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Observation of black carbon aerosol in Beijing, 2003

LOU Shujuan, MAO Jietai, WANG Meihua

《环境科学与工程前沿（英文）》 2007年 第1卷 第3期   页码 345-349 doi: 10.1007/s11783-007-0059-4

摘要： The objective of this study was to determine the black carbon concentration in Beijing in 2003. The aerosol properties were measured using an Aethalometer and a tapered element oscillating microbalance (TEOM) on the roof of the Physics Building of Peking University (39.99º N, 116.31º E) from July to August 2003 and from November 2003 to January 2004. The average black carbon (BC) concentrations in the summer and winter were 8.80 and 11.4 μg/m, respectively. During winter, two different cyclone cut offs were installed at the inlet of an aethalometer. The BC mass concentration in TSP, PM, and PM were obtained. The results indicated that in winter aerosol, 90% of BC exited in PM and 82.6% of BC exited in PM. The BC in PM accounted for 5.11% of the PM mass.

关键词： carbon concentration     Beijing     tapered element     August     aethalometer    

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Effect of bond enhancement using carbon nanotubes on flexural behavior of RC beams strengthened with

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 131-143 doi: 10.1007/s11709-021-0787-8

摘要： This paper studied the effect of incorporation of carbon nanotubes (CNTs) in carbon fiber reinforced polymer (CFRP) on strengthening of reinforced concrete (RC) beams. The RC beams were prepared, strengthened in flexure by externally bonded CFRP or CNTs-modified CFRP sheets, and tested under four-point loading. The experimental results showed the ability of the CNTs to delay the initiation of the cracks and to enhance the flexural capacity of the beams strengthened with CFRP. A nonlinear finite element (FE) model was built, validated, and used to study the effect of various parameters on the strengthening efficiency of CNTs-modified CFRP. The studied parameters included concrete strength, flexural reinforcement ratio, and CFRP sheet configuration. The numerical results showed that utilization of CNTs in CFRP production improved the flexural capacity of the strengthened beams for U-shape and underside-strip configurations. The enhancement was more pronounced in the case of U-shape than in the case of use of sheet strip covers on the underside of the beam. In case of using underside-strip, the longer or the wider the sheet, the higher was the flexural capacity of the beams. The flexural enhancement of RC beams by strengthening with CNTs-modified CFRP decreased with increasing the rebar diameter and was not affected by concrete strength.

关键词： RC beams     flexural     strengthening     CFRP     CNTs     finite element    

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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    

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Characteristics of chemical components in PM

Jianwu SHI,Xiang DING,Yue ZHOU,Ran YOU,Lu HUANG,Jiming HAO,Feng XIANG,Jian YANG,Ze SHI,Xinyu HAN,Ping NING

《环境科学与工程前沿（英文）》 2016年 第10卷 第5期 doi: 10.1007/s11783-016-0841-2

摘要： The mass concentrations of PM were studied at a plateau city. Seasonal and spatial variation of chemical components in PM were analyzed. Primary emissions were the main contributors of PM . A sampling campaign including summer, autumn and winter of 2014 and spring of 2015 was accomplished to obtain the characteristic of chemical components in PM at three sites of Kunming, a plateau city in South-west China. Nine kinds of water-soluble inorganic ions (WSI), organic and element carbon (OC and EC) in PM were analyzed by ion chromatography and thermal optical reflectance method, respectively. Results showed that the average concentrations of total WSI, OC and EC were 22.85±10.95 μg·m , 17.83±9.57 μg·m and 5.11±4.29 μg·m , respectively. They totally accounted for 53.0% of PM . Secondary organic and inorganic aerosols (SOA and SIA) were also assessed by the minimum ratio of OC/EC, nitrogen and sulfur oxidation ratios. The annual average concentrations of SOA and SIA totally accounted for 28.3% of the PM concentration. The low proportion suggested the primary emission was the main source of PM in Kunming. However, secondary pollution in the plateau city should also not be ignorable, due to the appropriate temperature and strong solar radiation, which can promote the atmospheric photochemical reactions.

