工作桥对进水塔整体结构的抗震性能影响研究

地震作用下,进水塔与工作桥、库水、地基的相互作用复杂。通过建立塔身主体结构-启闭机房-工作桥-地基-库水整体有限元模型,基于势流体理论模拟结构与库水的相互作用,采用黏弹性人工边界考虑地基辐射阻尼,研究结构与库水、工作桥和地基的动力相互作用对进水塔整体体系自振特性和地震动力响应的影响。结果表明：在正常蓄水位下,工作桥的存在会使进水塔结构的顺流向位移最大减小25.15%,加速度最大减小14.33%,进水塔关键点最大拉应力降幅可达12.0%以上;考虑地基的辐射阻尼效应时,进水塔结构的动力响应明显减小,其关键点的最大拉应力降幅可达40%以上。相比工作桥,地基辐射阻尼效应对进水塔地震作用下动水压力、加速度、位移和应力响应的影响更加显著。     

气垫载荷在带裂缝冰面运动的水弹性响应

气垫船在冰面上运动会激起冰面产生水弹性波.在特定条件下,此水弹性波使得冰层内部的应力达到最大值,甚至超过冰层的极限承载应力而发生破坏.为此,该文研究了冰面裂缝对于气垫载荷引起的冰面水弹性响应的影响.基于弹性薄板假设和势流理论,建立了气垫载荷在带裂缝冰面上运动的理论数学模型.在模型求解上,采用边界元法对流体域进行求解,冰...     

频域内求解移动荷载作用下三维层状场地动力响应的理论推导

基于Hung教授所做移动荷载作用下弹性半空间的振动分析,给出了频域内求解移动荷载作用下三维层状场地动力响应的理论推导,得到弹性半空间动力刚度矩阵和单层土动力刚度矩阵;根据相邻层连接处的平衡条件和变形协调条件,得到具有对称性精确分析、且不受土层厚度影响的整体刚度矩阵。本理论分析方法可用于求解三维层状场地在车辆移动荷载作用下的动力响应问题。     

海上风机基础高阶水动力荷载数值模拟研究

在实际海洋环境下,海上风机结构常常承受非线性波浪和系泊系统的联合作用,探究海上浮式风机基础高阶水动力荷载及其运动响应非常重要.该文基于非线性势流理论和摄动展开技术,建立了海上浮式风机基础与波浪和系泊系统耦合作用的二阶时域高阶边界元数值分析模型,研究了OC4-DeepCwind半潜浮式风机基础在波浪作用下的动力响应特性....     

水下桩腿长度对带支腿浮式结构水动力系数的影响分析

风电安装船是带支腿浮式结构,而水下桩腿长度对船体在波浪中的动力响应会产生较大的影响。究其原因就是水下支腿的存在导致结构所受水动力不同于普通无支腿船体。为了研究水下桩腿长度对水动力系数大小的影响,该文利用三维势流理论对桩腿收放过程中不同阶段的水动力系数进行了数值计算,给出了不同工况下带支腿浮式结构在波浪中运动的6个自由度水动力系数与波浪频率的关系。研究结果表明:桩腿水下长度对带支腿浮式结构水动力系数的影响较为明显,除垂荡运动外,附加质量随桩腿在水下的长度的增加而增大;当波浪频率处于低频或高频时,桩腿的水下长度对附加阻尼的影响较小,而当波浪频率处于中频时,附加阻尼系数随运动状态的不同表现出不同的规律。此外,还分析了桩腿对带支腿浮式结构湿固有频率的影响,结果反映出桩腿在水下的长短对结构的湿固有频率有明显的调制作用。     

基于黏弹性人工边界的拱坝动力响应分析

无限地基的辐射阻尼是影响拱坝地震反应的一个重要因素,无限边界的处理方法很多,其中黏弹性人工边界具有较高的计算精度和计算效率、较好的稳定性,同时程序容易实现。基于黏弹性人工边界的基本原理,以Ansys为计算平台,采用声学流体单元fluid30模拟库水,在坝基截断边界添加弹簧-阻尼单元以考虑无限地基的辐射阻尼影响;并以锦屏一级高拱坝在El Centro地震波作用下的动力响应分析为例,对不考虑坝基辐射阻尼与采用黏弹性人工边界两种计算方法的计算结果进行比较。结果表明,采用黏弹性人工边界条件后的动力响应(动水压力、位移、主应力)均有所降低,坝顶拱冠处的应力分布更为合理,动力响应时程滞后;验证了该边界条件的吸能效果。该方法计算效率高、稳定性好,克服了透射边界与有限元相结合的方法存在高频失稳问题的缺陷。     

