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Shear-critical reinforced concrete columns under various loading rates

Witarto WITARTO,Liang LU,Rachel Howser ROBERTS,Y. L. MO,Xilin LU

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 362-372 doi: 10.1007/s11709-014-0083-y

摘要: This paper presents an experimental study of shear-governed reinforced concrete columns subjected to different loading rates. Four typical short columns were tested cyclically with loading rate of 0.05, 1, 3, and 5 Hz, simulating seismic load. Test result indicated that the loading rate does not affect the column behavior when the rate is up to 5 Hz. Furthermore, Carbon Nano-Fiber Aggregates (CNFAs) were utilized as internal sensors to detect the damage in the column. The test result shows that the CNFAs work well sensing the structural behavior. The CNFA output was further quantitatively correlated to the structural damage level. Finally, a finite element analytical model was constructed to describe the behavior of short columns with shear failure. The analytical model successfully modeled the cyclic loading test results.

关键词: reinforced concrete columns     shear failure     loading rate     Carbon Nano-Fiber Aggregates (CNFAs)     finite element analysis     OpenSees    

Behavior of aqueous stable colloidal nano-C

Jing HUO,Ye YU,Ling GE,Bo ZHANG,Yiliang HE

《环境科学与工程前沿(英文)》 2015年 第9卷 第2期   页码 197-205 doi: 10.1007/s11783-014-0624-6

摘要: C , as one of carbon nanomaterials widely used in various fields, could be released into the water environment thus exerting some potential health risks to human beings. This work examined the behavior of aqueous stable colloidal nano-C (nC ) aggregates under different environmental conditions including Polyethylene glycol octylphenol ether (TX100) micelles concentration, pH, and reaction time when exposed to TX100 micelles. Results show that the nC aggregates became more dispersive and restored the capability of generating the singlet oxygen when exposed to TX100 micelles. With the increase of TX100 concentration, smaller average size of nC aggregates was observed in dynamic light scattering (DLS) analysis, the fluorescence intensity of TX100 was more quenched by nC aggregates, and the kinetic rate constant of generating the singlet oxygen for nC aggregates was improved. The mean size of nC aggregates in the presence of TX100 had no obvious variations when the pH ranged from 4 to 8. The longer reaction time between nC aggregates and TX100 led to a higher kinetic rate constant of generating the singlet oxygen. Collective data suggest that variations in physicochemical properties of nC aggregates are strongly dependent on the surrounding media under different environmental conditions and directly govern nC ’s transport behavior and potential toxicity.

关键词: nano-C60 (nC60) aggregates     photochemical reactivity     artificial biological membrane    

MICROBIAL NECROMASS WITHIN AGGREGATES STABILIZES PHYSICALLY-PROTECTED C RESPONSE TO CROPLAND MANAGEMENT

《农业科学与工程前沿(英文)》 2023年 第10卷 第2期   页码 198-209 doi: 10.15302/J-FASE-2023498

摘要:

● The contribution of fungal necromass C to SOC increased with aggregate sizes.

关键词: cropland management     microbial necromass     soil aggregates     soil carbon sequestration     soil organic matter    

Pd nano-catalyst supported on biowaste-derived porous nanofibrous carbon microspheres for efficient catalysis

《化学科学与工程前沿(英文)》 2023年 第17卷 第9期   页码 1289-1300 doi: 10.1007/s11705-023-2299-7

摘要: Environmental pollution caused by the presence of aromatic aldehydes and dyes in wastewater is a serious global concern. An effective strategy for the removal of these pollutants is their catalytic conversion, possibly to valuable compounds. Therefore, the design of efficient, stable and long-lifetime catalysts is a worthwhile research goal. Herein, we used nanofibrous carbon microspheres (NCM) derived from the carbohydrate chitin present in seafood waste, and characterized by interconnected nanofibrous networks and N/O-containing groups, as carriers for the manufacture of a highly dispersed, efficient and stable Pd nano-catalyst (mean diameter ca. 2.52 nm). Importantly, the carbonised chitin’s graphitized structure, defect presence and large surface area could promote the transport of electrons between NCM and Pd, thereby endowing NCM supported Pd catalyst with high catalytic activity. The NCM supported Pd catalyst was employed in the degradation of some representative dyes and the chemoselective hydrogenation of aromatic aldehydes; this species exhibited excellent catalytic activity and stability, as well as applicability to a broad range of aromatic aldehydes, suggesting its potential use in green industrial catalysis.

