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An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1653-1653 doi: 10.1007/s11709-019-0578-7

摘要: In recent years, there has been an increased interest in the use of fiber reinforced polymer (FRP) in the construction industry. However, the E-modulus and strength of such members at high service temperatures is still unknown. Modulus and strength of FRP at high service temperatures are highly required parameters for full design. The knowledge and application of this could lead to a cost effective and practical consideration in fire safety design. Thus, this paper proposes design methods for calculating the E-modulus and strength of FRP members at different temperatures. Experimental data from literature were normalized and compared with the results predicted by this method. It was found that the proposed design methods conservatively estimate the E-modulus and strength of FRP structural members. In addition, comparison was also made with direct references to the real behavior of materials. It was found to be satisfactory. Finally, an application is provided.

关键词: concrete     fiber reinforced polymer     E-modulus     strength     temperatures    

An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1654-1654 doi: 10.1007/s11709-020-0622-7

Advanced cement based nanocomposites reinforced with MWCNTs and CNFs

Emmanuel E. GDOUTOS,Maria S. KONSTA-GDOUTOS,Panagiotis A. DANOGLIDIS,Surendra P. SHAH

《结构与土木工程前沿(英文)》 2016年 第10卷 第2期   页码 142-149 doi: 10.1007/s11709-016-0342-1

摘要: Cementitious materials reinforced with well dispersed multiwall carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) at the nanoscale were fabricated and tested. The MWCNTs and CNFs were dispersed by the application of ultrasonic energy and the use of a superplasticizer. Mechanical and fracture properties including flexural strength, Young’s modulus, flexural and fracture toughness were measured and compared with similarly processed reference cement based mixes without the nano-reinforcement. The MWCNTs and CNFs reinforced mortars exhibited superior properties demonstrated by a significant improvement in flexural strength (106%), Young’s modulus (95%), flexural toughness (105%), effective crack length (30%) and fracture toughness (120%).

关键词: multi-walled carbon nanotubes     carbon nanofibers     mortars     toughness     Young’s modulus    

Empirical models and design codes in prediction of modulus of elasticity of concrete

Behnam VAKHSHOURI, Shami NEJADI

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 38-48 doi: 10.1007/s11709-018-0479-1

摘要: Modulus of Elasticity (MOE) is a key parameter in reinforced concrete design. It represents the stress-strain relationship in the elastic range and is used in the prediction of concrete structures. Out of range estimation of MOE in the existing codes of practice strongly affect the design and performance of the concrete structures. This study includes: (a) evaluation and comparison of the existing analytical models to estimating the MOE in normal strength concrete, and (b) proposing and verifying a new model. In addition, a wide range of experimental databases and empirical models to estimate the MOE from compressive strength and density of concrete are evaluated to verification of the proposed model. The results show underestimation of MOE of conventional concrete in majority of the existing models. Also, considering the consistency between density and mechanical properties of concrete, the predicted MOE in the models including density effect, are more compatible with the experimental results.

关键词: modulus of elasticity     normal strength normal weight concrete     empirical models     design codes     compressive strength     density    

Elastic modulus and thermal stress in coating during heat cycling with different substrate shapes

Daniel GAONA,Alfredo VALAREZO

《机械工程前沿(英文)》 2015年 第10卷 第3期   页码 294-300 doi: 10.1007/s11465-015-0351-0

摘要:

The elastic modulus of a deposit (Ed) can be obtained by monitoring the temperature (?T) and curvature (?k) of a one-side coated long plate, namely, a one-dimensional (1D) deformation model. The aim of this research is to design an experimental setup that proves whether a 1D deformation model can be scaled for complex geometries. The setup includes a laser displacement sensor mounted on a robotic arm capable of scanning a specimen surface and measuring its deformation. The reproducibility of the results is verified by comparing the present results with Stony Brook University Laboratory’s results. The ?k-?T slope error is less than 8%, and the Ed estimation error is close to 2%. These values reveal the repeatability of the experiments. Several samples fabricated with aluminum as the substrate and 100MXC nanowire (Fe and Cr alloy) as the deposit are analyzed and compared with those in finite element (FE) simulations. The linear elastic behavior of 1D (flat long plate) and 2D (squared plate) specimens during heating/cooling cycles is demonstrated by the high linearity of all ?k-?T curves (over 97%). The Ed values are approximately equal for 1D and 2D analyses, with a median of 96 GPa and standard deviation of 2 GPa. The correspondence between the experimental and simulated results for the 1D and 2D specimens reveals that deformation and thermal stress in coated specimens can be predicted regardless of specimen geometry through FE modeling and by using the experimental value of Ed. An example of a turbine-blade-shaped substrate is presented to validate the approach.

