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Advanced Engineering Science

Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-14-11-2021-91
Total View : 19

Abstract :

Pipe jacking synchronous grouting is an important method to reduce formation disturbance and final settlement. In order to obtain the relationship between the grouting pressure and the final settlement, find out the reasonable grouting pressure and grouting amount in the actual project to reduce the disturbance of the surrounding stratum, and provide theoretical and experimental supports for the improvements of the synchronous grouting technology, the stratum–mud interaction and the mechanism of settlement from the perspective of the structural characteristics of soil particles and bentonite molecules were analyzed, theoretical assumptions for the four stages of settlement were put forward. Then, the geotechnical engineering centrifuges and self-developed pipe jacking projects were used to simulate the pipe jacking under different grouting pressures on-site. Through the comparative analyses of the settlement curves, the conclusions of the theoretical analysis part were verified. Finally, the relevant parameters such as the grouting pressure in the experiment were applied to the pipe jacking project in Suzhou Donghui Park and the settlement measurement points were arranged on-site, further verified the conclusions. Researches showed that the settlement after grouting can be divided into four stages: soil collapse stage, seepage loss stage, mud skin formation stage and grout uplift stage. The soil collapse stage was short and the settlement speed was fast. Seepage loss stage lasted for a long time and the total settlement was large, which was the main part of the formation settlement. At the mud skin formation stage, the bentonite molecules accumulated on the mud–stratum contact surface to form mud skin, and the slurry was not permeated into the stratum and the settlement of the stratum slowed down. Finally, at the grout uplift stage, the grouting pressure of the mud acted on the mud skin to push the overlying soil and produce settlement compensation. The size of grouting pressure and grouting amount had a great influence on the final settlement. Small grouting pressure and grouting amount would increase the settlement caused by soil collapse and seepage loss, while large grouting pressure would cause excessive settlement compensation effect, even could cause surface uplift. Selecting a reasonable grouting pressure and grouting amount was very important and effective for controlling stratum settlement. It could be used in various pipe jacking projects on-site.

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Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-14-11-2021-90
Total View : 9

Abstract :

An active control method of trailing edge flap is investigated for suppressing high frequency vibration of wind turbine blades. The structure is modeled as composite blade beam with circumferentially asymmetric stiffness (CAS) configuration, which is based on the analysis of the elastic flap-wise/twist displacements and incorporates the angle control of trailing-edge flap driven by a stepping motor. Aerodynamic expressions of the aeroelastic system are based on a novel quasi-steady model suitable for trailing-edge flap. The partial differential aeroelastic equations of the aeroelastic system are solved based on the discretization function of Galerkin method. The high-frequency vibration of the blade is successfully suppressed by the active control based on the swing angle of the trailing-edge flap. The active control is realized by H∞ algorithm using linear matrix inequality (LMI) design and state observer design. Time-domain stability analysis and robust control method is investigated to realize displacement response analysis and robust performance analysis, and input signal display of trailing-edge flap angle. The optimization is investigated to mechanism of LMI is to optimize uncertain robust performance parameters based on the selection of robust control parameters, so that the controlled displacement and control input are kept within reasonable ranges. In order to reduce the influence of state variable detection error in full state feedback, state reconstruction and state observer are used to improve the control performance. At the same time, the reliability and robustness of H∞ control algorithm based on LMI are verified by comparisons of the results of high-frequency vibration control using different robust performance parameters and different wind speeds. Based on a real-time OPC technology of S7–300 PLC and WinCC configuration software, a process control experiment is adopted to verify the feasibility of the control algorithm in the engineering application. A real-time engineering application feasibility scheme is provided for the control method that cannot be conventionally implemented in the controller hardware due to the complexity of the intelligent control algorithm.