关键词: biowaste chitin     nanofibrous     palladium     nano-catalyst     catalysis    

Diversity-oriented synthesis of blue emissive nitrogen heterocycles and their conjugation with carbonnano-onions

Viviana Maffeis, Lisa Moni, Daniele Di Stefano, Silvia Giordani, Renata Riva

《化学科学与工程前沿(英文)》 2020年 第14卷 第1期   页码 76-89 doi: 10.1007/s11705-019-1833-0

摘要: The search for new fluorescent molecules for possible applications as functional -electron systems and their conjugation with different nanomaterials is nowadays of paramount importance to broaden the availability of materials with different properties. Herein we present a diversity-oriented approach to heterocyclic luminophores based on a multicomponent Ugi reaction followed by a Pd-mediated cascade sequence. The new molecules are coupled to carbon nano-onions, and hybrid systems represent the first example of blue emitters conjugated with these carbon nanoparticles.

关键词: carbon nano-onions     multicomponent reactions     blue emitters     fluorescence     isoquinolines    

Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbonfiber and poly(trimethylene terephthalate)

Mingtao RUN, Hongzan SONG, Yanping HAO

《化学科学与工程前沿(英文)》 2009年 第3卷 第3期   页码 255-264 doi: 10.1007/s11705-009-0008-9

摘要: The spherulites of the short carbon fiber(SCF)/poly (trimethylene terephthalate) (PTT) composites formed in limited space at designed temperatures, and their melting behaviors were studied by the polarized optical microscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. The results suggest that SCF content, isothermal crystallization temperatures, and the film thicknesses influence the crystal morphology of the composites. The dimension of the spherulites is decreased with increasing SCF content, but whether banded or nonbanded spherulites will form in the composites is not dependent on SCF content. However, the crystal morphology of the composites depends strongly on the temperature. When the isothermal crystallization temperatures increase from 180°C to 230°C, the crystal morphology of SCF/PTT composites continuously changes in the following order: nonbanded → banded → nonbanded spherulites. Discontinuous circle lines form in the film when the film thickness increases from 30 to 60 μm. Basing on the SEM observation, it is found that these circle lines are cracks formed due to the constriction difference of the different parts of the spherulites. These cracks are formed when the film is cooled from the isothermal crystallization temperature to the room temperature at a slow cooling rate; while they will disappear gradually at different temperatures in the heating process. The crack will appear/disappear first around the center of the spherulite when the film was cooled/heated. The nontwisted or slightly twisted lamellas will reorganize to form highly twisted lamellas inducing apparent banded texture of the spherulites.

关键词: poly(trimethylene terephthalate)     short carbon fiber     banded spherulites     crack    

The preparation and performance of lignin-based activated carbon fiber adsorbents for treating gaseous

