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A numerical and computer simulation for dynamic stability analysis of 3-unknown graded porous nanoplates using a Chebyshev-Ritz-Bolotin method 采用Chebyshev-Ritz-Bolotin方法对3-未知梯度多孔纳米板的动态稳定性进行了数值模拟和计算机模拟
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.78.4.379
D. Wei
A numerical and computer simulation for dynamic stability analysis of graded porous nanoplates has been provided using a Chebyshev-Ritz-Bolotin approach. The nanoplate has been formulated according to the nonlocal elasticity and a 3-unkown plate model capturing neutral surface location. All of material properties are assumed to be dependent of porosity factor which determines the amount or volume of pores. The nano-size plate has also been assumed to be under temperature and moisture variation. It will be shown that stability boundaries of the nanoplate are dependent on static and dynamical load factors, porosity factor, temperature variation and nonlocal parameter.
采用Chebyshev-Ritz-Bolotin方法对梯度多孔纳米板的动态稳定性进行了数值模拟和计算机模拟。根据非局部弹性和捕获中性表面位置的3-未知板模型,制备了纳米板。假定材料的所有性能都取决于孔隙率因子,孔隙率因子决定了孔隙的数量或体积。在温度和湿度变化的条件下,也假设了纳米板。结果表明,纳米板的稳定性边界取决于静、动载荷因素、孔隙率因素、温度变化和非局部参数。
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引用次数: 1
Shear strength evaluation of RC solid piers of high-speed railway bridges in China 中国高速铁路桥梁RC实体墩抗剪强度评价
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.78.4.413
W. Guo, Chao-Chin Fan, Yao Cui, Chen Zeng, Li-zhong Jiang, Zhi-wu Yu
Piers are the main lateral force-resisting members of high-speed railway (HSR) bridges used in China and are characterized by low axial load ratios, low longitudinal reinforcement ratios, low stirrup ratios, and high shear span ratios. It is well known that flexural, flexural-shear, and shear failures of piers may occur during an earthquake. In this study, a new shear strength model was developed to simulate the seismic failure of HSR solid piers accurately. First, low cyclic-loading test data of solid piers obtained in recent years were collected to set up a database for model verification. Second, based on the test database, the applicability of existing shear strength models was evaluated. Finally, a new shear strength model for HSR solid piers with round-ended cross-sections was derived based on the truss model and ultimate equilibrium theory. In comparison with existing models, it was demonstrated that the proposed model could be used to predict the shear strength of HSR piers more accurately.
桥墩是国内高速铁路桥梁的主要抗侧力构件,具有低轴载比、低纵向配筋比、低配箍比和高剪跨比的特点。众所周知,在地震中桥墩可能发生弯曲破坏、弯剪破坏和剪切破坏。本文建立了一种新的抗剪强度模型,以准确模拟高铁实心桥墩的地震破坏。首先,收集近年来获得的实体桥墩低循环荷载试验数据,建立模型验证数据库;其次,基于试验数据库,对现有抗剪强度模型的适用性进行了评价。最后,基于桁架模型和极限平衡理论,建立了圆端截面高铁实心桥墩抗剪强度模型。通过与已有模型的比较,表明本文提出的模型能够更准确地预测高铁桥墩的抗剪强度。
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引用次数: 1
Simulation of different carbon structures on significant mechanical and physical properties based on MDs method 基于MDs方法模拟不同碳结构的重要力学和物理性能
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.78.6.691
Ashkan Farazin, M. Mohammadimehr, Amirabbas Ghorbanpour-Arani
In this research, the nanocomposite boxes are simulated using polyurethane (PU) as a thermoplastic polymer with various reinforcements including carbon nanoparticles (CNPs), graphene platelets (GPLs), single-walled carbon nanotubes (SWCNTs), and double-walled carbon nanotubes (DWCNTs), which are as biocompatible and biodegradable. To predict the mechanical and physical properties of each nanocomposite boxes, the molecular dynamics (MDs) method with Materials studio software has been applied. Ultimately, all properties including mechanical and physical properties (Young's modulus, shear modulus, bulk modulus and Poisson's ratio of nanocomposite from CNPs to DWCNTs approximately becomes 5.7, 10.25, 28.63, 96 and 1.39 times, respectively. Then, the stiffness matrix are obtained by Materials studio software. Moreover, the obtained results from this research are validated with the results of the literature. Also, the mechanical and physical properties of nanocomposite are recommended before fabrication. The manufacturing of this nanocomposite is used for biomedical cases such as artificial vessels and piping.
