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Experimental Study of the Wake of Multi-Rotor Turbine

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SSRN 2022年

作者： Xiong, Xue-Lu Laima, Shujin Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin Institute of Technology Harbin150090 China

This paper describes a comparative experimental study of the wake of a multi-rotor turbine and a single-rotor turbine. The wake merge process in the multi-rotor wake is analyzed from various perspectives. A jet-like gap flow region and a momentum redistribution region are found in the region before and after the full merge of the individual rotor wakes, respectively. Compared to the single-rotor wake, the fully merged multi-rotor wake is found to have a slower recovery rate and a lower turbulent kinetic energy. Furthermore, two sources are found for the peak frequency in the multi-rotor wake which results in different peak frequencies at different locations. One of the two sources is the rotor wake meandering with the meandering frequency maintain the same throughout the wake, and another one corresponds to the dynamic of the shear layer in the gap region with its peak frequency decrease in the streamwise direction. The yawed multi-rotor wake is found to be similar to the non-yawed case except for the wake deflection of the yawed case. And the deflection is more pronounced in the yawed multi-rotor wake than in the yawed single-rotor wake which indicates a higher yaw efficiency for the multi-rotor turbine. © 2022, The Authors. All rights reserved.

关键词： Wakes

Enhancing Ultrasonic Flaw Detection by a Nonconvex Sparse Regularization Approach

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SSRN 2023年

作者： Wu, Biao Zhou, Wensong College of Civil Engineering Nanjing Tech University Nanjing211816 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education School of Civil Engineering Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

Ultrasonic testing has been an important tool for the detection of hidden defects in materials yet its effectiveness is usually compromised by the noise originated from both the testing system and the material being evaluated. Motivated by the prior knowledge that only a small number of defects or reflectors exist within the tested material thus the measured signal can be viewed as a linear combination of a few echoes, a novel signal processing method is proposed in this study where a nonconvex sparse regularization method based on lp-norm (0 © 2023, The Authors. All rights reserved.

关键词： Defects

Efficient Two-Stage Strain/Temperature Measurement Method for Botda System Based on Bayesian Uncertainty Quantification

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SSRN 2022年

作者： Meng, Xianghao Zhang, Dongyu Li, Hui Huang, Yong Key Lab of Structures Dynamic Behavior and Control The Ministry of Education School of Civil Engineering Harbin Institute of Technology Harbin China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin China

Brillouin optical time-domain analysis (BOTDA) is an efficient distributed structural strain/temperature measurement technology by identifying the Brillouin frequency (BF) of the fiber. The original BF identification method involves gradually tuning the scanning frequency of the probe laser light, which is time-consuming. To improve the sensing efficiency of BOTDA, a novel two-stage strain/temperature measurement method is proposed based on Bayesian uncertainty quantification. The method uses the information of a small amount of wide range frequency scanning data in the 1st stage to guide a concentrated scanning of the frequency points in the 2nd stage by employing transitional Markov chain Monte Carlo (TMCMC) algorithm. The second-stage scanning strategy based on Bayesian uncertainty quantification ensures the high confidence for BF identification, so that the number of required scanning points can be significantly reduced without sacrificing the measurement accuracy. Finally, the efficacy of the proposed method is verified using numerical and experimental data. © 2022, The Authors. All rights reserved.

关键词： Uncertainty analysis

Experimental and Modelling Investigation on Chloride Transport and Flexural Behaviour of Rc Beams Subjected to Simultaneous Deteriorating Factors of Carbonation, Ft Cycles and Multiple-Type Sustained Stress

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SSRN 2022年

作者： Chen, Dingshi Guo, Wenhua Kang, Jiayuan Shi, Jun School of Civil Engineering Central South University Changsha410075 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education School of Civil Engineering Harbin Institute of Technology Harbin150090 China

