Papers by Author: Jing Zhou

Abstract: A regularization based method of inversely analyzing the material parameters for the gravity dams is presented in this paper. The measured noise of the displacement often leads to the ill-posed solutions of the dam inversion. A least square scheme was adopted for the inverse analysis by using of the displacement measurements, and the L-curve algorithm was proposed to perform the regularization in the inversion computation. The proposed method actually utilizes the sensitivity of the measured displacements with respect to the sub-regional material parameters. Thus a simplified algorithm was developed to calculate the sensitivity coefficients by using the standard finite element procedure. To investigate the effectiveness of the proposed method, the numerical simulations on a concrete gravity dam were carried out. The results demonstrate that the presented method can accurately obtain the material parameters of the dam by using of the inverse analysis, which has the potential for assessing the integrity of the gravity dams.

Abstract: This paper presents the experimental investigations into the seismic failure for high arch dam with shaking table test. The similitude scale of high arch dam was studied firstly. Then we developed a like concrete material to simulate the mechanical behavior of the structural concrete in high arch dam. The shaking table tests have been performed on the scale model. The experimental results reveal the failure process of high arch dam with respect to the different earthquake intensities.

Abstract: The great effort for reducing emissions of CO2 to atmosphere will inevitably involve the carry-out process of Carbon Capture and Storage(CCS), a novel plan which intends to capture and store anthropogenic CO2 produced at many existing industrial sources, such as power stations and petrochemical works. In particular, anthropogenic CO2 pipeline transportation from the energy plant to the remote sequestration area(both onshore and offshore) is a fundamental issue regarding the feasibility of applying the CCS technology. CO2 pipelines have been in operation in USA, Europe and North Africa for almost three decades. However, the technical challenges for pipelines transporting CO2 due to the relevant effects of different impurities coming from flue gases, are still needed to get people to take up, especially for China which is focusing on the roll-out of CCS. This paper will address a FE-based method which can assess residual life of a supercritical CO2 transmission pipeline containing an inner defect induced crack. Specifically, a portion of welded round steel pipeline is selected as the object of our analysis and an ANSYS finite element procedure is generated to simulate the stress state of an element volume along the radial direction and hence to calculate the effective stress due to the effects of crack closure. Afterwards, combining the effective stress we get in the above numeric analysis, the Paris equation is modified to build an integral analysis method for the residual life evaluation of CO2 pipeline. Lastly, in order to verify the validity of the proposed method, a pipeline example in a published paper is used as the benchmark model, the full-scale test results of which are compared with those from our method. Based on this, a section of CO2 pipeline, with an initial defect (assumed as a crack source), is analyzed and its residual life is evaluated by using the presented method. The analysis of numerical results indicates that the method presented in this paper can give us a valuable reference to life-evaluation for CO2 pipeline in CCS.

Abstract: A structural health monitoring system by fiber Bragg grating (FBG) sensing technology was installed on 8 # berthing pier of cylinder caisson in a new 300,000 DWT crude oil berth pier of Dalian Port. The system can realize the timely strain monitoring and timely cumulative damage identification of the structure. By analyzing the monitoring data of 8# cylinder caisson under wave load, this paper gives the strain rules and provides the reference for the safety assessment. The study results also have pratical significance on similar structures’ further research.

Abstract: A methodology of damage identification for the circumferentially cracked pipe is presented by using the quantitative relationship between crack size and reflection characteristics of guided waves. Firstly, the reflection characteristics and mode conversion behavior were theoretically studied by the 3-D finite element (FE) analysis. It is found that the reflection coefficients (RCs) of longitudinal L(0,2) and F(1,3) modes quantitatively is related to the circumferential length and radial depth of the crack. Then we present a novel method to quantitatively identify the crack. The feasibility of the proposed method was numerically investigated. The method only requires the longitudinal excitation mode of guided wave in the pipe, which shows the good potential for real application or in-situ damage monitoring. Introduction

Abstract: The electromechanical impedance (EMI) technique, which employs piezoelectric ceramic (PZT) patches as transducers, is emerging as an effective and powerful technique in structural health monitoring (SHM). This paper presents a novel method to extract the damage-sensitive feature (DSF) for EMI-based SHM. Firstly, the concept of effective drive point (EDP) impedance was introduced briefly. Secondly, a novel DSF was proposed as the ratio of the active parts of EDP admittances before and after damages. Finally, the effectiveness of the proposed DSF was experimentally verified. The results show that the novel method provides a sensitive feature for EMI-based SHM

Abstract: Snaked-lay pipeline is an effective method for control lateral buckling of pipeline, which is used widely. For design of snaked-lay pipeline the key is how to control lateral buckling of pipeline, namely, the lateral buckling is triggered at the designed location, the moment and strain of post buckling are acceptable. A new shape of snaked-lay pipeline is presented. Based on ANSYS, nonlinear finite element of pipeline is built. Comparisons show that the critical buckling load, moment and strain of post-buckling are all reduced for the new shape of snaked-lay pipeline.

Abstract: The part-through circumferential crack is a typical crack form in pipe structure, which often lead to the structure failure. Firstly, the local flexibility equations of a pipe with a part-through circumferential crack are derived by using linearly elastic fracture mechanics. Secondly, an adaptive Simpson quadrature-revisted was used to numerically calculate the local flexibility coefficients. Finally, the model test were performed to validate the local flexibility for a part-through circumferentially cracked pipe. The results show that the natural frequencies of cracked pipe obtained by the model test agree well with the theoretical values from the proposed equations of the local flexibility. It is demonstrated the feasibility of the proposed method for vibtaion analysis and damage identification of a cracked pipe.

Abstract: The structural behavior of an old six-span reinforced concrete arch bridge, which has been in service for about 40 years, is investigated. Field monitoring (inclusive of test of material property, static and dynamic test of the bridge) was conducted, static and dynamic responses of the bridge are obtained. Based on the primitive bridge, a scaled one-span bridge model was fabricated by organic-glasses. Both the static and dynamic tests were executed on the bridge model in the laboratory. Since the arch rib is the crucial member for the arch bridge, 7 notches were cut on both arch ribs of the bridge model to simulate different damages of the arch rib. Mechanical responses of the bridge with different damages on the arch ribs were achieved. FEM analyses were preformed on the bridge as well. Numerical results show good agreement with the experimental results.

Abstract: A novel approach for crack identification based on jointly time-frequency analysis is presented in the paper. A bilinear stiffness model for the breathing crack was introduced to represent the nonlinear dynamics of a cracked beam. The nonlinearity of the dynamic responses due to the crack opening-closing is used to identify the occurrence of the crack. The Wigner-Wille distribution technique is applied to analyze the response signals and the instantaneous frequency is extracted as damage-sensitive feature. The numerical simulations of a breathing crack model were carried out to validate the possibility and effectiveness of the proposed approach. The effects of crack severity and sampling frequency on crack identification were also studied in the simulations respectively. The results show that the proposed method can effectively identify the crack with slight severity without any baseline model or data, and the better the identification obtains as the larger the sampling frequency. The study demonstrates that the proposed approach by using of jointly time-frequency analysis is a promising technique for crack identification.