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1.
为了研究海底防沉板-桩复合基础在竖向荷载作用下的受力变形特性,以我国南海某200m水深项目为研究对象,将防沉板-桩复合基础简化为防沉板加角桩的形式,利用FLAC3D数值模拟软件建立了防沉板-桩复合基础数值计算模型。研究了海底防沉板-桩复合基础在竖向荷载作用下海床土体、防沉板、桩身的受力变形特性,并对不同竖向荷载作用下海床土体沉降、防沉板弯矩、桩身位移、桩身弯矩进行了对比分析。研究表明:防沉板的正负弯矩最大值分别出现在防沉板中部和防沉板与桩顶端的连接处,荷载越大,对防沉板的影响越大,桩在防沉板-桩复合基础中的作用越大;荷载越大,桩身产生的水平位移越大,其倾斜程度也越大;竖向荷载较小时,桩身同时出现正负弯矩,竖向荷载较大时,桩身只有正弯矩或只有负弯矩;复合基础的破坏容易发生在防沉板与桩身顶端的连接处。研究内容和计算结果可为防沉板-桩复合基础的设计提供合理可靠的理论依据。  相似文献   

2.
沉管隧道地震响应分析中的三维接触模型与算法研究   总被引:3,自引:0,他引:3  
针对土体与埋置在土体中的管段以及沉管隧道各个柔性接头处不同构件之间的动力相互作用,采用基于超级计算机的三维接触模型对上海某沉管隧道进行了地震响应分析,并进行了三维接触算法的研究。整个模型单元数超过了120万,节点数超过了100万。研究证明,应用文中提出的接触模型和算法可将接触处理的CPU时间大大缩短。地震波载荷选用调幅后的唐山地震波,应用通用非线性动力分析有限元程序LS-DYNA进行求解,计算结果可为隧道的抗震设计提供有力依据。  相似文献   

3.
沉管隧道横向地震响应分析是沉管隧道结构抗震设计的重点.根据沉管隧道的结构特点和接头剪力键的节点构造,建立了沉管隧道的多刚体-剪切铰-黏性阻尼铰多体动力学模型,并应用多体动力学中的离散时间传递矩阵法(multibody system discrete time transfer matriX method,MS—DT-TMM)建立了数学模型及表达式,同时编写Matlab程序进行求解实现.设定算例分别采用MS—DT—TMM和传统有限元法(finite element method,FEM)对沉管隧道横向地震响应进行对比分析,两者吻合较好,表明MS—DT-TMM应用于沉管隧道横向动力响应分析的可行性和有效性.  相似文献   

4.
在柱壳的有限元计算中,采用Mindlin八结点杂交壳单元和增量荷载法,基于选择积分,缩减积分及完全积分三种积分模式编制了分层计算各种厚度板壳的有限元程序FEAM,并对中厚圆柱壳在局部法向均布荷载作用下的弹塑性有限变形和屈曲问题进行了分析和计算,算例表明,利用FEAM可对壳体屈曲的临界荷载及屈曲后结构的承载与形状改变作定性与定量的分析.  相似文献   

5.
为了解决超大沉管管节在深水条件下线性精确控制的技术难题,并找出管节水下调整时的运动规律,依托港珠澳大桥沉管隧道现场复杂海况的施工条件,通过理论分析建立了内部调整方法的受力模型;并通过解析计算和数值仿真进行了有限位千斤顶和无限位千斤顶情况下沉管顶推过程中运动规律的分析研究,揭示了先铺法沉管水下轴线调整过程受力机理及运动规律。计算得出了沉管初始启动运动力学旋转点位置并进行了验证。实测纠偏沉管尾端偏差为38.3mm时实际实用推力为28800kN,与计算结果偏差仅为240kN,偏差率为8.4%,有效地验证了沉管基床之间摩擦受力的原理与技术参数。  相似文献   

6.
用有限个横条带法构造了板桁组合结构板段考虑局部屈曲的空间位移模式,基于三维连续体的虚功增量方程,导出了横向条带板段单元的UL列式,并考虑了板段单元位形变化的影响,此计算方法自由度少,计算精度高,能用于大型板桁结构的几何非线性分析,文末计算了广东西江桥板桁组合结构模型梁,计算结果与实测结果吻合较好。  相似文献   

7.
用有限个横向条带法构造了板桁组合结构板段考虑局部屈曲的空间位移模式。基于三维连续体的虚功增量方程,导出了横向条带板段单元的UL列式,并考虑了板段单元位形变化的影响。此计算方法自由度少,计算精度高,能用于大型板桁结构的几何非线性分析。文末计算了广东西江桥板桁组合结构模型梁,计算结果与实测结果吻合较好。  相似文献   

