2021 volumne 42卷 Issue 02
SONG Danqing1, DONG Lihu2, CHEN Zhuo3, DU Han4
Abstract: The large homogeneous rock slopes were taken as the research object.Two 3D FEM numerical models were established, the modal analysis of rock slope was carried out by the FEM. The natural frequency of the slopes and the corresponding vibration modes were obtained. The relationship between the dynamic response characteristics of the slopes and their inherent mode was studied in the small strain range. The results showed that the natural frequency of the slopes increased with the order, and the slope had the typical slope elevation and surface dynamic amplification effect. The gradient changes of the slope surface had a great influence on the natural frequencies and vibration modes of the slopes. Low-order (1st and 2nd order) natural frequencies mainly caused the overall deformation of the slopes, while high-order (≥3rd order) natural frequencies mainly caused local deformation of the slope surface. The modes below the fifth order were mainly characterized by a single deformation of bending, stretching or torsion, while those above the fifth order were characterized by a variety of deformation combinations.
ZHAO Bida, CAI Yangzheng, YAO Zeyang
Abstract: To study the out-of-plane bending seismic behavior of Unstiffened circular hollow section (CHS) KK-joints, an out-of-plane bending cyclic loading test was performed. Moreover, the test results of the KK-joints were compared with the existing test results of the corresponding X-joints (with same tubular dimension and material of the KK-joints), to investigate the seismic performance difference between the KK-joints and the X-joints. Additionally, the performance difference was further interpreted by the load-carrying mechanism analysis. The results showed that the failure mode of the KK-joints was chord wall crack after plasticizing, and the resistance decreases slowly after cracking. The energy dissipated of the KK-joints mainly relied on plastic deformation and crack propagation of the chord wall. The ductility ratio of the KK-joints was large than 6, which demonstrated excellent deformability and seismic behavior. It also found that the stress characteristics of the adjacent brace interaction made the out-of-plane flexural strength of KK-joints about 23% lower than that of the corresponding X-joints, but close to the value calculated by the predict equation of CHS X-joints of the EC3 specification. Moreover, the results of load-carrying mechanism analysis and FE analysis showed that the joint-zone of the KK-joints and the X-joints were subjected to tension in the four corners and in two diagonal directions respectively. Therefore, the KK-joints would develop more uniform and extensive plastic at joint-zone than that of X-joints. The comparison of test results between the two type joints also showed that the deformability, ductility, and energy dissipation of the KK-joints were also better than that of the corresponding X-joints.
Zhao Zhuo; Geng Jiashuo; Wang Jianqiang;
Abstract: In order to study the seismic performance of the prefabricated pier connected by Ultra-high performance concrete (UHPC), according to the practical engineering,the finite element model of the prefabricated pier connected by UHPC and the cast-in-place pier have been established by ABAQUS, the seismic performance of the prefabricated pier connected by UHPC and the cast-in-place pier were analyzed. The results showed that the failure process and failure form of the prefabricated pier connected by UHPC were similar to that of the cast-in-place pier, and the seismic performance of the joint between the prefabricated pier bottom and the variable section part should be strengthened. The hysteretic behavior, horizontal equivalent stiffness, energy dissipation, and residual displacement of the prefabricated pier connected by UHPC were basically consistent with the cast-in-place pier, which could satisfy the seismic requirements of the bridge. So UHPC could be used as the filling material for the prefabricated pier joints, which could improve the construction speed by using its good mechanical properties and working performance, thus it could exert the advantages of prefabricated construction technology.
