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Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened tubular steel T-joints

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

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论岩土塑性体应变与剪应变的相互作用原理

王靖涛

《中国工程科学》 2006年第8卷第9期页码 24-29

摘要：

对岩土塑性变形过程中体应变与剪应变的相互作用原理的内涵做了深入的阐述，特别对塑性体应变和剪应变之间的相互作用方式，塑性体应变对抗剪能力的直接控制作用，剪缩和剪胀发生的条件，应力路径相关性是这种相互作用的综合体现及实例验证，临界状态是塑性和弹性体应变都保持不变的纯粹剪切变形过程等方面进行了论证；根据这个相互作用原理，在理论上证明了空间临界状态线的存在性和唯一性以及它与应力是无关的。

关键词：岩土塑性体变形和剪应变的相互作用原理岩土本构关系压硬性剪胀性

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A model for creep life prediction of thin tube using strain energy density as a function of stress triaxialityunder quasi-static loading employing elastic-creep & elastic-plastic-creep deformation

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

《机械工程前沿（英文）》 2013年第8卷第2期页码 181-186 doi: 10.1007/s11465-013-0257-7

摘要：

This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-creep and elastic-plastic-creep finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.

关键词： elastic-creep elastic-plastic-creep stress triaxiality life prediction pressure vessels finite element analysis (FEA)

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The formation mechanism and the influence factor of residual stress in machining

null

《机械工程前沿（英文）》 2014年第9卷第3期页码 265-269 doi: 10.1007/s11465-014-0311-0

摘要：

Residual stresses generated in cutting process have important influences on workpiece performance. The paper presents a method of theoretical analysis in order to explicate the formation mechanism of residual stresses in cutting. An important conclusion is drawn that the accumulated plastic strain is the main factor which determines the nature and the magnitude of surface residual stresses in the workpiece. On the basis of the analytical model for residual stress, a series of simulations for residual stress prediction during cutting AISI 1045 steel are implemented in order to obtain the influences of cutting speed, depth of cut and tool edge radius on surface residual stress in the workpiece. And these influences are explained from the perspective of formation mechanism of residual stress in cutting. The conclusions have good applicability and can be used to guide the parameters selection in actual production.

关键词： residual stress analytical model strain plastic cutting parameter

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A modified zone model for estimating equivalent room thermal capacity

Hua CHEN, Xiaolin WANG

《能源前沿（英文）》 2013年第7卷第3期页码 351-357 doi: 10.1007/s11708-013-0254-x

摘要： The zone model has been widely applied in control analysis of heating, ventilation and air conditioning (HVAC) systems to achieve a high building efficiency. This paper proposed a modified zone model which is much simpler in the HVAC system simulation and has the similar accuracy to the complicated simulation model. The proposed model took into consideration the effect of envelop heat reservoir on the room indoor temperature by introducing the thermal admittance of the inner surfaces of the building enclosure. The thermal admittance for the building enclosure was developed based on the building thermal network analytical theory and transfer function method. The efficacy of the proposed model was demonstrated by comparing it with the complicated model — heat balance method (HTB2 program). The predicted results from the proposed model well agreed with those from the complicated simulation. The proposed model can then make the HVAC system dynamic simulation much faster and more acceptable for control design due to its simplicity and efficiency.

关键词： room model thermal network analysis transfer function heating ventilation and air conditioning (HVAC) system simulation

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Distribution of background equivalent static wind load on high-rise buildings

Jianguo ZHANG , Ming GU ,

《结构与土木工程前沿（英文）》 2009年第3卷第3期页码 241-248 doi: 10.1007/s11709-009-0036-z

摘要： In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel. Some typical methods proposed in some relative literatures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods, are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use.

关键词： high-rise buildings along-wind cross-wind background equivalent static wind load close formulae

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Moving policy and regulation forward for single-use plastic alternatives

《环境科学与工程前沿（英文）》 2021年第15卷第3期 doi: 10.1007/s11783-021-1423-5

摘要： Single-use plastics are often used once or cannot be reused for extended periods. They are widely consumed with the rapid development of social economy. The waste generated by single-use plastics threatens ecosystem health by entering the environment and ultimately restricts sustainable human development. The innovation of sustainable and environmentally friendly single-use plastic alternative materials and the joint participation of governments, enterprises and the public are promising technologies and management approaches that can solve the problem of single-use plastics wastes. The development of single-use plastic alternative products can be promoted fundamentally only by improving relevant legislation and standards, providing differentiated industrial policies, encouraging scientific and technological innovation and expanding public participation.

