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Toughened and self-healing carbon nanotube/epoxy resin composites modified with polycaprolactone filler for coatings, adhesives and FRP

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Journal of Building Engineering 2025年 111卷

作者： Guijun Xian Xiao Qi Jiajun Shi Jingwei Tian HuiGang Xiao Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology) Ministry of Education Heilongjiang Harbin 150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China School of Civil Engineering Harbin Institute of Technology Heilongjiang Harbin 150090 China Yangtze River Delta Carbon Fiber and Composite Material Innovation Center Jiangsu Changzhou 213126 China State Key Laboratory of Molecular Engineering of Polymers Fudan University Shanghai 200433 China

Aiming at the durability problem caused by micro-crack damage in polymer under complex load and hygrothermal conditions, an epoxy resin matrix composite with self-repair function was developed. The multi-damage self-healing function of epoxy resin can be realized by carbon nanotubes (CNTs) reinforcement and polycaprolactone (PCL) toughening. Based on 0.5 wt% CNTs addition, epoxy resin systems with different PCL fillers (1/5/10/15 wt%) were successfully prepared. Through the comparison of thermal and mechanical properties, the optimum formula was obtained as the epoxy resin with CNTs and 5 wt% PCL composite (EPCP5). Furthermore, the tensile strength and elongation at break of EPCP5 increased by 25.4 % and 42.3 %, respectively, compared to the control sample. This improvement was attributed to the formation of hydrogen bonds between PCL and the epoxy resin, enhancing intermolecular forces. The difference in glass transition temperature for samples with varying PCL content was minimal (less than 3.8 %), indicating excellent thermal compatibility between the PCL/CNTs fillers and the resin matrix. Before damage, the tensile and flexural strengths of EPCP5 were 47.28 MPa and 116.35 MPa, respectively. Compared with one cycle for 40 % prefabricated damage, the tensile and flexural strengths of EPCP5 increased by 15.8 % and 25.1 %, 17.4 % and 25.3 % after second and three repair cycles, demonstrating the significant self-healing effect. Under 40 % and 60 % prefabrication loads, the self-healing efficiency of EPCP5 for tensile and flexural strengths reached up to 116.1 % after the third repair cycle. This was because the PCL melt filled and bridged the damaged area, effectively healing and reinforcing the micro-cracks. Noticed, after damage repairing, the micro-morphology showed that the 2–4 μm through cracks in the resin matrix were well healed. Furthermore, the infrared spectrum of EPCP5 showed a combination of the individual spectra of CNTs, PCL, and the resin, which indic

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Experimental study on flexural behavior of precast concrete beams in-span joined with UHPC

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Journal of Building Engineering 2025年 111卷

作者： Zijun Xu Wei Zhou Guoyang Lu School of Civil Engineering Harbin Institute of Technology Harbin 150090 China Department of Architecture and Civil Engineering City University of Hong Kong Tat Chee Avenue Kowloon Tong Hong Kong Special Administrative Region of China Key Lab of Structures Dynamic Behavior and Control Ministry of Education Harbin Institute of Technology Harbin 150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disaster Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China

Efficient connection design is critical for the performance and applicability of precast concrete structures. This study proposes a novel in-span connection strategy using Ultra High Performance Concrete (UHPC) to assemble two standardized short precast concrete beams into a single unit, referred to as a Precast Beam Unit (PBU). This configuration relocates the joint from the beam ends to the mid-span, reducing local weakening and premature failure in high-stress regions while enhancing constructability. Static loading tests were conducted on five PBUs, with one cast-in-place beam serving as a control. The reinforcement ratio and the length of the UHPC corresponding to the diameter of the steel bar were employed as the main design parameters. The flexural behavior and failure mode of specimens were analyzed based on load displacement curves, crack propagation, and strain responses. Results showed that PBU-1 exhibited a 6.3 % higher ultimate flexural capacity than the cast-in-place beam. PBU-5, with a reinforcement ratio of 1.65 % demonstrated a 140.2 % higher ultimate bearing capacity compared to PBU-1 (0.64 % reinforcement ratio). PBUs also showed reduced deflection, narrower crack widths, and enhanced stiffness. The study proposed calculation methods for cracking analysis, short-term stiffness, and the normal section flexural capacity of PBU. Moreover, a finite element model developed in ABAQUS was employed to verify the damage situation and ultimate bearing capacity of the specimens, with good agreement with the experimental results. These findings confirm the safety and applicability of PBU and demonstrate its favorable connection performance.

