Research on the Detection of the Broken Wire Damage of a Cable in the Circumferential Directions Based on Self-magnetic Flux Leakage

Yinghao Qu,Jianting Zhou,Renming Liu,Leng Liao,Qingyuan Zhao 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.3

For large section members such as cables, there are insufficient methods for circumferential scanning along the cable sections for the detection of corroded broken wires. In this study, a detection method for broken wire damage (BWD) along the circumferential direction of cable based on the principle of self-magnetic flux leakage (SMFL) was proposed. First, the theoretical calculation model and the finite element model of the circumferential magnetic field in the polar coordinate system were established. The analysis results showed that the position of the BWD on the section of cable could be effectively judged by the concave position of the curves of the SMFL in the polar coordinate system. Through the circumferential scanning at different positions, the length of the BWD could be judged by the coordinates of x when the value of index “C” (similarity to circle) approached 1 for the first time in the x - C curves. Finally, the detection experiment for the BWD of a parallel wire bundle was carried out. The experimental results were consistent with the analysis results for the theoretical model and the finite element, and the experimental results verified the correctness of the detection method.

Stayed Buckle Cable Recycling for Seismic Upgrading of Super-long-span Concrete Filled Steel Tube Arch Bridges

Dan Ye,Jianting Zhou,Ruijie Zhang,Lueqin Xu,Shuangshuang Jin 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2

A seismic upgrading approach for super-large-span upper-deck concrete-filled steel tube arch bridges using the stayed buckle cables (SBCs, which are temporary facilities for construction of long-span arch bridges) was proposed. The arrangement of SBCs most beneficial to the seismic resistance of arch bridges was determined. The results show that the reasonable arrangement of SBCs can achieve significant seismic performance improvement, reduce the stress demand on the diagonal of the arch rib, and improve the capacity-demand ratios of the weak sections of the arch rib. In upgrading model, the max displacement response of the structure is decreased by 41.3%, the max tensile stress on the diagonal is decreased by 30.1%, the max compression stress demand on the diagonal decreased by 18.0%, the CDRs of sections of the arch ribs are greatly improved.

Experimental Research on Fatigue Damage of Reinforced Concrete Rectangular Beam

Fangping Liu,Jianting Zhou 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.9

In order to acquire the law of the fatigue damage development of reinforced concrete rectangular beams, the ultimate load carrying capacity of a tested beam was measured through the static loading test. The carrying capacity of the beam was then taken as the basis of loading amplitudes for the fatigue tests and the constant amplitude fatigue loading tests under different load levels were carried out for another three beams. The experimental results show that the crack in the beam is composed of the oblique crack in the bending shear section and the vertical crack in the pure bending section. The fatigue cracks are symmetrically distributed along the length direction, and the two sides are basically the same. The fatigue fracture of the test beam occurs in one main cracks located in the middle section of the span. According to the crack width, height and the number of cracks, the whole fatigue test process can be roughly divided into three stages, that is, the rapid development stage, the stable stage and the failure stage. The development of the deflection of the beam and the strain increment of the steel bar and the concrete increased significantly at the beginning of the fatigue cycle; with the increase of cycle number of fatigue load, the growth rate slowed down and entered a relatively stable stage of development; as fatigue destruction gets nearer, the speed became great again. The stiffness of the beam has a relatively large decrease at the beginning of the fatigue loading. In the middle of a longer period of time, it is basically in a linear decline phase. Before the failure, the stiffness decreases greatly. Overall, the stiffness degradation of the beam shows a more obvious monotonic decreasing “S” curve. In a word, many aspects reflect that the fatigue damage of reinforced concrete rectangular beam has obvious three stages damage law. In the early and later stages of fatigue test, the damage is developing rapidly; and in the intermediate stage of fatigue test, the damage development is relatively stable.

