Seismic Damage Indexes of a High Arch Dam Based on the Monolith

Jianyun Chen,Lijun Qin,Qiang Xu,Jing Li 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.7

To assess safety of a dam in an earthquake, establishing the performance evaluation index of the arch dam is significant. The finite-element model based on the 289 m-high Baihetan Dam in Southwest China is taken as a case for seismic response analysis, in which the radiation damping of infinite foundation and opening of contraction joints are taken into consideration. Using the incremental dynamic analysis (IDA) approach, a three-component earthquake scaled to 12 increasing intensity levels is applied to the model, and the seismic response of the model is analysed. In this paper, it is proposed to study the damage based on the monolith, so the monolith damage volume ratio and monolith damage area ratio are suggested to determine the most severe part of the dam. Meanwhile, to help identifying the damage of the dam, the response results of contraction joints are extracted to analyse the potential relationship between the proposed indexes, providing a reference for exploring new detection indexes and damage evaluation indexes. In order to explore the possibility of the simplified layout of dam damage monitoring, the dam body is partitioned according to the results of monolith damage development.

Study on the Influence of Variation of Contact Arc Zone on the Single-Pass Sawing of Sapphire Wafer

Jianyun Shen,Lang Lu,Yuanyuan Gong,Xipeng Xu 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.9

Single-pass sawing (SPS), a significant cutting process widely used in the manufacturing of optical components in optoelectronic fields, which can greatly improve the quality of products by reducing the proportion of edge chipping. In this paper, the mechanism of SPS was introduced by a novel approach of deep analysis of the variation of the contact arc zone. Setting sapphire wafers as the workpiece, this study performed the comparative experiments in three specific arc zones, which would further make a thorough inquiry on the related machining mechanism. The difficulty degree of machining and the topography of surface quality during SPS process were also analyzed. The difficulty degree of machining was reflected by the sawing force ratio, and the machining surfaces of sapphire wafers were compared by SEM and Digital Microscope. The results indicate that the lower the arc is, the easier it can be machined during SPS. And the best surface quality appears in Arc 2 (arc angle = 20°), which can be set as an excellent reference for the machining of other materials during SPS. The single-pass sawing mechanism is also derived on the basis of the traditional cutting mechanism model, which will further serve as useful references to both the industrial machining and the academia.

Exploration on Damage Mechanism and Equivalent Damage Model of High Arch Dams under Earthquakes

Jianyun Chen,Xiangyu Cao,Qiang Xu,Jing Li 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4

Damage identification technology of high arch dams has been well developed under strong earthquakes. However, the failure mechanism of high arch dams at different locations remains unclear. For this purpose, a series of deterministic dynamic analyses for a 3D 289-m-high arch dam based on concrete damaged plasticity constitutive model are performed. The failure mechanism at different locations of high arch dams under earthquakes is studied systematically. According to the sensitivity of different indicators to different damaged positions, an effective sensor placement scheme is proposed to assess the seismic reliability in practical engineering. Furthermore, a new effective equivalent damage model based on prior information is proposed, which can improve the efficiency of damage identification, as well as solving the problem that the real damage is concealed by homogenizing the damage in a pre-set region. The results provide suggestions and theoretical basis for sensor placement in actual monitoring of high arch dams; and the equivalent damage model provides a new solution to balance the efficiency and accuracy of damage identification.