WANG Jingxuan, YANG Yong, SHEN Yajun
Abstract: To study the anti-progressive collapse mechanism and failure characteristics of the CFST frame under the failure of key column, using the ABAQUS/Explicit analysis method,this paper developed a 3D finite element model this paper developed a 3D finite element model of CFST frame considering the full-height infilled walls. The material constitutive model of steel, concrete, infilled wall masonry and the restraint model between different components were selected reasonably.According to the actual working conditions, the horizontal tie-in effect at the end of composite beam was considered, and compared with the experimental data of existing researchers to verify the rationality of the modeling method.On this basis, the load displacement curve of CFST composite plane frame with infilled wall was calculated, and the local failure characteristics of infilled wall were analyzed,and compared with those of CFST composite frame, and the influence of infilled wall on collapse bearing capacity and failure mechanism of CFST frame was analyzed.Results show that, under the vertical load, the whole process stress mechanism of CFST composite plane frame anti-progressive collapse mechanism includes: beam mechanism, catenary mechanism and failure stage;the infilled wall could significantly improve the anti-progressive collapse bearing capacity of the CFST composite frame, the bearing capacity was more obvious in the beam mechanism stage. The bearing capacity of the infilled wall was mainly formed by the diagonal compression brace supporting. Therefore, it was suggested that the role of infill wall should not be ignored in the design of progressive collapse resistance of such structures.
Li Yue; Meng Wenjun; Gao Chongming; Wu Qiqi;
Abstract: In order to obtain the failure evolution law of the reinforced grout anchor connection interface of prefabricated concrete structures,a longitudinal steel bar anchor connection test was carried out on a prefabricated concrete structure by the digital speckle correlation method (DSCM).By observing the failure process of steel bar anchor connection and analyzing the speckle image, the evolution characteristics of the stress of the fabricated concrete structure anchor, the evolution characteristics of the force field of the anchor system, and the evolution characteristics of the strain field of the anchor system were studied.The results showed that: ① The thickness of the anchoring agent would affect the failure mode and the ultimate bearing capacity of the anchoring system. ② In the anchoring system, the pulling force was continuously transmitted along the steel bar from the loaded end to the free end, and the greater the thickness of the anchoring agenthas, the greater the transmission rangeis. ③ During the drawing process, the deformation of the anchoring system was mainly concentrated at the interface between the anchoring agent and the concrete, and expanded along the steel bar to the inside of the system as the load increases. ④ Under the pulling force, in the initial, the first principal strain and the maximum shear strain mainly existed in the grouting area around the reinforcement at the loading end. As the pulling force increased, the strain expanded to the bonding interface between the concrete matrix and the grouting material until it connects with the strain at the bonding interface.
CHEN Weihong1, LIU Fanghao1, QIAO Zehui1, CUI Shuangshuang2
Abstract: In order to examine on the factors to collapse resistance of the structure, the ABAQUS finite element model was firstly verified and calibrated by using the progressive collapse test results of the two-layer concrete plane frame. Then 15 three-story and four-span concrete plane frames were established to carry out the progressive collapse analysis on three parameters based on the verified model. The parameters included the failure of the middle column of the different layers, the reinforcement ratio at the bottom of the beams, and the reinforcement ratio at the top of the beams. The results showed that the lower the floor where the failure of the center column is, the more difficult the catenary action is to play a role. The improvement of the reinforcement ratio at the bottom of the beams had no positive effect on the catenary action. The catenary action of the structure was weakened when the reinforcement ratio was too high. The increase in the reinforcement ratio of the upper part of the beam could significantly enhance the catenary action of the structure. The energy dissipation at the catenary action accounted for at least 70% of the total energy dissipation during the collapse process. Thus, the contribution of the catenary action should be considered when evaluating the structural robustness.
Li Tong; Shiqiang; Wang Xinwu; Ye Chongyang;
Abstract: Pseudo-static cyclic loading tests of a single-layer and single span prefabricated eccentrically braced steel frames were carried out and the test results were simulated by ABAQUS software. On the basis of reasonable results, five finite element models were established. The influence of web openings on seismic behavior of prefabricated eccentrically braced steel frames was analyzed from bearing capacity, stiffness degradation and energy dissipation capacity. The results showed that the opening ratio of web of link had influence on its bearing capacity in the monotonic load, the yield bearing capacity and ultimate bearing capacity of model decreases with the web opening ratio. Under cyclic loading, the initial stiffness of the model decreased with the increased of web opening ratio. The energy consumption capacity of model was not affected obviously by the opening ratio, except for BASE model: the energy consumption coefficients of other models are around 1.55. Appropriate increase of opening ratio could improve the ductility coefficient of the model, however, too large opening ratio would lead to premature failure of the component, which would make the reduction of ductility coefficient.
