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Experimental study on seismic behavior of interior steel fiber reinforced RPC beam-column joints

Jianzhu Jiegou Xuebao/Journal of Building structures 2019年第3期40卷 161-171页

作者： Wang, Dehong Zheng, Wenzhong Ju, Yanzhong Wei, Chunming Key Lab of Structures Dynamic Behavior and Control of China Ministry of Education Harbin Institute of Technology Harbin150090 China School of Civil Engineering and Architecture Northeast Electric Power University Jilin132012 China

In order to investigate the seismic behavior and shear bearing capacity of steel fiber reinforced reactive powder concrete (RPC) beam-column joints, quasi-static tests on eight RPC interior beam-column joints were carried out. The variables considered in test program included strength of reinforcement, stirrup ratio in joint core, and web rebars and vertical rebars across the joint core, and their influences on the failure mode, shear bearing capacity, hysteretic loops, energy dissipation, strength degeneration and rigidity degeneration behavior of the RPC joints were analyzed. The tests results indicate that the HRB600 longitudinal rebars in the beam mitigate the rigidity degeneration and improve the energy dissipating capacity of the specimen. An increase in stirrup ratio improves the strength degeneration and energy dissipating capacity of the specimen during the failure stages. As the transverse reinforcement ratio in joint core increases from 0 to 0.98%, the shear bearing capacity and ductility of the RPC joint increase. Web rebars and vertical rebars across the joint core improve the shear bearing capacity, strength degeneration and energy dissipation capacity of the specimen. Using the formula of GB 50011-2010 to calculate the shear bearing capacity leads to conservative results for RPC joints with a low stirrup ratio, but tends to be unsafe when the area stirrup ratio is greater than 0.98%. The predictions given by ACI 352- 02 are closer to the test result compared to the GB 50011-2010 prediction, with a safety margin of 9%- 46%. © 2019, Editorial Office of Journal of Building structures. All right reserved.

关键词： Steel fibers

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

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

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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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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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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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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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Actual measurement research on snow load of heated building roof

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Jianzhu Jiegou Xuebao/Journal of Building structures 2019年第6期40卷 24-31页

作者： Zhang, Borui Zhang, Qingwen 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

In order to explore the influence of the building thermal environment on the roof snow load, a prefabricated building model for actual measurement was designed based on the requirement of the law of thermal coefficient (Ct) in foreign building load codes (ASCE/SEI 7-10 and ISO 4355:2013). The proposed model can change the heat resistance of roof and indoor temperature. In detail, the actual measurements of apparent density of snow and snow load under natural snow (with low moisture) and artificial snow (with high moisture) conditions in both the snowmelt period (with daily maximum temperature higher than 0℃) and the non-snowmelt period (with daily maximum temperature not higher than 0℃) were completed. The results show that the snow-layer on the building roof in the snowmelt period experiences the stages of the melt of lower surface snow, and then upward movement of melt layer with discharge of the snowmelt water. The apparent density and environmental temperature of snow show a positively correlated relationship while the variation of snow load appears a typical three-stage form, including the melting, the mass-loss and the recrystallization. Besides, the variation of snow-layer on the building roof in the non-snowmelt period is less than that in the snowmelt period, but the trend is highly consistent, where the snow load decreases with the increasing of roof heat loss. Finally, according to GB 50189-2015 and JGJ 134-2010, the thermal coefficient values of all measured conditions were calculated, and the Ct value of the building with the indoor maximum temperature about 0℃ was suggested to be 1.2. © 2019, Editorial Office of Journal of Building structures. All right reserved.

关键词： Roofs

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Nanocellulose-Derived Hierarchical Carbon Framework-Supported P-Doped MoO2Nanoparticles for Optimizing Redox Kinetics in Lithium–Sulfur Batteries (Adv. Mater. 22/2025)

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Advanced Materials 2025年第22期37卷