Autoregressive Model-Based Structural Damage Identification and Localization Using Convolutional Neural Networks

Qizhi Tang,Jianting Zhou,Jingzhou Xin,Siyu Zhao,Yingxin Zhou 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.7

Traditional autoregressive (AR) model-based damage identification methods construct structural damage sensitive features by trial and error, which are time-consuming, laborious and may lead to poor recognition effect. This study applies convolutional neural networks (CNNs) to quickly and automatically extract high-dimensional features of autoregressive model coefficients (ARMCs). In this research, AR model was utilized to fit the acceleration time series. The input matrices marked with damage location were produced by ARMCs, and then those matrices were sent to the proposed CNN for training. The trained CNN was employed for damage identification and localization. The effectiveness of the proposed method was verified by the damage identification and localization of a three-storied frame structure. The performance of the proposed CNN was compared with multilayer perception (MLP), random forest, and support vector machine (SVM). Meanwhile, the prediction results from different sample types were also discussed. Furthermore, parametric study in relation to the number of accelerometers and ARMCs used is conducted. These analyses demonstrate that the accuracy of CNN tests results reach 100%, 6.67%, 20%, and 25% higher than that of MLP, random forest, and SVM, respectively. Besides, other metrics calculated in this paper (e.g., precision, recall) further indicate that the proposed CNN performs well. The combination of AR and CNN does show excellent performance in damage identification and localization, which seems to be able to resist external excitation changes and accurately identify the multi-location damage and minor damage using limited accelerometers and ARMCs.

Experimental Study on Corrosion of Unstressed Steel Strand based on Metal Magnetic Memory

Runchuan Xia,Jianting Zhou,Hong Zhang,Daoliang Zhou,Zeyu Zhang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

Aimed at the corrosion problem of the commonly used steel strand in the structure engineering, the Metal Magnetic Memory (MMM) was adopted as the non-destructive detection method in this paper. Firstly, based on the magnetic dipole model, the theoretical equations of the Self-Magnetic Flux Leakage (SMFL) for the trapezoidal corrosion section were derived, and the trend of the SMFL was depicted by the software of MATLAB. Then, the experiment of the corrosion detection for the unstressed steel strand based on the MMM was carried out. Ultimately, combined with the above theoretical model, the experimental data were analyzed. The results show that the corrosion of steel material can be relatively precisely calculated by the Faraday's first law of electrolysis. Via the horizontal scanning, the length of the corrosion region can be effectively obtained by the intersections of the x-Bx curves, and the theoretical model is verified. And via the vertical scanning, the inverse point x-z curve presents an inverted U-shape for the corroded steel strand and becomes a new means to determine the range of the corrosion areas. The findings have extensive prospectsfor the non-destructive detection in civil engineering.

Design and Experiment of an Automatic Temperature Control Device of Composite Shape-Stabilized Phase Change Material for Concrete Box Bridges

Zhen Wang,Jianting Zhou,Leng Liao,Jinquan Zhang,Huabin Zhang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.2

To solve the problem of bridge surface cracking caused by an uneven temperature field inside and outside the web of a concrete box structure, an automatic temperature control device applied to the beam surface of a concrete box bridge in the daytime is developed. The device, hanging on the surface of the box girder webs, consists of a radiation cooling coating and a composite shape-stabilized phase change material. With reference to a bridge in Guizhou Province, finite element analysis, short-term temperature monitoring and temperature-drop monitoring are carried out using the device. The result shows that the automatic temperature control device works well continuously. For a box girder without an automatic temperature control device, the inside and outside of the web demonstrate different sensitivities to the temperature of the external environment, with a high temperature fluctuation and a relatively high temperature stress. For a box girder with an automatic temperature control device, as the cooling coating reflects part of the solar radiation and the phase transformation of the composite shape-stabilized phase change material releases or absorbs part of the latent heat to or from the external environment, the temperature fluctuation and temperature stress of the inside and outside of the web are relatively small. When the temperature suddenly drops, the automatic temperature control device works better than under conventional weather conditions because it can reduce the external temperature by approximately 50% on the outer surface of the box girder webs.