Dynamic Analysis of AP1000 Shield Building Considering Fluid and Structure Interaction Effects

Xu, Qiang,Chen, Jianyun,Zhang, Chaobi,Li, Jing,Zhao, Chunfeng Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.1

The shield building of AP1000 was designed to protect the steel containment vessel of the nuclear reactor. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as an earthquake. The aim of this paper is to study the effect of water in the water tank on the response of the AP1000 shield building when subjected to three-dimensional seismic ground acceleration. The smoothed particle hydrodynamics method (SPH) and finite element method (FEM) coupling method is used to numerically simulate the fluid and structure interaction (FSI) between water in the water tank and the AP1000 shield building. Then the grid convergence of FEM and SPH for the AP1000 shield building is analyzed. Next the modal analysis of the AP1000 shield building with various water levels (WLs) in the water tank is taken. Meanwhile, the pressure due to sloshing and oscillation of the water in the gravity drain water tank is studied. The influences of the height of water in the water tank on the time history of acceleration of the AP1000 shield building are discussed, as well as the distributions of amplification, acceleration, displacement, and stresses of the AP1000 shield building. Research on the relationship between the WLs in the water tank and the response spectrums of the structure are also taken. The results show that the high WL in the water tank can limit the vibration of the AP1000 shield building and can more efficiently dissipate the kinetic energy of the AP1000 shield building by fluid-structure interaction.

Numerical Simulation Analysis of Damage Mode of Concrete Gravity Dam under Close-in Explosion

Jianyun Chen,Xiaopeng Liu,Qiang Xu 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

The study of damage mode of a concrete gravity dam under close-in explosive impact is a critical issue to assess the dam’s antiknock security. In this paper, a fluid-structure coupled finite element numerical method with combination of Lagrangian and Eulerian algorithm is applied, taking into consideration the damage development process of the Huangdeng concrete gravity dam. The damage mode of a square reinforced concrete slab under close-in blast loads has been simulated and discussed as a comparison with real experiment to verify the feasibility of the numerical simulation. The influence of the presence of spillway tunnel on damage mode of the concrete gravity dam has been investigated. Different damage modes of the concrete gravity dam are compared and studied for different standoff distances and different detonation depths. The damage process of the dam with time course is researched. The influence of different mediums, where the explosion occurs, on the failure mode of the dam is also researched. The analysis results show that attention should be paid to the concrete gravity dam subjected to close-in upstream shallow underwater blasts. It also should be focused on that the presence of spillway tunnel can affect the damage result of the dam.

Dynamic Analysis of AP1000 Shield Building Considering Fluid and Structure Interaction Effects

Qiang Xu,Jianyun Chen,CHAOBI ZHANG,Jing Li,Chunfeng Zhao 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.1

The shield building of AP1000 was designed to protect the steel containment vessel of thenuclear reactor. Therefore, the safety and integrity must be ensured during the plant life inany conditions such as an earthquake. The aim of this paper is to study the effect of waterin the water tank on the response of the AP1000 shield building when subjected to threedimensionalseismic ground acceleration. The smoothed particle hydrodynamics method(SPH) and finite element method (FEM) coupling method is used to numerically simulatethe fluid and structure interaction (FSI) between water in the water tank and the AP1000shield building. Then the grid convergence of FEM and SPH for the AP1000 shield building isanalyzed. Next the modal analysis of the AP1000 shield building with various water levels(WLs) in the water tank is taken. Meanwhile, the pressure due to sloshing and oscillation ofthe water in the gravity drain water tank is studied. The influences of the height of water inthe water tank on the time history of acceleration of the AP1000 shield building are discussed,as well as the distributions of amplification, acceleration, displacement, andstresses of the AP1000 shield building. Research on the relationship between the WLs in thewater tank and the response spectrums of the structure are also taken. The results showthat the high WL in the water tank can limit the vibration of the AP1000 shield building andcan more efficiently dissipate the kinetic energy of the AP1000 shield building by fluidstructureinteraction.