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Effects of pure carbonation on pore structure and water permeability of white cement mortars

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CEMENT 2022年 9卷

作者： Fangzhou Ren Xingyao Chen Qiang Zeng Chunsheng Zhou Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin 150090 China School of Civil Engineering Harbin Institute of Technology Harbin 150090 China College of Civil Engineering and Architecture Zhejiang University Hangzhou 310058 China

The effects of carbonation on cement-based materials have drawn much attention because of its profound influences on durability performance of concrete structures. Most accelerated carbonation in lab is conducted at RH 50%–70%, which also dries out cement-based materials. The introduced drying action changes pore structure significantly, making the effects of carbonation obscure. To clarify the effects of pure carbonation, water permeability and related micro-structural characteristics are measured on mature mortars, which have been carbonated at water-saturated state. It is found that after carbonation, the porosity of mortars decreases slightly, with finer overall pore structure and lower characteristic pore size. The water permeability also decreases by roughly 40% on average. Based on the pore size distribution curves obtained through the low-field proton nuclear magnetic resonance technique, water permeability is predicted by the Katz-Thompson and Kozeny-Carman theories with satisfactory accuracy. The decrease of water permeability after carbonation agrees well with the reduced characteristic pore length, which quantitatively verifies the observed refinement of nanoscale pore structure due to pure carbonation.

关键词： Carbonation White cement mortar Pore structure Water permeability Low-field nuclear magnetic resonance (LF-NMR)

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Experimental and numerical study of the strengthening effects of externally bonded CFRP on defected of pipes 7

Experimental and numerical study of the strengthening effect...

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7th Asia-Pacific Conference on FRP in structures, APFIS 2019

作者： Kong, Deao Xian, Guijun Key Lab of Structures Dynamic Behavior and Control Harbin Institute of Technology Ministry of Education Heilongjiang Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Heilongjiang Harbin150090 China

ISBN: (纸本)9780648752899

Externally wrapped carbon fiber reinforced polymer (CFRP) composites have been considered to be effectively in strengthening or repairing steel pipes. In the present paper, an unidirectional carbon fiber fabric was used to strengthen steel defective pipes. The strengthening effectiveness of ISO/TS 24817 design methods and the effects of CFRP thickness on the burst pressure, failure mode and stress distribution of the repaired pipes were investigated through burst test and finite element analysis. Comparing with defected pipes, the burst pressure of the pipes enhanced by at least 100% strengthened with ISO/TS 24817 methods. The stress of CFRP decreases linearly from inner layer to outer. A simple finite element analysis method was developed to predict the burst pressure of unidirectional CFRP-wrapped defective steel pipes. © APFIS 2019. All right reserved.

关键词： Finite element method

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Research of snow distribution on lower roof of step roofs with gable-roof on high part

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Jianzhu Jiegou Xuebao/Journal of Building structures 2019年第6期40卷 48-55页

作者： Liu, Boya Zhang, Qingwen Liu, Mengmeng Mo, Huamei Fan, Feng 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

Step roofs are sensitive to snow loads, therefore, snow distribution on lower roof of step roofs with gable-roof on the high part was studied through model experiment. The model experiments were conducted in open air snow-wind combined laboratory developed by the Harbin Institute of Technology, which could simulate the process of natural snowfall. The experiments consisted of four models according to different slopes of the upper gable-roof, and were conducted in different wind velocities and directions. The reliability of the experiment results was verified through comparison of field measurements and experiments on step flat roofs. The results show that the higher the wind velocity, the more significant the unevenness of snow distribution, but the roof snow distribution coefficient does not increase with the wind velocity. The slope of the upper gable-roof has significant influence on snow distribution. For the model which has 60°gable roofs and is under a wind of 3m/s from the windward side, the maximum snow distribution coefficient is 7.9 which is beyond the value in Eurocode. © 2019, Editorial Office of Journal of Building structures. All right reserved.