Quantitative Detection of Corroded Reinforced Concrete of Different Sizes Based on SMFL

Mao Yang,Jianting Zhou,Qingyuan Zhao,Qianwen Xia,Hong Zhang,Lifeng Wang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1

In order to solve the problem of quantitative detection of corroded reinforced concrete of different sizes, the quantitative detection experiment based on spontaneous magnetic flux leakage (SMFL) was carried out in batches. Electrochemical corrosion of 27 reinforced concrete specimens was carried out, and the SMFL signals of reinforcement were obtained by magnetic detection equipment. Four-dimensional magnetic indicators M1-M4 that can characterize the corrosion degree of the specimens were defined. The influence of different sizes on the magnetic indicators were analyzed. It is concluded that the thicknesses of the concrete covers affect the magnetic indicators by affecting the lift-off heights z. The influence of diameter of the rebars on the quantitative detection can be eliminated by describing the corrosion degree with the average cross-section loss rate α. The influence of length of the rebars on quantitative detection is not clear yet. Finally, Support Vector Machine (SVM) was introduced to establish a classification model of corrosion classes and magnetic indicators. Using the model to predict the corrosion classes of the specimens can achieve a high classification accuracy. The research provides a new method for the quantitative detection of steel corrosion.

A Numerical-Experimental Framework to Separate the Effects of Different Turbulence Components on the Buffeting Forces of Bluff-body Structures

Bo Wu,Jianting Zhou,Jingzhou Xin,Hong Zhang,Fengbo Wu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8

In conventional buffeting analyses of flexible civil engineering structures, the differencesbetween the effects of longitudinal (u-) and vertical (w-) turbulence components were usuallyignored. This assumption could cause unpredictable errors and needs to be refined. Toimprove the accuracy of buffeting analyses, this paper proposes a framework combiningComputational Fluid Dynamics simulation and wind tunnel test to analyze the buffeting forcesconsidering the differences between turbulence components. First, the Aerodynamic AdmittanceFunctions (AAFs) with respect to u- and w- turbulence are numerically evaluated. Next, thetotal buffeting forces are experimentally measured. Finally, the numerical and experimentalresults are combined following a theoretical scheme to separate the effects of u- and wturbulence. Results show that u- and w- turbulence have different contributions to the buffetingforces, directly indicating the inaccuracy of the conventional assumption. In the turbulencefield investigated, the buffeting lift force at zero angle of attack (AoA) are all contributed fromthe w-turbulence, while the contribution from u-turbulence increase as AoA increases. Thisnumerical-experimental framework overcomes the limitations of the conventional method byquantitatively describing the different contributions of u- and w- turbulence.

A New Method for Separating Temperature Effect of Bridge Strain Monitoring

Lei Huang,Jingzhou Xin,Jiafeng Yang,Shuangjiang Li,Jianting Zhou 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8

Temperature has a significant influence on bridge strain monitoring data. To improve the accuracy of temperature effect separation in strain monitoring data, this paper proposes a temperature effect separation method comprising variational nonlinear chirp mode decomposition (VNCMD), principal component analysis (PCA) and blind source separation. Firstly, VNCMD was used to decompose the monitoring data of strain and temperature, and the intrinsic mode functions (IMF) of strain and temperature signals were obtained. Secondly, PCA was used to reduce the dimension of IMF, and the false components were eliminated to select the optimal components. After reducing the dimension, the components were used as the input of fast independent component analysis model for blind source separation. Finally, the feasibility and accuracy of the method was verified via the signal-to-noise ratio (SNR) in the simulated signal, and the separation results were evaluated using the Pearson correlation coefficient between the strain component and the corresponding temperature component in real bridge monitoring data. The proposed method performed better than the empirical mode decomposition (EMD) method. The signal-to-noise ratio (SNR) of VNCMD improved 51.80% for daily temperature difference effect and 32.41% for annual temperature difference effect in the numerical study, respectively; the correlation coefficients of VNCMD improved 52.90% for daily temperature difference effect and 4.26% for annual temperature difference effect in practical verification, respectively.