关键词： PM2.5     Plateau city     Organic carbon     Element carbon     Inorganic ions     Secondary components    

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Acoustic analysis of lightweight auto-body based on finite element method and boundary element method

LIANG Xinhua, ZHU Ping, LIN Zhongqin, ZHANG Yan

《机械工程前沿（英文）》 2007年 第2卷 第1期   页码 99-103 doi: 10.1007/s11465-007-0017-7

摘要： A lightweight automotive prototype using alternative materials and gauge thickness is studied by a numerical method. The noise, vibration, and harshness (NVH) performance is the main target of this study. In the range of 1 150 Hz, the frequency response function (FRF) of the body structure is calculated by a finite element method (FEM) to get the dynamic behavior of the auto-body structure. The pressure response of the interior acoustic domain is solved by a boundary element method (BEM). To find the most contributing panel to the inner sound pressure, the panel acoustic contribution analysis (PACA) is performed. Finally, the most contributing panel is located and the resulting structural optimization is found to be more efficient.

关键词： harshness     automotive prototype     structural optimization     vibration     efficient    

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Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

《机械工程前沿（英文）》 2014年 第9卷 第1期   页码 41-49 doi: 10.1007/s11465-014-0284-z

摘要：

In this paper, the thermal buckling behavior of composite laminated plates under a uniform temperature distribution is studied. A finite element of four nodes and 32 degrees of freedom (DOF), previously developed for the bending and mechanical buckling of laminated composite plates, is extended to investigate the thermal buckling behavior of laminated composite plates. Based upon the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical implementation of the present finite element allowed the comparison of the numerical obtained results with results obtained from the literature: 1) with element of the same order, 2) the first order shear deformation theory, 3) the high order shear deformation theory and 4) the three-dimensional solution. It was found that the obtained results were very close to the reference results and the proposed element offers a good convergence speed. Furthermore, a parametrical study was also conducted to investigate the effect of the anisotropy of composite materials on the critical buckling temperature of laminated plates. The study showed that: 1) the critical buckling temperature generally decreases with the increasing of the modulus ratio EL/ET and thermal expansion ratio αT/αL, and 2) the boundary conditions and the orientation angles significantly affect the critical buckling temperature of laminated plates.

关键词： thermal buckling     laminated composite plates     anisotropy     critical buckling temperature     finite-element method     high precision rectangular Hermitian element    

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Special Column on Multiscale Stochastic Finite Element Method

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 105-106 doi: 10.1007/s11709-015-0297-7

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Comparison of indirect boundary element and finite element methods A case study: Shiraz-Esfahan railway

Amin MANOUCHEHRIAN, Mohammad Fatehi MARJI, Mohsen MOHEBBI

《结构与土木工程前沿（英文）》 2012年 第6卷 第4期   页码 385-392 doi: 10.1007/s11709-012-0173-7

摘要： Because of the high importance of transportation tunnels, most precise analyses of stress concentration and displacement around them are essential to provide safety of them as much as possible. Recently, various numerical methods such as finite element method (FEM), discrete element method (DEM), finite difference method (FDM) and boundary element method (BEM) have been used extremely in geosciences problems, but among these numerical methods, BEM has been used less than others because the computational algorithm is not so straightforward. This paper suggests the implementation of the indirect boundary element method (IBEM) as a formulation of BEM to analyze displacement around Shiraz-Esfahan railway tunnel in Zagros Mountains southwest of Iran. For this purpose, this tunnel has been modeled numerically using two-dimensional fictitious stress method (TWOFS) algorithm. To validate the results, they were compared with FEM results as a commonly used numerical method. Results of current theoretical study have shown that the presented approach using IBEM is reasonably accurate and can be used for analysis of displacement in geosciences problems. In rock mechanics, for problems with a low ratio of boundary surface to volume, FEM is not very well suited and may be cumbersome, but use of such a proposed IBEM approach can be particularly attractive.

