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Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar

Shuchun LI, Bo DIAO, Youpo SU,

《结构与土木工程前沿（英文）》 2009年第3卷第4期页码 378-383 doi: 10.1007/s11709-009-0064-8

摘要： To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column, mechanical performance of three groups of six RC flame joints with special-shaped (L, T and+) column and dispersed-steel bars-beam on the top floor under cyclic loads were studied. Experimental comparison was conducted between special-shaped (L, T and+) column and normal beams. The cracking load, yielding load, ultimate bearing capacity, failure patterns, and hysteretic properties at joint core area were investigated. The seismic behaviors of the joints with different proportions of dispersed-steel-bar beams were analyzed. The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and+-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane. Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness. Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.

关键词： beam with dispersed steel bar flame joints with special-shaped beam and column seismic behavior scale of dispersed steel bars

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Hybrid flexural components: Testing pre-stressed steel and GFRP bars together as reinforcement for flexural

Mohammed FARUQI, Oved I. MATA, Francisco AGUINIGA

《结构与土木工程前沿（英文）》 2018年第12卷第3期页码 352-360 doi: 10.1007/s11709-017-0453-3

摘要：

Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer (FRP) materials. However, the flexure behavior of a hybrid system reinforced by the combination of pre-stressed steel and glass fiber reinforced (GFRP) is still relatively unknown. The purpose of this work is to study this. Two slabs of 100 and 150-millimeter thickness, with a span of 2.1 m reinforced with both pre-stressing steel and GFRP were constructed and tested to failure using ACI 318-11 and ACI 440.1R-15. The concrete had strength of 31 MPa and the slabs were respectively reinforced with 5#4 bars and 3#5 bars. Each slab had 37.41 mm² prestressing wire with a failure stress of 1722.5 MPa. The experimental flexural strength and deflection of slabs were compared with their respective sizes theoretical slabs. The theoretical slabs were either reinforced with pre-stressed steel or GFRP rebars, or a hybrid system. It was found that the hybrid system produces better results.

关键词： Partial pre-stressing composite structures GFRP bars

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Numerical study of droplet dynamics impinging onto steel plate covered with scale layer

Jan BOHá?EK, Ale? HORáK

《机械工程前沿（英文）》 2010年第5卷第4期页码 389-398 doi: 10.1007/s11465-010-0108-8

摘要： The steel hot rolling process is inseparably connected to an oxide layer called “scale” at high temperatures. Hydraulic descaling of rolled material is a part of all rolling trains. Surface quality after descaling is fundamental for the final surface quality of a rolled product. The process itself is not theoretically well described; various different approaches have been used to clarify the descaling problem. This paper describes the dynamics of high-speed impact between the compressible water droplet and the steel scale layer. The phenomenon is known as water hammer effect. The purpose of this study is to numerically verify the fact that impact stress can be a significant factor during the descaling process. Considering a high droplet impact speed (100–300 ms ), inferential extremely short time interval (0.1–5 μs) peaks in impact pressure reaching 300 MPa can be found. Droplet dynamics was simulated with the help of LS-Dyna solver, whereas the stress analysis was performed in ANSYS interface. The extreme pressure peaks of very short duration in an impact area are a new phenomenon in the descaling theory.

关键词： hydraulic descaling scale rolling water-hammer descaling theory

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Ordinary Portland Cement (OPC) and Portland Pozzolane Cement (PPC) mixes and different diameter of TMT bars

A D POFALE, S P WANJARI

《结构与土木工程前沿（英文）》 2013年第7卷第1期页码 39-45 doi: 10.1007/s11709-013-0193-y

摘要： Since last two decades, the Portland Pozzolane Cement (PPC) is extensively used in structural concrete. But, till to date, a few literature is available on bond strength of concrete using PPC mixes. There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement (OPC). Hence, a comparative study was conducted on bond strength between OPC and PPC mixes. In the present investigation, total 24 samples consisting of M20, M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days. The pullout bond test was conducted on each specimen as per IS: 2770-1967/1997 [1] and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress. It was observed that the critical bond strength of PPC mixes is 10% higher than OPC mixes. Whereas, marginal improvement was noticed in maximum bond strength of PPC mixes. Hence, based on these findings, it could be concluded that development length for PPC mixes could be reduced by 10% as compared with same grade of OPC mixes.

