Lamb Wave(LW) simulation under time-varying conditions is an effective and low cost way to study the problem of the low reliability of the structural health monitoring methods based on the LW and Piezoelectric Transdu...Lamb Wave(LW) simulation under time-varying conditions is an effective and low cost way to study the problem of the low reliability of the structural health monitoring methods based on the LW and Piezoelectric Transducer(PT). In this paper, a multiphysics simulation method of the LW propagation with the PTs under load condition is proposed. With this method, two key mechanisms of the load influence on the LW propagation are considered and coupled with each other. The first mechanism is the acoustoelastic effect which is the main reason of the LW velocity change. The second key mechanism is the load influence on piezoelectric materials, which results in a change of the amplitude. Based on the computational platform of the COMSOL Multiphysics, a multiphysics simulation model of the LW propagation with the PTs under load condition is established. The simulation model includes two physical phenomena. The first one is called solid mechanics, which is used to simulate the acoustoelastic effect being combined with the hyperelastic material properties of the structure in which the LW propagates. The second one is called electromechanical coupling, which considers the simulation of the piezoelectric effect of the PTs for the LW excitation and sensing. To simulate the load influence on piezoelectric materials, a non-linear numerical model of the relationship between the load and the piezoelectric coefficient d31 is established based on an experiment of the load influence on the LW. The simulation results under uniaxial tensile load condition are obtained and are compared with the data obtained from the experiment. It shows that the variations of the phase velocity and amplitude of the LW obtained from the simulation model match the experimental results well.展开更多
The objective of this study is to develop a novel and efficient model for forecasting the nonlinear behavior of structures in response to time-varying random excitation.The key idea is to design a deep learning archit...The objective of this study is to develop a novel and efficient model for forecasting the nonlinear behavior of structures in response to time-varying random excitation.The key idea is to design a deep learning architecture to leverage the relationships,between external excitations and structure's vibration signals,and between historical values and future values,within multiple time-series data.The proposed method consists of two main steps:the first step applies a global attention mechanism to combine multiple-measured time series and time-varying excitation into a weighted time series before feeding it to a temporal architecture;the second step utilizes a self-attention mechanism followed by a fully connected layer to predict multi-step future values.The viability of the proposed method is demonstrated via two case studies involving synthetic data from a three-dimensional(3D)reinforced concrete structure and experimental data from an 18-story steel frame.Furthermore,comparison and robustness studies are carried out,showing that the proposed method outperforms conventional methods and maintains high performance in the presence of noise with an amplitude of less than 10%.展开更多
When the bridge components needing maintenance are the world problem at present,and the health monitoring system is considered to be a very helpful tool for solving this problem.In this paper,a large number of s...When the bridge components needing maintenance are the world problem at present,and the health monitoring system is considered to be a very helpful tool for solving this problem.In this paper,a large number of strain data acquired from the structural health monitoring system(SHMS)installed on a continuous rigid frame bridge are adopted to do reliability assessment.Firstly,a calculation method of punctiform time-dependent reliability is proposed based on the basic reliability theory,and introduced how to calculate reliability of the bridge by using the stress data transformed from the strain data.Secondly,combined with“Three Sigma”principle and the basic pressure safety reserve requirement,the critical load effects distribution function of the bridge is defined,and then the maintenance reliability threshold for controlling the unfavorable load state which appears in the early operation stage of this type bridge is suggested,and then the combination of bridge maintenance management and health monitoring system is realized.Finally,the transformed stress distribution certifies that the load effects of concrete bridges practically have a normal distribution;as for the concrete continuous rigid frame bridge with C50 strength grade concrete,the retrofit reliability threshold should be valued at 6.13.The methodology suggested in this article can help bridge engineers do effective maintenance of bridges,which can effectively extend the service life of the bridge and bring better economic and social benefits.展开更多
In general,the material properties,loads,resistance of the prestressed concrete continuous rigid frame bridge in different construction stages are time-varying.So,it is essential to monitor the internal force state wh...In general,the material properties,loads,resistance of the prestressed concrete continuous rigid frame bridge in different construction stages are time-varying.So,it is essential to monitor the internal force state when the bridge is in construction.Among them,how to assess the safety is one of the challenges.As the continuous monitoring over a long-term period can increase the reliability of the assessment,so,based on a large number of monitored strain data collected from the structural health monitoring system(SHMS)during construction,a calculation method of the punctiform time-varying reliability is proposed in this paper to evaluate the stress state of this type bridge in cantilever construction stage by using the basic reliability theory.At the same time,the optimal stress distribution function in the bridge mid-span base plate is determined when the bridge is closed.This method can provide basis and direction for the internal force control of this type bridge in construction process.So,it can reduce the bridge safety and quality accidents in construction stages.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51635008 and 51575263)the Fok Ying Tung Education Foundation of China(No.161048)+1 种基金the Program for Distinguished Talents of Six Domains in Jiangsu Province of China(No.GDZB-035)the Priority Academic Program Development of Jiangsu Higher Education Institutions of China
