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
A critical problem facing data collection in structural health monitoring,for instance via sensor networks,is how to extract the main components and useful features for damage detection.A structural dynamic measuremen...A critical problem facing data collection in structural health monitoring,for instance via sensor networks,is how to extract the main components and useful features for damage detection.A structural dynamic measurement is more often a complex time-varying process and therefore,is prone to dynamic changes in time-frequency contents.To extract the signal components and capture the useful features associated with damage from such nonstationary signals,a technique that combines the time and frequency analysis and shows the signal evolution in both time and frequency is required.Wavelet analyses have proven to be a viable and effective tool in this regard.Wavelet transform(WT)can analyze different signal components and then comparing the characteristics of each signal with a resolution matched to its scale.However,the challenge is the selection of a proper wavelet since various wavelets with varied properties that are to analyze the same data may result in different results.This article presents a study on how to carry out a comparative analysis based on analytic wavelet scalograms,using structural dynamic acceleration responses,to evaluate the effectiveness of various wavelets for damage detection in civil structures.The scalogram’s informative time-frequency regions are examined to analyze the variation of wavelet coefficients and show how the frequency content of a signal changes over time to detect transient events due to damage.Subsequently,damage-induced changes are tracked with time-frequency representations.Towards this aim,energy distribution and sharing information are investigated.The undamaged and damaged simulated comparative results of a structure reveal that the damaged structure were shifted from the undamaged structure.Also,the Bump wavelet shows the best results than the others.展开更多
The objective of this paper is to demonstrate how assessment of seismic vulnerability can be effective in protection against earthquakes.Findings are reported from a case study in a densely populated urban area near a...The objective of this paper is to demonstrate how assessment of seismic vulnerability can be effective in protection against earthquakes.Findings are reported from a case study in a densely populated urban area near an active fault,utilizing practical methods and exact engineering data.Vulnerability factors were determined due to technical considerations,and a field campaign was performed to collect the required data.Multi-criteria decision making was carried out by means of an analytical hierarchy process including a fuzzy standardization.Earthquake scenarios were applied through an implicit vulnerability model.GIS was utilized and the results were analyzed by classifying the state of vulnerability in levels as very low,low,moderate,high,and very high.Seismic resilience was evaluated as vulnerabilities below the moderate state,being about 40% in an intensity of 6 Mercalli and less than 10% in 10 Mercalli.It is concluded that seismic resilience in the area studied is not acceptable,the area is vulnerable in the expected scenarios,and due to the high seismicity of the region,proper crisis management planning is required in parallel with attempts toward retrofitting.In this regard,an emergency map was developed with reference to the assessed vulnerabilities.展开更多
Implementation of efficient vibration control schemes for seismically excited structures is becoming more and more important in recent years.In this study,the influence of different control schemes on the dynamic perf...Implementation of efficient vibration control schemes for seismically excited structures is becoming more and more important in recent years.In this study,the influence of different control schemes on the dynamic performance of a frame structure excited by El Centro wave,with an emphasis on reaching law based control strategies,is examined.Reaching law refers to the reachable problem and criteria for the sliding state of a control system.Three reaching laws are designed to present different sliding mode control strategies by incorporating a state space model that describes structural dynamic characteristics of a frame structure.Both intact and damaged structures are studied by using the aforementioned control strategies.The influence of different structural damage extents,control locations and reaching law based control methods are further investigated.The results show that the structure can be well controlled using the sliding mode strategy when the induced structural damage extent does not exceed the standard percentage for considering the structure was damaged,which is 20%reduction in structure stiffness,as reported in the literature.The control effectiveness is more satisfactory if the control location is the same as the direction of external excitation.Furthermore,to study the chattering phenomenon of the sliding mode control method,approximation and detail components extracted from the phase plots of the sliding mode control system are compared via wavelet transform at different scales.The results show that for the same type of control law,the system behaves with similar chattering phenomenon.展开更多