在本研究中,采用聚氨酯(PU)作为热塑性聚合物,并添加各种增强剂,包括碳纳米颗粒(CNPs)、石墨烯片(GPLs)、单壁碳纳米管(SWCNTs)和双壁碳纳米管(DWCNTs),模拟了纳米复合材料箱,这些增强剂具有生物相容性和可生物降解性。为了预测每个纳米复合材料盒子的力学和物理性能,应用了Materials studio软件中的分子动力学(MDs)方法。最终,CNPs / DWCNTs纳米复合材料的力学和物理性能(杨氏模量、剪切模量、体积模量和泊松比)分别约为5.7倍、10.25倍、28.63倍、96倍和1.39倍。然后,通过Materials studio软件得到刚度矩阵。并且,本研究得到的结果与文献的结果进行了验证。同时,介绍了制备前纳米复合材料的力学和物理性能。这种纳米复合材料的制造用于生物医学领域,如人造血管和管道。
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引用次数: 1
Free vibration analysis of functionally graded plates containing embedded curved cracks 含嵌曲裂纹功能梯度板的自由振动分析
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.79.2.157
V. Khalafi, J. Fazilati
In the present paper, the free vibration behavior of functionally graded plates containing straight and curved embedded crack is investigated. A NURBS-based multi-patch isogeometric analysis formulation is utilized based on the firstorder shear deformation plate theory. The Nitsche technique is implemented to meet the inter-patch connection constraints. The crack line is assumed as a narrow cut along a straight or free-shape curve path within the plate. The crack growth phenomena are overlooked. The accuracy and quality of the obtained results are compared to those available in the literature. Subsequently, the effect of various material and geometry parameters on the free vibration characteristics of cracked FG plate including the volume-fraction index, crack shape, crack length, crack orientation and, crack location are examined. It learned that the straight crack inclination angle mainly influences the fifth and fourth natural modes. Moreover, the FGM mixture index doesn't noticeably affect the frequency trends. No considerable impact is noted between the edge constraint setups on the fundamental frequency.
本文研究了含直、弯嵌缝功能梯度板的自由振动特性。基于一级剪切变形板理论,提出了一种基于nurbs的多块等几何分析公式。采用Nitsche技术来满足贴片间连接约束。假定裂纹线是沿板内直线或自由形状曲线路径的窄切口。裂纹扩展现象被忽略。所得结果的准确性和质量与文献中可用的结果进行了比较。随后,研究了各种材料和几何参数对裂纹FG板自由振动特性的影响,包括体积分数指数、裂纹形状、裂纹长度、裂纹方向和裂纹位置。研究发现,直裂纹倾角主要影响第五、四阶自然模态。此外,女性生殖器切割混合指数对频率趋势没有显著影响。边缘约束设置对基频没有显著的影响。
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引用次数: 2
Seismic fracture analysis of concrete arch dams incorporating the loading rate dependent size effect of concrete 考虑混凝土尺寸效应的混凝土拱坝地震断裂分析
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.79.2.169
Amir Pirooznia, A. Moradloo
The purpose of this study is to investigate the size effect, loading rate, and smeared crack models in the nonlinear seismic behavior of concrete arch dams. One of the important parameters in the design of arch concrete dams is the tensile strength of unreinforced mass concrete. Various fracture parameters obtained from experimental results reported for concrete in order to study the size-effect is used in this paper. In the present analysis, the smeared crack method is used in finite element analysis of the Morrow Point arch dam subjected to three components of the TAFT earthquake as a case study. The dependence of fracture, and especially of the size effect, on the loading rate is described. Models incorporating nonlinear analysis in three cases with and without the size effect of dam concrete and fluid-structure interaction are employed to evaluate and compare them. The water is taken as an inviscid, compressible fluid, and the foundation is rigid. From the study, it is concluded that the participation of the size effect leads to higher values of maximum displacements and stresses in benchmark points compared to the model that ignores the size effect. The crack initiation criterion based on the maximum tensile stress according to the size effect of concrete, and also the dynamic loading range should be defined. Results show considering fixed smeared crack models used in the concrete specimen as well as the size effect of concrete materials, will lead to the crack profile is more realistic and will represent near to real behavior of concrete fracture. The results are of significant interest for the concrete fracture of dams; hence the loading rate should be adopted for fracture properties obtained in dams.