Li Qingfu; Kuang Yihang; Guo Wei;
Abstract: To apply the concrete stress-strain curve in the concrete structure design code to the ABAQUS concrete plastic damage model, the calculation method of the concrete plastic damage model parameter and the value range of the damage factor were studied, taking a simple supported beam bending test as an example, the truncation of the stress-strain curve of concrete and the value of the damage factor were calibrated. In order to verify the rationality and accuracy of the calculation method of the model parameters and the values in this paper, three sets of specimens including 2 simply supported beams and 1 shear wall were selected for finite element simulation. The results showed that the simulation results and tests of the beam cracking load, ultimate load, load-span deflection curve and shear wall horizontal force-displacement curve were in good agreement and could meet the requirements of engineering accuracy. The truncation of the stress-strain curve of concrete and the value of the damage factor were accurate and reliable.
Yuan Chengfang; Wei Yiran; Li Shuang;
Abstract: The resource utilization of mixed waste concrete and sintered bricks is an important way to solve the problems of urban construction waste stacking and pollution. Based on the mechanical properties test and X-ray computed tomography (XCT) test of polypropylene fiber mixed recycled aggregate concrete, the influence law and mechanism of fiber on the compression and tensile properties of recycled aggregate concrete were studied in depth. The result showed that when the fiber content is 0.6 kg/m3, the compressive strength of recycled aggregate concrete was slightly increased, and when the fiber content was higher, the compressive strength of recycled aggregate concrete was reduced. Polypropylene fiber improved the tensile properties of recycled aggregate concrete. When the fiber content was 1.2 kg/m3, the fiber had the best improvement effect on the splitting tensile performance and bending tensile properties of recycled aggregate concrete. Polypropylene fiber had both positive and negative effects on the mechanical properties of recycled aggregate concrete. It was necessary to consider the reasonable amount of fiber when using it to obtain more excellent performance.
Li Ke; Xu Chaoyang; Wu Kaixin; Wang Xinling;
Abstract: In order to explore the bonding-slip relationship of 600 MPa grade steel with high strength concrete and to provide the theory basis for the application of reinforcing steel bar in concrete structure. The four groups of 42 specimens center drawing tests were conducted to explore the impact of concrete strength, steel bar anchoring length and thickness of concrete cover on the bonding-slip relationship.The results showed that the drawing failure modes of 600 MPa high strength steel bar in high strength concrete included three modes: pull-out failure, concrete splitting failure and steel yield failure.The bond-slip curve of reinforcement pull-out failure included rising section (including micro-slip section, slip section and splitting section), falling section, and residual section.The bond-slip curve of concrete splitting failure only included the ascending section (including micro-slip section, slip section and splitting section);Bond-slip curve of yield failure of steel bar, including rising section (including micro-slip section, slip section) and horizontal section.The ultimate drawing load included with the increase of concrete strength, anchorage length and diameter of steel bar under the condition of no yield failure.Based on the test results, the bond failure characteristics and bond-slip mechanism of 600 MPa steel bar and high-strength concrete were analyzed, and the bond-slip relationship model of 600 MPa steel bar and high-strength concrete under splitting failure condition and the calculation formula of model parameters were proposed. The proposed model and the calculation formula of model parameters were in good agreement with the test results.
