考虑土―结构相互作用的运转状态风电塔抗震分析

针对某陆上风电场1.5 MW风电塔结构,建立了"塔筒-基础-地基"整体三维精细有限元模型,研究土-结构相互作用对风机运转状态下风电塔结构地震动力响应的影响规律.在风机运转状态下,使用FAST程序把风速时程转化为风荷载时程输入模型,并使用EERA程序进行土层地震反应分析得到模型土层底部的地震波,作为地震激励进行输入,对风电塔进行模态分析并计算风电塔地震动力响应.研究表明,考虑土-结构相互作用效应会引起风电塔体系自振频率降低,并显著增加风电塔的结构动力响应.      

溶质钒原子与铁的[100](001)位错的相互作用

采用改进分析型EAM模型（MAEAM）研究了溶质钒与铁的[100]（001）位错的相互作用.对铁的[100]（001）位错及掺杂结构用分子动力学方法进行了弛豫.计算了钒在这些掺杂格点上的能量,以及溶质钒与铁的[100]（001）位错缺陷系统的能量,发现在位错芯区域钒的格点能高,随着钒与位错芯之间距离的增加,其格点能降低;溶质钒替代拉伸区位错芯位置的铁原子时,钒与位错的相互作用能最强,缺陷系统的能量最低、结构最稳定.     

2,2’-联吡啶-5,5’-二羧酸CuII 配合物的构筑、结构及性质研究

利用2,2’-联吡啶-5,5’-二羧酸、氧化铜和高氯酸在水热条件下得到了一个有趣的铜配合物[Cu（H₂bpdc）]·ClO₄（1）（H₂bpdc=2,2’-联吡啶-5,5’-二羧酸）.对其进行X射线单晶衍射,利用SHELXTL软件解析其结构,单晶结构分析表明配合物1为零维结构,分子间存在着丰富的氢键,通过氢键和弱的π-π相互作用使得配合物1形成一个三维网状结构.对配合物1和配体的固体荧光对比研究表明,配体与金属CuII离子配位后发生了荧光淬灭现象.利用热重分析研究了配合物1的热稳定性及热分解与晶体结构的关系.对开发新型多维有机金属框架结构及新型荧光材料具有一定的指导和借鉴意义.      

60-110E半移动破碎站结构模态分析

振动特性是反映结构动力响应的重要参数。它不受外加荷载的影响,仅与结构本身的形式、尺寸、材料有关。模态分析可以确定结构的振动特性,包括自振频率、周期和振型。为了防止结构在外加载荷的作用下发生共振,在有限元软件ANSYS中采用Block Lanczos模态提取法,对太原重工股份有限公司开发的60-110E半移动破碎站进行了模态分析,以此来判断破碎站钢结构的整体布置是否合理,以及整体刚度是否满足要求。     

流固耦合对脱硫塔结构简化模型的动力反应分析

为研究流固耦合对脱硫塔结构简化模型动力反应的影响,采用有限元程序(Adina)模拟脱硫塔结构简化模型在地震作用下的流固耦合效应.首先对脱硫塔结构进行合理简化,在不同液位下进行了脱硫塔结构的模态分析,研究了塔内液位高度对脱硫塔结构的频率和振型的影响;其次,通过对脱硫塔结构进行地震波加载,研究了塔内液位高度、地震波输入角度和加速度峰值对脱硫塔结构的位移和加速度的影响,并与试验结果进行比较.结果表明,脱硫塔结构的频率会随着液位增高而减小,塔内液位高度、地震波加载方向及加速度峰值对脱硫塔结构加速度的影响比较大,而对其位移影响不大.      

车辆-有砟轨道-桥梁系统动力分析模型及验证

针对桥上有砟轨道,利用耦合动力学理论,建立了车辆-有砟轨道-桥梁系统动力分析模型,编制了仿真计算程序.通过与既有理论分析结果和软件计算结果的对比,对本文所建模型的正确性进行了验证.该模型可用于研究车辆、轨道和桥梁结构的动力相互作用,可用于对车辆运行的舒适性以及桥上有砟轨道结构的动力特性进行预测评价.     

