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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

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Optimized Repairment Properties Of Wer-Cement Composite Material: An Experimental and Simulation Study

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SSRN 2023年

作者： Li, Cong Xiao, Huigang Min, Liu Wang, Wei Xu, Fan School of Civil Engineering Harbin Institute of Technology Heilongjiang China Key Lab of Structures Dynamic Behavior and Control The Ministry of Education Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Heilongjiang Construction Group Co. Ltd Heilongjiang China

The demand for high-performance repair materials has significantly increased in modern society after the completion of infrastructure construction. However, current research on epoxy resin cement mortar composite lacks theoretical investigation of the proportion of epoxy resin and hardener to prepare a composite material with optimal performance, as it often relies on empirical and previous studies. To address this issue, this study employed E44 and D230 raw materials and determined through theoretical calculations that the optimal ratio for the composite material is 4:1. The best ratio and content were validated by various testing techniques, such as workability, mechanical properties, self-developed shear bond strength test, and impermeability performance. These analyses showed that the composite material's epoxy resin and hardener ratio should be 4:1, with a content of 30%. Additionally, the microstructure of the composite material was analyzed using various testing techniques, including SEM, SEM-EDS, XRD, FTIR, and MIP, to investigate its influence on the ITZ, composition, and pore structure. Furthermore, molecular dynamics simulation was conducted to analyze the mechanical properties, adsorption energy, MSD, and RDF of C-S-H and epoxy resin molecules (cross-linked structures) composite, explaining the effect of water molecules on the composite material from an atomic scale perspective. By combining experimentation and simulation, this study proposed a computationally based ratio design method, which could provide new ideas for research and development of WER-cement composite while created a simple shear bond strength testing method for repair materials. © 2023, The Authors. All rights reserved.

关键词： Epoxy resins

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Real-Time Seismic Damage Simulation for Urban Building Portfolio Based on Basic Building Information and Machine Learning

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SSRN 2023年

作者： Li, Shuang Li, Changqing Huang, Yuwen Zhai, Changhai 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 of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Beijing Glory PKPM Technology Co. Ltd Beijing100013 China

Timely and accurate simulation of seismic damage of the urban building portfolio is important for pre-earthquake planning and post-earthquake rescue. This study proposes a real-time seismic damage simulation method for the urban building portfolio based on the multiple degree-of-freedom (MDOF) shear model and flexural-shear model established by basic building information and the machine learning. The formulas for predicting periods of six types of structures are proposed and the surrogate model-Ⅰ for predicting the key inter-story hysteretic parameters are established to optimize the MDOF models. The surrogate model-Ⅱ is established to rapidly predict the engineering demand parameters and damage states of structures under earthquakes. In terms of the generalization capability, an incremental learning strategy is advised to guarantee the accuracy of the surrogate model-Ⅱ in predicting the seismic damage of other urban building portfolios. The results in two city-scale cases show that the proposed method can achieve real-time seismic damage simulation of urban building portfolio with acceptable accuracy, and it’s not necessary to retrain or only needs minor additional training on the existing surrogate model when applied to other urban building portfolios. © 2023, The Authors. All rights reserved.

关键词： Machine learning

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A Study On Properties of Pu-Cement Composites Repairing Material for Seepage control and Plugging

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SSRN 2023年

作者： Li, Cong Bai, Jinrong Jiang, Ying Xiao, Huigang Wang, Wei Xu, Fan School of Civil Engineering Harbin Institution of Technology Heilongjiang China Key Lab of Structures Dynamic Behavior and Control The Ministry of Education Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China Heilongjiang Construction Group Co. Ltd Heilongjiang China

