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Review of the reinforcement sizing in the strength designof reinforced concrete slabs 钢筋混凝土板强度设计中配筋尺寸的研究进展
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-03-01 DOI: 10.12989/CAC.2021.27.3.211
L. Gil-Martín, E. Hernández-Montes
This paper presents a review of the two widespread approaches which deal with the ultimate strength design of RC slabs subjected to bending moments and torsion: The Field of Moments Method (FoMM) and the Sandwich method (SM). Special attention is paid to the ultimate strain distribution implicitly assumed when using each one of the methodologies, in particular, the yielding of the steel reinforcement. This work analyzes the initial assumption regarding ultimate strain distribution in the SM. Furthermore, this work studies the resisting moments field on which the Wood-Armer method is based, and it finds some inconsistencies. Several examples have been developed.
本文介绍了两种处理受弯矩和扭转作用的RC板极限强度设计的广泛方法:弯矩场法(formm)和夹层法(SM)。特别注意使用每种方法时隐含的极限应变分布,特别是钢筋的屈服。本文分析了SM中极限应变分布的初始假设。此外,本文还对Wood-Armer方法所依据的阻力矩场进行了研究,发现了一些不一致之处。已经开发了几个例子。
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引用次数: 3
Computer modeling to forecast accurate of efficiency parameters of different size of graphene platelet, carbon, and boron nitride nanotubes: A molecular dynamics simulation 预测不同尺寸石墨烯血小板、碳和氮化硼纳米管效率参数的计算机模型:分子动力学模拟
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.111
Ashkan Farazin, M. Mohammadimehr
In the present work, an extensive study for predicting efficiency parameters (ji) of various simulated nanocomposites including Polymethyl methacrylate (PMMA) as matrix and different structures including various sizes of graphene platelets (GPLs), single, double, and multi-walled carbon nanotubes (SWCNTs-DWCNTs-MWCNTs), and single and double-walled boron nitride nanotubes (SWBNNTs-DWBNNTs) are investigated. It should be stated that GPLs, carbon and boron nitride nanotubes (CNTs, BNNT) with different chiralities (5, 0), (5, 5), (10, 0), and (10, 10) as reinforcements are considered. In this research, molecular dynamics (MDs) method with Materials studio software is applied to examine the mechanical properties (Young's modulus) of simulated nanocomposite boxes and calculate i of each nanocomposite boxes. Then, it is noteworthy that by changing length (6.252, 10.584, and 21.173 nm) and width (7.137, 10.515, and 19.936) of GPLs, j1, j2, and j3 approximately becomes (0.101, 0.114, and 0.124), (1.15, 1.22, and 1.26), (1.04, 1.05, and 1.07) respectively. After that efficiency parameters of SWCNTs, DWCNTs, and MWCNTs are calculated and discussed separately. Finally efficiency parameters of SWBNNTs and DWBNNTs with different chiralities by PMMA as matrix are determined by MD and discussed separately. It is known that the accurate efficiency parameters helps a lot to calculate the properties of nanocomposite analytically. In particular, the obtained results from this research can be used for analytical work based on the extended rule of mixture (ERM) in bending, buckling and vibration analysis of structure in future study.