HAN Junxuan, SUN Weifeng, ZHAO Ruilian, WANG Weiwei
Abstract: In the process of program repair template mining, due to the noise interference in the historical repair information, the availability of the mined repair template was not strong, and the program repair effect is not good. In order to improve the efficiency of automatic repair. It was an important method use repair templates to repair the program. Therefore, from the perspective of repair template mining and automatic program repair, an improved program automatic repair method is proposed, called APRMT (automatic program repair method based on template mining). APRMT can eliminate the noise of repair information through regular matching, and the accuracy of repair information. According to the location and type of the program defect code to search and repair the information of the defect, the most recent strategy was proposed, which could efficiently use the repair template to repair the program defect. In order to verify the effectiveness of this method, APRMT experimented on 4 open source projects, and the experimental results showed that APRMT successfully fixed 26 defects, with an average time of 3.1 minutes per defect. It can be seen that APRMT can fix more program defects in a shorter time, and therefore improved the effect and efficiency of automatic program repaired.
Peng Jinzhu; Dong Mengchao; Yang Yang;
Abstract: Aiming at the problem of variety and accuracy of gesture recognition in human-computer interaction, a gesture recognition method was proposed based on fusion features of visual histogram of orientation gradient (HOG) and time-domain features of electromyography (EMG), where support vector machine (SVM) was used as a classifier. Visual sensors and smart armbands were used to collect gesture image information and EMG signals respectively, and the corresponding HOG features and time domain features were then extracted after preprocessing. These two features were fused at feature level by employing serial fusion. The combined SVM multiple classifier constructed by one Vs one was used to train and verify the gesture recognition model. Experimental results showed that the overall accuracy of 36 types of gesture recognition models reached 96% by using the proposed fusion features, which is 33% and 16% higher than the single hog feature and EMG time-domain feature before fusion, respectively. Compared with decision-level fusion, the accuracy of the proposed method was increased by 11%, and the calculation time was only 0.274 ms, which could effectively reduce the amount of feature data and significantly improve the accuracy of multiple types of gesture recognition.
Wang Hua; Ma Yadan; Li Shenli; Xu Jing; Xu Mingliang; Zhang Xu; Jin Baohua;
Abstract: Existing erasure animations mainly focused on two-dimensional animations, so they couldn’t be used in three-dimensional scenes directly. Aiming at this problem, a template-based and personalized erasure animation method in three-dimensional scenes was introduced. In our method, firstly, the erasure shape was extracted from the image data and semanticized as a template so that it can be used conveniently in erasure animations. Then the three-dimensional orthographic projection method was used to realize erasure animations. Experimental results showed that our method can realize a real-time animation for various kinds of users’ erasure shape in three-dimensional scenes efficiently.
Chen Yifei; Guo Sheng; Pan Wen’an; Lu Yanhui;
Abstract: Aiming at the target redundancy in reconstruction of certain scenes, in this paper a data fusion method of the camera RGB bitmap and lidar data was employed to solve the problem. In the field of 3D reconstruction, this method of data fusion could eliminate the irrelevant targets in the specific scene and reproduce the three-dimensional scene. The lightweight LeGO-LOAM algorithm was used to extract and match different types of feature points at first, and point clouds were merged at different times to complete the reproduction of the point cloud map. For the irrelevant targets in the constructed point cloud map, with the help of multi-source sensor data and deep learning application technology in the field of computer vision, object detection and elimination are accomplished in three-dimensional space. For the two different processes of point cloud modeling and target detection, the method of point cloud registration was adopted to fuse the algorithm and finally complete the scene reproduction in the campus environment. Experimental results showed that the method based muti-source data fusion could effectively combine the two processes of 3D modeling and object detection. The method proposed in this paper could be applied to smart cities, unmanned driving and other fields, and should have practical application value.
