010)supported by the Scientific Research Fund of Hunan Provincial Education Department of ChinaProject(2017GK4034)supported by the Major Technological Achievements Transformation Program of Hunan Strategic Emerging Industries of China
文摘Cantilever casting concrete arch bridge using form traveller has a broad application prospect.However,it is difficult to obtain reasonable initial cable force in construction stage.In this study,stress balance and influence matrix methods were developed to determine the initial cable force of cantilever casting concrete arch bridge.The stress balance equation and influence matrix of arch rib critical section were established,and the buckle cable force range was determined by the allowable stress of arch rib critical section.Then a group of buckle cable forces were selected and substituted into the stress balance equation,and the reasonable initial buckle cable force was determined through iteration.Based on the principle of force balance,the initial anchor cable force was determined.In an engineering application example,it is shown that the stress balance and influence matrix methods for the determination of initial cable force are feasible and reliable.The initial cable forces of arch rib segments only need to be adjusted once in the corresponding construction process,which improves the working efficiency and reduces the construction risk.It is found that the methods have great advantages for determining initial cable force in cantilever casting construction process of concrete arch bridge.
基金Projects(2009G008-B,2010G018-E-3) supported by Key Projects of China Railway Ministry Science and Technology Research and Development ProgramProject(CX2013B076) supported by Hunan Provincial Innovation Foundation For Postgraduate,China
文摘Based on reasonable assumptions that simplified the calculational model,a simple and practical method was proposed to calculate the post-construction settlement of high-speed railway bridge pile foundation by using the Mesri creep model to describe the soil characteristics and the Mindlin-Geddes method considering pile diameter to calculate the vertical additional stress of pile bottom.A program named CPPS was designed for this method to calculate the post-construction settlement of a high-speed railway bridge pile foundation.The result indicates that the post-construction settlement in 100 years meets the requirements of the engineering specifications,and in the first two decades,the post-construction settlement is about 80% of its total settlement,while the settlement in the rest eighty years tends to be stable.Compared with the measured settlement after laying railway tracks,the calculational result is closed to that of the measured,and the results are conservative with a high computational accuracy.It is noted that the method can be used to calculate the post-construction settlement for the preliminary design of high-speed railway bridge pile foundation.
基金National Key Basic Research Program of China(973 Program)under Grant No.2013CB036300Ministry of Transport Application Foundation Research Project under Grant No.2013319822070+1 种基金the National Natural Science Foundation of China under Grant Nos.91215302,51222809 and 51178353Program for New Century Excellent Talents in University
文摘This article explores the fundamentals of small-radius curved ramp bridges.It covers the selection of box girder spans,support methods,and forms,along with design optimization techniques for this type of bridge structure.The purpose of this paper is to provide robust support for enhancing the design quality of these bridges and ensuring their efficacy in real-world applications.
基金Project(2005k002-c-2) supported by the Science and Technology Development Program of Railways Department, China
文摘Mechanical behavior of concrete slab of large-span through tied-arch composite bridge was investigated by finite element analysis (FEA). Improved methods to decrease concrete stresses were discussed based on comparisons of different deck schemes, construction sequences and measures, and ratios of reinforcement. The results show that the mechanical behavior of concrete slab gets worse with the increase of composite regions between steel beams and concrete slab. The deck scheme with the minimum composite region is recommended on condition that both strength and stiffness of the bridge meet design demands under service loads. Adopting in-situ-place construction method, concrete is suggested to be cast after removing the full-supported frameworks under the bridge. Thus, the axial tensile force of concrete slab caused by the first stage dead load is eliminated. Preloading the bridge before concrete casting and removing the load after the concrete reaching its design strength, the stresses of concrete slab caused by the second stage dead load and live load are further reduced or even eliminated. At last, with a high ratio of reinforcement more than 3%, the concrete stresses decrease obviously.
基金Project(2004G016-B) supported by the Science and Technology Development Program of Railways Department,China
文摘Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.
基金This work was financially supported by National Natural Science Foundation of China through Grant 51778471Scientific Project of Education Department of Jiangxi Province GJJ160620Science and Technology Project of Communications Department of Jiangxi Province 2016C0006.
文摘The isolated curved girder bridge's vibration characteristics play a major part in the seismic responses of structures and anti-seismic properties.A clear analytic relationship between design parameters and the system's vibration characteristics could be established by its simplified dynamic analysis model,making it convenient for providing a reference to the optimization of design and safety analysis.A double-mass six-degree-of-freedom model for curved girder bridges with isolation bearings installed at the top of the bridge piers is built and a simplified analysis method for the vibration characteristics of the system is provided.Combined with the Matlab programming,the influences of radius of curvature,central angle,bridge deck width and damping ratio of the isolation layer and circular frequency of the isolation layer of isolated curved girder bridges on the pseudo-undamped natural circular frequency(called pseudo-frequency for short)and system damping ratio are systematically analyzed,and the sensitivity of vibration characteristics of isolated curved girder bridges is studied.The results show that the vibration characteristics of isolated curved girder bridges can be reflected well with this simplified model and calculation method.The pseudo-frequency of curved girder and system damping ratios increases with the increase of the isolation layer.The third-order vibration characteristic is more sensitive to the parameters of a curved girder,and the first-order vibration characteristic is sensitive to both central angle and radius of curvature to some extent while insensitive to the width of the bridge deck.Furthermore,the second-order vibration characteristic is not sensitive to the parameters of a curved girder.
