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SEISMIC RESPONSE ANALYSES OF RC PORTAL FRAMES WITH LARGE DEFORMABLE ELASTIC BRACES 大变形弹性支撑混凝土门式刚架地震反应分析
Pub Date : 2017-11-04 DOI: 10.2495/CMEM-V6-N5-880-886
K. Sawada
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引用次数: 1
ADVANCES IN SEISMIC VULNERABILITY ASSESSMENT OF REINFORCED CONCRETE BUILDINGS APPLIEDTO THE EXPERIENCE OF LORCA (SPAIN) 2011EARTHQUAKE 2011年西班牙洛尔卡地震经验中钢筋混凝土建筑地震易损性评价的研究进展
Pub Date : 2017-11-04 DOI: 10.2495/CMEM-V6-N5-887-898
J. Ródenas, A. Tomás, S. García-Ayllón
Despite the technical advances in seismic structural design, many regions still present a high level of seismic risk, principally due to the high vulnerability of their buildings. A modification of the empirical method for assessing the seismic vulnerability of reinforced concrete buildings in urban areas is proposed in this contribution. In the RISK-UE LM1 framework, the values of certain behaviour modifiers related to the typological, structural and urban parameters of the buildings have been modified according to a review and analysis of the currently available models and an evaluation of the actual seismic performance of buildings. This provides continuity to the progress of the previous works published to date. The proposal has been applied to the city of Lorca, Spain, for which ample knowledge of the damage occurred in the earthquake of May 11, 2011 is available. Less dispersion between actual observed and estimated damage in buildings is presented in comparison with the previous studies, with a statistical significance of 5%, thus achieving a more accurate evaluation of seismic risk. The new model also provides valuable information to be used in the planning and management of post-earthquake emergency situations when combining with GIS techniques, thus allowing for a better definition of several damage scenarios to enhance the development and urban preparedness in case of further seismic events.
尽管抗震结构设计的技术进步,许多地区仍然存在高水平的地震风险,主要是由于其建筑物的高度脆弱性。本文提出了对城市地区钢筋混凝土建筑物地震易损性评估的经验方法的改进。在RISK-UE LM1框架中,根据对当前可用模型的审查和分析以及对建筑物实际抗震性能的评估,已经修改了与建筑物的类型、结构和城市参数相关的某些行为调节剂的值。这为迄今为止出版的先前作品的进展提供了连续性。这一建议已被应用于西班牙洛尔卡市,该市对2011年5月11日地震造成的破坏有充分的了解。与以往的研究相比,实际观测到的建筑物损伤与估算的建筑物损伤之间的差异较小,统计显著性为5%,从而实现了更准确的地震风险评估。新模型还提供了宝贵的信息,可与地理信息系统技术相结合,用于震后紧急情况的规划和管理,从而可以更好地定义几种破坏情况,以加强发展和城市对未来地震事件的准备工作。
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引用次数: 5
EFFECTS OF MODELLING PARAMETERS ON THE SEISMIC ANALYSIS OF BRIDGES 模型参数对桥梁抗震分析的影响
Pub Date : 2017-11-04 DOI: 10.2495/CMEM-V6-N5-868-879
Yuling Gao, Lan Lin
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引用次数: 4
PREDICTING MODULUS OF ELASTICITY OF RECYCLED AGGREGATE CONCRETE USING NONLINEAR MATHEMATICAL MODELS 利用非线性数学模型预测再生骨料混凝土的弹性模量
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-703-715
Junior A. Reyes-sánchez, A. Tenza-Abril, F. Verdú, J. A. R. Perales
This research was financed by the University of Alicante through projects VIGROB-256 and GRE13-03.
