共查询到20条相似文献，搜索用时 31 毫秒
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The article presents a theoretical investigation of the propagation of normally and obliquely incident plane shear waves past a rectangular trench filled up with water saturated soil sandwiched between anisotropic elastic media. The motivation for this work is due to the effectiveness of the isolation of waves by the in-filled rectangular trench. Unlike the most of the previous researchers, this model considers the soil–structure interaction effects and directly determines the influence of barrier in the form of in-filled trench on the mode of wave propagation. It is of interest to determine the reflection and transmission coefficients, and the energy partition distribution of shear waves in the in-filled rectangular trench showing the influence of barrier on the propagation of waves. An extensive parametric study through numerical computation is carried out to investigate the influence of the material properties of the in-filled trench and the amplitude ratios on shear waves. The in-filled trench barrier directly declines the intensity of waves significantly in such a way that the waves do not create any hazards to the nearby structures, if exists at all. 相似文献
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Although intensive research on Fe(0) permeable reactive barriers (PRB) for in situ groundwater remediation has been conducted and multiple applications have been installed in the past two decades, some properties of reactive materials in use have not been fully considered and discussed yet. In the present investigation, a typical granular cast iron has been characterized with different techniques. The grain size distribution not only has an influence on the resulting pore geometry and the surface area but material properties significantly differ between fine and coarse grains. Metallographic analyses revealed large differences in both graphite inclusions and microstructures that likely influence the reactivity. Both graphite and cementite proved to be more resistant toward acidic dissolution compared to Fe0. The intrinsic material characteristics described here have not been covered in the existing PRB literature. 相似文献
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Gianni Blasi Daniele Perrone Maria Antonietta Aiello 《Bulletin of Earthquake Engineering》2018,16(12):6105-6130
A wide number of experimental studies conducted in latest years pointed out the high influence of the mechanical properties of masonry units and mortar bed joints on lateral strength and stiffness of masonry panels. This feature significantly modifies the global response of infilled frames under seismic actions as well as the local interaction phenomena. Despite a wide investigation on the influence of the infills on global behaviour of reinforced concrete (RC) frames has already been provided, different features characterizing the seismic performances of buildings suggest the need of accurately evaluating local interaction phenomena as well as the influence of the panel on specific and relevant aspects, as the accelerations transferred to non-structural components. This study provides a parametrical analysis of the influence of shear strength and elastic modulus of masonry infills on the seismic behaviour of RC frames originally designed for gravity loads. Regular buildings with different height were analysed using the Incremental Dynamic Analysis in order to provide fragility curves, investigate on the collapse mechanisms and define the floor spectra depending on the properties of the infills. Results obtained pointed out the high influence of the considered parameters on the fragility of existing RC frames, often characterized by inadequate transversal reinforcement of columns, which may lead to brittle failure due to the interaction with the infills. Floor response spectra are also significantly affected by the influence of masonry infills both in terms of shape and maximum spectral accelerations. Lastly, on the basis of the observed failure mechanisms, a parameter defining the ductility of the frames depending on the properties of the infills was also provided (Capacity Design Factor). The correlation between the mechanical properties of the infills and this parameter suggests its reliability in the simplified vulnerability analysis of existing buildings as well as for the design of new buildings. 相似文献
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PeterDusicka AhmadM.ltani IanG.Buckle 《地震工程与工程振动(英文版)》2004,3(2):195-203