关键词: in-plane     Young’s modulus     curvature temperature     thermal stress     coating    

Prediction of falling weight deflectometer parameters using hybrid model of genetic algorithm and adaptive neuro-fuzzy inference system

《结构与土木工程前沿(英文)》   页码 812-826 doi: 10.1007/s11709-023-0940-7

摘要: A falling weight deflectometer is a testing device used in civil engineering to measure and evaluate the physical properties of pavements, such as the modulus of the subgrade reaction (Y1) and the elastic modulus of the slab (Y2), which are crucial for assessing the structural strength of pavements. In this study, we developed a novel hybrid artificial intelligence model, i.e., a genetic algorithm (GA)-optimized adaptive neuro-fuzzy inference system (ANFIS-GA), to predict Y1 and Y2 based on easily determined 13 parameters of rigid pavements. The performance of the novel ANFIS-GA model was compared to that of other benchmark models, namely logistic regression (LR) and radial basis function regression (RBFR) algorithms. These models were validated using standard statistical measures, namely, the coefficient of correlation (R), mean absolute error (MAE), and root mean square error (RMSE). The results indicated that the ANFIS-GA model was the best at predicting Y1 (R = 0.945) and Y2 (R = 0.887) compared to the LR and RBFR models. Therefore, the ANFIS-GA model can be used to accurately predict Y1 and Y2 based on easily measured parameters for the appropriate and rapid assessment of the quality and strength of pavements.

关键词: falling weight deflectometer     modulus of subgrade reaction     elastic modulus     metaheuristic algorithms    

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

《结构与土木工程前沿(英文)》 2011年 第5卷 第2期   页码 199-207 doi: 10.1007/s11709-011-0102-1

摘要: Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities. Firstly, validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars. The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied. It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation. Wave attenuation as well as time delay is affected by the length, quantity, specific stiffness of the distributed microcracks as well as the incident stress wave frequency. The storage and loss moduli of the defected rock are also affected by the microcrack properties; however, they are independent of incident stress wave frequency.

关键词: stress wave propagation     defected rock     numerical manifold method     viscoelastic behavior     storage modulus     loss modulus    

Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using

Mosbeh R. KALOOP, Alaa R. GABR, Sherif M. EL-BADAWY, Ali ARISHA, Sayed SHWALLY, Jong WAN HU

《结构与土木工程前沿(英文)》 2019年 第13卷 第6期   页码 1379-1392 doi: 10.1007/s11709-019-0562-2

摘要: To date, very few researchers employed the Least Square Support Vector Machine (LSSVM) in predicting the resilient modulus ( ) of Unbound Granular Materials (UGMs). This paper focused on the development of a LSSVM model to predict the of recycled materials for pavement applications and comparison with other different models such as Regression, and Artificial Neural Network (ANN). Blends of Recycled Concrete Aggregate (RCA) with Recycled Clay Masonry (RCM) with proportions of 100/0, 90/10, 80/20, 70/30, 55/45, 40/60, 20/80, and 0/100 by the total aggregate mass were evaluated for use as UGMs. RCA/RCM materials were collected from dumps on the sides of roads around Mansoura city, Egypt. The investigated blends were evaluated experimentally by routine and advanced tests and the values were determined by Repeated Load Triaxial Test (RLTT). Regression, ANN, and LSSVM models were utilized and compared in predicting the of the investigated blends optimizing the best design model. Results showed that the ’s of the investigated RCA/RCM blends were generally increased with the decrease in RCM proportion. Statistical analyses were utilized for evaluating the performance of the developed models and the inputs sensitivity parameters. Eventually, the results approved that the LSSVM model can be used as a novel tool to estimate the of the investigated RCA/RCM blends.

关键词: Least Square Support Vector Machine     Artificial Neural Network     resilient modulus     Recycled Concrete Aggregate     Recycled Clay Masonry    

Assessing artificial neural network performance for predicting interlayer conditions and layer modulus