作者： Mengjiao Shi Xue Han Wen Qu Meihui Jiang Qing Li Feng Jiang Xiang Xu Shinsuke Ifuku Chunlei Zhang Chao Wang Junfeng Hu Liansheng Yang Yuanjun Lin Haipeng Yu Shouxin Liu Jian Li Yiqiang Wu Wenshuai Chen Key Laboratory of Bio-Based Material Science and Technology of the Ministry of Education Northeast Forestry University Harbin 150040 P. R. China Sustainable Functional Biomaterials Lab Department of Wood Science University of British Columbia Vancouver BC V6T 1Z4 Canada Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology and Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin 150090 P. R. China Research Institute for Sustainable Humanosphere Kyoto University Uji 611-0011 Japan College of Materials Science and Technology Central South University of Forestry and Technology Changsha 410004 P. R. China

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Effects and mechanisms of the main longitudinal beam shape on vortex-induced vibrations of Π-shaped composite girders

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structures 2025年 78卷

作者： Kaiwen Li Yifei Sun Qingkuan Liu Yangxue Wang Qingcai Wang Binxuan Wang School of Civil Engineering Shijiazhuang Tiedao University Shijiazhuang 050043 China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao University Shijiazhuang 050043 China Key Laboratory of Roads and Railway Engineering Safety Control Ministry of Education Shijiazhuang 050043 China Innovation Center for Wind Engineering and Wind Energy Technology of Hebei Province Shijiazhuang 050043 China Research Center for Wind Engineering and Engineering Vibration Guangzhou University Guangzhou 510006 China

As a typical blunt body cross-section, Π-shaped composite girders are notably susceptible to vortex-induced vibrations (VIVs). Therefore, it is crucial to investigate their VIV characteristics and develop corresponding aerodynamic countermeasures. In the present study, synchronous pressure and vibration measurements, combined with computational fluid dynamics (CFD) simulations, were conducted for various Π-shaped composite girder models with different main longitudinal beam shapes. The effects of the main longitudinal beam height ( h ), bottom plate width ( b ), and bottom plate inclination angle ( β ) on the vertical VIV were systematically investigated. The underlying mechanisms of VIV for these parameters were discussed by analyzing the time-frequency characteristics of aerodynamic forces, the relationship between local lift forces and vortex-excited forces (VEFs), and flow field characteristics. The results indicate that reducing h , increasing b , or setting β to 20° can suppress vertical VIV, but the suppressive effect varies and is related to the wind attack angle. From the perspective of the flow field, the formation and movement of the large separation vortices at the leading edge of the girder are responsible for the observed vertical VIVs. The aforementioned parameter adjustments that exhibit an excellent VIV suppression effect can reduce the size and suppress the development of the leading-edge vortices, thereby improving the stability of the flow field. From the perspective of aerodynamic force characteristics, these adjustments can reduce the RMS value of the surface pressure coefficient. They can also shift the dominant frequency of the pressure spectrum away from the vibration frequency, weaken the dominant role of the vibration frequency in the overall lift, and greatly reduce the contribution of local lift to the overall vortex-excited forces (VEFs). As a result, VIV is suppressed.

关键词： Flow field characteristics Synchronous pressure measurement Time-frequency characteristics Vibration mitigation Vortex-induced vibration Π-shaped composite girders

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Model update technique based on time domain response sensitivity enhancement method 9

Model update technique based on time domain response sensiti...

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9th International Conference on Structural Health Monitoring of Intelligent Infrastructure: Transferring Research into Practice, SHMII 2019

作者： Liu, K. Nie, G.B. Key Lab of Structures Dynamics Behavior and Control of the Ministry of Education Harbin Institute of Technology China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin Institute of Technology China Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration China

Time domain finite element model update technique, in which the measurement signals are easy to be obtaineed, can provide more equations, and it has no intermediate process error and can be directly applied to the nonlinear dynamic system, which makes the time domain finite element method more applicable. But the measurement noise bring errors in traditional time domain finite model update technique, so the time domian response sensitivity enhancement method is necessary to study. This paper propose an improved time domain response sensitivity enhancement method based on the multiple singular spectrum analysis method (MSSA), and the proposed method can deal with high measurment nosie level. The proposed method was validated by numerical simulation of a two dimensional truss model with 30% measurement noise, and the model update results were compared with those from the traditional time domain sensitivity method. The results show that the proposed method is effective, robust, and steady with high level measurement noise. © 2019 9th International Conference on Structural Health Monitoring of Intelligent Infrastructure: Transferring Research into Practice, SHMII 2019 - Conference Proceedings. All rights reserved.

关键词： Time domain analysis

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