本研究由阿利坎特大学资助,项目vig罗布-256和GRE13-03。
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引用次数: 7
VISUALISATION OF ACOUSTIC STREAMING USING PIV IN NEWTONIAN AND NON-NEWTONIAN LIQUIDS 在牛顿和非牛顿液体中使用piv可视化声流
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-814-826
M. Amaratunga, R. W. Time
The effect of fluid rheology on acoustic streaming was studied experimentally using a low frequency (600Hz–15kHz) underwater acoustic transducer. The fluid rheology was compared with deionized water and non-Newtonian fluid polyanionic cellulose (PAC). Streaming effect generated by the trans- ducer in a static liquid medium was visualized by particle image velocimetry (PIV) method. The motion of fluid was optically visualized using light scattering ‘seeding’ particles. Velocity profiles induced by the acoustic streaming have different shapes and range of magnitudes. First, the acoustic stream- ing in deionized water was visualized for different frequencies and pressure amplitudes (voltages). A maximum of 1 g/L PAC was then introduced in smaller steps for some selected frequency and voltage settings. The streaming disappeared completely when the total concentration of the fluid medium reached 0.19 g/L PAC. The measured streaming velocities are found to be in the range of 2.1 to 9.9 cm/s for water and it is proportional to the applied voltage and the operating frequency of the transducer. When introducing PAC, the streaming velocity within water gradually decreased until zero due to the attenuation of acoustic waves by viscous effects. This confirms that the streaming velocity is approximately inversely proportional to the bulk viscosity of the medium. The velocity vectors and the streaming velocity maps illustrate the induced non-linearities of the fluid medium due to the acoustic propagation. The results are part of a comprehensive study aimed at investigating the influence of acoustic vibration on particle settling in non-Newtonian
利用低频(600Hz-15kHz)水声换能器实验研究了流体流变对声流的影响。并与去离子水和非牛顿流体聚阴离子纤维素(PAC)进行了流变学比较。采用粒子图像测速(PIV)方法对传感器在静态液体介质中产生的流场效应进行了可视化研究。利用光散射“播种”粒子对流体的运动进行光学可视化。声流引起的速度分布具有不同的形状和震级范围。首先,可视化了不同频率和压力幅值(电压)下去离子水中的声流。然后,在一些选定的频率和电压设置下,以较小的步骤引入最大1g /L PAC。当流体介质的总浓度达到0.19 g/L PAC时,流体流动完全消失。测量到的流体流动速度在2.1 ~ 9.9 cm/s之间,与外加电压和换能器的工作频率成正比。引入PAC后,由于声波受粘滞效应衰减,水流速度逐渐减小,直至为零。这证实了流动速度与介质的总体粘度近似成反比。速度矢量和流速度图反映了声波传播引起的流体介质非线性。这些结果是一项综合研究的一部分,旨在研究声振动对非牛顿介质中粒子沉降的影响
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引用次数: 0
Finite element simulation of spherical indentation experiments 球形压痕实验的有限元模拟
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-749-763
S. Syngellakis, H. Habbab, B. Mellor
The problem of indentation of ductile materials by ball indenters is, in this paper, addressed by numerical modelling. A finite element model is built using general purpose software. The axisymmetry of the problem is taken into account thus reducing its dimensionality. Particular attention is given to contact modelling as well as mesh design for optimal performance. The model is validated by comparing its predictions to the exact elastic solution as well as experimental measurements from elasto-plastic indentation tests. In the latter case, indenter imperfection is accounted for and material input are stress-strain curves originating from tensile tests. The sensitivity of numerical results to indenter elasticity is investigated. The effect of friction and specimen creep during indentation on load-displacement predictions is also assessed.