Reinforced concrete (RC) structures are often exposed to coinstantaneous deterioration effects such as carbonation, chloride corrosion, freeze-thaw cycles and external loads which causing deterioration of concrete and reinforcement. This paper discussed the effects of carbonation, freeze-thaw cycles and sustained loads on chloride ion transport and proposed a chloride ion transport model taking porosity as the main coupling variate. The attenuation law of the corroded beams under coupling corrosion factors was studied. Through chloride immersion tests, it was found that applying freezing and thawing cycles and sustained tensile stress can enhance chloride transport capacity by coarsening pores;Carbonation and low compressive stress can repress the chloride ion transport by densifying concrete, but the compressive stress beyond about 0.7 times the compressive strength and tensile stress would enhance the transmission capacity due to the damage of the internal microstructure of concrete. Then, a comprehensive and unified theoretical model of chloride ion transport considering the coupling of carbonation, freeze-thaw cycle, sustained loading and other factors was proposed and verified by taking porosity as the main coupling variable quantity. This model could essentially explain the effects of various factors on chloride ion transport and has good consistency with the test results. Finally, the flexural bearing capacity of the corroded beams is tested, and the failure characteristics, crack characteristics, ultimate bearing capacity, load-displacement relationship and strain distribution of the corroded beams under different corrosion conditions were researched. The results show that the flexural capacity of the corroded beams suffered the coupling effects of multiple corrosion factors degrades, and the bearing capacity decreases with the increase of the corrosion degree of carbonation-freezing thawing cycles;The continuous tensile stress applied to the test beams in t

关键词： Bearing capacity

Sensitivity Analysis on Effective Parameters for Snow-Melting Performance on Automatically Snow-Melting Fabric Roof And Application on Practical Structure

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SSRN 2022年

作者： Zou, Jialin Sun, Xiaoying Liu, Qing Key Lab of Structures Dynamic Behavior Control of China Ministry of Education Harbin Institute of Technology Harbin150090 China Key lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

In recent decades, numerous membrane structures have been built in the cold region of China. Nevertheless, collapse caused by uneven snow distribution and snow sliding from the edge of roofs occur frequently. This collapse threatens the people’s lives and property. In order to prevent collapse of membrane structure, the automatically snow-melting fabric roof based on electrical-thermal system is presented in this study. Automatically snow-melting fabric roof based on electrical-thermal systems are environmental friendly and clean for eliminating snow that has accumulated on fabric roof. The main task in design the automatically snow-melting fabric roof is determining heating feasibility. A thermal simulation method for the snow melting process is described. This numerical method can predict surface temperature, snow-free area ratio and the coefficient of variation for temperature when climatic condition and heating wire layout parameters are provided. The model is validated experimentally and the influence analysis between the inputs( the heating wire power and spacing, wind velocity, solar radiation, ambient temperature and snow thickness) and the outputs of snow-melting performance are found by thermal simulation. Finally, the three layout scheme of heating wire have been proposed based on snow distribution of four prevailing wind direction and have been applied to ensure that snow-melting fabric roof based on electrical-thermal system studied are feasible to control thickness of snow layers in practical membrane structure. © 2022, The Authors. All rights reserved.

关键词： Snow

Experiment and Analysis on Flexural behavior of Uhpc Encased Steel Beams

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SSRN 2024年

作者： Wang, Kun Wang, Jiahui Omar, Ahmed Ahmad Luo, Huihui Yang, Yang Chen, Zaixian Tao, Qiyu College of Civil Science and Engineering Yangzhou University Yangzhou225127 China Key Lab of Structures Dynamic Behavior and Control The Ministry of Education Harbin Institute of Technology Heilongjiang Harbin150090 China Guangling College Yangzhou University Yangzhou225127 China Key Lab of Civil Engineering Structure and Disaster Prevention in Universities of Shandong Harbin Institute of Technology at Weihai Shandong Weihai264209 China

To improve the normal section design approach for ultra-high-performance concrete (UHPC) encased steel beams, this paper first conducted a flexural experiment on eight simply supported UHPC encased steel beams, where the test parameters included the longitudinal reinforcement ratio in tension, the width and thickness of H-shaped steel flanges, the strength grade of H-shaped steel, and the location of H-shaped steel. Then, the calculation method of the flexural capacity of the UHPC encased steel beams was proposed based on the position of the neutralization axis. The short-term stiffness before and after cracking, as well as the average crack width, were established by considering the effect of the steel fibers. Finally, a finite element model of the UHPC encased steel beam was constructed using reasonable material relations and compared with the test results for validation. The results showed that the longitudinal steel bars and the lower flanges of the UHPC encased steel beams first reached a yielding state, and then the upper UHPC was crushed, exhibiting an under-reinforced damage pattern. Increasing the longitudinal reinforcement ratio, the width and thickness of the H-shaped steel flange, the strength grade of the steel, and offsetting the H-shaped steel downward can effectively increase the vertical load-carrying capacity. Due to the high compression strength of the UHPC and the small depth of the compression zone, the upper flanges of the H-shaped steels for some UHPC encased steel beams did not reach yield. Concerning the presence of the H-shaped steel, after the upper UHPC in the span was crushed, the falling branches of the vertical load-deflection curves flattened, showing good ductility. The equivalent stress coefficient k in tension is suggested to be 0.7 when calculating the flexural capacity. For predicting the post-crack stiffness and the average crack width, the fiber influence coefficients B and w are recommended to be 0.2 and 0.3, respectively. The