合金熔体结构和原子- 分子热力学模型

对金属熔体结构的研究证实熔体中存在短程有序结构,而含金属间化合物的合金熔体中发现了原子- 分子结合的团簇结构,即固态下的金属间化合物在熔体中并没有消失,而是以团簇结构（实际上就是液态的分子）存在,并与熔体中的自由原子存在化学平衡。从熔体结构出发,提出了适用于合金熔体的原子- 分子热力学模型。然后以Ca- Mg合金熔体为例,介绍了该模型的构建和求解方法,并计算了1010K下的Ca- Mg合金熔体中各物质的摩尔分数。最后,将计算得到的钙、镁摩尔分数与各自的实测活度值进行比较,发现两者吻合得较好。这从计算上证明了合金熔体中同时存在着金属原子和金属间化合物分子,两者处于动态化学平衡之中。且达到平衡时,金属原子的摩尔分数实际上就是各自的活度。因此,对于合金熔体而言,活度并不存在。     

一种光敏树脂结构的力学性能

新设计三维打印光敏树脂结构,其主要用在减震隔震组合结构中作为阻尼元件.首先利用微机控制电子试验机对其进行静力加载试验,得到静载下载荷—位移特性曲线,并计算得到特定点处等效弹性模量,利用疲劳机进行动力加载试验,得到结构件在从5 Hz到20 Hz不同频率下滞回曲线,并计算出相应等效阻尼系数.基于有限元法,建立光敏树脂结构有限元模型,并以和实验相同的工况进行静力学和动力学计算分析,并对试验数据和数值计算结果进行对比,得到计算结果与实测结果吻合良好,从而验证有限元模型的可行性.在此基础上通过有限元计算方法,研究不同几何参数缝隙宽度、内弧半径、外弧半径、厚度对光敏树脂结构特定点等效弹性模量以及等效阻尼系数的影响.此结构受力时,纵向保持刚度输出,维持小变形,横向位移放大,具有良好的减振和抵抗变形的能力.      

快速货运动车组铝合金车体结构强度分析研究

根据快速货运动车组铝合金车体结构特点,简化车体几何模型,建立相应的有限元模型。基于车体静强度计算标准,确定8种车体结构静强度的计算工况,在这些计算工况作用下,计算车体结构的静强度,计算在最大垂直载荷作用下车体结构刚度,以及车体结构模态,计算结果表明快速货运动车组车体结构的刚度、静强度和模态均满足车体结构设计要求。     

2-2-吡啶基-4-羟基喹唑啉锌配合物的合成、结构及荧光性质

利用 2-（2-吡啶基 ）-4-羟基喹唑啉和醋酸锌在水热法条件下合成了一个新型锌配合物 [（Zn（phdq）·2H₂O）] （1） （phdq=2-（2-吡啶基）-4-羟基喹唑啉）.结构分析表明配合物 1 为单分子结构,结晶于单斜晶系,P-1 空间群.在配合物 1 中存在着丰富氢键和 π…π 作用力,通过分子间氢键和 π…π 堆积作用力使得配合物 1 形成三维网状结构.对配合物 1 和配体的固体荧光研究表明配合物的荧光明显增强,其原因可能是配体与金属 ZnII离子配位后增加了结构中的刚性.这对于开发新型荧光材料具有一定的指导与借鉴意义.      

Modified Topographic Amplification Factors for a Single-Faced Slope due to Kinematic Soil-Structure Interaction

In this paper, we evaluate the additive effects of topography, soil nonlinearity, and soil-structure interaction (SSI) along the crest of an idealized 40?m high cliff-type topographic feature with slope inclination 300, where excessive damage was observed during the Athens 1999 earthquake. The objective of this paper is to investigate the relative contribution of topographic amplification, and kinematic SSI as a function of the incident motion frequency content and geotechnical site conditions for a surface and an embedded structure located at the cliff crest. For this purpose, we perform elastic parametric and nonlinear site-specific two-dimensional finite element simulations using three profiles and six input motions. We illustrate the role of SSI in altering the response at the location of peak topographic amplification potential behind the crest, the effects of incident motion incoherency on the transient structural response, and the beneficial contribution of structural embedment. We finally suggest that empirical models for base-slab averaging of shallow foundations, developed as a function of site conditions, structural dimensions and center line location, could be combined with topographic amplification factors to predict realistic design spectra for structures located on irregular topographic features.     

Soil-Structure Interaction and Pulse Shape Effect on Structural Element Damage to Blast Load

The mode approximation method (MAM) is an effective approach when analyzing dynamic structural responses and damages to blast loading. The pressure-impulse (P-I) diagram generated from the MAM provides an efficient and accurate estimation of structural damage of simple or combined failure modes. In the previous works for damage assessment of underground reinforced concrete structures, the soil-structure interaction (SSI) was simplified as a constant damping or stiffness effect, and the pulse shape effect of the blast load on the P-I diagrams was not discussed. In the present study, a generalized iteration procedure is adopted in derivation of the P-I equations on the basis of the MAM; therefore, the nonconstancy of SSI and the pulse shape effect on underground RC structure damage to blast load can be analyzed. Result of the present study shows that the nonconstancy of SSI and the pulse shape effect has certain effects, and they cannot be simply ignored in damage assessment of buried structures. The generalized iteration procedure is also proved a helpful tool in carrying out such analysis.     

