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How to reduce the risk in the proving process for quality construction products 如何降低建筑产品质量验证过程中的风险
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2017-01-01 DOI: 10.5937/GRMK1701065C
Sonja Čerepnalkovska, Ljubica Vladiceska
Quality infrastructure with its components ensures compliance of products and services with the mandatory requirements, interests of consumers and businesses, and contributes to the maintaining of the quality of products and services. Quality infrastructure promotes export, competitiveness and innovation. Conformity assessment helps ensure certainty that products and services deliver on their promises. In other words, conformity assessment builds trust. This paper, which is based on the questionnaire, presents the real situation or the number of accredited laboratories in the Republic of Macedonia for testing in the field of construction as well as the participation in PT schemes, with an emphasis on the cement as a crucial product in the construction industry.
质量基础设施及其组成部分确保产品和服务符合强制性要求,符合消费者和企业的利益,并有助于保持产品和服务的质量。高质量的基础设施促进出口、竞争力和创新。合格评定有助于确保产品和服务履行其承诺。换句话说,合格评定建立信任。本文以问卷调查为基础,介绍了马其顿共和国在建筑领域进行测试的认可实验室的真实情况或数量,以及参与PT计划的情况,重点介绍了水泥作为建筑行业的关键产品。
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引用次数: 1
Fiber element formulation for inelastic frame analysis 非弹性框架分析的纤维单元公式
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/grmk1602003k
M. Kostic, B. Deretić-Stojanović
The paper discusses two formulations for the fiber based distributed plasticity beam/column element. For force based and displacement based formulations, basic details and main differences are emphasized. The differences in results of analysis when elements with these two formulations are used are demonstrated on two numerical examples. The first example involves the nonlinear static pushover analysis of low-rise frame with distributed element loading. The second example is nonlinear time history analysis of two-story frame subjected to earthquake loading. The differences in global and local response depending on the used finite element discretization are shown. In conclusion, the advantages of force based formulation and directions for the use of the two elements are summarized.
本文讨论了基于纤维的分布塑性梁柱单元的两种计算公式。对于基于力和基于位移的公式,强调基本细节和主要区别。通过两个数值算例,说明了采用这两种形式的单元分析结果的差异。第一个算例涉及分布单元荷载下低层框架的非线性静力推覆分析。第二个例子是地震荷载作用下两层框架的非线性时程分析。给出了不同的有限元离散方法在全局响应和局部响应上的差异。最后,总结了基于力的配方的优点和两种元素的使用方向。
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引用次数: 3
Analysis and modelling composite timber-concrete systems: Design of bridge structure according to EN 木结构-混凝土组合体系的分析与建模:依据EN标准的桥梁结构设计
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/GRMK1604047M
D. Manojlovic, Tatjana Kočetov-Mišulić
Timber-concrete composite structures are already applied more than 80 years in engineering practice, went trought the intuitive problem solution to the fully prefabricated hybride assemblies for dry building. The development path of timber-concrete composites was always followed by extensive theoretical and experimental research, whose results were successfully implemented in practice, i.e. on the market, but till presence didn't result in modern designer's code. In expectation of new European codes for timber-concrete composites, the objective of the paper is to provide a comprehensive review of available standards provisions and recent conclusions from literature. The key issues for practical design are highlighted and ilustrated on the example of glulam composite arch bridge structure with concrete deck, according the Eurocodes.
木混组合结构在工程实践中已经应用了80多年,从直观的问题解决到干式建筑的全预制混合组合结构。木结构-混凝土复合材料的发展道路一直遵循着广泛的理论和实验研究,其成果在实践中,即在市场上得到了成功的应用,但直到现在还没有形成现代设计规范。预计新的欧洲木材-混凝土复合材料规范,本文的目的是提供一个全面的审查现有的标准规定和最近的结论,从文献。并以欧洲规范中具有混凝土桥面的胶合木拱桥结构为例,说明了实际设计中应注意的关键问题。
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引用次数: 3
Environmental importance, composition and properties of pervious concrete 透水混凝土的环境重要性、组成和性能
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/GRMK1602015T
Gordana Topličić-Ćurčić, Dušan Grdić, Nenad Ristić, Zoran Grdić
Porous or pervious concrete was in use since the 60's of the previous century. It was first used in the USA and afterwards in Europe. The environmental importance of pervious concrete can be seen through fast collection of stormwater from the pavements, parking lots and other impervious surfaces. . Special purification systems remove the detrimental matter from the collected strormwater. As such, it can be used for other purposes. The pervious concrete has little or almost no fine aggregates. Its porosity is high, and ranges between 15 and 30 % in comparison to the concrete volume. Prior to massive usage of pervious concrete, it was necessary to prove, i.e. to examine its properties in service conditions. The paper elucidates the environmental character of pervious concrete, provides its usual composition and its properties.