This paper introduces a stiffness reduction based model developed by the authors to characterize accumulative fatigue damage in unidirectional plies and(0/θ/0)composite laminates in fiber reinforced polymer(FRP)compo...This paper introduces a stiffness reduction based model developed by the authors to characterize accumulative fatigue damage in unidirectional plies and(0/θ/0)composite laminates in fiber reinforced polymer(FRP)composite laminates.The proposed damage detection model is developed based on a damage evolution mechanism,including crack initiation and crack damage progress in matrix,matrix-fiber interface and fibers.Research result demonstrates that the corresponding stiffness of unidirectional composite laminates is reduced as the number of loading cycles progresses.First,three common models in literatures are presented and compared.Tensile viscosity,Young’s modulus and ultimate tensile stress of composites are incorporated as key factors in this model and are modified in accordance with temperature.Four types of FRP composite property parameters,including Carbon Fiber Reinforced Polymer(CFRP),Aramid Fiber Reinforced Polymer(AFRP),Glass Fiber Reinforced Polymer(GFRP),and Basalt Fiber Reinforced Polymer(BFRP),are considered in this research,and a comparative parameter study of FRP unidirectional composite laminates with different off-angle plies using control variate method are discussed.It is concluded that the relationship between the drop in stiffness and the number of cycles also shows three different regions,following the mechanism of damage of FRP composites and the matrix is the dominant factor determined by temperature,while fiber strength is the dominant factor that determine the reliability of composite.展开更多
The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new eros...The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new erosion control method using W-OH solution, a type of hydrophilic polyurethane, to prevent the Pisha sandstone from water erosion. We evaluated the comprehensive effects of W-OH on water erosion resistance and vegetation-growth promotion through simulated scouring tests and field demonstrations on the Ordos Plateau of China. The results of simulated scouring tests show that the water erosion resistance of W-OH treated area was excellent and the cumulative sediment yield reduction reached more than 99%. In the field demonstrations, the vegetation coverage reached approximately 95% in the consolidation-green area, and there was almost no shallow trenches on the entire slope in the treated area. In comparison, the control area experienced severe erosion with deep erosion gullies appeared on the slope and the vegetation coverage was less than 30%. This study illustrated that W-OH treatment can protect the Pisha sandstone from erosion and provide the vegetation seeds a chance to grow. Once the vegetation matured, the effects of consolidation-growth mutual promotion can efficiently and effectively improve the water erosion resistance and ecological restoration.展开更多
Beam-like structures arde a class of common but important structures in engineering.Over the past few centuries,extensive research has been carried out to obtain the static and dynamic response of beam-like structures...Beam-like structures arde a class of common but important structures in engineering.Over the past few centuries,extensive research has been carried out to obtain the static and dynamic response of beam-like structures.Although build-ing the finite element model to predict the response of these structures has proven to be effective,it is not always suitable in all the application cases because of high computational time or lack of accuracy.This paper proposes a novel approach to predict the deflection response of beam-like structures based on a deep neural net-work and the governing differential equation of Euler-Bernoulli beam.The Prandtl-Ishlinskii model is introduced as an element of prediction model to simu-late the plasticity of this beam structure.Finally the application of the proposed approach is demonstrated through four numerical examples including linear elastic/ideal plastic beam under concentrated/sinusoidal load and elastic/plastic continues beam under seismic load to demonstrate a proof of concept for the effectiveness of this AI-based approach.展开更多
A proof-of-concept indirect tire-pressure monitoring system is developed using artificial neural networks to identify the tire pressure of a vehicle tire.A quarter-car model was developed with MATLAB and Simulink to g...A proof-of-concept indirect tire-pressure monitoring system is developed using artificial neural networks to identify the tire pressure of a vehicle tire.A quarter-car model was developed with MATLAB and Simulink to generate simulated accelerometer output data.Simulation data are used to train and evaluate a recurrent neural network with long short-term memory blocks(RNN-LSTM)and a convolutional neural network(CNN)developed in Python with Tensorflow.Bayesian Optimization via SigOpt was used to optimize training and model parameters.The predictive accuracy and training speed of the two models with various parameters are compared.Finally,future work and improvements are discussed.展开更多