Composite grouting materials are increasingly becoming the focus of seepage control and plugging research, and in order to improve its mechanical properties and delayed hydration repairment effect without compromising its workability, PU-cement composites grouting materials, in which cement are not the main component, still, requiring a finer particle size and good shape. In this study, the ball-milled cement are prepared to combine with WPU and OPU, creating a new PU-cement composites grouting *** particle size distribution, early strength, and micro-structure of ball-milled cement were analyzed, then the best preparation process was determined as 120min ball-milling time and 0.03% grinding aid doping. The viscosity, swelling rate, bond strength, FTIR, XRD and micro-structure of the composites with different ratios of polymer/cement and OPU/WPU were then examined, especially, based on moisture distribution, a new method to evaluate the impermeability of repair materials is proposed, and the function of ball-milled cement in composites and the interaction mechanism between ball-milled cement and PU were discussed. The results showed that the best performance was achieved with the P/C ratio of 3:1 and 4:1, and the OPU/WPU ratio of 2:1 or 3:1, indicating that PU-cement grouting material can be an ideal choice for underground structure seepage control and plugging. © 2023, The Authors. All rights reserved.

关键词： Cements

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Tensile Resistance of Novel Interlocked Angle Connectors Used in Steel-Concrete-Steel Sandwich structures

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SSRN 2022年

作者： Zhou, Zhaohui Wang, Yonghui Zhai, Ximei Key Lab of Structures Dynamic Behavior and Control 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

This paper reports a new interlocked angle connector (IAC) for steel-concrete-steel sandwich structures, and the tensile behaviors of the IACs was also studied in detail by performing the tensile test. There were 14 specimens with different parameters being designed, including embedded depth of IACs, thicknesses of steel sheet, steel angle and bottom plate, side length of steel angle, diameter of steel tube and interlocking bolt. The failure modes and tensile resistances of the proposed IACs were obtained, and three failure modes were identified, including concrete breakout failure, tensile fracture failure of the steel angle and concrete direct shear failure. The main parameters affecting tensile resistance of the IACs were also discussed and analyzed. In addition, analytical models were proposed for predicting the ten¬sile resistances of IACs and their accuracies were also verified via comparing the pre¬dicted values with test results. Finally, the tensile resistances of IACs were compared with those of J-hook connectors, and improved tensile resistance could be observed for the proposed IACs. © 2022, The Authors. All rights reserved.

关键词： Tensile testing

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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

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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

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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

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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

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Water absorptivity and frost resistance performance of self-ignition coal gangue autoclaved aerated concrete

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Journal of Infrastructure Preservation and Resilience 2021年第1期2卷 1-10页

作者： Cong, Xinyu Tan, Yiqiu Lu, Shuang Wang, Zhaojia Huang, Tianyong School of Transportation Science and Engineering Harbin Institute of Technology Huanghe Road 73 Harbin150090 China School of Civil Engineering Harbin Institute of technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education 9 Harbin Institute of Technology Harbin150090 China State Key Laboratory of Solid Waste Reuse for Building Materials Beijing Building 11 Materials Academy of Science Research Beijing100041 China

Self-ignition coal gangue (SCG) used as one of precursors to fabricate autoclaved aerated concrete (AAC). Aiming at studying water absorptivity and frost resistance performance of SCG-based AAC (SCGAAC), three-period water absorption tests and freeze-thaw tests were carried out and the corresponding results were recorded and analyzed. In order to modify the water absorptivity of SCGAAC, foam stabilizer was applied to adjust pore structure while calcium stearate was expected to change hydrophilic feature of SCG. It was demonstrated that the compressive strength of SCGAAC containing foam stabilizer or calcium stearate declined at different levels. For water absorption, foam stabilizer failed to decrease the water content and even increased water absorption rates. Calcium stearate controlled water absorption rate successfully although the ultimate water content hardly reduced. All of the SCGAAC samples exhibited intact appearance after 50 freeze-thaw cycles and showed excellent frost resistance performance. Three models were proposed to predict water absorptivity and frost resistance performance of SCGAAC and the corresponding prediction results matched test resulted well. © The Author(s) 2021.

关键词： Coal

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