Nonlinear boundary parameter identification of bridges based on temperature-induced strains

Zuo-Cai Wang,Guo-Peng Zha,Wei-Xin Ren,Ke Hu,Hao Yang 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.5

Temperature-induced responses, such as strains and displacements, are related to the boundary conditions. Therefore, it is required to determine the boundary conditions to establish a reliable bridge model for temperature-induced responses analysis. Particularly, bridge bearings usually present nonlinear behavior with an increase in load, and the nonlinear boundary conditions cause significant effect on temperature-induced responses. In this paper, the bridge nonlinear boundary conditions were simulated as bilinear translational or rotational springs, and the boundary parameters of the bilinear springs were identified based on the measured temperature-induced responses. First of all, the temperature-induced responses of a simply support beam with nonlinear translational and rotational springs subjected to various temperature loads were analyzed. The simulated temperature-induced strains and displacements were assumed as measured data. To identify the nonlinear translational and rotational boundary parameters of the bridge, the objective function based on the temperature-induced responses is then created, and the nonlinear boundary parameters were further identified by using the nonlinear least squares optimization algorithm. Then, a beam structure with nonlinear translational and rotational springs was simulated as a numerical example, and the nonlinear boundary parameters were identified based on the proposed method. The numerical results show that the proposed method can effectively identify the parameters of the nonlinear boundary conditions. Finally, the boundary parameters of a real arch bridge were identified based on the measured strain data and the proposed method. Since the bearings of the real bridge do not perform nonlinear behavior, only the linear boundary parameters of the bridge model were identified. Based on the bridge model and the identified boundary conditions, the temperature-induced strains were recalculated to compare with the measured strain data. The recalculated temperature-induced strains are in a good agreement with the real measured data.

Damage detection of nonlinear structures with analytical mode decomposition and Hilbert transform

Wang, Zuo-Cai,Geng, Dong,Ren, Wei-Xin,Chen, Gen-Da,Zhang, Guang-Feng Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.1

This paper proposes an analytical mode decomposition (AMD) and Hilbert transform method for structural nonlinearity quantification and damage detection under earthquake loads. The measured structural response is first decomposed into several intrinsic mode functions (IMF) using the proposed AMD method. Each IMF is an amplitude modulated-frequency modulated signal with narrow frequency bandwidth. Then, the instantaneous frequencies of the decomposed IMF can be defined with Hilbert transform. However, for a nonlinear structure, the defined instantaneous frequencies from the decomposed IMF are not equal to the instantaneous frequencies of the structure itself. The theoretical derivation in this paper indicates that the instantaneous frequency of the decomposed measured response includes a slowly-varying part which represents the instantaneous frequency of the structure and rapidly-varying part for a nonlinear structure subjected to earthquake excitations. To eliminate the rapidly-varying part effects, the instantaneous frequency is integrated over time duration. Then the degree of nonlinearity index, which represents the damage severity of structure, is defined based on the integrated instantaneous frequency in this paper. A one-story hysteretic nonlinear structure with various earthquake excitations are simulated as numerical examples and the degree of nonlinearity index is obtained. Finally, the degree of nonlinearity index is estimated from the experimental data of a seven-story building under four earthquake excitations. The index values for the building subjected to a low intensity earthquake excitation, two medium intensity earthquake excitations, and a large intensity earthquake excitation are calculated as 12.8%, 23.0%, 23.2%, and 39.5%, respectively.

A data fusion method for bridge displacement reconstruction based on LSTM networks

Zuo-Cai Wang,Da-You Duan,Xiao-Tong Sun,Yu Xin 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.4

Bridge displacement contains vital information for bridge condition and performance. Due to the limits of direct displacement measurement methods, the indirect displacement reconstruction methods based on the strain or acceleration data are also developed in engineering applications. There are still some deficiencies of the displacement reconstruction methods based on strain or acceleration in practice. This paper proposed a novel method based on long short-term memory (LSTM) networks to reconstruct the bridge dynamic displacements with the strain and acceleration data source. The LSTM networks with three hidden layers are utilized to map the relationships between the measured responses and the bridge displacement. To achieve the data fusion, the input strain and acceleration data need to be preprocessed by normalization and then the corresponding dynamic displacement responses can be reconstructed by the LSTM networks. In the numerical simulation, the errors of the displacement reconstruction are below 9% for different load cases, and the proposed method is robust when the input strain and acceleration data contains additive noise. The hyper-parameter effect is analyzed and the displacement reconstruction accuracies of different machine learning methods are compared. For experimental verification, the errors are below 6% for the simply supported beam and continuous beam cases. Both the numerical and experimental results indicate that the proposed data fusion method can accurately reconstruct the displacement.