涌潮荷载下桩式丁坝的动力响应

通过势流理论研究了简谐荷载作用下的无黏性流-圆桩-土体系统的动力响应。采用动力Winkler弹性地基梁模型模拟桩与土的相互作用，考虑无黏性流体和桩体的耦合作用，将圆桩散射的特征函数展开，由解析法给出了埋置在土中的圆桩在无黏性流体中的稳态动力响应。最后将实测的钱塘江涌潮冲击荷载用傅立叶变换展开成正余弦荷载。考虑由流体黏性引起的速度力和黏性阻尼的Morison公式的速度力分项，研究分析了涌潮作用下桩式丁坝的受力特性及桩身振动响应。计算结果表明：埋置桩的自振频率较高，而涌潮荷载中高频分量相对较小，所以涌潮下桩式     

系泊系统对海上浮式风机运动响应的影响分析

通过建立一种海上浮式风机运动响应的时域耦合数值计算方法,分析系泊系统对于运动响应的影响。该计算方法由气动力模块、水动力模块、系泊模块和浮体运动求解模块组成。气动力模块采用叶素动量法;水动力模块采用势流理论,通过边界元法进行数值模拟;系泊模块采用悬链线模型,利用Chebyshev多项式拟合计算;浮体运动求解模块采用Runge-Kutta法进行时域计算。根据对OC3-Hywind spar浮式风机进行建模求解,分析了系泊系统对于浮式风机运动响应的影响。     

基于三维黏弹性边界的混凝土重力坝抗震性能分析

为进一步推动三维黏弹性人工边界在坝工抗震领域的研究和应用,更为方便地实现边界设置和波动输入方法与大型商业软件相结合,基于黏弹性边界基本理论及ANSYS有限元软件中的弹簧—阻尼单元,编制了三维黏弹性人工边界程序,该程序可有效求出边界结点的等效荷载,从而可以实现黏弹性边界单元的波动输入。然后,通过数值算例验证得出地表位移最大值接近入射波幅值的2倍,说明该程序的计算结果具有较高的精度。最后,将黏弹性边界单元及地震波入射方法应用到巴基斯坦玛尔水电站典型溢流坝段的抗震分析中,计算结果显示,在设计地震作用下坝体的动力响应峰值较固定边界下可减小20%~40%,说明考虑无限地基阻尼影响是很有必要的。     

基于OpenSees的二维黏弹性边界单元开发及应用

基于有限元开源软件OpenSees开发了二维黏弹性边界单元VS2D2Bar,采用数值算例验证了该二维黏弹性边界单元在程序实现上的正确性,并将其应用于重力坝地震响应分析。重力坝算例分析结果表明:与固定边界无质量地基模型相比,采用黏弹性边界单元分析得到的坝体动力响应峰值大幅度减小,在重力坝的地震响应分析中必须考虑无限地基辐射阻尼效应的影响;OpenSees适用于重力坝地震响应分析,编程开发和调试工作量较小,易于在复杂水工结构的静动力分析研究中推广应用。     

ANALYTICAL MODELS OF FLOATING BRIDGES SUBJECTED BY MOVING LOADS FOR DIFFERENT WATER DEPTHS

There are two types of floating bridge such as discrete-pontoon floating bridges and continuous-pontoon floating bridges. Analytical models of both floating bridges subjected by raoving loads are presented to study the dynamic responses with hydrodynamic influence coefficients for different water depths. The beam theory and potential theory are introduced to produce the models. The hydrodynamic coefficients and dynamic responses of bridges are evaluated by the boundary element method and by the Galerkin method of weighted residuals, respectively. Considering causal relationship between the frequencies of the oscillation of floating bridges and the added mass coefficients, an iteration method is introduced to compute hydrodynamic frequencies. The results indicate that water depth has little influence upon the dynamic responses of both types of floating bridges, so that the effect of water depth can be neglected during the course of designing floating bridges.     