本文采用数值模拟的方法研究了球压头对延性材料的压痕问题。利用通用软件建立了有限元模型。考虑了问题的轴对称性,降低了问题的维数。特别注意的是接触建模以及网格设计的最佳性能。通过将模型的预测结果与精确的弹性解以及弹塑性压痕试验的实验测量结果进行比较,验证了模型的有效性。在后一种情况下,压头缺陷被考虑在内,材料输入是源于拉伸试验的应力-应变曲线。研究了数值结果对压头弹性的敏感性。在压痕过程中,摩擦和试样蠕变对荷载-位移预测的影响也进行了评估。
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引用次数: 9
COMPUTATIONAL APPROACH TO IMPROVE BEARINGS BY RESIDUAL STRESSES BASED ON THEIR REQUIRED BEARING FATIGUE LIFE 基于轴承疲劳寿命要求的残余应力改进轴承的计算方法
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-656-666
F. Pape, O. Maiss, B. Denkena, G. Poll
In drive systems and component technology a high reliability is very important for machines. Machine element dimensions are calculated for reliability. The properties for these elements are based on conventional manufacturing techniques. Very high stresses are applied on bearings in their operating time. To improve the endurance life, residual stresses can be induced into the subsurface zone. In contrast to a conventional grinding process, the mechanical surface modification process deep rolling is able to induce very high compressive residual stresses. A computational approach was developed to establish an appropriate residual stress depth profile matching the applied loads. Thus, the costs of manufacturing can be chosen in accordance to the required properties. The method to determine the residual stresses is based on an iterative reverse calculation of an existing bearing fatigue life model of Ioannides et al. The model originates from the approach of Lundberg and Palmgren (1947) including a stress fatigue limit tu. For the term ti, the fatigue criterion of Dang-Van is applied. The equation accounts for the maximum orthogonal shear stress and the local hydrostatic pressure phyd, corrected for residual and hoop stress. The inputs into the computational model are the stresses on the surface, which are simulated based on the load and geometry of the contact between roller and bearing surface. As an output the required residual stress profile underneath the bearings raceway is given to achieve a bearing fatigue life as required for the given application. In order to verify the model, the bearing fatigue life was experimentally determined for a given residual stress profile by experiments.
在驱动系统和部件技术中,高可靠性对机器是非常重要的。为了可靠性,计算了机器元件的尺寸。这些元素的性质是基于传统的制造技术。轴承在运行过程中承受着很高的应力。为了提高耐久寿命,可以将残余应力诱导到地下区域。与传统的磨削工艺相比,机械表面改性深滚加工能够产生非常高的压残余应力。建立了一种计算方法,以建立一个适当的残余应力深度分布与施加的载荷。因此,制造成本可以根据所需的性能来选择。确定残余应力的方法是基于Ioannides等人已有的轴承疲劳寿命模型的迭代反算。该模型源自Lundberg和Palmgren(1947)的方法,包括应力疲劳极限tu,其中ti项采用Dang-Van疲劳判据。该方程考虑了最大正交剪应力和局部静水压力,并对残余应力和环向应力进行了修正。计算模型的输入是表面上的应力,这是基于载荷和滚子与轴承表面之间接触的几何形状来模拟的。作为输出,给出了轴承滚道下方所需的残余应力剖面,以达到给定应用所需的轴承疲劳寿命。为了验证该模型,通过实验确定了给定残余应力剖面下轴承的疲劳寿命。
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引用次数: 1
AN ELASTIC-VISCO-PLASTIC DEFORMATION MODEL OF AL–LI WITH APPLICATION TO FORGING 铝锂的弹粘塑性变形模型及其在锻件中的应用
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-635-646
L. Borkowski, J. Sharon, A. Staroselsky
Recent alloy developments have produced a new generation of Al–Li alloys that provide not only weight savings, but also many property benefits such as excellent corrosion resistance, good spectrum fatigue crack growth performance, a good strength and toughness combination and compatibility with standard manufacturing techniques. The forging of such alloys would lead to mechanical properties that closely match the aircraft engine requirements including lower weight, improved performance and a longer life. As a result, detailed analyses need to be performed to determine which material properties are best suited for a specific structure and how to achieve the required mechanical and damage tolerant properties during material processing. We developed an integrated physics-based model for prediction of microstructure evolution and material property prediction of third-generation Al–Li alloys. In order to develop such a model, an elastic-plastic crystal plasticity model is developed and incorporated in finite element software (ANSYS). The model accounts for microstructural evolution during non-isothermal, non-homogeneous deformation and is coupled with the damage kinetics. Our model bridges the gap between dislocation dynamics and continuum mechanics scales. Model parameters have been calibrated against lab tests including micropillar in-situ simple compression tests of Al–Li alloy 2070. Numerical predictions are verified against the lab results including stress–strain curves and crystallographic texture evolution.