关键词： Single-use plastic alternatives Policy Regulation Sustainable development

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China’s new problems of food security revealed by the Food Equivalent Unit

Huilong LIN,Ruichao LI,Cangyu JIN,Chong WANG,Maohong WEI,Jizhou REN

《农业科学与工程前沿（英文）》 2014年第1卷第1期页码 69-76 doi: 10.15302/J-FASE-2014023

摘要： China's food security has a great influence on the world, and has always been the top priority in China. In recent years, as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing, research based on nutrition security and broad food systems are increasingly needed in today’s China. Thus, not only grain for human consumption, but also animal foods have been integrated into the Food Equivalent, which is used to analyze China’s current agriculture system and reveal the water resource distribution. The results indicated that the average animal food consumption has risen by 78.6%, and now China’s daily supply of animal food per capita has reached about 50% of that in the USA and 80% of that in the South Korea. So there exist an obvious disparity in animal food supply between China and these two countries. It is impossible for the China’s current agricultural system to achieve the level in the USA. Under China’s current agricultural system, the consumption proportion of feed grain had surpassed the consumption of food grain, increased sharply from 33% in 1992 to 67% in 2011. However, the growth potential of total grain output is approaching an upper limit, so the continued growth of feed grain demand exerts great pressure on the China’s food supply. The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security. China’s current “grain farming” cannot meet the demand of increasing nutrition and appropriate resource utilization. The implementation of grassland agriculture appears feasible and necessary for saving feed grain, providing a large number of high-quality animal foods and appropriate water resource utilization.

关键词： food security nutrition security food equivalent unit grassland agriculture China

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Equivalent circuit and characteristic simulation of a brushless electrically excited synchronous wind

Hao WANG, Fengge ZHANG, Tao GUAN, Siyang YU

《机械工程前沿（英文）》 2017年第12卷第3期页码 420-426 doi: 10.1007/s11465-017-0439-9

摘要：

A brushless electrically excited synchronous generator (BEESG) with a hybrid rotor is a novel electrically excited synchronous generator. The BEESG proposed in this paper is composed of a conventional stator with two different sets of windings with different pole numbers, and a hybrid rotor with powerful coupling capacity. The pole number of the rotor is different from those of the stator windings. Thus, an analysis method different from that applied to conventional generators should be applied to the BEESG. In view of this problem, the equivalent circuit and electromagnetic torque expression of the BEESG are derived on the basis of electromagnetic relation of the proposed generator. The generator is simulated and tested experimentally using the established equivalent circuit model. The experimental and simulation data are then analyzed and compared. Results show the validity of the equivalent circuit model.

关键词： wind power brushless electrically excited synchronous generator hybrid rotor equivalent circuit

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Current scenario and challenges of plastic pollution in Bangladesh: a focus on farmlands and terrestrial

《环境科学与工程前沿（英文）》 2023年第17卷第6期 doi: 10.1007/s11783-023-1666-4

摘要：

● A global snapshot of plastic waste generation and disposal is analysed.

关键词： Plastic waste Farmlands Terrestrial ecosystem Marine life

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Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

《结构与土木工程前沿（英文）》 2012年第6卷第3期页码 210-216 doi: 10.1007/s11709-012-0165-7

摘要： A uniaxial tension test is commonly used to determine the mechanical properties of steel, but it has no meaning for the response of the material in a structure. The test was developed as a consensus solution by producers, fabricators, designers and code writers, to have a standard by which similar materials could be compared to a common base. It does not represent the actual behavior of the steel in a structure, and was never intended to do so. To study the true behavior of the structure and how the material responds it would be better to determine the strains and deformations that will take place during actual service condition. Such characteristics reflect the real behavior, whether in the elastic or inelastic range. If stresses or forces are needed, these are easily determined by the value of the strain and the relevant material modulus, along with the type of cross section, whether elastic or inelastic. The paper addresses the properties of a range of structural steels, how these are incorporated into design standards and how the standards define deformation characteristics and demands for bolted and welded connections.

