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An enhanced damage plasticity model for predicting the cyclic behavior of plain concrete under multiaxial

Mohammad Reza AZADI KAKAVAND, Ertugrul TACIROGLU

《结构与土木工程前沿（英文）》 2020年第14卷第6期页码 1531-1544 doi: 10.1007/s11709-020-0675-7

摘要： Some of the current concrete damage plasticity models in the literature employ a single damage variable for both the tension and compression regimes, while a few more advanced models employ two damage variables. Models with a single variable have an inherent difficulty in accounting for the damage accrued due to tensile and compressive actions in appropriately different manners, and their mutual dependencies. In the current models that adopt two damage variables, the independence of these damage variables during cyclic loading results in the failure to capture the effects of tensile damage on the compressive behavior of concrete and vice-versa. This study presents a cyclic model established by extending an existing monotonic constitutive model. The model describes the cyclic behavior of concrete under multiaxial loading conditions and considers the influence of tensile/compressive damage on the compressive/tensile response. The proposed model, dubbed the enhanced concrete damage plasticity model (ECDPM), is an extension of an existing model that combines the theories of classical plasticity and continuum damage mechanics. Unlike most prior studies on models in the same category, the performance of the proposed ECDPM is evaluated using experimental data on concrete specimens at the material level obtained under cyclic multiaxial loading conditions including uniaxial tension and confined compression. The performance of the model is observed to be satisfactory. Furthermore, the superiority of ECDPM over three previously proposed constitutive models is demonstrated through comparisons with the results of a uniaxial tension-compression test and a virtual test.

关键词： damage plasticity model plain concrete cyclic loading multiaxial loading conditions

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Ballistic behavior of plain and reinforced concrete slabs under high velocity impact

Chahmi OUCIF, Luthfi Muhammad MAULUDIN, Farid Abed

《结构与土木工程前沿（英文）》 2020年第14卷第2期页码 299-310 doi: 10.1007/s11709-019-0588-5

摘要： This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete slabs. In this paper, we focus on the comparison of the performance of the plain and reinforced concrete slabs of unconfined compressive strength 41 MPa under ballistic impact. The concrete slab has dimensions of 675 mm × 675 mm × 200 mm, and is meshed with 8-node hexahedron solid elements in the impact and outer zones. The ogive-nosed projectile is considered as rigid element that has a mass of 0.386 kg and a length of 152 mm. The applied velocities vary between 540 and 731 m/s. 6 mm of steel reinforcement bars were used in the reinforced concrete slabs. The constitutive material modeling of the concrete and steel reinforcement bars was performed using the Johnson-Holmquist-2 damage and the Johnson-Cook plasticity material models, respectively. The analysis was conducted using the commercial finite element package Abaqus/Explicit. Damage diameters and residual velocities obtained by the numerical model were compared with the experimental results and effect of steel reinforcement and projectile diameter were studies. The validation showed good agreement between the numerical and experimental results. The added steel reinforcements to the concrete samples were found efficient in terms of ballistic resistance comparing to the plain concrete sample.

关键词： Johnson-Holmquist-2 Johnson-Cook reinforced concrete damage impact loads

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Investigation on the freeze-thaw damage to the jointed plain concrete pavement under different climate

Shuaicheng GUO, Qingli DAI, Jacob HILLER

《结构与土木工程前沿（英文）》 2018年第12卷第2期页码 227-238 doi: 10.1007/s11709-017-0426-6

摘要： Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses under different climate conditions. Based on the Long-Term Pavement Performance (LTPP) data base, the freeze-thaw damage generated by four different kinds of climate conditions are considered in this project: wet-freeze, wet-non freeze, dry-freeze and dry-non freeze. The amount of the transverse crack and the joint spalling, along with the International Roughness Index ( ) are compared among the test sections located in these four different climate conditions. The back calculation with the Falling Weight Deflectometer (FWD) test results based on the ERES and the Estimation of Concrete Pavement Parameters (ECOPP) methods are conducted to obtain concrete slab elastic modulus and the subgrade -value. These two parameters both decrease with service time under freeze condition. Finally, MEPDG simulation is conducted to simulate the development with service year. These results showed the reasonable freeze-thaw damage development with pavement service life and under different climate conditions.