Non-linear finite element models accounting for large displacements have been used to investigate the behavior of steel built-up shear links that had previously been tested using large-scale experiments. The links were designed using steel grades with yield points ranging from high to low strengths. The objectives of the numerical analyses were to further investigate the non-linear behavior and to correlate the numerical results with experimental observations. Elasto-plastic as well as cyclic stress-strain material properties were incorporated to study the influence of material behavior on the overall shear link response. Non-linear monotonic analyses of the shear links incorporating the cyclic stress-strain steel properties resulted in similar trends in the response as the backbone curves recorded from the physical experiments. The numerical models of built-up shear links utilizing structural grade steels closely correlated to the experimentally recorded shear strength.Models utilizing low yield point steels overestimated the shear strength, which was caused by the characteristics of cyclic behavior of those steels. The detailed numerical models also allowed for investigation of the plastic strain demands on the different components of the link. It was shown that finite element models combined with appropriate stress-strain relationship may be used with confidence to check the design of shear links of different steel grades and sectional geometries. 相似文献
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Mette Thiel Nielsen 《地震工程与结构动力学》1982,10(3):497-510
The resistance of a soil to horizontal harmonic vibration of a vertical, end bearing pile with circular cross-section is theoretically investigated. The soil is considered to be a continuum with material damping of the hysteretic type. The motions of the soil and pile are expressed as series, and a resistance coefficient on each term in the series of the pile motion is found. The resistance is found to depend on the excitation frequency, the pile slenderness and on the material properties of the soil. Finally a study of the influence of the parameters is carried out. 相似文献
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Judith Wang Xiangwu Zeng D.A. Gasparini 《Soil Dynamics and Earthquake Engineering》2008,28(4):258-276
A proposed method for mitigating ground-borne vibration generated by high-speed trains is the usage of rubber-modified asphalt concrete as a ballast mat material. To gauge this material's influence in vibration control, a dynamic finite element code that models distinct damping properties in a large, nonhomogenous system was created. A linear hysteretic damping model is used to capture the dissipative mechanisms of each material; frequency domain substructuring is used for computational efficiency. Vibratory responses utilizing different ballast mat materials in a high-speed rail foundation are compared. It is shown that rubber-modified asphalt concrete results in a general reduction of motion, particularly in directions horizontally parallel and perpendicular to the train's passage. The described modeling procedure may be used for any dynamic analysis where the preservation of material damping characteristics is desired. 相似文献
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Influence of the nonlinear behavior of viscous dampers on the seismic demand hazard of building frames 总被引：1，自引：0，他引：1 
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下载免费PDF全文 This paper analyzes the influence of damper properties on the probabilistic seismic performance of building frames equipped with viscous dampers. In particular, a probabilistic methodology is employed to evaluate the influence of the damper nonlinearity, measured by the damper exponent, on the performance of structural and nonstructural components of building frames, as described by the response hazard curves of the relevant engineering demand parameters. The performance variations due to changes in the damper nonlinearity level are evaluated and highlighted by considering two realistic design scenarios and by comparing the results of a set of cases involving dampers with different exponents designed to provide the same deterministic performance. By this way, it is possible to evaluate the influence of the nonlinear response and of its dispersion on the demand hazard. It is shown that the damper nonlinearity level strongly affects the seismic performance and different trends are observed for the demand parameters of interest. A comparison with code provisions shows that further investigation is necessary to provide more reliable design formulas accounting for the damping nonlinearity level. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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为提高作为结构材料使用时硬质聚氨酯泡沫塑料(RPUF)的力学性能,在基体材料中添加增强材料形成了增强RPUF(RRPUF),RRPUF内部的材料组成及结构特征影响其力学性能.本文应用微焦点锥束体式工业CT技术,进行了玻璃纤维RRPUF三维结构的工业CT检测,获得了高分辨率的RRPUF三维结构CT图像,并解析了RRPUF内部结构特征,包括玻璃纤维及泡孔的形状、位置、尺寸、体积含量以及分布状况等.研究表明微焦点VCT技术可有效地实现RRPUF内部结构特征的检测及分析,为进一步研究RRPUF的性能提供了重要方法. 相似文献