关键词： steel stress-strain characteristics tension test strain design actual behavior improved design codes

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广义塑性力学及其运用

郑颖人,孔亮

《中国工程科学》 2005年第7卷第11期页码 21-36

摘要：

分析了经典塑性力学用于岩土类材料的问题，它采用了3个不符合岩土材料变形机制的假设。从固体力学原理直接导出广义塑性位势理论，将经典塑性力学改造为更一般的塑性力学——广义塑性力学。广义塑性力学采用了塑性力学中的分量理论，能反映应力路径转折的影响，并避免了采用正交流动法则所引起的过大剪胀等不合理现象，也不会产生当前非关联流动法则中任意假定塑性势面引起的误差。给出了广义塑性力学的屈服面理论、硬化定律和应力-应变关系，并建立了考虑应力主轴旋转的广义塑性位势理论。屈服条件是状态参数，也是试验参数，只能由试验给出。应用表明，广义塑性力学可作为岩土材料的建模理论，还可应用于诸如极限分析等土力学的诸多领域，具有广阔的应用前景。

关键词：岩土塑性力学广义塑性力学塑性势屈服面本构模型

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Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

《结构与土木工程前沿（英文）》 2022年第16卷第1期页码 86-98 doi: 10.1007/s11709-021-0793-x

摘要： One of the strategic materials used in earth-fill embankment dams and in modifying and preventing groundwater flow is plastic concrete (PlC). PlC is comprised of aggregates, water, cement, and bentonite. Natural zeolite (NZ) is a relatively abundant mineral resource and in this research, the microstructure, unconfined strength, triaxial behavior, and permeability of PlC made with 0%, 10%, 15%, 20%, and 25% replacement of cement by NZ were studied. Specimens of PIC-NZ were subjected to confined conditions and three different confining pressures of 200, 350, and 500 kPa were used to investigate their mechanical behavior and permeability. To study the effect of sulfate ions on the properties of PlC-NZ specimens, the specimens were cured in one of two different environments: normal condition and in the presence of sulfate ions. Results showed that increasing the zeolite content decreases the unconfined strength, elastic modulus, and peak strength of PlC-NZ specimens at the early ages of curing. However, at the later ages, increasing the zeolite content increases unconfined strength as well as the peak strength and elastic modulus. Specimens cured in the presence of sulfate ions indicated lower permeability, higher unconfined strength, elastic modulus, and peak strength due to having lower porosity.

关键词： plastic concrete sulfate resistance natural zeolite triaxial compression test SEM permeability

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Fault classification and reconfiguration of distribution systems using equivalent capacity margin method

K. Sathish KUMAR, T. JAYABARATHI

《能源前沿（英文）》 2012年第6卷第4期页码 394-402 doi: 10.1007/s11708-012-0211-0

摘要： This paper investigates the capability of support vector machines (SVM) for prediction of fault classification and the use of the concept of equivalent capacity margin (ECM) for restoration of the power system. The SVM, as a novel type of machine learning based on statistical learning theory, achieves good generalization ability by adopting a structural risk minimization (SRM) induction principle aimed at minimizing a bound on the generalization error of a model rather than the minimization of the error on the training data only. Here, the SVM has been used as a classification. The inputs of the SVM model are power and voltage values. An equation has been developed for the prediction of the fault in the power system based on the developed SVM model. The next steps of this paper are the restoration and reconfiguration by using the ECM concept, the development of a code, and the testing of the results with various load outages, which have been executed for a 12 load system.

关键词： support vector machines (SVM) structural risk minimization (SRM) equivalent capacity margin (ECM) restoration fault classification

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Preventing masks from becoming the next plastic problem

《环境科学与工程前沿（英文）》 2021年第15卷第6期 doi: 10.1007/s11783-021-1413-7

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标题作者时间类型操作

Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened tubular steel T-joints

Peng DENG, Boyi YANG, Xiulong CHEN, Yan LIU

期刊论文

论岩土塑性体应变与剪应变的相互作用原理

王靖涛

期刊论文

A model for creep life prediction of thin tube using strain energy density as a function of stress triaxialityunder quasi-static loading employing elastic-creep & elastic-plastic-creep deformation

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

期刊论文

The formation mechanism and the influence factor of residual stress in machining

null

期刊论文

A modified zone model for estimating equivalent room thermal capacity

Hua CHEN, Xiaolin WANG

期刊论文

Distribution of background equivalent static wind load on high-rise buildings

Jianguo ZHANG , Ming GU ,

期刊论文

Moving policy and regulation forward for single-use plastic alternatives