关键词： Stiffness

Effect of Fiber Reinforcement on Self-Healing Ability of Asphalt Mixture Induced by Microwave Heating

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SSRN 2022年

作者： Yang, Hanwen Ouyang, Jian Jiang, Zhao Ou, Jinping School of Civil Engineering Dalian University of Technology Dalian116024 China School of Transportation and Logistics Dalian University of Technology Dalian116024 China Key Lab of Structures Dynamic Behavior and Control The Ministry of Education China

Microwave heating is considered to be an effective method for accelerating the healing of the cracked asphalt mixture containing microwave-absorbing materials. However, the effects of fiber content and the microwave healing conditions on the selfhealing ability of fiber modified asphalt mixture are not clear. Moreover, the degree of freeze-thaw damage is a crucial aspect that might influence the self-healing ability and mechanical properties of the mixture. To obtain an asphalt mixture with both better selfhealing ability and mechanical properties, the healing index and the mechanical properties of fiber modified asphalt mixtures with three microwave-absorbing fibers additive (i.e. carbon fiber, steel fiber and steel wool) are studied by the semi-circular bending test in this paper. The results show that the freeze-thaw cycles have a great effect on self-healing ability and mechanical properties. However, the addition of fibers can improve the mechanical properties of asphalt mixtures under the initial state. Since the strength of steel fiber and steel wool cannot easily be affected by the action of bending and tensile load, the two fibers can provide better cohesive and adhesive strength with asphalt mastic in the fracture surface, attenuating the effect of freeze-thaw cycles on the self-healing ability of asphalt mixtures. Therefore, it is recommended that 3% of steel fiber and 4% of steel wool can be used as microwave-absorbing materials to enhance the self-healing ability of the asphalt mixtures. © 2022, The Authors. All rights reserved.

关键词： Microwaves

A Two-Stage Mitigation Method for Optical Turbulence-Induced Errors in Vision-Based Structural Displacement Measurement

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SSRN 2024年

作者： Zhang, Xiulin Zhou, Wensong Chen, Xize Wang, Yonghuan Wu, Qi Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control The Ministry of Education Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China Central Research Institute of Building and Construction Co. Ltd MCC Group Beijing100088 China

Vision-based structural displacement measurement techniques have been widely applied. However, the visual sensors used for remote monitoring of structures in high-temperature weather are easily affected by optical turbulence, which introduces errors in displacement measurement. Therefore, this paper proposes a two-stage optical turbulence-induced error alleviation method. In the first stage, the steerable pyramid method is used to decompose the monitoring video, and the phase of each position is independently temporal filtered at different spatial scales and directions to reconstruct the video. To further reduce errors with spatial randomness, a feature point matching method considering the weighted distance is used to track the displacement of multiple measurement points on the target structure in the reconstructed video, and the results are spatially filtered in the second stage. The effectiveness of the proposed method was verified through static and dynamic target experiments using a heater to simulate optical turbulence in the laboratory. © 2024, The Authors. All rights reserved.

关键词： Errors

Evaluating Progressive Collapse with Automatic Check Vba Programming and Identifying Optimal Performance Bracing of Systems

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SSRN 2024年

作者： Bigonah, Mohammad Ali, Barham Haidar Rashed, Parya Li, Shuang Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Faculty of Engineering Civil Engineering Department Tishk International University Erbil Iraq School of Civil Engineering Iran University of Science and Technology Narmak Tehran16765-163 Iran

Braced frames are among the most effective systems for resisting progressive collapse;however, determining the optimal bracing system remains a challenge. In this study, several bracing systems were evaluated using a flowchart that satisfied the regulations UFC (chapter 4). VBA programming tools were employed to facilitate the evaluation process. The utilization of the control process and automated VBA programming proved beneficial in the inspection of plastic hinges and ensuring compliance with UFC regulation. The behaviour of four types of braced frames, including concentrically and eccentrically braced frames (CBF and EBF), was investigated under three scenarios involving member removal. The results demonstrated that the inverted V-braced CBF and EBF systems exhibited superior performance by minimizing vertical displacement and redistributing forces on the remaining connected members. In this scenario, despite experiencing significant vertical displacement, lower global forces were observed in all beams and columns. However, the frame without any bracing system failed to meet the regulatory standards, as determined by the control flowchart. Conversely, the remaining structural systems performed exceptionally well. © 2024, The Authors. All rights reserved.

关键词： Compliance control