SSI Effects on Ground Motion at Lotung LSST Site

A 3D finite-element model is developed to study soil-structure interaction (SSI) effects at a Large-Scale Seismic Test (LSST) site in Lotung, Taiwan, during the earthquake of May 20, 1986. Analyses are carried out by direct method incorporating a 1∕4-scale nuclear plant containment structure. The containment structure is modeled as a linearly elastic material, while the subsoil is modeled as an elastoplastic continuum material that deforms plastically according to a bounding surface plasticity theory with a vanishing elastic region. Eigenvalue analyses are performed to see how the presence of the structure affects the fundamental frequencies and modes of vibration of the system in the limit of elastic response. SSI effects are shown to be partly responsible for the reduced peak north-south ground surface acceleration recorded by a downhole array near the containment structure. Eigenvalue studies suggest that the local effect of the containment structure is to generate rocking and torsional vibration modes, in addition to the usual lateral and vertical modes. However, results of time domain studies indicate that the former modes (rocking and torsional) were not triggered by the 1986 earthquake.     

Modal Identification through Ambient Vibration: Comparative Study

An analytical comparison between three techniques for the identification of modal properties of structures when subjected to ambient vibrations is performed. The algorithms examined include the eigensystem realization algorithm with data correlations, the prediction error method through least squares, and the stochastic subspace identification (SSI) technique. Both analytical and experimental data from a four-storey building scaled at 1:3 are used to perform these evaluations. The level of noise added to the simulated data is varied to study the robustness of the techniques. All techniques are fully automated, allowing for assessments to be conducted through Monte Carlo simulations. The results indicate that the SSI technique provides the most accurate identification of natural frequencies and mode shapes even with high noise levels, all while requiring the least amount of experience for implementation.     

Dynamic Field Test, System Identification, and Modal Validation of an RC Minaret: Preprocessing and Postprocessing the Wind-Induced Ambient Vibration Data

The investigation of dynamic response for civil engineering structures largely depends on a detailed understanding of their dynamic characteristics, such as the natural frequencies, mode shapes, and modal damping ratios. Dynamic characteristics of structures may be obtained numerically and experimentally. The finite-element method is widely used to model structural systems numerically. However, there are some uncertainties in numerical models. Material properties and boundary conditions may not be modeled correctly. There may be some microcracks in the structures, and these cracks may directly affect the modeling parameters. Modal testing gives correct uncertain modeling parameters that lead to better predictions of the dynamic behavior of a target structure. Therefore, dynamic behavior of special structures, such as minarets, should be determined with ambient vibration tests. The vibration test results may be used to update numerical models and to detect microcracks distributed along the structure. The operational modal analysis procedure consists of several phases. First, vibration tests are carried out, spectral functions are produced from raw measured acceleration records, dynamic characteristics are determined by analyzing processed spectral functions, and finally analytical models are calibrated or updated depending on experimental analysis results. In this study, an ambient vibration test is conducted on the minaret under natural excitations, such as wind effects and human movement. The dynamic response of the minaret is measured through an array of four trixial force-balanced accelerometers deployed along the whole length of the minaret. The raw measured data obtained from ambient vibration testing are analyzed with the SignalCAD program, which was developed in MATLAB. The employed system identification procedures are based on output-only measurements because the forcing functions are not available during ambient vibration tests. The ModalCAD program developed in MATLAB is used for dynamic characteristic identification. A three-dimensional model of the minaret is constructed, and its modal analysis is performed to obtain analytical frequencies and mode shapes by using the ANSYS finite-element program. The obtained system identification results have very good agreement, thus providing a reliable set of identified modal properties (natural frequencies, damping ratios, and mode shapes) of the structure, which can be used to calibrate finite-element models and as a baseline in health monitoring studies.     