An ABC-BP-ANN Algorithm for Semi-active Control for Magnetorheological Damper

Qiang Xu,Jianyun Chen,Xiaopeng Liu,Jing Li,Chenyang Yuan 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.6

The Magnetorheological (MR) damper is one of the most popular semi-active devices, which uses MR fluids to produce controllable dampers. In this work, the Back-propagation (BP) Artificial Neural Network (ANN) optimized by the Artificial Bee Colony (ABC) algorithm (ABC-BP-ANN) is proposed to obtain the required voltage for semi-active control of MR damper simulated by Spencer model. It is found that the control-forces of MR damper are close to the results of active control algorithms such as the conventional Linear Quadratic Regulator (LQR) control algorithm. The initial weights and the thresholds of BP-ANN are regarded as solutions; the training errors of BP-ANN are used for the cost function and ABC algorithm is used to optimize the initial weights and the thresholds of BP-ANN. The proposed model uses the Spencer model to calculate the train samples to train proposed ABC-BP-ANN model. The proposed ABC-BP-ANN model predicts the voltage based on the results of control-force calculated by LQR model. Several numerical examples are used to verify the proposed model. The results show that the control-forces of MR damper calculated by proposed model are close to those calculated by LQR algorithm. The proposed ABC-BP-ANN inversion algorithm for obtaining the voltage for MR damper has greater computational efficiency and higher accuracy than the conventional BP-ANN algorithm.

One-pot synthesis of electron-acceptor composite enables efficient fullerene-free ternary organic solar cells

Zhang, Jianyun,Liu, Wenrui,Chen, Shanshan,Xu, Shengjie,Yang, Changduk,Zhu, Xiaozhang The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.45

<P>An effective strategy of “synthesizing an electron-acceptor composite (ZITI-m) by one-pot reaction” to improve photovoltaic performance is proposed. The ZITI-m composite is synthesized by one-pot Knoevenagel reaction of ZIT-2CHO and a mixture of INCN-2F and I-a, from which asymmetrical ZITI-3F and symmetrical ZITI-4F are separated. J71:ZITI-m-based OSC shows the highest PCE of 13.65 ± 0.13% with remarkable PCE of 13.85% than those based on J71:ZITI-3F (12.97 ± 0.15%) and J71:ZITI-4F (13.02 ± 0.13%) blends. The effect of acceptor ratio in the composite on OPV performance indicates that all PCEs of composite system are higher than those of the materials based on pure acceptors with a broad composition tolerance, which is ascribed to the synergistic effect of the ternary blend system.</P>

MECHANICAL PROPERTIES OF TWO-WAY DIFFERENT CONFIGURATIONS OF PRESTRESSED CONCRETE MEMBERS SUBJECTED TO AXIAL LOADING

CHAOBI ZHANG,Jianyun Chen,Qiang Xu,Jing Li 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.5

In order to analyze the mechanical properties of two-way different configurations of prestressedconcrete members subjected to axial loading, a finite element model based on thenuclear power plant containments is demonstrated. This model takes into account theinfluences of different principal stress directions, the uniaxial or biaxial loading, andbiaxial loading ratio. The displacement-controlled load is applied to obtain the stressestrain response. The simulated results indicate that the differences of principal stressaxes have great effects on the stressestrain response under uniaxial loading. When thespecimens are subjected to biaxial loading, the change trend of stress with the increase ofloading ratio is obviously different along different layout directions. In addition, correlationexperiments and finite element analyses were conducted to verify the validity and reliabilityof the analysis in this study.

Research on the Influence Factors of Thermal Cracking in Mass Concrete by Model Experiments

Xianzheng Yu,Jianyun Chen,Qiang Xu,Zhi Zhou 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8

Thermal cracking has significant impact on the safety and durability of mass concrete. This paper aims to find the reason forcracking of a prototype bridge structure and consider which influencing factors are the most important. For this model experimentson mass concrete in bridge structures were designed and conducted and thermally cracking was induced. Fiber bragg grating sensorswere used to monitor the temperature and strain within concrete in real time, as well as the strain around the embedded cooling pipes. Thermal properties of concrete were deduced from these monitoring data and then used in the numerical analyses to verity thecalculation accuracy. In the context of engineering practice, the primary influencing factors on the cracking of mass concrete wereinvestigated by numerical analyses. The optimized temperature control methods were proposed to prevent the occurrence of thermalcracking of mass concrete.