关键词： Roofs

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Retraction notice to "Study on damage rules on concrete under corrosion of freeze-thaw and saline solution" [Constr. Build. Mater. 304 (2021) 124617] (Construction and Building Materials (2021) 304, (S0950061821023722), (10.1016/***.2021.124617))

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Construction and Building Materials 2025年 474卷

作者： Chen, Dingshi Deng, Yuang Shen, Jiyang Sun, Guorui Shi, Jun School of Civil Engineering Central South University Changsha410075 China National Engineering Laboratory for High Speed Railway Construction Changsha China Bridge Design Institute CCCC First Highway Consultants Co. Ltd. Shaanxi Xi'an710075 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 Laboratory of Bridge Detection and Reinforcement Technology of Ministry of Transport Chang'an University Shaanxi Xi'an710064 China

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://***/locate/withdrawalpolicy). This article has been retracted at the request of authors with approval of the Editor-in-Chief. Following correspondence with the corresponding author requesting to retract this paper over an authorship dispute, it was determined that significant content in this paper is based on a 2019 Chang'an University Master's thesis "Study on Damage Rules of Concrete under Corrosion of Freeze-Thaw and Saline Solution" [https://***/KCMS/detail/***?dbname=CMFD202001&filename= ***] submitted by Su Youbiao and supervised by Dr. Hu Dalin. The specimens reported as "schemes 0 through 9" in this paper are taken directly from the Chang'an University Master's thesis. Results for schemes 0 through 9 are fully reported in the Chang'an University Master's thesis (Chapter 3). No indication or acknowledgement of the source of this data is provided. Neither Su Youbiao nor Hu Dalin is credited as a coauthor. The authors agree with the need to retract this paper in order to uphold and maintain the highest standards of academic integrity. © 2025 Elsevier Ltd

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Jianzhu Jiegou Xuebao/Journal of Building structures 2019年第6期40卷 40-47页

作者： Liu, Mengmeng Zhang, Qingwen Qian, Yiwei Mo, Huamei Fan, Feng 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

Wind-induced snowdrift phenomenon leads to the unbalanced distribution of snow on the building roofs, which could bring a huge safety hazard to the structure. The wind tunnel test is one of the main methods to study wind-induced snowdrift, and similarity theories are the bases of wind tunnel test. In this paper, the similarity theories of Kind, Iversen and Tabler were firstly summarized. After the classification, the main similarity criteria were then summarized, including Froude, Reynold, time similarity criterion and speed similarity criterion, etc. Making use of the wind-snow combined experiment facility, taking artificial snow as the simulating granular material, as well as considering characteristics of different similarity criteria sufficiently, scale experiments on snow distribution around a 0.5 m cube were conducted according to the selected similarity criterion, with the field observation on snow distribution around a 1m cube by Oikawa as the prototypes. Finally, according to the comparison of the prototypes and scale experiments,and with a full consideration of the characteristics of each similarity criterion, the similarity criterion based on the mass transfer rate of saltation process is proved to be the most reliable for the reappearance of snow distribution, and the experimental results show better agreement with the prototype when using the mean wind speed of the prototype. © 2019, Editorial Office of Journal of Building structures. All right reserved.

关键词： Wind tunnels

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Anchorage and fatigue performance of a large-diameter carbon/glass hybrid rod 7

Anchorage and fatigue performance of a large-diameter carbon...