Luo Wen; Sun Benshuang; Liu Shuhan; Chen Jie; Meng General; Li Shurong;
Abstract: The application and properties of ITO ceramic target were seriously affected by its nodulation behavior, it was extremely important to grasp the formation mechanism of nodulation. So the experimental study on the ITO target was carried out by magnetron sputtering technology under different sputtering parameters. The nodulation behavior of target was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the depth of etch ring increased with increasing sputtering time, and then the nodules were formed on the target surface and spread to the etching ring,which reduced the sputtering rate at the edge of etching ring. The nodules were mainly composed of non-stoichiometric ITO, which lacked of O but rich in Sn, and was formed by reverse deposition at low sputtering rate. The nodulation component deviated from its stoichiometric ratio, due to the sputtering difference of Sn atoms in different regions and the O ions were easily formed on target surface. The formation of nodules in the early stage of sputtering was mainly caused by the Sn-rich precipitated particles in In2O3/Sn crystals. And they were easy to accumulate charges and induce arc discharge due to the poor electrical and thermal conductivity, which made them break under the thermal stress. The scattered particles became the new induction points of nodules, resulting in the rapid increase in the coverage of nodules.
Li Weiqing; Zhu Shijie; Sun Yufeng; Guan Shaokang;
Abstract: In this study, Mg-Zn-Y-Nd alloy micro-tubes with an outer diameter of Φ2.46 mm and a wall thickness of 0.14 mm were successfully prepared by secondary hot extrusion, cold drawing and annealing. The outer diameter error, inner diameter error and wall thickness error of the micro-tubes were 0.51 %, 0.32 % and 3. 35 %, respectively. The yield strength, tensile strength and elongation of the drawn micro-tubes were 342.2±10 MPa, 350.4±10 MPa and 0.4±0.2 %. After annealing, the micro-tubes undergo static recrystallization, which resulted in grain refinement, texture weaken and dispersion of the second phase particles. The mechanical properties of the annealed micro-tubes were significantly improved. The yield strength, tensile strength and elongation of the annealed micro-tubes were 245.6±10 MPa, 305.6±10 MPa and 18.2±1.0 %, respectively. Moreover, the fractures of the annealed micro-tubes exhibited typical ductile fracture characteristics.
Ma Feng; Jin Yanxin; Fu Zhen; Xing Haipeng;
Abstract: In order to improve the road performance of asphalt mixture and take into account the good weather resistance, high-speed shearing machine was used to prepare different amounts of SEBS modified asphalt. Various performance indicators were measured and their influence on the road performance of the asphalt mixture was studied. The high temperature, low temperature, water stability and fatigue resistance of SEBS modified asphalt mixture were evaluated by high temperature stability test, low temperature crack resistance test, freeze-thaw splitting and water-immersed Marshall test and four-point bending fatigue test. The test shows that the dynamic stability of asphalt mixture increases with the increase of SEBS content, and the increase is smaller when the dosage exceeds 4% SEBS has a significant effect on improving the low-temperature performance of asphalt mixtures and water stability after freeze-thaw cycles The fatigue life of the post-mixing material is reduced, but the initial stiffness modulus is significantly higher than that of the matrix asphalt. After the secondary fatigue loading self-healing, the late modulus and fatigue life of the modified asphalt mixture are significantly better than the matrix asphalt, and gradually increase with the increase of the dosage, showing excellent self-healing properties
Li Xiaomin; Cao Kan; Li Pengkai; Xu Shanshan; Wu Zongquan;
Abstract: An experimental investigation was carried out on a MILD burner firing biogas, which was developed based on the scheme of rich combustion-injection-MILD (moderate & intense low oxygen dilution) combustion. An analysis was conducted to explore effects of primary biogas ratio and heat transfer ratio of rich combustion chamber on NOx emissions of the burner, with thermal input of 100 kW. Results showed that temperature difference in the MILD combustion chamber was less than 200 ℃ and NOx content in its flue gas was in the range of 0.14 and 1.12 mg/m3. When the primary biogas ratio was in the range of 0.3 and 0.4, secondary dilution was indispensable to achieve MILD combustion. However, when the primary biogas ratio was greater than 0.4, MILD combustion could be realized without secondary dilution. Finally, an expression was obtained through binary regression, which could explain influences of the primary biogas ratio and the heat transfer ratio of the rich combustion chamber on NOx emissions to a great degree.
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