关键词： bond strength Portland Pozzolane Cement (PPC) concrete Ordinary Portland Cement (OPC) concrete bond between concrete and steel pullout test development length

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基于纳米铁碳析出物的钢综合强化机理

傅杰,李光强,于月光,毛新平,方克明

《中国工程科学》 2011年第13卷第1期页码 31-42

摘要：

简要叙述了关于钢强化机理的研究现状，用化学相分析+X射线小角散射、RTO方法及高分辨透射电镜对薄板坯连铸连轧钛微合金化高强耐候钢中纳米粒子的属性进行了综合分析。发现钛微合金化高强耐候钢中尺寸<36 nm的粒子，除纳米TiC以外，还存在大量的纳米Fe3C，其体积分数为同尺寸TiC体积分数的4.4倍，析出强化作用比纳米TiC粒子大，不可忽略；提出了钢的综合强化机理，指出对不同种类、不同尺寸的纳米析出粒子，应分别根据位错切割和位错绕过机理计算出析出强化贡献，然后与固溶强化和细晶强化贡献加和，求得钢的屈服强度；讨论了细晶强化与位错强化不能加和的原因以及相变对钢强度影响的表现形式，对钛微合金化高强耐候钢屈服强度的理论计算与生产结果相符，实验钢 σ_s= 630~676 MPa，实际 σ_s=630~680 MPa。简述了钢综合强化机理的应用情况，指出了有待进一步研究的科学问题。

关键词：屈服强度纳米铁碳析出物纳米TiC 析出强化钢的综合强化机理

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Performance of a novel bent-up bars system not interacting with concrete

Aydin SHISHEGARAN, Mohammad Reza GHASEMI, Hesam VARAEE

《结构与土木工程前沿（英文）》 2019年第13卷第6期页码 1301-1315 doi: 10.1007/s11709-019-0552-4

摘要： Increasing the bending and shear capacities of reinforced concrete members is an interesting issue in structural engineering. In recent years, many studies have been carried out to improve capacities of reinforced concrete members such as using post and pre-tensioning, Fiber Reinforced Polymer and other techniques. This paper proposes a novel and significant technique to increase the flexural capacity of simply supported reinforced concrete beams. The proposed method uses a new reinforcement bar system having bent-up bars, covered with rubber tubes. This technique will avoid interaction of bent-up bars with concrete. They are located in the zone where compressive and tensile forces act against one another. The compressive force in the upper point of the bent-up bars is exerted to the end point of these bars located under neutral axis. Moreover, the tensile stress is decreased in reinforcements located under the neutral axis. This will cause the Reinforced Concrete (RC) beam to endure extra loading before reaching yield stress. These factors may well be considered as reasons to increase bending capacity in the new system. The laboratory work together with finite element method analysis were carried out in this investigation. Furthermore, bending capacity, ductility, strength, and cracking zone were assessed for the new proposed system and compared with the conventional model. Both the FEM simulation and the experimental test results revealed that the proposed system has significant impact in increasing the load bearing capacity and the stiffness of the RC beams. In the present study, an equation is formulated to calculate bending capacity of a new reinforcement bar system beam.

关键词： bending capacity rubber tube stress transfer bent-up bars ductility cracking

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Room-temperature hydrogenation of halogenated nitrobenzenes over metal–organic-framework-derived ultra-dispersed

《化学科学与工程前沿（英文）》 2022年第16卷第12期页码 1782-1792 doi: 10.1007/s11705-022-2220-9

摘要： Ultra-dispersed Ni nanoparticles (7.5 nm) on nitrogen-doped carbon nanoneedles (Ni@NCNs) were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines. Two different crystallization methods (stirring and static) were compared and the optimal pyrolysis temperature was explored. Ni@NCNs were systematically characterized by wide analytical techniques. In the hydrogenation of p-chloronitrobenzene, Ni@NCNs-600 (pyrolyzed at 600 °C) exhibited extraordinarily high performance with 77.9 h^–1 catalytic productivity and > 99% p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions (90 °C, 1.5 MPa H₂), showing obvious superiority compared with reported Ni-based catalysts. Notably, the reaction smoothly proceeded at room temperature with full conversion and > 99% selectivity. Moreover, Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups (halogen, nitrile, keto, carboxylic, etc.), and could be easily recycled by magnetic separation and reused for 5 times without deactivation. The adsorption tests showed that the preferential adsorption of –NO₂ on the catalyst can restrain the dehalogenation of p-chloronitrobenzene, thus achieving high p-chloroaniline selectivity. While the high activity can be attributed to high Ni dispersion, special morphology, and rich pore structure of the catalyst.