在本工作中,对各种模拟纳米复合材料的效率参数(ji)进行了广泛的研究,包括以聚甲基丙烯酸甲酯(PMMA)为基体,以及不同结构(包括不同尺寸的石墨烯片(GPLs)、单壁、双壁和多壁碳纳米管(SWCNTs-DWCNTs-MWCNTs)、单壁和双壁氮化硼纳米管(swbnnt - dwbnnt))的预测。需要说明的是,我们考虑了具有不同手性(5,0)、(5,5)、(10,0)和(10,10)的gpl、碳和氮化硼纳米管(CNTs, BNNT)作为增强剂。本研究采用分子动力学(MDs)方法和Materials studio软件对模拟纳米复合材料箱体的力学性能(杨氏模量)进行了检测,并计算了每个纳米复合材料箱体的力学性能。然后,值得注意的是,通过改变gpl的长度(6.252、10.584和21.173 nm)和宽度(7.137、10.515和19.936),j1、j2和j3分别近似为(0.101、0.114和0.124)、(1.15、1.22和1.26)、(1.04、1.05和1.07)。然后分别计算并讨论了SWCNTs、DWCNTs和MWCNTs的效率参数。最后,分别讨论了以聚甲基丙烯酸甲酯为基体的不同手性swbnnt和dwbnnt的效率参数。准确的效率参数有助于解析计算纳米复合材料的性能。特别是,本文的研究结果可用于今后基于扩展混合规则的结构弯曲、屈曲和振动分析工作。
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引用次数: 5
Finite element parametric study of RC beams strengthenedwith carbon nanotubes modified composites 碳纳米管改性复合材料加固RC梁的有限元参数研究
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.131
Mohammad R. Irshidat, Rami S. Alhusban
This paper aims at investigating the capability of different FRP/concrete interface models to predict the effect of carbon nanotubes on the flexural behavior of RC beams strengthened with CFRP. Three different interfacial bond models are proposed to simulate the adhesion between CFRP composites and concrete, namely: full bond, nonlinear spring element, and cohesive zone model. 3D Nonlinear finite element model is developed then validated using experimental work conducted by the authors in a previous investigation. Cohesive zone model (CZM) has the best agreement with the experimental results in terms of load-deflection response. CZM is the only bond model that accurately predicted the cracks patterns and failure mode of the strengthened RC beams. The FE model is then expanded to predict the effect of bond strength on the flexural capacity of RC beams strengthened with externally bonded CNTs modified CFRP composites using CZM bond model. The results reveal that the flexural capacity of the strengthened beams increases with increasing the bond strength value. However, only 23% and 22% of the CFRP stress and strain capacity; in the case of full bond; can be utilized before failure.
本文旨在研究不同FRP/混凝土界面模型预测碳纳米管对碳纤维增强混凝土梁抗弯性能影响的能力。提出了三种不同的界面粘结模型来模拟CFRP复合材料与混凝土之间的粘结,即:全粘结模型、非线性弹簧单元模型和粘结区模型。建立了三维非线性有限元模型,并利用作者在之前的研究中进行的实验工作进行了验证。黏聚区模型(CZM)在荷载-挠度响应方面与试验结果最吻合。CZM是唯一能准确预测钢筋混凝土加固梁裂缝形态和破坏模式的粘结模型。然后对有限元模型进行扩展,使用CZM粘结模型预测粘结强度对外粘结CNTs改性CFRP复合材料加固RC梁抗弯能力的影响。结果表明,加固梁的抗弯承载力随着粘结强度值的增大而增大。但CFRP的应力应变能力仅为23%和22%;在全额担保的情况下;可在故障前利用。
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引用次数: 1
Pozzolanicity identification in mortars by computationalanalysis of micrographs 用显微照片计算分析鉴定迫击炮的火山灰性
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.175
R. G. D. M. Filho, J. M. Rosso, E. Volnistem, R. Vanderlei, D. Longhi, Rodrigo Clemente Thom de Souza, P. R. Paraíso, L. M. D. M. Jorge
The incorporation of pozzolans to Portland cement pastes adds value in the development of new materials for the construction industry. This study presents a new computational method, complementary to the pozzolanic identification by compressive strength at 28 days method, for supporting the validation of pozzolanic mortars for non-structural purposes. An algorithm capable of classifying the pixels of micrographs of specimens fragments was developed. Therefore, comparative analyses were generated from fractional Gaussian representations in four intervals of the same amplitude that indicated the predispositions to form larger void indices (intervals 1 and 2). The results showed that the computational method indicators are in accordance with the physical and chemical indicators.