引用

7th Asia-Pacific Conference on FRP in structures, APFIS 2019

作者： Li, Chenggao Xian, Guijun Li, Hui Key Lab of Structures Dynamic Behavior and Control Harbin Institute of Technology Ministry of Education Heilongjiang Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Heilongjiang Harbin150090 China

ISBN: (纸本)9780648752899

A novel pultruded large diameter glass fiber shell (GFS) and carbon fiber core (CFC) hybrid rod (19 mm) was developed for structural applications. In the present paper, the anchorage performance of hybrid rod was systematically studied and a novel extrusion-bonding compound anchor was proposed. The tension-tension fatigue tests were conducted with three stress levels (41.7%, 33.4% and 25.0%) and a fixed stress ratio of 0.4. It can be found the stress distribution of hybrid rod in the extrusionbonding anchor was uneven. The fatigue life of the hybrid rod conformed to the classic logarithm regression model. The fatigue damage of the hybrid FRP rod was initiated by debonding of GFS/CFC interface, leading more loads to be transferred to GFS. The fatigue failure mode was that GFS split and separate from CFC, while no obvious damage was found on CFC. © APFIS 2019. All right reserved.

关键词： Fatigue testing

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NSFnets (Navier-Stokes Flow nets): Physics-informed neural networks for the incompressible navier-stokes equations

arXiv

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arXiv 2020年

作者： Jin, Xiaowei Cai, Shengze Li, Hui Karniadakisc, George Em 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 Division of Applied Mathematics Brown University ProvidenceRI02912 United States

We employ physics-informed neural networks (PINNs) to simulate the incompressible flows ranging from laminar to turbulent flows. We perform PINN simulations by considering two different formulations of the Navier-Stokes equations: the velocity-pressure (VP) formulation and the vorticity-velocity (VV) formulation. We refer to these specific PINNs for the Navier-Stokes flow nets as NSFnets. Analytical solutions and direct numerical simulation (DNS) databases provide proper initial and boundary conditions for the NSFnet simulations. The spatial and temporal coordinates are the inputs of the NSFnets, while the instantaneous velocity and pressure fields are the outputs for the VP-NSFnet, and the instantaneous velocity and vorticity fields are the outputs for the VV-NSFnet. These two different forms of the Navier-Stokes equations together with the initial and boundary conditions are embedded into the loss function of the PINNs. No data is provided for the pressure to the VP-NSFnet, which is a hidden state and is obtained via the incompressibility constraint without splitting the equations. We obtain good accuracy of the NSFnet simulation results upon convergence of the loss function, verifying that NSFnets can effectively simulate complex incompressible flows using either the VP or the VV formulations. For the laminar flow solutions we show that the VV formulation is more accurate than the VP formulation. For the turbulent channel flow we show that NSFnets can sustain turbulence at Reτ ∼ 1, 000 but due to expensive training we only consider part of the channel domain and enforce velocity boundary conditions on the boundaries provided by the DNS data base. We also perform a systematic study on the weights used in the loss function for the data/physics components and investigate a new way of computing the weights dynamically to accelerate training and enhance accuracy. Our results suggest that the accuracy of NSFnets, for both laminar and turbulent flows, can be improved wi

关键词： Turbulence

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Review of research methods in snow engineering for buildings

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Jianzhu Jiegou Xuebao/Journal of Building structures 2019年第6期40卷 1-13页

作者： Fan, Feng Zhang, Borui Zhang, Qingwen Liu, Mengmeng Zhang, Guolong Mo, Huamei 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

Snow engineering for buildings is a new academic discipline, which aims to investigate and forecast the influence of snowfalls on buildings and surroundings as well as the possibility of the disaster such as buildings collapse induced by snow accumulation, based on interdisciplinary researches such as physics, geophysics and catastrophology etc. This paper presents an in-depth review and analysis on the development of three main research methods, namely, field measurement, experimental research and numerical simulation. In terms of the field measurement, the development and theoretical models of several important factors, including snow transport by wind and snow melt by heat transfer, are investigated;the focus of this method in China in the future is also pointed out. Four different research techniques involved in experiments and the establishment of their similarity criterions as well as the selection of relevant parameters are summarized, followed by the necessity of establishing the professional climatic wind tunnel for snow drift research. By reviewing the progress of the computational fluid dynamics (CFD) simulation method, the achievement of existing simulation methods and their potential shortcomings are summarized so as to show the direction of the future improvements in this research method. © 2019, Editorial Office of Journal of Building structures. All right reserved.

关键词： Snow

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