Seismic Response of Liquid Storage Tanks Incorporating Soil Structure Interaction

A frequency domain method is presented to compute the impulsive seismic response of circular surface mounted steel and concrete liquid storage tanks incorporating soil-structure interaction (SSI) for layered sites. The method introduces the concept of a near field region in close proximity to the mat foundation and a far field at distance. The near field is modeled as a region of nonlinear soil response with strain compatible shear stiffness and viscous material damping. The shear strain in a representative soil element is used as the basis for strain compatibility in the near field. In the far field, radiation damping using low strain soil response is used. Frequency dependent complex dynamic impedance functions are used in a model that incorporates horizontal displacement and rotation of the foundation. The focus of the paper is on the computation of the horizontal shear force and moment on the tank foundation to enable foundation design. Significant SSI effects are shown to occur for tanks sited on soft soil, especially tanks of a tall slender nature. SSI effects take the form of period elongation and energy loss by radiation damping and foundation soil damping. The effects of SSI for tanks are shown to reverse the trend of force and moment reduction under earthquake loading as is usually assumed by designers. The reasons for this important effect in tank design are given in the paper and relate to the very short period of most tanks, hence, period lengthening may result in load increase. A comparison is made with SSI effects evaluated using the code SEI/ASCE 7-02. Period elongation is found to be similar for relatively stiff soils when assessed by the code compared with the results of the dynamic analysis. For soft soils, the agreement is not as good. Code values of system damping are found to agree reasonably well with an assessment based on the dynamic analyses for the range of periods covered by the code. Energy loss by material damping and radiation damping is discussed. It is shown that energy loss may be computed using the complex dynamic impedance function associated with the viscous dashpot in the analytical model. The proportion of energy loss in the translation mode compared to that dissipated in the rotational mode is addressed as a function of the slenderness of the tank. Energy loss increases substantially with the volume of liquid being stored.     

城市土地利用变化中邻域相互作用的特征——日本三大都市圈的比较研究

Local spatial interaction between neighborhood land-use categories (i.e.neighborhood interaction) is an important factor which affects urban land-use change patterns.Therefore, it is a key component in cellular automata (CA)-based urban geosimulation models towards the simulation and forecast of urban land-use changes. Purpose of this paper is to interpret the similarities and differences of the characteristics of neighborhood interaction in urban land-use changes of different metropolitan areas in Japan for providing empirical materials to understand the mechanism of urban land-use changes and construct urban geosimulation models. Characteristics of neighborhood interaction in urban land-use changes of three metropolitan areas in Japan, i.e. Tokyo, Osaka, and Nagoya, were compared using such aids as the neighborhood interaction model and similarity measure function. As a result,urban land-use in the three metropolitan areas was found to have had similar structure and patterns during the study period. Characteristics of neighborhood interaction in urban land-use changes are quite different from land-use categories, meaning that the mechanism of urban land-use changes comparatively differs among land-use categories. Characteristics of neighborhood interaction reveal the effect of spatial autocorrelation in the spatial process of urban land-use changes in the three metropolitan areas, which correspond with the characteristics of agglomeration of urban land-use allocation in Japan. Neighborhood interaction amidst urban land-use changes between the three metropolitan areas generally showed similar characteristics. The regressed neighborhood interaction coefficients in the models may represent the general characteristics of neighborhood effect on urban land-use changes in the cities of Japan. The results provide very significant materials for exploring the mechanism of urban land-use changes and the construction of universal urban geosimulation models which may be applied to any city in Japan.     

Experimental and Numerical Study of Damaged Cantilever

The introduction of a crack in a steel structure will cause a local change in the stiffness and damping capacity. The change in stiffness will lead to a change of some of the natural frequencies of the structure and a discontinuity in the associated mode shapes. This paper contains a presentation of the results from experimental and numerical tests with hollow section cantilevers containing fatigue cracks. Two different finite-element (FE) models have been used to estimate the modal parameters numerically. The first FE model consists of beam elements. The second FE model consists of traditional rectangular shell elements and one rectangular shell element with a transverse, internal, open crack. The analytical results from the numerical models are compared with data obtained from experimental tests. The numerical models give good agreements with the experimental data. The beam model takes into account only the first mode of the crack evaluation. In the shell model all three modes of the crack growth are taken into account. Nevertheless, the results obtained for both models are satisfactory because the beam is subjected to bending. It can be concluded that it is sufficient to use crack models for calculating natural frequencies in bending, taking into account the first mode of the crack extension only.     

Vertical Excitation of Stochastic Soil-Structure Interaction Systems

This paper considers two stochastic models for a soil-structure interaction problem with vertical propagation of P waves during strong earthquake motion. These models include the horizontal and vertical spatial variability of stiffness of the soil medium. The first model involves a two-dimensional stochastic Winkler foundation, which takes into account the horizontal variability of the soil. This model elucidates some experimental results obtained on a nuclear power station physical model built in Hualien (Taiwan). The second model is developed as a continuum system of random columns involving, this time, horizontal and vertical random characteristics of the soil medium. For both models a statistical analysis was performed with respect to determining probabilistic properties resonance frequencies and amplitudes of the corresponding transfer functions. The theoretical development and numerical results demonstrate the importance of considering soil variability for geotechnical design applications.