关键词： LTPP elastic modulus k-value IRI MEPDG

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Effect of size on biaxial flexural strength for cement-based materials by using a triangular plate method

Hakan T TURKER

《结构与土木工程前沿（英文）》 2022年第16卷第8期页码 1017-1028 doi: 10.1007/s11709-022-0871-8

摘要： The effect of size on the biaxial flexural strength (BFS) of Portland cement mortar was investigated by using the recently proposed triangular plate method (TPM). An experimental program was conceived to study the size effect by keeping a constant water-cement ratio of 0.485, cement-sand ratio of 1:2.75, and using unreinforced triangular mortar plates of five different thicknesses and seven different side lengths. The BFS of the produced specimens was tested, and variations of BFS depending on specimen thickness and side length were determined. The results indicated that increases in triangular plate specimen side length and specimen thickness led to a decrease in the BFS of Portland cement mortar. The effect of specimen length increase on BFS was more significant than on the effect of the specimen thickness. The variations in specimens’ thickness indicated a deterministic Type I size effect, while the variations in specimens’ length showed an energetic-statistical Type I size effect.

关键词： testing apparatus & methods plain concrete tensile properties biaxial flexural strength triangular plate method

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Finite element modeling of environmental effects on rigid pavement deformation

Sunghwan KIM,Halil CEYLAN,Kasthurirangan GOPALAKRISHNAN

《结构与土木工程前沿（英文）》 2014年第8卷第2期页码 101-114 doi: 10.1007/s11709-014-0254-x

摘要： In this study, finite element (FE)-based primary pavement response models are employed for investigating the early-age deformation characteristics of jointed plain concrete pavements (JPCP) under environmental effects. The FE-based ISLAB (two-and-one-half-dimensional) and EverFE (three-dimensional) software were used to conduct the response analysis. Sensitivity analyses of input parameters used in ISLAB and EverFE were conducted based on field and laboratory test data collected from instrumented pavements on highway US-34 near Burlington, Iowa. Based on the combination of input parameters and equivalent temperatures established from preliminary studies, FE analyses were performed and compared with the field measurements. Comparisons between field measured and computed deformations showed that both FE programs could produce reasonably accurate estimates of actual slab deformations due to environmental effects using the equivalent temperature difference concept.

关键词： jointed plain concrete pavements (JPCP) curling and warping sensitivity analyses rigid pavement analysis and design finite element analysis (FEA)

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GROUNDWATER DEPLETION IN THE NORTH CHINA PLAIN: THE AGROHYDROLOGICAL PERSPECTIVE

《农业科学与工程前沿（英文）》 2021年第8卷第4期页码 594-598 doi: 10.15302/J-FASE -2021407

摘要：

Agricultural production in the North China Plain with rainfall of less than 500 mm·yr⁻¹ has been steadily increasing over the past 40 years, with the groundwater levels decreasing at a rate of over 1 m·yr⁻¹. In this paper, it is demonstrated theoretically that the water level in the aquifer can be expressed as a function of agricultural production and the sum of water added as rainfall and imported from outside the basin. Therefore, the most effective measures to halt groundwater depletion are importing water, decreasing cropping intensity and growing less thirsty crops. Irrigation improvements, mulching and agronomic measures that could increase the yield per unit area have less of an impact on solving the declining groundwater levels.

关键词： crop yield / groundwater depletion / sustainability

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Evaluation of groundwater quality in the Xinjiang Plain Area

Jinlong ZHOU, Xinguang DONG, Yiping WANG, Guomin LI, Xiaojing GUO,

《环境科学与工程前沿（英文）》 2010年第4卷第2期页码 183-186 doi: 10.1007/s11783-010-0021-8

摘要： Groundwater is the main source of drinking water for the urban and rural residents in the plain area of the Xinjiang Uygur Autonomous Region, China. The quality of groundwater has a direct relationship with human health. Thus, 386 groundwater samples collected from April to August in 2003 were analyzed. The samples were collected in basic evaluation units which are determined on the basis of watersheds. Total dissolved solids, total hardness, pH value, NH–N, CHOH, Chemiluminescence detection of permanganate index (COD) and intestinal germ group were evaluated according to the guidelines of Groundwater Quality Standard (GB/T14848-93). The quality of the groundwater in each evaluation unit was classified by using the One Veto Method (a unified approach stipulated by the Ministry of Water Resources). The results indicate that the groundwater in the mainstream area of the Tarim Basin and the Yerqiang River Sub-basin belongs to Category V; the groundwater in the Wulungu River Sub-basin, the Kaidu-Kongque River Sub-basin, the Kashgar River Sub-basin, the Cherchen River Sub-basin and the Hotan River Sub-basin belongs to Category IV; the groundwater in the Aibi Lake System belongs to Category II, and the groundwater of other evaluation units belongs to Category III. The causes of water quality formation were concisely analyzed. The results can be useful for the evaluation and management of water resources in the Xinjiang Plain Area.