关键词： halogenated nitrobenzenes room-temperature hydrogenation Ni nanoparticles nitrogen-doped carbon nanoneedles metal–organic-framework

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The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient

Souzana P. TASTANI,Maria S. KONSTA-GDOUTOS,Stavroula J. PANTAZOPOULOU,Victor BALOPOULOS

《结构与土木工程前沿（英文）》 2016年第10卷第2期页码 214-223 doi: 10.1007/s11709-016-0332-3

摘要： Stress transfer between reinforcing bars and concrete is engaged through rib translation relative to concrete, and comprises longitudinal bond stresses and radial pressure. The radial pressure is equilibrated by hoop tension undertaken by the concrete cover. Owing to concrete’s poor tensile properties in terms of strength and deformability, the equilibrium is instantly released upon radial cracking of the cover along the anchorage with commensurate abrupt loss of the bond strength. Any improvement of the matrix tensile properties is expected to favorably affect bond in terms of strength, resilience to pullout slip, residual resistance and controlled slippage.The aim of this paper is to investigate the local bond of steel bars developed in adverse tensile stress conditions in the concrete cover. In the tests, the matrix comprises a novel, strain resilient cementitious composite (SRCC) reinforced with polypropylene fibers (PP) with the synergistic action of carbon nano-tubes (CNT). Local bond is developed over a short anchorage length occurring in the constant moment region of a four-point bending short beam. Parameters of investigation were the material structure (comprising a basic control mix, reinforced with CNTs and/or PP fibers) and the age of testing. Accompanying tests used to characterize the cementitious material were also conducted. The test results illustrate that all the benefits gained due to the synergy between PP fibers and CNTs in the matrix, namely the maintenance of the multi-cracking effect with time, the increased strength and deformability as well as the highly increased material toughness, were imparted in the recorded bond response. The local bond response curves thus obtained were marked by a resilient appearance exhibiting sustained strength up to large levels of controlled bar-slip; the elasto-plastic bond response envelope was a result of the confining synergistic effect of CNTs and the PP fibers, and it occurred even without bar yielding.

关键词： carbon nanotubes strain resilient cementitious composite polypropylene fibers tensile bending bond

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浅滩区大型基础施工方案比选

先正权,梁进达,赵磊

《中国工程科学》 2010年第12卷第4期页码 29-32

摘要：

介绍了在浅滩区大型基础施工中基桩施工平台采用钢板桩围堰筑岛替代钢结构平台的成功经验，利用钢板桩围堰筑岛作为基桩施工平台，将承台施工阶段的钢板桩围堰提前施工，起到了减少施工成本、节省工期、降低施工难度、提高施工质量的作用。

关键词：浅滩区大型基础钢板桩围堰筑岛

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Self-centering steel plate shear walls for improving seismic resilience

Patricia M. CLAYTON,Daniel M. DOWDEN,Chao-Hsien LI,Jeffrey W. BERMAN,Michel BRUNEAU,Laura N. LOWES,Keh-Chuan TSAI

《结构与土木工程前沿（英文）》 2016年第10卷第3期页码 283-290 doi: 10.1007/s11709-016-0344-z

摘要： As part of a Network for Earthquake Engineering Simulation research project led by researchers at the University of Washington with collaborators at University at Buffalo, and Taiwan National Center for Research on Earthquake Engineering, a self-centering steel plate shear wall (SC-SPSW) system has been developed to achieve enhanced seismic performance objectives, including recentering. The SC-SPSW consists of thin steel infill panels, referred to as web plates that serve as the primary lateral load-resisting and energy dissipating element of the system. Post-tensioned (PT) beam-to-column connections provide system recentering capabilities. A performance-based design procedure has been developed for the SC-SPSW, and a series of nonlinear response history analyses have been conducted to verify intended seismic performance at multiple hazard levels. Quasi-static subassembly tests, quasi-static and shake table tests of scaled three-story specimens, and pseudo-dynamic tests of two full-scale two-story SC-SPSWs have been conducted. As a culmination of this multi-year, multi-institutional project, this paper will present an overview of the SC-SPSW numerical and experimental research programs. This paper will also discuss innovative PT connection and web plate designs that were investigated to improve constructability, resilience, and seismic performance and that can be applied to other self-centering and steel plate shear wall systems.