Accurate estimation of stiffness loss is a challenging problem in structural health monitoring.In this studyorthogonal wavelet decomposition is used for identifying the stiffness loss in a single degree of freedom spr...Accurate estimation of stiffness loss is a challenging problem in structural health monitoring.In this studyorthogonal wavelet decomposition is used for identifying the stiffness loss in a single degree of freedom spring-mass-dampersystem.The effects of excitation frequency on accuracy of damage detection is investigated.Results show that pseudo-aliaseffects caused by the orthogonal wavelet decomposition(OWD),affect damage detectability.It is demonstrated that theproposed approach is sunable for damage detection when the excitation frequency is relatively low.This study shows how apriori knowledge about the signal and ability to control the sampling frequency can enhance damage detectability.展开更多
The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the co...The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ2 and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.展开更多
Earth buildings are common types of structures in most rural areas in all developing countries.Catastrophic failure and destruction of these structures under seismic loads always result in loss of human lives and econ...Earth buildings are common types of structures in most rural areas in all developing countries.Catastrophic failure and destruction of these structures under seismic loads always result in loss of human lives and economic losses.Wall is an important load-bearing component of raw soil buildings.In this paper,a novel approach is proposed to improve the strength and ductility of adobe walls.Three types of analyses,material properties,mechanical properties,and dynamic properties,are carried out for the seismic performance assessment of the adobe walls.These performed studies include that,material properties of the earth cylinder block,mechanical properties of adobe walls under quasi-static loads,and dynamic performance of adobe walls excited by seismic waves.On investigation of material properties,eighteen cylindrical specimens with a diameter of 100 mm and a height of 110 mm were divided into three groups for compressive,tensile,and split pull strength tests,respectively.The results of the three groups of tests showed that the yield strength ratios of compressive,tensile,and shear strength were about 1:0.3:0.2.In order to study the performance of structural components,three 1/3 scale model raw soil walls with a dimension of 1,200 mm in width,1,000 mm in height,and 310 mm in thickness were tested under cyclic loading.The average wall capacity of the wall obtained by the test was about 13.5 kN and the average displacement angle was about 1/135.The numerical simulation experiment is used to explore the mechanism of structural failure.A three-dimensional finite element model is established by choosing the material parameters based on the above test outcomes.The accuracy of the numerical simulation experiment is verified by simulation and comparison of the above quasi-static test results.Further,the collapse process of raw soil wall under a seismic wave is simulated for exploring the response and damage mechanism of structure.Based on those systematically analyzed,some useful suggested guidelines are provided for improving the seismic performance of raw soil buildings.展开更多
Damage detection is an important area with growing interest in mechanical and structural engineering.One of the critical issues in damage detection is how to determine indices sensitive to the structural damage and in...Damage detection is an important area with growing interest in mechanical and structural engineering.One of the critical issues in damage detection is how to determine indices sensitive to the structural damage and insensitive to the surrounding environmental variations.Current damage identification indices commonly focus on structural dynamic characteristics such as natural frequencies,mode shapes,and frequency responses.This study aimed at developing a technique based on energy Curvature Difference,power spectrum density,correlation-based index,load distribution factor,and neutral axis shift to assess the bridge deck condition.In addition to tracking energy and frequency over time using wavelet packet transform,in order to further demonstrate the feasibility and validity of the proposed technique for bridge condition assessment,experimental strain data measured from two stages of a bridge in the different intervals were used.The comparative analysis results of the bridge in first and second stage show changes in the proposed feature values.It is concluded,these changes in the values of the proposed features can be used to assess the bridge deck performance.展开更多
Toll-like receptors are well-defined barriers in innate immunity. Among them hTLR4 on the surface of monocytes, plays a critical role in the formation of atherosclerotic plaques, plaque instability and arterial remode...Toll-like receptors are well-defined barriers in innate immunity. Among them hTLR4 on the surface of monocytes, plays a critical role in the formation of atherosclerotic plaques, plaque instability and arterial remodeling through production of inflammatory cytokines. This study was designed to examine the association of hTLR4 monocyte expression and response with the severity of coronary stenosis in patients with stable angina (SA). Blood samples were obtained from 39 patients with SA who were scheduled for a coronary angiography and from 28 healthy volunteers. The samples were collected before the procedure. Expression of hTLR4 on CD14+ monocytes and serum levels of TNF-α and IL-1β were measured using flowcytometry and ELISA techniques respectively. Percentage stenosis diameter was measured by comparing the area of coronary stenosis to an adjacent normal segment of the vessel. Compared with control group, patients showed upregulation of hTLR4+/CD14+ monocytes. Furthermore, patients with more severe coronary stenosis exhibited enhanced expression of hTLR4+/CD14+ monocytes (p α (p β. In addition, significant correlations were seen between percentage stenosis diameter and monocyte expression of hTLR4 as well as TNF-α. hTLR4 monocytic expression and related cytokines are positively associated percentage stenosis diameter. These results suggest that hTLR4 activity may be involved in progression of atherosclerosis.展开更多