关键词： groundwater quality evaluation one veto method total dissolved solids (TDS) pH total hardness

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Quantitative analysis of yield and soil water balance for summer maize on the piedmont of the North China Plain

Jingjing WANG,Feng HUANG,Baoguo LI

《农业科学与工程前沿（英文）》 2015年第2卷第4期页码 295-310 doi: 10.15302/J-FASE-2015074

摘要： The North China Plain (NCP) is a major grain production area in China, but the current winter wheat-summer maize system has resulted in a large water deficit. This water-shortage necessitates the improvement of crop water productivity in the NCP. A crop water model, AquaCrop, was adopted to investigate yield and water productivity (WP) for rain-fed summer maize on the piedmont of the NCP. The data sets to calibrate and validate the model were obtained from a 3-year (2011–2013) field experiment conducted on the Yanshan piedmont of the NCP. The range of root mean square error (RMSE) between the simulated and measured biomass was 0.67–1.25 t·hm , and that of relative error (RE) was 9.4%–15.4%, the coefficient of determination ( ) ranged from 0.992 to 0.994. The RMSE between the simulated and measured soil water storage at depth of 0–100 cm ranged from 4.09 to 4.39 mm; and RE and in the range of 1.07%–1.20% and 0.880–0.997, respectively. The WP as measured by crop yield per unit evapotranspiration was 2.50–2.66 kg·m . The simulated impact of long-term climate (i.e., 1980–2010) and groundwater depth on crop yield and WP revealed that the higher yield and WP could be obtained in dry years in areas with capillary recharge from groundwater, and much lower values elsewhere. The simulation also suggested that supplementary irrigation in areas without capillary groundwater would not result in groundwater over-tapping since the precipitation can meet the water required by both maize and ecosystem, thus a beneficial outcome for both food and ecosystem security can be assured.

关键词： AquaCrop summer maize soil water balance water productivity

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Improving water use efficiency in grain production of winter wheat and summer maize in the North China Plain

Xiying ZHANG,Wenli QIN,Juanna XIE

《农业科学与工程前沿（英文）》 2016年第3卷第1期页码 25-33 doi: 10.15302/J-FASE-2016090

摘要： Reducing irrigation water use by improving water use efficiency (WUE) in grain production is critical for the development of sustainable agriculture in the North China Plain (NCP). This article summarizes the research progresses in WUE improvement carried out at the Luancheng station located in the Northern part of NCP for the past three decades. Progresses in four aspects of yield and WUE improvement are presented, including yield and WUE improvement associated with cultivar selection, irrigation management for improving yield and WUE under limited water supply, managing root system for efficient soil water use and reducing soil evaporation by straw mulch. The results showed that annual average increase of 0.014 kg·m for winter wheat and 0.02 kg·m in WUE were observed for the past three decades, and this increase was largely associated with the improvement in harvest index related to cultivar renewal and an increase in chemical fertilizer use and soil fertility. The results also indicated that deficit irrigation for winter wheat could significantly reduce the irrigation water use, whereas the seasonal yield showed a smaller reduction rate and WUE was significantly improved. Straw mulching of summer maize using the straw from winter wheat could reduce seasonal soil evaporation by 30–40 mm. With new cultivars and improved management practices it was possible to further increase grain production without much increase in water use. Future strategies to further improve WUE are also discussed.

关键词： harvest index cultivar selection deficit irrigation root water uptake straw mulching

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compaction parameters for sand-filled embankment using large thickness sand filling technique in Jianghan Plain

Wentao WANG, Chongzhi TU, Rong LUO

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 568-576 doi: 10.1007/s11709-017-0444-4

摘要： The study uses the finite element method to simulate a new technique of highway sand embankment filling in Jianghan Plain district, which can raise the thickness of sand-filled layer from 30 cm to 70 cm and can significantly shorten the construction period based on the guarantee of sand embankment construction quality. After simulating the three compacting proposals carried out on the field test, the study uses COMSOL software to research on the compacting effects of sand-filled layers in larger thicknesses by 22 ton vibratory roller alone, and then to investigate the steady compacting effect of 12 ton vibratory roller. The simulation results indicate that the sand-filled layer thickness of 70 cm is suitable for the new sand filling technique, and the sand-filled embankment project with tight construction period is suggested to choose the 12 ton vibration roller for steady compaction.

关键词： sand embankment compaction in large thickness numerical simulation small size vibratory roller steady compaction

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黄淮海平原浅层地下水中NO₃-N含量的空间变异与分布特征