自上世纪60年代以来,多孔或透水混凝土一直在使用。它首先在美国使用,后来在欧洲使用。从路面、停车场和其他不透水表面快速收集雨水可以看出透水混凝土的环境重要性。特殊的净化系统可以从收集的雨水中去除有害物质。因此,它可以用于其他目的。透水混凝土很少或几乎没有细集料。它的孔隙率很高,与混凝土体积相比在15%到30%之间。在大量使用透水混凝土之前,有必要证明,即检查其在使用条件下的性能。阐述了透水混凝土的环境特性,介绍了透水混凝土的常用组成及其性能。
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引用次数: 3
Hydration process and compressive strength of cement pastes containing natural zeolite 含天然沸石水泥浆体水化过程及抗压强度
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/GRMK1602029R
M. Radeka, T. Milović, M. Malešev, V. Radonjanin, M. Laban
This paper presents the results of the study examining the effect of natural zeolite from Igros, Serbia, on the hydration and compressive strength of Portland cement based pastes, in which a part of cement has been replaced by natural zeolite. The experimental part comprises three stages. In the first stage, the chemical composition of natural zeolite and the textural properties of both natural zeolite and Portland cement have been examined. In the second stage, Portland cement based pastes incorporating 0%, 10%, 20% and 30% per weight of natural zeolite have been prepared and cured for 28 and 60 days. Finally, mineralogical properties and compressive strength of pastes have been examined. The products of hydration and relative changes of portlandite consumption throughout hydration process (28 and 60 days) have been studied by the means of X-ray diffraction and Fourier transform infrared spectroscopy. Additionally, mercury intrusion porosimetry has been used to characterise pore structure.
本文介绍了塞尔维亚Igros天然沸石对硅酸盐水泥基浆体水化和抗压强度影响的研究结果,其中部分水泥已被天然沸石取代。实验部分包括三个阶段。在第一阶段,研究了天然沸石的化学成分以及天然沸石和硅酸盐水泥的结构特性。在第二阶段,制备天然沸石含量分别为0%、10%、20%和30%的硅酸盐水泥基浆体,分别固化28天和60天。最后,对膏体的矿物学性质和抗压强度进行了研究。利用x射线衍射和傅里叶变换红外光谱研究了水化过程中(28和60 d)硅酸盐水化产物和水化消耗的相对变化。此外,压汞孔隙度法已被用于表征孔隙结构。
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引用次数: 6
Nonlinear stability analysis of the frame structures 框架结构的非线性稳定性分析
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/GRMK1603027C
Ćorić Stanko, Brčić Stanko
In this paper the phenomenon of instability of frames in elasto-plastic domain was investigated. Numerical analysis was performed by the finite element method. Stiffness matrices were derived using the trigonometric shape functions related to exact solution of the differential equation of bending according to the second order theory. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. For the purposes of numerical investigation in this analysis, part of the computer program ALIN was created in a way that this program now can be used for elastic and elasto-plastic stability analysis of frame structures. This program is developed in the C++ programming language. Using this program, it is possible to calculate the critical load of frames in the elastic and inelastic domain. In this analysis, the algorithm for the calculation of buckling lengths of compressed columns of the frames was also established. The algorithm is based on the calculation of the global stability analysis of frame structures. Results obtained using this algorithm were compared with the approximate solutions from the European (EC3) and national (JUS) standards for the steel structures. By the given procedure in this paper it is possible to follow the behavior of the plane frames in plastic domain and to calculate the real critical load in that domain.