8.
考虑路面板和地基的相互作用,将路面板作为三维弹性体,建立路面板-层状多相弹性地基动力响应的三维多相层状弹性半空间体模型,分析了移动荷载作用下路面板-多相弹性地基系统的动力响应.将移动单元法引入到两相饱和弹性介质的半解析方法中,构造了随荷载按照相同速度运动的移动层单元,基于移动坐标下两相饱和弹性介质的动力控制方程和边界条件,应用加权残数法建立了两相弹性介质移动层单元动力方程,该方程可退化为单相弹性介质移动层单元动力方程,基于此,建立了移动荷载下多相弹性地基与路面板系统的三维动态响应的统一的半解析方程.并以两相饱和弹性半空间地基-单相弹性地基-路面板所形成的路面结构为例,数值分析了荷载速度、饱和层渗透系数、弹性层厚度等参数对路面板位移和土体孔压响应的影响.研究结果表明移动单元法是研究移动荷载下路面结构动态响应的一种有效的方法.  相似文献   

9.
沉管隧道柔性接头的力学性能是其抗震设计的关键准则. 用有限元方法模拟接头的非线性力学性能需要解决接头处材料非线性和接触非线性两个问题. 为简化分析计算,该文采用分段线性化的方法表征接头的材料非线性问题,引进调整因子改进接触算法中的判断条件,处理接头的边界非线性问题. 通过沉管隧道接头的三维精细化建模,研究了沉管隧道接头在拟静力载荷下的响应,获得了接头的轴向等效刚度曲线、抗弯刚度曲线和非线性耦合的剪切特性曲线,进而分析了不同轴向压力对接头剪切特性的影响.  相似文献   

10.
本文首先利用波函数展开法推导了弹性半空间中埋管的地基轴向阻抗函数计算公式.然后采用层状地基中无限长线激振荷载薄层法基本位移解,结合容积法求解了层状地基中埋管的地基轴向、垂直及水平阻抗函数.分别用两种方法计算了弹性全空间、弹性半空间地基内埋管的地基轴向阻抗函数,两者的计算结果符合良好,验证了用薄层法求解的可行性.本文还利用薄层法分析了弹性半空间内埋管的埋深对地基水平、垂直及轴向阻抗函数的影响;计算了弹性半空间内埋管的轴向刚度系数并与我国及日本的相关规范对比分析;计算分析了上海典型层状地基内地铁隧道的地基阻抗函数.  相似文献   

11.
An inviscid theoretical method that is applicable to non-periodic motions and that accounts for large amplitudes and non-planar wakes (large-angle unsteady thin airfoil theory) is developed. A pitch-up, hold, pitch-down motion for a flat plate at Reynolds number 10,000 is studied using this theoretical method and also using computational (immersed boundary method) and experimental (water tunnel) methods. Results from theory are compared against those from computation and experiment which are also compared with each other. The variation of circulatory and apparent-mass loads as a function of pivot location for this motion is examined. The flow phenomena leading up to leading-edge vortex shedding and the limit of validity of the inviscid theory in the face of vortex-dominated flows are investigated. Also, the effect of pitch amplitude on leading-edge vortex shedding is examined, and two distinctly different vortex-dominated flows are studied using dye flow visualizations from experiment and vorticity plots from computation.  相似文献   

12.
Distributed Point Source Method (DPSM) is a semi-analytical technique that can be used to calculate the ultrasonic field (pressure, velocity and displacement fields in a fluid, or stress and displacement fields in a solid) generated by ultrasonic transducers. So far the technique has been used to model ultrasonic fields in homogeneous and multilayered fluid structures, and near a fluid–solid interface when a solid half-space is immersed in a fluid. In this paper, the method is extended to model the ultrasonic field generated in a homogeneous isotropic solid plate immersed in a fluid. The objective of this study is to model the generation of guided waves in a solid plate when ultrasonic beams from transducers of finite dimension strike the plate at different critical angles. DPSM results for a solid half-space problem are compared with the finite element predictions to show the superiority of the DPSM technique. The predicted results are also compared with the experimental visualization of the mode patterns of Lamb waves propagating in a glass plate obtained from stroboscopic photoelastic method. Experimental and theoretical results show good qualitative agreement. The DPSM technique is then applied to study the mode patterns in aluminum plates immersed in water.  相似文献   