Lingyun YOU, Kezhen YAN, Nengyuan LIU

《结构与土木工程前沿(英文)》 2020年 第14卷 第2期   页码 487-500 doi: 10.1007/s11709-020-0609-4

摘要: The objective of this study is to evaluate the performance of the artificial neural network (ANN) approach for predicting interlayer conditions and layer modulus of a multi-layered flexible pavement structure. To achieve this goal, two ANN based back-calculation models were proposed to predict the interlayer conditions and layer modulus of the pavement structure. The corresponding database built with ANSYS based finite element method computations for four types of a structure subjected to falling weight deflectometer load. In addition, two proposed ANN models were verified by comparing the results of ANN models with the results of PADAL and double multiple regression models. The measured pavement deflection basin data was used for the verifications. The comparing results concluded that there are no significant differences between the results estimated by ANN and double multiple regression models. PADAL modeling results were not accurate due to the inability to reflect the real pavement structure because pavement structure was not completely continuous. The prediction and verification results concluded that the proposed back-calculation model developed with ANN could be used to accurately predict layer modulus and interlayer conditions. In addition, the back-calculation model avoided the back-calculation errors by considering the interlayer condition, which was barely considered by former models reported in the published studies.

关键词: asphalt pavement     interlayer conditions     finite element method     artificial neural network     back-calculation    

Sustainability of metal recovery from E-waste

Biswajit Debnath, Ranjana Chowdhury, Sadhan Kumar Ghosh

《环境科学与工程前沿(英文)》 2018年 第12卷 第6期 doi: 10.1007/s11783-018-1044-9

摘要:

Metal recovery techniques from electronic waste reported in literature.

Metal recovery processes followed in Industries from electronic waste.

Sustainability analysis of metal recovery processes from electronic waste.

关键词: E-waste     Metal recovery     Metal Recovery from E-waste (MREW)     Sustainability    

The stress relaxation of cement clinkers under high temperature

Xiufang WANG,Yiwang BAO,Xiaogen LIU,Yan QIU

《机械工程前沿(英文)》 2015年 第10卷 第4期   页码 413-417 doi: 10.1007/s11465-015-0357-7

摘要:

The energy consumption of crushing is directly affected by the mechanical properties of cement materials. This research provides a theoretical proof for the mechanism of the stress relaxation of cement clinkers under high temperature. Compression stress relaxation under various high temperatures is discussed using a specially developed load cell, which can measure stress and displacement under high temperatures inside an autoclave. The cell shows that stress relaxation dramatically increases and that the remaining stress rapidly decreases with an increase in temperature. Mechanical experiments are conducted under various temperatures during the cooling process to study the changes in the grinding resistance of the cement clinker with temperature. The effects of high temperature on the load-displacement curve, compressive strength, and elastic modulus of cement clinkers are systematically studied. Results show that the hardening phenomenon of the clinker becomes apparent with a decrease in temperature and that post-peak behaviors manifest characteristics of the transformation from plasticity to brittleness. The elastic modulus and compressive strength of cement clinkers increase with a decrease in temperature. The elastic modulus increases greatly when the temperature is lower than 1000 °C. The compressive strength of clinkers increases by 73.4% when the temperature drops from 1100 to 800 °C.

关键词: stress relaxation     high temperature     cement clinker     compression     elastic modulus    

risks of heavy metals, polybrominated diphenyl ethers, and polychlorinated dibenzo-dioxins/furans at e-waste

《环境科学与工程前沿(英文)》 2023年 第17卷 第7期 doi: 10.1007/s11783-023-1679-z

摘要:

● Heavy metals and organic toxins may persist in legacy sites for a long time.

关键词: E-waste     Human health risk     Organ risk     Heavy metal toxicity     PBDE     PCDD/F    

Molecular dynamics modeling of a single diamond abrasive grain in grinding

SAVVOPOULOS,Nikolaos E. KARKALOS,Dimitrios E. MANOLAKOS

《机械工程前沿(英文)》 2015年 第10卷 第2期   页码 168-175 doi: 10.1007/s11465-015-0337-y

摘要:

In this paper the nano-metric simulation of grinding of copper with diamond abrasive grains, using the molecular dynamics (MD) method, is considered. An MD model of nano-scale grinding, where a single diamond abrasive grain performs cutting of a copper workpiece, is presented. The Morse potential function is used to simulate the interactions between the atoms involved in the procedure. In the proposed model, the abrasive grain follows a curved path with decreasing depth of cut within the workpiece to simulate the actual material removal process. Three different initial depths of cut, namely 4 ?, 8 ? and 12 ?, are tested, and the influence of the depth of cut on chip formation, cutting forces and workpiece temperatures are thoroughly investigated. The simulation results indicate that with the increase of the initial depth of cut, average cutting forces also increase and therefore the temperatures on the machined surface and within the workpiece increase as well. Furthermore, the effects of the different values of the simulation variables on the chip formation mechanism are studied and discussed. With the appropriate modifications, the proposed model can be used for the simulation of various nano-machining processes and operations, in which continuum mechanics cannot be applied or experimental techniques are subjected to limitations.