文摘Lamb Wave(LW) simulation under time-varying conditions is an effective and low cost way to study the problem of the low reliability of the structural health monitoring methods based on the LW and Piezoelectric Transducer(PT). In this paper, a multiphysics simulation method of the LW propagation with the PTs under load condition is proposed. With this method, two key mechanisms of the load influence on the LW propagation are considered and coupled with each other. The first mechanism is the acoustoelastic effect which is the main reason of the LW velocity change. The second key mechanism is the load influence on piezoelectric materials, which results in a change of the amplitude. Based on the computational platform of the COMSOL Multiphysics, a multiphysics simulation model of the LW propagation with the PTs under load condition is established. The simulation model includes two physical phenomena. The first one is called solid mechanics, which is used to simulate the acoustoelastic effect being combined with the hyperelastic material properties of the structure in which the LW propagates. The second one is called electromechanical coupling, which considers the simulation of the piezoelectric effect of the PTs for the LW excitation and sensing. To simulate the load influence on piezoelectric materials, a non-linear numerical model of the relationship between the load and the piezoelectric coefficient d31 is established based on an experiment of the load influence on the LW. The simulation results under uniaxial tensile load condition are obtained and are compared with the data obtained from the experiment. It shows that the variations of the phase velocity and amplitude of the LW obtained from the simulation model match the experimental results well.
基金This work was financially supported by the Hanoi University of Civil Engineering(Vietnam),ID 28{2023/KHXD-TD}.
文摘The objective of this study is to develop a novel and efficient model for forecasting the nonlinear behavior of structures in response to time-varying random excitation.The key idea is to design a deep learning architecture to leverage the relationships,between external excitations and structure's vibration signals,and between historical values and future values,within multiple time-series data.The proposed method consists of two main steps:the first step applies a global attention mechanism to combine multiple-measured time series and time-varying excitation into a weighted time series before feeding it to a temporal architecture;the second step utilizes a self-attention mechanism followed by a fully connected layer to predict multi-step future values.The viability of the proposed method is demonstrated via two case studies involving synthetic data from a three-dimensional(3D)reinforced concrete structure and experimental data from an 18-story steel frame.Furthermore,comparison and robustness studies are carried out,showing that the proposed method outperforms conventional methods and maintains high performance in the presence of noise with an amplitude of less than 10%.
文摘When the bridge components needing maintenance are the world problem at present,and the health monitoring system is considered to be a very helpful tool for solving this problem.In this paper,a large number of strain data acquired from the structural health monitoring system(SHMS)installed on a continuous rigid frame bridge are adopted to do reliability assessment.Firstly,a calculation method of punctiform time-dependent reliability is proposed based on the basic reliability theory,and introduced how to calculate reliability of the bridge by using the stress data transformed from the strain data.Secondly,combined with“Three Sigma”principle and the basic pressure safety reserve requirement,the critical load effects distribution function of the bridge is defined,and then the maintenance reliability threshold for controlling the unfavorable load state which appears in the early operation stage of this type bridge is suggested,and then the combination of bridge maintenance management and health monitoring system is realized.Finally,the transformed stress distribution certifies that the load effects of concrete bridges practically have a normal distribution;as for the concrete continuous rigid frame bridge with C50 strength grade concrete,the retrofit reliability threshold should be valued at 6.13.The methodology suggested in this article can help bridge engineers do effective maintenance of bridges,which can effectively extend the service life of the bridge and bring better economic and social benefits.
文摘In general,the material properties,loads,resistance of the prestressed concrete continuous rigid frame bridge in different construction stages are time-varying.So,it is essential to monitor the internal force state when the bridge is in construction.Among them,how to assess the safety is one of the challenges.As the continuous monitoring over a long-term period can increase the reliability of the assessment,so,based on a large number of monitored strain data collected from the structural health monitoring system(SHMS)during construction,a calculation method of the punctiform time-varying reliability is proposed in this paper to evaluate the stress state of this type bridge in cantilever construction stage by using the basic reliability theory.At the same time,the optimal stress distribution function in the bridge mid-span base plate is determined when the bridge is closed.This method can provide basis and direction for the internal force control of this type bridge in construction process.So,it can reduce the bridge safety and quality accidents in construction stages.