本研究的目的是探讨混凝土拱坝非线性地震行为中的尺寸效应、加载率和涂抹裂缝模型。无筋大体积混凝土的抗拉强度是拱坝设计的重要参数之一。为了研究混凝土的尺寸效应,本文采用了从已有的试验结果中得到的各种断裂参数。本文以TAFT地震三分量作用下的莫罗点拱坝为例,采用涂抹裂缝法进行有限元分析。描述了断裂,特别是尺寸效应对加载速率的依赖关系。采用具有和不具有坝混凝土尺寸效应和流固耦合作用的三种情况下的非线性分析模型对它们进行评价和比较。水被认为是一种无粘性、可压缩的流体,地基是刚性的。研究表明,与不考虑尺寸效应的模型相比,尺寸效应的参与导致基准点的最大位移和应力值更高。应根据混凝土的尺寸效应确定以最大拉应力为起裂准则,并确定动加载范围。结果表明,考虑混凝土试件中使用的固定涂抹裂缝模型以及混凝土材料的尺寸效应,可以使裂缝剖面更加真实,更接近于混凝土断裂的真实行为。研究结果对大坝混凝土断裂具有重要意义;因此,大坝的断裂特性应采用加载率。
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引用次数: 2
Numerical simulation on the crack initiation and propagation of coal with combined defects 含复合缺陷煤裂纹萌生与扩展的数值模拟
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.79.2.237
Huayong Lv, Zhanbo Cheng, Yaqing Dong, Jing Zhang, Y. Ma
There is normally the occurrence of pre-existing cracks and holes in coal mass to influence its mechanical behaviours. And the crack initiation and propagation around the tip of pre-existing cracks can be observed to induce the overall failure of coal mass finally. In this study, two groups of hole with the radius of 10 mm connecting one crack with length and width of 20 mm and 1 mm, respectively, were pre-existed in sample to explore the influence of crack angle (from 0 to 90o) on the unconfined compressive strength (UCS), crack initiation and propagation, and failure modes of coal mass with combined faults by using RFPA2D. The results showed that the stress-strain curves of specimen with double-hole-crack exhibit multiple stress drop compared to that of intact coal sample, especially in the post-peak stage. Moreover, UCS decreased firstly with the crack angle increasing to 30o and then increased until the crack angle reaching to 75o following by decreasing with the continuous increase of crack angle to 90o. In addition, the failure mode of double-hole-crack specimen with the crack angle of 0-30o can be regards as the dominated tensile failure combined with shear failure, which was consist with the failure pattern of intact specimen. On the other hand, the failure mode of double-hole-crack specimen with the crack angle of 45-90o is the dominated shear failure combined with tensile failure. Meanwhile, the distribution characteristics of acoustic emission energy can be used to better reflect the deformation and failure process of coal mass with combined defects.
煤体中通常存在预先存在的裂隙和孔洞,从而影响其力学行为。观察到裂纹在裂隙尖端处的萌生和扩展,最终导致煤体整体破坏。本研究在试样中预先存在两组半径为10 mm的孔洞,分别连接一条长度为20 mm、宽度为1 mm的裂缝,利用RFPA2D研究裂隙角度(0 ~ 90°)对含组合断层煤体无侧限抗压强度(UCS)、裂缝起裂扩展及破坏模式的影响。结果表明:与完整煤样相比,双孔裂纹试样的应力-应变曲线表现出多次应力降,尤其是在峰后阶段;随着裂纹角度的增加,单轴抗压强度先减小后增大,直至裂纹角度为75°,随着裂纹角度的持续增大至90°,单轴抗压强度逐渐减小。双孔裂纹试件在0 ~ 300角范围内的破坏模式可视为以拉伸破坏为主,剪切破坏为主,与完整试件的破坏模式一致。另一方面,裂隙角度为45 ~ 90°的双孔裂纹试样的破坏模式为剪切破坏为主,拉伸破坏为主。同时,利用声发射能量的分布特征可以更好地反映含组合缺陷煤体的变形破坏过程。
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引用次数: 7
Solving structural optimization problems with discrete variables using interactive fuzzy search algorithm 用交互式模糊搜索算法求解离散变量结构优化问题
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.79.2.247
A. Mortazavi
The current investigation deals with assessing the search performance of a recently developed, parameter-free, and self-adaptive search algorithm so-called Interactive Fuzzy Search Algorithm (IFSA) in solving weight minimization of the constrained structural optimization problems with discrete variables. The proposed IFSA combines the navigation pattern of the Interactive Search Algorithm (ISA) with the decision-making competence of fuzzy reasoning. The fuzzy module of the proposed IFSA permanently monitors the search process and adjusts each agent's search behavior by considering the governing condition of the current problem. In structural optimization, due to construction limitations, it is more realistic to select the sizing variables from a discrete domain. Thus, in this study, to empirically evaluate the search capability of the IFSA, it is applied to solve a suite of structural optimization problems with the discrete design variables. The attained outcomes are compared with the ISA and some other related methods addressed in the relevant literature. The acquired accuracy level and demanded number of objective function evaluations indicates that the IFSA, comparatively, using lower computational cost could found lighter structural systems. Also, the comparison of the attained standard deviation values shows that the IFSA demonstrates higher stability during the optimization process. These superior outcomes designate that the fuzzy decision-making mechanism of the IFSA could work properly in dynamically adapting the search behavior of the algorithm with the governing condition of the current problem. Consequently, the promising gained results reveal that IFSA can effectively be applied in solving the structural optimization problems with discrete search domains.