Min Song, Wei Zhang, Yongsheng Chen, Jinming Luo, John C. Crittenden

《化学科学与工程前沿(英文)》 2017年 第11卷 第3期   页码 328-337 doi: 10.1007/s11705-017-1646-y

摘要: Two types of lignin-based carbon fibers were prepared by electrospinning method. The first was activated with Fe O (LCF-Fe), and the second was not activated with Fe O (LCF). Gas phase adsorption isotherms for toluene on LCF-Fe and LCF were studied. The gas phase adsorption isotherm for 0% RH showed LCF-Fe have about 439 mg/g adsorption capacity which was close to that of commercially available activated carbon (500 mg/g). The Dubinin-Radushkevich equation described the isotherm data very well. Competitive adsorption isotherms between water vapor and toluene were measured for their RH from 0 to 80%. The effect of humidity on toluene gas-phase adsorption was predicted by using the Okazaki et al. model. In addition, a constant pattern homogeneous surface diffusion model (CPHSDM) was used to predict the toluene breakthrough curve of continuous flow-packed columns containing LCF-Fe, and its capacity was 412 mg/g. Our study, which included material characterization, adsorption isotherms, kinetics, the impact of humidity and fixed bed performance modeling, demonstrated the suitability of lignin-based carbon fiber for volatile organic compound removal from gas streams.

关键词: lignin     carbon fiber     electrospinning     toluene     humidity    

Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened

Peng DENG, Boyi YANG, Xiulong CHEN, Yan LIU

《结构与土木工程前沿(英文)》 2020年 第14卷 第5期   页码 1215-1231 doi: 10.1007/s11709-020-0663-y

摘要: A method for strengthening damaged tubular steel T-joints under axial compression by wrapping them with carbon fiber-reinforced polymer (CFRP) sheets was proposed and evaluated. The influence of the CFRP strengthening on the failure mode and load capacity of T-joints with different degrees of damage was investigated using experiments and finite element analyses. Five T-joints were physically tested: one bare joint to obtain the peak load and corresponding displacement ( ), two reinforced joints to provide a reference, and two pre-damaged then retrofitted joints to serve as the primary research objects. The ratio of the pre-loaded specimen chord displacement to the value of was considered to be the degree of damage of the two retrofitted joints, and was set to 0.80 and 1.20. The results demonstrate that the maximum capacity of the retrofitted specimen was increased by 0.83%–15.06% over the corresponding unreinforced specimens. However, the capacity of the retrofitted specimen was 2.51%–22.77% lesser compared with that of the directly reinforced specimens. Next, 111 numerical analysis models (0.63≤ ≤0.76, 9.70≤ ≤16.92) were established to parametrically evaluate the effects of different geometric and strengthening parameters on the load capacity of strengthened tubular T-joints under different degrees of damage. The numerical analysis results revealed that the development of equivalent plastic strain at the selected measuring points was moderated by strengthening with CFRP wrapping, and indicated the optimal CFRP strengthening thickness and wrapping orientation according to tubular T-joint parameters. Finally, reasonable equations for calculating the load capacity of CFRP-strengthened joints were proposed and demonstrated to provide accurate results. The findings of this study can be used to inform improved CFRP strengthening of damaged tubular steel structures.

关键词: tubular T-joint     carbon fiber-reinforced polymer     degree of damage     numerical analysis     equivalent plastic strain    

Effect of denitrifying bacteria on the electrochemical reaction of activated carbon fiber in electrochemical

YING Diwen, JIA Jinping, ZHANG Lehua

《环境科学与工程前沿(英文)》 2007年 第1卷 第3期   页码 305-310 doi: 10.1007/s11783-007-0051-z

摘要: An electrochemical-activated denitrifying biofilm system consisting of activated carbon fiber electrodes immobilized with denitrifying bacteria film as cathode was studied. A revised model for an electrochemical-activated denitrifying biofilm was developed and validated by electrochemical analysis of cathodal polarization curves and nitrate consumption rate. The cathodal polarization curve and nitrate consumption rate were introduced to verify the rate of electrochemical reaction and the activity of denitrifying bacteria, respectively. It was shown that the denitrification process effectively strengthened the electrochemical reaction while the electron also intensified denitrification activity. Electron was transferred between electrochemical process and biological process not only by hydrogen molecule but also by new produced active hydrogen atom. Additionally, a parameter of apparent exchange current density was deprived from the cathodal polarization curve with high overpotential, and a new bio-effect current density was defined through statistical analysis, which was linearly dependent to the activity of denitrification bacteria. Activated carbon fiber (ACF) electrode was also found to be more suitable to the electrochemical denitrifying system compared with graphite and platinum.