将火山灰掺入波特兰水泥浆中,为建筑行业开发新材料增加了价值。本研究提出了一种新的计算方法,补充了28天抗压强度法对火山灰的识别,为非结构用途的火山灰砂浆的验证提供了支持。提出了一种能够对标本碎片显微照片像素进行分类的算法。因此,在4个相同振幅的区间(区间1和区间2)中,通过分数阶高斯表示进行对比分析,表明易形成较大空隙指数。结果表明,计算方法指标与理化指标一致。
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引用次数: 0
Physical test and PFC2D simulation of the failure mechanismof echelon joint under uniaxial compression 单轴压缩下梯队节理破坏机制物理试验及PFC2D模拟
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.099
V. Sarfarazi, S. Abharian, E. Z. Ghalam
Experimental and discrete element methods were used to investigate the effects of echelon non-persistent joint on the failure behaviour of joint's bridge area under uniaxial compressive test. Concrete samples with dimension of 150 mmx100 mmx50 mm were prepared. Uniaxial compressive strength and tensile strength of concrete were 14 MPa and 1MPa, respectivly. Within the specimen, three echelon non-persistent notches were provided. These joints were distributed on the three diagonal plane. the angle of diagonal plane related to horizontal axis were 15o, 30o and 45o. The angle of joints related to diagonal plane were 30o, 45o, 60o. Totally, 9 different configuration systems were prepared for non-persistent joint. In these configurations, the length of joints were taken as 2 cm. Similar to those for joints configuration systems in the experimental tests, 9 models with different echelon non-persistent joint were prepared in numerical model. The axial load was applied to the model by rate of 0.05 mm/min. the results show that the failure process was mostly governed by both of the non-persistent joint angle and diagonal plane angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. The strength of samples increase by increasing both of the joint angle and diagonal plane angle. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.
采用实验和离散元方法研究了单轴压缩试验条件下梯队非持久节理对节理桥面破坏行为的影响。制备尺寸为150mmx100mmx50mm的混凝土试样。混凝土单轴抗压强度为14 MPa,抗拉强度为1MPa。在标本内,提供了三个梯队的非持久缺口。这些关节分布在三个对角线面上。对角线平面与横轴的夹角分别为150度、300度和45度。与对角线平面相关的关节角度分别为300度、45度、600度。针对非持续性关节,共制备了9种不同的构型系统。在这些构型中,关节长度取2 cm。与试验试验中关节构型系统相似,在数值模型中制备了9种不同梯次非持久关节模型。轴向载荷以0.05 mm/min的速率作用于模型。结果表明:破坏过程主要受非持久节理角和对角线平面角共同控制;试件的抗压强度与结构面断裂模式和破坏机制有关。结果表明,结构面剪切性能与节理角增大所诱发的拉伸裂纹数量有关。增大节理角和对角角均可提高试样的强度。试验测试和数值模拟两种方法的破坏形态和破坏强度相似。
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引用次数: 10
Vibration analysis of steel fiber reinforced self-compacting concrete beam on elastic foundation 弹性基础上钢纤维增强自密实混凝土梁的振动分析
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.085
M. Ozdemir, V. Kobya, M. Yaylı, A. Mardani‐Aghabaglou
In this study, the effect of steel fiber utilization, boundary conditions, different beam cross-section, and length parameter are investigated on the free vibration behavior of fiber reinforced self-compacting concrete beam on elastic foundation. In the analysis of the beam model recommended by Euler-Bernoulli, a method utilizing Stokes transformations and Fourier Sine series were used. For this purpose, in addition to the control beam containing no fiber, three SCC beam elements were prepared by utilization of steel fiber as 0.6% by volume. The time-dependent fresh properties and some mechanical properties of self-compacting concrete mixtures were investigated. In the modelled beam, four different beam specimens produced with 0.6% by volume of steel fiber reinforced and pure (containing no fiber) SCC were analyzed depending on different boundary conditions, different beam cross-sections, and lengths. For this aim, the effect of elasticity of the foundation, cross-sectional dimensions, beam length, boundary conditions, and steel fiber on natural frequency and frequency parameters were investigated. As a result, it was observed that there is a noticeable effect of fiber reinforcement on the dynamic behavior of the modelled beam.