本文研究了框架的弹塑性失稳现象。采用有限元法进行了数值分析。根据二阶理论,利用与弯曲微分方程精确解相关的三角形状函数,导出了刚度矩阵。当结构在塑性域发生屈曲时,需要用切线模量Et代替弹性模量E。切线模量是应力相关函数,考虑了构件刚度在非弹性范围内的变化。为了在此分析中进行数值研究,计算机程序ALIN的一部分被创建,该程序现在可以用于框架结构的弹性和弹塑性稳定性分析。本程序是用c++编程语言开发的。利用该程序,可以计算框架在弹性和非弹性域的临界荷载。在此分析中,建立了框架受压柱屈曲长度的计算算法。该算法基于框架结构整体稳定性分析的计算。用该算法得到的结果与欧洲(EC3)和国家(JUS)钢结构标准的近似解进行了比较。通过本文给出的程序,可以跟踪平面框架在塑性域中的行为,并计算出该域中的实际临界荷载。
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引用次数: 4
The properties of the cement screeds with the addition of polypropylene fibres and the shrinkage-reducing admixture 研究了聚丙烯纤维和减缩掺合料对水泥砂浆性能的影响
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/grmk1601017R
Radan Radulovic, D. Jevtić, V. Radonjanin
The paper points out the problems of damage that can occur during the preparation and exploitation of a cement screed. There were described the types and properties and presented test results obtained on the samples of cement composites prepared with the addition of fibre reinforcement and shrinkage-reducing admixture. Testing procedure included the following properties: density, compressive strength, ultrasound, coefficient of construction advantages and shrinking, and above all the impact of compaction procedure on the quality of cement screed. The testing results of experimental research show that the use of polypropylene fibres and shrinkage-reducing admixture contributes to the improvement of mechanical and deformation properties of cement screeds and that installation which includes some method of vibration is crucial for screed quality. The above statements are also recommendations in the execution of cement screed in practice.
指出了水泥找平层在制备和开采过程中可能出现的损伤问题。介绍了掺加纤维增强和收缩掺合料的水泥复合材料的种类和性能,并给出了掺加纤维增强和收缩掺合料的水泥复合材料样品的试验结果。测试程序包括以下性能:密度、抗压强度、超声、施工优势系数和收缩系数,最重要的是压实程序对水泥层质量的影响。试验研究结果表明,聚丙烯纤维和减缩掺合料的使用有助于改善水泥砂浆的力学性能和变形性能,而包括某种振动方法的安装对水泥砂浆的质量至关重要。以上论述也是在水泥找平施工实践中提出的建议。
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引用次数: 1
Fracture toughness of ultra high performance concrete by flexural performance 超高性能混凝土受弯性能的断裂韧性
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2016-01-01 DOI: 10.5937/grmk1601003M
E. Manolova
This paper describes the fracture toughness of the innovative structural material - Ultra High Performance Concrete (UHPC), evaluated by flexural performance. For determination the material behaviour by static loading are used adapted standard test methods for flexural performance of fiber-reinforced concrete (ASTM C 1609 and ASTM C 1018). Fracture toughness is estimated by various deformation parameters derived from the load-deflection curve, obtained by testing simple supported beam under third-point loading, using servo-controlled testing system. This method is used to be estimated the contribution of the embedded fiber-reinforcement into improvement of the fractural behaviour of UHPC by changing the crack-resistant capacity, fracture toughness and energy absorption capacity with various mechanisms. The position of the first crack has been formulated based on P-δ (load- deflection) response and P-e (load - longitudinal deformation in the tensile zone) response, which are used for calculation of the two toughness indices I5 and I10. The combination of steel fibres with different dimensions leads to a composite, having at the same time increased crack resistance, first crack formation, ductility and post-peak residual strength.