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The elastodynamic response of coupled soil-pile-structure systems to seismic loading is studied using rigorous three-dimentional (3D) finite element models. The system under investigation comprises of a single pile supporting a single degree of freedom (SDOF) structure founded on a homogeneous viscoelastic soil layer over rigid rock. Parametric analyses are carried out in the frequency domain, focusing on the dynamic characteristics of the structure, as affected by typical foundation properties such as pile slenderness and soil-pile relative stiffness. Numerical results demonstrate the strong influence on effective natural SSI period of the foundation properties and the crucial importance of cross swaying-rocking stiffness of the pile. Furthermore, the notion of a pseudo-natural SSI frequency is introduced, as the frequency where pile-head motion is minimized with respect to free field surface motion. Dynamic pile bending is examined and the relative contributions of kinematic and inertial interaction, as affected by the frequency content of input motion, are elucidated. 相似文献
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Several building codes propose methodologies to account for epistemic uncertainties in the seismic assessment of masonry buildings by selecting a knowledge level and reducing material strengths by means of the associated value of the confidence factor. Previous works showed that, in the case of masonry structures, this approach has various limitations, such as the lack of proper consideration of experimental tests performed. This article focuses on the issue of imperfect knowledge on material properties of existing masonry buildings and proposes a probabilistic methodology for the assessment, based on Bayesian updating of mechanical properties. The use of a Bayesian approach allows to update the values of the material properties assumed a priori as knowledge on the building increases, by taking into account all the experimental information gathered during the assessment process. A large number of simulated assessments is carried out and the values of the confidence factors on material properties are defined through the comparison between the obtained results and those of the reference structure, assumed to be perfectly known. These factors are useful in a more general framework for the assessment of masonry buildings accounting for different sources of uncertainty. 相似文献
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Mechanical recovery of oil by oil sorbents is one of the most important countermeasures in marine oil-spill response. Polypropylene is the ideal material for marine oil-spill recovery due to its low density, low water uptake and excellent physical and chemical resistance. Different forms of polypropylene nonwoven sorbents were evaluated in this study in terms of initial oil-sorption capacities and oil-retention properties. The investigation revealed that the fibre diameter, sorbent porosity and oil property are the most important factors in the oil-sorption performance of polypropylene nonwoven sorbents. 相似文献
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Paolo Ricci Maria Teresa De Risi Gerardo Mario Verderame Gaetano Manfredi 《Bulletin of Earthquake Engineering》2013,11(5):1585-1616
A growing attention has been addressed to the influence of infills on the seismic behavior of Reinforced Concrete buildings, also supported by the observation of damage to infilled RC buildings after severe earthquakes (e.g. L’Aquila 2009, Lorca 2011). In this paper, a numerical investigation on the influence of infills on the seismic behavior of four different case study buildings is carried out: four- and eight-storey buildings, designed for seismic loads according to the current Italian technical code or for gravity loads only according to an obsolete technical code, are considered. Seismic capacity at two Limit States (Damage Limitation and Near Collapse) is assessed through static push-over analyses, within the N2 spectral assessment framework. Different infill configurations are considered (Bare, Uniformly Infilled, Pilotis), and a sensitivity analysis is carried out, thus evaluating the influence of main material and capacity parameters on seismic response, depending on the number of storeys and the design typology. Fragility curves are obtained, through the application of a Response Surface Method. Seismic performance is also expressed in terms of failure probability, given a reference time period. 相似文献
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以黄土、砂为骨料,石膏、水泥为胶结材料,水为调节剂,以正交试验方法配制出V级围岩相似材料,该材料能够很好的模拟隧道Ⅴ级软弱围岩。在此基础上,以钢筒模型试验为媒介,通过千斤顶配合反力架加载,观察不同材料配比下的试验组应力变化斜率、自稳时间、应变大小等方面的差异,结合加载完成后模型开口处岩体变化情况,探索高地应力下Ⅴ级围岩开挖卸载效应。试验结果表明:虽然相似材料会因配比不同改变物理力学性质,但主要是对弹性模量的影响较大;在增大垂直压力作用下,试验中材料自稳时间变长,应力释放也较为彻底,但整体趋势放缓。 相似文献
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Kung-Juin Wang Ming-Chieh Chuang Keh-Chyuan Tsai Chao-Hsien Li Pu-Yuan Chin Shen-Yuo Chueh 《地震工程与结构动力学》2019,48(3):347-365