研究了钢纤维用量、边界条件、不同梁截面和长度参数对弹性基础上纤维增强自密实混凝土梁自由振动性能的影响。在欧拉-伯努利推荐的梁模型分析中,采用了Stokes变换和傅立叶正弦级数相结合的方法。为此,除不含纤维的控制梁外,采用体积比为0.6%的钢纤维制备了3个SCC梁单元。研究了自密实混凝土混合料随时间变化的新鲜性能和部分力学性能。在模拟梁中,根据不同的边界条件、不同的梁截面和长度,分析了四种不同的梁试件,钢纤维增强和纯(不含纤维)SCC的体积为0.6%。为此,研究了基础弹性、截面尺寸、梁长、边界条件和钢纤维对固有频率和频率参数的影响。结果表明,纤维增强对模型梁的动力性能有明显的影响。
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引用次数: 0
Research on the anti-seismic performance of composite precast utility tunnels based on the shaking table test and simulation analysis 基于振动台试验和模拟分析的组合预制隧道抗震性能研究
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.163
Yanmin Yang, Zi-li Li, Yongqing Li, Ran Xu, Yunke Wang
In this paper, the parameters of haunch height, reinforcement ratio and site condition were evaluated for the influence on the seismic performance of a composite precast fabricated utility tunnel by shaking table test and numerical simulation. The dynamic response laws of acceleration, interlayer displacement and steel strain under unidirectional horizontal seismic excitation were analyzed through four specimens with a similarity ratio of 1:6 in the test. And a numerical model was established and analyzed by the finite element software ABAQUS based on the structure of utility tunnel. The results indicated that composite precast fabricated utility tunnel with the good anti-seismic performance. In a certain range, increasing the height of haunch or the ratio of reinforcement could reduce the influence of seismic wave on the utility tunnel structure, which was beneficial to the structure earthquake resistance. The clay field containing the interlayer of liquefied sandy soil has a certain damping effect on the structure of the utility tunnel, and the displacement response could be reduced by 14.1%. Under the excitation of strong earthquake, the reinforcement strain at the side wall upper end and haunches of the utility tunnel was the biggest, which is the key part of the structure. The experimental results were in good agreement with the fitting results, and the results could provide a reference value for the anti-seismic design and application of composite precast fabricated utility tunnel.
通过振动台试验和数值模拟,评价了腿高、配筋率、场地条件等参数对组合预制综合隧道抗震性能的影响。通过4个相似比为1:6的试件,分析了单向水平地震激励下加速度、层间位移和钢应变的动力响应规律。利用有限元软件ABAQUS建立了针对某电站隧道结构的数值模型,并对其进行了分析。结果表明,复合预制装配式公用隧道具有良好的抗震性能。在一定范围内,提高后腿高度或配筋率可以减小地震波对公用隧道结构的影响,有利于提高结构的抗震性能。含液化砂质土夹层的粘土场对水工隧道结构有一定的阻尼作用,可使水工隧道的位移响应降低14.1%。在强震作用下,综合隧道侧壁上端及后拱处的钢筋应变最大,是结构的关键部位。试验结果与拟合结果吻合较好,可为组合预制隧道的抗震设计和应用提供参考价值。
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引用次数: 2
Implementation of double scalar elastic damage constitutive model in UMAT interface UMAT界面双标量弹性损伤本构模型的实现
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.153
Pan Liu, B. Shen
This paper aims to simulate the isotropic elastic damage theory of Liu Jun (2012) using the self-programmed UMAT subroutine in the interface of ABAQUS. Liu Jun (2012)'s method based on the mechanic theory can not be used interactively with the currently commonly used finite element software ABAQUS. The advantage of this method in the paper is that it can interact with ABAQUS and provide a constitutive program framework that can be modified according to user need. The model retains the two scalar damage variables and the corresponding two energy dissipation mechanisms and damage criteria for considering the tensile and compressive asymmetry of concrete. Taking C45 concrete as an example, the relevant damage evolution parameters of its tensile and compressive constitutive model are given. The study demonstrates that the uniaxial tensile stress calculated by the subroutine is almost the same as the Chinese Concrete Design Specification (GB50010) before the peak stress, but ends soon after the peak stress. The stress-strain curve of uniaxial compression calculated by the subroutine is in good agreement with the peak stress in Chinese Concrete Design Specification (GB50010), but there is a certain deviation in the descending stage. In addition, this paper uses the newly compiled subroutine to simulate the shear bearing capacity of the shear key in a new structural system, namely the open-web sandwich slab. The results show that the damage constitutive subroutine has certain reliability.