Damage detection of nonlinear structures with analytical mode decomposition and Hilbert transform

Zuo-Cai Wang,Dong Geng,Wei-Xin Ren,Guang-Feng Zhang,Gen-Da Chen 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.1

This paper proposes an analytical mode decomposition (AMD) and Hilbert transform method for structural nonlinearity quantification and damage detection under earthquake loads. The measured structural response is first decomposed into several intrinsic mode functions (IMF) using the proposed AMD method. Each IMF is an amplitude modulated-frequency modulated signal with narrow frequency bandwidth. Then, the instantaneous frequencies of the decomposed IMF can be defined with Hilbert transform. However, for a nonlinear structure, the defined instantaneous frequencies from the decomposed IMF are not equal to the instantaneous frequencies of the structure itself. The theoretical derivation in this paper indicates that the instantaneous frequency of the decomposed measured response includes a slowly-varying part which represents the instantaneous frequency of the structure and rapidly-varying part for a nonlinear structure subjected to earthquake excitations. To eliminate the rapidly-varying part effects, the instantaneous frequency is integrated over time duration. Then the degree of nonlinearity index, which represents the damage severity of structure, is defined based on the integrated instantaneous frequency in this paper. A one-story hysteretic nonlinear structure with various earthquake excitations are simulated as numerical examples and the degree of nonlinearity index is obtained. Finally, the degree of nonlinearity index is estimated from the experimental data of a seven-story building under four earthquake excitations. The index values for the building subjected to a low intensity earthquake excitation, two medium intensity earthquake excitations, and a large intensity earthquake excitation are calculated as 12.8%, 23.0%, 23.2%, and 39.5%, respectively.

Time-varying physical parameter identification of shear type structures based on discrete wavelet transform

Wang, Chao,Ren, Wei-Xin,Wang, Zuo-Cai,Zhu, Hong-Ping Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

This paper proposed a discrete wavelet transform based method for time-varying physical parameter identification of shear type structures. The time-varying physical parameters are dispersed and expanded at multi-scale as profile and detail signal using discrete wavelet basis. To reduce the number of unknown quantity, the wavelet coefficients that reflect the detail signal are ignored by setting as zero value. Consequently, the time-varying parameter can be approximately estimated only using the scale coefficients that reflect the profile signal, and the identification task is transformed to an equivalent time-invariant scale coefficient estimation. The time-invariant scale coefficients can be simply estimated using regular least-squares methods, and then the original time-varying physical parameters can be reconstructed by using the identified time-invariant scale coefficients. To reduce the influence of the ill-posed problem of equation resolving caused by noise, the Tikhonov regularization method instead of regular least-squares method is used in the paper to estimate the scale coefficients. A two-story shear type frame structure with time-varying stiffness and damping are simulated to validate the effectiveness and accuracy of the proposed method. It is demonstrated that the identified time-varying stiffness is with a good accuracy, while the identified damping is sensitive to noise.

AN ULTRA-LUMINOUS QUASAR AT <i>z</i> = 5.363 WITH A TEN BILLION SOLAR MASS BLACK HOLE AND A METAL-RICH DLA AT <i>z</i> ∼ 5

Wang, Feige,Wu, Xue-Bing,Fan, Xiaohui,Yang, Jinyi,Cai, Zheng,Yi, Weimin,Zuo, Wenwen,Wang, Ran,McGreer, Ian D.,Ho, Luis C.,Kim, Minjin,Yang, Qian,Bian, Fuyan,Jiang, Linhua IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.807 No.1

<P>We report the discovery of an ultra-luminous quasar J030642.51+185315.8 (hereafter J0306+1853) at redshift 5.363, which hosts a supermassive black hole with M-BH = (1.07 +/- 0.27) x 10(10) M-circle dot. With an absolute magnitude M-1450 = -28.92 and a bolometric luminosity L-bol similar to 3.4 x 10(14) L-circle dot, J0306+1853 is one of the most luminous objects in the early universe. It is not likely to be a beamed source based on its small flux variability, low radio loudness, and normal broad emission lines. In addition, a z = 4.986 damped Ly alpha system (DLA) with [M/H] = -1.3 +/- 0.1, among the most metal-rich DLAs at z greater than or similar to 5, is detected in the absorption spectrum of this quasar. This ultra-luminous quasar puts strong constraints on the bright end of the quasar luminosity function and massive end of the black hole mass function. It will provide a unique laboratory for the study of BH growth and the co-evolution between a BH and the host galaxy with multi-wavelength follow-up observations. The future high-resolution spectra will give more insight into the DLA and other absorption systems along the line of sight of J0306+1853.</P>

Time-varying physical parameter identification of shear type structures based on discrete wavelet transform

Chao Wang,Wei-Xin Ren,Zuo-Cai Wang,Hong-Ping Zhu 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.5

This paper proposed a discrete wavelet transform based method for time-varying physical parameter identification of shear type structures. The time-varying physical parameters are dispersed and expanded at multi-scale as profile and detail signal using discrete wavelet basis. To reduce the number of unknown quantity, the wavelet coefficients that reflect the detail signal are ignored by setting as zero value. Consequently, the time-varying parameter can be approximately estimated only using the scale coefficients that reflect the profile signal, and the identification task is transformed to an equivalent time-invariant scale coefficient estimation. The time-invariant scale coefficients can be simply estimated using regular least-squares methods, and then the original time-varying physical parameters can be reconstructed by using the identified time-invariant scale coefficients. To reduce the influence of the ill-posed problem of equation resolving caused by noise, the Tikhonov regularization method instead of regular least-squares method is used in the paper to estimate the scale coefficients. A two-story shear type frame structure with time-varying stiffness and damping are simulated to validate the effectiveness and accuracy of the proposed method. It is demonstrated that the identified time-varying stiffness is with a good accuracy, while the identified damping is sensitive to noise.