In the context of civil engineering applications,vibration responses are complex,exhibiting variations in time and space and often containing nonlinearity and uncertainties not considered during data collection.These ...In the context of civil engineering applications,vibration responses are complex,exhibiting variations in time and space and often containing nonlinearity and uncertainties not considered during data collection.These responses can also be contaminated by various sources,impacting damage identification processes.A significant challenge is how to effectively remove noise from these data to obtain reliable damage indicators that are unresponsive to noise and environmental factors.This study proposes a new denoising algorithm based on discrete wavelet transform(DWT)that addresses this issue.The suggested method offers a strategy for denoising using distinct thresholds for positive and negative coefficient values at each band and applying denoising process to both detail and trend components.The results prove the effectiveness of the technique and show that Bayes thresholding performs better than the other techniques in terms of the evaluated metrics.This suggests that Bayes thresholding is a more accurate and robust technique for thresholding compared to other common techniques.展开更多
Pisha sandstone is a special kind of soft rock in the semiarid region along the up and middle reaches of Yellow River and Loess Plateau and is severely eroded by wind,rainfall and gravity force.Pisha sandstone region ...Pisha sandstone is a special kind of soft rock in the semiarid region along the up and middle reaches of Yellow River and Loess Plateau and is severely eroded by wind,rainfall and gravity force.Pisha sandstone region is called 'the most severe water loss and soil erosion in the world' and referred to as the 'Earth Cancer' by local residents and experts both at home and abroad.The plan for the control of Pisha sandstone started in the 1950s.Since then a series of projects have been implemented,both engineering and vegetation measures have been developed and widely used to protect Pisha sandstone from erosion.Since seabuckthom was introduced as a viable approach for soil erosion protection and its implementation resulted in a breakthrough to control Loess Plateau,it was considered as an important and efficient measure.Then the seabuckthom flexible dam was proposed for coarse sediment retention and fine sediment deposition.And then a new comprehensive control model using consolidation materials combined with vegetation was proposed and promising results were achieved both in laboratory and field demonstrations.In the future,the complex erosion mechanism and ecological carrying capacity should he studied further and more efficient and practical comprehensive measures shall be developed.Moreover,monitoring systems shall be used to predict and detect the changes in the Pisha sandstone slope and structure.展开更多
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.
文摘A critical problem facing data collection in structural health monitoring,for instance via sensor networks,is how to extract the main components and useful features for damage detection.A structural dynamic measurement is more often a complex time-varying process and therefore,is prone to dynamic changes in time-frequency contents.To extract the signal components and capture the useful features associated with damage from such nonstationary signals,a technique that combines the time and frequency analysis and shows the signal evolution in both time and frequency is required.Wavelet analyses have proven to be a viable and effective tool in this regard.Wavelet transform(WT)can analyze different signal components and then comparing the characteristics of each signal with a resolution matched to its scale.However,the challenge is the selection of a proper wavelet since various wavelets with varied properties that are to analyze the same data may result in different results.This article presents a study on how to carry out a comparative analysis based on analytic wavelet scalograms,using structural dynamic acceleration responses,to evaluate the effectiveness of various wavelets for damage detection in civil structures.The scalogram’s informative time-frequency regions are examined to analyze the variation of wavelet coefficients and show how the frequency content of a signal changes over time to detect transient events due to damage.Subsequently,damage-induced changes are tracked with time-frequency representations.Towards this aim,energy distribution and sharing information are investigated.The undamaged and damaged simulated comparative results of a structure reveal that the damaged structure were shifted from the undamaged structure.Also,the Bump wavelet shows the best results than the others.