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Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-14-11-2021-89
Total View : 3

Abstract :

Hysteresis is one of the important characteristics of automatic adjustment of river system, while there are few studies on the law of sediment delayed response in the Three Gorges Reservoir (TGR). Based on the delayed response model, the measured data were analyzed and the delayed response model was modified by considering the sediment concentration and sediment particle size in order to construct the delayed response model in accordance with the characteristic of sediment deposition in TGR. Firstly, the changes of water and sediment conditions and sediment deposition characteristics since the impoundment of TGR were counted, and the influence of cascade reservoirs in the upper Yangtze River was analyzed. In order to simulate and analyze the sedimentation delayed response law in different periods of TGR, the existing model was used and modified. Based on the existing and modified response model simulation results, it can be seen that 1) The modified response model can better simulate the sediment deposition process of TGR after the impoundment of cascade reservoirs because of the consideration of sediment concentration and sediment particle size. 2) After the impoundment of cascade reservoirs, the fluctuation range of inflow and sediment decreases, the sediment inflow of TGR is more concentrated in flood season, both of which make the channel adjustment rate increase, the delayed response time of sediment deposition in TGR is shortened from the early 4 years to the early 3 years. 3) After the impoundment of cascade reservoirs, the influence weight of sediment concentration on the sediment deposition process increases, while the influence weight of flow and water level in front of dam decreases. By using the modified model, it can be seen that the inflow of sediment concentrates more in the flood season, which make the delayed response time of sedimentation in TGR shorten, and the influence weight of sediment on the sediment deposition increases.

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Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-14-11-2021-88
Total View : 1

Abstract :

Onshore ground motions were widely used for seismic analysis of sea-crossing bridges, and the difference between the onshore and offshore ground motions were ignored. Due to soil loss around piles scoured by water for a long time, the stability of substructure of bridge in marine environment was reduced. Taking an approach part of a sea-crossing bridge as an example, a finite element model for this approach part was built by using the ABAQUS software. The pile-soil effect and hydro dynamic force were considered in the model. The probabilistic seismic demand analysis method was used with the fragility analysis of bridge piers under onshore and offshore ground motions with different scour conditions. By drawing the transcendence probability vulnerability curves and the transcendence probability increase diagrams of piers and bearings, the damage regularities of bridges under the onshore and offshore ground motions and different scour depths of bridges key components were studied. The results showed that the bridge piers were more vulnerable under offshore motions than that under onshore motions. With the increase of the local soil scour depth, the failure probability of the bridge piers and bearings increased. The effect of scour depth had a more obvious effect on the failure exceeding probability of the piers. The failure exceeding probability of the piers in bridge longitudinal direction was higher than that in bridge transverse direction under the same intensity of ground motion. The bearings were more vulnerable than bridge piers under the same working conditions. The increase of failure exceeding probability of the bearings under the offshore motions was also generally higher than that under the onshore. As the scour depth increased, the failure exceeding probability of the bearing gradually increased. Comparing with the onshore motions, the scour depth had a more obvious influence on the failure exceeding probability of bridge piers under the offshore motions with the increase of the ground motion intensity.

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Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-14-11-2021-87
Total View : 2

Abstract :

As the basic part of motion of humanoid robots, human-like motion planning of the anthropomorphic arm is always one of the research hotspots and difficulties. A novel human-like motion planning method based on movement primitives was proposed. This method can satisfy the feature of arm motion and improve the accuracy. Firstly, the arm structure was decoupled and the arm model was built to express different arm movements. The methods of extraction and connection about movement primitives were established. The mapping relations between the arm models and inverse kinematic (IK) solutions were established. Meanwhile, a motion framework was proposed. The joint trajectories of a certain platform can be generated to accomplish required tasks with this motion framework. Secondly, according to the motion features of different movement primitives, the associated Human Performance Measures for different movement primitives were constructed to solve the IK problem. Finally, the proposed method was verified by the similarity experiment and the human-like movement experiment for the general motion of humanoid robot NAO. In the similarity experiment, the robot NAO generated the human-like movements with the proposed method. The motion data were compared with the real data generated by humans. All the errors were less than 1 cm, which satisfied the accuracy requirements of human-like movements. In the human-like movement experiment, the robot NAO performed a human-like arm movement with the proposed method. The proposed method was also compared with the minimum total potential energy method and the last norm algorithm. Using the proposed method, 7% and 58 % increase in similarity were achieved respectively, compared with those two methods. With the proposed method, the complex motion models were decoupled into different simple sub-movements and the classification of the movements reduced the calculation amount. The experiments proved that the anthropomorphic arm can generate human-like movements accurately.

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