本文旨在利用ABAQUS界面中自编的UMAT子程序对刘军(2012)的各向同性弹性损伤理论进行模拟。刘军(2012)基于力学理论的方法不能与目前常用的有限元软件ABAQUS交互使用。该方法的优点是可以与ABAQUS进行交互,并提供一个可根据用户需要修改的本构程序框架。该模型保留了两个标量损伤变量以及相应的两种能量耗散机制和损伤准则,以考虑混凝土的拉压不对称性。以C45混凝土为例,给出了其拉伸和压缩本构模型的相关损伤演化参数。研究表明,子程序计算的单轴拉应力在峰值应力之前与中国混凝土设计规范(GB50010)基本相同,但在峰值应力之后很快结束。该子程序计算的单轴压缩应力-应变曲线与中国混凝土设计规范(GB50010)中的峰值应力吻合较好,但在下降阶段存在一定偏差。此外,本文还利用新编写的子程序对一种新型结构体系即开腹板夹层板的剪力键抗剪承载力进行了模拟。结果表明,该损伤本构子程序具有一定的可靠性。
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引用次数: 1
New explicit formulas for optimum design of concrete gravity dams 混凝土重力坝优化设计的新显式公式
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-02-01 DOI: 10.12989/CAC.2021.27.2.143
A. Habibi, S. Zarei, N. Khaledy
Large dams are a part of the infrastructure of any society, and a huge amount of resources are consumed to build them. Among the various types of dams, the optimum design of concrete gravity dams requires special attention because these types of dams require a huge amount of concrete for their construction. On the other hand, concrete gravity dams are among the structures whose design, regarding the acting forces, geometric parameters, and resistance and stability criteria, has some complexities. In the present study, an optimization methodology is proposed based on Sequential Quadratic Programming (SQP), and a computer program is developed to perform optimization of concrete gravity dams. The optimum results for 45 concrete gravity dams are studied and regression analyses are performed to obtain some explicit formulas for optimization of the gravity dams. The optimization of concrete gravity dams can be provided easily using the developed formulas, without the need to perform any more optimization process.
大型水坝是任何社会基础设施的一部分,建造水坝需要消耗大量资源。在各种类型的水坝中,混凝土重力坝的优化设计需要特别注意,因为这类水坝需要大量的混凝土来建造。另一方面,混凝土重力坝是其设计在作用力、几何参数、阻力和稳定性准则方面具有一定复杂性的结构之一。本文提出了一种基于顺序二次规划(SQP)的优化方法,并开发了混凝土重力坝优化的计算机程序。对45座混凝土重力坝的优化结果进行了研究,并进行了回归分析,得到了一些明确的重力坝优化计算公式。利用所建立的公式,可以方便地对混凝土重力坝进行优化,而无需再进行任何优化过程。
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引用次数: 0
Strengthening of isolated square footings using passive wrapping systems 使用被动包裹系统加强孤立的方脚
IF 4.1 4区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/CAC.2021.27.1.041
Xin-Zheng Lu, R. Aboutaha
This paper introduced three new strengthening systems for isolated footings: BFRP wrapping system, CFRP wrapping system, and steel jacketing system. The proposed systems are more practical than the current traditional methods, which involves installing many dowel bars and splicing reinforcing steels to join new and old concrete segments. In the proposed three new systems, BFRP wraps, CFRP wraps, or steel jackets are installed on the exterior surface of the enlarged footing, with construction adhesive or a few steel dowels being applied to the contact surfaces. To investigate the effectiveness of three systems, forty-four models were constructed in ABAQUS, with different parameters being considered. All footings investigated failed in punching shear, including original and retrofitted footings. According to FEA results and parametric studies, the three strengthening systems were capable of improving the punching shear resistance of footings. By introducing a new factor n, the punching shear equation in Eurocode 2 was modified to predict the punching shear resistances of the strengthened footings. A linear formula was developed to present the relationship between the new factor n and the investigated parameters.
介绍了三种新型隔震基础加固体系:BFRP包覆体系、CFRP包覆体系和钢护套体系。所提出的系统比目前的传统方法更实用,传统方法需要安装许多销钉和拼接钢筋来连接新旧混凝土段。在提出的三种新系统中,在扩大基础的外表面安装BFRP包层,CFRP包层或钢护套,并在接触面应用施工胶或一些钢销钉。为了考察这三个系统的有效性,在ABAQUS中构建了44个模型,考虑了不同的参数。所有被调查的基础都在冲剪中失效,包括原始基础和改造基础。有限元分析结果和参数分析表明,三种加固体系均能提高基础的抗冲剪能力。通过引入新的因子n,对欧洲规范2中的冲剪方程进行修正,以预测加固基础的冲剪抗力。建立了一个线性公式来表示新因子n与所研究参数之间的关系。
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引用次数: 1
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Computers and Concrete
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