文摘The objective of this paper is to demonstrate how assessment of seismic vulnerability can be effective in protection against earthquakes.Findings are reported from a case study in a densely populated urban area near an active fault,utilizing practical methods and exact engineering data.Vulnerability factors were determined due to technical considerations,and a field campaign was performed to collect the required data.Multi-criteria decision making was carried out by means of an analytical hierarchy process including a fuzzy standardization.Earthquake scenarios were applied through an implicit vulnerability model.GIS was utilized and the results were analyzed by classifying the state of vulnerability in levels as very low,low,moderate,high,and very high.Seismic resilience was evaluated as vulnerabilities below the moderate state,being about 40% in an intensity of 6 Mercalli and less than 10% in 10 Mercalli.It is concluded that seismic resilience in the area studied is not acceptable,the area is vulnerable in the expected scenarios,and due to the high seismicity of the region,proper crisis management planning is required in parallel with attempts toward retrofitting.In this regard,an emergency map was developed with reference to the assessed vulnerabilities.
文摘Implementation of efficient vibration control schemes for seismically excited structures is becoming more and more important in recent years.In this study,the influence of different control schemes on the dynamic performance of a frame structure excited by El Centro wave,with an emphasis on reaching law based control strategies,is examined.Reaching law refers to the reachable problem and criteria for the sliding state of a control system.Three reaching laws are designed to present different sliding mode control strategies by incorporating a state space model that describes structural dynamic characteristics of a frame structure.Both intact and damaged structures are studied by using the aforementioned control strategies.The influence of different structural damage extents,control locations and reaching law based control methods are further investigated.The results show that the structure can be well controlled using the sliding mode strategy when the induced structural damage extent does not exceed the standard percentage for considering the structure was damaged,which is 20%reduction in structure stiffness,as reported in the literature.The control effectiveness is more satisfactory if the control location is the same as the direction of external excitation.Furthermore,to study the chattering phenomenon of the sliding mode control method,approximation and detail components extracted from the phase plots of the sliding mode control system are compared via wavelet transform at different scales.The results show that for the same type of control law,the system behaves with similar chattering phenomenon.
文摘This paper introduces a stiffness reduction based model developed by the authors to characterize accumulative fatigue damage in unidirectional plies and(0/θ/0)composite laminates in fiber reinforced polymer(FRP)composite laminates.The proposed damage detection model is developed based on a damage evolution mechanism,including crack initiation and crack damage progress in matrix,matrix-fiber interface and fibers.Research result demonstrates that the corresponding stiffness of unidirectional composite laminates is reduced as the number of loading cycles progresses.First,three common models in literatures are presented and compared.Tensile viscosity,Young’s modulus and ultimate tensile stress of composites are incorporated as key factors in this model and are modified in accordance with temperature.Four types of FRP composite property parameters,including Carbon Fiber Reinforced Polymer(CFRP),Aramid Fiber Reinforced Polymer(AFRP),Glass Fiber Reinforced Polymer(GFRP),and Basalt Fiber Reinforced Polymer(BFRP),are considered in this research,and a comparative parameter study of FRP unidirectional composite laminates with different off-angle plies using control variate method are discussed.It is concluded that the relationship between the drop in stiffness and the number of cycles also shows three different regions,following the mechanism of damage of FRP composites and the matrix is the dominant factor determined by temperature,while fiber strength is the dominant factor that determine the reliability of composite.
基金funded by the National Key Research and Development Program of China (2017YFC0504505)the National Key Technology Support Program of China during the Twelfth Five-year Plan Period (2013BAC05B02, 2013BAC05B04)
文摘The Pisha sandstone-coverd area is among the regions that suffer from the most severe water loss and soil erosion in China and is the main source of coarse sand for the Yellow River. This study demonstrated a new erosion control method using W-OH solution, a type of hydrophilic polyurethane, to prevent the Pisha sandstone from water erosion. We evaluated the comprehensive effects of W-OH on water erosion resistance and vegetation-growth promotion through simulated scouring tests and field demonstrations on the Ordos Plateau of China. The results of simulated scouring tests show that the water erosion resistance of W-OH treated area was excellent and the cumulative sediment yield reduction reached more than 99%. In the field demonstrations, the vegetation coverage reached approximately 95% in the consolidation-green area, and there was almost no shallow trenches on the entire slope in the treated area. In comparison, the control area experienced severe erosion with deep erosion gullies appeared on the slope and the vegetation coverage was less than 30%. This study illustrated that W-OH treatment can protect the Pisha sandstone from erosion and provide the vegetation seeds a chance to grow. Once the vegetation matured, the effects of consolidation-growth mutual promotion can efficiently and effectively improve the water erosion resistance and ecological restoration.