最近的合金发展已经产生了新一代的铝锂合金,不仅可以减轻重量,而且还具有许多性能优势,例如优异的耐腐蚀性,良好的频谱疲劳裂纹扩展性能,良好的强度和韧性组合以及与标准制造技术的兼容性。这种合金的锻造将使其机械性能与飞机发动机的要求紧密匹配,包括更轻的重量、更好的性能和更长的寿命。因此,需要进行详细的分析,以确定哪种材料性能最适合特定的结构,以及如何在材料加工过程中实现所需的机械和损伤容忍性能。建立了第三代铝锂合金微观组织演变和材料性能预测的综合物理模型。为了建立该模型,建立了弹塑性晶体塑性模型,并将其集成到有限元软件ANSYS中。该模型考虑了非等温、非均匀变形过程中的微观结构演变,并与损伤动力学相结合。我们的模型弥合了位错动力学和连续介质力学之间的差距。根据2070铝锂合金微柱原位简单压缩试验对模型参数进行了标定。数值预测与实验结果进行了对比,包括应力-应变曲线和晶体织构演变。
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引用次数: 1
Computer-aided model of colonic propulsive activity 结肠推进活动的计算机辅助模型
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-797-803
O. A. Qatrawi, R. Miftahof
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引用次数: 0
Image Analysis Applications for the Study of Segregation in Lightweight Concretes 图像分析在轻量化混凝土离析研究中的应用
Pub Date : 2017-11-03 DOI: 10.2495/CMEM-V6-N4-835-846
A. Solak, A. Tenza-Abril, F. Baeza-Brotons
The use of lightweight concrete allows great flexibility and cost savings when it is used in building construction having a positive impact on the energy consumption of buildings due to its good thermal characteristics. However, it is also known that the differences between the densities of the materials used to produce these concretes make it highly susceptible to the segregation phenomenon. The main objective of the present work is to present a method to quantify this phenomenon using techniques of image analysis. In this work, a lightweight concrete produced was molded in cylindrical molds using different times of internal vibration and causing different degrees of segregation. The samples were cured, vertically saw-cut in two pieces (halves) and the sections were photographed. Subsequently, the halves were saw-cut horizontally in four equal parts and posteriorly their densities were determined experimentally. The densities obtained were used to calculate the segregation index of each sample (experimental method). Furthermore, the photographed sections were processed using image analysis software in order to determine the volumetric proportions of aggregates in each sample (noise reduction, threshold adjustment, binarization and fill holes). The processed images were used to calculate the densities and segregation index of the lightweight concrete produced through image analysis. In addition, using the photographed sections, a vertical density profile was programmed to analyze the distribution of the lightweight concrete components (mortar and aggregate). Finally, the results obtained experimentally and through image analysis were compared. This study demonstrates that the image analysis allows a deeper knowledge of the behavior of segregated concrete
轻质混凝土的使用允许极大的灵活性和节省成本,当它用于建筑施工时,由于其良好的热特性,对建筑的能源消耗有积极的影响。然而,众所周知,用于生产这些混凝土的材料密度之间的差异使其极易受到离析现象的影响。目前工作的主要目的是提出一种方法来量化使用图像分析技术的这种现象。在这项工作中,生产的轻质混凝土在圆柱形模具中成型,使用不同的内部振动次数并造成不同程度的离析。将样品固化,垂直锯切成两部分(半),并拍摄各部分。随后,将这些薄片水平切成四等份,然后通过实验测定其密度。所得密度用于计算各样品的偏析指数(实验方法)。此外,使用图像分析软件对拍摄的切片进行处理,以确定每个样本中骨料的体积比例(降噪、阈值调整、二值化和填充孔)。利用处理后的图像计算图像分析得到的轻量化混凝土的密度和离析指数。此外,利用拍摄的剖面,对垂直密度剖面进行编程,以分析轻质混凝土组件(砂浆和骨料)的分布。最后,对实验结果和图像分析结果进行了比较。本研究表明,图像分析可以更深入地了解分离混凝土的行为
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引用次数: 4
期刊
THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS
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