当前的研究涉及评估一种最近开发的,无参数的,自适应的搜索算法,即交互式模糊搜索算法(IFSA)在解决具有离散变量的约束结构优化问题的权值最小化中的搜索性能。该算法将交互式搜索算法(ISA)的导航模式与模糊推理的决策能力相结合。该算法的模糊模块对搜索过程进行永久监控,并根据当前问题的控制条件调整各agent的搜索行为。在结构优化中,由于结构的限制,从离散域中选取尺度变量更为现实。因此,在本研究中,为了实证评估IFSA的搜索能力,将其应用于解决一套具有离散设计变量的结构优化问题。所获得的结果与ISA和相关文献中提到的一些其他相关方法进行了比较。所得的精度水平和所需的目标函数评价次数表明,相对而言,IFSA可以用更低的计算成本找到更轻的结构体系。得到的标准差值的比较表明,IFSA在优化过程中具有较高的稳定性。这些优越的结果表明,IFSA的模糊决策机制能够根据当前问题的控制条件动态调整算法的搜索行为。结果表明,IFSA可以有效地应用于求解具有离散搜索域的结构优化问题。
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引用次数: 3
Output-only structural damage detection under multipleunknown white noise excitations 多未知白噪声激励下的纯输出结构损伤检测
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.79.3.327
P. Ni, Xiaojuan Wang, Hongyuan Zhou
Most of the existing output-only damage detection methods require the number of sensors should be larger than the number of unknown excitation force, and the force location should be available. This paper presents a novel output-only damage detection method without these requirements. The proposed method is based on the correlation function of acceleration responses. When the structure is under white noise excitations (or ambient excitations), the correlation function of acceleration responses can be treated as free vibration responses with unknown initial conditions. The unknown structural parameters and initial conditions can be simultaneously identified by minimizing the difference between the measured and calculated correlation functions. The unknown initial conditions are identified with state space method and the unknown structural parameters are updated with sensitivity method. Numerical studies of a 2D truss and a five-bay 3D frame structure are conducted to demonstrate the accuracy, effectiveness, and robustness of the proposed method. Experimental studies on an eight-floor steel frame are further carried out. Results show that the proposed method is not only insensitive to environmental noise but also applicable when the number of sensors is less than that of unknown excitations. Also, the proposed method can be used for damage detection when the force location is unknown.