This paper describes a series of hybrid tests performed on a steel panel damper (SPD) specimen by using a multi-axial testing system. The building under investigation adopted a three-dimensional six-story moment resisting frame with four SPDs installed at each story as the main seismic resisting system. The structural model was subjected to bi-directional ground excitations of three hazard levels. The finite element analysis program “Platform of Inelastic Structural Analysis for 3D Systems” (PISA3D) was used as the analysis kernel for hybrid tests. Relevant programming extensions in PISA3D were created to support geographically distributed hybrid testing in a general-purpose manner. An external displacement control (EDC) method was developed such that the actual boundary deformation of the specimen fixtures could be continuously measured and immediately compensated during tests. An online model updating (OMU) technique was developed and employed such that the material properties of the specimen could be identified directly from the specimen response during the test. The identified material properties were then immediately used to update those of the other relevant numerical elements to enhance the overall simulation fidelity. Superior flexibility of the underlying software architecture was well demonstrated in this series of hybrid tests since no hardcoding was used to support all the complex test settings. Test results confirmed the effectiveness of the proposed EDC method, as well as the capacity of the proposed OMU technique to satisfactorily and efficiently capture the hysteretic properties of the specimen. 相似文献
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The reason for detailed investigation of problems related to earthquake phenomena, their prediction and undertaking of necessary protection measures, results from their disastrous consequences. Besides material damage, the loss of human lives is far too priceless.One of the main problems related to investigation of earthquake occurrence phenomenon is the problem of definition of earthquake released energy.Accelerations are also recognized as a very significant parameter used for solution of many problems.Such a problem is the definition of the released energy through the material expressed in a form of acceleration; the largest source being the energy released from earthquake origins.Definition of seismicity on the soil surface due to the effects of the released energy during an earthquake is carried out by using accelerations, velocities and displacements.In this respect, the author of this paper makes an attempt to point out the shortcomings in the existing analytical expressions for definition of ground accelerations. A new solution is also proposed by introducing a new concept in dissipation of the released energy through a material and by introducing a new factor which includes the main parameters and characteristics of the entire frequency content of the considered material. 相似文献
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Microstructure measures and the minimum size of a representative volume element: 2D numerical study 总被引：1，自引：0，他引：1
In the paper, a numerical study of the size of a representative volume element (RVE) for both the heat flow as well as the linear elasticity problems is presented. A particular two-phase random microstructure is studied and the method is applied to the digital image of reconstructed 2D realization of random media. The minimum size of RVE is determined by the investigation of the convergence of apparent properties as the size of RVE is increasing. Then, two estimates of the minimum RVE size are proposed and it is shown that the estimates are in a good agreement with the results determined by the investigation of the convergence of apparent properties. The minimum size of RVE can be successfully predicted based only on the microstructure morphology. The statistical measures used in this work are: the two-point probability and the linealpath functions. 相似文献
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基于损伤塑性模型的砌体墙体非线性有限元分析 总被引：2，自引：0，他引：2
为了研究砌体墙体用钢结构加固后的力学性能,需要提供较准确的砌体墙体非线性计算,考虑到砌体与混凝土的材料性质具有相似性,将混凝土损伤塑性模型经修正后应用于砌体数值模拟,实现对砌体墙体的非线性有限元分析。通过与水平加载试验结果对比,验证了有限元模型的正确性。探讨了损伤塑性模型中的粘性系数、膨胀角、砌体本构关系中的初始弹性模量、受拉应力应变关系对计算结果的影响。结果表明：粘性系数和膨胀角对抗剪承载力、峰值位移及下降段性能均有较大影响,而对初始刚度影响很小;随着初始弹性模量的增大,砌体墙体抗剪承载力随之提高,但峰值位移无明显变化;受拉应力应变方程中待定系数的取值,对抗剪承载力及峰值位移影响较大。 相似文献
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Fiber reinforced soil behaves as a composite material in which fibers of relatively high tensile strength are embedded in a matrix of soil. Shear stresses in the soil mobilize tensile resistance in the fibers, which in turn imparts greater strength to the soil. In this paper a study on the influence of synthetic fibrous materials in improving the dynamic response characteristics of fine sandy soil is reported. The project aims at converting fibrous carpet waste into a value-added product for soil reinforcement. A series of five shaking table tests using rigid box were carried out on Toyoura sand specimens reinforced with randomly distributed geotextile strips. The dynamic deformation characteristics of the reinforced sand are defined in terms of wall lateral deformation and rotation. The results clearly indicate the effectiveness of fiber reinforcement in improving dynamic properties of fine sand and deformation characteristics of fiber reinforced sheet pile retaining wall during shaking. 相似文献