13.
A hybrid Cartesian/immersed boundary code is developed and applied to interactions between a flexible plate and a surrounding fluid. The velocities at the immersed boundary (IB) nodes are reconstructed by interpolations along local normal lines to an interface. A new criterion is suggested to distribute the IB nodes near an interface. The suggested criterion guarantees a closed fluid domain by a set of the IB nodes and it is applicable to a zero‐thickness body. To eliminate the pressure interpolation at the IB nodes, the hybrid staggered/non‐staggered grid method is adapted. The developed code is validated by comparisons with other experimental and computational results of flow around an in‐line oscillating cylinder. Good agreements are achieved for velocity profiles and vorticity and pressure contours. As applications to the fluid–structure interaction, oscillations of flexible plate in a resting fluid and flow over a flexible plate are simulated. The elastic deformations of the flexible plate are modelled based on the equations of motion for plates considering the fluid pressure as the external load on the plate. Two non‐dimensional parameters are identified and their effects on the damping of the plate motion are examined. Grid convergence tests are carried out for both cases. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
基于工程结构不确定性的区间分析方法,本文将区间分析方法与可靠性分析方法相结合,探讨了一种可以获得区问可靠指标的可靠性分析方法.依据结构失效准则确定的功能函数在一定区间内变化,进而得出了可靠指标的变化区间,在得到区间可靠指标的同时也得到了一种反映结构稳健性的稳健可靠指标.结合区间有限元的优化计算方法,对某地下隧道结构进行了区间可靠性分析,所得区间可靠性指标合乎规律.  相似文献   

15.
Parameters that affect the efficiency of a flat plate integrated collector storage solar water heater (ICSSWH) are examined experimentally and numerically. This specific ICSSWH contains water that is not refreshed. The service water is heated indirectly through an immersed heat exchanger (HE) in contact with the front and back major surfaces. A forced convection mechanism consisting of a pump that brings the storage water into motion by recirculation is used for heat transfer intensification. The two major (front and back) flat plate surfaces need to be well interconnected so that they are not deformed by the weight of the contained water and the exerted high-pressure. Two main factors that influence the performance are optimized: the position and size of the recirculation ports and the arrangement and size of the interconnecting fins. Both factors are explored to maximize the velocity flow field of the recirculated storage water. Consequently, the heat transfer rate between the two water circuits is maintained at high levels. Various 3D computational fluid dynamics (CFD) models are developed using the FLUENT package. An experimental model, made by Plexiglas, is used for the visualization of the flow field. Flow velocities are measured using a laser doppler velocimetry (LDV) system. The optimal arrangement increases the mean storage water velocity by 65% and raises the outlet temperatures up to 8 °C.  相似文献   

16.
Summary The problem of the generation of waves due to small rolling oscillations of a thin vertical plate partially immersed in uniform finite-depth water is investigated here by utilizing two mathematical methods assuming the linearised theory of water waves. In the first method, the use of eigenfunction expansion of the velocity potentials on the two sides of the plate produces the amplitude of wave motion at infinity in terms of an integral involving the unknown horizontal velocity across the gap, and also in terms of another integral involving the unknown difference of the potential across the plate. These unknown functions satisfy two integral equations. Any one of these, when solved numerically, can be used to compute the amplitude of the wave motion set up at either infinity on the two sides of the plate for various values of the wave number.In the second method, the problem is formulated in terms of a hypersingular integral equation involving the difference of the potential function across the plate. The hypersingular integral equation is solved numerically, and its numerical solution is used to compute the wave amplitude at infinity. The two methods produce almost the same numerical results. The results are illustrated graphically, and a comparison is made with the deep-water result. It is observed that the deep-water result effectively holds good if the plate is partially immersed to the order of one-tenth of the bottom depth.This work was initiated when the first Author was visiting Mathematics Department, Indian Institute of Science, Bangalore. It was partially supported by DST, and by CSIR. The authors take this opportunity to thank the Managing Editor for his suggestions to improve the paper in the present form.  相似文献   

17.
A steady laminar boundary layer flowing along a vertical plate immersed in a Darcy–Brinkman porous medium saturated with water at 4°C is studied. The plate temperature varies sinusoidally along the plate between 0 and 8°C where the density of water varies parabolically and is almost symmetrical at about 4°C. Except for the existence of the buoyancy force, it is assumed that either the plate moves upwards or the ambient water moves upwards (moving stream). The results are obtained with the direct numerical solution of the boundary layer equations taking into account the temperature dependence of water thermophysical properties (ρ, μ and c p). Results are presented for the wall temperature gradient and the wall shear stress along the plate for free convection and mixed convection. Temperature and velocity profiles are also presented.  相似文献   

18.
壁湍流扩展的自相似标度律的实验研究   总被引:6,自引:4,他引:2  
姜楠  王玉春 《实验力学》2002,17(1):28-34
对风洞中零压力梯度平板湍流边界层进行了实验研究,用热线风速仪测量了不同法向位置的脉动速度,研究了湍流边界层不同法向位置速度结构函数的扩展的自相似标度律。  相似文献   

19.
We present, a model to calculate sound transmission through plates perforated with periodically distributed subwavelength holes. Measurements performed using aluminium-perforated plates immersed in water are compared to predictions obtained with the calculation model. The calculated results agree well with experimental ones. It is also showed, both experimentally and numerically, that the number of the transmission peaks, related to the Fabry-Pérot resonances, depends on the plate thickness. Finally the existence of a transmission dip, when the water wavelength is equal to the array period, is a manifestation of the Wood anomaly.  相似文献   

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