文摘Beam-like structures arde a class of common but important structures in engineering.Over the past few centuries,extensive research has been carried out to obtain the static and dynamic response of beam-like structures.Although build-ing the finite element model to predict the response of these structures has proven to be effective,it is not always suitable in all the application cases because of high computational time or lack of accuracy.This paper proposes a novel approach to predict the deflection response of beam-like structures based on a deep neural net-work and the governing differential equation of Euler-Bernoulli beam.The Prandtl-Ishlinskii model is introduced as an element of prediction model to simu-late the plasticity of this beam structure.Finally the application of the proposed approach is demonstrated through four numerical examples including linear elastic/ideal plastic beam under concentrated/sinusoidal load and elastic/plastic continues beam under seismic load to demonstrate a proof of concept for the effectiveness of this AI-based approach.
文摘A proof-of-concept indirect tire-pressure monitoring system is developed using artificial neural networks to identify the tire pressure of a vehicle tire.A quarter-car model was developed with MATLAB and Simulink to generate simulated accelerometer output data.Simulation data are used to train and evaluate a recurrent neural network with long short-term memory blocks(RNN-LSTM)and a convolutional neural network(CNN)developed in Python with Tensorflow.Bayesian Optimization via SigOpt was used to optimize training and model parameters.The predictive accuracy and training speed of the two models with various parameters are compared.Finally,future work and improvements are discussed.
文摘Accurate estimation of stiffness loss is a challenging problem in structural health monitoring.In this studyorthogonal wavelet decomposition is used for identifying the stiffness loss in a single degree of freedom spring-mass-dampersystem.The effects of excitation frequency on accuracy of damage detection is investigated.Results show that pseudo-aliaseffects caused by the orthogonal wavelet decomposition(OWD),affect damage detectability.It is demonstrated that theproposed approach is sunable for damage detection when the excitation frequency is relatively low.This study shows how apriori knowledge about the signal and ability to control the sampling frequency can enhance damage detectability.
基金Project(2010-K2-8)supported by Science and Technology Program of the Ministry of Housing and Urban Rural Development,ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ2 and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.
文摘Earth buildings are common types of structures in most rural areas in all developing countries.Catastrophic failure and destruction of these structures under seismic loads always result in loss of human lives and economic losses.Wall is an important load-bearing component of raw soil buildings.In this paper,a novel approach is proposed to improve the strength and ductility of adobe walls.Three types of analyses,material properties,mechanical properties,and dynamic properties,are carried out for the seismic performance assessment of the adobe walls.These performed studies include that,material properties of the earth cylinder block,mechanical properties of adobe walls under quasi-static loads,and dynamic performance of adobe walls excited by seismic waves.On investigation of material properties,eighteen cylindrical specimens with a diameter of 100 mm and a height of 110 mm were divided into three groups for compressive,tensile,and split pull strength tests,respectively.The results of the three groups of tests showed that the yield strength ratios of compressive,tensile,and shear strength were about 1:0.3:0.2.In order to study the performance of structural components,three 1/3 scale model raw soil walls with a dimension of 1,200 mm in width,1,000 mm in height,and 310 mm in thickness were tested under cyclic loading.The average wall capacity of the wall obtained by the test was about 13.5 kN and the average displacement angle was about 1/135.The numerical simulation experiment is used to explore the mechanism of structural failure.A three-dimensional finite element model is established by choosing the material parameters based on the above test outcomes.The accuracy of the numerical simulation experiment is verified by simulation and comparison of the above quasi-static test results.Further,the collapse process of raw soil wall under a seismic wave is simulated for exploring the response and damage mechanism of structure.Based on those systematically analyzed,some useful suggested guidelines are provided for improving the seismic performance of raw soil buildings.