Optimization of the microemulsion formulation of curcuma oil and evaluation of its acaricidal efficacy against Tetranychus cinnabarinus (Boisduval) (Acari: Tetranychidae)

Cheng Zuo-Hui,Fan Fang-Fang,Zhao Jin-Zhong,Li Rui,Li Sheng-Cai,Zhang En-Jia,Liu Yu-Kun,Wang Jue-Ying,Zhu Xiang-Run,Tian Yong-Ming 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.4

The microemulsion formulation (hereafter formulation) of curcuma oil and its acaricidal efficacy against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae) were optimized in the laboratory to evaluate their spray effectiveness of oviposition inhibition and repellence. Ethovision XT6 was used to analyse the effects of the sublethal concentrations (LC 20 ) of curcuma oil and the formulation on the behaviors of T. cinnabarinus. The results showed that Tween-80 was the best surfactant, Isopropanol was the best co-surfactant and K m = 2:1 was the best condition for the formulation. The prepared microemulsions are stable under conditions of centrifugation and incubation for extended periods. The results showed that the effect of the spray bioassays of the formulation against T. cinnabarinus continuously increased during the experiment, but for curcuma oil almost no longer increase observed when the exposure time went beyond 24 h. Moreover, compared with curcuma oil (LC 50 = 0.716%), the spray bioassay of the formulation (LC 50 = 0.035%) was stronger against T. cinnabarinus. The repellency of the formulation to T. cinnabarinus was stronger with increasing exposure time, but that of curcuma oil declined after 12 h of exposure. The mobile distance of T. cinnabarinus treated with the formulation continuously declined during the experiment but that due to the curcuma oil almost no longer declined when the treatment time reached 12 h. The maximum mobile frequency of T. cinnabarinus treated by curcuma oil and the formulation was recorded at 6 h and 12 h, respectively. Thus, the formulation is a promising candidate as a botanical acaricide of green vegetables.

Nonlinear structural model updating based on the Deep Belief Network

Ye Mo,Zuo-Cai Wang,Genda Chen,Ya-Jie Ding,Bi Ge 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.5

In this paper, a nonlinear structural model updating methodology based on the Deep Belief Network (DBN) is proposed. Firstly, the instantaneous parameters of the vibration responses are obtained by the discrete analytical mode decomposition (DAMD) method and the Hilbert transform (HT). The instantaneous parameters are regarded as the independent variables, and the nonlinear model parameters are considered as the dependent variables. Then the DBN is utilized for approximating the nonlinear mapping relationship between them. At last, the instantaneous parameters of the measured vibration responses are fed into the well-trained DBN. Owing to the strong learning and generalization abilities of the DBN, the updated nonlinear model parameters can be directly estimated. Two nonlinear shear-type structure models under two types of excitation and various noise levels are adopted as numerical simulations to validate the effectiveness of the proposed approach. The nonlinear properties of the structure model are simulated via the hysteretic parameters of a Bouc-Wen model and a Giuffré- Menegotto-Pinto model, respectively. Besides, the proposed approach is verified by a three-story shear-type frame with a piezoelectric friction damper (PFD). Simulated and experimental results suggest that the nonlinear model updating approach has high computational efficiency and precision.

Internal force monitoring design of long span bridges based on ultimate bearing capacity ratios of structural components

Hu, Ke,Xie, Zheng,Wang, Zuo-Cai,Ren, Wei-Xin,Chen, Lei-Ke Techno-Press 2018 Structural monitoring and maintenance Vol.5 No.1

In order to provide a novel strategy for long-span bridge health monitoring system design, this paper proposes a novel ultimate bearing capacity ratios based bridge internal force monitoring design method. The bridge ultimate bearing capacity analysis theories are briefly described. Then, based on the ultimate bearing capacity of the structural component, the component ultimate bearing capacity ratio, the uniformity of ultimate bearing capacity ratio, and the reference of component ultimate bearing capacity ratio are defined. Based on the defined indices, the high bearing components can then be found, and the internal force monitoring system can be designed. Finally, the proposed method is applied to the bridge health monitoring system design of the second highway bridge of Wuhu Yangtze river. Through the ultimate bearing capacity analysis of the bridge in eight load conditions, the high bearing components are found based on the proposed method. The bridge internal force monitoring system is then preliminary designed. The results show that the proposed method can provide quantitative criteria for sensors layout. The monitoring components based on the proposed method are consistent with the actual failure process of the bridge, and can reduce the monitoring of low bearing components. For the second highway bridge of Wuhu Yangtze river, only 59 components are designed to be monitored their internal forces. Therefore, the bridge internal force monitoring system based on the ultimate bearing capacity ratio can decrease the number of monitored components and the cost of the whole monitoring system.