关键词: ACF     apparent exchange     hydrogen molecule     activated     biological process    

Studies of fiber-matrix debonding

Navneet DRONAMRAJU,Johannes SOLASS,Jörg HILDEBRAND

《结构与土木工程前沿(英文)》 2015年 第9卷 第4期   页码 448-456 doi: 10.1007/s11709-015-0316-8

摘要: In this paper, the debonding of a single fiber-matrix system of carbon fiber reinforced composite (CFRP) AS4/Epson 828 material is studied using Cohesive Zone Model (CZM). The effect of parameters namely, maximum tangential contact stress, tangential slip distance and artificial damping coefficient on the debonding length at the interface of the fiber-matrix is analyzed. Contact elements used in the CZM are coupled based on a bilinear stress-strain curve. Load is applied on the matrix, tangential to the interface. Hence, debonding is observed primarily in Mode II. Wide range of values are considered to study the inter-dependency of the parameters and its effect on debonding length. Out of the three parameters mentioned, artificial damping coefficient and tangential slip distance significantly affect debonding length. A thorough investigation is recommended for case wise interface debonding analysis, to estimate the optimal parametric values while using CZM.

关键词: single fibre     cohesive zone model     interface debonding     carbon fiber reinforced composite (CFRP)    

Consumption of carbon fiber plates in the reinforced concrete beams strengthened with CFPs

BU Liangtao, SHI Chuxian, SONG Li

《结构与土木工程前沿(英文)》 2007年 第1卷 第4期   页码 393-398 doi: 10.1007/s11709-007-0053-8

摘要: Four-point bending flexural tests were conducted to one full-size reinforced concrete (RC) beam and three full-size RC beams strengthened with carbon fiber plates (CFPs). The experimental results showed that the consumption of CFP

关键词: flexural     full-size     Four-point     consumption     experimental    

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1426-1440 doi: 10.1007/s11709-021-0783-z

摘要: The ultra-high-performance concrete (UHPC) and fiber-reinforced polymer (FRP) are well-accepted high-performance materials in the field of civil engineering. The combination of these advanced materials could contribute to improvement of structural performance and corrosion resistance. Unfortunately, only limited studies are available for shear behavior of UHPC beams reinforced with FRP bars, and few suggestions exist for prediction methods for shear capacity. This paper presents an experimental investigation on the shear behavior of UHPC beams reinforced with glass FRP (GFRP) and prestressed with external carbon FRP (CFRP) tendons. The failure mode of all specimens with various shear span to depth ratios from 1.7 to 4.5 was diagonal tension failure. The shear span to depth ratio had a significant influence on the shear capacity, and the effective prestressing stress affected the crack propagation. The experimental results were then applied to evaluate the equations given in different codes/recommendations for FRP-reinforced concrete structures or UHPC structures. The comparison results indicate that NF P 18-710 and JSCE CES82 could appropriately estimate shear capacity of the slender specimens with a shear span to depth ratio of 4.5. Further, a new shear design equation was proposed to take into account the effect of the shear span to depth ratio and the steel fiber content on shear capacity.

关键词: beam     external prestressing     ultra-high-performance concrete     fiber-reinforced polymers     shear behavior     design equation    

A Cu-modified active carbon fiber significantly promoted HS and PH simultaneous removal at a low reaction

《环境科学与工程前沿(英文)》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1425-3

摘要:

• Cu0.15-ACF performs the best for H2S and PH3 simultaneous removal.