本文介绍了创新结构材料-超高性能混凝土(UHPC)的断裂韧性,并通过弯曲性能进行了评价。通过静载荷测定材料性能采用纤维增强混凝土弯曲性能的标准试验方法(ASTM C 1609和ASTM C 1018)。断裂韧性是利用伺服控制测试系统对简支梁在三点载荷作用下的载荷-挠度曲线进行测试得到的各种变形参数来估计的。该方法通过多种机制改变了UHPC的抗裂能力、断裂韧性和吸能能力,从而评估了嵌入纤维增强材料对改善其断裂行为的贡献。根据P-δ(载荷-挠度)响应和P-e(载荷-拉伸区纵向变形)响应,确定了第一裂纹的位置,并将其用于计算两个韧性指标I5和I10。不同尺寸的钢纤维组合形成复合材料,同时具有更高的抗裂性、首次裂纹形成、延展性和峰后残余强度。
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引用次数: 0
Estimation of concrete compressive strength using artificial neural network 基于人工神经网络的混凝土抗压强度估计
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2015-01-01 DOI: 10.5937/GRMK1501003K
Srdjan Kostic, D. Vasović
In present paper, concrete compressive strength is evaluated using back propagation feed-forward artificial neural network. Training of neural network is performed using Levenberg-Marquardt learning algorithm for four architectures of artificial neural networks, one, three, eight and twelve nodes in a hidden layer in order to avoid the occurrence of overfitting. Training, validation and testing of neural network is conducted for 75 concrete samples with distinct w/c ratio and amount of superplasticizer of melamine type. These specimens were exposed to different number of freeze/thaw cycles and their compressive strength was determined after 7, 20 and 32 days. The obtained results indicate that neural network with one hidden layer and twelve hidden nodes gives reasonable prediction accuracy in comparison to experimental results (R=0.965, MSE=0.005). These results of the performed analysis are further confirmed by calculating the standard statistical errors: the chosen architecture of neural network shows the smallest value of mean absolute percentage error (MAPE=, variance absolute relative error (VARE) and median absolute error (MEDAE), and the highest value of variance accounted for (VAF).
本文采用反向传播前馈人工神经网络对混凝土抗压强度进行了评价。为了避免过拟合的发生,采用Levenberg-Marquardt学习算法对人工神经网络的1、3、8、12个隐层节点进行了四种结构的训练。对75个w/c比和三聚氰胺型高效减水剂掺量不同的混凝土试样进行了神经网络的训练、验证和测试。在不同的冻融循环次数下,分别在7、20和32天后测定试件的抗压强度。结果表明,与实验结果相比,1个隐藏层和12个隐藏节点的神经网络具有合理的预测精度(R=0.965, MSE=0.005)。通过计算标准统计误差进一步证实了这些分析结果:所选择的神经网络结构具有最小的平均绝对百分比误差(MAPE=)、方差绝对相对误差(VARE)和中位数绝对误差(MEDAE),以及最大的方差占比(VAF)。
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引用次数: 1
EVALUATION OF STRUCTURAL RELIABILITY USING SIMULATION METHODS 基于仿真方法的结构可靠性评估
IF 0.4 Q4 ENGINEERING, CIVIL Pub Date : 2015-01-01 DOI: 10.5937/GRMK1501017B
M. Baballëku, B. Isufi
Eurocode describes the 'index of reliability' as a measure of structural reliability, related to the 'probability of failure'. This paper is focused on the assessment of this index for a reinforced concrete bridge pier. It is rare to explicitly use reliability concepts for design of structures, but the problems of structural engineering are better known through them. Some of the main methods for the estimation of the probability of failure are the exact analytical integration, numerical integration, approximate analytical methods and simulation methods. Monte Carlo Simulation is used in this paper, because it offers a very good tool for the estimation of probability in multivariate functions. Complicated probability and statistics problems are solved through computer aided simulations of a large number of tests. The procedures of structural reliability assessment for the bridge pier and the comparison with the partial factor method of the Eurocodes have been demonstrated in this paper.
欧洲规范将“可靠性指数”描述为与“故障概率”相关的结构可靠性指标。本文以某钢筋混凝土桥墩为研究对象,对该指标进行了评价。在结构设计中明确地使用可靠度概念是很少见的,但通过它们我们可以更好地了解结构工程的问题。失效概率估计的主要方法有精确解析积分法、数值积分法、近似解析法和仿真法。本文采用蒙特卡罗模拟,因为它为多元函数的概率估计提供了一个很好的工具。复杂的概率和统计问题是通过计算机辅助模拟大量试验来解决的。本文阐述了桥墩结构可靠度评定的步骤,并与欧洲规范的部分因子法进行了比较。
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引用次数: 0
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Gradevnski Materijiali I Konstrukcije-Building Materials and Structures
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