李保国,白由路,胡克林,黄元仿,陈德立

《中国工程科学》 2001年第3卷第4期页码 42-45

摘要：

通过GPS定位取样分析和GIS处理，研究了黄淮海平原浅层地下水中NO₃-N含量的空间变异和分布特征。结果表明，黄淮海平原浅层地下水中NO₃-N含量在35～50km的取样密度下，没有半方差结构，各取样点之间变异性较大；黄淮海平原有10%的面积浅层地下水中NO₃-N含量超过20 mg·L^-1，主要分布在天津至济南一线和淮河流域的新蔡、阜阳和蚌埠一带。徐州至连云港一带的苏北地区及山东的潍坊地区，浅层地下水中的NO₃-N含量一般在10～20 mg·L^-1之间，约占黄淮海平原总面积的11.5%。浅层地下水中NO₃-N 的含量与地下水埋深密切相关，NO₃-N含量超过20 mg·L^-1的地下水埋深一般在3 m以上，地下水埋深在10 m以下时，其中的NO₃-N含量均不超过10mg·L^-1。这表明，目前通过土壤NO₃-N的淋失对该区地下水中 NO₃-N含量影响深度一般不超过10 m。此项研究结果对于黄淮海平原持续发展，制定优化的高效水肥管理措施和方案有一定指导意义。

关键词：黄淮海平原地下水 NO₃-N 空间分布

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现代建模与优化技术研究——在三江平原井灌水稻节水灌溉系统中的应用

付强

《中国工程科学》 2002年第4卷第6期页码 44-55

摘要：

将SPAC模型理论变相宏观应用于三江平原井灌水稻节水灌溉系统中，将地下水、农用机井、晒水池、渠道、本田池、环境因子等纳入整体系统，在各个子系统中综合运用现代建模与优化技术，通过有关机理与理论研究，建立相关的数学模型。对地下水、晒水池、渠道及水稻水分生产函数、水稻需水量、有效降雨等6个子系统进行建模与分析，制定了非充分灌溉条件下优化灌溉制度。最后通过典型示范小区的优化设计，将节水技术组装，实现了增温5～15℃，节水171%，增产700～1000 kg/hm²的目标。

关键词：建模优化三江平原井灌水稻节水灌溉系统

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平原河网区水动力重构理论与实践 Article

唐洪武, 袁赛瑜, 曹昊

《工程（英文）》 2023年第24卷第5期页码 202-212 doi: 10.1016/j.eng.2022.01.015

摘要：

我国平原河网地区地势低洼，河道比降平缓，水动力弱，加上密集的人类活动，水安全问题十分突出，比如洪涝频发、水体自净能力差、水生态系统脆弱等。本文研究发现这些问题都与水动力有关，水流能量时空分布失衡是产生这些水问题的共同本源。由此，创建了平原河网区水动力重构理论。该理论在水量调控的基础上，深挖水动力及有限能量在水生态环境改善中的作用，优化布局水闸、泵站等水利工程体系，充分挖潜工程的综合效益。通过重构水动力时空分布来满足平原河网区复杂水问题统筹治理的需求。在此基础上，建立了完整的弱动力平原河网区多尺度水动力重构、多目标水力调控的理论方法和技术体系，提出了平原河网区水问题统筹治理原则。最后以扬州主城区河网活水提质为例，介绍该理论的实际应用及效果。

关键词：平原河网水安全问题水动力重构多目标统筹治理

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太湖流域平原水网区面源污染现状与控制对策

秦忠,耿清蔚,臧贵敏

《中国工程科学》 2010年第12卷第6期页码 113-116

摘要：

通过对2005年与2000年入河污染物总量的分析表明，点源在入河污染物总量中的占比逐年下降，面源的占比迅速增加，尤其是TP（总磷）入河量已经超过点源；面源污染呈“总量持平，结构调整”态势；面源污染物总量构成中，农村居民生活位居第一，其次是水产养殖、水田径流等。在面源污染成因分析基础上，相应提出了太湖流域平原水网区面源污染控制的对策建议。

关键词：太湖流域平原水网面源污染控制

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Improvement of impact resistance of plain-woven composite by embedding superelastic shape memory alloy

Xiaojun GU, Xiuzhong SU, Jun WANG, Yingjie XU, Jihong ZHU, Weihong ZHANG

《机械工程前沿（英文）》 2020年第15卷第4期页码 547-557 doi: 10.1007/s11465-020-0595-1

摘要： Carbon fiber reinforced polymer (CFRP) composites have excellent mechanical properties, specifically, high specific stiffness and strength. However, most CFRP composites exhibit poor impact resistance. To overcome this limitation, this study presents a new plain-woven CFRP composite embedded with superelastic shape memory alloy (SMA) wires. Composite specimens are fabricated using the vacuum-assisted resin injection method. Drop-weight impact tests are conducted on composite specimens with and without SMA wires to evaluate the improvement of impact resistance. The material models of the CFRP composite and superelastic SMA wire are introduced and implemented into a finite element (FE) software by the explicit user-defined material subroutine. FE simulations of the drop-weight impact tests are performed to reveal the superelastic deformation and debonding failure of the SMA inserts. Improvement of the energy absorption capacity and toughness of the SMA-CFRP composite is confirmed by the comparison results.

关键词： carbon fiber reinforced polymer composite shape memory alloy wire impact resistance drop-weight test finite element simulation