关键词: ACF     H2S     PH3     Cu     Low temperature     Simultaneous removal    

Experimental study on fire protection methods of reinforced concrete beams strengthened with carbon fiber

HU Kexu, HE Guisheng, LU Fan

《结构与土木工程前沿(英文)》 2007年 第1卷 第4期   页码 399-404 doi: 10.1007/s11709-007-0054-7

摘要: In this paper, two reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymer (CFRP) and attached with thick-painted fire resistant coating were tested for fire resistance following the standard fire testing procedures. The experimental results show that the specimen pasted with the insulated layer of 50 mm in thickness could resist fire for 2.5 h. It is also demonstrated that the steel wire mesh embedded in the insulated layer can effectively prevent it from cracking and eroding under firing.

关键词: polymer     insulated     resistant     CFRP     resistance    

Multiscale model of micro curing residual stress evolution in carbon fiber-reinforced thermoset polymer

Xinyu HUI, Yingjie XU, Weihong ZHANG

《机械工程前沿(英文)》 2020年 第15卷 第3期   页码 475-483 doi: 10.1007/s11465-020-0590-6

摘要: In this study, the micro curing residual stresses of carbon fiber-reinforced thermoset polymer (CFRP) composites are evaluated using a multiscale modeling method. A thermochemical coupling model is developed at the macroscale level to obtain the distributions of temperature and degree of cure. Meanwhile, a representative volume element model of the composites is established at the microscale level. By introducing the information from the macroscale perspective, the curing residual stresses are calculated using the microscale model. The evolution of curing residual stresses reveals the interaction mechanism of fiber, matrix, and interphase period during the curing process. Results show that the curing residual stresses mostly present a tensile state in the matrix and a compressive state in the fiber. Furthermore, the curing residual stresses at different locations in the composites are calculated and discussed. Simulation results provide an important guideline for the analysis and design of CFRP composite structures.

关键词: CFRP     curing residual stress     multiscale modeling     finite element method    

标题 作者 时间 类型 操作

Shear-critical reinforced concrete columns under various loading rates

Witarto WITARTO,Liang LU,Rachel Howser ROBERTS,Y. L. MO,Xilin LU

期刊论文

Behavior of aqueous stable colloidal nano-C

Jing HUO,Ye YU,Ling GE,Bo ZHANG,Yiliang HE

期刊论文

MICROBIAL NECROMASS WITHIN AGGREGATES STABILIZES PHYSICALLY-PROTECTED C RESPONSE TO CROPLAND MANAGEMENT

期刊论文

Pd nano-catalyst supported on biowaste-derived porous nanofibrous carbon microspheres for efficient catalysis

期刊论文

Diversity-oriented synthesis of blue emissive nitrogen heterocycles and their conjugation with carbonnano-onions

Viviana Maffeis, Lisa Moni, Daniele Di Stefano, Silvia Giordani, Renata Riva

期刊论文

Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbonfiber and poly(trimethylene terephthalate)

Mingtao RUN, Hongzan SONG, Yanping HAO

期刊论文

The preparation and performance of lignin-based activated carbon fiber adsorbents for treating gaseous

Min Song, Wei Zhang, Yongsheng Chen, Jinming Luo, John C. Crittenden

期刊论文

Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened

Peng DENG, Boyi YANG, Xiulong CHEN, Yan LIU

期刊论文

Effect of denitrifying bacteria on the electrochemical reaction of activated carbon fiber in electrochemical

YING Diwen, JIA Jinping, ZHANG Lehua

期刊论文

Studies of fiber-matrix debonding

Navneet DRONAMRAJU,Johannes SOLASS,Jörg HILDEBRAND

期刊论文

Consumption of carbon fiber plates in the reinforced concrete beams strengthened with CFPs

BU Liangtao, SHI Chuxian, SONG Li

期刊论文

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

期刊论文

A Cu-modified active carbon fiber significantly promoted HS and PH simultaneous removal at a low reaction

期刊论文

Experimental study on fire protection methods of reinforced concrete beams strengthened with carbon fiber

HU Kexu, HE Guisheng, LU Fan

期刊论文

Multiscale model of micro curing residual stress evolution in carbon fiber-reinforced thermoset polymer

Xinyu HUI, Yingjie XU, Weihong ZHANG

期刊论文