现有的大多数仅输出的损伤检测方法要求传感器数量大于未知激励力的数量,并且力的位置是可用的。本文提出了一种新的不需要这些要求的仅输出的损伤检测方法。该方法基于加速度响应的相关函数。当结构在白噪声激励(或环境激励)下,加速度响应的相关函数可以看作是初始条件未知的自由振动响应。通过最小化测量值与计算值之间的差值,可以同时识别未知的结构参数和初始条件。用状态空间法辨识未知初始条件,用灵敏度法更新未知结构参数。通过二维桁架和五孔三维框架结构的数值研究,验证了该方法的准确性、有效性和鲁棒性。对一个八层钢框架进行了进一步的试验研究。结果表明,该方法不仅对环境噪声不敏感,而且适用于传感器数量小于未知激励的情况。该方法也可用于力位置未知时的损伤检测。
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引用次数: 4
Influence of sisal fibres and rubber latex on the engineering properties of sand concrete 剑麻纤维和胶乳对砂混凝土工程性能的影响
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.80.1.047
Oday Z. Jaradat, Karima Gadri, B. Tayeh, Abdelhamid Guettalaa
This experimental study aims to investigate the properties of sand concrete (SC) by using sisal fibres and latex in various fields in construction. Sisal fibres were applied at four ratios of 0.05%, 0.10%, 0.15% and 0.20%, while liquid latex was replaced with three ratios of 15%, 25% and 35%. In this context, ideal percentages of sisal fibre (0.1% F) and latex (35% L) were combined in a single cement matrix. For each percentage, tests on flow, density, compressive strength, flexural strength, ultrasonic pulse velocity, modulus of elasticity, water accessible porosity, water absorption and shrinkage were performed on fresh and hardened SC. Scanning electron microscopy (SEM) was also conducted for microstructure analysis. Results indicate that adding latex emulsion to SC containing sisal fibres increased the adhesion of the fibres to the cement matrix, which contributed to the increase in flexural strength and the decrease in shrinkage. This condition also helped reduce the porosity and water absorption of latex-modified SC with sisal fibres compared with SC that contained fibres. The improvement occurred in the properties that constitute an obstacle to the widespread use of SC. Thus this improvement has practical implications.
本实验研究旨在探讨剑麻纤维和乳胶在不同建筑领域的砂混凝土性能。剑麻纤维以0.05%、0.10%、0.15%和0.20%的比例涂抹,液体乳胶以15%、25%和35%的比例涂抹。在这种情况下,理想百分比的剑麻纤维(0.1% F)和乳胶(35% L)结合在一个单一的水泥基体中。在每个百分比下,分别对新鲜和硬化的SC进行了流量、密度、抗压强度、抗折强度、超声脉冲速度、弹性模量、可水孔隙率、吸水率和收缩率测试,并进行了扫描电子显微镜(SEM)的微观结构分析。结果表明:在含剑麻纤维的SC中加入乳胶乳液,增强了纤维与水泥基体的附着力,从而提高了纤维的抗弯强度,降低了收缩率。与含有纤维的纤维相比,这种条件也有助于降低含有剑麻纤维的乳胶改性纤维的孔隙率和吸水率。这种改进发生在构成SC广泛使用障碍的特性上。因此,这种改进具有实际意义。
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引用次数: 11
Optimization of porosity distribution of FGP beams considering buckling strength 考虑屈曲强度的FGP梁孔隙率分布优化
IF 2.2 4区 工程技术 Q2 Engineering Pub Date : 2021-01-01 DOI: 10.12989/SEM.2021.79.6.711
M. Farrokh, Mohammad Taheripur
In this paper, the porosity distribution of functionally graded porous (FGP) beams are optimized using the genetic algorithm to achieve the maximum ratio of the normalized buckling load to the beam's weight. The analytical forms for critical buckling loads of the FGP beams under different end conditions are determined analytically using principle virtual work based on the Euler and Timoshenko beam theories. The effects of Nano Graphene Platelets (NGPs) on the critical buckling load of the nanocomposite FGP beams are also taken into account. The sensitivity analyses show that porosity will reduce the buckling load-to-weight ratio of porous beams to conventional beams in some cases. Based on the optimization results, the optimum distribution of the porosity and NGPs' volume fraction are proposed for several porosity coefficients. The obtained results indicate that the optimum distribution for porosity has a symmetric sandwich-like shape while the optimum distribution for NGPs' volume fraction is uniform.
本文采用遗传算法对功能梯度多孔(FGP)梁的孔隙率分布进行了优化,以实现归一化屈曲载荷与梁重的最大比值。利用基于欧拉和Timoshenko梁理论的虚功原理,解析确定了FGP梁在不同端部条件下的临界屈曲载荷解析形式。研究了纳米石墨烯薄片对纳米复合材料FGP梁临界屈曲载荷的影响。敏感性分析表明,在某些情况下,孔隙率会降低多孔梁的屈曲载荷重量比。根据优化结果,提出了几种孔隙度系数下孔隙度和NGPs体积分数的最佳分布。结果表明:孔隙率的最佳分布为对称的三明治状,而NGPs体积分数的最佳分布为均匀的。
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引用次数: 2
期刊
Structural Engineering and Mechanics
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