文摘Damage detection is an important area with growing interest in mechanical and structural engineering.One of the critical issues in damage detection is how to determine indices sensitive to the structural damage and insensitive to the surrounding environmental variations.Current damage identification indices commonly focus on structural dynamic characteristics such as natural frequencies,mode shapes,and frequency responses.This study aimed at developing a technique based on energy Curvature Difference,power spectrum density,correlation-based index,load distribution factor,and neutral axis shift to assess the bridge deck condition.In addition to tracking energy and frequency over time using wavelet packet transform,in order to further demonstrate the feasibility and validity of the proposed technique for bridge condition assessment,experimental strain data measured from two stages of a bridge in the different intervals were used.The comparative analysis results of the bridge in first and second stage show changes in the proposed feature values.It is concluded,these changes in the values of the proposed features can be used to assess the bridge deck performance.
文摘Toll-like receptors are well-defined barriers in innate immunity. Among them hTLR4 on the surface of monocytes, plays a critical role in the formation of atherosclerotic plaques, plaque instability and arterial remodeling through production of inflammatory cytokines. This study was designed to examine the association of hTLR4 monocyte expression and response with the severity of coronary stenosis in patients with stable angina (SA). Blood samples were obtained from 39 patients with SA who were scheduled for a coronary angiography and from 28 healthy volunteers. The samples were collected before the procedure. Expression of hTLR4 on CD14+ monocytes and serum levels of TNF-α and IL-1β were measured using flowcytometry and ELISA techniques respectively. Percentage stenosis diameter was measured by comparing the area of coronary stenosis to an adjacent normal segment of the vessel. Compared with control group, patients showed upregulation of hTLR4+/CD14+ monocytes. Furthermore, patients with more severe coronary stenosis exhibited enhanced expression of hTLR4+/CD14+ monocytes (p α (p β. In addition, significant correlations were seen between percentage stenosis diameter and monocyte expression of hTLR4 as well as TNF-α. hTLR4 monocytic expression and related cytokines are positively associated percentage stenosis diameter. These results suggest that hTLR4 activity may be involved in progression of atherosclerosis.
基金support from National Natural Science Foundation of China(Grant No.52178115)the support provided by the International Institeu for Urban Systems Engineering at Southeast University.
文摘In the context of civil engineering applications,vibration responses are complex,exhibiting variations in time and space and often containing nonlinearity and uncertainties not considered during data collection.These responses can also be contaminated by various sources,impacting damage identification processes.A significant challenge is how to effectively remove noise from these data to obtain reliable damage indicators that are unresponsive to noise and environmental factors.This study proposes a new denoising algorithm based on discrete wavelet transform(DWT)that addresses this issue.The suggested method offers a strategy for denoising using distinct thresholds for positive and negative coefficient values at each band and applying denoising process to both detail and trend components.The results prove the effectiveness of the technique and show that Bayes thresholding performs better than the other techniques in terms of the evaluated metrics.This suggests that Bayes thresholding is a more accurate and robust technique for thresholding compared to other common techniques.
基金This work is funded by the State Key Research Development Program of China(Grant no.2017YFC0504505)Key Projects of the National Science&Technology Pillar Program(Grant no.2013BAC05B02)Natural Science Foundation of Jiangsu Province(BK20151401).
文摘Pisha sandstone is a special kind of soft rock in the semiarid region along the up and middle reaches of Yellow River and Loess Plateau and is severely eroded by wind,rainfall and gravity force.Pisha sandstone region is called 'the most severe water loss and soil erosion in the world' and referred to as the 'Earth Cancer' by local residents and experts both at home and abroad.The plan for the control of Pisha sandstone started in the 1950s.Since then a series of projects have been implemented,both engineering and vegetation measures have been developed and widely used to protect Pisha sandstone from erosion.Since seabuckthom was introduced as a viable approach for soil erosion protection and its implementation resulted in a breakthrough to control Loess Plateau,it was considered as an important and efficient measure.Then the seabuckthom flexible dam was proposed for coarse sediment retention and fine sediment deposition.And then a new comprehensive control model using consolidation materials combined with vegetation was proposed and promising results were achieved both in laboratory and field demonstrations.In the future,the complex erosion mechanism and ecological carrying capacity should he studied further and more efficient and practical comprehensive measures shall be developed.Moreover,monitoring systems shall be used to predict and detect the changes in the Pisha sandstone slope and structure.