应用比例边界有限元法研究波浪与带狭缝三箱作用的共振现象

比例边界有限元法（SBFEM）是一种半解析的新数值分析方法,比完全数值方法具有更高的分析精度.本文应用该方法求解波浪与有限水深中三个相同,但之间存在狭缝的二维固定方箱的作用问题,为波浪与多模块超大型浮体的相互作用提供一些规律。文中给出了各箱的波浪力及反射、透射系数的数值结果,与BEM结果进行了比较,吻合良好.发现波浪与三箱的作用存在双共振现象而且中间箱的共振形式与两边箱不同.进一步分析了箱体吃水深度、狭缝宽度和箱体宽度对三箱共振频率的影响.这对超大型浮体水动力分析和结构设计具有一定的参考价值。数值结果证实该方法用较少单元便能得到精确结果,这为超大型浮体的水动力分析提供了一个可行的分析方法。     

AN OPTIMIZATION OF EIGENFUNCTION EXPANSION METHOD FOR THE INTERACTION OF WATER WAVES WITH AN ELASTIC PLATE

The hydroelastic interaction of an incident wave with a semi-infinite horizontal elastic plate floating on a homogenous fluid of finite depth is analyzed using the eigenfunction expansion method. The fluid is assumed to be inviscid and incompressible and the wave amplitudes are assumed to be small. A two-dimensional problem is formulated within the framework of linear potential theory. The fluid domain is divided into two regions, namely an open water region and a plate-covered region. In this paper, the orthogonality property of eigenfunctions in the open water region is used to obtain the set of simultaneous equations for the expansion coefficients of the velocity potentials and the edge conditions are included as a part of the equation system. The results indicate that the thickness and the density of plate have almost no influence on the reflection and transmission coefficients. Numerical analysis shows that the method proposed here is effective and has higher convergence than the previous results.     

An iterative Rankine BEM for wave-making analysis of submerged and surface- piercing bodies in finite water depth

A 3-D iterative Rankine Boundary Element Method （BEM） for seakeeping problem in time domain is developed in the framework of linear potential theory. Waves generated by both submerged and surface-piercing bodies moving at a constant forward speed in otherwise calm water, and the resultant steady wave pattern, wave profile and resistance are computed to validate this newly-developed code. A rectangular computational domain moving with the same forward speed as the body is introduced, in which an artificial damping beach is installed at an outer portion of the free surface except the downstream side for satisfying the radiation condition. The velocity potential on the ship hull and the normal velocity on the free surface are obtained directly by solving the boundary integral equation, with the Rankine source used as the kernel function. An iterative time-marching scheme is employed for updating both kinematic and dynamic free surface boundary conditions to stabilize the calculation. Extensive results including the wave patterns, wave profiles and wave resistances for a submerged spheroid and a Wigley hull with forward speed are presented to validate the efficiency of the proposed 3-D time-domain higher-order approach. Finally, the sensitivity of ship-generated waves to the water depth is investigated. Computed results show satisfactory agreement with the corresponding experimental data and other numerical solutions.     

高拱坝泄洪振动水弹性模型

以小湾工程为背景，通过水弹性模型实验，判断高拱坝泄洪所引起的振动和影响，采用自己研制的物理和力学性能优良的加重橡胶材料，在计算机的辅助下，建成了１：１５０比尺的水弹性实物模型，完善了对库水－地基－坝体－脉动荷载相互作用的模拟；采用先进的测试手段和分析软件包，对该模型的模态和多种工况泄水响应进行了全面的测试与分析，并采用计算机数值模拟与实验成果相结合的方法对坝身泄洪振动进行了结构动力分析及反分析和反     

三峡水利枢纽导流底孔闸门泄流振动监测与分析

对三峡水利枢纽工程导流底孔闸门动力安全监测资料作了介绍与分析,其中包括闸门的动力特性和在设计水位条件下闸门在动水启闭过程中的振动加速度、振动位移、动静应力、脉动压力和启闭力的监测成果。监测成果表明闸门的自振频率监测成果与闸门水弹性模型试验成果很接近,振型相同;在动水开门和关门过程中,闸门在小开度时,下游面底缘的脉动压力较大;闸门门叶和支臂的振动小开度比大开度的大,未出现危害性振动,各测点的振动位移和振动应力都比较小,闸门振动是安全的。     