关键词： self-centering steel plate shear walls large-scale experiment post-tensioned connections performance-based design

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Induction motors variable speed drives diagnosis through rotor resistance monitoring

K. YAHIA, S. ZOUZOU, F. BENCHABANE

《能源前沿（英文）》 2012年第6卷第4期页码 420-426 doi: 10.1007/s11708-012-0192-z

摘要： Induction motor driven by vector control method makes high performance control of torque and speed possible. The decoupling of flux and electromagnetic torque obtained by field orientation depends on the precision and the accuracy of the estimated states. Rotor asymmetries lead to perturbations of air gap flux patterns in induction machines. These perturbations in flux components affect the electromagnetic torque, as well as stator currents and voltages. This paper first investigates the control of the induction motor using an extended Kalman filter (EKF) for a direct field-oriented control. It then studies the broken rotor bars (BRBs) fault by the monitoring the rotor resistance. The hypothesis on which the detection is based is that the apparent rotor resistance of the motor will increase when a rotor bar breaks. The rotor resistance is estimated and compared with its nominal value to detect BRBs fault. The EKF estimates the rotor flux, speed and rotor resistance on line by using only measurements of the stator voltages and currents. Simulation results show the effectiveness of the proposed method in the cases of load torque perturbation and speed reversion.

关键词： induction motor vector control broken rotor bars (BRBs) diagnostic extended Kalman filter (EKF)

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A novel approach in preparing polymer/nano-CaCO composites

LIU Zhengying, YU Runze, YANG Mingbo, FENG Jianmin, YANG Wei, YIN Bo

《化学科学与工程前沿（英文）》 2008年第2卷第1期页码 115-122 doi: 10.1007/s11705-008-0020-5

摘要： An novel compounding process using nano-CaCO aqueous suspension for preparing polymer/nano-CaCO composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nanoparticle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical polymeric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO improve slightly. It proved that this approach is suitable for the preparation of nanocomposites based on both polar and non-polar polymers.

关键词： preparation suitable nano-CaCO pre-dispersed nanoparticle processing

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中国钢桥

潘际炎

《中国工程科学》 2007年第9卷第7期页码 18-26

摘要：

介绍了我国钢桥的发展及国内外的钢桥比较；论述了建造钢桥的钢材及其要求的化学成分和物理力学性能。

关键词：中国钢桥钢材钢桥设计钢桥结构

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Structure controlling and process scale-up in the fabrication of nanomaterials

Chunzhong LI,

《化学科学与工程前沿（英文）》 2010年第4卷第1期页码 18-25 doi: 10.1007/s11705-009-0305-3

摘要： Nanotechnology is already having a significant commercial impact, and will very certainly have a much greater impact in the future. The research on process engineering and scale-up will be very important for the commercial production and application of nanomaterials, because the properties and structure of nanomaterials are not only determined by the nucleation and growth process, but also strongly affected by the engineering properties, such as the mixing, the heat and mass transfer, and also the distribution of temperature, concentration, etc. This paper will present some research work in our laboratory on the fabrication of nanomaterials. Based on the chemical engineering principle and methods, many kinds of novel nanomaterials can be synthesized and their structure can be easily controlled through adjusting the parameters of the fluid mixing, and the distribution of temperature, residence time and concentration, etc. By using the micro-mixing, heat and mass transfer and reaction control methods, the host-guest nanocomposites have been assembled and assumed as the novel electroanalytical sensing nanobiocomposite materials. Based on the principles of chemical engineering, the manufacturing technologies for magnetic powders, calcium carbonate, and titanium dioxide have been developed for commercial-scale production, and the largest production scale has reached 15 kt/year.

关键词： scale-up significant commercial electroanalytical engineering laboratory

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Large-scale App privacy governance

《工程管理前沿（英文）》页码 640-652 doi: 10.1007/s42524-022-0228-y

摘要： Recently, the problem of mobile applications (Apps) leaking users’ private information has aroused wide concern. As the number of Apps continuously increases, effective large-scale App governance is a major challenge. Currently, the government mainly filters out Apps with potential privacy problems manually. Such approach is inefficient with limited searching scope. In this regard, we propose a quantitative method to filter out problematic Apps on a large scale. We introduce Privacy Level (P-Level) to measure an App’s probability of leaking privacy. P-Level is calculated on the basis of Permission-based Privacy Value (P-Privacy) and Usage-based Privacy Value (U-Privacy). The former considers App permission setting, whereas the latter considers App usage. We first illustrate the privacy value model and computation results of both values based on real-world dataset. Subsequently, we introduce the P-Level computing model. We also define the P-Level computed on our dataset as the PL standard. We analyze the distribution of average usage and number of Apps under the levels given in the PL standard, which may provoke insights into the large-scale App governance. Through P-Privacy, U-Privacy, and P-Level, potentially problematic Apps can be filtered out efficiently, thereby making up for the shortcoming of being manual.

关键词： privacy risk Privacy Level quantification large-scale App governance