关键词： indirect boundary element method     finite element method     displacement     tunnel     case study    

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Finite element analysis of controlled low strength materials

Vahid ALIZADEH

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1243-1250 doi: 10.1007/s11709-019-0553-3

摘要： Controlled low strength materials (CLSM) are flowable and self-compacting construction materials that have been used in a wide variety of applications. This paper describes the numerical modeling of CLSM fills with finite element method under compression loading and the bond performance of CLSM and steel rebar under pullout loading. The study was conducted using a plastic-damage model which captures the material behavior using both classical theory of elasto-plasticity and continuum damage mechanics. The capability of the finite element approach for the analysis of CLSM fills was assessed by a comparison with the experimental results from a laboratory compression test on CLSM cylinders and pullout tests. The analysis shows that the behavior of a CLSM fill while subject to a failure compression load or pullout tension load can be simulated in a reasonably accurate manner.

关键词： CLSM     finite element method     compressive strength     pullout     numerical modeling     plastic damage model    

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The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 456-477 doi: 10.1007/s11709-019-0519-5

摘要：

The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.

关键词： computational method     finite element method     smoothed finite element method     strain smoothing technique     smoothing domain     weakened weak form     solid mechanics     softening effect     upper bound solution    

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Finite element modeling of thermo-active diaphragm walls

Yi RUI, Mei YIN

《结构与土木工程前沿（英文）》 2020年 第14卷 第3期   页码 646-663 doi: 10.1007/s11709-020-0584-9

摘要： There are two major challenges faced by modern society: energy security, and lowering carbon dioxide gas emissions. Thermo-active diaphragm walls have a large potential to remedy one of these problems, since they are a renewable energy technology that uses underground infrastructure as a heat exchange medium. However, extensive research is required to determine the effects of cyclic heating and cooling on their geotechnical and structural performance. In this paper, a series of detailed finite element analyses are carried out to capture the fully coupled thermo-hydro-mechanical response of the ground and diaphragm wall. It is demonstrated that the thermal operation of the diaphragm wall causes changes in soil temperature, thermal expansion/shrinkage of pore water, and total stress applied on the diaphragm wall. These, in turn, cause displacements of the diaphragm wall and variations of the bending moments. However, these effects on the performance of diaphragm wall are not significant. The thermally induced bending strain is mainly governed by the temperature differential and uneven thermal expansion/shrinkage across the wall.

关键词： thermo-active diaphragm wall     finite element analysis     thermo-hydro-mechanical coupling     ground source heat pump    

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Finite element analysis on the seismic behavior of side joint of Prefabricated Cage System in prefabricated

Yunlin LIU, Shitao ZHU

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1095-1104 doi: 10.1007/s11709-019-0538-2

摘要： The Prefabricated Cage System (PCS) has the advantages of high bearing capacity and good ductility. Meanwhile, it is convenient for factory production and it is beneficial to the cost savings, construction period shortening. Side joint is the weak region of PCS concrete frame and has great influence on seismic behavior of the whole structure. Thus systematically study on the seismic behavior of PCS concrete side joint is necessary. This paper presents a finite element study on behavior of the side joint under seismic loading. In the finite element model, PCS concrete and the reinforced concrete (RC) is modeled by the solid element and fiber-beam element, respectively. The numerical results is compared with the experimental results and it is found that the results of model based on fiber-beam element is in better agreement with the experimental results than solid element model. In addition, the overall seismic behavior of the side joints in PCS concrete is better than that of the RC with the same strength.

关键词： PCS concrete side joint     numerical simulation     fiber-beam element joint model     solid element joint model     seismic behavior    

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Finite element analysis of creep for plane steel frames in fire