关键词: molecular dynamics     abrasive process     chip formation     cutting force     temperature    

Policy options for Agriculture Green Development by farmers in China

Laurence E. D. SMITH

《农业科学与工程前沿(英文)》 2020年 第7卷 第1期   页码 90-97 doi: 10.15302/J-FASE-2019290

摘要:

Farmers are the key agents who manage land and water. Agriculture Green Development (AGD) requires a transformation in farming from high resource consumption and environmental cost to sustainable intensification with high productivity, high resource use efficiency and low environmental risk. This paper analyzes the public policy challenge of AGD and makes the case for a location-sensitive policy mix made up of regulation, advice provision, voluntarism and targeted incentives. The public agricultural extension service in China is a key resource, but one that requires reorientation and reform with the aim of better balancing high farm productivity with environmental protection.

关键词: agriculture     environment     development     incentives     policy     regulation    

数字采矿技术在岩爆风险评估中的应用

Sousa Luis Ribeiro e,Miranda Tiago,Sousa Rita Leal e,Tinoco Joaquim

《工程(英文)》 2017年 第3卷 第4期   页码 552-558 doi: 10.1016/J.ENG.2017.04.002

摘要:

目前在世界范围内的很多地下矿山,岩爆已经成为一个与矿山采矿生产密切相关的重要现象。深入理解这类现象,不仅有助于岩爆管理,而且还有可能节约采矿成本,减少人身伤亡事故。其中,实验室实验是深入研究岩爆机理的一个重要途径。在本文作者前期的研究中,已经建立了实验室岩爆实验数据库。与此同时,借助于数字采矿技术,也建立了岩爆最大应力和岩爆风险指数的预测模型。为实现基于矿山地质条件和矿山井巷建筑结构特性对岩爆类型即岩爆强度等级的准确预测,本文的重点是,基于对岩爆实例的分析来建立岩爆影响矩阵,明确岩爆现象的诱发因子,并厘清这些影响因子之间的相互关系。运用人工神经网络(ANN)和初始贝叶斯分类器等数字矿山技术,对矿山岩爆数据库进行了更深入的研究。最后给出了研究得出的各项结论。

关键词: 岩爆     数字采矿     贝叶斯网络     原位数据库    

标题 作者 时间 类型 操作

An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

期刊论文

An improved design method to predict the E-modulus and strength of FRP composites at different temperatures

Mohammed FARUQI, Gobishanker RAJASKANTHAN, Breanna BAILEY, Francisco AGUINIGA

期刊论文

Advanced cement based nanocomposites reinforced with MWCNTs and CNFs

Emmanuel E. GDOUTOS,Maria S. KONSTA-GDOUTOS,Panagiotis A. DANOGLIDIS,Surendra P. SHAH

期刊论文

Empirical models and design codes in prediction of modulus of elasticity of concrete

Behnam VAKHSHOURI, Shami NEJADI

期刊论文

Elastic modulus and thermal stress in coating during heat cycling with different substrate shapes

Daniel GAONA,Alfredo VALAREZO

期刊论文

Prediction of falling weight deflectometer parameters using hybrid model of genetic algorithm and adaptive neuro-fuzzy inference system

期刊论文

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

期刊论文

Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using

Mosbeh R. KALOOP, Alaa R. GABR, Sherif M. EL-BADAWY, Ali ARISHA, Sayed SHWALLY, Jong WAN HU

期刊论文

Assessing artificial neural network performance for predicting interlayer conditions and layer modulus

Lingyun YOU, Kezhen YAN, Nengyuan LIU

期刊论文

Sustainability of metal recovery from E-waste

Biswajit Debnath, Ranjana Chowdhury, Sadhan Kumar Ghosh

期刊论文

The stress relaxation of cement clinkers under high temperature

Xiufang WANG,Yiwang BAO,Xiaogen LIU,Yan QIU

期刊论文

risks of heavy metals, polybrominated diphenyl ethers, and polychlorinated dibenzo-dioxins/furans at e-waste

期刊论文

Molecular dynamics modeling of a single diamond abrasive grain in grinding

SAVVOPOULOS,Nikolaos E. KARKALOS,Dimitrios E. MANOLAKOS

期刊论文

Policy options for Agriculture Green Development by farmers in China

Laurence E. D. SMITH

期刊论文

数字采矿技术在岩爆风险评估中的应用

Sousa Luis Ribeiro e,Miranda Tiago,Sousa Rita Leal e,Tinoco Joaquim

期刊论文