A three-dimensional hydroelasticity theory for ship structures in acoustic field of shallow sea

Nowadays the development of green ship technology requires the vibration and noise control of oceangoing ships. The three-dimensional hydroelasticity theory of ships was previously extended to include the effect of fluid compressibility. This enables the dynamic responses and the acoustic radiations of a ship excited by onboard machineries or fluid fluctuation loads to be predicted. In this paper the hydroelastic analysis and sonoelastic analysis methods are fixrther incorporated with the Green＇s function in the Pekeris ocean hydro-acoustic waveguide model to work out a three-dimensional sonoelastic analysis method for ships in the ocean hydro-acoustic environment. As examples, the sound radiations of a floating elastic spherical shell excited by a concentrated force and a traveling LNG ship excited by the propeller induced pulsating forces acting on the wetted bottom plate of the stem in the shallow sea environment are predicted. The influences of the free surface and the sea bed on the generalized hydrodynamic coefficients and the acoustic pressure distributions in fluid domain are illustrated and discussed.     

Flexural-gravity wave resistances due to a moving point source on 2-D infinite floating beam

The flexural-gravity wave responses due to a load steadily moving or suddenly accelerated along a rectilinear orbit are analytically studied within the framework of the linear potential theory. A thin viscoelastic plate model is used for a very large floating structure. The initially quiescent fluid in the ocean is assumed to be homogenous, incompressible, and inviscid, and the disturbed motion be irrotational. A moving line source on the plate surface is considered as a moving point in the two-dimensional coordinates. Under the assumptions of small-amplitude wave motion and small plate deflection, a linear fluid-plate coupling model is established. The integral solutions for the surface deflections and the wave resistances are analytically obtained by the Fourier transform method. To study the dynamic characteristics of the flexural-gravity wave response, the asymptotic representations of the wave resistances are derived by the residue theorem and the methods of stationary phase. It shows that the steady wave resistance is zero when the speed of moving load is less than the minimal phase speed. The wave resistances due to the accelerate motion consist of two parts, namely the steady and transient wave responses. Eventually the transient wave resistance declines toward zero and the wave resistance approaches the steady component as the time goes to the infinity. Furthermore, the effect of the strain relaxation time for this viscoelastic plate is studied and it exhibits more influence for a high-speed motion.     

闸门流激振动全水弹性模型试验的原型验证

由于弹性结构与其周围流场存在着复杂的相互作用,单纯数值方法还不能正确预报这种水弹性振动,因此,水弹性模型试验已成为预报流场中结构原型行为的唯一方法.在对水弹性振动模型相似准则和研制的闸门水弹性振动模型材料性质简要介绍的基础上,对三峡大坝导流底孔弧形闸门全水弹性模型振动试验成果和其原型振动观测成果作了多方面对比分析.结果表明:全水弹性模型试验预报的原型闸门的动力特性、振动加速度、结构动静应力与原型闸门在相近条件下的实测成果颇为一致,从而验证了闸门全水弹性模型对原型闸门流激振动行为预报的可靠性.     

基于预处理共轭梯度法的桥梁移动荷载识别

 时域法（TDM）是移动荷载识别最有效的方法之一,它通过桥梁时域测量响应,间接识别桥梁移动荷载。针对时域法（TDM）有时识别精度较低、受噪声干扰的影响较大等问题,提出采用预处理共轭梯度法（PCGM）识别桥梁移动荷载。以两轴时变移动荷载识别为例,进行数值仿真研究,得到不同噪声水平下预处理共轭梯度法和时域法的识别结果。通过比较2种方法的识别精度,可以发现预处理共轭梯度法具有识别精度高、抗噪能力强、收敛速度快、初始参数设置少等优点,特别当仅仅采用弯矩响应识别移动荷载时,其识别精度仍然很高,这为移动荷载识别方法的实际应用打下了基础。