Hui ZHU, Yuching WU

《结构与土木工程前沿（英文）》 2012年 第6卷 第3期   页码 297-307 doi: 10.1007/s11709-012-0162-x

摘要： Steel is widely used for the construction of bridges, buildings, towers, and other structures because of its great strength, light weight, ductility, and ease of fabrication, but the cost of fireproofing is a major disadvantage. Therefore, the resistance of a steel structure to fire is a significant subject for modern society. In the past, for simplification, creep behavior was not taken into account in research on the resistance of a steel structure to fire. However, it was demonstrated that the effect of creep is considerable at temperatures that commonly reach 600°C and should not be neglected in this context. In this paper, a co-rotational total Lagrangian finite element formulation is derived, and the corresponding numerical model is developed to study the creep behavior of plane steel frames in fire conditions. The geometric nonlinearity, material nonlinearity, high temperature creep, and temperature rate of change are taken into account. To verify the accuracy and efficiency of the numerical model, four prototypical numerical examples are analyzed using this model, and the results show very good agreement with the solutions in the literature. Next, the numerical model is used to analyze the creep behavior of the plane steel frames under decreasing temperatures. The results indicate that the effect of creep is negligible at temperatures lower than 500°C and is considerable at temperatures higher than 500°C. In addition, the heating rate is a critical factor in the failure point of the steel frames. Furthermore, it is demonstrated that the deflection at the midpoint of the steel beam, considering creep behavior, is approximately 13% larger than for the situation in which creep is ignored. At temperatures higher than 500°C, the deformed steel member may recover approximately 20% of the total deflection. The application of the numerical model proposed in this paper is greatly beneficial to the steel industry for creep analysis, and the numerical results make a significant contribution to the understanding of resistance and protection for steel structures against disastrous fires.

关键词： creep     plane steel frame     fire     finite element method     geometric nonlinearity    

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Spectral element modeling based structure piezoelectric impedance computation and damage identification

Zhigang GUO, Zhi SUN

《结构与土木工程前沿（英文）》 2011年 第5卷 第4期   页码 458-464 doi: 10.1007/s11709-011-0133-7

摘要： This paper presents a numerical simulation study on electromechanical impedance technique for structural damage identification. The basic principle of impedance based damage detection is structural impedance will vary with the occurrence and development of structural damage, which can be measured from electromechanical admittance curves acquired from PZT patches. Therefore, structure damage can be identified from the electromechanical admittance measurements. In this study, a model based method that can identify both location and severity of structural damage through the minimization of the deviations between structural impedance curves and numerically computed response is developed. The numerical model is set up using the spectral element method, which is promised to be of high numerical efficiency and computational accuracy in the high frequency range. An optimization procedure is then formulated to estimate the property change of structural elements from the electric admittance measurement of PZT patches. A case study on a pin-pin bar is conducted to investigate the feasibility of the proposed method. The results show that the presented method can accurately identify bar damage location and severity even when the measurements are polluted by 5% noise.

关键词： PZT     piezoelectric impedance     optimization     spectral element     damage identification    

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Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite element

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0035-5

摘要： Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and power cone programming

关键词： finite element power     stability rock escarpment    

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标题 作者 时间 类型 操作

Observation of black carbon aerosol in Beijing, 2003

LOU Shujuan, MAO Jietai, WANG Meihua

期刊论文

Effect of bond enhancement using carbon nanotubes on flexural behavior of RC beams strengthened with

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

Characteristics of chemical components in PM

Jianwu SHI,Xiang DING,Yue ZHOU,Ran YOU,Lu HUANG,Jiming HAO,Feng XIANG,Jian YANG,Ze SHI,Xinyu HAN,Ping NING

期刊论文

Acoustic analysis of lightweight auto-body based on finite element method and boundary element method

LIANG Xinhua, ZHU Ping, LIN Zhongqin, ZHANG Yan

期刊论文

Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

期刊论文

Special Column on Multiscale Stochastic Finite Element Method

期刊论文

Comparison of indirect boundary element and finite element methods A case study: Shiraz-Esfahan railway

Amin MANOUCHEHRIAN, Mohammad Fatehi MARJI, Mohsen MOHEBBI

期刊论文

Finite element analysis of controlled low strength materials

Vahid ALIZADEH

期刊论文

The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

期刊论文

Finite element modeling of thermo-active diaphragm walls

Yi RUI, Mei YIN

期刊论文

Finite element analysis on the seismic behavior of side joint of Prefabricated Cage System in prefabricated

Yunlin LIU, Shitao ZHU

期刊论文

Finite element analysis of creep for plane steel frames in fire

Hui ZHU, Yuching WU

期刊论文

Spectral element modeling based structure piezoelectric impedance computation and damage identification

Zhigang GUO, Zhi SUN

期刊论文

Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite element

期刊论文